Design Configuration
Vertical alignment choices determine the spatial relationship between microvias on adjacent layers in a high-density circuit design. The comparison of stacked vs staggered microvias involves balancing the need for routing space against the requirements for mechanical reliability. Placement of one via directly on top of another saves horizontal area but creates a continuous column of copper through the layers.
Interconnect Reliability
Mechanical stress tends to concentrate at the interfaces of vertically aligned copper structures during thermal expansion. Using stacked vs staggered microvias changes the failure profile as the offset version distributes the stress across a wider area of the laminate. Reliability data indicate that the staggered approach is more resistant to barrel cracking in high-reliability applications.
Boards destined for extreme temperature fluctuations usually benefit from the increased surface area for bonding that the offset placement provides. Via placement impacts the long-term electrical continuity of the via chain.
Routing Efficiency
Designers select the vertical arrangement based on the density of the component pinouts and the available layers. Choosing stacked vs staggered microvias affects the ease with which traces can pass between the vias to reach other parts of the board. Stacked configurations are often necessary for the most compact ball grid array footprints.
Production costs remain similar for both styles.
