What is High TG PCB?

What is High TG PCB?

PCBs are also made from different polymer bases, including FR-4 and Polyimide. Thus, these materials also have a TG value that must be considered before using them for the PCB. Keep in mind that TG is only related to polymer PCBs; there is nothing to worry about the temperature in the case of metal core PCBs.

PCB bases have a typical TG value. For instance, the typical TG of FR-4 is 130°C. We mean that the value is above the standard TG value by high TG. FR-4 boards are also available in higher TGs, known as High TG PCBs. Generally, PCBs having a TG of more than 170°C are known as High TG PCBs. However, it also depends on the base material/substrate type.

How to differentiate high Tg materials?
Materials TG MOT
FR-4 common Tg 130℃ 110℃
FR-4 Medium Tg 150℃ 130℃
FR-4 High Tg 170℃ 150℃
PI Ultra-high Tg 260℃ 240℃
Tg value of common PCB materials
Tg is defined as “glass transition temperature,” and there is no Tg value in ceramic substrates, polytetrafluoroethylene substrates, polyimide (PI) substrates that do not contain any glass fibers. However, for these three substrates, it is generally considered that the Tg value is greater than 200°C. In this case, Tg only represents its high-temperature resistance.
Materials TG
CEM-1 110-130℃
FR-4 120-180℃
PTFE 200-260℃
Ceramic 200-300℃
PI 200-350℃

High TG PCBs have the capability to withstand higher temperature stress. They can work in extreme conditions. If the operating temperature is high, it is necessary to use a High TG PCB to ensure optimum and reliable performance.

 

Why is High TG PCB Used?

PCBs are used in different environments. The conditions can be normal or extreme, but we cannot use a PCB in every condition. For instance, if the TG value of a PCB is 150°C, then we can use it in any environment having an operating temperature below 125°C.

If the temperature of the environment, where the PCB is in operation, increases above the TG value, the PCB will start to change its state. It will become a rubbery material, which will affect the performance of the PCB. It could bend and change its shape. The electrical performance of the PCB is badly affected. In extreme cases, it can stop working. Thus, it is necessary to ensure that the operating temperature is 25°C lower than the TG.

The 25°C difference ensures no change in the state of the polymer. It is because the polymer experience changes when the temperature is near TG, and in this case, the performance and lifespan of the PCB are badly affected. Therefore, it is a must to have this difference in temperature.

Some applications have a high operating temperature. They require a high TG PCB for optimum performance. Standard and normal PCBs cannot work in such areas. Therefore, High TG PCBs enjoy high demand and importance in the industry. Moreover, some projects require high TG PCBs to get certification and compliance.

High TG materials are widely used for making multilayer PCBs. The component density in multilayer PCBs is more than a simple PCB. The surface is thickly populated, which is why the heat generation is more than a single-layer PCB. Therefore, it is necessary to use a high TG material to deal with excessive heat and higher operating temperatures. Another way is to reduce the heat generation of the PCB board, but this is neither cost-effective nor easy. You will need to change the components and design, and sometimes it is not possible. Thus, the only cost-effective and feasible solution is using a High TG PCB.