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What is the FPC Connector

FPC connector, full name Flexible Printed Circuit Connector, is a kind of flexible zigzag printed circuit connector.

The composition of FPC connector

FPC connector (Flexible Printed Circuit Connector) is a precision electronic component. Its structure is designed to achieve a reliable electrical connection and mechanical fixing.

1.Composition of core components

1. Flexible contactor
   As the core component of the connector, the elastic contactor is usually made of highly elastic material such as a steel plate or phosphor bronze, to ensure stable electrical contact and long-lasting mechanical properties.
2. Snap mechanism
   The precise snap mechanism is designed to accurately locate and firmly fix the relative position between the FPC connector and the circuit board to prevent displacement or loosening during use.
3. Protective Shell
   The shell structure not only provides mechanical protection but also has the important function of fixing the internal components to ensure the overall structural integrity and reliability of the connector.

1.High-performance FPC connector enhancement components

1. Rubber core assembly
   Function: Provide terminal protection, electrical insulation, connectivity and enhance mechanical strength.
   Manufacturing process: precision injection molding
   Material: PA9T and other high-performance engineering plastics
2. Guide Tongue
   Function: Cable crimping, electrical insulation, connection positioning, and structural strengthening.
   Manufacturing process: high-precision injection molding
   Material: PA10T, PP,S and other high temperature resistant engineering plastics.
3. Conductive Terminal
   Function: Ensure efficient transmission of electronic signals
   Manufacturing Process: Precision stamping combined with electroplating (gold/tin plating).
   Material: Phosphor bronze and other highly conductive alloys
4. Soldering fixing piece
   Function: Precise positioning, mechanical fixing, and structural strength enhancement.
   Manufacturing process: stamping with electroplating treatment
   Material: bronze and other high-performance alloys
   This modular design allows FPC connectors to meet the stringent requirements of modern electronic products on high-density, high-reliability connections, while adapting to the needs of automated production. The careful selection of materials for each component and the precision manufacturing process ensure that the connector has excellent performance in terms of electrical performance, mechanical strength and long-term reliability.

FPC Connector Classification

FPC connectors can be categorized according to pitch, structure and usage to meet the needs of different application scenarios.

1.Classification according to pitch

The pitch of the FPC connector determines its integration degree and applicable scenarios. Mainstream specifications include:
0.3mm: ultra-high density connection for miniaturized devices (e.g. wearable devices, miniature sensors).
0.5mm: mainstream compact design, widely used in consumer electronics (e.g. smartphones, tablets).
0.8mm & 1.0mm: general-purpose pitch, suitable for devices with lower space requirements (e.g. industrial control, automotive electronics).
The smaller the pitch, the higher the integration, but also higher requirements for manufacturing precision and the assembly process.

2.Categorized by structure

Different structural designs to adapt to different connection needs, the main types include:
Top Contact:
The terminals are located above the socket, taking up little space, and are suitable for compact designs with height restrictions.
Bottom Contact:
Terminals are located below the receptacle for a more secure connection, suitable for vibration-resistant, high-reliability scenarios.
Flip-Lock:
Flip-locked FPCs can be easily inserted and removed by flipping the cover plate, and are often used in applications where FPCs need to be replaced frequently (e.g., test equipment).
Slider:
Adopting a slide locking mechanism, the connection is more solid, suitable for high vibration, high reliability requirements (such as automotive electronics, industrial equipment).

3.Classification by use

FPC connectors can be divided into different types according to the connection:
Board-to-Board (Board-to-Board):
Connection of two PCBs, suitable for multi-layer stacking design (such as modular electronic equipment).
Wire to board (Wire-to-Board):
Connecting cable and PCB, commonly used in power, signal transmission (such as display, camera module).
FPC to FPC:
Directly connecting two flexible circuits, suitable for foldable devices, flexible electronics (e.g., folding screen phones, flexible sensors).
This categorization helps engineers to choose the right type of FPC connector according to space constraints, connection stability, application scenarios, and other needs.

FPC connector product advantages

With its unique structural design and material properties, FPC connectors show excellent performance advantages in modern electronic equipment, mainly including the following aspects:

1.High flexibility

Adopting flexible circuit design, it can adapt to complex spatial layout and dynamic bending requirements, and is widely used in folding devices, wearable electronics, and other scenarios that require high shape adaptability.

2.Excellent electrical performance

Low impedance and low signal loss design ensures stable transmission of high-speed signals, suitable for high-frequency and high-precision electronic systems (e.g., 5G communication, high-definition display, etc.).

3.Ultra-thin and lightweight

Compact structure design, thickness can be as low as 0.3mm or less, significant space saving, especially suitable for portable electronic devices (such as smart phones, tablet PCs, drones, etc.).

4.Excellent environmental adaptability

With bending resistance (more than 100,000 times), high temperature resistance (up to 125 ° C), moisture and corrosion resistance, etc., to meet the needs of automotive electronics, industrial equipment and other harsh environments for long-term stable operation.
These advantages make FPC connectors an indispensable key component in modern electronic equipment, especially in the field of high-density integration, flexible electronics and miniaturized equipment has an irreplaceable role.

The role of FPC connectors

FPC connector as a key interconnect component in modern electronic systems, in equipment integration and performance optimization plays an irreplaceable role, its main functional value is reflected in the following aspects:

1.Efficient interconnection function

As a bridge between flexible circuit board (FPC) and PCB or other electronic modules, it simultaneously realizes the dual functions of mechanical fixation and electrical conduction, and supports a variety of connection modes (board-to-board, wire-to-board, FPC-to-FPC) to meet the interconnection needs of different application scenarios.

2.System reliability guarantee

The use of precision contact structure and high-quality conductive materials ensures long-term stability of the electrical connection performance, effectively avoids signal interruption or equipment failure due to poor contact,and significantly improves the service life of electronic products.

3.High-quality signal transmission

Support high-speed digital signals (such as HDMI, USB), high-frequency RF signals, and stable transmission of analog signals, low impedance, and low crosstalk design to ensure signal integrity, to meet the high-definition video, high-fidelity audio, and other demanding applications.

4.Space-optimized solutions

Ultra-thin design (minimum pitch up to 0.3mm) significantly improves space utilization, especially for smartphones, wearable devices ,and other extremely space-sensitive miniaturized electronic products.

5.Convenient maintenance characteristics

Modular design supports rapid insertion and removal, greatly simplifying the equipment assembly and maintenance process, with repeatable insertion and removal characteristics (usually supporting 5000-10000 times insertion and removal) to reduce maintenance costs and improve product repairability.
These core features make FPC connectors indispensable key components in modern electronic product design, especially in the pursuit of thin and light, high reliability, and easy maintenance, application scenarios show unique advantages. With the development of electronic equipment to a higher degree of integration, the importance of FPC connectors will be further highlighted.

FPC Connector Selection Key Parameters

To ensure the best performance of FPC connectors in the target application, engineers need to focus on the following key parameters:

1.Electrical performance parameters

Rated current: 0.5A ~ 3A (selected according to power requirements)
Voltage rating: 50V~300V (considering the system voltage margin)
Contact resistance: ≤30mΩ (low impedance design ensures signal integrity)
Insulation resistance: ≥100MΩ (typical value)

2.Mechanical Performance Parameters

Insertion and extraction force characteristics:
Insertion force: 5N~20N (balancing operational convenience and connection reliability)
Pull-out force: ≥2N (to ensure connection stability)
Terminal plating:
Gold plating thickness: 0.05~0.2μm (affects wear resistance and contact resistance)
Optional plating: tin plating, silver plating, etc.

3.Structure compatibility parameters

FPC compatibility range:
Thickness compatibility: 0.1 mm~0.3 mm (need to match the actual FPC specifications)
Insertion depth: such as 4.5mm ± 0.3 (affects the reliability of the connection)
Terminal spacing: 0.3mm/0.5mm/1.0mm, etc. (determines the connection density)

4.Environmental tolerance parameters

Mechanical environment:
Vibration resistance: 10Hz~500Hz/50m/s² (higher requirements for automotive applications)
Impact resistance: ≥50G (industrial grade standard)
Climatic environment:
Operating temperature: -40℃~+85℃ (Extended type can reach 125℃)
Protection grade: IP54 and above (dustproof and waterproof requirements)
Humidity and heat resistance: 85℃/85%RH (1000 hours test)

5.Life parameters

Mechanical life: ≥ 5000 times plugging and unplugging (high-quality products up to 10000 times)
Environmental aging life: ≥5 years (assessed according to application scenarios)
It is recommended to adopt the “parameter margin method” when selecting, i.e., to reserve 20%-30% of the design margin based on the measured parameters to cope with the variable factors in the actual application. For critical applications (e.g., automotive electronics, medical equipment), it is recommended to conduct a complete reliability verification test.

