201206595 六、發明說明： 【發明所屬之技術領域】 本發明，是關於鑽孔工具。 【先前技術】 對於印刷電路板（P C B )的鑽孔加工，是使用如第1 圖所示之由具有刃部C的鑽身部a和柄部b所構成的鑽 頭。鑽頭的尺寸是根據用途有各種的尺寸，但一般大多數 是使用直徑0.7mm以下的鑽頭。 具體而言’於刃部C’如第2圖所示是在本體20的 外圍從鑽頭前端朝基端側形成有螺旋狀的切屑排出槽22 ，於該切屑排出槽22的傾斜面和設置在前端的第一後隙 面之交叉稜線部是形成有切刃2 1 (例如參照專利文獻1、 2)。另’圖中’圖號25是連設在第—後隙面24之工具 旋轉方向後方側的第二後隙面，d’是工具直徑，1’是切屑 排出槽的溝槽長，α’是螺旋角。 此外’鋁合金、鈦、鎂' 銅等非鐵系被削材所適合之 具有耐磨損性和耐熔敷性的皮膜是以非晶質碳皮膜爲實用 性，其是使用做爲鑽頭或銑刀、刃頭交換型切削刀等切削 工具的被覆（例如參照專利文獻3 )。 然而，PCB是由銅和做爲絕緣層之含浸有樹脂的玻璃 布貼合構成，近年來的PCB ’爲了要更加提昇其可靠性， 是需要提昇耐熱性，加強彎曲強度及低熱膨脹化，因此大 多數是提高PCB構成用的玻璃布或樹脂的機械性強度， 201206595 藉此確保較高的可靠性。 不過，當考慮到PCB是做爲要進行鑽孔加工的被削 材時，上述構成的PCB會因爲機械性強度的提高相對地 容易促進鑽頭磨損，容易導致鑽孔加工中的鑽頭折損或過 度磨損造成孔位置精度等的孔品質變差。 另一方面，隨著PCB的高密度化，所要求的孔徑（ 鑽頭的直徑）是逐年小徑化，直徑爲〇.4mm以下的鑽孔 加工逐漸變多。 此外，於鑽孔加工步驟，考慮到加工效率，一般是將 相同規格的PCB複數片重疊後進行鑽孔加工。具體而言 ，一般是在複數片重疊的PCB上面載置有目的爲提高鑽 頭之求心性的抵接板即鋁板或表面被覆有樹脂之附帶樹脂 的鋁板之後進行鑽孔加工。附帶樹脂的鋁板是比鋁板提昇 求心性的效果高，此外爲了有助於鑽頭折損的改善，特別 是以使用在直徑〇.4mm以下之小徑鑽頭的鑽孔加工爲多 數。 近年來，針對上述加工性比較差的PCB之加工所使 用的PCB用小徑鑽頭，同樣地也以削減加工成本爲目的 要求能夠在PCB重疊片數增加及鑽頭不折損的狀況下進 行鑽孔加工又能夠延長鑽頭鑽孔的壽命。 不過，使用附帶樹脂之鋁板做爲抵接板進行鑽孔加工 時，是比使用鋁板進行鑽孔加工時，還會在鑽頭之刃部C 的基端部附近明確產生切屑之捲附殘屑，樹脂的黏性愈高 或被覆的樹脂厚度愈厚，產生上述切屑之捲附殘屑的傾向 -6- 201206595 愈高’以致難以實現上述的要求。 其原因是，通常鑽孔加工時產生的切 附屬的切屑吸取功能吸取，然後搬出至指 使用附帶樹脂之鋁板時，因鑽孔加工時的 軟化的樹脂會和切屑一起受到切屑排出槽 導致在刃部C的基端部附近產生鑽頭和切 持續重覆進行鑽孔加工勢必會造成切屑之 加。 切屑之捲附殘屑量，也會因爲鑽孔加 轉數或進刀速度的加工條件或PCB的材 但如第3 ( a )圖所示產生明顯的切屑之 因是該切屑之捲附殘屑在持續的鑽孔加工 振動等造成切屑（切屑塊）離開鑽頭，即 述吸取功能但切屑塊也不會被吸取以致切 板上，然後，正要鑽孔加工的鑽頭會因掉 導致孔位置精度變差或鑽頭折損。另，舞 示著掉落在抵接板上的切屑塊。 此外，例如：專利文獻4中，是針對 2個切屑排出槽的PCB鑽頭，揭示有下述 屑排出槽在從前端後退指定量的位置合流 後方的位置成爲1個溝槽，藉此提高剛性 屑的捲附，因此是無法滿足上述要求。 [先行技術文獻] 屑是利用鑽孔機 定的垃圾箱，但 切削熱而形成爲 的引導而排出， 屑的黏附作用， 捲附殘屑量的增 工時之鑽頭的旋 質而有所改變， 捲附殘屑，其原 中因某種因素的 使鑽孔機具有上 屑塊掉落在抵接 落的切屑塊干涉 5 3 ( b )圖中例 具有2個切任和 技術即是將各切 ，在比合流點還 ，但並未言及切 201206595 [專利文獻] [專利文獻1]日本特開昭56-39807號公報 [專利文獻2]日本特開2006_55915號公報 [專利文獻3]日本特開2001-341021號公報 [專利文獻4]日本特開昭2〇〇7_3〇7642號公報 【發明內容】 [發明欲解決之課題] 本發明是有鑑於上述現狀而爲的發明，目的是提供一 種能夠防止切屑捲附，即使是直徑爲〇. 7mm以下，特別 是〇.4mm以下的小徑鑽頭，也可成爲折損壽命長能夠實 現穩定的鑽孔加工又實用性極爲優秀的鑽孔工具。 [用以解決課題之手段] 以下是參照附圖對本發明的主旨進行說明。 本發明相關的鑽孔工具，是在工具本體1的前端設有 1個或複數切刃，於該工具本體1的外圍從工具前端朝基 端側設有複數螺旋狀切屑排出槽，該複數切屑排出槽是至 少包括1個主溝槽2a和1個副溝槽2b，在上述主溝槽2a 的途中部設有1個或複數副溝槽2b形成合流，其特徵是 於上述主溝槽2a及副溝槽2b的合流部6設置段差7。 此外’本發明相關的鑽孔工具，是於申請專利範圍第 1項記載的鑽孔工具中，其特徵爲，上述段差7是由上述 主溝槽2a和上述副溝槽2b之溝槽深度的差異形成。 -8- 201206595 另外’本發明相關的鑽孔工具，是於申請專利範圍第 1項記載的鑽孔工具中，其特徵爲，上述段差7是2μιη以 上。 此外’本發明相關的鑽孔工具，是於申請專利範圍第 2項記載的鑽孔工具中，其特徵爲，上述段差7是2μηι以 上。 另外，本發明相關的鑽孔工具，是於申請專利範圍第 3項記載的鑽孔工具中，其特徵爲，上述段差7是主溝槽 2a之溝槽深度的7 0%以下。 此外，本發明相關的鑽孔工具，是於申請專利範圍第 4項記載的鑽孔工具中，其特徵爲，上述段差7是主溝槽 2 a之溝槽深度的7 0 %以下。 另外，本發明相關的鑽孔工具，是於申請專利範圍第 1項至第6項任一項記載的鑽孔工具中，其特徵爲，將上 述主溝槽2a或上述副溝槽2b的螺旋角在工具前端側和工 具基端側形成爲不同，藉此使上述主溝槽2a和上述副溝 槽2b形成合流。 此外，本發明相關的鑽孔工具，是於申請專利範圍第 1項至第6項任一項記載的鑽孔工具中，其特徵爲，上述 合流部6是設置在距離工具前端有上述主溝槽2a之溝槽 長1的50%以下的位置。 另外，本發明相關的鑽孔工具，是於申請專利範圍第 7項記載的鑽孔工具中，其特徵爲，上述合流部6是設置 在距離工具前端有上述主溝槽2a之溝槽長1的50%以下 201206595 的位置。 此外’本發明相關的鑽孔工具，是於申請專利範圍第 8項記載的鑽孔工具中，其特徵爲，被覆有潤滑性皮膜。 另外’本發明相關的鑽孔工具，是於申請專利範圍第 9項記載的鑽孔工具中，其特徵爲，被覆有潤滑性皮膜。 此外，本發明相關的鑽孔工具，是於申請專利範圍第 1 〇項記載的鑽孔工具中，其特徵爲，上述潤滑性皮膜是 採用非晶質碳皮膜。 另外’本發明相關的鑽孔工具，是於申請專利範圍第 11項記載的鑽孔工具中，其特徵爲，上述潤滑性皮膜是 採用非晶質碳皮膜。 此外，本發明相關的鑽孔工具，是於申請專利範圍第 12項記載的鑽孔工具中，其特徵爲，工具直徑爲〇.7mm 以下。 另外’本發明相關的鑽孔工具，是於申請專利範圍第 13項記載的鑽孔工具中，其特徵爲，工具直徑爲〇.7mm 以下。 此外’本發明相關的鑽孔工具，是於申請專利範圍第 12項記載的鑽孔工具中，其特徵爲，工具直徑爲〇.4mm 以下。 另外’本發明相關的鑽孔工具，是於申請專利範圍第 13項記載的鑽孔工具中’其特徵爲，工具直徑爲〇.4mm 以下。 -10- 201206595 [發明效果] 本發明因是如以上所述的構成’所以就能夠防止切屑 捲附，即使是直徑0.7mm以下特別是〇.4mm以下的小徑 鑽頭，還是能夠成爲折損壽命長能夠實現穩定鑽孔加工之 實用性極佳的鑽孔工具。 【實施方式】 [發明之最佳實施形態] 以下，是根據圖面以揭示本發明作用的方式對本發明 之最佳實施形態進行簡單的說明。 在鑽孔加工時當工具前端部產生的切屑沿著切屑排出 槽排出時，切屑彼此會在主溝槽2a和副溝槽b的合流部 6產生衝撞，此外，又加上主溝槽2a和副溝槽b之合流 部6的段差7，是會使切屑於合流部6強制性（朝工具徑 方向）飛散難以到達工具基端部，因此就能夠防止工具基 端部的切屑捲附。 [實施例] 針對本發明具體性的實施例是根據第4圖〜第1 〇圖進 行說明。 本實施例的鑽孔工具，是在工具本體1的前端設有1 個或複數的切刃，於該工具本體1的外圍從工具前端朝基 端側設有複數螺旋狀切屑排出槽，該複數切屑排出槽是至 少包括1個主溝槽2a和1個副溝槽2b，在上述主溝槽2a -11 - 201206595 的途中部設有1個或複數副溝槽2b形成合流， 是於上述主溝槽2a及副溝槽2b的合流部6設置 具體而言，本實施例的鑽頭，工具直徑爲0 設有1條溝槽長1爲1.2 mm之主溝槽2a和與該 合流的副溝槽2b，在該主溝槽2a及副溝槽2b 和上述工具本體1之前端後隙面（第一後隙面） 線部是分別設有與工具本體1成爲一體的切刃， 使用在PCB的鑽孔加工。 該PCB的鑽孔加工，例如：如下述的實驗 是將難削材即半導體封裝用的PCB (基板：厚彦 表背兩面Cu層）5片重疊，在該上面載置厚度 附帶樹脂鋁板做爲抵接板，爲了能夠進行貫通孔 上述 PCB的下面配置一般做爲丟棄材使用； 1.5mm的紙酚材，於該狀態下進行鑽孔加工。抵 度是適當設定在〇.〇4~l.〇mm的範圍。此外，厚 程度之PCB的Cu層厚度通常爲2〜80μιη程度。 另，於本實施例中是針對具有2個切刃和2 出槽（1個主溝槽2a和1個副溝槽2b )的鑽頭 )進行說明，但對於形態爲只在主溝槽側設有切 刃鑽頭，或3片刃以上的鑽頭（例如具有1個主 個副溝槽的鑽頭）也是相同。 更具體地說，於上述條件之形態時’因容易 切屑的捲附殘屑，所以爲了解決該問題就對第2 工具進行了改良，所改良的構成爲是於工具本體 其特徵爲 段差7。 .075mm， 主溝槽2a 的傾斜面 之交叉稜 該鑽頭是 例所示， ^ 0.1mm/ 0 · 1 mm 的 加工，在 之厚度爲 接板的厚 度 0 · 1 mm 個切屑排 (2片刃 刃的1片 溝槽和2 產生上述 圖所示的 1被覆非 -12- 201206595 晶質碳皮膜，在鑽頭的主溝槽2a設置具有第一螺旋角 的第一螺旋區域3和連設在第一螺旋區域3的工具基端側 具有比第一螺旋角α 1還大之第二螺旋角αζ的第二螺旋 區域4(副溝槽2b的螺旋角α3爲一定）’使主溝槽2a 和副溝槽2b形成合流[參照第4圖、第5圖，另，第5 (a )圖〜第5(c)圖是第4圖前端部份從各種不同旋轉相位 看時的圖面。]。 另，也可構成爲並不是在主溝槽2a而是在副溝槽2b 或是在主溝槽2a及副溝槽2b的雙方設置第一螺旋區域和 第二螺旋區藉此形成合流（連設），亦可構成爲是將主溝 槽2a或副溝槽2b的螺旋角朝工具基端側逐漸（曲線性） 改變（變大）藉此形成合流，也可構成爲開始就先改變主 溝槽2a及副溝槽2b的螺旋角使該等形成合流。 此外，主溝槽2a和副溝槽2b之合流部6的段差7， 是以切屑的飛散效果爲目的利用主溝槽2a和副溝槽2b之 溝槽深度的不同形成，因此主溝槽2和副溝槽2b的溝槽 深度是沒有限定那一方爲較深。具體而言，當將主溝槽 2a的溝槽深度（主溝槽深度、主溝槽2a之工具半徑方向 最深距離）X形成爲比副溝槽2b的溝槽深度（副溝槽深 度、副溝槽2b之工具半徑方向最深距離）Y還深藉此形 成段差7時，於合流部6欲合流的切屑彼此會衝撞無法合 流’導致切屑往徑方向飛散。此外，當將副溝槽2b的溝 槽深度Y形成爲比主溝槽2a的溝槽深度X還深藉此形成 段差7時，副溝槽2b於合流部6會消失使切屑衝撞主溝 -13- 201206595 槽2a的壁，由於排出空間消失，因此切屑就會 飛散。 另外，於本實施例中，爲了避免以下詳細說 痕造成的折損危險性，是將副溝槽2b的溝槽深ί 爲比主溝槽2a的溝槽深度X還淺藉此形成段差 示第5 ( b )圖A-A剖面圖的第6圖]。 該段差7是以2μπι以上且爲主溝槽2a之溝 的70%以下爲佳。當上述斷差7未滿2μιη時， 主溝槽2a產生有磨石痕的可能性就高，應力會 磨石痕可能成爲折損的起點，以致折損的可能性 外工具剛性變差也會影響到孔位精度。本實施例 述段差7設定爲3 μηι(主溝槽2a之溝槽深度X ，本實施例2是將上述段差7設定爲5·2μιη(: 之溝槽深度X的64%)。另外，當上述段差7 槽2a之溝槽深度X的70%時，副溝槽2b會變太 能阻礙到需求最低限度的切屑排出性，因此並不 7圖中並未圖示，但將段差7設定爲主溝槽2a 度X的70%時鑽頭的實驗結果爲折損）。 另，於本申請中是將主溝槽2a和副溝槽2b 始點（離工具前端有Ο距離的位置）至合流結 工具前端有P距離的位置）爲止的區域爲合流部 ’於本申請該段差7的測定位置，是在主溝槽2 槽2b之合流開始點和合流結束點的中間位置Q 連設）中心點的位置。 往徑方向 明之磨石 t Y形成 7 [參照表 槽深度X 製造上於 集中在該 變高，此 1是將上 的 3 7 % ) 溝槽2a 大於主溝 淺，有可 理想（第 之溝槽深 的合流開 束點（離 6。此外 a和副溝 即合流（ -14- 201206595 此外，是以可使合流部6的基端位置（主溝槽2 a和 付溝槽2b的合流結束點）設置在距離工具前端有主溝槽 2a之溝槽長1的50%以下的位置爲條件來設定第一螺旋區 域3及第二螺旋區域4的各螺旋角及連設位置。該形態時 ，溝槽在距離工具前端超過溝槽長1之50%的區域就會成 爲1個使剛性提高，提昇孔位置精度。當將合流部6從工 具前端設置在比主溝槽2a的溝槽長1之50%還後方（基 端側）的位置時，溝槽容積會變大，導致工具的剛性變差 ，孔位置精度變差或導致折損的可能性變高。於本實施例 ，合流部6的基端位置是設定成位於距離工具前端有溝槽 長1之3 2 %的位置。 接著，是對各部進行具體性說明。 該鑽頭，其基材，是以WC爲主成份的硬質粒子和以 Co爲主成份的結合材所形成的超硬合金製，採用該超硬 合金之WC粒子的平均粒徑爲Ο.