H.A.L.T. TEST VEHICLE FOR LEAD FREE SURFACE FINISH AND SOLDER PASTE SELECTION
Author: Tim Murphy Company: Thomson Inc. Date Published: 9/24/2006
Abstract: Thomson has developed a test vehicle and protocol to enable our engineers and management decision makers to easily measure and compare the often elusive, interactions between surface finish, paste flux and solder alloy. This thermo-mechanical test method measures the average energy required to fracture SMT solder joints using nine, (9) different strain conditions. The ease of replication and simple test geometry allows practical multifactor experiments to be conducted on paste alloys and their flux vehicle. The method permits measurement of thermal stability, packaging and shelf life studies on PCB finishes and allows measurement of their complex interaction with paste alloys, i.e. wetting, fillet formation, intermetallic phases distribution and, alloy dilution. Data presented in this paper has expanded upon our earlier work now including evaluation of multiple suppliers of Immersion silver & tin coatings, OSP, ENIG and Lead free HASL. Additional reliability data on 3% & 4% SAC alloy is presented along with comparisons to non silver bearing paste alloys; SnCuNi and SnZn.