What are the common materials used in PCB circuit boards?

PCB (Printed Circuit Board) is a core fundamental component of modern electronic devices. It not only serves as the physical support for electronic components, but also acts as the key carrier for electrical interconnection and signal transmission. Like a neural network in the electronic world, the PCB efficiently and reliably connects various components, forming a complete circuit system.

Base Materials

1. Phenolic Paper Substrate: The most traditional PCB base material, made from paper impregnated with phenolic resin. It offers good machinability and low cost, but has poor heat resistance and dielectric properties. It is only suitable for consumer electronics and household appliances with low electrical performance requirements and mild environments.
2. Epoxy Glass Fiber Substrate (FR-4): Currently the most widely used, made from epoxy resin and glass fiber cloth. It features excellent electrical properties, mechanical strength, heat resistance, and chemical stability. FR-4 is widely adopted in general electronic devices such as computers, communication equipment, and industrial control systems.
3. Polyimide Substrate: Uses polyimide film as the insulating layer, offering extremely high heat resistance (continuous working temperatures above 260°C), excellent electrical properties, low moisture absorption, and good mechanical strength. Mainly used in aerospace, military, automotive electronics, and other fields with high reliability and harsh environments, as well as high-frequency circuits like microwave and RFID.
4. Aluminum Substrate: Uses aluminum alloy as the base, covered by an insulating dielectric layer. It has excellent heat dissipation, effectively solving heat management issues in high-power electronic devices. It also has good mechanical strength, electromagnetic shielding, and certain corrosion resistance. Commonly used in LED lighting, power modules, automotive electronics, audio equipment, and other applications requiring efficient heat dissipation.
5. Copper Substrate: Uses high-purity copper as the base, with a composite insulating layer. Copper substrates have outstanding thermal conductivity, much higher than aluminum, and are especially suitable for high-power, high-heat applications such as high-brightness LEDs, power modules, electric vehicles, and telecom base stations. They also offer high mechanical strength and corrosion resistance, suitable for harsh environments.
6. Specialty Substrates: For high-frequency, high-speed, or highly reliable electronic products, high-performance materials such as ceramic substrates and PTFE (polytetrafluoroethylene) are also used to meet special electrical and environmental requirements.

Copper Foil

Copper foil is the main material for the conductive layer of PCBs and is divided into two types:

1. Electrolytic Copper Foil: Produced chemically by depositing a uniform copper film on a stainless steel roller, then peeling it off. It is low-cost, available in various thicknesses and sizes, and is the mainstream copper foil type for rigid PCBs.
2. Rolled Copper Foil: Made by repeatedly rolling and annealing copper through physical methods. It has high ductility, making it especially suitable for flexible circuit boards (FPC) and dynamic environments. Its smooth surface and low ridges are ideal for high-frequency and microwave applications, but it is more expensive, has weaker adhesion to substrates, and is limited in width.

Insulation Layer

The insulation layer is located between the copper foil and the base material, ensuring electrical isolation between conductive layers and circuit safety. Main materials include:

• Epoxy Resin: Good insulation and adhesion, low cost, widely used in most PCBs.
• Polyimide: Excellent heat resistance and electrical properties, ideal for high-end, high-frequency, or high-temperature applications.

Protective Layer

1. Solder Mask: Usually green, covers the board surface to protect the circuit from short circuits, defines soldering areas, prevents solder bridges, and improves soldering accuracy and board reliability.
2. Silkscreen Layer: Used for marking component positions, identifiers, warnings, etc. The silkscreen layer aids assembly and later maintenance, helping engineers quickly identify components and traces.

Surface Finishing

To improve solderability, oxidation resistance, and reliability, common surface finishing processes include HASL (hot air solder leveling), ENIG (electroless nickel immersion gold), OSP (organic solderability preservative), and immersion silver, depending on application needs.

Solder

1. Lead-Tin Alloy Solder: Such as 63Sn-37Pb eutectic solder, which provides good conductivity, processability, low melting point, and strong solder joints. However, due to the toxicity of lead, its use is decreasing in favor of environmental protection.
2. Lead-Free Solder: Melting point around 217°C, non-toxic and environmentally friendly, requires stricter processing, and has become the mainstream choice.

Environmental and Sustainable Materials

With increasingly stringent environmental regulations, PCB manufacturing places greater emphasis on halogen-free, RoHS-compliant, and recyclable materials, promoting green and sustainable development in the electronics industry.

Application Fields

Common PCB materials are widely used in consumer electronics, communication devices, industrial control, automotive electronics, medical instruments, smart home, LED lighting, and other areas. Whether for new product prototyping or small-batch trial production, high-quality PCB materials are key to ensuring the performance and reliability of electronic products.