微液滴噴墨技術是一非接觸式的直接製造方法，透過電腦輔助控制，可將材料直接噴覆於特定位置點上。由於液滴的精微尺寸，且其噴覆於基板後之凝固過程極為短暫，在實驗中無法清楚觀察，故以數值方法模擬微液滴噴覆於基板後之行為，將利於觀察解析各種微液滴在基板上之相關現象。

本研究主要是將數值模擬技術應用於熔融無鉛銲錫微液滴噴覆於基板上之行為探討，藉由實驗比對，找出適當的界面熱傳係數。利用噴墨技術噴印Sn3.0Ag0.5Cu合金材料噴印於鍍金玻璃基板上，並使用商用軟體Flow-3D模擬微液滴噴覆於基板上之流動及熱傳現象，以預測不同參數條件下之導線型態及線寬。

由模擬結果發現，微液滴與基板間的界面熱傳係數，隨液滴飛行速度的增加有增大的趨勢，而界面熱傳係數增大，將適時停止微液滴擴張和回彈，使擴散因子不隨液滴飛行速度增大有太大的變化，對銲錫凝固後的尺寸造成影響。此外，在導線的噴製上，由於多顆微液滴之間有相互吸引拉扯的作用，影響微導線凝固後之型態及線寬。較大的液滴間距或較高的噴覆頻率使線寬縮減。當液滴間距為140 μm，導線出現一斷裂不連續處。當噴覆頻率為1/70 1/ μs，導線出現一明顯的頸縮現象。

Drop-on-demand inkjet printing technology was a direct droplet deposition method. Materials can be deposited on the demand positions. Experimental investigation of the droplet solidification process is quite challenging due to the very short time and length scales involved. Therefore, a numerical modeling is used in order to observe the phenomena occurring during the droplet impaction on the substrate.

The research is aimed at applying the numerical modeling on the micro-droplet deposition of molten lead-free solder, and experiments were conducted to determine the interfacial heat transfer coefficients between solders and substrate. Sn3.0Ag0.5Cu alloys were deposited on a gold-coating glass substrate by inkjet printing technology, and commercial software Flow-3D was adopted to simulate the fluid dynamics and thermal transients of molten solders after deposited on the substrate in order to predict the morphology and line width of micro-conductive line.

The simulated results show the interfacial heat transfer coefficients between solders and substrate for various velocities increase with increasing velocity, and the interfacial heat transfer coefficient would effect the spead factors of solder. For micro-conductive line formation, the aggregation of multi-droplet influence the morphology and line width of micro-conductive line. Large step sizes or high deposition frequencies would decrease the line width. The micro-conductive line broke when step size was 140 μm and necked when the deposition frequency was 1/70 1/ μs.

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