A high temperature PCB is a PCB designed to withstand high temperatures. These PCBs are also called high Tg PCBs. They are used for high temperature operation.
However, these PCBs require special materials to withstand high temperatures of 150 to 170°C.
For continuous thermal loads, a simple rule of thumb should be followed for high-temperature PCBs at operating temperatures of approximately 25°C below Tg.
Therefore, if your product is in the temperature range of 130°C or higher, it is recommended to use high Tg materials.
Material considerations for high Tg PCBs follow a simple rule of thumb. According to a rule of thumb, if the operating temperature is about 25°C lower than the glass transition temperature, the PCB material will withstand an increasing thermal load. This means that if the expected operating temperature will rise to 130°C, the board must be made of high Tg materials. When selecting materials for high-temperature PCBs, the following factors must be considered.
Low soot formation
There are several mature materials suitable for high Tg PCB manufacturing.
The materials used to manufacture high Tg PCBs are flame retardant materials. Glass epoxy resin has flame retardant properties. Therefore, polymers and composites containing epoxy resins are preferred for high Tg PCB manufacturing.
The most common high Tg materials include: ISOLA IS410, ISOLA IS420, ISOLA G200, SY-S1000-2, ITEQ IT-180A.
IS410 is based on a high-Tg epoxy system with a nominal glass transition temperature of 170 - 180 °C (DSC). It is suitable for multiple thermal excursions and it has cleared the 6X solder test under 288°C temperature. It is also suitable for lead-free soldering in high-temperature PCB manufacturing.
IS420 is a high performance 170°C glass transition temperature (Tg) FR-4 system for multilayer Printed Wiring Board (PWB) applications where maximum thermal performance and reliability are required. IS420 laminate and prepreg products are manufactured with a unique high performance multifunctional epoxy resin, reinforced with electrical grade (E-glass) glass fabric. This system provides improved thermal performance and low expansion rates in comparison to traditional FR-4 while retaining FR-4 processability.
G200 is a combination of epoxy resin and Bismaleimide/Triazine (BT). It offers high thermal resistance, high mechanical strength, and absolute electrical performance. It is suitable for multi-layered Printed wiring boards.
As we all know, designers are squeezing more performance out of printed circuit boards. Power density is rising, and the ensuing high temperatures can cause severe damage to conductors and dielectrics. Elevated temperature-whether due to I2R losses or environmental factors-will affect the thermal resistance and electrical impedance, resulting in unstable system performance (even if it is not a complete failure). The difference in the thermal expansion rate between a conductor and a dielectric (a measure of the tendency of a material to expand when heated and contract when cooled) can cause mechanical stress, which can lead to cracks and connection failures, especially when the circuit board is periodically heated and cooled . If the temperature is high enough, the dielectric may completely lose its structural integrity, leaving the first dominoes in trouble.