Effects of Voiding on the Degradation of Microvias in High Density Interconnect Printed Circuit Boards Under Thermomechanical Stresses

Printed circuit boards (PCBs) are made of several dielectric layers stacked on top of each other. These layers could be standard PCB core board or high density interconnect (HDI) layers. Microvias allow signal and power transmission between the HDI layers of the PCBs. The presence of voiding in filled microvias has raised concerns in industry about how they affect the degradation of microvias during the life cycle of the product. Voids can vary widely in shape and size and have been observed in both stacked and single-level microvias. This paper examines whether the presence of voids alone is responsible for the degradation of microvias, or if parameters such as void size and void shape have an influence as well. Both voided and nonvoided microvias were tested together using liquid-to-liquid thermal shock as the accelerated testing method to understand their different behaviors under thermomechanical stresses.