Using Vacuum Reflow Processing to Eliminate Solder Joint Voiding and Optimize Thermal Fatigue Reliability
Authors: Richard Coyle, Dave Hillman, Charmaine Johnson, Keith Howell, Richard Popowich, David Heller, Richard Parker, Jörg Trodler, Adam Murling Company: Nokia Bell Labs, Collins Aerospace, Nihon Superior Co., Ltd., Heller Industries, iNEMI, Heraeus, Indium Corp. Date Published: 1/30/2019
Abstract: A test program was developed to evaluate the effectiveness of vacuum reflow processing on solder joint voiding and subsequent thermal cycling performance. Area array package test vehicles were assembled using conventional reflow processing and a solder paste that generated substantial void content in the solder joints. Half of the population of test vehicles then were re-processed (reflowed) using vacuum reflow system. Transmission x-ray inspection showed a significant reduction in solder voiding after vacuum processing. The solder attachment reliability of the conventional and vacuum reflowed test vehicles was characterized and compared using two different accelerated thermal cycling profiles. The thermal cycling results are discussed in terms of the general impact of voiding on solder thermal fatigue reliability, results from the open literature, and the evolving industry standards for solder voiding. Recommendations are made for further work based on other void reduction methods and additional reliability studies.