Due to increasing regulatory and consumer pressure on the industry to remove lead from semiconductor assembly, the search for a lead-free solder - used to attach the semiconductor chip to the substrate (Leadframe) - has become an important production factor. ESEC, together with OMG-dmc~2 division and the University of Darmstadt (both Germany) has accomplished an extensive development program intended to identify a drop-in solution for currently commonly used Pb-based alloys. Using computer added development tools together with experimental methods the group was able to develop a set of Bi-based solders that not only meet most of the criteria for soft solder die attach applications but exceeds those in some cases. Investigated and presented are the physical properties of the new alloys like, wetting behavior, mechanical deformation behavior, heat dissipation and results like thermal cycling behavior and void rates obtained by producing and investigating real devices.
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