Thermal Expansion Control of Printed Circuit Boards Using Copper-Molybdenum Composite Materials

In recent years, there has been a strong demand for electronic devices to be miniaturized, lightweight, and high-performing. As a result, there has been progress in downsizing and increasing the output of components, as well as high-density mounting of components, leading to an increase in heat generation on the printed circuit board (PCB). Since rising component temperatures can lead to component failure, efficient heat removal is an urgent issue. Damage caused by thermal stress is also a major problem. Repeated temperature changes can cause fractures or cracks inside the PCB or in the joints between the PCB and mounted components, resulting in poor conduction. The main factor contributing to this thermal stress is the mismatch in coefficients of thermal expansion (CTE) between materials. To ensure the reliability of PCBs with mounted components, it is necessary to reduce the thermal stress that occurs between the PCB and the components. We have focused on Cu-Mo composite materials with high thermal conductivity, high elastic modulus, and low thermal expansion, and have developed PCBs with low thermal expansion and high heat dissipation by utilizing these materials. In this study, we concentrated on the low thermal expansion of PCBs made with Cu-Mo composite materials and demonstrated the possibility of controlling the CTE of PCBs by adjusting the volume content of the Cu-Mo composite in the inner layer.