壓電噴印技術是一種直接寫的製程技術，由於噴印品質的大幅改善與生產速度的提升，可以應用於電子封裝產業。此技術的優點包括可變的液滴尺寸、定位精度高、快速製造和低生產成本。然而，為了使熔融金屬微液滴能穩定地形成，並且製備精微金屬結構，在高溫下能操作壓電驅動裝置，適當的製程參數調整是必須，因此在實驗方面針對高溫噴墨進行研究，探討噴印條件對三維金屬微結構品質之影響。
本研究主要採用Sn-3Ag-0.5Cu無鉛銲錫為研究主軸，分別進行點、線、牆、三維結構等基礎研究，目的在不同製程參數條件下，以高速攝影機觀察熔融金屬微液滴撞擊基板後，形成金屬微液滴堆疊結構、微導線過程及在矽薄膜太陽能電池上作為接合銅箔導帶之應用。首先，金屬微液滴堆疊的結構上，則是探討噴印高度與噴印速度的改變對金屬微液滴堆疊形狀影響，並且配合模擬熔融金屬微液滴的撞擊與凝固過程，以多顆液滴沉積堆疊方式觀察液滴的溫度場、凝固場及速度場之情形，最終與實驗進行驗證；接著，就是探討藉由液滴間距、試片溫度與載台移動速度的改變，對金屬微液滴沉積導線結構之影響，在實驗過程中，找出不同試片溫度對金屬液滴沉積線寬、高度與凝固接觸角之結果。此外，藉由試片溫度的改變找出導線牆之緻密噴印品質；最後，則是研究Sn-3Ag-0.5Cu無鉛銲錫的潤濕行為與應用於矽薄膜太陽能電池基板上之鋁電極進行接合，藉由使用壓電噴印的方式將熔融無鉛銲錫進行沉積代替銀膠接合，以改善在矽薄膜太陽能電池鋁電極與銅箔導帶之間的接合強度與轉換效率。
利用高速攝影機可觀察記錄到金屬微液滴的沉積與堆疊情形，這些條件的無因次參數範圍韋伯(We)數為2.1-15.1與奧內佐格(Oh)數5.4×10-3-3.8×10-3，液滴撞擊後直徑是37-65μm、液滴體積為25-144 pl與液滴撞擊速度為 2.0-3.7 m∙s-1，結果可成功噴印出垂直與傾斜結構的微液柱；在噴印微導線方面，則是固定試片溫度30 °C、液滴間距50 μm及載台移動速度為50 mm∙s-1，可找出金屬微導線結構線寬為55 μm，並且當試片溫度為70 °C，可成功觀察出無孔洞之緻密導線牆結構；在太陽能電池銅箔導帶接合上，找出沉積銲錫液滴間距為200 μm (單位面積銲錫量為50 μg∙mm-2)可優於銀膠的剝離強度，當銲錫液滴間距微縮小為100 μm (單位面積銲錫量為201 μg∙mm-2)，則可獲得最低的最大功率損失為1.1%與矽薄膜太陽能電池之轉換效率8.3%。

Inkjet printing technology has made great improvements in print quality and reproduction speed, and is now widely used in the modern electronics packaging industry. The merits of this approach include variable drop size, high precision in positioning, rapid prototyping, and low production cost. However, parameter adjustment is necessary when operating a piezoelectric device at high temperature in order to pile up the molten metallic droplets in stable formations.
The Sn-3Ag-0.5Cu lead-free solder material was employed in this study for observing droplets pile up and micro line structures during inkjet printing, and bonding silicon thin-film solar cell modules of the ink-jet printing method. First, the effects of the jet height and variations in impact velocity of successive droplets piled up shapes were observed. The other objective is to obtain the widths and shapes of the molten micro droplets. The effects of the dot spacing, sample temperature and variations in motion velocity of consistent droplets on the shapes of the conducting lines were recorded. Finally, the purpose of this study is to investigate the wetting behavior of the Sn-3Ag-0.5Cu solder alloy and inkjet printing for bonding on the aluminum electrode of a silicon thin-film solar cell substrate. Molten lead-free solder was deposited by utilizing inkjet printing to replace silver paste, thus improving the bonding strength of the connections between the back electrode of the aluminum and copper ribbon in the fabrication of thin-film solar cell modules.
A high-speed digital camera was used to record the solder impact and examine the accuracy of the pile up. These impact conditions correspond to We =2.1-15.1 and Oh =5.4×10-3-3.8×10-3. The diameter, volume and velocity of the inkjet solder droplet are around 37-65 μm, 25-144 picoliters, and 2.0-3.7 m∙s-1, respectively. The vertical and inclined column structures of molten lead-free solder can be fabricated using piezoelectric ink-jet printing systems. The line width of each sample was then calculated using a formula over a temperature range of 30 to 70 °C. The results showed that a metallic line with a width of 55 μm can be successfully printed with dot spacing (50 μm) and the stage velocity (50 mm∙s-1) at the substrate temperature of 30 °C. The experimental results revealed that the height (from 0.63 to 0.58) and solidification contact angle (from 72° to 56°) of the metallic micro droplets decreased as the temperature of the sample increased from 30 to 70 °C. The peel strength of the Sn-3.0Ag-0.5Cu solder alloy is better than that of silver paste when the dot spacing of solder droplets is lower than 200 μm (a density of over 50 μg∙mm-2). The findings also show that the contact resistance of the solder alloy is better than that of silver paste when the dot spacing of solder droplets is lower than 100 μm. This results in a low power loss of solar cells of 1.1%, and a good photovoltaic conversion efficiency of over 8.3%. This study thus demonstrates the feasibility of decreasing the efficiency loss of solar cells by employing the proper spacing of lead-free solder droplets by inkjet printing.

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