NDLI: Silver-indium joints produced at low temperature for high temperature devices

Content Provider	IEEE Xplore Digital Library
Author	Chuang, R.W. Lee, C.C.
Copyright Year	1999
Abstract	A two-step fluxless bonding process adopted to produce high temperature silver-indium joints (80 wt% silver and 20 wt% indium) at relatively low process temperature of 206/spl deg/C has been developed. After annealing the joint continuously for 26 h at 145/spl deg/C, its melting temperature increases to 765-780/spl deg/C, as confirmed by a de-bonding test. The technique thus developed provides a viable alternative to packaging many high temperature devices running at 350/spl deg/C and above. The bonding quality of the Ag-In joints produced was examined using scanning acoustic microscopy. The joint cross-section was also studied using a scanning electron microscope equipped with an energy dispersive X-ray (EDX) spectroscope to find the local microstructure and composition. The results have shown that the joint is nearly void-free and uniform in thickness ranging from 7.2 to 7.8 /spl mu/m. The annealed sample joint, as determined by EDX, is mainly composed of AgIn/sub 2/, Ag/sub 2/In, and AuIn/sub 2/ grains embedded in an Ag-rich Ag-In alloy matrix. During joint formation, the intermetallic compound AgIn/sub 2/, in particular, prevents the indium layer from oxidation, and therefore, no flux is needed. In addition, low process temperatures help to reduce the thermal stresses developed in the bonded structure due to thermal expansion mismatch. Finally, reliability tests were conducted on three sets of annealed joints using a high temperature oven running continuously at 500/spl deg/C for 10, 100, and 1000 h each. Scanning acoustic microscopy (SAM) images on these samples confirmed that the joints have an excellent survivability in a high temperature environment.
Sponsorship	IEEE Components, Packaging, and Manufacturing Technology Society
Starting Page	453
Ending Page	458
Page Count	6
File Size	675420
File Format	PDF
ISSN	15213331
Volume Number	25
Issue Number	3
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2002-09-01
Publisher Place	U.S.A.
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Temperature Annealing Thermal stresses Indium Acoustic testing Microscopy Thermal expansion Bonding processes Silver Packaging
Content Type	Text
Resource Type	Article
Subject	Electronic, Optical and Magnetic Materials Electrical and Electronic Engineering

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