Materials Characterization and Model of PCB Thermal Expansion for Laminates With Various Copper Densities and Thicknesses

The SEMATECH/SEMI roadmap forecasts increased density requirements for printed circuit board manufacturing to accommodate smaller form factor interconnects, increased pin counts, and routing densities on a range of PCB sizes and thicknesses. As a result, the effect of materials. thermal expansion properties may further impact the structural or physical integrity and subsequent electrical properties for high speed and thermal management requirements. This study demonstrated that various sample coupons selected from PCB boards with different amounts of copper showed a corresponding coefficient of thermal expansion (CTE) correlation in the Z-axis (CTEZ) and can be modeled using a constitutive equation. Moreover, samples were further evaluated from the effect of increasing temperature and showed that the CTE indeed affects copper-interconnect physical structures such as copper vias and barrels in terms of elongation or strain.