200306897 Π) 玖、發明說明 【發明所屬之技術領域】 本發明是關於工作件鑽鑿精密性孔用的鑽頭。 【先前技術】 電子零件等組裝用的印刷配線基板（以下稱印刷基板 )’是把銅箔疊層在強化纖維樹脂上而形成，在該印刷基 板上鑽鑿多數的貫穿孔後，透過電鍍處理使上述貫穿孔的 內壁形成有金屬電鍍層，接著又對該印刷基板表面的銅箔 進行蝕刻處理形成印刷電路，把該印刷電路和下層的銅箔 透過上述金屬電鍍層進行導通電源，接著又將L S I等電 子零件電焊在上述貫穿孔以形成印刷電路板。 然而，近年來，伴隨著電子機器的高性能化、小型化 ，對於印刷電路板要高密度組裝的需求有愈來愈高的趨勢 。根據該需求，在印刷基板之薄板化、高多層化、高密度 配線化前進的同時，加速要鑽鑿在上述印刷基板上之上述 貫穿孔的小徑化的腳步，因此，所使用之鑽頭勢必要小徑 另外，爲了要提昇作業效率和降低製造成本，對於在 印刷基板上的貫穿孔鑽鑿加工，是採複數片重疊該印刷基 板進行貫穿孔鑽鑿加工。因此’貫穿孔的縱橫比（針對孔 直徑之板厚的比）會變大，所以就需愈長的鑽頭。 此外，鑽頭若較長，相對地就需增加鑽頭所需要的強 度。因此，鑽頭就需具有高強度。 -5- (2) (2)200306897 另外，貫穿孔若較深，就愈容易產生孔洞彎曲。因此 ，鑽頭就需具有較高的筆直前進性。 此外’從電的觀點來看，鑽頭當場是要能鑽鑿出良好 的貫穿孔內壁粗糙度，即，鑽頭需能夠鑽鑿出貫穿孔內壁 粗糙度爲盡可能平滑的孔。 整理以上所述，可知對於最近之印刷基板加工用鑽頭 的要求，是其需爲具有鑽徑小，長度長，強度爲高強度， 具優良筆直前進性，並且所鑽鑿出的孔內壁粗糙度爲良好 的鑽頭。 另一方面，第1圖、第2圖爲習知印刷基板之貫穿孔 鑽鑿用的鑽頭3 3 (以下稱習知例）。 該習知例，是於前端設有鑽刃4 1，於外周面設有2 條螺旋狀鑽屑排出溝槽3 2，於該鑽屑排出溝槽3 2之間設 有導像部3 1，接著又在鄰接於導像部3 1的位置上設有比 鑽頭33直徑稍小直徑的鏟齒面34，該鏟齒面34之上述 導像部3 1的相反側形成有後跟3 5。此，鑽屑排出溝槽3 2 是從導像部3 1的端緣（外周轉角）往橫刃斜角3 6構成爲 正視直線形狀，從上述橫刃斜角3 6往上述後跟3 5 (後跟 面3 8 )因考慮到鑽屑的排出性能而構成爲剖視凹彎曲形 狀。 【發明內容】 〔本發明欲解決之課題〕 以該習知例的構成，要成爲如上述般之鑽徑小，長度 -6 - (3) (3)200306897 長，強度爲高強度，具優良筆直前進性，並且所鑽鑿出的 孔內壁粗糙度爲良好的鑽頭時會產生下述矛盾。 首先，當鑽頭3 3的鑽徑爲小直徑時，其強度當然會 降低。此外，鑽頭3 3，若長度愈長則愈容易彎曲，使其 筆直前進性降低。 因此，就會考慮將鑽頭3 3的芯厚（最細部份的直徑 )變大以提高強度，但於該狀況時，因鑽屑排出溝槽3 2 的深渡會變淺，而降低鑽屑的排出性能。 當鑽屑的排出性能降低時，鑽頭3 3將會以抱著鑽屑 在鑽屑排出溝槽3 2內的狀態進行鑽孔，鑽屑存在的部份 ，就會使貫穿孔的內壁面成粗糙的凹凸面，此外，作用於 鑽頭3 3上的負載會增加使鑽頭3 3折損。 因此，就習知例而言，若要加大鑽頭33的芯厚是有 所限度，所以就難以滿足上述條件（鑽徑小，長度長，強 度爲高強度，具優良筆直前進性，並且所鑽鑿出的孔內壁 粗糙度爲良好的鑽頭），尤其是無法同時達到筆直前進性 和所鑽鑿出的孔內壁粗糙度爲良好的雙方面條件。 本發明’ 7H有鑑於上述問題點而完成者，其目的在於 提供一種即使是鑽徑小、長度長，也能成爲高強度且可發 揮其筆直前進性’又能使所鑽鑿之孔的內壁粗糙度爲良好 之實用性極佳的鑽頭。 〔用以解決課題之手段〕 參考附圖對本發明之主旨進行說明。 -7 - (4) (4)200306897 鑽頭3是於其外周面設有螺旋狀之複數鑽屑排出溝槽 2 ’在該鑽屑排出溝槽2彼此之間§又有導像η卩1 ’又則 端設有鑽刃8的鑽頭，其特徵爲於鑽屑排出溝槽2的底部 設有往該鑽屑排出溝槽2延伸設置方向延伸的複數鑽屑導 引凹槽6、7。 此外，於申請專利範圍第1項所記載之鑽頭中’複數 鑽屑導引凹槽6、7，是以並設狀態設置，當中至少有一 條鑽屑導引凹槽的深度是設定成比其他的鑽屑導引凹槽的 深度還淺。 又，於申請專利範圍第1項所記載之鑽頭中，複數鑽 屑導引凹槽6、7，是從鑽屑排出溝槽2的前端開始延伸 設置，當中至少有一條鑽屑導引凹槽的長度是設定成比其 他的鑽屑導引凹槽的長度還短。 另外，於申請專利範圍第2項所記載之鑽頭中，複數 鑽屑導引凹槽6、7，是從鑽屑排出溝槽2的前端開始延 伸設置，當中至少有一條鑽屑導引凹槽的長度是設定成比 其他的鑽屑導引凹槽的長度還短。 此外，於申請專利範圍第1項所記載之鑽頭中，鑽屑 排出溝槽2是設置成三條；於該鑽頭3的前端部中，爲各 條導像部1之前端面的刃腹4，是與所鄰接導像部1的刃 腹4交叉而形成三條橫刃5，該三條橫刃5的交點構成著 前端尖銳部。 另外，於申請專利範圍第2項所記載之鑽頭中，鑽屑 排出溝槽2是設置成三條；於該鑽頭3的前端部中，爲各 -8- (5) (5)200306897 條導像部1之前端面的刃腹4，是與所鄰接導像部1的刃 腹4交叉而形成三條橫刃5，該三條橫刃5的交點構成著 前端尖銳部。 又，於申請專利範圍第3項所記載之鑽頭中，鑽屑排 出溝槽2是設置成三條；於該鑽頭3的前端部中’爲各條 導像部1之前端面的刃腹4，是與所鄰接導像部1的刃腹 4交叉而形成三條橫刃5，該三條橫刃5的交點構成著前 端尖銳部。 此外，於申請專利範圍第4項所記載之鑽頭中’鑽屑 排出溝槽2是設置成三條；於該鑽頭3的前端部中’爲各 條導像部1之前端面的刃腹4，是與所鄰接導像部1的刃 腹4交叉而形成三條橫刃5，該三條橫刃5的父點構成者 前端尖銳部。 另外，於申請專利範圍第1項所記載之鑽頭中，鑽屑 排出溝槽2是設置成三條以上；於該鑽頭3的前端部中’ 爲各條導像部1之前端面的刃腹4，是與所鄰接導像部1 的刃腹4交叉而形成三條以上的橫刃5 ’ & 一彳丨木以上的丰頁 刃5的交點構成著前端尖銳部。 此外，於申請專利範圍第2項所記載之鑽頭中’鑽屑 排出溝槽2是設置成三條以上；於該鑽頭3的前端部中’ 爲各條導像部1之前端面的刃腹4，是與所鄰接導像部1 的刃腹4交叉而形成三條以上的橫刃5，該三條以上的橫 刃5的交點構成著前端尖銳部。 又，於申請專利範圍第3項所記載之鑽頭中’鑽屑排 -9- (6) 200306897 出溝槽2是設置成三條以上；於該鑽頭3的 各條導像部1之前端面的刃腹4 ’是與所鄰 刃腹4交叉而形成三條以上的橫刃5 ’該三 5的交點構成著前端尖銳部。 此外，於申請專利範圍第4項所記載之 排出溝槽2是設置成三條以上；於該鑽頭3 爲各條導像部1之前端面的刃腹4，是與所 的刃腹4交叉而形成三條以上的橫刃5，該 刃5的交點構成著前端尖銳部。 另外，於申請專利範圍第1項至第1 2 載之鑽頭中，該鑽頭3爲超硬合金製鑽頭。 又，於申請專利範圍第1項至第1 2項 之鑽頭中，該鑽頭3爲印刷配線基板加工用 此外，於申請專利範圍第1 3項所記載 鑽頭3爲印刷配線基板加工用。 又，鑽頭3是於其外周面設有螺旋狀之 溝槽2，在該鑽屑排出溝槽2彼此之間設有 於前端設有鑽刃8之印刷配線基板加工用的 爲：該鑽頭3爲超硬合金製鑽頭；設有三條 狀的鑽屑排出溝槽2 ;於該鑽頭3的前端部 像部1之前端面的刃腹4，是與所鄰接導像 交叉形成三條橫刃5，該三條橫刃5的交點 銳部；於鑽屑排出溝槽2的底部，以並設狀 鑽屑排出溝槽2的前端往該鑽屑排出溝槽2 前端部中，爲 接導像部1的 條以上的橫刃 鑽頭中，鑽屑 的前端部中， 鄰接導像部1 三條以上的橫 項任一項所記 任一項所記載 鑽頭。 之鑽頭中，該 複數鑽屑排出 導像部1，又 鑽頭，其特徵 各剖視爲同形 中，爲各條導 部1的刃腹4 構成著前端尖 態設置著從該 延伸設置方向 -10- (7) (7)200306897 延伸的二條鑽屑導引凹槽6、7，該二條鑽屑導引凹槽6、 7其中有一條鑽屑導引凹槽的深度及長度是設定成比另一 條鑽屑導引凹槽的深度還淺且長度還短。 另外，鑽頭3是於其外周面設有螺旋狀之複數鑽屑排 出溝槽2，在該鑽屑排出溝槽2彼此之間設有導像部1， 又於前端設有鑽刃8之印刷配線基板加工用的鑽頭，其特 徵爲：該鑽頭3爲超硬合金製鑽頭；設有三條各剖視爲同 形狀的鑽屑排出溝槽2 ;於該鑽頭3的前端部中，爲各條 導像部1之前端面的刃腹4 ’是與所鄰接導像部1的刃腹 4交叉形成三條橫刃5 ’該三條橫刃5的交點構成著前端 尖銳部；於鑽屑排出溝槽2的底部’以並設狀態設置著從 該鑽屑排出溝槽2的前端往該鑽屑排出溝槽2延伸設置方 向延伸的二條鑽屑導引凹槽6、7，該二條鑽屑導引凹槽6 、7其中有一條鑽屑導引凹槽的深度及長度是設定成比另 一條鑽屑導引凹槽的深度還淺且長度還長。 .【實施方式】 〔發明之實施形態〕 第3圖至第5圖爲表示本發明之一實施例’其說明如 下。 本實施例，是於外周面設有螺旋狀之複數鑽屑排出溝 槽2，在該鑽屑排出溝槽2彼此之間設有導像部1 ’又於 前端設有鑽刃8之印刷配線基板加工用的鑽頭3 ’其於鑽 屑排出溝槽2的底部設有* ί主贊《 ^ tB丨冓ί曹2 & ί申設®力 -11 - (8) (8)200306897 向延伸的二條鑽屑導引凹槽6、7之鑽頭。 該鑽頭3爲超硬合金製，例如是採用以平均粒徑爲1 // 1T1以下之碳鶴爲主要成份的超微粒子超硬合金（混合者 鈷、鐽、鉻等）。另，也可採用其他的超硬合金。 設有三條鑽屑排出溝槽2。此外，於鑽屑排出溝槽2 彼此間設有導像部1，並且，採用沒有鏟齒面構成的導像 部。另外，鑽屑排出溝槽2，是採用各條剖視爲同一形狀 的鑽屑排出溝槽。又，該三條鑽屑排出溝槽2，是設置成 等間隔。 另，本實施例之鑽頭3，從該鑽頭3的前端側看是往 左旋轉進行鑽孔加工的鑽頭，三條鑽屑排出溝槽2從該鑽 頭3的前端側看是設置成右螺旋狀。 二條鑽屑導引凹槽6、7是設置成並設狀態。 該鑽屑排出溝槽2和二條鑽屑導引凹槽6、7 (以下 稱第一鑽屑導引凹槽6、第二鑽屑導引凹槽7 )是同時形 成。即藉由磨刀石硏磨先形成第二鑽屑導引凹槽7及導像 部1的一側面，接著，形成第一鑽屑導引凹槽6及所鄰接 之導像部1的一側面以形成鑽屑排出溝槽2和第一鑽屑導 引凹槽6及第二鑽屑導引凹槽7。另外，此時’第一鑽屑 導引凹槽6並不會使在第二鑽屑導引凹槽7所設定的鑽頭 3芯厚減少，並且，是形成爲擴大第二鑽屑導引凹槽7的 寬度（鑽屑排出溝槽2的寬度）。 另，第一鑽屑導引凹槽6及第二鑽屑導引凹槽7，例 如也可以是V字形、U字形、梯形的凹槽等。此外’第一 -12- (9) (9)200306897 鑽屑導引凹槽6及第二鑽屑導引凹槽7也可以是相同或$ 同的形狀。 第一鑽屑導引凹槽6及第二鑽屑導引凹槽7，是從|贊 屑排出溝槽2的前端開始各別延伸設置著。 該第一鑽屑導引凹槽6及第二鑽屑導引凹槽7的深@ ，第一鑽屑導引凹槽6的深度是設定成比第二鑽屑導弓丨凹 槽7的深度還淺。藉此，使鑽頭3的芯厚在重視著該鑽頭 3剛性的狀況下主要是由第二鑽屑導引凹槽7來決定，盡 可能不降低鋼性，並且，是由第一鑽屑導引凹槽6確保著 鑽屑排出性影響大之鑽屑排出溝槽2的深度和寬度，使該 鑽屑排出性得以良好地發揮。 此外，第一鑽屑導引凹槽6是比第二鑽屑導引凹槽7 還短，形成爲在前往鑽頭3之底端側的途中就消失。因此 ，對鑽屑排出溝槽2來講第鑽屑導引凹槽6不存在的部份 。是僅由第二鑽屑導引凹槽7來形成鑽屑排出溝槽2。 被引導至鑽屑排出溝槽2內的鑽屑，是藉由第一鑽屑 導引凹槽6及第二鑽屑導引凹槽7的引導作用在鑽屑排出 溝槽2內良好地通過後，於上述第一鑽屑導引凹槽6消失 部位因上述引導作用減弱而往鑽頭3外方移動，逐漸離開 該鑽頭3。 導像部1的前端面是設定成被稱爲是刃腹4的傾斜面 。此外，導像部1的刃腹4，是從鑽頭3的中心軸朝鑽頭 3的外周邊緣傾斜的面。 位於所鄰接之導像部1前端的刃腹4交叉邊，是設定 -13- (10) 200306897 成直線邊。由於設有三片鑽刃8，所以刃腹4是與其 接於左右的二條導像部1的刃腹4各別中介著直線邊 交叉。該三條直線邊的交點是與鑽頭3的中心軸爲一 位置。 藉由該鄰接之刃腹4彼此的交叉，使鑽頭3的前 形成著合計爲三條的直線形橫刃5。