201132430 六、發明說明： 【發明所屬之技術領域】 本發明是關於使用於印刷配線板等的非鐵系被削材的 鑽孔加工等之鑽孔工具。 【先前技術】 在印刷配線板（PCB )之鑽孔加工，是使用如第1圖所 圖示般之由具有刃部C之主體部A和柄部B所構成之鑽頭。 其尺寸雖依用途而異，一般大多是使用直徑〇.7mm以下的 鑽頭。 具體而言，在刃部C，如第2圖所示般在主體2 0的外周 ，從鑽頭前端朝向基端側形成螺旋狀的切削屑排出溝槽22 ，在該切削屑排出溝槽22的傾斜面（rake face )和設置於 前端之第一刀腹面（flank face) 24之交叉稜線部形成切 刀2 1 (例如參照專利文獻1、2 )。又在圖中，符號2 5代表 連設於第一刀腹面24的工具旋轉方向後方側之第二刀腹面 ，d’爲工具直徑，Γ爲切削屑排出溝槽之溝槽長，α，爲扭 轉角。 此外，作爲適用於鋁合金、纟太、鎂、銅等的非鐵系被 削材之具有耐摩耗性和耐熔接性的被膜，非晶質碳被膜已 實用化，而用來被覆在鑽頭、端銑刀、刀口更換型切削塊 等的切削工具（例如參照專利文獻3 ).。 然而’ P C Β是將銅和絕緣層（讓玻璃纖維布含浸樹脂 而成）貼合而構成，近年來的PCB，爲了進一步提高可靠 -5- 201132430 性，是要求提昇耐熱性、提高彎曲強度以及減低熱膨脹’ 因此藉由將構成PCB之玻璃纖維布和樹脂的機械強度提高 ，以確保可靠性的情況變多。 然而，在考慮要進行鑽孔加工之被削材的情況，由於 上述構造的PCB之機械強度提高而容易促進鑽頭的摩耗， 容易在鑽孔加工中引發鑽頭折損，或因過度摩耗而導致孔 位置精度等的孔品質變差。 另一方面，隨著PCB之高密度化，所要求的孔徑（鑽 頭直徑）越來越小，直徑〇.4mm以下之鑽孔加工開始變多 〇 另外，在鑽孔加工步驟，考慮到加工效率，一般是將 同規格的PCB重疊複數片而進行鑽孔加工》 因此，近年來，即使是上述般之加工性較差的P CBM 工所使用之PCB用小徑鑽頭，爲了減少加工成本而要求 PCB重疊片數的增加，又要求延長鑽頭的鑽孔壽命（能在 未折損的狀態下進行鑽孔加工）。 〔專利文獻1〕日本特開昭5 6-3 98 07號公報 〔專利文獻2〕曰本特開2006-55915號公報 〔專利文獻3〕日本特開2001 -341 02 1號公報 【發明內容】 於是，本發明人等嘗試將TiN、TiCN、TiAIN等各種 的氮化物系陶瓷被膜被覆在鑽頭上而進行PCB的鑽孔加工 ，但相對於無被覆的鑽頭，並無法獲得耐折損性的提昇效 -6- 201132430 果。 此外，將非晶質碳被膜等的潤滑性被膜被覆在鑽頭上 所進行之P c B鑽孔加工，相對於無被覆的鑽頭雖可確認其 耐折損性有提昇，但仍有不足，依鑽孔加工時之鑽頭的轉 數和進給速度等的加工條件、PCB的材質，也確認出有較 早發生折損的情況。 本發明人等爲了解決上述問題而深入硏究的結果，獲 得以下所說明的見解而完成本發明。 如前述般，在鑽孔加工步驟，考慮加工效率而一般是 將同規格的P c B重疊複數片來進行鑽孔加工。 具體而言，一般是在複數片互相重疊的PCB上面，爲 了提高鑽頭的向心性而載置護板（鋁板或表面被覆有樹脂 之樹脂被覆鋁板）以進行鑽孔加工。樹脂被覆鋁板之向心 性提昇效果是比鋁板更佳，又有助於改善鑽頭折損，因此 常用於直徑0.4mm以下的小徑鑽頭之鑽孔加工。 然而，使用樹脂被覆鋁板作爲護板來進行鑽孔加工的 情況，相較於使用鋁板的情況，在鑽頭之刃部C的基端部 附近會明顯地產生切削屑的纏繞，樹脂黏性越高、所被覆 的樹脂越厚，產生前述切削屑纏繞的傾向越高。 這是因爲，通常鑽孔加工時產生的切削屑是藉由鑽孔 機所附設的切削屑吸引功能吸引而往既定的集塵盒搬出， 在使用樹脂被覆鋁板的情況，受到鑽孔加工時的切削熱而 軟化後之樹脂會和切削屑一起導入切削屑排出溝槽而排出 ，該樹脂在刃部C的基端部附近會將鑽頭和切削屑黏在一 201132430 起，經由繼續反覆進行鑽孔加工，切削屑的纏繞量會增多 切削屑的纏繞量，雖會依鑽孔加工時鑽頭的轉數和進 給速度等的加工條件、PCB的材質而改變，但如第3 ( a ) 圖所示般產生明顯的切削屑的纏繞，該切削屑的纏繞在接 續的鑽孔加工中，其切削屑（切削屑塊）會起因於振動等 而從鑽頭脫離，即使利用前述吸引功能仍無法予以吸引而 落到護板上，然後要進行鑽孔加工之鑽頭會被落下的切削 屑塊干涉，而產生孔位置精度變差、鑽頭折損。第3(b) 圖係例示出落到護板上的切削屑塊。 本發明人等探究出，在僅被覆潤滑性被膜的情況，相 較於無被覆之鑽頭，會明顯地產生切削屑纏繞，起因於前 述落下的切削屑塊之問題，會造成鑽頭之折損壽命不穩定 ，而可能發生提早折損的情況。 本發明是有鑑於上述現狀而提供一種實用性極優異的 鑽孔工具，其被覆有潤滑性被膜，且讓切削屑排出溝槽的 扭轉角在中途改變，藉此變得不容易折損且大幅提昇切削 屑排出性而防止切削屑纏繞，即使是直徑〇.7mm以下（特 別是0.4mm以下）之小徑鑽頭，仍能延長折損壽命而實現 穩定的鑽孔加工。 參照附圖來說明本發明的要旨。 一種鑽孔工具，是在工具主體1的外周，從工具前端 朝向基端側形成一或複數條螺旋狀的切削屑排出溝槽2， 在前述切削屑排出溝槽2被覆潤滑性被膜而構成的鑽孔工 201132430 具，其特徵在於，前述切削屑排出溝槽2係具備：胃； 一扭轉角ct 1之第一扭轉區域3、連設於該第—扭轉區域3 的工具基端側且具有第二扭轉角α 2 (比前述第〜柱^轉_ α 1更大）之第二扭轉區域4。 此外，在請求項1記載的鑽孔工具中，前述、潤、滑性$ 膜是非晶質碳被膜。 此外，在請求項1記載的鑽孔工具中，前述第_丨丑轉 角〇：!和前述第二扭轉角《2之角度分別設定成：在前述第 一扭轉區域3和前述第二扭轉區域4的連設部5，便沿著前 述切削屑排出溝槽2排出之切削屑的排出方向強制％ _ 而從前述工具主體1飛散出。 此外，在請求項2記載的鑽孔工具中，前述第—丨丑轉 角^:，和前述第二扭轉角α：2之角度分別設定成：在前述第 一扭轉區域3和前述第二扭轉區域4的連設部5，使沿著前 述切削屑排出溝槽2排出之切削屑的排出方向強制地改變 而從前述工具主體1飛散出。 另外，在請求項3記載的鑽孔工具中，前述第一扭轉 角α ,設定成30°〜45°，前述第二扭轉角α 2設定成比前述第 一扭轉角^，大5°以上，且前述第二扭轉角α2設定成35。 〜65。。 另外，在請求項4記載的鑽孔工具中，前述第一扭轉 角α ,設定成30°〜45°，前述第二扭轉角α 2設定成比前述第 一扭轉角αι大5°以上，且前述第二扭轉角α 2設定成35° 〜65。。 -9- 201132430 另外’在請求項3記載的鑽孔工具中，前述第一扭轉 角011設定成35°〜45°，前述第二扭轉角α2設定成比前述第 一扭轉角《，大10°以上，且前述第二扭轉角設定成45。 〜60°。 另外’在請求項4記載的鑽孔工具中，前述第一扭轉 角α !設定成35°〜4 5°，前述第二扭轉角α 2設定成比前述第 一扭轉角〇：1大10°以上，且前述第二扭轉角α 2設定成45。 〜60°。 此外’在請求項5記載的鑽孔工具中，前述第一扭轉 區域3和前述第二扭轉區域4的連設部5，是設置在從工具 最前端6起算0.2mm〜前述切削屑排出溝槽2全長1的1/2位置 〇 此外’在請求項6記載的鑽孔工具中，前述第一扭轉 區域3和前述第二扭轉區域4的連設部5，是設置在從工具 最前端6起算0.2mm〜前述切削屑排出溝槽2全長1的1/2位置 〇 此外’在請求項7記載的鑽孔工具中，前述第一扭轉 區域3和前述第二扭轉區域4的連設部5，是設置在從工具 最前端6起算0.2mm〜前述切削屑排出溝槽2全長1的1/2位置 〇 此外，在請求項8記載的鑽孔工具中，前述第一扭轉 區域3和前述第二扭轉區域4的連設部5，是設置在從工具 最前端6起算0.2mm〜前述切削屑排出溝槽2全長1的1/2位置 -10- 201132430 另外’在請求項1〜1 2中任一項記載的鑽孔工具中，工 具直徑爲〇.7mm以ί；·。 另外’在請求項1〜1 2中任一項記載的鑽孔工具中，工 具直徑爲0.4mm以·'p。 此外’在請求項14記載的鑽孔工具中，該鑽孔工具是 適用於使用護板將被加工物施以加工的情況。 此外’在請求項〗5記載的鑽孔工具中，前述護板是鋁 製。 此外’在請求項16記載的鑽孔工具中，前述護板的厚 度爲 0.04〜1.0mm。 另外’在請求項1 7記載的鑽孔工具中，前述被加工物 是設有銅箱層之印刷配線板。 此外，在請求項1 8記載的鑽孔工具中，前述銅箔層的 厚度爲2~80 μ m。 依據本發明的上述構造，可提供一種實用性極優異的 鑽孔工具，變得不容易折損且大幅提昇切削屑排出性而防 止切削屑纏繞，即使是直徑0.7mm以下（特別是〇.4mm以 下）之小徑鑽頭，仍能延長折損壽命而實現穩定的鑽孔加 工。 【實施方式】 針對本發明的較佳實施形態，根據圖式並配合本發明 的作用而簡單地說明。 至少在切削屑排出溝槽2被覆非晶質碳被膜等的潤滑 -11 - 201132430 性被膜，以提高切削屑排出溝槽之表面潤滑性，藉此使鑽 孔加工所產生之切削屑的剪切角變大而切削屑變得薄且長 ，又由於表面潤滑性高而容易使切削屑沿著切削屑排出溝 槽朝工具主體1 (第1圖的刃部c)之基端部排出，如此可 防止切削屑堵塞，而變得不容易折損。 此外，藉由縮小工具前端的扭轉角£^,，可防止切削 屑變得過於薄且長，使切削屑變得較厚短而不容易纏繞在 工具主體1，再者可確保較大的切刀之刀口角，因此可防 止切刀發生缺口而改善孔位置精度，變得不容易折損。 再者，藉由增大工具基端側的扭轉角α2，可提高切 削屑排出溝槽2的基端側之切削屑排出性而提昇耐折損性 ，而且，利用被覆非晶質碳被膜等的潤滑性被膜之效果， 讓沿著切削屑排出溝槽2順利排出之切削屑的排出方向強 制改變，配合上離心力之相乘效果，使其朝工具主體1的 外側飛散，可防止切削屑的纏繞，而實現折損壽命長之穩 定的鑽孔加工。 〔實施例〕 根據第4圖至第6圖來說明本發明的具體實施例。 本實施例之潤滑性被膜被覆鑽孔工具，是在工具主體 1的外周，從工具前端朝向基端側形成複數條螺旋狀的切 削屑排出溝槽2，在前述工具主體1 (切削屑排出溝槽2) 被覆潤滑性被膜而構成的鑽孔工具；前述切削屑排出溝槽 2係具備：具有第一扭轉角《!之第一扭轉區域3、連設於 -12- 201132430 該第一扭轉區域3的工具基端側且具有第二扭轉角α 2 (比 前述第一扭轉角αι更大）之第二扭轉區域4。 具體而言，本實施例之鑽頭，工具直徑d爲0· 1mm，且 設有兩條溝槽長1爲1.7mm之切削屑排出溝槽2，在該切削 屑排出溝槽2之傾斜面和前述工具主體1的前端刀腹面（第 一刀腹面）之交叉棱線部分別設有與前述工具主體1呈一 體的切刀，其適用於PCB的鑽孔加工。該PCB的鑽孔加工 ，例如後述實驗例所載般，將難切削材之半導體封裝用的 PCB (基板：厚〇_lmm/表裏兩面Cu層）重疊八片，在其上 面載置厚0.1mm之樹脂被覆鋁板來作爲護板，爲了進行貫 通孔加工，在前述PCB的下面配置一般使用之厚1.5mm的 紙酚醛材來作爲墊板，而在此狀態下進行。又護板厚度是 在0.04〜1.0mm的範圍內適當地設定。又厚0.1mm左右之 PCB的Cu層厚度通常爲2〜80//m左右。 更具體的說，在上述條件的情況，由於容易產生前述 切削屑的纏繞，爲解決此問題而將第2圖所示的工具予以 改良，亦即在工具主體1被覆非晶質碳被膜，在鑽頭之切 削屑排出溝槽2設置前述第一扭轉區域3和前述第二扭轉區 域4。 接著具體地說明各部位。 該鑽頭之基材，是主成分爲WC之硬質粒子和主成分 爲Co之結合材所構成之超硬合金製，該超硬合金之WC粒 子的平均粒徑爲Ο.Ι/im〜2//m，Co含量爲5〜15重量。/。，至 少在工具主體1的切削屑排出溝槽2被覆非晶質碳被膜。由 -13- 201132430 於非晶質碳被膜是硬質的，可抑制工具摩耗， 高潤滑性而使切削屑容易沿切削屑排出溝槽朝 1的基端部排出，因此可防止切削屑堵塞而變 損。 此外，在本實施例，作爲潤滑性被膜，雖 體爲碳原子所構成且維氏硬度3 000以上之高硬 碳（DLC )所構成的非晶質碳被膜，但只要 2 000以上即可，也能採用較低硬度的非晶質碳 DLC和其他物質（例如金屬）的混合物所構成 可採用鉻氮化物等的其他潤滑性被膜。 又在本實施例，非晶質碳被膜雖是直接形 ，但例如在基材上方形成下層被膜層（底膜， 表4a、5a、6a族及Si中之一種或兩種以上的元 屬或半金屬所構成，膜厚200nm以下lnm以上 層被膜層上形成前述非晶質碳被膜亦可。又作 層，並不限定於上述構造，亦可採用：選自周 、6a族及Si中之一種或兩種以上的元素、和選 一種以上的元素之化合物所構成。 