Reliability of Stacked Microvia

The Printed Circuit Board industry has seen a steady reduction in pitch from 1.0mm to 0.4mm; a segment of the industry is even using or considering a 0.25mm pitch. This has increased the use of stacked microvias in these designs. The process of stacking microvias has been practiced for several years in handheld devices; however, the devices generally do not operate in harsh conditions. Type 1 and Type 2 microvias have been tested over the years and have been found to be very reliable. We do not have enough test data for 3 and 4 stack microvias when placed on and off buried via. The main objective of this study was to understand the reliability of 3 and 4 stack microvias placed on and off a buried via.