In this post, you will find the PCB TG definition, a brief comparison of TG 180 PCBs, TG 150 PCBs, TG 140 PCBs, and get to know a high TG PCB manufacturer PCB HERO

What is PCB TG

When the temperature gets high enough, the PCB substrate that consists of glass fiber turns soft. The critical temperature at which the PCB substrate turns from the solid-state to the liquid state is the PCB TG (glass transition temperature). In other words, PCB TG is the highest temperature at which the PCB FR4 substrate keeps rigid.

According to the different TG values, we classify FR4 PCBs into normal TG PCBs, medium TG PCBs, and high TG PCBs: (DSC)

The higher TG of the PCB laminates, the higher the temperature range that the FR4 PCB can properly work in. When the PCB temperature goes beyond the glass transition point, the PCB turns soft and deforms. In this case, the PCB mechanical and electrical performances worsen, and the circuit board becomes unreliable.

TG 180 PCB vs TG 150 PCB vs TG 140 PCB

The PCB HERO editor chooses Ventec's three laminates to make a comparison between TG 180 PCB, TG 150 PCB, and TG 140 PCB.

• The high TG FR4 laminate VT-47: TG 180℃, 5% weight loss Td 355℃, total expansion Z-axis CTE 2.3%
• The medium TG FR4 laminate VT-42S: TG 150℃, 5% weight loss Td 315℃, total expansion Z-axis CTE 3.75%
• The normal TG FR4 laminate VT-42: TG 140℃, 5% weight loss Td 310℃, total expansion Z-axis CTE 3.75%

As you can see, even the TG 140 PCB made of VT-42 laminates has a 5% weight loss Td value of 310℃, and the reflow soldering temperature range during the lead-free PCB assembly is 240℃~270℃. Why is TG 140 PCB not used for lead-free products? The reason is that, during the 240℃~270℃ lead-free reflow soldering process, normal TG PCBs usually lose 1.5% to 3% of resin weight. The lost resin weight may reduce the PCB reliability or even lead to soldering defects.

Therefore, most of the products that require lead-free assembly apply TG 170 and TG 180 PCBs.

Besides, we prefer PCBs to have a small coefficient of thermal expansion (CTE). TG 180 PCBs usually have a smaller CTE than TG 150 PCBs, and TG 150 PCBs usually have a smaller CTE than TG 140 PCBs. But it depends, and you should check the PCB laminate specifications.

Is the PCB TG Higher the Better?

From the above, you can understand what the PCB TG is and know that a PCB can't work properly when temperatures go beyond its TG. Here is a question: is the PCB TG higher, the better for the PCB to be?

The answer is yes and no.

YES - high TG means high-temperature resistance and high stability of the PCB. Especially when the PCB absorbs moisture and the temperature gets high, compared with a normal TG PCB, a high TG PCB has better performances in mechanical strength, stability, adhesion, water absorption, and thermal decomposition.

Products tend to be smaller, finer, thinner, and the PCB working temperature gets higher. Especially, lead-free assembly temperatures are about 20℃ higher than tin-lead soldering. A higher TG should be better.

NO - it is more difficult to produce high TG PCBs because of the higher lamination temperatures. And after the high-temperature lamination, high TG PCBs are more hard and brittle than normal TG PCBs. Compared with normal TG PCBs, it is more difficult for mechanical drilling on high TG PCBs.

Though it is more difficult to manufacture high TG PCBs, many PCB designers and product managers choose high TG PCBs for high-power devices because of their good thermal performances.

It should also be noted that high TG PCBs usually have more than 10 layers. And high-end FR4 laminates have high TG and high Td (thermal decomposition temperature for PCB resin to lose 5% weight).

Where to Order TG 180 PCB, TG 150 PCB, and TG 140 PCB Manufacturing and Assembly?

You can order TG 180 PCB, TG 150 PCB, and TG 140 PCB from PCB HERO. PCB HERO is an advanced TG PCB manufacturer founded in 1999 with three large PCB and PCBA manufacturing bases. You can order PCB manufacturing, PCB assembly, and electronic components all together by registering online to get a quote or sending an inquiry email to sales@pcb-hero.com.

• PCB HERO provides 1 to 56 layers of high/medium/normal TG PCB manufacturing and assembly to clients around the globe.
• Provide one-stop high TG PCB manufacturing from prototyping to bulk production, such as TG 170℃, TG 180℃, TG 185℃.
• Strict quality control. High TG PCB manufacturing and assembly are run under ISO quality management.
• High-quality standards. High TG PCB assembly follows IPC-A-600 Class 2 and 3 standards.
• Offer one-on-one engineering support to assist customers from designing PCB, choosing materials to PCB manufacturing and assembly.
• Free electronic components procurement services. All components are traceable and at possibly the lowest prices in the world.

Apart from FR4 PCBs of any TG, you can order ceramic PCBs, PTFE PCBs, rigid-flex PCBs, FPCs, aluminum PCBs, etc. The product delivery is fast. You are welcome to get an instant quote now.