本實驗室過去開發 Cu/Ni/Ga/Ni/Cu 的固溶型暫態液相接合技術[1] [2] [3]，輔以聲化學合成法製備次微米 Ga 粒子基漿料，改善 Ga 基材料的保存性，最佳的接合條件為利用 Cu/0.1 μm Ni/酸性助銲劑/次微米 Ga 粒子/0.1 μm Ni /Cu 的三明治結構於 300 ℃、10 MPa 下熱壓接合 1 小時，得到接合界面為 FCC-(Cu, Ni, Ga) 固溶相接點，具有 13 MPa 的接合強度，且隨著長時間的高溫儲存後，其接合強度會逐漸提升，足以補足初始強度稍低的部分，為應用於功率元件的一大優勢，目前已在美國、日本、中國、台灣取得專利。但目前還沒有塗佈參數定量化之相關數據，而噴墨列印法為可靠的漿料轉移技術，不僅可精確控制漿料塗佈量，更可以快速轉移單點或單面的漿料，期許未來能投入工業級生產。漿料轉移製程使用壓電噴墨機，將波形參數固定為 Trise = 30 μs, Tdwell = 20 μs, TFall = 15 μs, TEcho dwell = 15 μs, Trise = 5 μs，脈衝電壓為 ±50 V，墨滴間距 200 μm，可形成穩定不分裂的墨滴，實際印製可得一規則的陣列。從微觀角度檢視，Ga 粒子於溶劑範圍中覆蓋率約 50%，厚度僅約 0.450 μm，較過往塗佈方式如微量滴管，其厚度降低一倍左右。漿料中之 Ga 粒子的開殼製程為一重要環節，透過合適的酸性助銲劑可以快速打破外圍氧化殼層，幫助液態 Ga 在更短時間內往兩側基板擴散，有助於之後往低溫、短時間的接合製程優化。我們期望 Ga 粒子與助銲劑在室溫不反應，維持設計的噴印陣列分布，避免 Ga bulk 被擠壓而分布不均。待闔上上板與下板後，升溫至 150˚C 以上才發生破殼。因此在不同溫度下的開殼臨界 pH 值是一重要資訊。以鹽酸與乙二醇混和溶液進行開殼實驗，當環境溫度為 30˚C，粒子開殼的臨界 pH 值為 0.7。當環境溫度上升至 90˚C，粒子開殼的臨界 pH 值為 1.2。另以鹽酸與去離子水混和溶液進行開殼實驗，當環境溫度為 30˚C，粒子開殼的臨界 pH 值為 1.4。當環境溫度上升至 90˚C，粒子開殼的臨界 pH 值為 1.6。比較使用不同溶劑 (乙二醇/水) 的開殼後形貌，發現以去離子水配置的鹽酸水溶液開殼效果較符合需求。在高溫 90˚C 時，當溶液 pH ≤ 1.6，只需 3 分鐘即可完全開殼，Ga bulk 的直徑僅約 0.5~5 μm，分布相當均勻且緊密。此部分可作接合溫度優化之參考。

For the paste transfer, we are trying to confirm and control the Ga amount by inkjet printing. The transfer method using now can provide a thin Ga SMPs layer with the help of UV light cleaning. Fix the waveform parameters as Trise = 30 μs, Tdwell = 20 μs, TFall = 15 μs, TEcho dwell = 15 μs, Tr ise= 5 μs, and pulse voltage is ±50 V, which can form stable ink drops and obtain a regular array. The coverage of Ga particles in solvents is nearly 50%, and the thickness is only about 0.450 μm. Compared with the previous coating methods such as micropipette and spin coating, the thickness is reduced by about one time. For another subject, we try to figure out the releasing process between the pH value and releasing ability. Mixing a solution of hydrochloric acid and ethylene glycol. When the temperature is 30 ̊C, the critical pH is 0.7. When the temperature rises to 90 ̊C, the critical pH is 1.2. In addition, a mixture of hydrochloric acid and deionized water is used for the experiment. When the temperature is 30 ̊C, the critical pH is 1.4. When the temperature rises to 90 ̊C, the critical pH is 1.6, it takes only 3 minutes to completely release. Diameter of Ga bulk is about 0.5~5 μm, and the distribution is uniform and close. This section could be the reference for the critical pH value at 150 ̊C and the optimization of bonding temperature.With the check on transferring and releasing process for core-shell Ga-particle pastes, we are looking forward to the reproducibility of good bonding interface.

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