What is High Tg PCB?
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.
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.
Applications of High Temperature PCB: If the electronic product has higher power density where heat generation would have that propensity to disturb heat sink or other parts of the product, High Tg printed circuit boards would be the best solution. Link to the reduction of heat generation of printed circuit boards may affect the weight, cost, power supplied and the ultimate size of the product. Therefore, in other aspects to the implementation of high Tg printed circuit boards is a cost-effective and pragmatic solution. In applications where printed circuit board is subjected to high temperature, it result into damaging the dielectrics and conducting elements, generation of mechanical stress due differences in thermal strain at different points. And it could lead to permanent failure.
Here we can see, more we will try to deal with the heat removal mechanism it will affect the design of the printed circuit board. Limiting the power density of the products will reduce it features and market value at the same time. Inclusion of more number of heat sinks would lead to increase in weight and size of the printed circuit board and the PCB cost as well. Even if the designer is aware of numerous method of heat management in such cases but still it will affect performance of the printed circuit board in some other aspect.
Therefore, to get rid off from all such problems the best way is to implement the high Tg printed circuit board in such high temperature applications. If working temperature of the product is higher than normal (130-140C), then have to use high Tg material which is > 170C, and popular PCB high value are 170C, 175C, and 180C. Normally the PCB Tg value should be at least 10-20C higher than working temperature of product.