Reliable microvias in HDI PCB

One challenge for High Density Interconnect (HDI) PCB development, is to fabricate reliable microvias, especially for stacked microvias, without resulting in incomplete filling, dimples, or voids in the copper plating process. Incomplete copper filling increases the stress levels in microvias and hence decreases microvia fatigue life. As for voids, different voiding conditions, such as different void sizes, shapes, and locations result in different effects on microvia reliability. Small voids of a spherical shape lightly increase the microvia fatigue life, but extreme voiding conditions greatly reduce the duration of microvias.