此外，在本實施例，在進行非晶質碳被膜 膜時，雖是採用電弧離子鍍方式的成膜裝置， 濺鍍方式、雷射剝蝕方式等的PVD成膜裝置。 以下進一步說明本實施例。 第1扭轉角α ,設定爲3 0°〜45°。鑽頭之扭轉 切削屑的排出性和鑽頭剛性，藉由增大扭轉角 又由於具有 向工具主體 得不容易折 是採用：主 度的非晶質 維氏硬度在 丨（DLC)或 的被膜，亦 成在基材上 由選自周期 素組成的金 )，在該下 爲下層被膜 期表4a、5a 自氮及碳之 或底膜的成 但亦可使用 角，會影響 可提昇切削 -14- 201132430 屑排出性，相反地，會造成剛性降低。在小徑鑽頭的情況 ，鑽頭之耐折損性，不僅是剛性，還容易受切削屑排出性 的影響。因此，較佳爲將直徑0.7mm以下（特別是0.4mm 以下）的鑽頭之扭轉角設定成較大，一般是設定爲4(Γ〜50° 〇 本發明人等，爲了進一步提昇鑽頭之耐折損性，針對 扭轉角（顯現鑽頭剛性和切削屑排出性二種相反的特性） 深入硏究的結果得知，在被切削物上面載置鋁板或樹脂被 覆鋁板的情況、以及在被切削物的內外層等具有較多銅箔 的情況，若扭轉角未達3 0 °，切削屑排出性變差而使鑽頭 容易折損，當扭轉角設定成比45 °更大的情況，起因於切 削屑排出性的提昇雖可提昇耐折損性，但鋁或銅的切削屑 會變得過薄且長，在工具主體1 (切削屑排出溝槽2)的基 端部（根部）容易發生切削屑的纏繞。 再者，本發明人等如前述般探究出，在被覆非晶質碳 被膜等的潤滑性被膜之鑽頭的情況，相較於無被覆之鑽頭 雖具有提昇耐折損性的效果，但會明顯地產生切削屑纏繞 ’該切削屑的纏繞（切削屑塊）會落到護板上，所落下的 切削屑塊會干涉鑽頭而造成孔位置精度變差且鑽頭之折損 壽命變得不穩定，而可能發生提早折損的情況。 考慮這些點，進行切削之工具前端的切刀部分，其扭 轉角（第一扭轉角αι)較佳爲45。以下的角度（30。〜45。） ’以確保切削屑排出性並縮短切削屑長度而使切削屑變得 不容易纏繞。更佳爲設定成3 5。〜4 5。。在本實施例是設定成 -15- 201132430 35、 第二扭轉角α2是設定成比第一扭轉角α 1大5°以上的 角度，且設定爲35°〜6 5°。藉由使第二扭轉角α2比第一扭 轉角α !更大，可提昇切削屑排出溝槽2之基端側的切削屑 排出性而提昇耐折損性。 此外，利用被覆非晶質碳被膜（潤滑性被膜）的效果 ，能使沿著第一扭轉區域3 (設定成第一扭轉角a!)的切 削屑排出溝槽2順利地排出之切削屑的排出方向，往第二 扭轉區域4(設定成第二扭轉角α2)的切削屑排出溝槽2 強制地改變，配合上離心力的相乘效果而讓其朝工具主體 1的外側飛散，以防止切削屑的纏繞而使折損壽命變長且 穩定。 當第一扭轉角a i和第二扭轉角α 2的角度差未達5°的 情況，讓切削屑排出方向強制改變的效果差，不容易讓切 削屑朝工具主體1的外側飛散。此外，若第二扭轉角α 2比 65°更大，工具主體1的基端部剛性會降低，而使耐折損性 變差。 更佳爲，第一扭轉角α!和第二扭轉角α2的角度差設 定爲10°以上，且第二扭轉角α 2設定爲45°〜60°。在本實施 例，第二扭轉角α2設定爲：與第一扭轉角(35°)有10° 的角度差之45°。 此外，爲了良好地排出切削屑’宜儘量在工具前端側 朝第二扭轉角α 2改變’由於一般P C Β用的鑽頭在使用後必 須將前端重新硏磨而供使用（再硏磨）’第一扭轉區域3 -16- 201132430 和第二扭轉區域4的連設部5較佳爲’考慮硏磨量而設定在 從工具最前端6起算〇.2mm〜切削屑排出溝槽的溝槽長1之 1 / 2位置。 又若將連設部5的位置設定在工具最前端6起算之比溝 槽長1的1 / 2更後方的位置，由於扭轉角小之第一扭轉區域3 的部分會增加，造成切削屑排出性變差而使鑽頭折損的危 險性昇高。 在本實施例，第一扭轉角和第二扭轉角的變化 點（連設部5)，是設定在從工具最前端6起算之溝槽長1 的2 3 . 5 %的位置（C !)。 本發明的鑽頭，是使用於ρ c Β等的非鐵系被削材的鑽 孔加工且被覆有非晶質碳被膜等的潤滑性被膜’作爲其基 材，宜爲主成分爲WC之硬質粒子和主成分爲Co之結合材 所構成的超硬合金，由於其爲可取得硬度和韌性平衡的材 料。 若WC粒子的平均粒徑過小，在結合材中很難讓WC粒 子均一地分散，容易造成超硬合金之抗彎強度降低。另一 方面，若WC粒子過大，超硬合金的硬度降低。此外，若 Co含量過少，超硬合金的抗彎強度降低’相反地若Co含量 過多，超硬合金的硬度降低。因此，基材較佳使用：wc 粒子的平均粒徑爲o.l" m，Co含量爲5〜15重量％的 超硬合金。 此外，對於PCB等的難削材，爲了進行無被膜剝離之 穩定的鑽孔加工，較佳爲提昇基材和非晶質碳被膜的密合 -17- 201132430 性。在基材上方形成底膜（由選自Ti、Cr、Ta等的周期表 4a、5a、6a族及Si中之一種或兩種以上的元素組成的金屬 或半金屬所構成）’在其上方形成非晶質碳被膜，藉此可 更加提昇基材和非晶質碳被膜的密合性。此外，作爲形成 於基材上方之底膜，亦可爲由選自周期表4a、5a、6a族及 Si中之一種或兩種以上的元素、和選自氮及碳之一種以上 的元素之化合物。 設置底膜的目的是爲了提昇基材和非晶質碳被膜的密 合性，若過厚將失去其意義，因此膜厚宜爲200nm以下 lnm以上。 本實施例由於採用上述構造，至少在切削屑排出溝槽 2被覆非晶質碳被膜等的潤滑性被膜，可提高切削屑排出 溝槽之表面潤滑性，藉此使鑽孔加工所產生之切削屑的剪 切角變大而切削屑變得薄且長，又由於表面潤滑性高而容 易使切削屑沿著切削屑排出溝槽朝工具主體1 (第1圖的刃 部C)之基端部排出，如此可防止切削屑堵塞，而變得不 容易折損。 此外，藉由縮小工具前端的扭轉角αΐ，可防止切削 屑變得過於薄且長，使切削屑變得較厚短而不容易纏繞在 工具主體1，再者可確保較大的切刀之刀口角，因此可防 止切刀發生缺口而改善孔位置精度，變得不容易折損。 再者，藉由增大工具基端側的扭轉角α 2，可提高切 削屑排出溝槽2的基端側之切削屑排出性而提昇耐折損性 ，而且，利用被覆非晶質碳被膜（潤滑性被膜）之效果， -18- 201132430 讓沿著切削屑排出溝槽2順利排出之切削屑的排出方向強 制改變，配合上離心力之相乘效果，使其朝工具主體1的 外側飛散，可防止切削肩的纏繞，而實現折損壽命長之穩 定的鑽孔加工。 如此般，依據本實施例可提供一種實用性極優異的鑽 孔工具，即使是使用樹脂被覆銘板作爲護板的情況，仍變 得不容易折損且大幅提昇切削屑排出性而防止切削屑纏繞 ，即使是直徑〇.7mm以下（特別是0.4mm以下）之小徑鑽 頭，仍能延長折損壽命而實現穩定的鑽孔加工。 接著說明可證實本實施例的效果之實驗例。 第5圖的圖表，是讓第一扭轉角和第二扭轉角α2進 行各種改變而評價起因於切削屑排出性之耐折損性和切削 屑的纏繞狀態之實驗條件及實驗結果。該實驗所使用的鑽 頭，工具直徑3爲0.1111111，溝槽長1爲1.7111〇1，刀腹厚、前端 角等之第一扭轉角α !和第二扭轉角α 2以外的規格是相同 的數値。此外，第一扭轉角α ,和第二扭轉角α 2的連設部5 ，是設定在從工具最前端6起算0.4mm (溝槽長I的23.5%) 的位置，在工具主體1被覆有非晶質碳被膜。 在本實驗，是將難削材之半導體封裝用的PCB (基板 :厚0.1mm /表裏兩面Cu層）重疊八片，在其上面載置厚 0.1mm之樹脂被覆鋁板來作爲護板，爲了進行貫通孔加工 ，在前述PCB的下面配置一般使用之厚1.5 mm的紙酚醛材 來作爲墊板。又鑽頭（主軸）轉數爲250krpm，進給速度 爲2.5m/min，設定衝孔數爲8000次。 -19 - 201132430 如上述般，是在第一扭轉角和第二扭轉角α2以外 的規格設定爲相同數値之相同的實驗條件下進行比較評價 ，因此耐折損性是起因於不同扭轉角所造成的切削屑排出 性。 從第5圖可確認出，相較於第一扭轉角α 1爲25° (未達 30°)的鑽頭、從工具前端至基端其扭轉角爲一定的鑽頭 ，第一扭轉角α ,爲30°~45°、第二扭轉角α2成比第一扭轉 角〇：1大5°以上且第二扭轉角爲35°〜6 5°的鑽頭，起因於 切削屑排出性之耐折損性和切削屑的纏繞狀態良好。特別 是第一扭轉角α ,爲35°~4 5°，第二扭轉角α 2成比第一扭轉 角《，大10°以上且第二扭轉角α 2爲45°〜6 0°的鑽頭，起因於 切削屑排出性之耐折損性更良好。 如第6 ( a ) ( b )圖所示，在上述加工條件下加工後 的實施例（a)，在工具主體1(切削屑排出溝槽2)的基 端部幾乎看不到切削屑的纏繞。另一方面，在習知例（b )，可確認出在工具主體1(切削屑排出溝槽2)的基端部 發生多量切削屑的纏繞。在此，第6(a)圖是使用第5圖 中的實施例之第一扭轉角α ,爲35°且第二扭轉角α 2爲45° 的鑽頭。又第6(b)圖是使用第5圖中的習知例之從工具 前端至基端之扭轉角都是45°而爲一定的鑽頭。又依據該 習知例，有無法完成所設定的衝孔數之8000次鑽孔加工而 在中途就發生折損的情況，而第6 ( b )圖係顯示完成8000 次鑽孔加工的情況。該折損如前述般，是落下的切削屑塊 干涉鑽頭而引起的》 -20- 201132430 此外，本發明人等也嘗試使用無被覆的鑽頭而將上述 PCB重疊八片進行鑽孔加工，但確認出在加工初期的數次 衝孔就發生折損。因此在使用無被覆的鑽頭進行鑽孔加工 的情況，必須減少PCB的重疊片數，相較於使用被覆有非 晶質碳被膜之鑽頭的情況其效率較差。 【圖式簡單說明】 第1圖係PCB用鑽頭之槪略說明側視圖。 第2圖係習知例的放大槪略說明圖。 第3 ( a )圖係例示鑽頭的刃部C之基端部附近的切削 屑纏繞之相片，第3 ( b )圖係例示落到護板上之切削屑塊 的相片。 第4圖係本實施例的放大槪略說明側視圖。 第5圖係顯示實施例的實驗條件及實驗結果之圖表。 第6圖係顯示實施例（a )及習知例（b )之鑽孔加工 後的切削屑纏繞狀態之相片》 【主要元件符號說明】 1 :工具主體 2 :切削屑排出溝槽 3 :第一扭轉區域 4 :第二扭轉區域 5 :連設部 6 :工具最前端 -21 - 201132430 a i :第一扭轉角 a 2 :第二扭轉角 -22-[Technical Field] The present invention relates to a drilling tool used for drilling a non-ferrous material to be cut into a printed wiring board or the like. [Prior Art] The drilling process of the printed wiring board (PCB) is a drill comprising a main body portion A having a blade portion C and a shank portion B as shown in Fig. 1 . Although the size varies depending on the application, it is generally used with a drill having a diameter of 〇.7 mm or less. Specifically, in the blade portion C, as shown in FIG. 2, a spiral chip discharge groove 22 is formed on the outer periphery of the main body 20 from the tip end of the drill toward the base end side, and the chip discharge groove 22 is formed in the chip. The rake face and the intersecting ridge portion of the first flank face 24 provided at the tip end form a cutter 2 1 (see, for example, Patent Documents 1 and 2). Further, in the figure, reference numeral 25 denotes a second rake face which is connected to the rear side of the tool in