鋁/聚亞醯胺複合凸塊應用於COG製程之研究

Abstract

晶粒-玻璃接合技術(Chip-on-Glass，COG)擁有密度最高、製程最 少 、成本最低等優點，是未來液晶顯示器(Liquid Crystal Display，LCD) 驅動IC構裝的主流技術之一。本研究探討低成本的鋁/聚亞醯胺 (Aluminum/Polyimide，Al/PI)複合凸塊之結構設計，並依序進行耐 探 針測試實驗、COG接合參數找尋實驗、可靠度實驗，以驗證其替代 傳統 高成本的金凸塊應用於COG製程的可行性。耐探針測試實驗結果 顯示， 第III型Al/PI複合凸塊當Al層厚度大於0.8μm時，具有 良好的耐 探針測試性。可靠度實驗結果顯示，第III型Al/PI複合凸 塊應用於Al 墊玻璃基板的COG接合，當Al/PI複合凸塊的Al層厚度 大於1.1μm時 ，可得到優良的接點品質，其接點電阻(2個接點)平 均值為4.9Ω；標 準差σ為0.2Ω。經60℃，90％RH貯存試驗、 85℃貯存試驗、-20 ℃貯存試驗、-25℃∼70℃熱循環試驗等四種可 靠度實驗，其接點電阻 改變平均值△Rav及接點電阻改變值的標準差 σ的最大值分別為△Rav ＝1.8Ω；σ＝2.2Ω，符合產品應用之標 準。同樣的Al/PI複合凸塊 應用於ITO墊玻璃基板的COG接合，其接 點電阻及可靠度實驗接點電阻 改變值則偏高，於產品的應用上需再作 進一步研究及改善。 The COG technology has become the most competitive technology for LCD driver IC packaging due to its advantages of the highest density, the less process steps and the lowest cost. As a replacement of conventional Au bump, the applicability of Al/PI composite bump for COG process was investigated. We evaluated the probing testability, COG bonding parameters, and its reliability through environment tests. Among the four different types of Al/PI bumps fabricated in this work, the type-III bump with thickness of Al overlayer exceeding 0.8 μm exhibited excellent probing testability. The type-III bump with Al layer over 1.1 μm applied to COG process with Al pad on glass also showed satisfactory contact quality. The average contact resistance (included 2 contact points) was 4.9 Ω with the standard deviation (σ) 0.2 Ω. Through the environment tests (a 60℃, 90%RH storage test; a 85℃ storage test; a -20℃ storage test; a -25℃ ~ 70℃ thermal cycling test), the average contact resistance change (△Rav) was no more than 1.8 Ω with the standard deviation less than 2.2 Ω. These results indicated the Al/PI bumps with type-III configuration can be applied to real COG process with Al pad on glass. As to the same A1/PI bump applied to COG process with ITO pad on glass, after environment tests the contact resistance was found to be too high for real product applications. Further study is hence required for the realization of such a Al/PI bump for COG process with ITO pad on glass.