Reliability issues of replacing solder with conductive adhesives in power modules

Electrically conductive adhesives are potential candidates as die attach materials for power modules because they offer simplified and environmentally compatible processing and easier reworkability compared to solder joining. There are, however, reliability issues which must be considered carefully before the adhesives can be used in a production setting. In this study, three silver-filled epoxy-based adhesives and a solder alloy were tested in a power module test structure. The test modules went through thermal and operational cycling as well as elevated humidity and temperature aging. Mechanical stresses were endured well by most of the test adhesives. Elevated humidity and temperature aging showed, though, that the right adhesive choice is important for successful module performance. One of the adhesives was clearly superior when compared with the other two adhesives. None of them, however, showed any silver migration in the humid conditions