Impact of Process Control in Pb-Free to SnPb Reballing Techniques Part 1: Control of Thermal Exposure
Authors: Joelle Arnold, Seth Binfield, Steph Gulbrandsen, and Dr. Nathan Blattau Company: DfR Solutions Date Published: 5/13/2014
ICSR (Soldering and Reliability)
Abstract: For high reliability industries that have not transitioned to Pb-free solders, reballing of Pb-free ball grid array (BGA) type components is the preferred solution to the obsolescence of Commercial Off-The-Shelf (COTS) BGAs manufactured with SnPb solder. This work focuses on observed differences in reballing techniques, process control of thermal exposure by reballers, and resulting differences in reballed components. Five different reballers employing distinct techniques were audited during reballing of dummy chip scale packages (CSPs) and large BGAs. Dressed bond pads of an active flip chip were examined, and assembled dummy packages were cross sectioned to measure the intermetallic compound (IMC). Results indicate that the processes that achieved the most uniform pads during ball removal formed IMCs that were more sensitive to thermal exposure during ball attach. Methodology and process controls during reballing can have notable effects on the microstructure of solder joints formed at final assembly, and their eventual reliability in the field.