Solderability And Oxide Thickness Measurement To Determine Long Term Storage Of BGA And QFP
Authors: Rama Hegde, Ph.D. Terry Burnette and Andrew Mawer Company: Freescale Semiconductor, Inc. Date Published: 10/13/2013
Abstract: This paper will report on the oxide thickness and solderability testing for evaluation of ball grid array (BGA) and quad flat package (QFP) device parts following long term storage. A study was undertaken to assess oxide growth and solderability versus storage on multiple package types and lead finishes (SnPb and Pb-free LQFPs, SnPb and Pb-free BGAs) following various aging conditions. The oxide thickness on plated leads and on BGA spheres was determined by Auger Electron Spectroscopy (AES) depth profiling measurements. The solderability was assessed using the industry standard surface mount process simulation test [1, 2]. For the solderability testing, these devices were subjected to either a 125°C bake in air or 8 hours of steam aging as prescribed by the standards. The steam aging resulted in measurable oxide growth (thickness and composition) with respect to the bake condition. A good correlation was found between the solderability and the oxide thickness on BGAs and LQFPs. Maximum oxide thickness below ~ 70Å on samples resulted in good solderability.
oxide thickness, solderability, BGAs, QFPs, MSL bake, steam aging, Auger electron spectroscopy (AES), long term storage, end-of-life (EOL)