Application Scenarios

Mobile smart terminal field
Core applications: smartphones (folding screen models), tablets, TWS headphones, smartwatches
Typical connections: OLED/LCD module, multi-camera system, 3D sensing module, side button wiring
Technical Advantage: 0.3mm ultra-narrow pitch design adapts to the trend of full-screen, supports more than 200,000 times of bending life.
Automotive Electronic System
Key parts: intelligent cockpit display, ADAS sensor array, electronic gearshift mechanism, HUD projection module
Performance requirements: AEC-Q200 automotive certification, high temperature resistance of 125 ℃, anti-vibration 50Hz/30G
Development trend: applied to the domain controller high-speed interconnect, transmission rate up to 10Gbps +.
High-end medical equipment
Precision connections: endoscopic imaging modules, wearable monitoring patches, digital PCR detectors, surgical robot joints
Special requirements: biocompatible materials, support for autoclave sterilization, IP68 anti-liquid permeability
Industrial Automation Scenarios
Typical configuration: industrial robot joint harness, PLC control unit, intelligent sensor network, AGV navigation system
Environmental adaptation: anti-chemical corrosion plating, -40℃~85℃ wide temperature range, anti-electromagnetic interference design
Emerging Application Areas
Consumer electronics: AR/VR headset devices, flexible e-books, foldable smart terminals
Internet of Things: smart home control module, LoRa sensing node, 5G micro base station
Special fields: satellite communication equipment, UAV flight control system

Development trend

With the development of electronic equipment to higher performance, smaller volume, FPC connector technology is experiencing a revolutionary breakthrough, mainly showing the following four major trends:
1.Extreme miniaturization technology breakthroughs
Industry benchmark: Hirose FH28 series to achieve 0.2mm pitch mass production
Technical highlights:
Adoption of micron-level precision stamping process
Innovative suspended contact structure design
Support 15μm ultra-thin FPC connection
Application scenarios: foldable device pivot area, medical micro-implantable device
2.High-speed transmission technology evolution
Latest standard: supports 56 Gbps PAM4 signal transmission
Key Technology:
Precise control of differential pair impedance (100Ω±10%)
Low dielectric loss material application (Dk<3.0@10GHz)
Optimized crosstalk rejection design (<-40dB)
Typical applications: 400G optical modules, AI server backplane interconnects
3.Extreme environment reliability enhancement
Vehicle-grade standards:
Compliant with USCAR-2 vibration standards
1000 hours salt spray test (5% NaCl solution)
125°C continuous operating temperature
Innovative process:
Nano-coating technology (Au+Ni composite coating)
Laser welding encapsulation process
Silicone secondary injection molding sealing
4.Intelligent interconnection function integration
A new generation of smart connectors:
TE Connectivity M.2 connectors with integrated plug detection
Molex Develops FPC Connectors with Temperature Sensing
JAE Introduces Industrial Connectors with RFID Identification Features
Technology Integration:
Embedded Microcontrollers
Hybrid Fiber-Copper Transmission
Self-diagnostic fault warning system
Industry trends show that the next generation of FPC connectors will be developed in the direction of the “four super”: ultra-miniature (0.1mm pitch), ultra-high speed (112Gbps), ultra-reliable (2 million times plugged), ultra-intelligent (edge computing integration), these breakthroughs will promote the development of cutting-edge technology, such as 5G communications, automated driving, AI computing and so on.

What is PCBA

The full name of PCBA is Printed Circuit Board Assembly, i.e. Printed Circuit Board Assembly, which refers to the assembly of electronic components, connectors, plug-ins, digital logic gates, micro-control units, etc. onto a printed circuit board, and then a variety of processes such as soldering and plugging to make it a complete functional module of an electronic product.

What are the common components on the PCB

1.Passive components

1. Resistors (Resistor)
   Function: Limit the current size, voltage shunt
   Common types: carbon film resistors (economical and practical), metal film resistors (higher precision), wirewound resistors (high-power applications), chip resistors (SMD, modern mainstream)
   Identification techniques: color ring code: 4-6 color rings to indicate the resistance value and accuracy, chip code: 3-4 digits to indicate the resistance value
   Circuit Symbol: Rectangular box or wavy line
2. Capacitor (Capacitor)
   Function: energy storage, filtering, coupling
   Mainstream types: electrolytic capacitors (large capacity, polarity), ceramic capacitors (good high frequency characteristics), tantalum capacitors (small size, high stability), film capacitors (high precision)
   Circuit marking: “C” beginning (such as C1, C2)
   Selection points: capacitance value, withstand voltage value, temperature coefficient
3. Inductor (Inductor)
   Function: filtering, energy storage, current stabilization
   Main categories: hollow inductors (high-frequency applications), ferrite inductors (anti-interference), chip inductors (space-saving), power inductors (high-current)
   Circuit marking: “L” beginning (such as L1, L2)

2.Semiconductor devices

1. Diode (Diode)
   Function: unidirectional conductivity, voltage stabilization, light-emitting
   Common types: rectifier diodes (such as 1N4007), voltage regulator diodes (such as 1N4742), Schottky diode (low drop), LED (light-emitting diode), TVS diodes (anti-static)
   Circuit marking: “D” beginning
2. Transistor (Transistor)
   Function: signal amplification, switching control
   Main types: transistor (BJT), field effect tube (MOSFET), IGBT (high-power switch)
   Package: TO-92 (low power), TO-220 (medium power), SOT-23 (SMD)

3.Integrated Circuits

1. Analog IC
   Operational amplifiers, voltage regulators, data converters (ADC/DAC)
2. Digital ICs
   Microcontroller (MCU)
   Memory (Flash, RAM), logic gate circuits
3. Mixed-signal ICs
   Wireless transceiver chips, sensor interface ICs

4.Other Important Components

1. Connectors
   Pin header/female connector, USB/HDMI interface, board-to-board connector
2. Protection components
   Fuses, varistors, gas discharge tubes
3. Electromechanical components
   Relay, switch, buzzer

What certifications are required for components

Specific certification requirements for different types of components
Integrated circuits: ISO/IEC 27001 Information Security Management System certification is required to ensure that the design and manufacture comply with the relevant standards.
Capacitors and resistors: RoHS certification is required to ensure that they do not contain hazardous substances.
Connectors: UL certification or other electrical safety certification is required to ensure safety during use.
LED components: Safety and performance certifications are required to ensure compliance in lighting and display applications.
Semiconductor devices: need to be AEC-Q100 certified for use in automotive electronics.
Sensors: industry-specific certifications may be required, such as ISO 13485 for medical electronics
These certifications not only ensure the quality and safety of the product, but also help the product to be compliant in the marketplace.

The role of common components on the PCB

1.Resistor (Resistor)
Core functions: current limiting, voltage distribution, signal regulation
Typical applications: provide the appropriate bias voltage for the transistor, in the sensor circuit to adjust the signal level, as a current-limiting LED protection components
2.Capacitor
Core functions: energy storage, noise filtering, signal coupling
Typical applications: power supply circuit filtering (to eliminate ripple), signal coupling in audio circuits, digital IC power pin decoupling
3.Inductor
Core functions: energy storage, high-frequency filtering, current stabilization
Typical applications: switching power supply energy conversion, impedance matching in RF circuits, the key components of EMI filters
4.Diode (Diode)
Core functions: one-way conductivity, voltage regulation, circuit protection
Typical applications: AC to DC rectifier circuit, over-voltage protection TVS diode, to prevent the power reverse protection circuit
5.Transistor (Transistor)
Core functions: signal amplification, electronic switching, current control
Typical applications: audio signal amplification, digital logic circuits, motor drive control
6.Integrated Circuit (IC)
Core functions: realization of complex electronic functions
Typical applications: microcontrollers (system control core), operational amplifiers (signal processing), power management ICs
7.Electromechanical components
Switches: circuit on/off control
Connectors: electrical connection between modules
Relay: small current to control large current
Indication and alarm components
LED: visual indication of working status
Buzzer: audible alarm indication
8.Protection Components
Fuse: overcurrent protection
Varistor: Surge protection
Gas discharge tube: lightning protection
9.Sensor Components
Temperature sensor: environmental monitoring
Photoresistor: Light intensity detection
Accelerometer: Motion sensing

How to quickly identify PCB components

Look at the marking: letters + numbers next to the component numbering
Look at the package: different components have a typical package form
Measurement parameters: using a multimeter to measure the basic characteristics of the
Check the information: according to the model query specifications

PCB on the common component symbols

PCB on the common component symbols include resistance (R), capacitance (C), inductance (L), integrated circuits (IC), diodes (D), transistors (Q), transformers (T) and so on.

