How will high frequency circuit board materials be affected?
21 January 2025
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The selection of high-frequency circuit board materials has a very important impact on the performance quality of high-frequency circuits. The following will elaborate on the four influencing factors of dielectric constant, thermal expansion coefficient, heat-resistant temperature and water absorption rate on high-frequency circuit board materials, and provide some relevant data and parameters.
Dielectric constant
Dielectric constant refers to the ratio of dielectric capacitance to electric field strength and is one of the important performance parameters of high-frequency circuit board materials. Lower dielectric constant improves signal transmission rate and transmission distance. Common high-frequency circuit board materials include FR-4, PTFE, RO4350B, etc. For example, the dielectric constant of PTFE is about 2.1-2.2, and lower values help increase signal speed and transmission distance.
Thermal expansion coefficient
The thermal expansion coefficient refers to the ratio of the deformation amount of a material to the temperature change amount when the temperature changes. In high-frequency circuits, changes in frequency will cause thermal expansion in nature, so the thermal expansion coefficient is one of the important factors affecting the performance of high-frequency circuit boards. If the thermal expansion coefficient is too large, it may cause circuit board deformation and micro-cracks, affecting the stability and performance of the circuit. Different materials have different coefficients of thermal expansion, so the application environment needs to be considered when selecting materials. For example, the thermal expansion coefficient of FR-4 material is about 13-18 ppm/℃, and the thermal expansion coefficient of PTFE material is about 15-25 ppm/℃.
Heat resistance temperature
Heat-resistant temperature refers to the highest temperature that a high-frequency circuit board can withstand. In high-frequency circuits, circuit boards need to withstand higher operating temperatures and peak temperatures, so materials with higher heat-resistant temperatures need to be selected to ensure the safety and reliability of the circuit board. Common high-frequency circuit board materials such as PTFE and Rogers have different heat-resistant temperatures. For example, PTFE material has good heat resistance and can withstand operating temperatures up to 260°C.
Water absorption
The water absorption rate of high-frequency circuit board materials refers to the ratio of the mass increment of the material after absorbing water to the original mass of the material. Moisture can have a huge impact and damage circuit boards, especially in holes and corners where water can accumulate. Some low-quality materials can cause problems such as small cracks in circuit boards, shrinkage and blockage of wires. Common materials such as FR-4 have higher water absorption, while PTFE has lower water absorption, which is more beneficial to the performance stability of the circuit.
In practical applications, appropriate high-frequency circuit board materials need to be selected according to specific application environments and needs to ensure circuit performance and reliability. Researchers still need to continue in-depth research to discover more optimization methods and performance performance of high-frequency circuit board materials. The above data and parameters are for reference only, and the specific selection should be comprehensively considered based on the actual situation.
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