New metallurgical systems for electronic soldering applications

The aim of this paper is to present results on a new soldering process base d on the low-temperature solidification of intermetallic phases from the sy stem Cu-Sn-Cu which can be employed to form a heat-resistant die-attach as well as signal and power electric contacts. Because of the total transforma tion into intermetallic phase, the working temperature of the bond formed i s several hundred degrees Celsius higher than the process temperature (arou nd 250 degrees C). This process leads to a homologous temperature T/T-m of about 0.3 compared to 0.7 in the case of soft SnAg solder alloy. Therefore a better reliability of the proposed bonding process is achievable. Results of the match of the predicted volume fraction of the intermetallic forms a nd the experimentally measured contact volume would be also discussed, for contacts formed in power diodes. (C) 1999 Elsevier Science S.A. All rights reserved.