Sequential interfacial reactions of Au/In/Au transient liquid phase-bonded joints for power electronics applications

The transient liquid phase (TLP) bonding of Au/In/Au as a die-attach material for high-temperature applications was studied in this work. The sequential interfacial reactions between Au and In layers and the phase transformations of an In solder to the intermetallic compound (IMC) phases of the Au/In/Au joints were investigated for TLP bonding at 190 °C for up to 30 min under different bonding pressures (0.2-10 MPa). The TLP joint was fully converted into the Au-rich Au7In3 IMC. During TLP bonding, the In solder was sequentially transformed in the following order: I (Au7In3, AuIn, and AuIn2), II (Au7In3 and AuIn), and III (Au7In3). We effectively fabricated the Au/In/Au TLP-bonded joint under moderate bonding pressures of 5 and 10 MPa for a short bonding time.