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|Evaluation of reliability of lead-free solders in silver-free hybrids|
|Keywords: lead free solder, thick film , reliability|
|Silver and silver-based alloys are widely used for hybrid substrates conductors, components terminals and conductive attach materials. On the other hand, silver is one material of concern for high-voltage hybrid assemblies that have to operate in harsh non-hermetic or semi-hermetic applications. In this work, the reliability testing of silver-free passive components attach materials were conducted. The target application temperature for this research is 200C. Three lead-free solder pastes were evaluated: Sn100C, Sn96 and Au80Sn20. Sn96 solder contains 3.5% of silver was chosen as a comparison group. Two types of Ag-free thick film substrates were tested with different type of solders to mount SMT components. The assembled test samples were subjected to aging test, thermal cycle test, vibration and shock test. At each test intervals, shear test were performed to evaluate the mechanical performance. Cross sections on the solder joint and thick film interface were used to understand the intermetallic compounds (IMC) formation and failure mechanisms under thermal stress. Test for conductive filament growth was preformed to evaluate Sn-based solders behavior under target environmental conditions and high electrical stress. Test results were discussed and suggestions for achieving a reliable lead-free thick film hybrid were made.|
Baker Hughes GE