Effect of Thermal Treatment on the Microstructure, Properties, and Reliability of Lead-Free Bismuth Containing Solder AlloysAuthors: André M. Delhaise, David Hillman, Polina Snugovsky, Jeff Kennedy, Ross Wilcoxon, David Adams, Stephan Meschter, Joseph Juarez, Milea Kammer, Ivan Straznicky, Doug D. Perovic
Company: Celestica, Department of Materials Science & Engineering at University of Toronto, Rockwell-Collins, BAE Systems, Honeywell Aerospace, Curtiss-Wright
Date Published: 9/17/2017 Conference: SMTA International
In our previous work, the creep properties of Violet (Sn- 2.25Ag-0.5Cu-6.0Bi) and SAC 305 were evaluated both before and after the application of an above-solvus thermal treatment. It was shown that the creep resistance of Violet was significantly improved after this treatment while the SAC 305 was unaffected. In this work, the aforementioned treatment (125oC for either 24h or 48h) was performed on a series of PCBs that had been assembled using SAC 305 or Violet. After the thermal treatment, boards underwent ATC at one of two thermal profiles: -55oC to 125oC or -40oC to 70oC, per the IPC 9701 specification. Statistical analysis was conducted to evaluate the efficacy of the thermal treatment on improving solder joint reliability. Physical failure analysis was also performed to investigate the evolution of the microstructure and determine the combined effects of the treatment and ATC on the failure mode.
heat treatment, solder, ATC, reliability
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