FR4 High TG Multilayer HDI PCB

Tg refers to the glass transition temperature. Since the flammability of printed circuit boards (PCBs) is V-0 (UL 94-V0), if the temperature exceeds the specified Tg value, the circuit board will change from a glass state to a rubbery state. Then the function of the PCB will be affected.

If your product operates at higher temperature than usual (130-140C), you must use a high Tg material >170C. The popular PCB high values are 170C, 175C and 180C. Generally, the PCB Tg value should be at least 10-20C higher than the product's operating temperature. If you are a 130TG board, the working temperature will be lower than 110C; if you use a 170 top TG board, the maximum working temperature should be less than 150C.

If your PCB will be subjected to thermal loads below TG and no higher than 25 degrees Celsius, your application requires a high temperature board. If your product operates in a temperature range of 130 degrees Celsius or higher, you will want to use a high TG PCB for safety. The main reason for adopting Hi TG PCB is to move to RoHS PCB. This has led most of the PCB industry to switch to Hi TG materials due to the higher temperatures required for lead-free solder to flow.