ίμηι〜2μιη且Co含有量其 重量％爲5〜15%的超合金基材，此外至少是在工具本體1 的切屑排出槽被覆有非晶質碳皮膜。非晶質碳皮膜因是爲 硬質所以能夠抑制工具的磨耗，此外又具有高的潤滑性容 易使切屑沿著切屑排出槽往工具本體1的基端側排出能夠 防止切屑堵塞因此就不易折損。 此外，本實施例中，潤滑性皮膜，是採用以碳原子爲 主體構成其維克氏硬度爲3 000以上之高硬度非晶質碳（ DLC)所形成的非晶質碳皮膜，但只要維克氏硬度爲2〇〇〇 以上，也可採用比較低硬度的非晶質碳（DLC )和其他物 -15- 201206595 質（例如金屬）之混合物所形成的皮膜，此外也可採用鉻 氮化物等其他的潤滑性皮膜。 另，本實施例中，非晶質碳皮膜是形成在基材正上方 ，但也可構成爲例如：是於基材正上方，形成有從週期表 之4a、5a、6a族及Si當中選出1種或2種以上之元素所 形成的金屬或半金屬所構成，其膜厚爲200nm以下且 lnm以上的下層皮膜層（底膜），然後在該下層皮膜層上 形成有上述非晶質碳皮膜。此外，下層皮膜層，並不限於 上述構成，也可採用從週期表之4a、5a、6a族及Si當中 選出1種或2種以上之元素和從氮及碳當中選出1種以上 之元素的化合物所構成的下層皮膜層。 此外，本實施例中，對於非晶質碳皮膜或底膜的成膜 ，是使用電弧離子鍍敷方式的成膜裝置，但也可使用濺鍍 方式或雷射燒蝕塗敷方式等PVD成膜裝置。 第一螺旋角（^是設定在30° ~4 5° 。螺旋角，是會 影響切屑的排出性和鑽頭剛性，當將螺旋角形成爲較大時 是可提昇切屑排出性，但相反地會和剛性降低有關。當構 成爲小徑鑽頭的形態時，鑽頭的耐折損性不只會受到剛性 的影響也容易受到切屑排出性的影響。因此，直徑爲 0.7mm以下，特別是爲〇.4mm以下之鑽頭的螺旋角是以 設定成較大爲佳，一般是設定在30° ~45° 。 本發明者等，爲了要更家提昇鑽頭的耐折損性，針對 鑽頭的剛性和切屑排出性之顯示相反特性的螺旋角進行重 覆硏究的結果，得知：當被削物上面載置有鋁板或附帶樹 -16- 201206595 脂鋁板時，或被削物的內外層等有較多的銅箔時，若是將 螺旋角爲未滿30° ，則切屑排出性會變差導致鑽頭容易 折損，若將螺旋角設定成比4 5 ° ，則因切屑排出性的提 昇是會造成耐折損性提昇，但會導致鋁或銅的切屑形成爲 過度薄又長，以致在工具本體1(切屑排出槽）的基端部 (根基部）容易產生切屑的捲附殘屑。 再加上，本發明者等，也査明：構成爲被覆有非晶質 碳皮膜等潤滑性皮膜的鑽頭時，其與沒有塗敷的鑽頭相比 是有提昇耐折損性的效果，但會明顯產生切屑的捲附殘屑 ，該切屑的捲附殘屑（切屑塊）會掉落在抵接板上，因掉 落的切屑塊有時會干涉到鑽頭造成孔位置精度變差或造成 鑽頭的折損壽命不穩定以致早期折損。 當考慮到該等因素時，切削執行用之工具前端的切刃 部份是以螺旋角（第一螺旋角副溝槽2b的螺旋角α 3 )爲45°以下的角度（30°〜45° )爲佳，藉此確保切 屑排出性的同時使產生的切屑較短不會有切屑捲附。再加 上，該螺旋角（第一螺旋角及副溝槽2b的螺旋角α3 )又以設定成30°〜45°爲更佳。本實施例中，主溝槽2a 的第一螺旋角α〗及副溝槽2b的螺旋角α 3是設定成38。 〇 第一螺旋角〇：2是設定成比第一螺旋角αι還大5。以 上的角度’並且是設定在35°〜65。。藉由將第二螺旋角 0：2形成爲比第一螺旋角αι還大，是能夠提高切屑排出 槽之基端側的切屑排出性能夠提昇耐折損性。 -17- 201206595 此外，利用被覆有非晶質碳皮膜（潤滑性皮膜）的效 果，是可使沿著設定成第一螺旋角之第一螺旋區域3 的切屑排出槽順暢排出的切屑排出方向強制性改變成往設 定成第二螺旋角α2之第二螺旋區域4的切屑排出槽，利 用與離心力的相乘效果使切屑往工具本體1的外方飛散， 從該點來看也是能夠防止切屑的捲附使折損壽命變長又穩 定。 當第一螺旋角和第二螺旋角α2的角度差未滿5° 時，強制性改變切屑排出方向的效果就會降低，螺旋角改 變所造成之切屑往工具本體1外方飛散的效果就會降低。 此外，當第二螺旋角α2比第一螺旋角大時工具本體1 之基端部的剛性會降低，導致耐折損性變差。 再加上，又以第一螺旋角α!和第二螺旋角α2的角 度差設定成10°以上，並且，第一螺旋角和第二螺旋 角《2的合計角度設定在45°〜60°爲更佳。本實施例中 ，第二螺旋角α2,是設定成與第一螺旋角0^(38° )有 17°之角度差的55° 。 另外，爲了良好排出切屑，是以盡可能在工具前端側 改變成第二螺旋角α2爲佳，但一般而言PCB用的鑽頭是 在使用後重新硏磨前端之後再做爲使用（再硏磨）’因此 第一螺旋區域3和第二螺旋區域4的連設部5’當考慮到 硏磨量時是以設定在距離工具前端〇.2mm以上且爲切屑 排出槽之溝槽長1的50%以下的位置爲佳。 於本實施例中，第一螺旋角αι和第二螺旋角α2的 -18- 201206595 變化點（連設部5)是設定在距離工具前端有溝槽 之20.8%的位置（（：1)。 本發明是以PCB等非鐵系被削材鑽孔加工等 之被覆有非晶質碳皮膜等潤滑性皮膜的鑽頭爲發明 但其基材，是以WC爲主成份的硬質粒子和以Co 份的結合材所形成的超硬合金其硬度和韌性均衡的 佳。 WC粒子的平均粒徑若太小，則難以使WC粒 分散在結合材中，容易導致超硬合金的抗折力降低 方面，WC粒子的平均粒徑若太大，則超硬合金的 降低。此外，C 0含有量若太少則會降低超硬合金 力，反之Co含有量若太多則會降低超硬合金的硬 此，基材是以WC粒子的平均粒徑爲0.1μηι~2μιη， 有量其重量％爲5~15%的超硬合金爲佳。 此外，針對PCB等難削材爲了要進行皮膜不 穩定的鑽孔加工，是需要更加提高基材和非晶質碳 緊密性。將Ti、Cr、Ta等週期表之4a、5a、6a族 Si當中選出1種或2種以上之元素所形成的金屬 屬做爲底膜成膜在基材正上方，然後在其上方成膜 碳皮膜，藉此就能夠使基材和非晶質碳皮膜之緊密 。此外，也可將從週期表之4a、5a、6a族及Si當 1種或2種以上之元素和從氮及碳當中選出1種以 素的化合物做爲底膜成膜在基材正上方。 底膜的成膜是以提昇基材和非晶質碳皮膜之緊 長度1 所使用 對象， 爲主成 材料爲 子均勻 0另一 硬度會 的抗折 度。因 Co含 剝落之 皮膜之 元素及 或半金 非晶質 性更高 中選出 上之元 密性爲 -19- 201206595 目的，若太厚就無意義，因此是以200nm以下且lnm以 上之膜厚爲佳。 本實施例是構成爲如以上所述，所以至少會因爲切屑 排出槽被覆有非晶質碳皮膜等潤滑性皮膜而使切屑排出槽 的表面潤滑性變高，因此鑽孔加工所產生之切屑的剪斷角 會變大使切屑變薄變長的同時，由於表面潤滑性高使切屑 沿著切屑排出槽容易往工具本體1(第1圖的刃部C)的 基端部排出，相對地就能夠防止切屑堵塞，使賺頭不易折 損。 此外，因是將工具前端的螺旋角及^3形成爲較 小，所以就能夠防止切屑變太薄長，使切屑變厚變短難以 捲附在工具本體1，再加上，還能夠將切刃的刃物角確保 成較大，因此能夠避免切刃破角能夠改善孔位置精度的同 時使鑽頭不易折損。 再加上，因是將工具基端側的螺旋角α2形成爲較大 ，所以就能夠提高切屑排出槽2之基端側的切屑排出性使 耐折損性提昇，並且，利用被覆有非晶質碳皮膜（潤滑性 皮膜）的效果，是可使沿著切屑排出槽順暢排出的切屑排 出方向強制性改變，利用與離心力的相乘效果使切屑往工 具本體1的外方飛散，防止切屑的捲附使折損壽命變長能 夠實現穩定的鑽孔加工。 另外，於鑽孔加工時當工具前端部產生的切屑會沿著 切屑排出槽排出時，切屑彼此會在主溝槽2a和副溝槽2b 的合流部6衝撞，此外，又加上主溝槽2a和副溝槽b之 -20- 201206595 合流部6的段差7 ’是會使切屑於合流部6強制性（朝工 具徑方向）飛散難以到達工具基端部’因此就能夠防止工 具基端部的切屑捲附。 基於此，本實施例的鑽孔工具’即使是在使用附帶樹 脂之鋁板做爲抵接板時，還是難以折損並且可使切屑排出 性飛躍性良好能夠防止切屑捲附’即使是直徑爲〇.7mm 以下，特別是〇 . 4mm以下的小徑鑽頭’也可使其成爲折 損壽命變長且孔位置精度良好能夠實現穩定的鑽孔加工又 實用性極爲優秀的鑽孔工具。 接著，是以本實施例的效果爲依據針對實驗例進行說 明。 第7圖，是表示使用主溝槽2a爲一定的溝槽深度X ，副溝槽2b的溝槽深度Y有所改變之鑽頭進行鑽孔加工 時評估其孔位置精度的實驗結果圖表。該實驗使用的鑽頭 ，是工具直徑爲〇.〇75mm，（主溝槽的）溝槽長1爲 1.2mm，比較例1是先前2片刃2溝槽形狀的鑽頭（2個 切屑排出槽的螺旋角都是45°不改變），比較例2(於主 溝槽和副溝槽的合流部沒有段差的例）、實施例1及實施 例2，是主溝槽2a的螺旋角α ! ' α 2爲3 8 ° 、5 5 ° ’副 溝槽2b的螺旋角a3爲3 8°不改變’其他：心厚、前端 角等，副溝槽2b的溝槽深度Y以外的規格是相同的値。 另，實施例1及實施例2之副溝槽2b的溝槽深度Y，都 是設定成比主溝槽2a的溝槽深度X還淺。此外，於工具 本體1是被覆有非晶質碳皮膜（DLC)。 -21 - 201206595 該實驗中，是將難削材即半導體封裝用的PCB (基板 :厚度0.1 mm/表背兩面Cu層）5片重疊然後在其上面載 置厚度0.1mm的附帶樹脂鋁做爲抵接板，爲了要能夠進 行貫通孔加工是在上述PCB的下面配置有一般使用之厚 度1.5mm的紙酚材做爲丟棄板。另外，鑽頭（心軸）的 旋轉數爲300krpm，進刀速度爲1.8m/min，設定擊數爲 10,000 擊。 根據第7圖、第8圖，確認出比較例1在實驗後半期 產生明顯的切屑捲附，在抵接板進入側有捲附的磨擦痕跡 及所捲附之切屑的掉落。接著，是確認出該等在抵接板進 入側表面形成凹凸，使鑽頭的附著性變差，導致鑽頭容易 彎曲。另一方面，根據第7圖、第10圖，確認出實施例 1及實施例2，因溝槽在工具基端側是成爲1個，所以工 具基端側的剛性高，不會產生上述問題，鑽頭不易彎曲， 又確認出當主溝槽、副溝槽深度差（段差）/主溝槽深度 爲7 0%以下時孔位置精度是會獲得改善。另，亦確認出當 主溝槽、副溝槽深度差（段差）/主溝槽深度超過70%時 孔位置精度是會變差。此外。根據第8圖〜第10圖，是確 認出切屑捲附量依照比較例1、比較例2、實施例的順序 變少，雖然未圖示但確認出實施例2的切屑捲附量是和實 施例1同等。因此，可確認出根據本實施例時與先前的鑽 頭相比是能夠改善捲附性。 【圖式簡單說明】 -22- 201206595 第1圖爲P c B用鑽頭的槪略說1明側面圖° 第2圖爲先前例的放大槪略說明圖。 第3(a)圖爲鑽頭刃部C基端部附近之切屑的捲附 殘屑的例示照片’第3(b)圖爲掉落在抵接板上的切屑 塊例示照片。 第4圖爲本實施例的刃部槪略說明圖。 第5圖爲第4圖前端部份的放大槪略說明圖。 第6圖爲第5(a)圖的A-A剖面圖。 第7圖爲表示實驗結果的圖表。 第8圖爲表示比較例1之切屑捲附狀態及加工後之抵 接板的照片。 第9圖爲表示比較例1之切屑捲附狀態的照片。 第1 〇圖爲表示實施例1之切屑捲附狀態及加工後之 抵接板的照片。 【主要元件符號說明】 1 :工具本體 2a :主溝槽 2 b :副溝槽 6 :合流部 7 :段差 1 :溝槽長 -23-201206595 VI. Description of the Invention: [Technical Field to Which the Invention Is Ascribed] The present invention relates to a drilling tool. [Prior Art] For the drilling of a printed circuit board (P C B ), a drill composed of a drill portion a having a blade portion C and a shank b as shown in Fig. 1 is used. The size of the drill bit is various depending on the application, but most of the drill bits are used with a diameter of 0.7 mm or less. Specifically, as shown in FIG. 2, in the blade portion C, a spiral chip discharge groove 22 is formed on the outer periphery of the body 20 from the tip end side of the drill toward the base end side, and the inclined surface of the chip discharge groove 22 is provided at the front end. The intersecting ridge portion of the first flank surface is formed with the cutting edge 21 (see, for example, Patent Documents 1 and 2). In the figure, the figure 25 is a second flank face connected to the rear side of the tool-rotation surface 24 in the direction of rotation of the tool, d' is the diameter of the tool, and 1' is the