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SAC Aging 2

Idea/Definition Information
Summary: 

There is evidence that the ATC performance of SAC solders is affected by thermal preconditioning or aging.  This project will use an existing test board design and component(s) to facilitate the further understanding of this phenomenon, and attempt to relate ATC performance to microstructural changes that occur during aging.  Baseline microstructural characterization will be performed on ambient (no age) and aged samples. Failure mode analysis and characterization will be performed on ATC samples to determine extent of microstructural evolution and impact on final failure.

If you are interested in this project and would like to subscribe to the project mailing list, please click here (members only) or email the project facilitator, Robert Smith - smitty@HDPug,org

Background: 

There is some evidence that the ATC performance of SAC solders tests is degraded by thermal preconditioning or aging

  • Multiple HDPUG Tests: SAC Acceleration Factors, Mild Acceleration Test, and SAC Aging Test
  • CALCE Data (limited public)
Problem: 
  • The current HDPUG SAC Aging work using bulk solder samples showed a correlation between SAC solder properties and micro-structures with aging. The work using commercial components confirmed micro-structural changes with aging.
  • The ATC testing showed that the magnitude of the aging effects are dependent strongly on the component type, CTE mismatch, nominal strain level, and ATC test parameters. The work also showed that in some cases, the effects due to in situ aging during thermal cycling control the failure process, not the effects due to the initial thermal aging, In some cases the work showed aging effects with Sn-Pb as well. 
  • More work needs to be done to better understand this phenomena. 
Approach: 
  • Use an existing test board design and component(s) to facilitate the launch of the SAC Aging II Project.  The component(s) will be selected from ones that have shown signs of being impacted by aging in the Mild Acceleration Test
  • Perform baseline micro-structural characterization on ambient (no age) and aged samples.
  • Perform failure mode analysis and characterization on ATC samples to determine extent of micro-structural evolution and impact on final failure.
  • Build additional samples (5 boards for each component type) for micro-structural analysis at different aging times/temperatures.