此外，由於刃腹 傾斜，及，三條的直線形橫刃5爲交叉，使鑽頭3的 前端部形成尖銳。 然而，這對上述習知例來講有下述之問題點。 習知例，是設有導像部3 1及鑽刃4 1合計爲二條 謂的二片刃鑽頭。但是，就二片刃鑽頭而言，是難以 鑽頭3 3的中心前端部硏磨成尖銳。其原因在於二片 頭只有二條導像部3 1，而由導像部3 1的刃腹3 9 (設 像部3 1前端的傾斜面）彼此交叉所形成的橫刃40只 條。因此，於習知例中，就施有要使橫刃40中央部 尖銳的辦法（例如：於導像部的前端形成不同角度的 刃腹使橫刃的中央部形成尖銳）。 鑽頭3 3的中心前端部若不尖銳，在鑽孔開始時 頭3 3的中心位置就容易偏掉，相對地當然會降低貫 的精度。 但是，本實施例，如上述般由於刃腹4爲傾斜且 橫刃5爲交叉著，所以鑽頭3的前端部就形成尖銳， 不需要如習知例般的加工，就可構成鑽孔位置不會偏 鑽頭。 所鄰 進行 致的 端部 4爲 中心 之所 將其 刃鑽 在導 有一 形成 二個 的鑽 穿孔 三條 因此 掉的 -14- (11) (11)200306897 圖中，圖號π，是爲要盡可能降低和導像部1的外 面及由鑽頭3所形成之加工孔內面的抵接面積之段部。本 實施例的構成，可採用被稱爲具有該段部Π之所謂的讓 切式（Undercut Type)構成，也可採用不具有段部之所謂的 直切式（Straight Type)構成。 本實施例，爲要在疊層爲多層的印刷配線基板上鑽鑿 貫穿孔，而構成爲鑽徑小且長度長。此外，鑽頭3的芯厚 (鑽頭3最細部份的直徑），是設定成鑽屑排出溝槽2可 良好地排出鑽屑，並且，是設定成該鑽頭3的強度得以維 持成可良好地發揮筆直前進性的程度。 即使鑽頭3的鑽徑小，但因爲設置在鑽屑排出溝槽2 底部的上述二條鑽屑導入凹槽6、7及形成在該條鑽屑導 入凹槽6、7間的凸條部份可發揮做爲加強肋條的作用， 使鑽頭3變成高強度，並且，可發揮高筆直前進性。 此外，由於設置在鑽屑排出溝槽2底部的上述二條鑽 屑導入凹槽6、7使鑽屑的移動被引導，所以可良好地執 行該鑽屑的排出，防止鑽屑滯留在該鑽屑排出溝槽2內。 另外，因二條鑽屑導入凹槽6、7之中的第一鑽屑導 入凹槽6的長度是比第二鑽屑導入凹槽7的長度還短，所 以鑽屑不會一直都滯留在鑽屑排出溝槽2內，而會從該鑽 屑排出溝槽2排出至鑽頭3的外方，因此就這點而言也可 良好地執行鑽屑的排出。 此外，因鑽頭3前端側的鑽屑排出性能高，所以儘是 如此就可良好地執行鑽屑的排出。 -15- (12) (12)200306897 因此’鑽頭3就難彎折，即使鑽徑小且長度長，也能 具高強度並且發揮高筆直前進性，再者，又可防止因鑽屑 滯留在鑽屑排出溝槽2內而造成的工作瑕疵，鑽鑿出內壁 粗糙度爲良好的孔（精度良好的孔）。 另外’因鑽頭3爲超硬合金製，所以其強度當然高， 就這點而言也可發揮高筆直前進性。 又，於習知例中，因有後跟3 5，從該後跟3 5跨越橫 刃斜角3 6的面（後跟面3 8 )的剖視爲凹彎曲形狀，所以 使該凹彎曲形狀部份抱住鑽屑，但因本實施例是採用沒有 後跟的構成，所以不會有抱住鑽屑的現象發生，因此，就 這點而言也可良好地發揮鑽屑排出溝槽2的鑽屑排出作用 〇 如此，根據本實施例時，因可極良好地發揮鑽屑排出 溝槽2的鑽屑排出作用，所以能夠防止由鑽頭3所鑽鑿的 孔內壁面會因鑽屑而造成粗糙不整，因此，可鑽鑿出精度 良好的孔。 此外，因導像部1是爲三條設置形成的構成，所以由 鑽頭3所鑽鑿的孔與該鑽頭3是在三條導像部1的外周面 進行抵接，因此，藉由三點支撐使該鑽頭3在孔中呈穩定 狀態，如此一來也可發揮高筆直前進性。 另外，鑽刃8的數量也比習知例還多’以相同條件下 進行鑽孔加工時，作用在鑽刃8上的加工負載會減輕’並 且，作用在一條鑽屑排出溝槽2的鑽屑排出負載也會減輕 ，僅是如此就可使鑽孔加工穩定進行’藉此也可發揮高筆 -16- (13) (13)200306897 直前進性，並且，可鑽鑿出精度良好的孔。 又，鑽刃8爲三片，合計有三條由鄰接的刃腹4交叉 形成的橫刃5，因該三條橫刃5的交點是形成尖銳，所以 在鑽孔時要決定中心位置的尖銳可簡單地形成在鑽頭3的 中心軸。 以上本實施例因是爲上述般的構成，所以即使鑽徑小 且長度長，也可成爲具高強度並且發揮高筆直前進性的鑽 頭，再者，又可做爲鑽鑿出的孔內壁粗糙度爲良好之實用 性極佳的印刷配線基板加工用鑽頭。 第6圖、第7圖爲已確認本實施例之效果的實驗結果 。另，第6圖爲表示本實施例之孔位置精度的實驗結果， 第7圖爲表示習之例之孔位置精度的實驗結果。 鑽頭，是使用直徑爲0.3 5 m m的小鑽徑型鑽頭。此 外，芯厚爲相同尺寸（規格是重視著良好之內壁粗糙度的 實現而定）。又，要鑽孔的印刷配線基板，是使用總厚度 爲 5 m m之重疊複數片相當於美國電力工業規格（ National Electrical Manufacturers Association)之 F R — 4規格的印刷配線基板。鑽頭的旋轉速度等之加工條件爲 相同。 孔位置，是以重心法求出。 在評估實際所鑽鑿出的孔的分佈是偏離設計上的孔中 心爲何種程度時，於一般上是以設計上的孔中心至實際所 鑽鑿出的孔的中心位置爲止的距離平均，及其與標準偏差 的三倍之和來進行評估，根據該評估，本實施例和習知例 -17- (14) (14)200306897 相比約只有60 %之實際所鑽鑿出的孔的中心是沒有偏差 ，由此可確認出是可鑽鑿出非常高精度的孔。 此外，對鑽孔後的印刷配線基板進行電鍍處理在孔中 設有銅電鍍層，然後裁切印刷配線基板，對上述孔的縱剖 面進行放大觀察結果，本實施例，與習知例同爲孔內壁粗 糙度良好。 即，本實施例之鑽頭3，在被確認是可鑽鑿直徑爲 0 · 3 5 m m程度，並且，深度爲5 m m以上之孔的鑽頭的同 時，被應確認其是具高筆直前進性，及所鑽鑿出的孔內壁 粗糙度爲良好的雙好鑽頭3。 另外，以目視就可觀察出本實施例在鑽屑排出方面是 比較良好。 另，因鑽頭3的剛性高，所以也可採用朝鑽頭3的底 端側其芯厚會逐漸便大的構成。 又，鑽屑排出溝槽2也可設置成從鑽頭3的前端側看 是爲左螺旋狀。 另，鑽屑排出溝槽2雖然也可爲設置成四條以上的構 成（橫刃5變成四條以上），但從三條導像部1所形成的 三點支撐效果來考量時，或從三條橫刃5的交點必然成一 點的事實來考量時，鑽屑排出溝槽2還是以三條的構成爲 最佳。 又，第一鑽屑導引凹槽6也可構成爲比第二鑽屑導引 凹槽7還長。 (15) (15)200306897 〔發明作用及效果〕 由於本發明是在鑽屑排出溝槽2的底部設有往該鑽屑 排出溝槽2延伸設置方向延伸的複數鑽屑導引凹槽6、7 ，因此該複數鑽屑導引凹槽6、7間發揮著做爲加強肋條 的作用，就該點而言可使鑽頭3的強度變高。 因此’鑽頭3就難彎折，即使鑽徑小且長度長，也能 具局強度並且發揮高筆直前進性。 此外’由於鑽頭3的強度高，所以能夠使其芯厚爲小 以充分確保鑽屑排出溝槽2的深度來進行良好之鑽屑排出 ，防止鑽屑滯留在鑽屑排出溝槽2內造成工作瑕疵。 因此，使用該鑽頭3時，就可鑽鑿出內壁粗糙度爲良 好的孔（精度良好的孔）。 再者’鑽屑的排出是由設置在鑽屑排出溝槽2的底部 的複數鑽屑導引凹槽6、7來引導，因此鑽屑的排出得以 良好進行。 又’根據本發明之申§靑專利軔圍第2項的發明時，由 於複數鑽屑導引凹槽6、7的深度不同，所以較淺的鑽屑 導引凹槽可發揮鑽頭3強度的維持作用，較深的鑽屑導引 凹槽能以高水準發揮鑽屑的排出作用，藉此可達到良好的 鑽屑排出性及由鑽頭高剛性產生的高筆直前進性，即可達 到孔位置精度的提昇。 再者，根據本發明之申請專利範圍第3、4項的發明 時，由於複數鑽屑導引凹槽6、7的長度不同，所以在鑽 頭3的則端側是因該複數鑽屑導引凹槽6、7而彳辱以發揮 -19- (16) (16)200306897 高的鑽屑排出性，在鑽頭3的底端側是因長度較短的鑽屑 導引凹槽消失而提高了鑽頭3的強度，因此’可達到良好 的鑽屑排出性及由鑽頭高剛性產生的高筆直前進性，即可 達到孔位置精度的提昇。 本發明由於是構成爲上述般的構成，所以即使是鑽徑 小且長度長，也可成爲高強度，可發揮高筆直前進性的鑽 頭，又可做爲鑽鑿出的孔內壁粗糙度爲良好之實用性極佳 的印刷配線基板加工用鑽頭。 【圖式簡單說明】 第1圖爲習知例之說明用正面圖。 第2圖爲習知例之說明用側面圖。 第3圖爲本實施例之說明用透視圖。 第4圖爲本實施例之說明用正面圖。 第5圖爲本實施例之說明用側面圖。 第6圖爲表示本實施例之位置精度實驗結果。 第7圖爲表示習知例之位置精度實驗結果。 〔圖號說明〕 1 :導像部 2 :鑽屑排出溝槽 3 :鑽頭 4 :刃腹 5 :橫刃 -20- (17)200306897 6、7 :鑽屑導引凹槽 8 :鑽刃200306897 Π) 发明. Description of the invention [Technical field to which the invention belongs] The present invention relates to a drill for drilling precision holes in a work piece. [Prior art] A printed wiring board (hereinafter referred to as a printed circuit board) for assembling electronic components is formed by laminating a copper foil on a reinforced fiber resin, and drilling a large number of through-holes on the printed circuit board, and then passing through a plating process. A metal plating layer is formed on the inner wall of the through hole, and then the copper foil on the surface of the printed substrate is etched to form a printed circuit. The printed circuit and the underlying copper foil are turned on through the metal plating layer to power on, and then An electronic component such as an LSI is soldered to the above-mentioned through hole to form a printed circuit board. However, in recent years, with the high-performance and miniaturization of electronic equipment, the demand for high-density assembly of printed circuit boards has become increasingly high. According to this demand, while the thinning, high-layering, and high-density wiring of printed circuit boards are progressing, the pace of reducing the diameter of the through holes to be drilled in the printed substrates is accelerated. Therefore, the drills used are bound to be used. In addition, in order to improve work efficiency and reduce manufacturing costs, for the through-hole