1. Definition and Function of PCB
PCB (Printed Circuit Board) is the core basic component of electronic devices, used to carry electronic components and achieve electrical connections. It achieves the following functions through the combination of conductive layer, insulating layer, and top layer:
Supporting components: Provide installation platforms for resistors, capacitors, chips, etc.
Electrical connection: Connecting components through copper wires to transmit electrical signals and power.
Protection circuit: The insulation layer isolates different circuit areas to prevent short circuits or current leakage.
Signal transmission: Ensure efficient and stable transmission of signals.
2. Types and manufacturing processes of PCBs
type
Single panel: Components are concentrated on one side, wires are on the other side, suitable for simple circuits.
Double sided board: Both sides can be wired, with an insulation layer in the middle to reduce wiring difficulty.
Multilayer board: contains multiple conductive and insulating layers, supports complex circuits (such as 8-40 layers), and is used for high-performance devices (such as AI servers).
manufacturing process
Material preparation: substrate (such as FR-4), copper foil, insulation layer, etc.
Drawing design: Design circuit layout using EDA tools.
Imaging and etching: Transfer the circuit pattern to the substrate and etch excess copper layers.
Drilling and plugins: Drilling to install component pins and soldering plugins.
Testing: Verify electrical performance and insulation.
3. PCB design process
Preliminary preparation:
Create component packaging library (PCB library) and schematic diagram (SCH library).
Structural design:
Determine the size of the circuit board, mechanical positioning holes, installation holes, etc.
Layout and wiring:
Layout principle: Divide by function (such as digital/analog circuits) and prioritize placement of key components.
Wiring rules: Power/ground wires should be bolded first, and signal wires should avoid parallel routing to reduce interference.
Design verification:
DRC inspection (design rule inspection): Ensure that the line width and spacing meet the requirements.
ERC check (electrical rule check): Verify network connectivity.
4. Key parameters and material selection
key parameter
Tg (glass transition temperature):
Definition: The temperature at which a resin changes from a solid state to a rubber like state, affecting its heat resistance.
Grading: Low Tg (130-150 ℃), Medium Tg (150-170 ℃), High Tg (≥ 170 ℃).
Dk (dielectric constant):
Affects signal transmission speed, the smaller the Dk, the faster the speed.
Df (dielectric loss factor):
Measuring signal transmission loss, the smaller the Df, the higher the signal quality.
CAF (Conductive Anode Wire):
Evaluate insulation performance to prevent electrical leakage in humid environments.
Material selection
Substrate:
FR-4： Universal type, Tg about 130-170 ℃.
High Tg material: suitable for high temperature environments (such as automotive electronics).
Copper foil:
Thickness affects conductivity (commonly used 1oz=35 μ m).
Insulation layer:
Epoxy resin, polyimide (PI), etc., provide electrical isolation.
5. Application Fields
Communication: 5G base station, satellite system.
Medical: Diagnostic equipment (such as CT scanners), implantable devices.
Consumer electronics: smartphones, tablets, smartwatches.
Automotive electronics: engine control module, in car entertainment system.
Aerospace: Satellite and aircraft navigation equipment.
Military defense: radar systems, encrypted communication equipment.
6. Future Development Trends
Market size:
The global PCB market size is expected to reach 96.8 billion US dollars by 2025, with China accounting for over 50%.
Technical direction:
High density interconnect (HDI): supports miniaturized devices such as wearable devices.
High frequency and high-speed materials: meet the needs of 5G and the Internet of Things (such as Megtron 6).
Flexible PCB: Applied to medical equipment and foldable mobile phones.
Green manufacturing: lead-free process, environmentally friendly materials.
summarize
As the foundation of electronic devices, PCB technology covers multiple aspects such as materials, design, and manufacturing. With the demand for miniaturization and high performance of electronic products, PCB technology is developing towards high-density, high-frequency, high-speed, and green direction.
