How to Select Material for Your PCBs from Cost and Reliability Considerations

Material, usually substrate material as far as PCB (Printed Circuit Board) is concerned, plays a core role in PCB since it carries its leading functions and properties. Besides, PCB material allows PCBs to conform to some high and special requirements set by the products or projects they’ll work for. Furthermore, it is beneficial to reduce cost and improve products’ reliability when optimal material is selected.

Elements to be Considered in PCB Material Selection

• Glass Transition Temperature (Tg)

Tg refers to the temperature at which material is converted into a glass state. Standard Tg stays above 130℃ while high Tg is above 170℃ and mid-Tg above 150℃.

When it comes to material for PCBs, high Tg should be picked, which should be higher than the working temperature current runs.

• Coefficient of Thermal Expansion (CTE)

As the temperature of the substance rises, the substance will suffer from expansion or shrinking. When it comes to PCB fabrication, since CTEs in X, Y and thickness are different, PCB will tend to become deformed. Furthermore, the plated hole may suffer from breakage or components will get damaged. Therefore, the CTE of substrate material should be sufficiently low.

• Heat Resistance

PCB is required to be heat resistant. Generally speaking, PCBs should feature heat resistance of 250℃/50s, which also works on material.

• Flatness

PCB is required to feature excellent flatness. As far as SMT assembly is concerned, PCB is required to feature warpage lower than 0.0075mm/mm.

• Electrical Performance