drilling processing on a printed substrate, a plurality of overlapping printed circuit boards are used for through-hole drilling processing. Therefore, the aspect ratio of the through-hole (the ratio of the plate thickness to the hole diameter) becomes larger, so a longer drill bit is required. In addition, if the drill bit is longer, the strength required by the drill bit is relatively increased. Therefore, the drill needs to have high strength. -5- (2) (2) 200306897 In addition, the deeper the through hole, the easier it is for the hole to bend. Therefore, the drill needs to have a high straightness. In addition, from an electrical point of view, the drill bit must be able to drill a good roughness of the inner wall of the through hole on the spot, that is, the drill bit must be able to drill a hole with a smooth inner wall thickness as much as possible. Sorting out the above, it can be seen that the requirements for recent drills for printed circuit board processing are that they must have a small drill diameter, a long length, high strength, excellent straight forwardness, and rough holes. The degree is good. On the other hand, Figs. 1 and 2 show drill bits 3 3 (hereinafter referred to as conventional examples) for drilling through holes of a conventional printed circuit board. In this conventional example, a cutting edge 41 is provided at the front end, two spiral drill cuttings discharge grooves 3 2 are provided on the outer peripheral surface, and a guide portion 3 1 is provided between the drill cuttings discharge grooves 3 2. Then, a shovel tooth surface 34 having a diameter slightly smaller than the diameter of the drill 33 is provided at a position adjacent to the image guide 31, and a heel 3 5 is formed on the opposite side of the image guide 31 of the shovel tooth surface 34. . Here, the drill cuttings discharge groove 3 2 is formed in a straight straight line from the end edge (outer peripheral corner) of the image guide 31 to the lateral edge oblique angle 3 6, and from the lateral edge oblique angle 3 6 to the heel 3 5. (Heel surface 3 8) The concave-curved shape is configured in cross-section in consideration of the discharge performance of the cuttings. [Summary of the Invention] [Problems to be Solved by the Invention] With the structure of the conventional example, the drill diameter as described above is small, and the length is -6-(3) (3) 200306897 long, with high strength and excellent strength. The following contradiction occurs when the drill is straight and the inner wall roughness of the hole being drilled is good. First, when the drill diameter of the drill bit 3 is a small diameter, the strength of course decreases. In addition, as the length of the drill 3 3 becomes longer, it becomes easier to bend, so that its straight forwardability decreases. Therefore, it is considered to increase the core thickness (the diameter of the thinnest part) of the drill bit 3 3 to increase the strength, but in this situation, the depth of the drill cutting groove 3 2 will be shallower, which will reduce the drilling depth. Chip discharge performance. When the discharge performance of drill cuttings is reduced, the drill bit 3 3 will drill in a state where the cuttings are held in the drill cuttings discharge groove 3 2, and the part of the cuttings will cause the inner wall surface of the through hole to become The rough uneven surface, in addition, the load acting on the drill 3 3 will increase the damage to the drill 33. Therefore, as far as the conventional example is concerned, it is difficult to increase the core thickness of the drill 33, so it is difficult to satisfy the above conditions (small drill diameter, long length, high strength, excellent straightness, and The roughness of the inner wall of the hole being drilled is a good bit), especially the straight forwardness and the roughness of the inner wall of the hole being drilled cannot be achieved at the same time. The present invention '7H was completed in view of the above-mentioned problems, and its object is to provide a high-strength and straight-forward performance that can be achieved even with a small drill diameter and a long length', and can also make the inside of a drilled hole Wall roughness is a drill with good practicality. [Means for Solving the Problems] The gist of the present invention will be described with reference to the drawings. -7-(4) (4) 200306897 The drill bit 3 is provided with a plurality of spiral cuttings discharge grooves 2 on the outer peripheral surface of the drill cutting grooves 2 'There are guide images η21' between the cuttings discharge grooves 2 and each other A drill bit with a drill edge 8 at its end is characterized in that a plurality of drill chip guide grooves 6 and 7 are provided at the bottom of the drill chip discharge groove 2 and extend in a direction in which the drill chip discharge groove 2 extends. In addition, in the drill bits described in the first patent application scope, the 'plurality of cuttings guide grooves 6, 7 are set in parallel, and the depth of at least one of the cuttings guide grooves is set to be more than the