A Process Improvement in Silver-indium Transient Liquid Phase Bonding Method for the High-Power Electronics and Photonics Packaging

It has been demonstrated that the silver-indium (Ag-In) transient liquid phase (TLP) method [1] can be used in the heterogeneous integration between the chemical vapor deposition (CVD) diamond and Cu, whereby forming an advanced composite heat spreading submount for the future high-power electronics and photonics. However, some issues regarding to the Op species oxygen group trapped within grain boundaries of silver layer and Ag tarnishing during electroplating process were found in the previous research work[2]. Above issues resulted in an adversary effect on the bonding strength of Ag-In TLP joint. In this current paper, to further explore the Ag-In TLP bonding method in the utility of high-power electronics packaging, the authors have deposited multilayer metal film structures on diamond and copper substrates, with a combined process of the electroplating method and E-beam evaporation deposition. In order to eliminate the isolated voids on the bonding interface caused by undersupply of the indium molten phase during the TLP process, a vacuum annealing treatment was introduced to the E-beam deposited and electroplated silver layer, prior to the bonding process. We have changed the recipe of indium electro-plating solution, to a sulfur-element free one. Therefore, the previous reported oxide trapping and Ag tarnishing issues during the indium plating have been successfully resolved. In conclusion, this research work will pave the path for the future utility of Ag-In TLP method in the advanced high-power electronics and photonics packaging[3].