Selective Soldering Design for Reliability Using a Novel Test Board and Sir Test Method
Authors: Mike Bixenman, David Lober, Mark McMeen, Denis Jean and Joe Clure Company: KYZEN Corporation, STI Electronics, KESTER Inc. and KURTZ ERSA Date Published: 10/14/2018
Abstract: The reliability of selectively soldered PCBs is a product of a complex interaction of several factors determined by the PCB design layout, flux, selective soldering machine, cleanliness, and end-user environment. Selective solder flux must be present and active to achieve reliable solder connections. The precision of flux transferred to the soldering area is critical to prevent leakage currents and dendritic growth on products used in harsh operating environments. Surface Insulation Resistance (SIR) is an effective method for predicting long-term failure mechanisms and as a predictive tool for service life reliability. SIR is a quantitative test method to evaluate electrochemical reactions from ionic contamination following the selective soldering process. A custom designed mixed technology test board, used for this study, has a connector next to surface mount components. The reliability of the soldering process will be tested using SIR IPC-TM 2.3.7 test method. The purpose of this research is to develop a test method designed to evaluate the electrochemical reliability of the selective soldering process at the assembly site. We will examine the impact of four (4) solder fluxes for flux spread and tackiness. Following these tests, the boards will be SIR tested at 40°C, 85% RH for 168 hours.