other The depth of the drill chip guide groove is shallow. Moreover, in the drill bit described in item 1 of the scope of the patent application, the plurality of cuttings guide grooves 6, 7 are extended from the front end of the cuttings discharge groove 2, and at least one of the cuttings guide grooves is provided. The length is set to be shorter than the length of other cuttings guide grooves. In addition, in the drill bit described in item 2 of the scope of the patent application, the plurality of cuttings guide grooves 6, 7 are extended from the front end of the cuttings discharge groove 2, and at least one of the cuttings guide grooves is provided. The length is set to be shorter than the length of other cuttings guide grooves. In addition, in the drill bit described in Item 1 of the scope of the patent application, the drill cuttings discharge grooves 2 are provided in three pieces; in the front end portion of the drill bit 3, the cutting edge 4 of the front end face of each guide portion 1 is Three cutting edges 5 are formed by crossing the flank 4 of the adjoining guide portion 1, and the intersection of the three cutting edges 5 constitutes a sharpened tip. In addition, in the drill bit described in item 2 of the scope of the patent application, the drill cuttings discharge grooves 2 are provided in three pieces; in the front end portion of the drill bit 3, there are -8- (5) (5) 200306897 guides The burrs 4 on the front end face of the section 1 intersect with the burrs 4 of the adjoining image guide section 1 to form three lateral blades 5, and the intersection of the three lateral blades 5 constitutes a sharpened tip. Further, in the drill bit described in item 3 of the scope of the patent application, the drill cuttings discharge grooves 2 are provided in three pieces; in the front end portion of the drill bit 3, is the cutting edge 4 of the front end face of each of the image guide portions 1, is Three cutting edges 5 are formed by crossing the flank 4 of the adjoining guide portion 1, and the intersection of the three cutting edges 5 constitutes a sharpened tip. In addition, in the drill bit described in item 4 of the scope of the patent application, 'drill cuttings discharge grooves 2 are provided in three pieces; in the front end portion of the drill bit 3' are the cutting edges 4 of the front end face of each guide portion 1, It intersects with the flank 4 of the adjoining guide part 1 to form three transverse blades 5, and the parent points of the three transverse blades 5 constitute a sharpened front end. In addition, in the drill bit described in Item 1 of the scope of the patent application, the drill cuttings discharge grooves 2 are provided in three or more; in the front end portion of the drill bit 3 is the cutting edge 4 of the front end face of each of the image guides 1, It intersects with the flank 4 of the adjoining guide part 1 to form three or more horizontal blades 5 ′. The intersection point of the leaf blade 5 with a height of more than one wood constitutes the front sharp portion. In addition, in the drill bit described in item 2 of the patent application scope, "drill cuttings discharge grooves 2 are provided in three or more; in the front end portion of the drill bit 3" is the cutting edge 4 of the front end face of each of the image guides 1, It intersects with the flank 4 of the adjacent image guide 1 to form three or more horizontal edges 5, and the intersection of the three or more horizontal edges 5 constitutes a sharpened tip. In the drill bit described in the scope of patent application No. 3, “Drill Chip Row-9- (6) 200306897, the grooves 2 are provided in three or more; the cutting edges on the front end face of each guide portion 1 of the drill 3 The abdomen 4 ′ intersects the adjacent flank abdomen 4 to form three or more horizontal blades 5 ′. The intersection of the three 5 constitutes a sharp point at the front end. In addition, three or more discharge grooves 2 described in item 4 of the scope of patent application are provided; the drill bit 3 is the cutting edge 4 of the front end surface of each image guide 1 and is formed by crossing the cutting edge 4 Three or more horizontal edges 5, and the intersections of the edges 5 constitute a sharpened tip. In addition, among the drill bits contained in items 1 to 12 of the patent application scope, the drill bit 3 is a cemented carbide drill bit. Further, among the drill bits in the scope of claims 1 to 12 of the patent application, the drill 3 is used for processing printed wiring boards. In addition, the drill 3 described in the scope of claims 13 in the patent application is used for processing printed wiring boards. The drill 3 is provided with a spiral groove 2 on its outer peripheral surface, and the drill chip discharge groove 2 is provided with a drill edge 8 at the front end for processing printed wiring boards. The drill 3 It is a cemented carbide drill bit; it is provided with three stripe-shaped cuttings discharge grooves 2; the cutting edge 4 at the front end face of the image portion 1 of the front end of the drill bit 3 forms three transverse