E. A. Holm, M. K. Neilsen, A. F. Fossum, P. T. Vianco, S. N. Burchett, Sandia National Laboratories, Albuquerque, NM
Because solders operate at high homologous temperatures, their microstructures continually change. In environments that include thermal cycling, microstructural evolution combines with cyclic strain to initiate thermomechanical fatigue (TMF), a principal failure mechanism in Pb-Sn solders. However, most interconnect design tools do not account for these microstructural changes. Since predicting solder joint lifetime is critical to designing for product reliability, we have developed a viscoplastic continuum damage (VCD) model for TMF of Pb-Sn solders that includes the coupling between microstructural evolution and thermomechanical response. This model captures experimentally observed phenomena, and corroborates empirical observations of existing circuit boards. Utilizing a microstructural failure criterion, we predict widely varying interconnect lifetimes for different joint geometries. A simplified version of the VCD model, the Solder Interconnect Predictor (SIP), is available as a desktop design tool. This science-based approach to solder joint design can improve manufactured products that undergo frequent or severe thermal cycling (automobiles) as well as high reliability products (satellites, aircraft).
This work was performed in part at Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.
Because solders operate at high homologous temperatures, their microstructures continually change. In environments that include thermal cycling, microstructural evolution combines with cyclic strain to initiate thermomechanical fatigue (TMF), a principal failure mechanism in Pb-Sn solders. However, most interconnect design tools do not account for these microstructural changes. Since predicting solder joint lifetime is critical to designing for product reliability, we have developed a viscoplastic continuum damage (VCD) model for TMF of Pb-Sn solders that includes the coupling between microstructural evolution and thermomechanical response. This model captures experimentally observed phenomena, and corroborates empirical observations of existing circuit boards. Utilizing a microstructural failure criterion, we predict widely varying interconnect lifetimes for different joint geometries. A simplified version of the VCD model, the Solder Interconnect Predictor (SIP), is available as a desktop design tool. This science-based approach to solder joint design can improve manufactured products that undergo frequent or severe thermal cycling (automobiles) as well as high reliability products (satellites, aircraft).
This work was performed in part at Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.
