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|Title: ||以表面處理控制自發性晶鬚生長及殘留應力對晶鬚生長動力學之影響;Control of Spontaneous Tin Whisker Growth by Surface Treatment and the Effect of Residual Stress on Growth Kinetics|
|Keywords: ||錫晶鬚;同步輻射;介金屬化合物;Tin whisker;synchrotron radiation;intermetallic compounds|
|Issue Date: ||2014-08-11 18:13:31 (UTC+8)|
由本論文之結果可知，表面氧化層越不緻密，可有效減少長而有害之晶鬚生長，降低元件損壞之風險，利用微結構觀察與晶鬚形貌之量測，推導出一晶鬚生成之數學模型：晶鬚指數，可提供研究晶鬚成長之基礎，亦可供業界於元件設計之參考。;In electronic package industry, the spontaneous growth of whiskers on tin thin films poses a threat to the reliability of electronic devices. These whiskers are produced by the continuous generation and relaxation of compressive stresses within the tin. The primary driving forces involved in Sn thin films grow on a Cu leadframe are the formations of intermetallic compounds (IMCs) resulting from the reaction between Cu and Sn and a dense oxide layer on Sn surfce. This study sought to overcome the unpredictable nature of whisker growth and achieve accurate quantitative analysis of the growth kinetics. The purpose of this research was to control the location of whisker growth, which occurs in the weak spots created by the lithographic processes associated with the application of tin oxide coatings. Scanning Electron Microscopy (SEM) was adopted to examine each whisker at every step to record the dimensions at different annealing time to calculate the real growth rate of whisker. This study employed synchrotron radiation X-ray diffractometery to identify variations in stress associated with whisker growth that fitted appropriately to the mathematical model. The results of this study could prove that the formation of a surface oxide layer is a necessary condition for controlling where whisker growth will occur.
We also investigated the relationship between cracks in the surface oxide layer and the growth of whiskers. The results represented that total volume of whisker growth was independently of the interval between weak spots. But the length of whisker and density of weak spots on surface oxide were disproportionate. This study employed statistical methods based on focused ion beam (FIB) observation to characterize the relationship between the total volume of the whisker growth and Cu6Sn5 IMCs. These results clearly demonstrate that the growth of whisker was the square root of annealing time (t1/2).
Our results verify the effectiveness of a Ni-P underlayer as a barrier to the inter-diffusion between Sn film and a Cu substrate that was a general mitigated method for whisker growth. The combination of weak spots on surface and measurement of residual stress were studied in the experimental. The results presented thin and layered Ni3Sn4 IMCs grew only and the residual stress was very small. As a result, no whisker growth occurred in the Sn/Ni-P/Cu specimens.
The creation of a weak oxide layer or taking steps to prevent the formation of intermetallic compounds could be very important for reducing the threat of short circuit. A “Whisker Index” was proposed to evaluate the effect of microstructure and surface treatments on the kinetics of whisker growth for providing the fundamental knowledge of whisker growth and the future design of devices.
|Appears in Collections:||[化學工程與材料工程研究所] 博碩士論文|
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