groove length of the chip discharge groove, α' It is a spiral angle. In addition, a film having wear resistance and weldability suitable for non-ferrous materials such as aluminum alloy, titanium, and magnesium 'copper is practical for amorphous carbon film, and it is used as a drill bit or A coating of a cutting tool such as a milling cutter or a blade-end type cutting blade (see, for example, Patent Document 3). However, the PCB is composed of copper and a glass cloth impregnated with resin as an insulating layer. In recent years, in order to further improve the reliability of the PCB, it is necessary to improve heat resistance, strengthen bending strength, and reduce thermal expansion. Most of them are mechanical strengths for improving the glass cloth or resin used for PCB construction, and 201206595 ensures high reliability. However, when considering that the PCB is used as a material to be drilled, the PCB constructed as described above is relatively easy to promote bit wear due to an increase in mechanical strength, and is liable to cause bit breakage or excessive wear in the drilling process. The quality of the hole causing the hole position accuracy or the like is deteriorated. On the other hand, as the density of the PCB is increased, the required aperture (diameter of the drill) is reduced in diameter year by year, and the drilling process having a diameter of less than 4 mm is gradually increased. In addition, in the drilling process step, in consideration of the processing efficiency, it is generally performed by stacking a plurality of PCBs of the same specification and then performing drilling. Specifically, it is generally performed by drilling an aluminum plate or a resin-attached aluminum plate whose surface is coated with a resin for the purpose of improving the centering of the drill. The aluminum plate with resin is more effective than the aluminum plate for improving the coreability, and in order to contribute to the improvement of the bit breakage, in particular, the drilling process using a small diameter drill having a diameter of 44 mm or less is used. In recent years, in order to reduce the processing cost, the small-diameter drill for PCB used for the processing of the PCB having poor workability is required to be drilled under the condition that the number of overlapping PCBs is increased and the drill is not broken. It also extends the life of the drill bit. However, when the aluminum plate with the resin is used as the abutting plate for drilling, when the aluminum plate is used for drilling, the scraps of the chips are clearly generated near the base end portion of the blade portion C of the drill. The higher the viscosity of the resin or the thicker the thickness of the resin to be coated, the higher the tendency of the above-mentioned chips to wrap the debris - the higher the height - 6 to 201206595, so that it is difficult to achieve the above requirements. The reason is that the cutting and sucking function which is usually generated during the drilling process is sucked and then carried out until the aluminum plate with the resin is used, and the softened resin during the drilling process is subjected to the chip discharge groove together with the chips. The generation of the drill bit near the base end of the portion C and the continuous repetition of the cutting process are bound to cause the addition of chips. The amount of debris attached to the chip is also due to the processing conditions of the hole or the speed of the hole or the material of the PCB, but the obvious chip is caused by the chip as shown in Figure 3 (a). The chips are subjected to continuous drilling and vibrations, etc., causing the chips (chips) to leave the drill bit, that is, the suction function, but the chip blocks are not sucked so that the cutting plates are formed, and then the drill bit being drilled may cause the hole position due to the drilling. The accuracy is deteriorated or the drill bit is broken. In addition, the dance blocks that fall on the abutment plate are danced. Further, for example, Patent Document 4 discloses a PCB drill for two chip discharge grooves, and discloses that the following chip discharge grooves become one groove at a position after the position where the predetermined amount is retracted from the front end, thereby increasing the rigidity. The attached volume is therefore unable to meet the above requirements. [Pre-Technical Literature] The swarf is a garbage bin that is set by a drilling machine, but is cut and guided by cutting heat, and the adhesion of the swarf is changed, and the spin of the drill is changed when the amount of scrap is increased. The coil is attached with debris, which is caused by some factor in the original machine. The drill has the upper chip falling on the chipping block that abuts the falling piece. 5 3 (b) The example has two cuttings and the technology is In the case of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity of the singularity [Problem to be Solved by the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an object of the present invention. A small-diameter drill having a diameter of 〇. 7 mm or less, particularly 〇.4 mm or less, can be used as a drilling tool which can achieve stable drilling and has excellent practicability. [Means for Solving the Problems] The gist of the present invention will be described below with reference to the drawings. In the drilling tool according to the present invention, one or a plurality of cutting edges are provided at the front end of the tool body 1. On the periphery of the tool body 1, a plurality of spiral chip discharge grooves are provided from the front end of the tool toward the base end side, and the plurality of chips are discharged. The groove includes at least one main groove 2a and one sub-groove 2b, and