Crack Formation after Thermal Cycling Tests for Sn2.3Ag Microbumps with Different Under-Bump-Metallization Structures

• Main Authors: Mo, Chun-Chieh, 莫竣傑
• Other Authors: Chen, Chih
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47952366753963799832

碩士 === 國立交通大學 === 加速器光源科技與應用碩士學位學程 === 100 === Due to the progress of packaging technology from 2-dimension to 3-dimension (3D) stacking, the decreasing in pitch of microbumps is inevitable. It was reported the intermetallic compounds (IMCs) are brittle and thus not good for 3D integrated circuit (IC) reliability. While the microbumps are getting smaller, the IMCs will occupy a large percentage of joint volume. Therefore, it is important to study the effect of IMC formation in mechanical properties of microbumps. In this study, different kinds of structures, Cu/solder/Cu, Cu/solder/Ni, and Ni/solder/Ni, were used to study the effect of different IMCs on the crack resistance during thermal cycling test (TCT). The solders are Sn2.3Ag, and the heights were 10µm and 40µm. After various reflow time at 260 ℃, the microbumps were tested under TCT. (-55oC to 125oC) We will discuss the effect of reflow times, solder heights, and the IMC compositions on the failure mechanisms of microbumps under TCT. After long period of reflow, the IMC bridging phenomena was observed in most of the low solder height samples. Before IMC bridging, we can observed the crack appeared from the edge of the IMC/solder interface. The length of cracks increased as the solder height. Comparing the Cu/solder/Cu and Cu/solder/Ni system, the ternary IMCs can significantly reduce the cracks between the IMC/solder interface and inhibit the cracks propagation. The IMC-bridged microbumps can endure 2000-cycle TCT and reduce crack propagation. According to these obtained results, the IMC bridging is an advantageous to the TCT in microbumps. The IMC bridging effectively minimize the crack initiation and propagation.