edges 5 that intersect with the adjacent guide image. The sharp part of the intersection of the three transverse blades 5; at the bottom of the cuttings discharge groove 2 at the bottom of the cuttings discharge groove 2 in a juxtaposed manner toward the front end of the cuttings discharge groove 2 is for the image guide 1 Among the horizontal-edge drills having more than three strips, the drill bit described in any one of the three or more horizontal items adjoining the image guide 1 in the tip portion of the cuttings. In the drill bit, the plurality of drill cuttings are ejected from the guide portion 1, and the drill bit is characterized by being cut in the same shape, and the leading edge 4 of each guide portion 1 is formed in a tip state, and the extension direction is set to -10. -(7) (7) 200306897 Two extended cuttings guide grooves 6, 7 are extended. One of the two guided cuttings grooves 6 and 7 is set to a depth and length that are longer than the other. A cuttings guide groove is shallow and short. In addition, the drill 3 is provided with a spiral-shaped plurality of drill cuttings discharge grooves 2 on its outer peripheral surface, and a guide portion 1 is provided between the drill cuttings discharge grooves 2 and a cutting edge 8 is provided at the front end. The drill bit for wiring board processing is characterized in that the drill bit 3 is a cemented carbide drill bit; it is provided with three drill cuttings discharge grooves 2 each cut into the same shape; the front end of the drill bit 3 is each The cutting edge 4 ′ of the front end surface of the guide portion 1 intersects with the cutting edge 4 of the adjacent guide portion 1 to form three transverse edges 5 ′. The intersection of the three transverse edges 5 constitutes a sharp point at the front end; At the bottom of the two cutting edge guide grooves 6 and 7 are provided in a juxtaposed state extending from the front end of the cutting edge discharge groove 2 toward the direction in which the cutting edge discharge groove 2 extends. The two cutting edge guide recesses The depth and length of one of the cuttings guide grooves in the grooves 6 and 7 are set to be shallower and longer than the depth of the other cuttings guide groove. [Embodiment] [Embodiments of the invention] Figs. 3 to 5 show an embodiment of the present invention 'and its explanation is as follows. In this embodiment, a plurality of spiral-shaped drill cuttings discharge grooves 2 are provided on the outer peripheral surface, and the drill cuttings discharge grooves 2 are provided with a guide portion 1 ′ and a printed wiring with a drill edge 8 at the front end. The drill bit 3 for substrate processing is provided at the bottom of the drill chip discharge groove 2 * ί 主 赞 《^ tB 丨 冓 ίCao 2 & ί Shenshe® Li-11-(8) (8) 200306897 extended Two drill cuttings guide grooves 6, 7 of the drill. The drill 3 is made of cemented carbide, for example, a superfine cemented carbide (mixed with cobalt, samarium, chromium, etc.) using a carbon crane whose main particle size is 1 // 1T1 or less as a main component. In addition, other cemented carbides can also be used. There are three drill cuttings discharge grooves 2. In addition, an image guide 1 is provided between the drill chip discharge grooves 2 and an image guide having no shovel surface is used. In addition, the cuttings discharge groove 2 is a cuttings discharge groove in which each section is cut into the same shape. The three drill cuttings discharge grooves 2 are arranged at regular intervals. In addition, the drill 3 of this embodiment is a drill that rotates to the left when viewed from the front end side of the drill 3, and the three drill chip discharge grooves 2 are provided in a right spiral shape when viewed from the front end of the drill 3. The two drill cutting guide grooves 6, 7 are arranged in a juxtaposed state. The cuttings discharge groove 2 and the two cuttings guide grooves 6, 7 (hereinafter referred to as the first cuttings guide groove 6, and the second cuttings guide groove 7) are simultaneously formed. That is, a second drill cutting guide groove 7 and one side of the image guide 1 are formed first by a honing stone, and then a first drill guide groove 6 and one of the adjacent guides 1 are formed. The side faces are formed with drill cuttings discharge grooves 2 and a first drill cuttings guide groove 6 and a second drill cuttings guide groove 7. In addition, at this time, the 'first drill cutting guide groove 6 does not reduce the core thickness of the drill 3 set in the second drill cutting guide groove 7, and is formed to enlarge the second drill cutting guide groove. The width of the groove 7 (the width of the drill cuttings discharge groove 2). The first cuttings guide groove 6 and the second cuttings guide groove 7 may be V-shaped, U-shaped, trapezoidal grooves, for example. In addition, the first drill cutting guide groove 6 and the second drill cutting guide groove 7 of the first -12- (9) (9) 200306897 may also have the same or the same shape. The first drill cuttings guide groove 6 and the second drill cuttings guide groove 7 are respectively