the direction of rotation of the first rake face 24, d' is the diameter of the tool, and Γ is the groove length of the chip discharge groove, α, Torsion angle. In addition, as a film having abrasion resistance and weld resistance which is applied to a non-ferrous material to be cut into aluminum alloy, enamel, magnesium, copper, etc., an amorphous carbon film has been put to practical use, and is used for covering a drill bit. A cutting tool such as an end mill or a knife-replacement type cutting block (see, for example, Patent Document 3). However, 'PC 构成 is made by bonding copper and an insulating layer (made of glass fiber cloth impregnated with resin). In recent years, PCBs have been required to improve heat resistance and increase bending strength in order to further improve reliability. The thermal expansion is reduced. Therefore, the reliability of the glass fiber cloth and the resin constituting the PCB is increased to ensure reliability. However, in consideration of the case where the material to be drilled is to be drilled, the mechanical strength of the PCB of the above configuration is improved, and the wear of the drill bit is easily promoted, the bit breakage is easily caused in the drilling process, or the hole position is caused by excessive wear. The hole quality such as accuracy deteriorates. On the other hand, with the high density of the PCB, the required aperture (drill diameter) is getting smaller and smaller, and the drilling process with a diameter of less than 4 mm starts to become more. In addition, in the drilling process, the processing efficiency is considered. Generally, a plurality of PCBs of the same specification are overlapped and drilled. Therefore, in recent years, even small-diameter drills for PCBs used by P CBM workers having poor processing properties have required PCBs in order to reduce processing costs. The increase in the number of overlapping sheets requires an increase in the drilling life of the drill bit (the drilling process can be performed without breaking). [Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. 2006-55915 (Patent Document 3). Then, the inventors of the present invention attempted to drill a PCB by coating various nitride-based ceramic coatings such as TiN, TiCN, and TiAIN on a drill, but it was impossible to obtain a fracture-resistant effect with respect to the uncoated drill. -6- 201132430 fruit. In addition, a P c B drilling process in which a lubricative film such as an amorphous carbon film is coated on a drill is used, and it is confirmed that the fracture resistance is improved with respect to the uncoated drill, but there is still a shortage, and the drill is still insufficient. The processing conditions such as the number of revolutions of the drill bit and the feed rate during the hole processing, and the material of the PCB were also confirmed to be damaged earlier. The inventors of the present invention have completed the present invention by obtaining the findings described below in order to solve the above problems. As described above, in the drilling processing step, in consideration of the processing efficiency, generally, a plurality of sheets of the same size P c B are stacked to perform drilling processing. Specifically, in general, on a PCB in which a plurality of sheets overlap each other, a shield (aluminum plate or a resin-coated aluminum plate coated with a resin) is placed for drilling to improve the centripetality of the drill. The resin-coated aluminum sheet has a centripetal effect that is better than that of the aluminum sheet and contributes to the improvement of the bit breakage. Therefore, it is often used for drilling a small diameter drill having a diameter of 0.4 mm or less. However, in the case where the resin-coated aluminum plate is used as the shield for the drilling process, the entanglement of the chips is remarkably generated in the vicinity of the base end portion of the blade portion C of the drill, and the resin is more viscous than in the case of using the aluminum plate. The thicker the resin to be coated, the higher the tendency of the aforementioned chips to entangle. This is because the chips generated during the drilling process are usually sucked out by a chip suction function attached to the drilling machine and are carried out to a predetermined dust box. When the resin is coated with an aluminum plate, it is subjected to drilling. The heat-cut and softened resin is introduced into the chip discharge groove together with the chips, and the resin sticks the drill bit and the cutting chips to the 201132430 near the base end of the blade C, and continues to repeatedly drill. In the processing, the amount of winding of the chips increases the amount of winding of the chips, which varies depending on the machining conditions such as the number of revolutions of the drill and the feed speed during drilling, and the material of the PCB, but as shown in Figure 3 (a) It is obvious that the winding of the chips is generated, and the chips are wound in the subsequent drilling process, and the chips (chips) are detached from the drill due to vibration or the like, and cannot be attracted even by the aforementioned suction function. The drill bit that falls on the guard plate and then is drilled will be interfered by the falling