多晶矽材料之線切割放電加工特性及其 表面品質改善之研究

Machining characteristics of polycrystalline silicon by wire electrical discharge machining and surface quality improvement

游博淮(Yu-Po Huai)

指導教授 ： 顏炳華

國立中央大學/工學院/機械工程學系/博士(2011年)

摘要

太陽能電池近年來在成本與轉換效率上的改善，使得其應用日漸普及，但亦因全球矽晶棒之產能不足，使得原材價格節節上升，因此如何降低矽晶圓切割加工過程的材料損耗(kerf loss)，成為目前重要之課題。因此本文利用線切割放電加工法(Wire electrical discharge machining, WEDM)來加工多晶矽材料(2-3 Ωcm)，探討各項參數因子對於加工特性上的影響。由實驗結果得知，開路電壓為影響多晶矽材料突破絕緣的關鍵參數，而脈衝時間(pulse-on time)則對加工率影響也有相對影響。其它加工因子則對加工速率影響不大，但對加工溝槽寬和表面粗糙度則有改善效果。實驗中亦導入以雙脈衝波電源模式進行加工，與傳統脈衝電源相較，可提升加工速率。由實驗証明此線切割放電加工法確實可應用在多晶矽材料的切割，日後將此線切割放電製程技術應用於太陽能相關產業上，將有很大之競爭力。
雖然線切割放電可應用於多晶矽材料上切割，但加工機制乃是利用電能轉變成熱能產生高溫達到去除材料的目的，在加工過程中，會因產生的局部高溫而使材料表面上形成微裂痕及放電坑，如此問題將會造成日後太陽能電池相關製成上產生負面影響，所以需要二次加工來進行改善。因此後續以電解加工附加磁力的方式，針對放電加工後的多晶矽材料進行表面改善的加工探討。電解實驗過程中以附加磁力的方式，能可有效改善加工後的表面品質，其改善率為33%。

關鍵字

電解加工 ； 線切割放電加工 ； 微裂痕 ； 多晶矽 ； 放電坑

並列摘要

In recent years, the application of solar cell is very popular since the significant improvements on cost and electrical transfer efficiency. Accordingly, there is a big shortage on the raw material. Hence, how to minimize the kerf loss during machining so as to reduce cost for solar cell production has currently become an important research issue. This study examines the use of wire electrical discharge machining (WEDM) in machining polycrystalline silicon with resistivity of 2-3 Ωcm. The effects of different WEDM parameters on cutting speed, machining groove width, and surface roughness are explored. Experimental results indicate that open voltage is the critical parameter in breaking the insulation of polycrystalline silicon. The experimental results show that WEDM can be practically applied to machining polycrystalline silicon. Hence, applications of WEDM to manufacturing of solar cell can lead to significant enhancement in production efficiency. However, WEDM material removal mechanism involves heat generation. Cracks and craters are also formed on the workpiece surface under high-temperature melting and rapid cooling. All these undermine the surface quality of the WEDMed workpiece, which in turn affect both precision and life of the final product. Therefore, the improvement of surface defects by electrolytic machining (EM) to enhance surface quality will also introduce in this study. The experiment results show the surface roughness improvement rate up to 33 %.

並列關鍵字

crack ； electrolytic machining (EM) ； polycrystall silicon ； Wire electrical discharge machining (WEDM)

參考文獻

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