High Tg PCB: Superior Heat Resistance for Advanced Application

Tg represents the temperature range where the base material of a PCB transitions from a solid, rigid, and glassy state to a rubbery state. It is important to select a PCB with a Tg value at least 20-25 degrees Celsius higher than the expected operating temperature of the device. This ensures the stability of the board and prevents adverse effects during the manufacturing process. High Tg PCBs have excellent thermal resistance, mechanical strength, and chemical stability, making them essential for reliable operation in high-density electronic applications.

What is high TG PCB?

A high Tg PCB refers to a printed circuit board with a high glass transition temperature (Tg). Tg is the temperature at which the base material of the PCB changes from a solid and rigid state to a more rubbery state. That is to say, Tg is a mechanical property that designates glass transition temperature, that is, the highest temperature at which the substrate remains rigid.

A normal PCB FR4-Tg is 130-140 degrees, the medium Tg is greater than 150-160 degrees, and high Tg is greater than 170 degrees. By using materials with higher Tg values, high-Tg PCBs can handle elevated temperatures without warping, delamination, or other thermal-related issues. This makes them suitable for applications where heat dissipation and thermal management are critical, ensuring the longevity and performance of electronic components on the board.

Properties of high Tg PCB

High-Tg PCBs possess several key properties that make them advantageous for some applications.

• High Temperature Resistance: High Tg PCBs are engineered to withstand elevated temperatures without losing their structural integrity. They exhibit excellent heat resistance, preventing issues such as warping or delamination during operation.

• Enhanced Mechanical Strength: These PCBs offer improved mechanical stability, ensuring they can endure the stress and strain of assembly processes, vibrations, and thermal cycling. Their robust construction enhances the reliability and longevity of the board.

• Improved Signal Integrity: High Tg PCBs provide better signal transmission and reduced signal loss, particularly in high-frequency applications. Their superior electrical properties contribute to enhanced signal integrity and minimize signal distortion.

• Reliable Thermal Management: Due to their ability to handle higher temperatures, high-Tg PCBs facilitate efficient heat dissipation, preventing overheating of sensitive electronic components. This property is crucial for maintaining optimal performance and preventing thermal-related failures.

• Chemical Resistance: High Tg PCBs exhibit improved resistance to chemicals and solvents, making them more durable in harsh environments. This property ensures their long-term functionality and reliability even in challenging operating conditions.

• Design Flexibility: High Tg PCBs can be manufactured with multiple layers, enabling the creation of complex circuitry and supporting advanced technologies such as high-density interconnects and fine pitch components.

Advantages of high Tg PCB

Perfect for Multilayer and HDI PCBs

Multilayer and High-Density Interconnect PCBs, known for their compact size and densely packed circuits, tend to produce a lot of heat. High Tg PCBs are ideal for these types of boards because they can handle the increased heat dissipation without compromising the manufacturing process. This ensures that the PCBs are reliable and durable, even in demanding applications.

Enhanced Stability with High Tg PCB Substrates

Increasing the Tg, or glass transition temperature, of a PCB substrate can significantly boost the board's performance. A higher Tg means better resistance to heat, chemicals, and moisture, which enhances the overall stability of the device. This improvement is crucial for electronics that need to operate reliably under stressful conditions.

Handling High Power Density

Devices that generate a lot of heat due to high power density can benefit from high Tg PCBs. These boards are designed to manage heat effectively, ensuring that the device remains functional and safe. Instead of using a larger PCB to dissipate heat, which can change the design and power requirements, a high Tg PCB offers a more efficient solution.

Applications of High Tg PCB

With the rapid growth of the electronics industry, high Tg materials have become widely utilized in various applications such as computers, communication equipment, precision instruments, and more. As electronic products strive for increased functionality and multilayer development, PCB substrate materials require higher heat resistance as a prerequisite. The emergence and advancement of high-density mounting technologies like SMT and CMT have made PCBs increasingly reliant on substrates with superior heat resistance, particularly in cases involving thinning, small apertures, and fine wiring.

Furthermore, high Tg materials have gained popularity in the LED lighting industry. LEDs generate more heat compared to standard electronic components. While metal core PCBs, such as aluminum PCBs, offer excellent heat dissipation, the same structural design using FR-4 boards is much more cost-effective.

Tg for PCBs

For PCBs, Tg corresponds to the temperature at which glass fibers become amorphous during lamination of layers of different materials under high temperature and pressure. It is not the maximum operating temperature of the PCB, but the temperature that the PCBA can withstand for a short time before it deteriorates.

Copper clad laminate (FR4) with inner layer imaging is the most commonly used material in PCB production, but it requires the use of PREPRG layers, which are laminated for rigidity. The heat required for PREPRG rigidity must be applied without exceeding the FR4 Tg to maintain PCB stability. Standard FR4 Tg is between 130 – 140°C, with a median Tg of 150°C and a high Tg greater than 170°C. In the hot state, high Tg FR4 will have better mechanical and chemical resistance to heat and moisture than standard FR4.

Tg for PCB Assembly

Temperature fluctuations can significantly impact the performance and reliability of PCB assemblies (PCBAs). Materials used in PCBs expand with rising temperatures, causing mechanical stress and potential micro-cracks. These micro-cracks often go undetected during electrical tests conducted after production. Without proper detection, failures may occur during assembly or even in the final product, resulting in reliability issues. Additionally, the shift towards lead-free soldering alloys, as mandated by RoHS directives, has increased the soldering temperature for PCBs. To ensure the integrity of PCBAs, it is crucial to choose a PCB with appropriate mechanical characteristics, especially an adequate Tg that matches the selected soldering process.

When do you need a high Tg PCB?

If you printed circuit board can not bear a thermal load no greater than 25 degrees centigrade below the Tg, you will need a high Tg PCB for your applications. If the circuit has to operate at 150°C then a material with a Tg greater than or equal to 180°C is preferred. Such requirements are typically seen in  and space applications. What’s more, it also make sure safety with high Tg PCB if your product is operating in the 130 degrees centigrade range or higher. Needless to say, the main reason for high Tg PCB is the movement to RoHS PCB. So there are more and more PCB industries moving toward high Tg materials as the lead-free solder to flow needs higher temperatures.

High Tg materials used at VictoryPCB

The difference between standard FR-4 and high Tg materials is that high Tg PCB substrates will perform better in terms of mechanical strength, dimensional stability, adhesion, water absorption and thermal management. If you have any other questions, please contact us and our pcb expert will help choose the right materials for high tg pcb.