電鑄鑽石輪刀之線上旋轉電解銳化研究

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2021

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本研究提出一種「線上旋轉式電解銳化」的技術,用於對電鑄鑽石輪刀進行銳化及薄化研究。目前,半導體業大多使用電鑄鑽石輪刀進行晶粒分割(本文所稱晶粒,係指輪刀對矽晶圓切割後的微小晶片(chip)),由於結合鑽石磨粒的鎳具強韌性,且鑽石的高硬度與絕緣性,使得輪刀鈍化後,不易再被削銳,所以都直接丟棄。本研究設計一具有拘束電解液功能的電解槽,電解槽內具穩定流動的中性硝酸鈉電解液,填塞的輪刀透由高速主軸的緩速旋轉,浸入電解液中。藉由電解原理(反電鍍法),輪刀表面的鎳原子逐漸被均勻解離,填塞於屑袋中的磨屑便能順利脫離輪刀並裸露出新的鑽石磨粒,故輪刀能經300秒銳化,再度恢復研削力。輪刀電解銳化過程,鎳原子被逐顆移除,所以輪刀沒有機械式削銳的切削應力或熱應力,不會發生變形,能實現輪刀的銳化或輪刀薄化,獲得更窄的晶粒分割道。銳化過程,輪刀未與高速主軸分離,故銳化後的輪刀,可直接移位作晶粒分割,省卻再校正的繁瑣程序。實驗結果顯示,銳化後的輪刀可再增加5.5 m的研削長度,而位移平台電流回饋顯示,其研削阻抗由0.82 A降至0.21 A,並發現分割後的晶粒,其邊緣崩落量很少,證實「線上旋轉式電解銳化」技術著實能快速實現輪刀再生。在另一方面,本研究亦設計與輪刀互為平行的雙陰極板,透由兩側的電解電場作用,進行輪刀薄化。實驗結果顯示,原刃厚55 μm的電鑄鑽石輪刀,薄化至35 μm的刃厚,耗時僅約300秒,切割道槽寬由66 μm縮減至45 μm,延續的研削長度為4.5 m,說明輪刀薄化不但可延長輪刀壽命,更可降低研削阻抗及窄化切割道,並分割出更多的晶粒數。此項開發的「線上旋轉式電解銳化」技術經實驗證實能讓輪刀快速再生,且符合環保,具市場競爭力,期望未來能為半導體產業所用。
An "in-situ rotary electrolytic dressing technology" for sharpening and thinning electroformed diamond wheels is proposed in this study. At present, die separation is usually carried out by using electroformed diamond wheel by the semiconductor maker. (This "die" refers to the tiny chip after the silicon wafer is divided by the diamond wheel in this study). Due to the strong toughness of nickel combined with diamond abrasive grains, and the high hardness and insulation of diamond, the electroformed diamond wheel is not easy to be sharpened after dulling, it is discarded directly. An electrolytic tank, in which can stabilize the flow of neutral sodium nitrate electrolyte and prevent splashing, is designed and employed in this study. The clogged electroformed diamond wheel rotates slowly on the high-speed spindle and immersed into the electrolyte. By applying the principle of electrolysis (reverse electroplating), the nickel atoms on the surface of the diamond wheel are gradually and uniformly dissociated, and the grinding dust packed in the chip pockets can escape smoothly from the wheel and expose new diamond abrasive grains. The diamond wheel can restore the grinding force again after 300 seconds of electrolysis time. During the diamond wheel is electrolyzed, and nickel atoms are removed one by one. Therefore, there is no cutting stress, thermal stress and deformation on the wheel. In addition, the diamond wheel has not been unloaded from the high-speed spindle during the dressing process, hence, the dressed wheel can directly shift for next die separation, which saves the tedious procedure of re-calibration. Experimental results show that the dressed wheel can extend the tool life by increasing the grinding length of 5.5 m. The current feedback of the translation stage shows that the grinding resistance is reduced from 0.82 A to 0.21 A, and the amounts of edge avalanche of the divided dies are very small. It proves that the"in-situ rotary electrolytic dressing technology" can quickly realize the wheel regeneration. On the other hand, a dual-cathode plate parallel to the diamond wheel, which can thin the wheel width by the electrolytic electric field on both sides, is also designed in this study. Experimental results show that the original electroformed diamond wheel can be thinned from a thickness of 55 μm to 35 μm. It takes only about 300 seconds. The width of the cutting lane can be reduced from 66 μm to 45 μm and the extended grinding length is 4.5 m. This shows that the thinning of the wheel can not only reduce the grinding resistance and extend the lifetime, but also narrow the width of cutting path resulting in obtaining more dies. The developed"in-situ rotary electrolytic dressing technology" has been experimentally proven to enable the diamond wheel to regenerate quickly, is environmentally friendly, and has market competitiveness. It is expected to be used by the semiconductor industry in the future.

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電解銳化, 電解薄化, 輪刀再生, 屑袋, electrolytic dressing, electrolytic thinning, wheel regeneration, chip pocket

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