one or a plurality of sub-grooves 2b are formed in the middle of the main groove 2a to form a merged flow, which is characterized by the main groove 2a and The merging portion 6 of the sub-groove 2b is provided with a step 7. Further, the boring tool according to the first aspect of the invention is characterized in that the step 7 is the groove depth of the main groove 2a and the sub-groove 2b. Differences are formed. Further, the drilling tool according to the first aspect of the invention is characterized in that the step 7 is 2 μm or more. Further, the boring tool according to the second aspect of the invention is characterized in that the step 7 is 2 μm or more. Further, the boring tool according to the third aspect of the invention is characterized in that the step 7 is 70% or less of the groove depth of the main groove 2a. Further, the drilling tool according to the invention of claim 4 is characterized in that the step 7 is 70% or less of the groove depth of the main groove 2a. Further, the boring tool according to any one of the first to sixth aspects of the present invention is characterized in that the main groove 2a or the sub-groove 2b is spiraled. The corners are formed differently on the tool leading end side and the tool base end side, whereby the main groove 2a and the sub-groove 2b are joined together. The boring tool according to any one of claims 1 to 6, wherein the merging portion 6 is provided at the front end of the tool and has the main groove. The groove 2a has a groove length of 50% or less. Further, the boring tool according to the seventh aspect of the invention is characterized in that the merging portion 6 is disposed at a groove length of the main groove 2a from the front end of the tool. The location of 50% below 201206595. Further, the boring tool according to the eighth aspect of the invention is characterized in that the boring tool according to the eighth aspect of the invention is characterized in that it is coated with a lubricating film. Further, the boring tool according to the invention of claim 9 is characterized in that the boring tool according to claim 9 is coated with a lubricating film. Further, the drilling tool according to the first aspect of the invention is characterized in that the lubricating film is made of an amorphous carbon film. Further, the boring tool according to the invention of claim 11 is characterized in that the lubricating film is made of an amorphous carbon film. Further, the boring tool according to the invention of claim 12 is characterized in that the tool diameter is 〇.7 mm or less. Further, the boring tool according to the invention of claim 13 is characterized in that the tool diameter is 〇.7 mm or less. Further, the boring tool according to the invention is the boring tool according to claim 12, characterized in that the tool diameter is 〇.4 mm or less. Further, the boring tool according to the invention is the boring tool according to the thirteenth aspect of the invention, wherein the tool diameter is 〇.4 mm or less. -10- 201206595 [Effect of the Invention] Since the present invention is configured as described above, it is possible to prevent the chip from being wound up, and even a small-diameter drill having a diameter of 0.7 mm or less, particularly 〇.4 mm or less, can be used for a long service life. A highly practical drilling tool that enables stable drilling. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the invention will be briefly described based on the drawings. When the chips generated at the front end portion of the tool are discharged along the chip discharge groove during the drilling process, the chips collide with each other at the joining portion 6 of the main groove 2a and the sub groove b, and further, the main groove 2a is added. The step 7 of the merging portion 6 of the sub-grooves b makes it difficult for the chips to be converge in the merging portion 6 (toward the tool diameter direction) and is difficult to reach the tool base end portion. Therefore, it is possible to prevent the chip from being attached to the tool base end portion. [Embodiment] An embodiment of the present invention will be described with reference to Figs. 4 to 1 . The drilling tool of this embodiment is provided with one or a plurality of cutting edges at the front end of the tool body 1. On the periphery of the tool body 1, a plurality of spiral chip discharge grooves are provided from the front end of the tool toward the base end side, and the plurality of chips are provided. The discharge groove is composed of at least one main groove 2a and one sub-groove 2b, and one or a plurality of sub-grooves 2b are formed in the middle of the main groove 2a-11 - 201206595 to form a merged flow. Specifically, the drill bit of the embodiment 2 has a tool diameter of 0, and is provided with a main groove 2a having a groove length of 1 mm and a sub-groove merged therewith. 2b, the main groove 2a and the sub-groove 2b and the front end flank surface (first flank surface) of the tool body 1 are respectively provided with cutting edges integrated with the tool body 1, and are used on the PCB. Drilling processing. For the drilling of the PCB, for example, the following experiment is performed by superimposing five pieces of PCBs (substrate: two layers of Cu on the back side of the thick surface) which are difficult to cut, that is, semiconductor packaging, on which the thickness of the resin-coated aluminum plate is placed. In order to enable the through hole, the lower surface of the PCB is generally used as a discard material; the 1.5 mm paper phenol material is drilled in this state. The offset is appropriately set in the range of 〇.〇4~l.