| Abstract: |
The rising interest in lead-free solders creates a need for complete property data on the various lead-free solder compositions. Various types of data are available, but are widely dispersed through the literature. To improve the sharing of this important information, we developed an on-line database for solder properties emphasizing new lead-free solders. As data came in, we found it difficult to combine data from some sources, due to differences in procedures under which the data were developed. Therefore, we developed a practice guide to offer some standard procedures for future work. Finally, once we had collected as much information as possible, we began to develop data to fill in some of the gaps. Intermetallic formation and growth were studied for the alloys Sn-3.2Ag-0.8Cu, Sn-3.5Ag, Sn-0.7Cu, and Sn-9Zn. Coupons of solder joints (prepared by melting some of each solder alloy on a copper-plated circuit board) were subjected to thermal aging tests for 20, 100, 200, and 500 hours at 70, 100, and 150 oC. The results confirm that the formation of intermetallic layers is controlled by diffusion and that the intermetallic layers grow by thermal activation in a parabolic manner. |
Click here to retrieve PDF version of paper (267KB)