Character Circuit Diagram Symbols

1.Basic electrical symbols

1. Power supply category
   AC: alternating current symbol (wavy line)
   DC: direct current symbol (straight line + dotted line)
   G: generator symbol (circle with G)
2. Protective devices
   FU: Fuse (rectangular center break)
   FF: Falling fuse (rectangle with slash)
   FV: Voltage limiting protection device (rectangle with arrow)

2.Control device symbols

1. Switch category
   QS: Disconnecting switch (slash disconnect)
   QF: Circuit breaker (with trip symbol)
   SB: Push-button switch (half-circle connection)
2. Relays
   KA: Instantaneous relay (with lightning in the box)
   KT: Time relay (with clock in the box)
   KH: Thermal relay (with wavy lines in the box)

3.Measuring Instrument Symbols

1. Basic meter
   PA: ammeter (A in circle)
   PV: Voltmeter (V in circle)
   PPF: Power factor meter (cosφ in circle)
2. Electricity measurement
   PJ: Active meter (Wh in circle)
   PJR: reactive power meter (VARh in circle)

4.Motor and actuator

1. Electric motor
   M: General symbol for electric motor (M in circle)
   MS: Synchronous motor (double circle)
   MA: Asynchronous motor (with slash in circle)
2. Actuator
   YV: Solenoid valve (rectangle with wavy line)
   YM: Motorized valve (rectangle with gear)
   YE: electric actuator (rectangle with arrow)

5.Signal indicating device

1. Indicator light
   HR: red light (solid circle with H)
   HG: green light (solid circle with G)
   HY: Yellow light (solid circle with Y)
2. Signaling device
   HA: Acoustic signal (horn symbol)
   HS: Light signal (lightning symbol)
   HP: Light sign (rectangle with text inside)

6.Special Component Symbols

1. Sensor type
   BL: Liquid level sensor (trapezoidal with wavy lines)
   BT: Temperature sensor (rectangle with thermometer)
   BV: speed sensor (rectangle with tachometer)
2. Power electronics
   UR: Thyristor rectifier (triangular with gate)
   UI: Inverter (rectangle with bidirectional arrow)
   UF: Inverter (rectangle with frequency symbol)

7.Wiring and connecting devices

1. Connection devices
   XT: Terminal block (circular arrangement of points)
   XB: Connection tabs (rectangular connecting wires)
   XP/XS: plug socket (concave butt symbol)
2. Busbar system
   W: DC busbar (thick solid wire)
   WV: voltage mini-busbar (dotted line)
   WCL: closing small busbar (with switch symbol)
   Mastering these symbols is the basis for understanding circuit schematics, and with experience, you will be able to quickly interpret a variety of complex electrical drawings.

PCB component layout and wiring design

1.Basic principles of component layout

1. Strategic Priority Layout
   First arrange the core IC and large components (such as processors, FPGA)
   Then arrange key peripheral circuits (clock circuits, power modules)
   Finally arrange small passive components (resistors, capacitors, etc.)
2. Signal flow optimization layout
   According to the schematic signal flow direction (input → processing → output) sequence layout
   Critical signal paths are minimized (especially for high-speed signals)
   Sensitive signals away from interference sources (e.g. switching power supply)
3. Symmetry aesthetics and functional balance
   Mirror symmetry layout for the same functional modules
   Uniform distribution of components on the board (to avoid weight skew)
   Balanced heat dissipation and electromagnetic compatibility.

2.Professional layout details

1. Functional modular layout
   Strict partitioning of digital/analog circuits (recommended spacing >5mm)
   Separate isolation for RF circuits
   Centralized arrangement of power supply modules
2. Safety spacing specification
   Components from the board edge ≥ 5mm (to prevent processing damage)
   Between the chip components ≥ 2mm (easy to repair)
   Between high-voltage components ≥ 8mm (safety requirements)
3. Special component processing
   Heat generating components:
   Uniform distribution to avoid hot spot concentration
   Keep away from heat-sensitive components (such as electrolytic capacitors)
   Add heat sinks if necessary
   High frequency components:
   As close to the center of the board as possible
   Keep away from I/O ports
   Use ground shield protection
4. Decoupling capacitor arrangement
   0.1μF capacitor on each power pin
   Layout distance <3mm (ideally mounted on the backside)
   When multiple capacitors are connected in parallel, they are arranged from smallest to largest capacity.

3.Intelligent wiring strategy

1. Prioritize key signals
   Clock signals:
   Thicker line width (usually 8-12 mil)
   Full accompanying ground
   Avoid right-angle turns
   Differential signals:
   Strictly equal length (error <50 mil)
   Parallel alignment
   Impedance matching
2. High-density wiring techniques
   Start from BGA and other complex devices
   Route through the densest areas first
   Use 45° diagonal transition
3. Layered routing scheme
   Layer stacking is recommended:
   Top layer: critical signals
   Inner layer 1: complete ground plane
   Inner layer 2: Power plane
   Bottom Layer: Common Signals
   High Frequency Signal Recommendation:
   Ribbon line alignment (inner layer)
   Avoid Cross-Split Zones

How to do PCBA fabrication

PCBA fabrication is a complex and delicate process that requires specialized knowledge and equipment. The following are the general steps for PCBA production:
1.circuit design: according to the functional requirements of electronic products, design circuit diagrams, and use professional EDA software, such as Altium Designer, etc., circuit board design.
2.printed circuit board manufacturing: the design of the circuit diagram printed production into a solid circuit board, which usually needs to be through photolithography, etching, drilling and other steps.
3.component procurement: according to the circuit design, procurement of the appropriate electronic components, including resistors, capacitors, inductors, diodes, transistors, integrated circuits and so on.
44component assembly: the procurement of components in accordance with the circuit design requirements placed on the printed circuit board, which usually need to be carried out through the mounter and other specialized equipment.
5.welding: components and printed circuit board welding, including wave soldering, reflow soldering and other methods.
6.Testing: Test the completed PCBA, including visual inspection, electrical testing, functional testing, etc., to ensure that its function is correct and free of defects.
7.Packaging：Packaging and labeling of the tested PCBA, including anti-static packaging, moisture-proof packaging, etc., to ensure its safety in the transportation and use of the process.

PCBA Application Areas

PCBA technology has been deeply integrated into various fields of modern society:
Consumer electronics: the miniaturized core of smartphones and tablets
Automotive industry: the nerve center of electrification and intelligent driving
Medical equipment: the lifeline of high-precision diagnostic instruments
Industry 4.0: the control core of intelligent manufacturing systems
Aerospace industry: the technological cornerstone of highly reliable equipment

Future Development Trends

1.Heterogeneous integration technology
2.5D/3D packaging breaks through the plane limitation
Silicon photonics integration to enhance transmission bandwidth
2.Green Manufacturing Transformation
Lead-free process popularization
Recyclable Material Application
3.Digital Twin Application
Virtual Prototyping Accelerates Development
Intelligent Predictive Maintenance

In the PCBA design and manufacturing process, the correct selection and rational use of electronic components is crucial. Designers need to select the appropriate types and specifications of electronic components based on the functional requirements of the circuit, performance requirements and cost considerations. At the same time, it is also necessary to consider the layout of components, soldering process and reliability to ensure that the quality and performance of the circuit board meets the expected requirements.

12V SPDT PCB mounted 2A ultra-miniature relays have become a critical control element in today’s compact electronic equipment, with their superior miniaturized design ensuring high performance while achieving revolutionary space savings. Typically more than 50% smaller than conventional relays, these ultra-miniature relays are used in a wide range of high-density electronic systems because they maintain excellent electrical performance and mechanical reliability.

Product Benefits

1.Extreme space utilization (typical size is only 10 x 6 x 5mm)
2.Excellent electrical characteristics (contact resistance ≤ 100mΩ, insulation resistance ≥ 100MΩ)
3.Wide compatibility (12VDC±10% operating voltage range)
4.Reliable load capacity (2A/250VAC or 30VDC)

Product Category

1.Classification according to contact material

Silver alloy contacts: good conductivity, strong arc resistance
Gold contacts: low contact resistance, suitable for small signal switching.

2.Classification according to coil characteristics

Standard type: conventional power consumption design
Low power consumption type: energy-saving design, reducing the overall energy consumption of the system.
High sensitivity type: can work reliably under lower voltage.

3. Classified by package form

Fully sealed: dust and moisture resistant, suitable for harsh environments.
Semi-sealed: basic protection, low cost
Open type: good heat dissipation, suitable for conventional environment.

4. Classified by special function

With LED indication type: can visualize the working status.
With diode protection type: built-in diode to protect the driving circuit.
With surge suppression: to reduce the electromagnetic interference of the switching moment.

