線放電切割與電解磨削應用於多晶矽晶碇之加工特性研究

Processing Characteristics of Polycrystalline Silicon by Wire Electrical Discharge Machining and Electrochemical Grinding

葉金璋(Chin-chang Yeh)

指導教授 ： 顏炳華

國立中央大學/工學院/機械工程學系/博士(2014年)

摘要

現今再生能源的研究與發展已成為全球共識，當中以太陽能電池相關技術發展最受矚目。太陽能電池製造時，晶碇的切割製程是決定成本的主要關鍵。現有切割方式則以多線鋸加工為主，其優點為可複線式加工，加工效率高。但此方式為接觸式加工，過程中易產生加工應力進而造成晶碇破裂損壞。其游離磨粒加工時無法完全使用，並且在回收時過程複雜及會造成環境污染。因此，近年來相關研究文獻中提出，採用線放電加工方式切割矽晶材料，使用此方式可有效改善線鋸加工之缺點。但目前仍以加工單晶矽材料為主，而多晶矽材料的線放電加工方面文獻甚少，主要原因為多晶矽材料具有晶界多變、電阻大等特性，導致無法順利進行線放電切割加工。但是多晶矽材料具有製程簡單、成本較低與光電效率穩定等優勢，因此更需要發展新的方法，改善多晶矽材料的加工問題。
本論文中採用線放電切割與電解磨削的兩種製程方式，對多晶矽材料之加工特性進行研究。本文分為兩大研究方向，第一部份為應用線放電製程於多晶矽材料進行切割加工，探討放電參數對於多晶矽材料切割加工時的影響，並調製磷加工液對其加工效率與特性進行改善。第二部分為應用電解磨削製程對線放電切割後表面缺陷進行磨削，改善表面粗糙度及異質層的去除，使用田口實驗法進行實驗規劃，經由分析後得到製程的主要影響因子。後續於電解加工液中加入石墨烯材料，藉由此材料的高硬度與高磨潤性，改善原有的表面加工特性，並探討製程參數對於加工時的影響。
經由本論文實驗後，線放電切割加工方面，證實磷加工液可以有效使放電過程中的放電能量增強與導電度提升，可以在不改變現有加工參數的條件下，提升切割速度與降低切口損失。電解磨削表面加工方面，加入石墨烯材料後，可有效改善放電加工後殘留之表面問題並減少加工時的摩擦力進而提升磨削刀具壽命。期望藉由本論文之研究成果作為產學界研究之參考。

關鍵字

線放電切割加工 ； 電解磨削 ； 磷加工液 ； 多晶矽 ； 石墨烯

並列摘要

Nowadays, the researches and developments of renewable energy have become the universal consensus. Among them, the developments of solar cell attract the greatest attention. In the process of making solar cell, the cutting process of silicon ingot is the key to determine the cost. Multi-wire saw has been used in the traditional cutting to conduct machining process. Its advantage is to multi-wire-type processing, which heighten the processing efficiency. However, multi wire requires great tension and produces stress that could easily damage the silicon ingot. In addition, during the process, abrasive could not be used completely. The complicated recycle processes of abrasive contaminate the environment. Thus, in recent years, related research proposed in the literature, by using wire electrical discharge machining (WEDM) cutting silicon ingot, this method can effectively improve the shortcomings multi-wire saw. WEDM has been applied onto the single-crystal silicon cutting. Most researches adopted single-crystal silicon as the process material. However, it is hard to find a literature review on the machining characteristics of a polycrystalline silicon surface and the quality improvements after processing. The main reasons of polycrystalline silicon are changing boundaries, high electrical resistance and other characteristics, which lead WEDM can not be process smoothly. Polycrystalline silicon manufacturing process is simple, lower cost, stable photoelectric efficiency and other advantages. Therefore, a new method to improve the polycrystalline silicon processing problems needs to be developed.
This thesis adopts machining characteristics of polycrystalline silicon research by WEDM and electrochemical grinding (ECG) these two methods. This paper divided into two research directions. The first part discusses when the polycrystalline silicon by using WEDM processing, the impact of discharge parameters on the polycrystalline silicon and the adjustments of phosphorous dielectric improve its processing efficiency and processing characteristics. The second part is the application of ECG surface defects after WEDM be grinded, it improves the removal of surface roughness and affected layer by using Taguchi-method experiment planning, the main factor affects the analysis process to get through. Follow added graphene in dielectric. By using the high hardness and high lubricity of graphene to improve processing characteristics of the original surface and explore the impact of process parameters for the processing.
After the experiments by this thesis, it is sure that in the WEDM processing, phosphorous dielectric improves the discharge process effectively and makes the discharge energy booster to enhance conductivity. Under the no-changing existed processing parameters condition, it improves the cutting speed and reduces kerf loss. In the ECG processing, by adding graphene, the surface problems effectively improved after WEDM machining residues and reduce friction force during processing and it enhances the grinding tool life. It is expected the results of this thesis could be referenced for the future research in both industrials and academic field.

並列關鍵字

wire electrical discharge machining ； electrochemical grinding ； phosphorous dielectric ； polycrystalline silicon ； graphene

參考文獻

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[37] 崔海平，「電化學結合電泳精密拋光不鏽鋼之研究」，國立中央大學，博士論文，民國96年。

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