LEAD-FREE SOLDER DURABILITYTESTING AT ACCELERATED THERMAL EXCURSIONS FOR QFN AND DFN PACKAGE INTERCONNECTS

摘要

Hamilton Sundstrand’s (HS) subsidiary in Nordlingen, Germany is using a synchronous step down switching regulator from Linear Technology in a low voltage power supply (LVPS) application. This device is packaged in a 32 pin Quad Flat No-lead (QFN32) package. During thermal cycling tests there have been numerous instances of solder joint failures associated with this device. An evaluation of the PWB layout for this device and the solder stencil design has revealed deviations from the design features recommended by QFN32 manufacturers. Further, failure data shows that the use of conformal coating accelerates the failure mechanism.