The Role of Relays

In modern electronic systems, the 12V SPDT ultra-miniature relay plays multiple critical roles due to its compact design and superior performance:

1.Electrical isolation barrier

As a safety barrier between the control circuit and the load circuit, complete electrical isolation is achieved. This isolation feature effectively protects the low-voltage control terminal from interference and damage from the high-voltage load terminal, ensuring safe and stable operation of the system.

2.Highly Reliable Signal Routing

In precision test instruments and communication equipment, the relay serves as a highly reliable electronic switch to ensure the precise switching of signal paths. Its ultra-miniature design is particularly suitable for high-density signal routing applications, while maintaining excellent signal integrity.

3.Compact Power Control

Despite its compact size, its 2A current carrying capacity makes it an ideal control element for small and medium power devices such as LED lighting arrays, micro motors and compact solenoid valves, perfectly balancing space constraints with power requirements.

4.Intelligent State Switching

SPDT single-pole, double-throw structure gives it unique bidirectional control capability, a single relay can realize: automatic switching of circuit state, alternate selection of dual-channel signals, and conversion of equipment operating modes.

5.Basic Logic Construction

Through the clever combination of relays, basic logic circuits such as AND, OR, etc. can be constructed to provide cost-effective solutions for simple automation systems, especially suitable for application scenarios that do not require complex programmable controllers.

6.System Safety Guard

The built-in quick cut-off mechanism makes it an effective circuit protection device, which can quickly cut off the connection when abnormal conditions are detected, and can effectively prevent, equipment overload damage, circuit short-circuit accidents, and system failures from expanding.

Working Principle

1.Electromagnetic drive system

When 12V DC voltage is loaded to the relay coil, the precision designed miniature electromagnetic system responds immediately:
The miniature coil made of high permeability alloy material generates a strong electromagnetic field.
Optimized winding process ensures maximum electromagnetic efficiency in limited space.
The electromagnetic suction force generated is precisely applied to the special alloy armature mechanism.

2.Precision Mechanical Transmission

The mechanical transmission system of the ultra-miniature relay embodies the essence of micromechanical engineering:
Adopting aerospace-grade precision spring system, the response time is <3ms.
Unique design of lever amplification mechanism increases the efficiency of electromagnetic force by 40%.
Super wear-resistant bearing structure ensures 10 million times mechanical life.

3.High performance contact system

SPDT contact set adopts innovative design:
Sandwich composite contact material (AgSnO2+Au plating)
Reed mechanism with special elastic design
Self-cleaning contact structure design
Contact pressure >50g to ensure low contact resistance

4.Co-operative workflow

Stationary state
High precision spring maintains NC contact closed
COM terminal and NC terminal maintain conduction
Static contact resistance <50mΩ
Excitation state (12V energized)
Electromagnetic force overcomes spring force within 5ms
Armature mechanism pushes contact switching
COM terminal establishes connection with NO terminal
Switching time <10ms
Reset process
Spring force resets the mechanism after power failure
Mechanical rebound time <8ms
Complete restoration of the initial contact state

With innovative magnetic circuit design, precise mechanical structure and advanced contact technology, this miniature relay realizes better performance in 1/3 of the volume of traditional relays, which is especially suitable for application scenarios with stringent space requirements, such as 5G devices and IoT terminals. The perfect synergy of all systems during its working process ensures reliable operation in -40℃~85℃ environment.

Specification

Core Electrical Characteristics

• Coil Parameters
• Rated voltage: 12VDC (±10% tolerance)
• Power consumption: 0.2W-0.5W (including energy-saving and standard types)
• Pick-up voltage: ≤9.6VDC (ensures reliable actuation)
• Drop-out voltage: ≥1.2VDC (guarantees complete reset)
• Contact Performance
• Contact resistance: Initial ≤50mΩ (≤100mΩ after 1 million operations)
• Dielectric strength: 1500VAC/1min between coil and contacts
• Insulation resistance: ≥1000MΩ (tested at 500VDC)

Load Capacity Parameters

Mechanical Specifications

• Dimensions
• Ultra-compact design: 10.0mm(L)×6.0mm(W)×5.0mm(H)
• Mounting: Supports both THT and SMD (optional)
• Pin configuration: Standard 2.54mm pitch (1.27mm high-density option available)
• Environmental Durability
• Operating temperature: -40℃～+85℃ (industrial grade)
• Storage temperature: -55℃～+105℃
• Protection rating: IP40 (standard)/IP67 (optional sealed version)
• Vibration resistance: Complies with IEC 60068-2-6
• Shock resistance: 100m/s² (meets MIL-STD-202G)

Reliability Indicators

• Mechanical Life
• Standard: ≥10 million operations (no load)
• Enhanced: ≥20 million operations (special mechanical design)
• Electrical Life
• Resistive load: ≥100,000 operations (at rated 2A)
• Inductive load: ≥50,000 operations (L/R=10ms)
• Low-level load: ≥500,000 operations (100mA@5VDC)

Representative Model Comparison

Note: All parameters measured at 25℃ ambient temperature. Derating recommended for actual operating conditions. Custom solutions available for special applications.

Diversified application scenarios of 12V SPDT PCB mounted 2A ultra-miniature relay

1.Communication infrastructure field

Ultra-miniature relays are widely used in 5G base station equipment, fiber optic network switches and programmable telephone systems, responsible for the precise routing of critical signals and interface switching. Their high reliability ensures the uninterrupted operation of communication networks 24/7, while the miniaturized design is perfectly adapted to the demand for high-density integration of modern communication equipment.

2.Consumer electronics field

From the temperature control system in smart home, security equipment to the program control of all kinds of home appliances, the load capacity of 2A enables it to directly drive the actuators in most household appliances. It is especially worth mentioning that in the IoT terminal equipment, the low-power characteristics of this relay and the wireless module are perfectly matched to realize the organic combination of remote control and local execution.

3.Industrial Automation

As the standard configuration of PLC output modules, they are responsible for converting control signals into device actions; in sensor networks, they assume signal conditioning and isolation and amplification functions. Even in harsh industrial environments, their operating temperature range of -40°C to +85°C ensures stable operation.
Automotive Electronics
From mode switching of in-vehicle infotainment systems, to control of comfort functions such as seats and mirrors, to signal processing of OBD diagnostic interfaces, they can be found everywhere. Products that meet automotive-grade vibration and temperature standards are also ideal for battery management systems in electric vehicles.

4.Medical electronics

These relays are widely used in portable monitors, diagnostic equipment and low-power therapeutic instruments due to their stable performance and ultra-small size. Fully sealed models can better meet the special needs of medical equipment sterilization.

5.Test and Measurement Instruments

Automatic Test Equipment (ATE) uses them to realize intelligent switching of multi-channel signals, while precision measuring instruments rely on them to complete the automatic conversion of ranges. High-precision contact performance ensures the accuracy of the measurement results, and fast response characteristics improve the testing efficiency.

6.New energy and power electronics field

Micro relays are used in solar energy controllers for charge/discharge management, in micro inverters for circuit topology switching, and in energy monitoring equipment for sampling control. Its excellent insulation can provide a reliable guarantee for system safety.

Summary:The 12V DC operating voltage design enables it to be perfectly adapted to most modern low-voltage control systems, while the 2A current carrying capacity provides a reliable switching solution for various types of small and medium power loads. In particular, its precise PCB mounting design not only simplifies the production assembly process, but also significantly improves the efficiency of automated production, becoming an indispensable standard component in modern electronics manufacturing.

PCB SBU Industry Insight

Strategic Position & Market Value

As the “central nervous system” of electronics, printed circuit boards (PCBs) hold irreplaceable importance in modern manufacturing. According to Prismark, the global PCB market exceeded $80 billion in 2023, with a steady CAGR of 5.8%. Driven by 5G, AIoT, and electric vehicles, PCB Strategic Business Units (SBUs) are evolving from passive components into strategic innovation drivers.