chip, and the hole position accuracy will be deteriorated and the drill bit will be broken. Figure 3(b) illustrates a chip that falls onto the fender. The inventors of the present invention have found that in the case where only the lubricative film is coated, the entanglement of the chips is remarkably generated as compared with the uncoated bit, and the problem of the broken chips is caused by the problem of the falling chips. Stable, and there may be cases of early damage. In view of the above circumstances, the present invention provides a drilling tool which is excellent in practicality, which is coated with a lubricating coating, and the torsion angle of the chip discharge groove is changed in the middle, thereby making it difficult to be broken and greatly improved. The chip discharge is prevented and the chips are prevented from being entangled. Even a small-diameter drill having a diameter of 7.7 mm or less (especially 0.4 mm or less) can extend the breakage life and achieve stable drilling. The gist of the present invention will be described with reference to the accompanying drawings. A drilling tool is formed on the outer circumference of the tool main body 1 from the tool front end toward the base end side, or a plurality of spiral chip discharge grooves 2, and the chip discharge groove 2 is covered with a lubricating film. The driller 201132430 is characterized in that the chip discharge groove 2 is provided with: a stomach; a first torsion region 3 of a torsion angle ct 1 , and a tool base end side connected to the first torsion region 3 and having The second torsion region 4 of the second torsion angle α 2 (larger than the aforementioned first column ^ _ α 1 ). Further, in the drilling tool according to claim 1, the wet/slip film is an amorphous carbon film. Further, in the drilling tool according to claim 1, the angles of the first 丨 转 corner !: and the second torsion angle "2" are set to be in the first torsion region 3 and the second torsion region 4, respectively. The connecting portion 5 is caused to fly out from the tool body 1 by forcing %_ along the discharge direction of the chips discharged from the cutting dust discharge groove 2. Further, in the drilling tool of claim 2, the angle of the first 丨 转 angle ^: and the second twist angle α: 2 are set to be in the first torsion region 3 and the second torsion region, respectively. The connecting portion 5 of the fourth portion forcibly changes the discharge direction of the chips discharged along the cutting dust discharge groove 2 and is scattered from the tool body 1. Further, in the drilling tool according to claim 3, the first torsion angle α is set to 30° to 45°, and the second torsion angle α 2 is set to be larger than the first torsion angle ^ by 5 degrees or more. And the aforementioned second torsion angle α2 is set to 35. ~65. . Further, in the drilling tool according to claim 4, the first torsion angle α is set to 30° to 45°, and the second torsion angle α 2 is set to be larger than the first torsion angle α1 by 5° or more, and The second twist angle α 2 is set to 35° to 65. . -9-201132430 Further, in the drilling tool of claim 3, the first torsion angle 011 is set to 35° to 45°, and the second torsion angle α2 is set to be 10° larger than the first torsion angle “ Above, the second torsion angle is set to 45. ~60°. Further, in the drilling tool according to claim 4, the first torsion angle α? is set to 35° to 45°, and the second torsion angle α 2 is set to be 10° larger than the first torsion angle 〇:1. The above, and the second torsion angle α 2 is set to 45. ~60°. Further, in the drilling tool according to claim 5, the connecting portion 5 of the first torsional region 3 and the second torsional region 4 is provided at a distance of 0.2 mm from the foremost end 6 of the tool to the chip discharge groove. In the boring tool according to claim 6, the arranging portion 5 of the first torsional region 3 and the second torsional region 4 is provided from the foremost end of the tool 6 In the boring tool of claim 7, the connecting portion 5 of the first torsional region 3 and the second torsional region 4 is in the range of 0.2 mm to 1/2 of the total length 1 of the chip discharge groove 2, In the boring tool of claim 8, the first torsional region 3 and the second portion are provided in a 1/2 position from the foremost end 6 of the tool to the full length 1 of the chip discharge groove 2 The connecting portion 5 of the torsion region 4 is provided at a 1/2 position from the tool leading end 6 to the full length 1 of the cutting dust discharge groove 2 - 10, 2011, 324, 530, and in the request 1 to 1 2 In a recorded drilling tool, the diameter of the tool is 〇.7mm to ί; Further, in the drilling tool according to any one of claims 1 to 2, the tool has a diameter of 0.4 mm to 'p. Further, in the drilling tool described in claim 14, the drilling tool is suitable for applying a workpiece to a workpiece using a shield. Further, in the drilling tool described in the claim 5, the shield is made of aluminum. Further, in the drilling tool according to claim 16, the thickness of the shield is 0.04 to 1.0 mm. Further, in the drilling tool according to claim 17, the workpiece is a printed wiring board provided with a copper box layer. Further, in the drilling tool