〇mm. Further, the thickness of the Cu layer of the thick PCB is usually about 2 to 80 μm. Further, in the present embodiment, a description will be given of a drill having two cutting edges and two outlet grooves (one main groove 2a and one auxiliary groove 2b), but the configuration is only on the main groove side. A cutting bit, or a drill with more than three blades (for example, a drill having one main sub-groove) is also the same. More specifically, in the case of the above-described condition, the second tool has been improved in order to solve the problem because the chips are easily attached to the chip, and the improved structure is such that the tool body has a step of 7. .075mm, the intersection of the inclined faces of the main groove 2a. The drill is shown in the example, ^ 0.1mm / 0 · 1 mm, the thickness of the plate is 0 · 1 mm chip rows (2 blades) 1 groove and 2 produce the 1 coated non-12-1206506595 crystalline carbon film shown in the above figure, and the first spiral region 3 having the first helix angle is disposed in the main groove 2a of the drill bit and is connected to the first The tool base end side of the spiral region 3 has a second spiral region 4 of a second helix angle αζ larger than the first helix angle α 1 (the helix angle α3 of the sub-groove 2b is constant) 'to make the main groove 2a and the pair The grooves 2b are joined together [see Figs. 4 and 5, and the fifth (a) to (c)th drawings are the drawings of the front end portion of Fig. 4 when viewed from various rotation phases.]. Alternatively, the first spiral region and the second spiral region may be disposed not on the main trench 2a but in the sub trench 2b or on both the main trench 2a and the sub trench 2b. The configuration may be such that the spiral angle of the main groove 2a or the sub-groove 2b is gradually (curved) toward the tool base end side to form a confluence. Alternatively, the spiral angles of the main grooves 2a and the sub-grooves 2b may be changed to form a confluence at the beginning. Further, the step 7 of the confluence portion 6 of the main grooves 2a and the sub-grooves 2b is scattered by the chips. For the purpose of the effect, the groove depths of the main groove 2a and the sub-trench 2b are differently formed, and therefore the groove depths of the main groove 2 and the sub-groove 2b are not limited to the one side. Specifically, when The groove depth of the main groove 2a (the depth of the main groove, the deepest distance in the tool radius direction of the main groove 2a) X is formed to be the groove depth of the sub groove 2b (the depth of the sub groove, the tool radius of the sub groove 2b) When the depth is the deepest distance Y, the depth of the step 7 is formed, and the chips to be joined at the merging portion 6 collide with each other and cannot merge. This causes the chips to scatter in the radial direction. Further, when the groove depth Y of the sub-groove 2b is formed as When the step depth 7 is formed deeper than the groove depth X of the main groove 2a, the sub-groove 2b disappears at the merging portion 6 so that the chips collide with the wall of the main groove-13-201206595 groove 2a, and the swarf is removed due to the disappearance of the discharge space. It will fly. In addition, in this embodiment, in order to avoid the following details The risk of breakage caused by the fine marks is that the groove depth of the sub-groove 2b is shallower than the groove depth X of the main groove 2a, thereby forming a segment difference. The fifth aspect of the cross-sectional view of Fig. 5(b)AA is shown. The step 7 is preferably 2 μm or more and 70% or less of the groove of the main groove 2a. When the step 7 is less than 2 μm, the main groove 2a is likely to have a grindstone mark. The stress will cause the grindstone to become the starting point of the breakage, so that the possibility of the damage of the outer tool will also affect the accuracy of the hole position. The step difference 7 in this embodiment is set to 3 μηι (the groove depth X of the main groove 2a, In the second embodiment, the above-described step 7 is set to 5·2 μm (: 64% of the groove depth X). Further, when the step 7 of the groove 7 is 2% of the groove depth X, the sub-groove 2b becomes too much to hinder the minimum chip discharge property, so it is not shown in the figure, but the step is not shown. 7 When the main groove is set to 70% of the degree Xa X, the experimental result of the drill is broken. In the present application, the region from the start point of the main groove 2a and the sub-groove 2b (the position at which the distance from the tip of the tool is separated to the position at which the tip end of the merging tool is P) is the merging portion. The measurement position of the step 7 is a position at which the center point is connected to the intermediate position Q of the joining start point of the main groove 2 groove 2b and the joining end point. In the direction of the radial direction, the grinding stone t Y is formed 7 [Refer to the depth of the surface groove X, which is concentrated on the height, and this 1 is the upper 3 7 %.) The groove 2a is shallower than the main groove, and is ideal (the first groove) Convergence opening point of the groove depth (from 6. In addition, the a and the sub-ditch are merged (-14-201206595. In addition, the base end position of the merging portion 6 is completed (the merging of the main groove 2a and the groove 2b is completed) In order to set the helix angle and the connection position of the first spiral region 3 and the second spiral region 4 on the condition that the tip end of the tool has 50% or less of the groove length 1 of the main groove 2a. The groove is increased in rigidity in the region where the front end of the tool exceeds 50% of the groove length by one, and the position of the groove is increased. The position of the merging portion 6 is longer than the groove of the main groove 2a. When the position of 50% is still rearward (base end side), the groove volume becomes large, and the rigidity of the tool is deteriorated, and the hole position accuracy is deteriorated or the possibility of breakage becomes high. In this embodiment, the merging portion is increased. The base end position of 6 is set to be located at a position 2 to 2 % of the groove length from the front end of the tool. Specifically, the specific part of each part is described. The base material of the drill is made of a super-hard alloy formed of a hard particle containing WC as a main component and a bonding material containing Co as a main component, and the WC of the super hard alloy is used. The superalloy base material having an average particle diameter of the particles of Ο.