PCB SBU Core Value

1.Supply Chain Nexus

Upstream: Specialized materials (high-frequency PTFE, ABF substrates for IC packaging)
Downstream: Six key sectors—consumer electronics (32%), telecom (28%), automotive (18%), medical (11%), industrial (8%), and aerospace (3%)

2.End-to-End Solutions

Co-design: Signal integrity optimization (<0.1dB loss via SI/PI simulation)
Smart manufacturing: mSAP process enabling 20/20μm line/space precision
Supply chain efficiency: Panel-level production (18×24 in standard) boosts material utilization to 93%

3.Production Optimization

Technology Breakthroughs

1.Advanced PCB Technologies

HDI: Stacked microvias for 16-layer interconnects
Flexible circuits: 3D-MID for wearable medical devices
High-frequency materials: Ceramic composites with Dk <3.0 / Df <0.002

2.Industry 4.0 Transformation

AI-powered AOI achieves 99.98% defect detection
Digital twin slashes NPI cycles to 72 hours
Hydrogen-based curing cuts energy use by 35%

Competitive Strategy & Future Roadmap

Key Challenges

Dual-supply chain for copper foil/resin (geopolitical resilience)
Bio-degradable substrates for EU RoHS 3.0 compliance

Growth Engines

Southeast Asia hub: Vietnam facility for automotive PCB localization
Heterogeneous integration: 2.5D/3D substrates with 5μm line width

Topfast’s Competitive Edge

As an IATF 16949-certified leader, we deliver three pillars of excellence

1. Technology Leadership

Capable of mass production of SLP 10μm lines.
Semiconductor test boards (±25μm tolerance)

2.Operational Reliability

24-hour prototyping (vs. industry-standard 72 hours)
99.2% on-time delivery for high-volume orders

3. Ecosystem Partnerships

DFM analysis + testing integration
Lifetime traceability with client-dedicated tech archives

Our “Concept-to-Production” approach powers mission-critical applications, from SpaceX Starlink terminals to Da Vinci surgical robots. With 8.7% R&D investment, we lead in materials science and precision engineering.

The Next Frontier

As silicon photonics and terahertz communications emerge, Topfast is pioneering:
Optical PCBs: Co-packaged photonic components
Nanocellulose substrates: 60% lower carbon footprint
Quantum interconnects: Cryogenic superconducting bonding
By fusing craftsmanship with digital intelligence, we’re redefining connectivity standards. Partner with Topfast to build the future of electronics.

The 2025 Russia International Consumer Electronics Fair (ICEF 2025), held from April 15–17 at Moscow’s Crocus Expo IEC, solidified its position as the largest and most influential tech trade show in the Russian-speaking world. With 50,000+ professional attendees, 30,000+ sqm exhibition space, and participants from 30+ countries, the event showcased cutting-edge innovations across the electronics ecosystem. Topfast was honored to participate as a key exhibitor (Booth B1143 & B1147), engaging with global partners and industry leaders.

17 Years of Excellence in PCB Solutions

Since its founding in 2008, Topfast has grown into a 1,000+ employee, 20,000 sqm manufacturing powerhouse, delivering end-to-end PCB solutions for Fortune 500 clients like Huawei, DJI, Mitsubishi, and Thales Group. Specializing in rapid prototyping and small-batch production, we combine precision engineering with agile delivery to meet the demands of IoT, aerospace, and next-gen consumer electronics.

Innovation-Driven Product Portfolio

Our certified offerings include:
High-Density Interconnect (HDI) Boards
Heavy Copper & Backplane Solutions
High-Frequency/RF & High-Speed PCBs
Flex-Rigid Hybrid Circuits
Semiconductor Test Boards
All products comply with IPC Class 3 standards, backed by UL, RoHS, and ISO9001 certifications, and serve mission-critical applications in 5G infrastructure, medical devices, industrial automation, and EV systems.

Why Global Leaders Choose Topfast

Elite Team: 20+ years’ average industry expertise
Advanced Manufacturing: Continuous investment in automation and R&D
Full-Spectrum Support: From design consultation to post-production testing
Speed-to-Market: 72-hour prototyping with 99.2% on-time delivery
At ICEF 2025, we strengthened ties with existing partners and forged new collaborations across Eastern Europe. Moving forward, Topfast remains committed to redefining PCB excellence through quality-first innovation and customer-centric agility.
Let’s Build the Future Together
Contact us to explore how our solutions can power your next breakthrough.

The 8-layer PCB laminated structure usually includes signal layer, power layer and ground layer, the specific arrangement and design principles are as follows

Signal layer: It usually includes the top layer (TOP), the bottom layer (Bottom) and the signal layer in the middle (e.g. Signal2, Signal3, etc.). The signal layer is mainly used for wiring and transmitting electrical signals.

Power Layer: It usually includes one or more power layers (e.g. Power1, Power2, etc.), which are used to provide a stable power supply. The power supply layer is adjacent to the ground layer to better realize the coupling between the power supply and the ground, and to reduce the impedance between the power plane and the ground plane.

Ground layer: includes one or more ground layers (e.g. Ground1, Ground2, etc.), which are mainly used to provide a stable ground reference plane and reduce electromagnetic interference. The ground plane is adjacent to the power plane to provide better signal integrity.

Design Principles and Common Arrangements

The layer adjacent to the main chip is the ground plane: it provides a stable reference plane for the main chip and reduces interference.
All signal layers are adjacent to the ground plane as much as possible: provides better signal integrity.
Avoid two signal layers directly adjacent to each other as much as possible: reduce signal interference.
Main power supply is adjacent to its corresponding ground plane as much as possible: to reduce the impedance between the power plane and the ground plane.
Symmetrical structure design: Dielectric layer thickness and type, copper foil thickness, and graphic distribution type should be symmetrical to minimize the impact of asymmetry.

Common design examples and tool usage

Common stacked layer design: such as TOP-Gnd-Signal-Power-Gnd-Signal-Gnd-Bottom, etc. This design can provide better signal integrity and electromagnetic compatibility.
Using Huaqiu DFM tool: This tool helps to calculate impedance, select proper line width and spacing, and ensure the accuracy of the design.

8-Layer PCB Stackup Design Analysis

Option 1: Six Signal Layer Design (Not Recommended)

Structure Characteristics:

1. Top Layer: Signal 1 (Component side/Microstrip routing layer)
2. Inner Layer: Signal 2 (X-direction microstrip, premium routing layer)
3. Inner Layer: Ground (Ground plane)
4. Inner Layer: Signal 3 (Y-direction stripline, premium routing layer)
5. Inner Layer: Signal 4 (Stripline routing layer)
6. Inner Layer: Power (Power plane)
7. Inner Layer: Signal 5 (Microstrip routing layer)
8. Bottom Layer: Signal 6 (Microstrip routing layer)

Drawback Analysis:

• Poor electromagnetic absorption
• High power impedance
• Incomplete signal return paths
• Inferior EMI performance

Option 2: Four Signal Layer Design (Recommended)

Improved Features:

1. Top Layer: Signal 1 (Component side/Microstrip, premium routing layer)
2. Inner Layer: Ground (Low-impedance ground plane, excellent EM absorption)
3. Inner Layer: Signal 2 (Stripline, premium routing layer)
4. Inner Layer: Power (Power plane forming capacitive coupling with adjacent ground)
5. Inner Layer: Ground (Ground plane)
6. Inner Layer: Signal 3 (Stripline, premium routing layer)
7. Inner Layer: Power (Power plane)
8. Bottom Layer: Signal 4 (Microstrip, premium routing layer)

Advantages:
✓ Dedicated reference plane for each signal layer
✓ Precise impedance control (±10%)
✓ Reduced crosstalk (orthogonal routing between adjacent layers)
✓ 40% improvement in power integrity

Option 3: Optimal Four Signal Layer Design (Highly Recommended)

Golden Rule Structure:

1. Top Layer: Signal 1 (Component side/Microstrip)
2. Inner Layer: Ground (Solid ground plane)
3. Inner Layer: Signal 2 (Stripline)
4. Inner Layer: Power (Power plane)
5. Inner Layer: Ground (Core ground plane)
6. Inner Layer: Signal 3 (Stripline)
7. Inner Layer: Ground (Shielding ground plane)
8. Bottom Layer: Signal 4 (Microstrip)

Outstanding Performance:
★ Five ground planes provide perfect EM shielding
★ <3mil power-ground spacing for optimal decoupling
★ Symmetrical layer distribution prevents warpage
★ Supports 20Gbps high-speed signaling

Design Recommendations:

1. Route critical signals on S2/S3 stripline layers first
2. Implement split power plane design
3. Limit top/bottom layer traces to <5mm length
4. Maintain orthogonal routing between adjacent signal layers

Stackup Thickness Reference

Note: All designs should incorporate blind/buried vias for optimal routing space utilization.

Classification and Applications of Printed Circuit Boards (PCBs)

Printed circuit boards (PCBs), as the core components of electronic devices, can be systematically classified based on different characteristics and application scenarios as follows:

Classification by Conductive Layer Count

1. Single-Sided PCB
   The most basic type of PCB, featuring a single copper layer with components mounted on one side and conductive traces on the other. It is simple in structure and low-cost, primarily used in early electronics and simple circuit designs.
2. Double-Sided PCB
   Utilizes copper layers on both sides, with electrical connections between layers achieved through plated through-holes (PTHs). Compared to single-sided PCBs, they offer higher wiring density and design flexibility, making them the most widely used PCB type today.
3. Multilayer PCB
   Consists of three or more conductive layers, bonded together with insulating dielectric materials and interconnected through vias. Multilayer PCBs enable complex circuit designs, meeting the high integration demands of modern electronics.

