How to select PCB materials?

Thickness:Refers to the overall thickness of the PCB, with common specifications of 0.8mm, 1.0mm, 1.6mm and 2.0mm. It shall be selected according to the number of components, installation space and performance requirements.

Coefficient of Thermal Expansion (CTE):The dimensional change rate of the material under temperature fluctuations. The smaller the coefficient, the lower the risk of equipment failure caused by thermal expansion and contraction.

Tensile Strength:The maximum stress that the material can withstand when damaged by external force, which must meet the actual application requirements of the product.

Flammability:Must meet the fire retardant requirements, commonly evaluated by the UL94 standard (V0, V1, V2 ratings).

Dielectric Constant (Dk):Reflects the dielectric properties of the material. The smaller the value, the faster the signal transmission speed.

Thermal Stability:The ability of the substrate to withstand high temperatures and thermal cycling. FR-4, polytetrafluoroethylene (PTFE) and silicon carbide materials have superior thermal stability performance.

①Paper Substrate (Phenolic PCB Paper Substrate)

Made from wood pulp fiber paper as raw material and compounded with phenolic resin, it features low cost and low density, and is mostly used for single-sided PCBs. It is widely applied in low-end power boards such as LED lamp power modules.

②Composite PCB Substrate (Powder Board)

With wood pulp/cotton pulp fiber paper as the core, reinforced by glass fiber cloth on the surface, and compounded with flame-retardant epoxy resin. It balances strength, insulation and cost, and is used for low-end to mid-end products.

③FR-4 (Epoxy Board/Glass Fiber Board)

Made of glass fiber cloth and epoxy resin, it dominates the mainstream of the general PCB market. It is suitable for double-sided PCBs, with good stability and high operating temperature, and is applied to power boards, high-layer circuit boards, communication equipment, etc. Its price is higher than that of composite substrates.

④ High Temperature Board

With high TG (Glass Transition Temperature) as the core feature, it is made of polyimide, can withstand high temperatures up to 300℃, and has strong chemical stability. It is expensive and mainly used in high-end extreme high temperature scenarios such as military industry and aerospace. Ordinary FR-4 has a TG value of about 130℃, which is only suitable for conventional environments.

⑤ Ceramic Substrate

With ceramic as the core material, it has extremely strong insulation and chemical stability, and can withstand high-frequency and high-power signals. It is suitable for high-end fields with stringent performance requirements such as high-end wireless communication, radar and microwave equipment.

⑥ Metal Core Substrate (MCS)

Centered on high thermal conductivity, aluminum substrate is the most common type (aluminum base + insulating layer), suitable for high-power scenarios requiring heat dissipation such as LED, power amplifier and power circuits. It has outstanding heat dissipation performance, but is limited to single-layer layout and cannot be used for multi-layer boards.

⑦Flexible Printed Circuit (FPC) Substrate

With polyimide or polyester film as the base material, it is light, thin, bendable and has high wiring density, suitable for devices with strict space and weight requirements such as mobile phones and tablets. It has low mechanical strength, is not suitable for high-power circuits, and its production process is different from that of ordinary PCBs.

✅ Low-cost low-end applications (LED power supply) → Paper substrate

✅ Low to mid-end single/double-sided PCB → Composite substrate (CEM-1/CEM-3)

✅ General conventional applications (communication, computers) → FR-4

✅ High temperature environments (military industry, aerospace) → High temperature board

✅ High-frequency signal applications (5G/radar) → High-frequency board

✅ High-power heat dissipation requirements → Metal core substrate (e.g. aluminum substrate)

✅ Limited space and bending requirements → FPC

High-performance substrates such as high-temperature boards, high-frequency boards and ceramic substrates have high costs. Avoid "performance overkill" — ordinary consumer electronics do not require military-grade substrates, and conventional signal transmission does not require high-frequency boards.

✅ Temperature: Refer to TG value and maximum operating temperature (approx. 130℃ for FR-4, up to 300℃ for high temperature boards)

✅ Signal: Focus on Dielectric Constant (Dk) and Dissipation Factor (Df) for high-frequency scenarios

✅ Structure: FR-4 for multi-layer boards, metal core substrate for single-layer heat dissipation applications, FPC for bending requirements

• Manufacturability: Meet the requirements of lamination, heat resistance and flame retardant rating to ensure long-term reliability

  
  

• Product Adaptability: High-speed boards require low loss and stable Dk/Df; low-roughness copper foil is preferred for long traces, and pre-simulation is required in the early stage

  
  

• Material Availability: High-frequency substrates have a long procurement lead time, so it is necessary to communicate with the manufacturer in advance for material preparation

  
  

• Cost Adaptation: Match the price sensitivity according to the product type (consumer/military, etc.)

  
  

• Compliance: Meet the requirements of environmental regulations such as RoHS and halogen-free standards.

It refers to the melting point of the resin. Below Tg, the resin is in a rigid glassy state, while above Tg, it is in a flexible rubbery state. It is the core parameter of PCB heat resistance. The higher the Tg, the better the heat resistance and moisture resistance of the substrate; however, an excessively high Tg will make the substrate hard and brittle, affecting its processing and electrical properties. High Tg is recommended for boards with 8 layers or more.

It measures the insulation capacity of the material and affects the characteristic impedance of signal traces (a key focus for boards with impedance control requirements), which is mainly affected by the resin and reinforcing materials. Key point: The smaller the Dk value, the faster the signal propagation speed, so low Dk substrates are preferred for high-speed boards.

It affects the signal transmission quality. The smaller the Df value, the lower the signal loss, which is a mandatory focus for high-frequency, high-speed and radio frequency boards.

It refers to the leakage behavior caused by the migration of copper ions inside the PCB. The more miniaturized and higher density the PCB is, the more important this indicator is. Key point: For high-humidity and high-temperature environments, or designs with small hole-to-trace spacing and high density, the CAF indicator must be focused on to avoid insulation breakdown.