以電流驅動錫晶鬚的成長之研究

Abstract

因近年來環境保護的考量，在微電子構裝工業中，無鉛銲錫逐漸地取代傳統的有鉛 銲錫。以使得而在大部份的無鉛銲料中，錫的成分比例皆超過95%，造成錫晶鬚的議題 變得很重要。但要研究錫晶鬚成長並不容易，主要是溫度太低(低於30°C)，錫晶鬚成長 非常慢，溫度太高(高於70°C)，應力被釋放而不會成長。對此議題我們發展出利用電流 驅動錫晶鬚成長。先期研究發現我們可以在室溫到100°C皆能在數十小時到數百小時內 成長錫晶鬚。因此，此方法能提供錫晶鬚成長的加速測試。對於錫晶鬚成長機制能夠有 系統地研究。 我們將以國際合作的方式來執行此計畫，與美國加州大學洛杉磯分校（UCLA）材 料系的杜經寧教授合作，因為杜教授在這方面有幾十年的經驗，以及他們可以用美國 Advanced Light Source 國家實驗室的同步輻射（synchrotron radiation）來量測小區域 的應力大小及分佈。本計劃中將於第一年裡，將分析錫鉛銲錫薄膜合金試片，而於第一 年中建立起分析錫鉛銲錫晶鬚的成長速率。第二年將開始研究無鉛銲錫的晶鬚成長，與 其應力分佈。除了實驗的觀測外，也將會與杜教授合作，以理論來推導晶鬚的成長速率。 爾後，在本國合計劃的第二年裡，杜教授團隊將觀測薄膜通電前後的陽極端壓應力變化 與其對晶鬚成長的影響。為分析晶鬚成長之活化能，於本計畫的第三年裡將主要對於薄 膜不同溫度下通電前後的陽極端壓應力變化與其對晶鬚成長的影響。由於後學已經與杜 教授有多年的合作經驗，並共同發表多篇優質期刊論文，我們將會密切合作，相信將會 很成功並對錫晶鬚成長機制有更深入的瞭解。

Due to environmental concerns, Pb-free solders have gradually replaced Pb-bearing solders in microelectronic packaging. In most of the Pb-free solders, the contents of Sn are over 95 wt%, making the Sn whisker issue an important issue. However, it is not easy to study this issue since its growth rate is too low at low temperature (<30°C) and it did not grow at temperature higher and about 70°C due to stress relaxation. We have developed an approach to grow whiskers by electrical current. Our preliminary results shows that whiskers still grow at very fast rate even at 100°C. Therefore, this approach can provide the accelerated test and systematic study for whisker growth. We would like to cooperate with Prof. King-Ning Tu at MSE dept at UCLA. Because he has a lot of experience on this topic and they have access to the synchrotron radiation in Advanced Light Source, USA. The synchrotron radiation can measure the stress value and distribution in a small region. This proposal will analyze the whisker growth in SnPb solder in the first year. We will establish the measure grow rate and mechanism in SnPb solder first, and then extend it to Pb-free solders in the 2nd year. In addition to experimental measurement, we will work with Prof. Tu on trying to formulate the grow rate theoretically. The stress analysis on Pb-free solder will be conducted by synchrotron radiation in the second year. To measure the activation energy, the growth rate at different temperatures will be measured for both SnPb and Pb-free solders. Since our group has been working with Prof. Tu for many years, and we have published several excellent papers together, I believe we will work closely and this project will be very successful. We will provide deeper understanding on the mechanism of Sn whisker growth.