The Printed Circuit Boards (PCBs) are always susceptible to damage due to high temperatures. As the PCB designs are becoming compact, the power densities are rising gradually causing high temperatures since dielectrics and conductors dissipate heat. This high temperature can potentially cause serious damage to the delicate electronic components. However, there is one extreme solution to this problem. The solution is High-Temperature PCB manufacturing. High-Temperature PCBs are the PCBs with glass transition temperature (Tg) higher than 150° C. Yet manufacturing high-temperature printed circuit boards have multiple extreme considerations of material selection and board designs. This post focuses on the material selection criteria and available materials for High-Temperature PCB manufacturing.
What is a High-Temperature PCB?
High-temperature PCBs are the PCBs designed to withstand high temperatures. These PCBs are also known as High-Tg PCBs. They are used in high-temperature operations.
However, these PCBs require special materials to withstand such a high temperature of 150 to 170°C. The next section introduces you to material selection criteria and suitable material for High-Tg PCBs.
What is the Material Selection Criteria for High-Tg PCBs?
The material consideration for High-Tg PCBs follows a simple thumb rule. According to the thumb rule, if the operating temperature is approximately 25°C below the glass transition temperature then the PCB material is under a gradually increasing thermal load. This means, if the operating temperature is expected to rise to 130°C then the board must be manufactured of a high Tg material. The material for high-temperature PCBs must be chosen with the following consideration.
- Flame Resistance
- Chemical Resistance
- Low Smoke and Ash Formation
There are a few proven materials that are suited for High-Tg PCB manufacturing.
What are the Materials Used for Manufacturing High-Tg PCBs?
The materials used for manufacturing High-Tg PCBs are flame-resistant materials. Glass epoxy resins possess flame-resistant properties. Therefore, the polymers and composites comprising epoxy resins are preferred for High-Tg PCB manufacturing.
The list of materials used for High-Tg manufacturing is detailed as follows.
- FR4: FR4 stands for glass-reinforced epoxy laminate material. It is a NEMA grade designation for epoxy fiber-glass composites. Here, FR stands for Flame Retardant. This FR4 material is tested for flame-resistant properties under UL94V-0 standards. The material offers electrical resistance in both dry and wet conditions, therefore the heat dissipation due to dielectric and conductors is resisted in FR4 materials.
There is a range of FR4 standard materials developed by Isola Group that is commonly used for this type of PCB manufacturing. The list of Isola Group FR4 materials is as follows.
- IS410: IS410 is FR4 laminate and prepreg material that can sustain 180°C Tg. It is suitable for multiple thermal excursions and it has cleared the 6X solder test under 288°C temperature. It is also suitable for lead-free soldering in high-temperature PCB manufacturing.
- IS420: IS420 is a high-performance multifunctional epoxy resin. It offers enhanced thermal performance and has low expansion rates as compared to regular FR4 materials. This material blocks UV radiations, therefore it is compatible with Automated Optical Inspections (AOI).
- G200: G200 is a combination of epoxy resin and Bismaleimide/Triazine (BT). It offers high thermal resistance, high mechanical strength, and absolute electrical performance. It is suitable for multi-layered Printed wiring boards.
However, along with these commonly used High-Tg materials, S1000, ITEQ IT-180A, ARLON 85N, etc are some FR4 materials from varying brands that are suited for High-Tg PCB manufacturing. It is also important to understand that along with the proper selection of material, High-Tg PCB manufacturing takes an understanding of the thermal design process. Therefore, this process must be performed by experts. Rigiflex Technology, Inc is a PCB manufacturing company that has experienced PCB design and manufacturing staff. The company has been offering PCB manufacturing services for 25 years. The experts at the company will work with you to understand your thermal requirements, before helping you choose the right FR4 material for the application.
