Improved thermal cycling reliability of Ag sinter joining by optimized chip mounting speed and push depth

Ag particle paste sintering has been developed and shown a good performance in areas such as high temperature reliability and high electronic conductivity. Recently, it was found that the microstructure of a sintered Ag layer exhibits a coarse-dense inhomogeneous distribution after sintering, which depends on the loading speed of a die during the chip mounting process due to the flow characteristics of the Ag particle paste. In this work, the effect of the die mounting speed and the push-in amount (push depth) in the die mounting process on the microstructure of the sintered Ag layer, shear strength and thermal cycling reliability of Ag sinter joint structures were investigated. The results show that the shear strength of the sintered Ag joints was largely influenced by the speed and push depth during mounting process. The fast push speed exhibited a better shear strength, and the push depth can be optimized to obtain a better shear strength. In addition, the reliability during the thermal cycling of the Ag sinter joint structures with different the die mounting speed and the push depth were evaluated during a thermal cycling test from - 40 to 175 degrees C for 500 h. Cracks propagated after the thermal cycle test at the high porosity area near the die edge when the die was mounted with a slow speed, leading to a shear strength quickly decreasing after the thermal cycle test. The die attached structure showed better thermal cycling reliability in the case where the die was mounted with a fast speed.