extended from the front end of the | Zan chip discharge groove 2. The depth of the first cuttings guide groove 6 and the second cuttings guide groove 7 is. The depth of the first cuttings guide groove 6 is set to be greater than that of the second cuttings guide bow 丨 groove 7. The depth is still shallow. With this, the core thickness of the drill bit 3 is mainly determined by the second drill chip guide groove 7 under the condition that the rigidity of the drill bit 3 is valued, and the rigidity is not reduced as much as possible, and the first drill chip guide The guide groove 6 ensures the depth and width of the cuttings discharge groove 2 having a large influence on the cuttings discharge performance, so that the cuttings discharge performance can be exerted well. The first cuttings guide groove 6 is shorter than the second cuttings guide groove 7 and is formed so as to disappear on the way to the bottom end side of the drill 3. Therefore, for the cuttings discharge groove 2, the portion where the cuttings guide groove 6 does not exist. The cuttings discharge groove 2 is formed only by the second cuttings guide groove 7. The cuttings guided into the cuttings discharge groove 2 pass through the cuttings discharge groove 2 well by the guiding action of the first cuttings guide groove 6 and the second cuttings guide groove 7. Then, at the disappearing part of the first drill cuttings guide groove 6, the guide effect is weakened, and the drill bit 3 is moved outside, and gradually leaves the drill bit 3. The front end surface of the image guide portion 1 is an inclined surface set to be referred to as a cutting edge 4. The blade web 4 of the image guide 1 is a surface inclined from the central axis of the drill 3 toward the outer peripheral edge of the drill 3. The flank 4 at the leading edge of the adjoining guide section 1 is set to -13- (10) 200306897 in a straight line. Since three drill edges 8 are provided, the cutting edge 4 intersects with the cutting edge 4 of the two image guides 1 connected to the left and right sides with straight edges interposed therebetween. The intersection of the three straight sides is a position with the center axis of the drill 3. When the adjacent cutting edges 4 intersect with each other, the front side of the drill 3 is formed with three straight linear cutting edges 5 in total. In addition, the tip of the drill 3 is sharpened by the inclination of the cutting edge and the intersection of the three linear cutting edges 5 with each other. However, this has the following problems for the above-mentioned conventional examples. A conventional example is a two-piece drill with a guide section 31 and a drill edge 41 in total. However, in the case of a two-edged drill, it is difficult to sharpen the center tip of the drill 33. The reason for this is that the two-piece head has only two image guide portions 31, and 40 blades formed by the flank 39 of the image guide portion 31 (the inclined surface at the front end of the image portion 31) intersect each other. Therefore, in the conventional example, a method of sharpening the central portion of the horizontal blade 40 is applied (for example, a blade with a different angle is formed at the front end of the image guide portion to sharpen the central portion of the horizontal blade). If the center front end of the drill 3 3 is not sharp, the center position of the drill 3 3 will be easily off at the beginning of drilling, and the accuracy of course will be relatively reduced. However, in this embodiment, since the cutting edge 4 is inclined and the cutting edge 5 is intersecting as described above, the tip of the drill 3 is sharpened, and the drilling position can be formed without the need for processing as in the conventional example. Will be biased. The adjoining end 4 is centered, so its blade is drilled in a drill hole with two drill holes and three drill holes are formed. Therefore, in the figure, the number π is for the purpose of exhaustion. It is possible to reduce the area of the contact area between the outer surface of the image guide 1 and the inner surface of the processing hole formed by the drill 3. The structure of this embodiment may be a so-called undercut type structure having a segment portion Π, or a so-called straight type structure without a segment portion. In this embodiment, a through-hole is to be drilled in a printed wiring board laminated in a plurality of layers, and the drill diameter is small and the length is long. In addition, the core thickness of the drill 3 (the diameter of the thinnest part of the drill 3) is set so that the drill cuttings discharge groove 2 can well discharge the cuttings, and the strength of the drill 3 is maintained so that it can be maintained well. Extent of straight forwardness. Even if the drill diameter of the drill bit 3 is small, it is possible because of the two drill cuttings introduction grooves 6 and 7 provided at the bottom of the drill cuttings discharge groove 2 and the convex portion formed between the drill cuttings introduction grooves 6 and 7. It functions as a reinforcing rib to make the drill