The Combined Effect of Shock Impacts and Operational Power Cycles on the Reliability of Handheld Device Component Board Interconnections
A compact high-density test board has been subjected to combinations of power cycling and shock impact loads. The test board was designed to replicate both the mechanical shock impact response and the thermomechanical response of a commercial handheld device component board under product- and board-level tests. The power cycling loading affected the microstructure of the solder interconnections by (1) enhancing the growth of interfacial intermetallic compound layers and (2) driving the coalescence of intermetallic particles inside the solder bulk. These microstructural changes initially improved drop test reliability, but longer exposure time caused the drop reliability to deteriorate. The lifetimes and failure modes of the test boards were found to be similar in concurrent and consecutive test combinations. Furthermore, the lifetime trend of the consecutive power cycling and drop tests was found to be the same in board- and product-level tests. This confirms that product-level reliability can be assessed with board-level tests.