according to claim 18, the copper foil layer has a thickness of 2 to 80 μm. According to the above configuration of the present invention, it is possible to provide a drilling tool which is extremely excellent in practicability, which is less likely to be broken and which greatly improves the discharge of the chips and prevents the chips from being entangled, even if the diameter is 0.7 mm or less (especially 〇.4 mm or less). ) The small diameter drill can still extend the damage life and achieve stable drilling. [Embodiment] A preferred embodiment of the present invention will be briefly described based on the drawings and in conjunction with the effects of the present invention. At least the lubricating -11 - 201132430 film of the amorphous carbon film is coated on the chip discharge groove 2 to improve the surface lubricity of the chip discharge groove, thereby cutting the chips generated by the drilling process. The angle becomes large and the chips become thin and long, and the surface lubricity is high, so that the chips are easily discharged toward the base end portion of the tool body 1 (the blade portion c of FIG. 1) along the chip discharge groove. It prevents chipping of the chips and becomes less likely to break. In addition, by reducing the twist angle of the front end of the tool, it is possible to prevent the chips from becoming too thin and long, making the chips thick and short, and not easily entangled in the tool body 1, and further ensuring a large cut. The knife edge angle of the knife prevents the cutter from being chipped and improves the hole position accuracy, making it less susceptible to breakage. In addition, by increasing the torsion angle α2 on the proximal end side of the tool, it is possible to improve the chip discharge property at the proximal end side of the chip discharge groove 2 and to improve the fracture resistance, and to cover the amorphous carbon film or the like. The effect of the lubricative film is to forcibly change the discharge direction of the chips which are smoothly discharged along the chip discharge groove 2, and to match the centrifugal force multiplication effect, so as to be scattered toward the outside of the tool body 1, and the entanglement of the chips can be prevented. , and achieve stable drilling process with long damage life. [Embodiment] A specific embodiment of the present invention will be described based on Figs. 4 to 6 . In the lubricative film covering drilling tool of the present embodiment, a plurality of spiral chip discharge grooves 2 are formed on the outer periphery of the tool body 1 from the tool tip toward the base end side, and the tool body 1 (chip discharge groove) a groove 2) a drilling tool including a lubricating coating; the chip discharge groove 2 includes: a first torsion region 3 having a first torsion angle “!, and a first torsion region connected to -12-201132430 The tool base end side of 3 has a second torsion region 4 having a second twist angle α 2 (larger than the aforementioned first twist angle α 1 ). Specifically, the drill bit of the embodiment has a tool diameter d of 0·1 mm, and is provided with two chip discharge grooves 2 having a groove length of 1 and 1.7 mm, and the inclined surface of the chip discharge groove 2 and The intersecting ridge portions of the front end surface of the tool body 1 (the first rake face) are respectively provided with cutters integrally formed with the tool body 1 described above, which are suitable for drilling of PCBs. The drilling process of the PCB, for example, as shown in the experimental example described later, the PCB for semiconductor packaging of a difficult-to-cut material (substrate: thick 〇lmm/two-sided Cu layer on the surface) is overlapped by eight sheets, and a thickness of 0.1 mm is placed thereon. The resin-coated aluminum plate was used as a shield. In order to perform through-hole processing, a paper phenolic material having a thickness of 1.5 mm which is generally used was placed as a backing plate on the lower surface of the PCB, and this was carried out in this state. Further, the thickness of the shield is appropriately set within the range of 0.04 to 1.0 mm. The thickness of the Cu layer of the PCB having a thickness of about 0.1 mm is usually about 2 to 80 / / m. More specifically, in the case of the above conditions, the entanglement of the chips is likely to occur, and in order to solve the problem, the tool shown in Fig. 2 is improved, that is, the tool body 1 is covered with an amorphous carbon film. The chip discharge groove 2 of the drill bit is provided with the aforementioned first torsion region 3 and the aforementioned second torsion region 4. Next, each part will be specifically described. The base material of the drill is made of a superhard alloy composed of a hard particle having a main component of WC and a binder of a main component of Co. The average particle diameter of the WC particles of the cemented carbide is Ο.