PCB manufacturers who have been in the industry for a while understand that every board type has unique mechanical, thermal, and chemical properties. High TG PCBs are ideal for applications that operate at high temperatures, typically 170°C or above.
These PCBs must be able to withstand extreme temperatures and possess exceptional resistance to thermal stress. In this article, we will delve into what makes high TG PCBs beneficial for certain types of electronics.
When it comes to epoxy materials used for PCB manufacturing, one of the most critical mechanical properties is glass transition temperature (Tg). Tg refers to the temperature at which the polymer or glass changes from a solid to a rubbery state, and it is an essential quality for PCBs that will be exposed to high operating temperatures. Here are some of the benefits that come with using high Tg laminates for PCBs:
Enhanced durability: Compared to standard FR-4 boards, high Tg PCBs have a longer layering time and can withstand higher temperatures before delamination occurs, making them more durable. Reduced thermal expansion: High Tg PCBs have low thermal expansion levels, making them more dimensionally stable and ideal for microelectronics manufacturing. Excellent high-temperature resistance: High Tg PCBs can withstand high thermal loads without losing their functionality due to thermal decomposition (Td). It's worth noting that different materials have varying Tg values and characteristics that make them suitable for high Tg PCB production. Here are some examples of materials used to produce high Tg PCBs:
Isola 370HR
Ventek VT47
IT180
Panasonic R1755V/R1650V
Kingboard KB6167
NP-175TL
ITEQ-IT-180A
Shengyi S1000-2
Other types of materials may also be suitable for high Tg PCB production. PCB manufacturers must carefully choose the appropriate material based on the intended application and operating environment.
When it comes to high TG PCB materials, their natural properties are crucial. However, manufacturers are more interested in the characteristics that their high TG PCBs should have. Here are some of the characteristics:
High heat resistance. High TG panels retain their functionality even after short exposure to direct flame. They should not ignite after a short exposure of approximately 10 seconds.
High plated through hole (PTH) reliability. Continuity of plated material is critical for optimal PCB performance, especially for multilayer PCBs.
Low Z-axis coefficient of thermal expansion (CTE). A low CTE value means a lower risk of fatal thermal expansion and better PTH reliability. A low CTE is usually associated with a high Td value.
High thermal shock resistance. TG boards are less susceptible to this stress caused by rapid, sudden changes in ambient temperature.
Excellent thermal fatigue resistance. TG boards are less prone to permanent change in PCB structure and function caused by prolonged exposure to unfavorable temperature conditions.
Other important properties of the TG material are its ability to dissipate heat adequately and its suitability for high-density designs. Three ways electronics dissipate heat are through conduction, radiation, and convection. TG PCBs can also stabilize the operating conditions within the equipment, extend the service life of circuit boards and electronic products, and reduce the risk of short circuits and other common modes of PCB failure. Additionally, TG materials help solve heat dissipation problems in high-density designs and are less prone to adverse effects for multilayer and HDI PCB.
In summary, high TG PCBs have several advantages, including stability, suitability for high-density designs, and use in multilayer and HDI PCBs. With their excellent mechanical and chemical resistance, they can extend the service life of circuit boards and electronic products, while reducing the risk of short circuits and other common modes of PCB failure.
If you anticipate that the thermal load of your PCB will exceed 25°C or that the device may operate with an internal temperature above 130°C, it is recommended to replace your FR-4 laminate with a high TG board. These boards have higher heat resistance, allowing them to withstand direct exposure to flame for short periods of time without losing functionality. Additionally, high TG materials are required for RoHS PCBs, which are lead-free solder boards that require higher temperature levels to melt and flow.
While replacing all FR-4 with high TG plates can be costly, there are several industries where high TG boards are necessary:
Metalworking industries, including CNC machining, where computer-controlled machines require microcontrollers with high TG boards to withstand temperature fluctuations during operation.
Engine efficiency-related electronics, which need to handle high temperature loads generated at higher RPM during run time.
WiFi boosters, which can fail after hours of operation without proper cooling, but high TG materials can help.
Embedded computer systems, where computer processors, memory, and other components are under heavy load, and high TG materials are better equipped to handle prolonged exposure.
Low-cost programmable logic controllers (PLCs), industrial computers suitable for controlling input devices, which require TG materials for extra reliability.
RFID gateway and portal applications, which track goods in motion and require TG materials due to the high radio frequency technology involved.
These are just a few examples of where high TG materials can be used. Ultimately, it is important to consider the expected thermal load of your PCB and the potential operating conditions to determine if a high TG board is necessary for your application.