Development of Printed Circuit Boards with High Thermal Conductivity and Low Thermal Expansion by Applying Cu-Mo Composite Materials

Abstract

In recent years, electronic devices are strongly required to be smaller, lighter, and more powerful. As a result, mounted components have become smaller, more powerful, and denser, and the heat generation density on printed circuit boards (PCBs) has increased. Since temperature rise of components can lead to component failure, efficient heat removal from the generated heat has become an urgent issue. Since general PCBs have low thermal conductivity, when high heat dissipation is required, methods to increase the thermal conductivity of PCBs have been employed by increasing the copper (Cu) content in the PCB or by placing an aluminum (Al) alloy in the inner layer. However, while Cu and Al have high thermal conductivity, they also have high coefficients of thermal expansion (CTE) and young’s modulus, and the CTE of a PCB with increased thermal conductivity using these materials is high. If the thermal expansion difference between the PCB and mounted components is large, reliability against heat cycles cannot be obtained. Thus, it is difficult to achieve both heat dissipation and low thermal expansion in current PCBs. Therefore, we have focused on copper-molybdenum (Cu-Mo) composite materials with high thermal conductivity and high elastic modulus, but with low thermal expansion. We have been utilizing Cu-Mo for the development of our PCBs and fabricated multilayered Cu-Mo composite PCBs; therefore, this report will focus on the results regarding thermal characterization of prototype PCBs.