ίμηι 2 2 μιη and a Co content of 5 to 15% by weight, and at least the amorphous carbon film coated on the chip discharge groove of the tool body 1 is amorphous. Since the carbonaceous carbon film is hard, it can suppress the wear of the tool, and the high lubricity is easy to cause the chips to be discharged to the base end side of the tool body 1 along the chip discharge groove, thereby preventing chip clogging and thus being less likely to be broken. In the examples, the lubricating film is an amorphous carbon film formed of a high hardness amorphous carbon (DLC) having a Vickers hardness of 3,000 or more mainly composed of carbon atoms, but only a Vickers hardness. For a thickness of 2 Å or more, a film formed of a mixture of a relatively low hardness amorphous carbon (DLC) and another substance -15-201206595 (for example, a metal) may be used, and other materials such as chromium nitride may be used. In the present embodiment, the amorphous carbon film is formed directly above the substrate, but may be formed, for example, directly above the substrate, and formed from groups 4a, 5a, and 6a of the periodic table. And a metal or a semimetal formed of one or more elements selected from Si and having a film thickness of 200 nm or less and a lower film layer (base film) of 1 nm or more, and then formed on the lower film layer The amorphous carbon film is not limited to the above-described configuration, and one or two or more elements selected from Groups 4a, 5a, and 6a of the periodic table and Si may be selected and selected from nitrogen and carbon. A lower film layer composed of a compound of one or more elements. Further, in the present embodiment, the film formation apparatus using the arc ion plating method is used for film formation of the amorphous carbon film or the base film, but PVD formation such as sputtering method or laser ablation coating method may be used. Membrane device. The first helix angle (^ is set at 30° ~ 4 5°. The helix angle affects the discharge of the chip and the rigidity of the bit. When the helix angle is formed to be large, the chip discharge can be improved, but conversely When the rigidity is reduced, the fracture resistance of the drill is not only affected by the rigidity but also by the chip discharge property. Therefore, the diameter is 0.7 mm or less, especially 〇.4 mm or less. The helix angle of the drill bit is preferably set to be larger, and is generally set at 30° to 45°. The inventors of the present invention, in order to further improve the fracture resistance of the drill bit, have the opposite effect on the rigidity and chip discharge of the drill bit. As a result of repeated investigation of the helix angle of the characteristic, it is known that when the aluminum plate or the accompanying tree-16-201206595 fat aluminum plate is placed on the object to be cut, or when the inner and outer layers of the object to be cut have more copper foil, If the helix angle is less than 30°, the chip discharge property will be deteriorated and the drill bit will be easily broken. If the helix angle is set to be 4 5 °, the chip discharge resistance will increase, and the fracture resistance will be improved. Will lead to aluminum or The inventors of the present invention have been found to be excessively thin and long, so that the roots of the tool body 1 (the chip discharge groove) are likely to cause chipping debris. Further, the inventors have also found out that: When the drill is coated with a lubricative film such as an amorphous carbon film, it has an effect of improving the breakage resistance compared with a drill which is not coated. However, it is apparent that the chip is wound and the chip is wound. The attached debris (chip block) will fall on the abutment plate, because the falling chip block sometimes interferes with the bit to cause the hole position accuracy to deteriorate or the bit life of the bit is unstable and the early breakage is considered. In the case of other factors, the cutting edge portion of the tip end of the tool for cutting execution is preferably an angle (30° to 45°) at a helix angle (the helix angle α 3 of the first helix angle sub-groove 2b) of 45° or less. Thereby, the chip discharge property is ensured while the generated chips are short and the chips are not attached. Further, the helix angle (the first helix angle and the helix angle α3 of the sub-groove 2b) is set to 30°. 