Classification by Substrate Material

• Rigid PCB
  Manufactured using inflexible, sturdy base materials, including:

• FR-4 (fiberglass epoxy)
• Paper-based substrates
• Composite substrates
• Ceramic substrates
• Metal-core substrates
• Thermoplastic substrates
  Widely used in computers, communication equipment, industrial controls, and more.

• Flexible PCB
  Made with bendable insulating substrates, allowing for folding, rolling, and bending. Ideal for portable electronics such as smartphones and tablets.
• Rigid-Flex PCB
  Combines rigid and flexible sections, providing structural support while allowing bending, making them suitable for 3D assembly applications.

Specialized Functional PCBs

• Metal-Core PCB (MCPCB)
  Composed of a metal base, insulating layer, and circuit layer, offering superior heat dissipation. Mainly used in high-heat applications like LED displays/lighting and automotive electronics.
• Heavy Copper PCB (≥3 oz copper thickness)
  Features:

• High current/voltage handling
• Excellent thermal performance
• Demanding manufacturing processes
  Applications: Industrial power supplies, medical equipment, military electronics, etc.

• High-Frequency PCB
  Characteristics:

• Low dielectric constant materials
• Strict signal integrity requirements
• High-precision fabrication
  Applications: Communication base stations, satellite systems, radar, etc.

• High-Speed PCB
  Features:

• Low-loss dielectric materials
• Precise impedance control
• Minimal insertion loss
  Applications: Networking equipment, servers, data storage systems, etc.

Advanced Multilayer PCB Technologies

• HDI (High-Density Interconnect) PCB
  Technical Features:

• Microvia technology (laser drilling)
• Sequential lamination
• Ultra-high wiring density
  Applications: Smartphones, automotive electronics, aerospace, etc.

• IC Substrate PCB
  Functional Features:

• Direct chip mounting
• High pin-count design
• Miniaturized packaging
  Applications: Memory chips, processors, sensors, and other semiconductor devices.

With advancements in electronics, PCBs continue to evolve toward higher layer counts, greater precision, and increased density. Emerging PCB technologies are driving innovation in electronic product development.

As climate change concerns grow and regulations tighten, the PCB industry is undergoing a green transformation. No longer just a trend—sustainable manufacturing has become a competitive necessity. With consumers, governments, and corporations demanding cleaner electronics, PCB manufacturers must adapt or risk falling behind.

Why Sustainability is Now a PCB Industry Imperative

1. Stricter Environmental Regulations

Governments worldwide are enforcing tougher e-waste and chemical regulations, including:
EU RoHS & REACH – Restricting hazardous substances
China’s Dual Carbon Policy – Mandating emissions cuts
U.S. EPA guidelines – Tightening wastewater & air pollution controls
Non-compliance risks fines, reputational damage, and lost business.

2. Rising Customer Demand for Green Electronics

75% of OEMs now prioritize eco-certified PCB suppliers (IPC Market Research, 2024)
Carbon-neutral pledges from Apple, Samsung, and Tesla are pushing supply chains to go green
Consumers pay up to 15% more for sustainably made electronics (Nielsen Survey, 2025)

3. Cost Savings & Long-Term Profitability

While “going green” requires investment, it lowers long-term costs:
Energy-efficient factories cut power bills by 20-30%
Waste recycling systems recover 90%+ of materials, reducing raw material costs
AI-driven optimization minimizes scrap rates, boosting yield

Key Innovations Driving Sustainable PCB Manufacturing

1. Eco-Friendly Materials

Halogen-free laminates – Reduce toxicity without sacrificing performance
Biodegradable substrates – Emerging R&D in plant-based PCB materials
Lead-free & low-chemical solders – Safer for workers and end-users

2. Energy & Water Efficiency Upgrades

Solar-powered PCB factories (e.g., AT&S’s renewable energy plants)
Closed-loop water systems – Recycle 40-50% of wastewater
Heat recovery systems – Repurpose excess heat from production

3. Smart Manufacturing & AI

AI defect detection – Reduces material waste by 15-20%
Predictive maintenance – Extends equipment life, lowering carbon footprint
Blockchain carbon tracking – Ensures transparency in sustainability claims

4. Circular Economy Practices

PCB refurbishment programs – Extend product lifecycles
Copper & gold recovery – 95%+ metal recycling rates
Take-back initiatives – Partnering with clients to recycle end-of-life boards

The Future is Green

$200B+ sustainable PCB market by 2030 (CAGR 18%)
IPC-1401 certification becoming the new industry benchmark
Carbon tariffs may penalize non-sustainable imports
Early adopters are already gaining:
New contracts with eco-conscious brands
Higher profit margins from efficiency gains
Stronger investor & customer trust

Conclusion:
Sustainability = Survival & Success. The PCB industry’s shift toward green manufacturing isn’t just about compliance—it’s a strategic advantage. Companies investing in clean tech, circular practices, and transparent reporting will lead the next era of electronics.

Founded in 2008, Topfast is a leading manufacturer of circuit board design, manufacturing and assembly, a one-stop PCB solution provider specializing in rapid prototyping and low-volume manufacturing customers. In response to the country’s international call for sustainable economic development with low energy and water consumption and low pollution, Topfast is rapidly realizing new technologies as an environmentally friendly science and technology enterprise, contributing to the global environmental protection cause.

Resistors are one of the most basic passive components in electronic circuits and are used for current control, voltage dividing, current limiting and so on. Resistors can be classified into various types according to their materials, structures and applications.

Classification of Resistors

Distinguished by resistance characteristics

1.Fixed Resistors
Characteristics: Fixed resistance value, not adjustable.
Common type:
Metal Film Resistors: High precision, good stability, used in precision circuits.
Carbon Film Resistors: Low cost, high versatility, suitable for general circuits.
Chip Resistors (SMD): Small size, suitable for high density PCB design.
Usage: Current limiting, voltage divider, pull-up/down and other basic circuits.
2.Variable Resistors
Features: Resistance value can be adjusted manually or automatically.
Common types:
Potentiometer: knob adjustment (e.g. volume control).
Trimmer Resistor (Trimpot): Used for circuit calibration, tool adjustment is required.
Digital Potentiometer: Adjustment by electrical signal (e.g. I²C), suitable for automation control.
Usage: Dimming, signal adjustment, circuit calibration, etc.
3.Special Resistors
Characteristics: Resistance value varies with environmental factors.
Common types:
Thermistor: Resistance value changes when the temperature changes (NTC resistance value decreases when the temperature rises, PTC resistance value rises when the temperature rises).
Light Dependent Resistor (LDR): The stronger the light, the lower the resistance value (e.g. automatic street light).
Voltage Dependent Resistor (VDR): resistance drops when voltage is too high, used for over-voltage protection.
Uses: Sensors, protection circuits, automatic control, etc.

Distinguished by material

1. Carbon Film Resistors
   Characteristics: lower cost, moderate resistance accuracy, general temperature stability.
   Applications: Widely used in consumer electronics, basic circuit design, such as LED current limiting, signal voltage divider.
2. Metal Film Resistors
   Characteristics: High precision (±1% or higher), low temperature coefficient, good long-term stability.
   Applications: precision instruments, measuring equipment, audio circuits and other occasions requiring high precision.
3. Wirewound Resistors
   Characteristics: High power (up to tens of watts), high temperature resistance, but poor high frequency characteristics.
   Applications: power supply circuits, motor control, high current loads and other scenarios that require high power tolerance.
4. Film Chip Resistors (SMD)
   Characteristics: Small size, suitable for surface mounting (SMT), better precision and stability.
   Applications: Smart phones, computer motherboards, high frequency circuits and other compact electronic devices.
5. Ceramic Resistors (e.g. Thick Film/Power Type)
   Characteristics: High voltage and high temperature resistance, suitable for harsh environments.
   Applications: power adapters, industrial control systems, electric vehicles and other high power/high voltage devices.

