台灣留學生出席國際會議補助

2007年3月12日 星期一

Thermomigration of Pb in eutectic SnPb flip chip solder joints

論文發表人:歐陽汎怡(加州大學洛杉磯校區材料科學與工博士班)

http://www.tms.org/Meetings/Annual-07/AnnMtg07Home.html

隨著半導體工業持續地追求高密度的輸入/輸出點和消費電子產品持續的小型化,覆晶封裝中的銲錫球的電遷移和熱遷移效用獲得越來越多的重視。當電流密度高到 104 A/cm2時,覆晶封裝中的銲錫球的熱遷移效用是不容忽略的。熱遷移是一種由於溫度梯度所造成的質量移動。此現象是個不可逆的過程。一個小小1C的溫度梯度跨過一個10微米的焊錫球就會產生一個每1公分1000C的溫度差,這個溫度差非常的大。所以我們不可以忽略熱遷移的效用。此外,當電遷移和熱遷移一起發生在覆晶封裝銲錫球時,由於大的孔洞形成在銲錫球的陰極和熱端,快速的破壞機制發生 。在這個研究中,我門調查覆晶封裝中的共晶錫鉛銲錫球的熱遷移效用,從我們的結果發現,隨著鉛是主要的控制元素和擴散到銲錫球的冷端,我們觀察到鉛和錫的重新分布。另一個有趣的發現是,相對於傳統的Soret效用,我們發現沒有鉛或錫線性濃度差存在。此外,銲錫球的微結構分佈變的更細小,這個現在指出自由能和介面能的增加。最後,鉛的莫耳傳播值被計算為每莫耳25千焦。

Thermomigration is defined as mass flow driven by a temperature gradient. It is an irreversible process. A temperature difference of 1 ℃ across a solder joint with 10 μm in height will produce a temperature gradient of 1000 ℃/cm, which cannot be ignored. When electromigration is combined with thermomigration in flip chip solder joints, fast failure due to large void formation at the cathode and the hot end occurs. In this talk, thermomigration in flip chip solder joints of eutectic SnPb will be presented. Redistribution of Sn and Pb has been observed, with Pb being the dominant diffusing species and moving to the cold end. No linear concentration gradient in either Pb or Sn is observed, contrary to the classical Soret effect. The lamellar structure becomes finer after thermomigration, indicating an increase in lamellar interfaces and in free energy. The molar heat of transport of Pb has been calculated to be - 25 kJ/mole.

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2007年3月8日 星期四

A Pneumatic Haptic Feedback Actuator Array for Robotic Surgery or Simulation

論文發表人:金志鴻 (加州大學洛杉磯分校生物醫學工程研究所博士班)

http://www.nextmed.com/mmvr_proceedings.html

機械輔助微創手術較一般內視鏡手術擁有極佳自由度的優點,因此成為新興的關鍵技術。 然而,在手術執行者缺乏實際觸覺回饋的情況下,僅能仰賴視覺來進行手術。 在機械手臂遠端控制介面加裝氣動式觸覺回饋致動器陣列能滿足手術進行中觸覺回饋的需求。 此裝置具有質量輕、體積小、成本低、以及通用於各種機械手臂等特點。 利用由矽膠薄膜所製成的氣動裝置,配合機械手臂尖端力的感應訊號,手術執行者的手部可以感應此裝置的力量傳遞,達到觸覺回饋的目的。 本研究探討了氣動裝置的大小(直徑0.75 ~ 2.00 mm)對手指觸感的靈敏度 ,藉此達到氣動裝置大小的最佳化。 初步結果證明了大於 1.00 mm 的裝置能提供較佳的觸覺反應。 此研究發明更可以普遍地應用在虛擬實境及義肢觸覺回饋等尖端領域。

Robot-assisted minimally invasive surgery (MIS) offers improved range of motion over standard laparoscopic techniques, but is characterized by a total loss of haptic feedback, requiring surgeons to rely solely on visual cues. Pneumatic tactile displays have many advantages, including low mass, low cost, compact size, and adaptability. A pneumatic haptic feedback actuator array has been developed that is suitable for mounting unto surgical robotic tools. The balloon actuators consist of spin-coated thin-film silicone membranes and molded substrates with cylindrical channels. Human perceptual tests were conducted on balloon diameters ranging from 0.75 to 2.0 mm to determine the optimal size that can be effectively detected. The control system was programmed to sequentially inflate a single balloon to one of the three levels, 100% (full hemispherical deformation), zero, 50% (half deformation), and 0% (no inflation). Blinded subjects (n=5) were asked to determine which of the two inflation levels was higher. Test results suggest that balloon diameters greater than 1.0 mm can deliver high detection accuracy. This indicates that pneumatic balloon-based actuation is a viable solution for generating haptic feedback. In addition to surgical applications, many other fields such as virtual reality-based simulators and prosthetics can benefit from this technology.

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