High Tg PCB: What is it?

Do you know what high Tg PCB is? In the modern electronics industry, with the increased demand for high power density and high-temperature operating environments, high Tg PCBs have become a key choice to ensure the reliability and heat resistance of the circuit board. High Tg PCBs are designed to operate under high-temperature and mechanical stress conditions, and their thermal stability, mechanical strength, and electrical properties are better than ordinary PCBs.

Next, this article will take you to explore the characteristics, advantages, application scenarios of high Tg PCB materials, and how to choose the right Tg Board to ensure the best performance and reliability for electronic devices. Let's get down to business!

What is High Tg PCB?

A high Tg PCB is a printed circuit board made using a material with a high glass transition temperature (Tg). The Tg value represents the temperature at which the PCB substrate material changes from a hard glass state to a soft rubber state. For standard FR4 materials, Tg values typically range from 130℃ to 140℃, while Tg values for high Tg PCBs reach 170°C or higher, and ultra-high Tg materials can even exceed 180℃. High Tg PCBs are designed to maintain their mechanical and electrical properties at high-temperatures without softening or failure. This makes them ideal for applications that operate in high-temperature environments or require lead-free welding processes.

High Tg FR4

FR4 is the most commonly used PCB substrate material and is usually composed of epoxy resin and glass fiber. High Tg FR4 is a specific type of High Tg PCB, mainly by changing the combination of resin formulation and glass fiber to improve its Tg value, High Tg FR4 indicates that this FR4 material has a higher glass transition temperature (usually greater than 170°C), more suitable for applications requiring high-temperature stability.

Understand Tg (Glass Transition Temperature)

Glass transition temperature (Tg) is a key characteristic of PCB materials, especially substrate materials such as FR4. As mentioned earlier, Tg refers to the temperature at which a material changes from a rigid glass state to a flexible rubber state. Below Tg values, the material remains hard and stable, providing the necessary mechanical strength for the PCB. When the temperature exceeds the Tg value, the material becomes softer and more prone to deformation, which can lead to problems such as plate warping, delamination or plating through hole (PTH) failure.

FR4 Tg materials are generally divided into three categories:

Standard Tg PCB (130°C-140°C) - suitable for general consumer electronics

High Tg PCB (170°C-180°C) - Suitable for high-temperature PCB applications

Ultra High Tg PCB (200°C+) - for extreme environments (e.g. aerospace, military, etc.)

Why Tg is Important?

Because the high Tg material can improve the reliability of the PCB in extreme environments, this makes it very suitable for multi-layer circuit boards and high power density applications.

The first is its dimensional stability, the expansion rate of high Tg PCB materials at high-temperatures is lower, and the probability of inter-layer dislocation and structural deformation will be reduced.

Secondly, it is its reliability of plated through holes, which can prevent PTH from cracking or delamination at high-temperatures and ensure the stability of the long-term use of the circuit board.

Third, it is its thermal stress resistance. This feature of Tg boards can effectively reduce thermal damage in applications that experience frequent temperature cycles, such as automotive and industrial equipment.

There is also its low coefficient of thermal expansion: the coefficient of thermal expansion of high Tg PCB is lower, and it can still maintain good dimensional stability in high-temperature environment.

The above characteristics also make high Tg PCB materials popular and widely used.

When Need to Use High Tg PCB?

How to choose the right Tg value?

The data in the above table is for your reference.

Materials Used in Manufacturing High Tg PCB

Common High Tg FR4 Materials

Conclusion

High Tg PCBs are ideal for high-temperature, high power density electronic systems. The use of high Tg PCB materials can ensure stable operation of the board in extreme environments.

Electronic products are constantly evolving, and the correct selection of Tg Board and PCB Tg grades is increasingly important for automotive, medical, aerospace, telecommunications and industrial electronics. Whether you are designing high power systems or lead-free welding applications, investing in high Tg PCBs will ensure that your products meet high reliability standards.