Distinguish by Application

1. Current Limiting Protective Resistors
   These resistors are mainly used for controlling the current level and protecting the circuit. Typical representative is the fuse resistor, which not only has the current limiting function of ordinary resistors, but also can fuse to protect the circuit in case of overcurrent. They are commonly used in power supply inputs and various applications that require current protection.
2. Voltage Sharing Resistors
   The potentiometer is the most typical variable voltage divider resistor to realize voltage regulation through the resistor voltage divider network. These resistors are widely used in analog circuits for voltage regulation, signal amplitude control, and other scenarios, such as volume adjustment of audio equipment.
3. Signal Stabilizing Resistors
   Pull-up/down resistors are key components in digital circuits to ensure signal stabilization. They provide a defined logic level for floating pins and prevent false triggering. They are essential in MCU interface circuits and bus systems.
4. Load Analog Type Resistors
   Used for power testing, circuit debugging and other occasions to simulate actual load conditions. These resistors need to have good power tolerance and are commonly used for aging test and performance verification of power supply products.
5. Current Sense Resistors
   Shunt Resistors are used for current detection by measuring the small voltage drop, requiring accurate resistance value and good temperature stability. Widely used in power management, battery monitoring and other applications that require accurate current measurement.
6. Circuit Connection Resistors
   The 0Ω resistor is very important in PCB design although its resistance value is zero. It can be used as a jumper and retains flexibility for later debugging, making it a practical component in circuit board design.
   Each functional resistor has its own specific application scenarios and selection requirements, engineers need to choose the right type of resistor according to the functional requirements of the circuit. In the actual design, it is often necessary to consider the resistance accuracy, power specifications, temperature coefficient and other parameters of the resistor indicators.

Advantages of resistors

1.Current limitation
Resistors in the circuit mainly play the role of limiting the current, to protect the other components in the circuit from excessive current damage.
2.Voltage and Current Sharing
Resistors can be used to divide voltage and current to help stabilize the voltage and current in the circuit and ensure the normal operation of the circuit.
3.Energy Conversion
Resistors convert electrical energy into thermal energy, and are indispensable energy-consuming components in electronic circuits. This energy conversion function makes resistors widely used in many circuits.
4.Design Flexibility
Resistors are available in a wide range of types and sizes, including fixed resistors and variable resistors (such as potentiometers), providing a wealth of options and flexibility in circuit design.
5.Cost Effectiveness
The manufacturing process of resistors is mature and relatively low cost, making them suitable for mass production and application.

Functions of Common Resistors

1.0Ω Resistors (Zero Ohm Resistors)
Used as a circuit jumper in PCB design to facilitate late debugging and circuit modification. More suitable for automated SMD production than traditional jumper wires to improve manufacturing efficiency. Mainly used in: circuit module isolation, test point connection, compatible design and other scenarios.
2.Current Limiting Resistors
Stabilizes the working current and protects sensitive components such as LEDs and vacuum tubes from current fluctuations. Precise selection of resistance value and proper power specification are essential. Mainly used in: LED driver circuit, tube amplifier, etc.
3.Pull-up/Pull-down Resistors
Provides a defined logic level for digital circuits and prevents malfunctions caused by MCU pin dangling. Resistance value selection needs to balance power consumption and response speed (usually 4.7kΩ-10kΩ). Mainly used in: I2C bus, key input circuit, digital interface.
4.Shunt Resistors (Current Detection Resistors)
Accurate current detection is realized by measuring tiny voltage drop (mV level). Low resistance value, high precision, excellent temperature stability. Main applications: power management systems, battery monitoring, motor control, etc.
5.Thermistors
NTC type: resistance value decreases with increasing temperature, widely used in temperature sensing and compensation.
PTC type: resistance value increases dramatically with temperature, commonly used in over-current protection and self-recovery insurance.
Application difference: NTC is used for temperature measurement, PTC is used for circuit protection.
6.Light Dependent Resistor (LDR)
Resistance value changes with light intensity (the stronger the light, the lower the resistance value). Low cost, easy to use, no need for additional driving circuit. Mainly used in: automatic lighting system, light intensity detection, security equipment.
7.High Power Variable Resistors
Adjust high current circuit parameters, such as motor speed, power supply output voltage, etc.. Made of wirewound or ceramic material, with excellent heat dissipation performance. Mainly used in: industrial control system, high power supply regulation, etc.

Resistor Symbols & Formulas

Resistor Symbols

1.Standard Fixed Resistor (IEC & ANSI)
IEC: ━━━━━━━━━━
ANSI: ~/~ ~
2.Variable Resistor/Potentiometer
IEC: ━━━━━━━━━━
╲
ANSI: ~/~ ╱~
3.Thermistor (Temperature-Sensitive)
━━━━━━━⊓⊔━━━━━━ (IEC)
4.Varistor (Voltage-Dependent)
━━━━━━━⋂⋃━━━━━━ (IEC)

Key Formulas

1.Ohm’s Law (DC Circuits)

Where:
V = Voltage (V)
I = Current (A)
R = Resistance (Ω)
2.Power Dissipation

P = Power (W)
3.Series Resistance

4.Parallel Resistance

For two resistors

Temperature Dependence

α = Temp. coefficient (1/°C)
RT​ = Resistance at temp. T

Color Code Chart (4-Band Example):

Relationship between different resistors

1.Complementary Functions

In circuit design, various types of resistors work together to achieve a more complete function:
Foundation and Adjustment Match
Fixed resistors provide the basic stability of the circuit, variable resistors realize the dynamic adjustment of parameters, and special resistors give the ability to perceive the environment, e.g. fixed resistors set the reference, potentiometers fine-tune the parameters.
Digital and Analog
Pull-up / pull-down resistors to ensure the reliability of digital signals, shunt resistors to achieve accurate measurement of analog current. For example: MCU systems use both pull-up resistors and current detection resistors.

2.Replaceability

Process Replacement
0Ω resistors and jumper wires, same function, but 0Ω resistors are more suitable for automated production. Plug-in and chip, according to the production process to choose the right package.
Performance Replacement
Metal film can replace carbon film to improve precision but increase cost, wirewound resistors to replace ordinary resistors to meet the demand for high-power, replacement needs to assess the cost, precision, power and other parameters.

3.Combined use

Sensing and Detection Combination
Thermistor + fixed resistor forming a voltage divider circuit = temperature detection.
Photoresistor + adjustable resistor = adaptive brightness control.
Precision Measurement Combination
Shunt resistor + op-amp = high precision current detection
Precision resistor + potentiometer = adjustable reference voltage source
Protection circuit combination
PTC resistor + fixed resistor = overcurrent protection
Varistor + Discharge Resistor = Surge Protection
These combinations reflect the synergistic effect of resistors in the circuit. In actual design, engineers need to be based on specific needs, balancing cost and performance, coordinating static parameters and dynamic adjustment, taking into account the basic functions and special needs.

Resistors in PCB

1.Current Limiting
Resistors can effectively limit the current of precision LEDs, integrated circuits and other components, preventing these components from being damaged by excessive current.
2.Voltage divider function
By connecting resistors in series, a voltage divider can be formed, enabling the power supply to output a lower voltage to meet the needs of the circuit.
3.Logic Voltage Stabilization
In digital logic circuits, resistors are often used in conjunction with pull-up/pull-down resistors to ensure that the circuit maintains a known logic voltage level when inputs are not driven.
4.Bias Supply
Resistors provide transistor amplifiers and other analog circuits with the proper DC bias voltage or current to ensure proper circuit operation.
5.Feedback Control
In analog circuits such as operational amplifiers, ADCs, DACs, etc., resistors provide precise control of gain and response through a feedback mechanism.
6.Pulse Shaping
Resistors combined with capacitors can form RC timing circuits for pulse generation and shaping.
7.ESD Protection
Resistors are effective in preventing damage to circuits caused by electrostatic discharges, protecting electronic equipment from damage.
8.Heating
Wirewound power resistors are able to efficiently convert electrical energy into heat and are commonly used in heating applications.

Application Areas

1.Consumer electronics, power management core components.
2.Automotive electronics, high reliability requirements.
3.communication equipment, signal conditioning key components. 4. industrial control, sensor signal conditioning, circuit protection core devices, power distribution important components.
4.Industrial control, sensor signal conditioning, circuit protection core devices, power distribution important components.
5.High-end applications
Medical equipment, precision current control.
Aerospace, extreme environment tolerance.
Military equipment, EMI suppression protection.
There are many types of resistors, each suitable for a specific application. Understanding their characteristics and functions helps to optimize circuit design, thereby improving reliability and performance. In practice, resistors should be selected based on circuit requirements, taking into account cost, accuracy and power handling capability.

A capacitor is a passive electronic component used to store electrical energy. Its core structure consists of two conductors (usually metal plates) that are insulated from each other and located close to each other. When a DC voltage is applied to the ends of a capacitor, positive and negative charges accumulate on each of the two plates, creating an electrostatic field between them. This process of charge separation and electric field establishment realizes the storage of electrical energy, and its energy storage capacity is determined by the capacity of the capacitor. Capacitors are able to respond quickly to voltage changes during charging and discharging, a characteristic that makes them valuable for a wide range of applications in electronic circuits.

Classification of capacitors

1.General-purpose capacitors

Mainly includes ceramic capacitors (such as high-frequency circuit in the MLCC), film capacitors (such as polyester capacitors, polystyrene capacitors, etc.), with good stability, low dielectric loss, widely used in coupling, bypass, oscillation and other conventional circuits.

