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 requirement 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 glass state. Standard Tg stays above 130℃ while
high Tg 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 substance rises, 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,
plated hole may suffer from breakage or components will get damaged. Therefore, 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

High-frequency circuits call for PCB material with high dielectric constant and low dielectric loss. Besides,
insulation resistance, dielectric strength and Arc resistance should be compatible with product requirement.