Study of Metallurgical Reactions between Copper and Sn2.3Ag Microbumps

• Main Author: 宋韋奇
• Other Authors: 陳智
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/09846055912917859589

碩士 === 國立交通大學 === 材料科學與工程學系 === 99 === Due to the progress of packaging technology, microbumps has been adapted as the interconnect of advanced packaging. When the interconnect is shrinkage into microbump level, reliability become an important issue. In this study, we study the metallurgical reaction between Cu under bump metallization (UBM) and solder with 5μm, 9μm, and 19μm thickness at 260℃. The reflow time is 1 min, 5 min, 10min, 20min, and 30 min. Plan-view scanning electron microscope was employed to measure the diameter of the interfacial Cu6Sn5 intermetallic compounds (IMCs) after the selective removal of the un-reacted solder. It is found that the solder volume does not have a significant effect on the growth rate of the Cu6Sn5 IMCs. Because the Sn in solder is gradually depleted during the solder reactions, the concentration of Ag in solder increase obviously in the microbumps. Therefore, large precipitation of Ag3Sn may take place. We can observe large Ag3Sn precipitation in 2μm and 5μm solder after 2 and 11 minutes reflow, respectively. The probability of observing a large Ag3Sn IMC is shown that there is 68% chance of finding a large Ag3Sn IMC in 11-min-reflowed sample for 5μm solder. Theoretical calculation indicates that it takes 1.5 min reflow for 2μm solder for Ag concentration to increase to 3.5wt.%; while it is 10.2 min for 5μm solder, which agrees quite well with the experiment observation. For aging test at 150℃, we also measure the thickness of the IMCs and their growth rate. We found that the solder volume does not have a significant effect on the growth rate of Cu6Sn5 and Cu3Sn IMCs.