bit 3 high-strength, and it can exhibit high straight forwardness. In addition, since the two cuttings introduction grooves 6 and 7 provided at the bottom of the cuttings discharge groove 2 guide the movement of the cuttings, the discharge of the cuttings can be performed well and the cuttings can be prevented from staying in the cuttings It is discharged into the groove 2. In addition, since the length of the first cuttings introduction groove 6 among the two cuttings introduction grooves 6 and 7 is shorter than the length of the second cuttings introduction groove 7, the cuttings will not stay in the drill all the time. The chip discharge groove 2 is discharged from the drill chip discharge groove 2 to the outside of the drill 3, and therefore, the discharge of the drill chips can be performed well in this regard. In addition, since the cutting chip discharge performance is high at the front end side of the drill 3, it is possible to perform the discharge of the cutting chips satisfactorily. -15- (12) (12) 200306897 Therefore, it is difficult for the drill bit 3 to bend, even if the drill diameter is small and the length is long, it can have high strength and high straight forward performance. Furthermore, it can prevent the drilling debris from remaining in the Working defects caused by the cuttings being discharged out of the groove 2 can be used to drill holes with good inner wall roughness (holes with good accuracy). In addition, since the drill 3 is made of cemented carbide, its strength is naturally high, and high straight forwardness can be exhibited in this regard. Moreover, in the conventional example, since the cross section of the face (heel surface 3 8) that crosses the bevel angle 3 6 from the heel 3 5 is a concave curved shape, the concave curve is formed. The shape part holds the cuttings, but since this embodiment adopts a structure without a heel, there is no phenomenon of holding the cuttings. Therefore, the cuttings can be well discharged from this point. 2 The cuttings discharge function of the second embodiment. Thus, according to this embodiment, since the cuttings discharge function of the cuttings discharge groove 2 can be exerted very well, the inner wall surface of the hole drilled by the drill 3 can be prevented from being affected by the cuttings. As a result, the surface is rough and uneven, and therefore, a precise hole can be drilled. In addition, since the image guides 1 are formed in three rows, the holes drilled by the drill 3 and the drill 3 are in contact with the outer peripheral surfaces of the three image guides 1. Therefore, the three-point support is used. The drill bit 3 is in a stable state in the hole, so that high straight forwardness can also be exhibited. In addition, there are more drill edges 8 than in the conventional example. “When drilling is performed under the same conditions, the machining load acting on the drill edge 8 will be reduced. The chip discharge load will also be reduced, so that the drilling process can be performed in a stable manner. This also enables high pen -16- (13) (13) 200306897 straight-forward performance, and can drill holes with good accuracy . In addition, the drill edge 8 is three pieces, and a total of three cutting edges 5 formed by the intersection of adjacent cutting edges 4 are formed. Since the intersection of the three cutting edges 5 is sharp, it is easy to determine the sharpness of the center position when drilling. Ground is formed on the central axis of the drill 3. The above-mentioned embodiment has the structure as described above, so even if the drill diameter is small and the length is long, it can be a drill with high strength and high straight forward performance. Furthermore, it can be used as the inner wall of a hole to be drilled. A drill for processing printed wiring boards with excellent roughness and excellent practicality. Fig. 6 and Fig. 7 are experimental results in which the effect of this embodiment has been confirmed. FIG. 6 is an experimental result showing the hole position accuracy of this embodiment, and FIG. 7 is an experimental result showing the hole position accuracy of the example. The drill is a small-diameter drill with a diameter of 0.3 5 m. In addition, the core thickness is the same size (the specifications are based on the realization of good inner wall roughness). In addition, the printed wiring board to be drilled is a printed wiring board with a total thickness of 5 mm, which is equivalent to the F R-4 specification of the National Electrical Manufacturers Association. The processing conditions such as the rotation speed of the drill are the same. The position of the hole was determined by the method of gravity. When assessing how far the distribution of the actually drilled holes deviates from the center of the designed hole, the average is generally the distance from the center of the designed hole to the center of the hole actually drilled, and It is evaluated by the sum of three times the standard deviation. According to this evaluation, the center of the actual drilled hole is only about 60% in this example and the conventional