45° is more preferable. In this embodiment, the first helix angle of the main groove 2a The helix angle α 3 of α and the sub groove 2b is set to 38. The first helix angle 〇: 2 is set to be larger than the first helix angle α1 by 5. The angle "above" is set at 35° to 65. By forming the second helix angle 0:2 to be larger than the first helix angle α1, the chip discharge performance at the base end side of the chip discharge groove can be improved, and the fracture resistance can be improved. -17- 201206595 The effect of coating the amorphous carbon film (lubricating film) is to forcibly change the direction in which the chips are discharged smoothly along the chip discharge groove of the first spiral region 3 set to the first helix angle. The chip discharge groove of the second spiral region 4 of the two helix angles α2 causes the chips to scatter toward the outside of the tool body 1 by the synergistic effect with the centrifugal force. From this point of view, it is also possible to prevent the winding of the chips and the fracture life becomes long. It is stable. When the angular difference between the first helix angle and the second helix angle α2 is less than 5°, the effect of forcibly changing the direction of chip discharge is reduced, and the effect of the chip caused by the change of the helix angle to the outside of the tool body 1 is reduce. Further, when the second helix angle α2 is larger than the first helix angle, the rigidity of the base end portion of the tool body 1 is lowered, resulting in deterioration of the fracture resistance. Further, the angle difference between the first helix angle α! and the second helix angle α2 is set to 10° or more, and the total angle of the first helix angle and the second helix angle “2 is set at 45° to 60°. For better. In the present embodiment, the second helix angle α2 is set to 55° which is an angular difference of 17° from the first helix angle 0^(38°). In addition, in order to discharge the chips well, it is preferable to change the second helix angle α2 on the tool front end side as much as possible, but in general, the drill bit for the PCB is used after re-honing the front end after use (re-honing Therefore, the connecting portion 5' of the first spiral region 3 and the second spiral region 4 is set to be at a distance of more than 2 mm from the front end of the tool and a length of 1 of the groove of the chip discharge groove when considering the amount of honing. The position below % is preferred. In the present embodiment, the -18-201206595 change point (connecting portion 5) of the first helix angle α1 and the second helix angle α2 is set at a position (.: 1) which is 20.8% from the tip of the tool. The present invention is a drill which is coated with a non-ferrous-based material such as a PCB and is coated with a lubricating film such as an amorphous carbon film. However, the substrate is a hard particle containing a WC as a main component and a Co part. The superhard alloy formed by the bonding material has a good balance of hardness and toughness. If the average particle diameter of the WC particles is too small, it is difficult to disperse the WC particles in the bonding material, which tends to cause a decrease in the folding resistance of the superhard alloy. If the average particle diameter of the WC particles is too large, the hardness of the superhard alloy is lowered. In addition, if the content of C 0 is too small, the strength of the superhard alloy is lowered, and if the content of Co is too large, the hardness of the super hard alloy is lowered. The base material is preferably a superhard alloy in which the average particle diameter of the WC particles is 0.1 μm to 2 μm, and the weight % is 5 to 15%. In addition, for the difficult-to-cut materials such as PCB, in order to perform the film unstable Hole processing is needed to improve the tightness of the substrate and amorphous carbon. Ti, Cr Metals formed by selecting one or more elements of Si, 4a, 5a, and 6a of the periodic table of Ta, etc., are formed as a base film directly on the substrate, and then a carbon film is formed thereon. This makes it possible to make the substrate and the amorphous carbon film tight. In addition, one or two or more elements of Groups 4a, 5a, and 6a of the periodic table and Si may be selected from nitrogen and carbon. The compound of the element is used as the base film to form the film directly above the substrate. The film formation of the base film is to use the object of the tight length of the substrate and the amorphous carbon film, and the main material is sub-uniform 0. The degree of flexural rigidity. The elemental density of the film containing Co and the semi-gold amorphous is -19-201206595. If it is too thick, it is meaningless, so it is below 200nm. In addition, the film thickness of the chip discharge groove is increased, and at least the lubricant discharge film such as the amorphous carbon film is coated on the chip discharge groove to increase the surface lubricity of the chip discharge groove. Therefore, the cutting angle of the chips generated by the drilling process will become larger and cut. At the same time, since the surface is lubricated, the chip is easily discharged to the base end portion of the tool body 1 (the blade portion C of the first drawing) along the chip discharge groove, so that the chip clogging can be prevented relatively, and the profit is difficult. In addition, since the helix angle and the ^3 of the tool tip are formed to be small, it is possible to prevent the chips from becoming too thin and long, and it is difficult to wrap the chips in the tool body 1 by adding thick and short chips, and The blade angle of the cutting edge is ensured to be large, so that it is possible to prevent the cutting edge from being broken and the hole position accuracy is improved, and the drill bit is not easily broken. Further, since the helix angle α2 of the tool base end side is formed to be large, Therefore, the chip discharge property of the base end side of the chip discharge groove 2 can be improved, and the fracture resistance can be improved, and the effect of coating the amorphous carbon film (lubricating film) can be smoothly discharged along the chip discharge groove. The direction in which the chips are discharged is forcibly changed, and the effect of multiplying by the centrifugal force causes the chips to scatter toward the outside of the tool body 1, thereby preventing the winding of the chips and making the life of the breakage longer, thereby achieving stable drilling. Further, when the chips generated at the front end portion of the tool are discharged along the chip discharge groove during the drilling process, the chips collide with each other at the joining portion 6 of the main groove 2a and the sub groove 2b, and the main groove is added. 