臺灣博碩士論文加值系統

壽命改善微機電式麥克風在chip-on-board (COB)製程中通常都是使用黏著膠材將其黏著在printed wiring board(PWB)上，再封上具導電性的外蓋，以杜絕外界的電磁波等干擾因素。將製作好的晶片以表面黏著技術(Surface Mounted Technology,SMT)，透過加熱到260℃將其晶片錫焊到用途較廣的主機板(Motherboard)上，而整個COB製的微機電式麥克風必須經過迴焊的高溫，因此，如何降低熱膨脹係數的不匹配所引起的熱變形與熱應力成為了黏著膠材選擇的關鍵。在這項研究中，我們採用的三種不同材料特性的黏著膠材，即ABLEBOND®2025D、DOW CORNING®3140RTV和CORNING®DA6501，和兩種不同材質的外蓋，即芳香族聚酯液晶聚合物(Liquid Crystal Polymer,LCP)和金屬鎳(Nickel)，以Finite Element Analysis(FEA)進行了一個具有多晶矽振動薄膜的麥克風晶片在封裝過程中因Reflow加熱而在薄膜上所產生的熱應力分析。為了提高MEMS麥克風於完成製程後的可靠性與良率，我們採用了一次迴流焊的溫度，由23℃到260℃再降溫至23℃。並以實驗的方式對照模擬結果，將晶片放至於加熱板上加熱，並以白光干涉儀(White Light Interferometers)量測振動薄膜之熱變形量。根據模擬結果，我們可以得到以下三項結論:(1)因LCP蓋與Ni蓋的CTE mismatch 造成PWB截然不同的變形，然而，不同外蓋材質對於振動薄膜上的熱應力影響卻小。(2)當黏著膠材的的厚度大於30um時，隨著厚度的增加振動薄膜上的熱應力也會隨著增加。而在黏著膠材2025D的楊氏係數遠高於其他兩種軟性膠材的狀況下，PWB的熱變形可能直接影響到矽晶片，因為在黏著膠材為2025D且厚度在30μm以下時，因PWB的熱變形影響使振動薄膜上的熱應力下降。(3)當黏著膠材有足夠厚度後，微機電式麥克風上的應力係由矽晶片與黏著膠材CTE mismatch有關，而底部PWB熱變形的影響變少，發揮所謂的緩衝層的效果。因此我們在黏著膠材的選擇上應偏向CTE值較小的軟性膠材，且厚度不宜過厚。在一般的情形之下，本研究提供MEMS封裝中COB製程上膠材選擇的依據。

MEMS microphone die attached on the printed wiring board (PWB) is by the chip-on-board (COB) process, and then sealed with a conductive outer cover to prevent interference from outside factors such as electromagnetic. Furthermore, MEMS microphone chip bonding on the a wider use of Motherboard by the SMT (Surface Mounted Technology), but MEMS microphones have to through the reflow. Therefore, how to reduce thermal deformation and thermal stress caused by the thermal expansion coefficient mismatch, choose adhesive material is crucial. In this study, we used three different material properties of the adhesive materials, that are ABLEBOND ® 2025D, DOW CORNING ® 3140RTV and CORNING ® DA6501, and two different cap materials, the LCP ( Liquid Crystal Polymer) and Nickel (Ni). Used Finite Element Analysis software ABAQUS to simulation microphone have been heating by Reflow, and then we can used simulation result to improve the MEMS microphone after the reflow of process are reliability and yield, we use a reflow temperature from 23 ℃ to 260 ℃ and then cooled to 23 ℃. Also comparison the experimental and simulation result, and used white light interferometer measure the diaphragm surface of thermal deformation. According to the results, we obtained the following three findings: (1) The CTE mismatch of LCP cap and the metal (Ni) cap are caused different type of thermal deformations of PWB, and lower thermally-induced stress and deformation were found in the case of LCP cap, however, different cap materials less affected the thermal stress in the diaphragm. (2) When the adhesive is greater than the thickness of 30um, the thermal stresses on the diaphragm are followed increase with increase adhesive thickness. The 2025D adhesive materials of the Young's modulus is much higher than the other two of soft adhesive materials, the PWB thermal deformation may have a direct impact on silicon. Because the adhesive materials of the 2025D and the thickness of 30μm or less, the thermal stress on the diaphragm not increase with adhesive thickness. (3) When the adhesive has sufficient thickness, the thermal stress on the MEMS microphone of the silicon and adhesive are compensation by CTE mismatch, whereas the bottom PCB of the thermal deformation effect is fewer, it is to play the so-called buffer effect. Consequently, we are the choice of adhesive materials tend to the smaller CTE value of the soft material. In general, present study provides the basis of selection of adhesive material for COB MEMS packaging.

