Effect of measured stress-strain solder data on die/substrate interface bond stress for large CTE mismatch

摘要

The thermal stresses generated during bonding of electronic devices to diamond substrates using a eutectic gold tin solder is studied using finite element analysis. The stress-strain behavior of the 8OAu2OSn solder material used in the numericalanalysis was experimentally determined et different temperatures. The maximum stresses determined using the experimentally measured stress-strain behavior of the solder are compared to those determined using perfectly elastic solder behavior. Using themeasured elastic-plastic behavior of the solder decreases the predicted final stress in the assembly because of the relatively low yield strength of the solder at temperatures close to its melting temperature.However, the decrease in the final stress (< 5%) is not significant when compared to the variations in ultimate strength of typical die materials (>13%). Therefore, it is concluded that the error resulting from assuming an elastic behavior for the soldermaterial is within the approximately 13% variation in published values of ultimate strength of common die materials.