Ι/im~2/ /m, Co content is 5 to 15 weight. /. At least the amorphous carbon film is coated on the chip discharge groove 2 of the tool body 1. From -13 to 201132430, the amorphous carbon film is hard, and it can suppress the tool wear and high lubricity, so that the chips can be easily discharged along the chip discharge groove toward the base end portion of one, thereby preventing chipping and chipping. damage. Further, in the present embodiment, the lubricative film is an amorphous carbon film composed of carbon atoms and high hardness carbon (DLC) having a Vickers hardness of 3,000 or more, but it is only required to be 2,000 or more. It is also possible to use a mixture of amorphous carbon DLC having a relatively low hardness and a substance (for example, a metal) to form another lubricating film such as chromium nitride. Further, in the present embodiment, although the amorphous carbon film is directly formed, for example, a lower film layer (base film, one or more of the groups 4a, 5a, 6a, and Si) or a plurality of elements or The amorphous carbon film may be formed on the layer of the film layer having a thickness of 200 nm or less and 1 nm or more. The layer is not limited to the above structure, and may be selected from the group consisting of a week, a group 6a, and a Si. One or two or more elements and a compound of one or more elements are selected. Further, in the present embodiment, when an amorphous carbon film is formed, a film forming apparatus using an arc ion plating method is used, and sputtering is performed. A PVD film forming apparatus such as a laser ablation method. The present embodiment will be further described below. The first torsion angle α is set to 30° to 45°. The discharge of the torsion chips of the drill bit and the rigidity of the drill bit are increased. The large twist angle is also due to the fact that it is not easy to fold to the tool body: the amorphous amorphous Vickers hardness is in the 丨 (DLC) or the film, and is also formed on the substrate by gold selected from cyclins. Below this is the lower layer of the film period 4a, 5a From the formation of nitrogen and carbon or the base film, but the angle can also be used, it will affect the cutting ability of the cutting -14-201132430, and conversely, the rigidity will be reduced. In the case of a small diameter drill bit, the fracture resistance of the drill bit is not only rigid but also susceptible to chip discharge. Therefore, it is preferable to set the torsion angle of the drill having a diameter of 0.7 mm or less (especially 0.4 mm or less) to be large, and generally set it to 4 (Γ~50°), the inventors, etc., in order to further improve the fracture resistance of the drill. For the torsion angle (the two opposite characteristics of the drill bit rigidity and the chip discharge performance), it is found that the aluminum plate or the resin-coated aluminum plate is placed on the object to be cut, and the inside and outside of the object to be cut are obtained. When a layer has a large amount of copper foil, if the torsion angle is less than 30°, the chip discharge property is deteriorated and the drill is easily broken. When the torsion angle is set to be larger than 45°, the chip discharge is caused. Although the improvement of the breakage resistance is improved, the chips of aluminum or copper become too thin and long, and the entanglement of the chips is likely to occur at the base end portion (the root portion) of the tool body 1 (the chip discharge groove 2). Furthermore, the inventors of the present invention have found that, in the case of a drill coated with a lubricative film such as an amorphous carbon film, the effect of improving the fracture resistance is improved compared to the uncoated drill. Producing cutting Winding 'The winding of the chips (chips) will fall on the guard plate, and the falling chips will interfere with the drill bit, resulting in poor hole position accuracy and the fracture life of the drill becomes unstable, and early breakage may occur. In consideration of these points, the torsion angle (first torsion angle α1) of the cutter portion at the tip end of the cutting tool is preferably 45. The following angles (30 to 45.) 'to ensure the discharge of the chips and The length of the chip is shortened, so that the chips are not easily entangled. More preferably, it is set to 3 5 to 4 5 . In the present embodiment, it is set to -15 - 201132430 35, and the second torsion angle α2 is set to be smaller than the first An angle of the torsion angle α 1 greater than 5° is set to 35° to 6 5°. By making the second torsion angle α2 larger than the first torsion angle α?, the base of the chip discharge groove 2 can be raised. In addition, the effect of covering the amorphous carbon film (lubricative film) can be along the first torsion region 3 (set to the first torsion angle a!) by the chip discharge property of the end side. Exhaust of the chips discharged smoothly from the chip discharge groove 2 In the direction, the chip discharge groove 2 to the second torsion region 4 (set to the second torsion angle α2) is forcibly changed, and the centrifugal force is multiplied to cause it to scatter toward the outside of the tool body 1 to prevent chipping. The entanglement makes the breakage life longer and more stable. When the angle difference between the first torsion angle ai and the second torsion angle α 2 is less than 5°, the effect of forcibly changing the direction in which the chips are discharged is poor, and it is not easy to make the chips. Further, when the second torsion angle α 2 is larger than 65°, the rigidity of the base end portion of the tool main body 1 