Temperature and Stress effects on IMC Behavior of Thin Film Cu-Al System in Wire Bond

Abstract

Wire bond is widely accepted as the predominant method for the area of electronic packaging. Copper wire has been studied to instead of the gold and aluminum owing to its advantages. In this paper, authors focus on the nanoscale interfacial characteristics of thermosonic copper ball bonding on the aluminum metallization. A serious of examinations and a 2.5D finite element simulation have been designed to find the IMC generation and the stress distribution. After the data and results are demonstrated in detail, some conclusions are drawn from the previous work. By TEM and SEM analysis, authors found at different temperature, the IMC layers showed great difference in the thickness. By X-rd and TEM analysis, the IMC also show difference in the organization. By the finite element analysis, authors found the stress distribution when copper was bonding on the aluminum pad. As the IMC layer's material characteristics are different form the copper and aluminum material, so when bonding at improper temperature, the IMC layer will show a bad behavior under the stress. By SEM picture of the real situation, some cracks can be easily found. On the other hand, by doing the research, people can have a general idea of the proper temperature and force when using copper wire bond.