摘要 I
Abstract III
致謝 V
目錄 VI
表目錄 IX
圖目錄 X
符號彙編 XIV
第一章 前言 1
1.1 研究動機 1
1.1.1 COB製程 7
1.1.2 SMT製程介紹 8
1.1.3 MEMS麥克風介紹 11
1.2 文獻回顧 14
1.3 研究目的 21
1.4 研究架構 22
第二章 理論基礎與研究方法 23
2.1 熱應力之概念 23
2.1.1 抵抗熱變形產生之應力 23
2.1.2 由溫度梯度引起之應力 26
2.1.3 由不同熱膨脹係數引起之應力 28
2.2 熱翹曲變形之現象 29
2.3 研究方法與步驟 30
2.4 研究流程 32
2.5 預設條件 33
第三章 有限元素模擬 34
3.1 二維有限元素模擬 34
3.1.1 二維麥克風模型之建立及參數條件 34
3.1.2 二維麥克風模型加熱及邊界條件之設定 38
3.1.3 二維模擬分析之結果與討論 40
3.1.3.1 楊氏係數對振動薄膜最大應力之影響 40
3.1.3.2 二維模擬結論 42
3.2 三維有限元素模擬 43
3.2.1 三維麥克風模型之建立及參數條件 43
3.2.2 三維麥克風模型加熱及邊界條件之設定 45
3.2.3 三維模擬分析之結果與討論 46
3.2.3.1 熱應力分析 47
3.3 緩衝層(Buffer Layer)效應 53
第四章 晶片黏著與實驗方法 56
4.1 晶片黏著 56
4.1.1 晶片黏著流程 56
4.1.2 晶片溢膠狀況 59
4.2 實驗設備 60
4.3 實驗架設與量測 63
4.4 實驗結果與討論 64
第五章 結論與未來展望 66
5.1 結論 66
5.2 未來展望 66
參考文獻 68
作者簡介 70

1.李文輝,“微機電式麥克風於覆晶式封裝法之最佳化研究”,南台科技大學奈米研究所碩士論文,2009
2.謝慶堂、丁志明、楊志輝、鐘震桂, “微機電封裝技術之簡介”, 工業材料193期， pp.175-180， 2003.
3.江昱成, “BGA構裝中SAC與SACNG無鉛焊料與Au/N/Cu多層結構之介面反應與焊點破壞性質”,國立台灣科技大學化學工程系碩士論文,2008
4.工作熊, “COB (Chip On Board) 製程介紹/簡介”,2008年8月,取自網路http://findliving.blogspot.com/2008/08/cob-chip-on-board-i.html
5.Kaven ,“SMT於FPC製程與應用”, 2010年12月,取自網路http://www.s-tek.com.tw/pdf/2008MR-SMTinFPC.pdf
6.Tom Tuhus, Are Bjomeklett, ”Thermal Cycling Reliability of Die Bonding Adhesives”, Proceedings of IEEE/IRPS, pp. 204-208, 1993
7.M. Li, Q. Huang, J. Song, J. Tang, F. Chen, ”Theoretical and Experimental Study on the Thermally Induced Packaging Effect in COB Structures”, Proceedings of Electronic Packaging Technology. ICEPT '06. 7th, pp 1-5, 2006.
8.Andrew A. O. Tay, K. Y. Goh, ”A Study of Delamination Growth in the Die-Attach Layer of Plastic IC Packages Under Hygrothermal Loading During Solder Reflow”, Proceedings of IEEE Transactions on Device and Materials reliability, vol. 3, no. 4,pp. 144-151, December 2003
9.Z. G. Sun, W. D. Huang, Y. Jiang, L. Luo, ”Evolution of Residual-Inplane Stress during Adhesive Curing and Recuring in Chip-on-Board Packages”, Journal of ELECTRONIC MATERIALS, vol. 31, No. 8,pp. 887-894, 2002
10.M. S. Zarnik, D. Rocak, and S. Macek, “Residual stresses in a pressure-sensor package induce adhesive material during curing: a case study”, Proceedings of Sensors and Actuators A, vol. 116, pp. 442-449, 2004.
11.J.B. Xu, Y.L. Zhao, Z.D. Jiang, ”Analysis of the Packaging Stresses in Monolithic Multi- Sensor”, Proceedings of the 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, pp. 241-244, 2007.
12.Z. Y. Zhang, Z. Wan, C. Liu, G. Cao, Y. Lu and S. Liu , “Effects of Adhesive Material on the Output Characteristics of Pressure Sensor.”, Proceedings of 11th International Conference on Electronic Packaging Technology & High Density Packaging, pp. 657-660, 2010.
13.呂宗興, “從IC封裝的角度看系統產品組裝製程及使用期間所產生之IC元件失效問題”, 台灣印刷電路板協會 TPCA, 2010
14.愛發股份有限公司, “ABAQUS實務入門引導”,全華科技圖書, 2005 原著