is lowered, and the fracture resistance is deteriorated. More preferably, the first torsion angle is obtained. The angular difference between α! and the second torsion angle α2 is set to 10° or more, and the second torsion angle α 2 is set to 45° to 60°. In the present embodiment, the second torsion angle α2 is set to be the first torsion angle (35°) has an angular difference of 10° of 10°. In addition, in order to discharge the chips well, it is advisable to change the tool tip side as far as possible to the second torsion angle α 2 'Because the drill bit for general PC use must be re-honed for use (re-honing) The connecting portion 5 of a torsion region 3-16-201132430 and the second torsional region 4 is preferably set to a groove length of 2 mm from the foremost end 6 of the tool to the chip discharge groove in consideration of the amount of honing. 1 / 2 position. Further, if the position of the connecting portion 5 is set to a position rearward of the tool leading end 6 by a distance of 1 / 2 of the groove length 1, the portion of the first torsional region 3 having a small torsional angle is increased, causing chip discharge Sexual deterioration causes the risk of bit breakage to increase. In the present embodiment, the change point of the first torsion angle and the second torsion angle (the connecting portion 5) is set at a position of 2 3 . 5 % of the groove length 1 from the foremost end 6 of the tool (C !) . The drill according to the present invention is a hard coating film for drilling a non-ferrous material such as ρ c 且 and coated with a lubricative film such as an amorphous carbon film, and is preferably a hard material having a WC as a main component. A superhard alloy composed of a binder of particles and a main component is a material which can achieve a balance between hardness and toughness. If the average particle diameter of the WC particles is too small, it is difficult to uniformly disperse the WC particles in the binder, which tends to cause a decrease in the bending strength of the cemented carbide. On the other hand, if the WC particles are too large, the hardness of the superhard alloy is lowered. Further, if the Co content is too small, the flexural strength of the cemented carbide is lowered. Conversely, if the Co content is too large, the hardness of the superhard alloy is lowered. Therefore, the substrate is preferably used: a superhard alloy having an average particle diameter of wc particles of o.l " m and a Co content of 5 to 15% by weight. Further, in the case of difficult-to-cut materials such as PCBs, in order to perform stable drilling without film peeling, it is preferable to improve the adhesion between the substrate and the amorphous carbon film -17-201132430. A base film (a metal or a semimetal composed of one or two or more elements selected from Groups 4a, 5a, 6a and Si of Ti, Cr, Ta, etc.) is formed above the substrate. The amorphous carbon film is formed, whereby the adhesion between the substrate and the amorphous carbon film can be further improved. Further, the base film formed on the substrate may be one or more elements selected from Groups 4a, 5a, 6a and Si of the periodic table, and one or more elements selected from the group consisting of nitrogen and carbon. Compound. The purpose of providing the under film is to improve the adhesion between the substrate and the amorphous carbon film. If the thickness is too thick, the film thickness is preferably 200 nm or less and 1 nm or more. According to the above configuration, at least the lubricative film such as the amorphous carbon film is coated on the chip discharge groove 2, and the surface lubricity of the chip discharge groove can be improved, thereby causing the cutting by the drilling process. The shear angle of the chips becomes large and the chips become thin and long, and the surface is lubricated to facilitate the cutting of the chips along the chip discharge grooves toward the base end of the tool body 1 (the blade portion C of FIG. 1). The discharge of the parts prevents the chips from becoming clogged and becomes less likely to be broken. Further, by reducing the torsion angle αΐ of the tip end of the tool, it is possible to prevent the chips from becoming too thin and long, making the chips thick and short, and it is not easy to be wound around the tool body 1, and a larger cutter can be secured. The knife edge angle prevents the cutter from being chipped and improves the hole position accuracy, making it less likely to break. Further, by increasing the torsion angle α 2 on the proximal end side of the tool, it is possible to improve the chip discharge property at the proximal end side of the chip discharge groove 2 and to improve the fracture resistance, and to use the coated amorphous carbon film ( The effect of the lubricative film, -18-201132430 Forcibly changes the discharge direction of the chips discharged smoothly along the chip discharge groove 2, and mixes the effect of the centrifugal force to scatter toward the outside of the tool body 1. It prevents the winding of the cutting shoulder and realizes stable drilling with long service life. In this way, according to the present embodiment, it is possible to provide a drilling tool which is extremely excellent in practicability, and even in the case where a