2a and sub-groove b -20-201206595 The step 7' of the merging portion 6 is such that the chips are forced in the merging portion 6 (toward the tool diameter direction) and it is difficult to reach the end of the tool base. Therefore, the tool base end can be prevented. The chip is attached. Based on this, the drilling tool of the present embodiment is difficult to break even when the aluminum plate with resin is used as the abutting plate, and the chip discharge property is excellent, and the chip winding can be prevented from being attached even if the diameter is 〇. 7mm or less, in particular, a small-diameter drill having a diameter of 4 mm or less can also be used as a drilling tool which is excellent in the fracture life and has excellent hole position accuracy, and is capable of achieving stable drilling and excellent practicality. Next, an experimental example will be described based on the effects of the present embodiment. Fig. 7 is a graph showing experimental results for evaluating the accuracy of the hole position when the drill is drilled using the groove depth X of the main groove 2a and the groove depth Y of the sub groove 2b. The drill used in this experiment was a tool having a diameter of 〇.〇75 mm and a groove length of 1 (main groove) of 1.2 mm. Comparative Example 1 was a drill bit of the previous two blades 2 groove shape (the spiral of two chip discharge grooves) The angles are all unchanged at 45°), Comparative Example 2 (an example in which the intersection of the main groove and the sub-groove has no step), and the first embodiment and the second embodiment are the helix angle α of the main groove 2a. 2 is 3 8 °, 5 5 ° 'The helix angle a3 of the sub-groove 2b is 3 8° does not change 'others: the core thickness, the front end angle, etc., and the specifications other than the groove depth Y of the sub-groove 2b are the same. . Further, the groove depths Y of the sub-grooves 2b of the first embodiment and the second embodiment are set to be shallower than the groove depth X of the main grooves 2a. Further, the tool body 1 is covered with an amorphous carbon film (DLC). -21 - 201206595 In this experiment, five pieces of PCBs (substrate: thickness: 0.1 mm/back surface Cu) of the semiconductor package for hard-to-cut materials were stacked, and then a resin aluminum with a thickness of 0.1 mm was placed thereon. In order to enable the through hole processing, a paper phenol material having a thickness of 1.5 mm which is generally used is disposed as a discarding plate in the lower surface of the above-mentioned PCB. In addition, the number of revolutions of the drill (mandrel) was 300 krpm, the feed speed was 1.8 m/min, and the number of strokes was set to 10,000 strokes. According to Fig. 7 and Fig. 8, it was confirmed that Comparative Example 1 produced a significant chip wrap in the latter half of the experiment, and there was a rubbing trace attached to the entry side of the abutting plate and a drop of the attached chip. Then, it was confirmed that the unevenness was formed on the surface on the side where the contact plate entered, and the adhesion of the drill was deteriorated, which caused the drill to be easily bent. On the other hand, according to Fig. 7 and Fig. 10, it was confirmed that in the first embodiment and the second embodiment, since the groove is one on the tool base end side, the rigidity of the tool base end side is high, and the above problem does not occur. The drill bit is not easily bent, and it is confirmed that the hole position accuracy is improved when the main groove and the sub groove depth difference (step difference) / the main groove depth is 70% or less. Further, it was confirmed that the hole position accuracy deteriorates when the main groove and the sub groove depth difference (step difference) / the main groove depth exceeds 70%. Also. In the eighth to tenth drawings, it was confirmed that the amount of the chip winding amount was reduced in accordance with the order of the comparative example 1, the comparative example 2, and the example, and the amount of the chip winding amount of the second embodiment was confirmed and implemented. Example 1 is equivalent. Therefore, it was confirmed that the curling property can be improved as compared with the prior drill head according to the present embodiment. [Simple description of the drawing] -22- 201206595 Fig. 1 is a schematic view of a bit for the P c B. Fig. 2 is an enlarged schematic view of the previous example. Fig. 3(a) is an exemplified photograph of the wound debris of the chip near the base end portion of the drill blade portion C. Fig. 3(b) is a photograph of a chip block which is dropped on the abutment plate. Fig. 4 is a schematic explanatory view of the blade portion of the embodiment. Fig. 5 is an enlarged schematic illustration of the front end portion of Fig. 4. Fig. 6 is a cross-sectional view taken along line A-A of Fig. 5(a). Figure 7 is a graph showing the results of the experiment. Fig. 8 is a photograph showing the state of the chip winding of Comparative Example 1 and the abutting plate after the processing. Fig. 9 is a photograph showing the state of the chip winding of Comparative Example 1. Fig. 1 is a photograph showing the state of the chip winding of the first embodiment and the abutment plate after the processing. [Description of main component symbols] 1 : Tool body 2a : Main groove 2 b : Sub-groove 6 : Confluence part 7 : Step difference 1 : Groove length -23-