The TG value (glass transition temperature) in PCB board refers to the temperature at which the material changes from glass to rubber. Simply put, the TG value is the temperature at which the PCB material begins to soften and deform. TG in PCB board means temperature resistance. The higher the G point, the higher the temperature requirement when pressing the board, and the pressed board will become harder and brittle.

The higher the G value, the better the heat resistance of the board, especially in the lead-free tin-spraying process, high T is more commonly used.

The ordinary Tg of the board is above 130 degrees, High-Tg is generally greater than 170 degrees, and the medium-normal Tg is about greater than 150 degrees. The Tg of the substrate increases, and the heat resistance, moisture resistance, chemical resistance, and stability of the printed board will increase and improve.

The specific meaning of the TG value

Glass State: At a temperature below the TG value, the PCB material is in a hard and brittle glass state.

Rubbery State: At a temperature above the TG value, the PCB material becomes soft and elastic.

Relationship between TG value and PCB quality

TG value has a great influence on the performance and quality of PCB, which is specifically reflected in the following aspects:

Thermal stability

PCB materials with high TG value can withstand higher temperatures and have better thermal stability. This is especially important in high temperature environments or high power applications, such as: high frequency circuits, multilayer boards, high power, LEDs, automotive electronics.

Dimensional stability

PCB materials with higher TG value can better maintain dimensional stability and reduce thermal expansion and contraction at high temperatures. This helps to avoid solder joint cracking and circuit failure.

Mechanical properties

High TG value materials can maintain good mechanical properties such as strength and rigidity at high temperatures, reducing material softening and deformation caused by increased temperature.

Electrical properties

The electrical properties of PCB materials, such as dielectric constant and dielectric loss, may change when approaching or exceeding the TG value. Therefore, high TG value materials can maintain good electrical properties at higher temperatures.

Manufacturing process

During the manufacturing process, especially during the lamination and welding of multilayer boards, high TG values can improve the material's heat resistance and reduce the risk of interlayer separation and deformation.

How to choose TG value

General application: For general applications, FR4 materials with a TG value of around 130°C are usually sufficient.

High temperature and high performance applications: For applications with high temperature, high performance or high reliability requirements, such as aerospace, automotive electronics and high-frequency circuits, it is more appropriate to choose high TG materials with a TG value of more than 170°C.

TG value is an important parameter of PCB materials, which directly affects their thermal stability, dimensional stability, mechanical properties and electrical properties. Choosing the right TG value is crucial to ensure the quality and reliability of PCBs, especially in high temperature applications.