Fabrication of Copper Compliant Iinterconnects on a Printed Circuit Board: An Additive Approach

The need to increase the power density in electronic devices is being limited by the reliability of power devices and its components. To counter this problem, devices will need to have nonconventional designs and features that can help mitigate thermal and mechanical stress concerns, in order to improve failure rates at critical locations within power devices and packages. A major problem plaguing power densification arises from the reliability of the device due to thermomechanical stresses and strains at interfaces that are amplified in harsh environment electronics such as in electric vehicle applications, where temperature extremes are common. One solution to enabling longer interconnect life lies in compliant interconnects, wherein various compliant geometries using photolithography-based approaches to fabricate suspended structures for allowing deflection between chip and substrate. These features reduce stress on the interconnection itself, resulting in improved lifetimes, particularly in solder joints. Yet these structures usually come at a cost of lateral many additional processing steps during interconnect fabrication. In this work, we present an additive approach to fabricate copper-plated compliant interconnects directly on printed circuit boards (PCBs). This approach can accomplish similar thermomechanical stress alleviation to formerly reported methods, but with fewer process steps, and new geometry availability. This work reports the fabrication procedure, process engineering and characterization in addition to the compliance evaluation for a semi-subtractive structure manufacturing process enabled through a novel additive manufacturing methodology.