Tg refers to the high heat resistance in PCB raw materials. Here’s a useful guide to classifying printed circuit boards based on temperature resistance:
- Standard copper-clad laminate PCBs: Between 130°C and 140°C
- Middle Tg PCBs: Greater than 150°C
- High Tg PCBs: Greater than 170°C with a typical range of 180°C to 225°C
There are many materials, such as rigid and flex polyimide material, with an average Tg of 220°C. Hydro-carbon ceramic-filled substrate has a temperature greater than 280°C and Teflon-based laminates have a temperature of >300*C.
A high Tg PCB contains a resin system that’s designed to withstand lead-free soldering and enables higher mechanical strength in harsh, higher temperature environments. Resin refers to any solid or semisolid organic substance that’s often used in plastics, varnishes, etc.
In other words, if your PCB has a higher Tg, it has more stability and a better chance of resisting heat, moisture, chemicals and other characteristics that would otherwise render the PCB ineffective.
In recent years, more and more PCB customers are requesting to manufacture their projects with high Tg due to its resiliency, high mechanical strength, and ability to withstand harsh environments.
Now let’s explore high Tg characteristics, materials, and key considerations when it comes to the two main types of circuit boards: rigid and flex.