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SAC Aging Factors

Idea/Definition Information
Summary: 

Endeavor to answer the following questions: What is the effect of aging time (post assembly) on SAC solder joint reliability? What is the effect of aging temperature?  How does SAC305 compare to SAC387?  How does strain level interact with aging?

Background: 

HDPUG SAC Acceleration Factors Project Observation: Aging of assembled test cards at 125C for 10 days prior to ATC testing affected thermal cycle reliability.  Others are reporting varying levels of a similar phenomenon (from significant to none).

Problem: 

Magnitude of effect apparently increases with SAC solder Ag content and cyclic strain levels.  May be negligible at some conditions.

Approach: 

A screening experiment to investigate:

  • Effect of post assembly thermal aging on SAC solder joint thermal cycle reliability
    • cyclic life degradation? why?
  • Effect of aging time and temperature
    • a thermally activated process?
  • Effect of SAC Ag content: SAC305 vs SAC387
    • silver content anticipated to be a significant factor
  • Effect of cycle strain level on aging behavior
    • higher strain appears to exaggerate aging effects