Mechanical properties of transient liquid phase bonded joints by using Ag-In sandwich structure

Transient liquid phase bonding has attracted considerable interests as a potential die attachment method for high power modules. However, the drawback of the long processing time restricts its wide application in industry. In this study, a novel transit liquid phase bonding method by using a sandwich structure of In-coated Ag sheet was proposed. The influence of bonding time on the microstructure and mechanical properties of the bonded joints were investigated. It was found that a qualified bonding joint with shear strength of 19.2 MPa could be obtained even within 10 min at 225°C. The microstructure of the bonded joint was mainly composed by Ag
9
In
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. Several unbonded-like lines were observed at the last solidification area, which served as potential crack propagation path during fracture. As bonding time increased from 5 min to 30 min, the failure position changed from along unbonded-like lines to inside of Ag
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In
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layer. Brittle trans granular fracture and intergranular fracture were identified from each failure positions, respectively.