PoP: 2 Times the BGAs, 2 Times the Problems?

摘要

WITH BOARD AREA often at a premium in today's sophisticated and high-performance electronics, using the third dimension of height to enable greater device functionality is ever more attractive. In particular, package-on-package (PoP) devices have been around for years and are popular for this purpose. From an x-ray inspection point-of-view, the most comman POPs can be considered as two BGAs stacked on top of each other. Therefore, the real and "virtual" issues associated with BGAs, as mentioned in previous columns, also come into play for these devices.