When the temperature of a high Tg printed board rises to a certain area, the substrate will change from “glass state” to “rubber state”. The temperature at this time is called the glass transition temperature (Tg) of the board. In other words, Tg is the maximum temperature (℃) that the substrate remains rigid. That is to say, ordinary PCB substrate materials not only produce softening, deformation, melting and other phenomena at high temperatures, but also show a sharp decline in mechanical and electrical characteristics (I think everyone does not want to see this in their products).
The general Tg sheet is above 130 degrees, the high Tg is generally greater than 170 degrees, and the medium Tg is approximately greater than 150 degrees. Generally, PCB printed boards with Tg≥170℃ are called high Tg printed boards. The Tg of the substrate is increased, and the heat resistance, moisture resistance, chemical resistance, stability and other characteristics of the printed board will be improved and improved. The higher the TG value, the better the temperature resistance of the sheet, especially in the lead-free process, high Tg applications are more.