What is High Tg PCB?

Tg is the glass transition temperature of a Printed Circuit Board. It is that temperature at which the base material of a PCB starts to transform from a brittle condition to a soft, elastic one. A PCB whose glass transition temperature (Tg) is greater than 170 ℃ is known as a High Tg PCB.  General, Tg values for PCBs lie between 120 and 170 ℃.

Every PCB has a different Tg value based on its substrate. If the operating temperature of the board exceeds its Tg value, the board will begin to change its state which will have an adverse effect on the functionality of the PCB. High Tg PCB boards perform better at high temperatures with better stability as the substrate provides better heat resistance, chemical and mechanical stability to the board.

When selecting a PCB, the Tg value should be at least 20-25 degree Celsius higher than the expected operating temperature of the device in which the PCB is used. For instance, if you have a PCB with a Tg value of 130 degree Celsius than the working temperature of the device should be lower than 110 degree Celsius.

Advantages of High Tg PCB

Withstand High Power Density Designs: If a device has high power density with very high heat generation rate then High Tg PCB is a good solution for heat management. 

Reduction in the heat generation of a regular PCB can be accomplished by using a larger PCB, changing the design and power requirements of a device. Alternatively, a high Tg PCB board can be used.

Ideal for Multilayer & HDI PCBs: Multilayer & HDI PCBs are more compact and have very dense circuits which can result in high levels of heat dissipation. High Tg boards are often used in these kinds of PCBs to ensure reliability during operation.

Higher Stability: If the Tg of a PCB substrate is increased then it will automatically increase the heat resistance, moisture resistance, chemical resistance and stability of the device.