Top-side chip contacts with low temperature joining technique (LTJT)

Chip temperatures above 175 °C are a demand for future power module applications. Low temperature joining technique, LTJT, shows excellent thermal and mechanical characteristics. The highly reliable joints stay stable even above 300 °C although the joining process takes place at 230 °C. Thus LTJT is currently investigated for application in high temperature electronics. LTJT is known to work for large area junctions like for chip- or substrate-mount. Taking advantage of its full performance would only be possible if both sides of a chip were joined by a LTJT method. Here a new development on LTJT is presented that expands its application to top-side chip contacts. The new method is based on using a dispenser for the silver powder application. The new degree of freedom in structuring junctions is presented, and the characteristics of the dot shaped contacts are investigated. It is shown that a wire-bond like contact system on the basis of LTJT is practicable and exhibits very good mechanical strength up to 300 °C in addition to its well known excellent thermal and electrical conductivity. To sum up LTJT can fulfill all requirements on a joining technique for high temperature module set-up.