resin-coated nameplate is used as a shield, it is not easily broken and the chip discharge property is greatly improved to prevent the chip from being entangled. Even small diameter drills with a diameter of less than 7 mm (especially 0.4 mm or less) can extend the breakage life and achieve stable drilling. Next, an experimental example in which the effects of the present embodiment can be confirmed will be described. The graph of Fig. 5 is an experimental condition and an experimental result for evaluating the fracture resistance of the chip discharge property and the winding state of the chips by variously changing the first torsion angle and the second torsion angle α2. The drill used in this experiment has a tool diameter 3 of 0.1111111, a groove length of 1 of 1.7111〇1, a first twist angle α such as a blade thickness, a front end angle, and the like, and the specifications other than the second twist angle α 2 are the same number. value. Further, the connecting portion 5 of the first torsion angle α and the second torsion angle α 2 is set at a position of 0.4 mm (23.5% of the groove length I) from the foremost end 6 of the tool, and is covered with the tool body 1 Amorphous carbon film. In this experiment, a PCB for a semiconductor package for hard-to-cut materials (a substrate: a thickness of 0.1 mm / a Cu layer on both sides of the surface) is overlapped, and a resin-coated aluminum plate having a thickness of 0.1 mm is placed thereon as a shield. For the through hole processing, a paper phenolic material having a thickness of 1.5 mm which is generally used is disposed as a backing plate under the aforementioned PCB. Further, the number of revolutions of the drill (spindle) was 250 krpm, the feed rate was 2.5 m/min, and the number of punching holes was set to 8000. -19 - 201132430 As described above, comparative evaluation is performed under the same experimental conditions in which the specifications other than the first torsion angle and the second torsion angle α2 are set to the same number, and therefore the fracture resistance is caused by different torsion angles. Chip removal. It can be confirmed from Fig. 5 that the first torsion angle α is a drill having a torsion angle constant from the tip end of the tool to the base end as compared with the first torsion angle α 1 of 25° (less than 30°). 30°~45°, the second torsion angle α2 is a bit larger than the first torsion angle 〇: 1 by 5° and the second torsion angle is 35° to 6 5°, which is caused by the fracture resistance of the chip discharge and The winding state of the chips is good. In particular, the first torsion angle α is 35° to 45°, and the second torsion angle α 2 is a bit larger than the first torsion angle “, greater than 10° and the second torsion angle α 2 is 45° to 60°”. The fracture resistance due to chip discharge is better. As shown in Fig. 6(a)(b), in the embodiment (a) processed under the above-described processing conditions, almost no chipping was observed at the base end portion of the tool body 1 (chip discharge groove 2). Winding. On the other hand, in the conventional example (b), it was confirmed that a large amount of chips were entangled at the base end portion of the tool body 1 (chip discharge groove 2). Here, Fig. 6(a) is a drill using the first torsion angle α of the embodiment in Fig. 5, which is 35° and the second torsion angle α 2 is 45°. Further, Fig. 6(b) is a drill bit which is constant from the tip end of the tool to the base end by a conventional example in Fig. 5 and has a constant twist angle of 45°. Further, according to the conventional example, the 8000-hole drilling process in which the number of punched holes is set cannot be completed, and the breakage occurs in the middle, and the sixth (b) figure shows the case where 8000 drilling processes are completed. In the above-mentioned case, the inventors of the present invention have attempted to drill the eight pieces of the above-mentioned PCB by using the uncoated drill bit, but confirmed that the damage was caused by the interference of the falling chips. -20-201132430 The punching occurs several times in the initial stage of processing. Therefore, in the case of drilling using an uncoated drill, it is necessary to reduce the number of overlapping sheets of the PCB, which is inferior to the case of using a drill coated with an amorphous carbon film. [Simple description of the drawing] Fig. 1 is a side view showing the outline of the drill bit for the PCB. Fig. 2 is an enlarged schematic view showing a conventional example. Fig. 3(a) is a photograph showing the entanglement of chips near the base end portion of the blade portion C of the drill, and Fig. 3(b) is a photograph exemplifying the chips of the chip falling on the shield. Fig. 4 is an enlarged schematic side view showing the present embodiment. Fig. 5 is a graph showing experimental conditions and experimental results of the examples. Fig. 6 is a photograph showing the state in which the chips are wound after the drilling process of the embodiment (a) and the conventional example (b) [Explanation of main component symbols] 1: Tool body 2: chip discharge groove 3: a torsion region 4: a second torsion region 5: the connecting portion 6: the tool front end-21 - 201132430 ai: the first twist angle a 2 : the second twist angle 22-