2. Electrolytic capacitors

Represented by aluminum electrolytic capacitors and tantalum electrolytic capacitors, they have the advantages of large capacity and small volume, and are mainly used in scenarios such as power supply filtering (e.g., the output of switching power supply), energy storage, and low-frequency signal coupling.

3. Adjustable capacitors

Through mechanical adjustment to change the pole plate spacing or effective area to achieve changes in capacitance value, typically used in radio tuning circuits (such as old-fashioned radio selector), high-frequency impedance matching and other occasions that require precise adjustment.

4. Supercapacitor (double layer capacitor)

Between the traditional capacitor and battery energy storage devices, with very high power density and fast charge and discharge characteristics, suitable for new energy vehicles start-stop system, grid energy storage and other high-power applications.

5.Safety Capacitors

Including X capacitors (across the line to suppress differential mode interference) and Y capacitors (between the line and ground to suppress common-mode interference), specifically used for power supply EMI filtering, to ensure that electrical equipment in line with electromagnetic compatibility standards.

6.Power Capacitors

Such as power electronics used in DC support capacitors, AC filter capacitors, etc., mainly used in frequency converters, inverters and other high-power power conversion devices.

The role of capacitors

1. Energy storage and fast charging and discharging

Capacitors can store electrical energy in the form of electrostatic field and support high-speed charging and discharging. Compared with chemical batteries, its charging and discharging speed is faster (milliseconds), and the cycle life can reach more than tens of thousands of times, so it has a unique advantage in the scene that requires instantaneous high current or rapid energy conversion (such as electric vehicle acceleration, braking energy recovery, pulse power system).

2. Isolation through the cross (coupling and decoupling)

Capacitors present a high impedance to DC, blocking the DC component while allowing AC signals to pass through. This characteristic makes it widely used in coupling circuits (such as audio signal transmission in the isolation capacitor) and decoupling circuits (to eliminate power supply noise interference).

3. Filtering and voltage stabilization

In power supply circuits, capacitors can effectively filter out the rectified pulsating components, the output of a smooth DC voltage (such as electrolytic capacitors used in power supply filtering). In addition, in signal processing, capacitors can be used with resistors or inductors to form a low-pass, high-pass filter to suppress high-frequency noise and improve signal quality.

4. Tuning and resonance (LC circuit)

Capacitors and inductors can be combined to form LC resonant circuits for frequency selection, tuning and other applications, such as radio receiver FM circuits, oscillators and RF matching networks.

5. Motor start and phase compensation

In single-phase AC motors, capacitors assist in motor starting (e.g., starting capacitors) by generating a phase difference to form a rotating magnetic field. In addition, in power systems, capacitors are used for power factor correction to improve the efficiency of power utilization.
These properties of capacitors make them play a key role in electronic circuits, power systems, new energy technologies and communication equipment.

Test capacitors for faults

1. Appearance

Power capacitor shell is intact, there is no obvious expansion, deformation, cracks and other phenomena. If the above situation occurs, it means that the capacitor has a serious failure, that is, it can not continue to use.
Whether the terminal connection of the capacitor is firm, with or without loose, corrosion and other problems. Problems with the terminals may lead to poor contact and affect the normal operation of the capacitor.

2. Capacity test

Measure the capacity of the power capacitor to see if the actual capacity of the capacitor matches the nominal capacity. If the actual capacity is too much lower than the nominal capacity, it means that the capacitor has aged and failed.

3.Insulation resistance test

Measure the insulation resistance of the capacitor with relevant instruments. Under normal circumstances, the insulation resistance should be greater than 10 megohms. If the insulation resistance is lower than this value, it means that the insulation performance of the capacitor may have been damaged and further inspection is required.

4. Voltage and current test

Measure the voltage value of the power capacitor during operation. If the voltage value fluctuates greatly, it means that the power capacitor may have problems.
Measure the current value of the capacitor at the rated voltage. If the actual current value exceeds the current value in the guide, it indicates that the capacitor may be overloaded.

5. Temperature Test

Test whether the operating temperature of the power capacitor is within the specified range. Normally the capacitor should be operated under suitable temperature conditions. If the temperature is too high, it proves that the capacitor may have some kind of failure, need to stop using immediately.
The above is the method to determine whether the power capacitor is faulty. In actual operation, power capacitors should be inspected regularly, and if abnormalities are found, they should be stopped in time to avoid triggering safety hazards.

Methods of testing capacitors

1. Digital multimeter test method

Operation Procedure:
Make sure the capacitor is completely discharged
Set the multimeter to resistance (recommended to choose ×1k or higher level)
Connect the test pens to both ends of the capacitor.
Observe the reading change:
Normal performance: the reading is displayed briefly and then quickly return to the “OL” (open circuit) state
Failure performance: Continuously display a fixed resistance value or zero resistance.
Caution:
Make sure that the test is fully discharged before testing
10 seconds or more between each test
Repeat the test 3 times to confirm the consistency of the results

2. Analog multimeter test method

Detection process:
Select the appropriate resistance level (recommended ×100 or ×1k)
Connect the test pen and observe the pointer movement:
Good capacitance: the pointer swings sharply to the right, and then slowly back to ∞!
Short-circuit fault: the pointer stops at the low resistance position
Open-circuit fault: the pointer does not move at all
Technical points:
Electrolytic capacitors need to pay attention to the polarity (black pen to the positive pole)
Large-capacity capacitors (>10μF) pointer swing more obvious
After the test need to wait for the pointer to return to the full position

3. Capacitance gear direct measurement method

Implement the specification:
Choose a digital multimeter with capacitance measurement function.
Measurement range selection:
Small capacitance (pF level): Use the special test clip.
Large capacitance (μF level): direct connection test
Result Judgment Criteria:
Pass: Measured value within ±20% of nominal value.
Note: Electrolytic capacitors allow +50%/-20% deviation.
Failure: display “0” or far below the nominal lower limit value

4. Voltage Test Method

Professional operation guide:
Build the test circuit:
Supply voltage ≤ capacitor rated voltage
Series current limiting resistor (1-10kΩ)
Measurement process:
At the beginning of charging: voltage should rise rapidly
After stabilization: voltage should be close to the supply voltage
Fault characteristics:
Voltage rises slowly: capacity decay
Voltage cannot be maintained: excessive leakage current
Zero voltage: complete failure

5. Time constant measurements

Precision measurement program:
Standard test circuit:
Known precision resistor R (1kΩ-10kΩ recommended)
Oscilloscope to monitor charging curve
Calculation method:
Measure time to 63.2% supply voltage (τ)
Calculate capacity: C = τ/R
Engineering Application Tip:
Suitable for 1μF-1000μF capacity range
Need to consider the effect of internal resistance of multimeter
Recommended to use square wave signal source to improve accuracy

Comprehensive testing suggestions:

Prioritize the use of direct measurement of capacitance
Difficult faults using multiple methods of cross-verification
High-voltage capacitors must be tested with specialized equipment
The establishment of testing records to track the deterioration trend
Note: All testing must comply with electrical safety codes, high-voltage capacitors must be fully discharged before testing!

Apacitors in PCBs

Coupling Function

Capacitors act as coupling components in circuits, effectively transmitting low-frequency signals and enabling signal amplification while isolating the DC operating points of adjacent circuit stages to prevent mutual interference. To ensure efficient transmission of low-frequency signal components, large-capacity electrolytic capacitors (typically in the μF range) are commonly used as coupling capacitors in design.

Filtering Function

In power supply circuits, capacitors filter out high-frequency noise from AC signals, delivering a smooth DC output. Specifically, large electrolytic capacitors stabilize pulsating DC voltage through charge-discharge processes. To enhance power supply stability, electrolytic capacitors ranging from tens to hundreds of microfarads are often connected in parallel at the power output and load input to suppress voltage fluctuations caused by load variations.

Energy Storage Function

Capacitors serve as energy storage components, storing charge and rapidly releasing it when needed to provide instantaneous high current or act as a backup power source. Additionally, capacitors can form RC timing circuits with resistors to achieve precise time delays or timing functions, widely used in sequential control circuits.

Utilization and Optimization of Parasitic Capacitance

In high-speed PCB design, parasitic capacitance can be strategically leveraged to enhance circuit performance. For example:
Adjusting trace layouts to utilize parasitic capacitance for impedance matching.
The parallel-plate structure formed by power-ground planes creates distributed capacitance, providing low-impedance charge storage for high-speed components to meet instantaneous high-current demands.
Conclusion
Capacitors exhibit multifunctionality in PCB design. Their selection and placement must be optimized based on specific circuit requirements (e.g., frequency characteristics, energy storage needs, noise suppression) to achieve optimal performance.