High Reliability Sintered Silver-Indium Bonding with Anti-Oxidation Property for High Temperature Applications

Abstract

Next generation of power semiconductor modules for electric vehicles, aerospace, and other industries require higher power and higher service temperature. In the past decades, wide bandgap semiconductors have been demonstrated to operate successfully at vtemperature above 300°C. However, traditional packaging materials such as tin-based solders and conductive adhesives are constrained to operation temperatures lower than 200°C. Thus, researchers have been seeking various methods to achieve high reliability joints that can operate at high power and high temperatures. For the past many years, sintering of silver or copper paste has been watched out as a promising technique. In the sintered joints, critical issues have recently been identified as follows: high porosity, poor interfacial wettability, and substrate oxidation, all leading to low reliability. To address the above issues, we proposed a novel bonding process called sintered silver-indium bonding (SSIB) process to produce reliable high temperature joints. The SSIB process incorporates the advantages of silver-indium transient liquid phase (TLP) bonding and nano-silver paste sintering. Our goal is to develop a feasible die attachment technology and packaging material for high power and high temperature applications. It has been shown in our previous studies that by adding indium inside the sintered nano-silver joint, the porosity was considerably lowered and the interfacial wettability was significantly enhanced. In order to further confirm the feasibility and potential of the SSIB process and sintered silver-indium joint, in this paper we evaluate the reliabilities by conducting high temperature storage test and temperature cycling test. Both high temperature reliability and temperature cycling reliability are the most critical and important properties that industries concern for high power and high temperature applications. The high temperature storage tests were conducted at 300°C in air and with the storage time from 50 h to 2000 h. For the temperature cycling tests, the temperature range was from -65°C to 150°C for 500 cycles, which conforms the Grade 1 condition of AEC-Q100 Rev-H Standard. After the above two reliability tests, both of the sintered nano-silver joints and sintered silver-indium joints were assessed by die shear tests and microstructure analyses to examine the evolution of the mechanical properties, bonding quality and phase transformations. From all aspects of the test results, sintered silver-indium joints have always performed better than sintered nano-silver joints. In summary, the innovative SSIB process reported here presents a new promise and opportunity to package high power and high temperature devices with high reliabilities.