example -17- (14) (14) 200306897. There is no deviation, so it can be confirmed that very high-precision holes can be drilled. In addition, the printed wiring substrate after drilling is plated with a copper plating layer provided in the hole, and then the printed wiring substrate is cut, and the longitudinal section of the hole is enlarged and observed. This embodiment is the same as the conventional example. The inner wall roughness of the hole is good. That is, the drill bit 3 of this embodiment is confirmed to be a drill bit capable of drilling a hole having a diameter of about 0.35 mm and a depth of 5 mm or more. And the double-good drill 3 with a good inner wall roughness of the hole being drilled. In addition, it can be visually observed that this embodiment is relatively good in terms of cuttings discharge. In addition, since the drill 3 has high rigidity, a configuration in which the core thickness gradually becomes larger toward the bottom end side of the drill 3 may be adopted. Further, the drill cuttings discharge groove 2 may be provided in a left spiral shape as viewed from the front end side of the drill 3. In addition, although the drill cuttings discharge groove 2 may be provided in a configuration of four or more (the horizontal blade 5 becomes four or more), when considering the three-point support effect formed by the three image guides 1, or three horizontal blades Considering the fact that the intersection point of 5 must be a little, when considering the drill cuttings discharge groove 2, the three-piece structure is the best. The first cuttings guide groove 6 may be longer than the second cuttings guide groove 7. (15) (15) 200306897 [Inventive effect and effect] Since the present invention is provided with a plurality of drill chip guide grooves 6 at the bottom of the drill chip discharge groove 2 extending in the direction in which the drill chip discharge groove 2 extends, Therefore, the plurality of drill cutting guide grooves 6 and 7 play a role of reinforcing ribs, and in this regard, the strength of the drill 3 can be increased. Therefore, the 'drill 3 is difficult to bend, and even if the drill diameter is small and the length is long, it can have local strength and exhibit high straight forwardness. In addition, 'due to the high strength of the drill 3, the core thickness can be made small to sufficiently ensure the depth of the cuttings discharge groove 2 for good cuttings discharge, preventing the cuttings from staying in the cuttings discharge groove 2 and causing work. defect. Therefore, when this drill bit 3 is used, it is possible to drill a hole having a good inner wall roughness (a hole with a high accuracy). Furthermore, the discharge of the cuttings is guided by the plurality of cuttings guide grooves 6, 7 provided at the bottom of the cuttings discharge groove 2, so that the cuttings can be discharged well. According to the application of the present invention, the invention encompasses the second invention. Since the depth of the plurality of cuttings guide grooves 6 and 7 is different, the shallower cuttings guide groove can exert the strength of the drill 3 Maintaining effect, the deeper cuttings guide groove can play the cuttings discharge function at a high level, thereby achieving good cuttings discharge and high straight forwardness caused by the high rigidity of the drill bit, which can reach the hole position Improved accuracy. Furthermore, according to the invention of claims 3 and 4 of the scope of patent application of the present invention, since the length of the plurality of cuttings guide grooves 6 and 7 is different, the end of the drill 3 is guided by the plurality of cuttings The grooves 6 and 7 are insulted to make use of -19- (16) (16) 200306897. The high cuttings discharge performance is improved at the bottom end of the drill 3 due to the disappearance of the shorter cuttings guide groove. The strength of the drill bit 3, therefore, can achieve good drill chip discharge and high straight forwardness caused by the high rigidity of the drill bit, and can improve the accuracy of the hole position. Since the present invention is structured as described above, even if the drill diameter is small and the length is long, it can be a high-strength drill that can exhibit high straightness, and it can also be used as the inner wall roughness of a drilled hole Good drillability for printed wiring board processing. [Brief description of the drawings] Fig. 1 is a front view for explaining a conventional example. Fig. 2 is a side view for explaining a conventional example. Fig. 3 is a perspective view for explaining the embodiment. Fig. 4 is a front view for explaining the embodiment. Fig. 5 is a side view for explaining the embodiment. Fig. 6 shows the results of the position accuracy experiment of this embodiment. Fig. 7 shows the results of the position accuracy experiment of the conventional example. [Illustration of figure number] 1: Guide part 2: Drill chip discharge groove 3: Drill bit 4: Cutting edge 5: Cross edge -20- (17) 200306897 6, 7: Drill chip guide groove 8: Drill blade
-21 --twenty one -