無凸塊式TAB熱超音波接合技術與可靠度之研究

Abstract

本研究利用熱超音波接合(Thermosonic Bonding)技術 , 及田口式直 交表實驗法(Taguchi Method) , 探討在無凸塊(Bumpless)晶片上進行捲 帶式自動接合(Tape Automated Bonding , TAB)的可行性與可靠度 。 除 了以拉離試驗(Pull Test)評估接合的品質良窳 , 並以掃描式電子顯微 鏡(Scanning Electron Microscopy , SEM)觀察接點拉離後的破壞模式 , 以提供接合方法上的改進 。田口式實驗之結果顯示溫度150℃、時間160 msec、力量90g、振幅200μin可使鍍金之銅引腳在具金-鉭(Au-Ta)接墊的 晶片上獲得最佳之熱超音波接合。由於量產用晶片上均覆有一層高分子保 護膜 , 為符合實際之材料特性限制 , 本實驗選用120℃/160msec/90 g/200μin為接合參數進行驗證實驗及可靠度實驗,實驗結果顯示無凸塊式 TAB熱超音波單點接合技術確實可行。吾人採用高溫貯存及85℃/85%RH高 溫高溼貯存實驗以探討接合品質之變化 , 實驗結果顯示 , 接合完成之捲 帶在150℃及300℃高溫貯存及85℃/85%RH貯存1000小時後 , 接合的品質 無劣化之現象發生 , 此結果除顯示前述接合參數之選擇為正確外 , 亦顯 示接合後適度之熱處理有助接合品質之提升。本實驗同時將晶片做160℃ 和400℃退火處理再進行接合 , 觀察其對接合強度的影響 , 實驗結果顯 示晶片做短時間160℃退火處理有利於接合 , 退火時間太長或溫度過高 , 則將造成接合強度的劣化。 In this work we investigated the feasibility of thermosonic bonding applied to inner lead bonding (ILB) process of bumpless TAB and its bonding reliability. The Taguchi methods were employed for the searching of bonding parameters, and the optimum bonding was achieved at the conditions of substrate temperature = 150℃, bonding time = 160msec, bonding force = 90g, and thermosonic amplitude = 200μin. We adopted the bonding parameters 120℃/160msec/90g/200μin for the identification tests since in practice the chip was coated with a polymer protection layer which could not sustain the temperatures as high as 150℃. The results of identification experiments and subsequent reliability tests indicated that the bumpless TAB was a feasible process incorporating with thermosonic bonding. Through a high-temperature storage test and a 85℃/85%RH storage test without bias for 1000hrs, the leads bonded within above conditions exhibited no deterioration of bonding strength.The high-temperature storage test also revealed the bonding quality would be benefited if an appropriate post-annealing treatment were carried out. The effect of annealing prior to TAB inner lead bonding was also evaluated. Annealing for a short times at 160℃ was found to enhance the bonding strength, while annealing for long times or at high temperature(e.g., at 400℃) deteriorated the bonding strength.