200824526 九、發明說明： 【發明所屬之技術領域】 本發明涉及一種製作柔性電路板之方法，尤其涉及一 種製作具有斷差結構之柔性電路板之方法。 【先前技術】 柔性電路板（Flexible Printed Circuit Board, FPCB)以其 優異之抗挽曲性能廣泛應用於各種工作時部件之間存在相 對運動之電子産品中以提供電力/訊號傳輸。例如折疊式手 : 機，列印頭，硬碟機讀取頭中。 電子産品小型化之趨勢需要同樣面積電路板所能傳輸 之訊號量越來越高，於不能增加電路板面積之情形下若要 提高信號傳輸量只能增加線路之層數。但層數增加，則其 抗撓曲性能降低，柔性電路板之壽命也降低。因此有必要 開發出具有優異之抗撓曲性能多層柔性電路板。 參閱圖18,爲一種具有斷差結構之柔性電路板結構示 意圖，柔性電路板於不同之區域具有不同之層數，層數少 之區域具有高之抗撓曲性能，層數高之區域可提高同樣面 積之電路板中之線路密度。 參閱圖18-圖23,爲先前技術中積層法製作此種柔性電 路板之方法不意圖。參閱圖18及圖19’將第一覆銅層壓板 (Copper Clad Laminate, CCL) 41、第一粘合層 45、第二 覆銅層壓板42疊層、壓合。參閱圖20及圖21，壓合後， 於第一覆銅層壓板41及第二覆銅層壓板42上貼上幹膜以 蝕刻線路。蝕刻線路時，先於第一覆銅層壓板41及第二覆 200824526 銅層壓板42上分別貼一層幹膜412、422，但由於第一覆銅 層壓板41與第二覆銅層壓板42長度不一致，於第一覆銅 層壓板.41與第二覆銅層壓板42之間存在-個斷差結構， 於斷差結構附近幹膜412結構彎曲而不能緊密貼合於第一 覆銅層壓板41及第二覆銅層壓板42之表面，其間存在一 孔隙46 ’於蝕刻步驟時，蝕刻藥水從此孔隙从中滲入從而 r %：_ 與第一覆銅層壓板41及第二覆銅層壓板42之絕緣層反 應，造成銅層爆開，剝離之問題。 、 囷22再为別於第一覆銅層壓板〇及第二覆銅層 壓板42上積層第一覆銅層壓板43及第二覆銅層壓板44， 才木用上述幹膜法再蝴線路。以此類推，可重複此過程直 至得到預定層數之電路板。 多閱圖23，於得到預定層數之電路板後，於電路板上 形成導通孔47。形成導通孔時需要於鑽好之孔内鑛上導電 f ’電料電層時’第二覆銅層壓板42部分絕緣層表面暴 路於電鍍藥水中，從而於絕緣層表面形成銅屑48。而於第 :覆銅層壓板43及第二覆銅層壓板44上製作最外層線路 =爲保護第二覆銅層壓板42之樹脂層，會用幹膜貼於樹 :層士，但銅屑48會刺穿幹膜，如果第二覆銅層壓板42 又面皆覆有銅箔，則蝕刻藥水蝕刻銅層造成斷線。 有鑒於此，有必要提供一種於製作過程中避免 電路板内部銅層與絕緣層産生損害，並斯 結構之製作柔性電路板之方法。 有斷差 8 200824526 【發明内容】 以·下以實施例說明於製作過程中避免對柔性電路板内 部銅層·與絕緣層產生損害，並且可形成具有斷差結構之製 作柔性電路板之方法。 & 該方法包括以下步驟：提供第一覆銅層壓板、黏接層及 第二覆銅層壓板，該第一覆銅層壓板包括絕緣層及形成於其 上之銅箔，第二覆銅層壓板包括絕緣層、形成於絕緣層上2 r銅箱及截止層；於該黏接層上預定區域形成開口，該黏接層 、包括一靠近該開口之側邊；將第一覆銅層壓板、黏接層及^ 二覆銅㈣板依:欠疊層並壓合，使得職止層與該黏接層連 接；於第一覆銅層壓板及第二覆銅層壓板的銅箔上形成線路 得到預製電路板；利用雷射對準該側邊切割預製電路板中處 於第-覆銅層驗-側之各層形成—切σ;沿預定之邊界裁 切該預製電路板形成一側面，該側面與該切口於該預製電路 板上定義出-與該開口相對應之去除區，該去除區於該斷面 4形成後即可從該預製電路板上脫落從而形成一具有斷差結 構之柔性電路板。 口 相較於先前技術，該製作具有斷差結構之柔性電路板 之方法具有如下優點：首先，於電路板上形成線路或者通 孔時，電路板上並無斷差結構，因此可㈣免銅層剝離、 斷線等不良之產生，可提高產品良率。其次，於電路板上 形成線路或者通孔時，電路板上也無預先形成之刀口，可 避，形，線路或者通孔㈣讀刀。巾以，造成電路板 不义。取後，利用雷射進行切割可以得到更加精確之斷面 9 200824526 尺寸。 【實施·方式】 以·下結合圖1-圖11對本技術方案第一實施例之製作具 有斷差結構之電路板之方法作出詳細說明。 參閱圖1，首先，提供第一覆銅層壓板（Copper Clad Laminate，CCL) 11、第二覆銅層壓板ι2及黏接層μ，並 於黏接層15上形成一開口 152,黏接層15於開口 152處有 一側邊154。根據需要，開口 152可爲各種形狀，例如矩形、 圓形、方形。本實施例中開口 152形狀爲矩形。第一覆銅 層壓板11包括絕緣層111及形成於絕緣層m上之銅箔 112。第二覆銅層壓板12包括絕緣層ι21及分別形成於絕 緣層121兩表面上之銅箔122及銅箔124。 絕緣層111、絕緣層121及黏接層15最常用之材質爲 聚酰亞胺（Polyimide，PI)，但還可選自以下聚合物如鐵氟龍 (Teflon)、聚硫胺（Polyamide)、聚甲基丙烯酸曱酯 (Polymethylmethacrylate)、聚碳酸酯（Polycarbonate)、聚乙 烯對苯二酸酯（Polyethylene Terephtalate，PET)或聚酰亞胺-聚乙烯-對苯二曱醋共聚物 （Polyamide polyethylene-terephthalate copolymer)或者其組合物。覆銅 層壓板也可以用其他覆銅層壓板代替，如銀、金等。銅箔 或者其他金屬箔一般藉由沈積之方法如電鍍、濺鍍，或者 壓合之方法形成於絕緣層上。 參閱圖2，將第一覆銅層壓板11、黏接層15及第二覆 銅層壓板12依次疊層並壓合。疊層時絕緣層111及截止銅 200824526 v备124分別緊貼於點接層Μ之兩表面上。 參.閱圖3’於銅箔112及銅箔122上形 112上與側ϋ 154相_應之區域形成—^路並於銅羯 114。形成線路時可採用姓刻工藝，1且體包=112之凹槽 恤）、曝光、顯影、⑽】等步驟。凹样括貼幹膜伽 刻形成，也可於形成線路之前或者形成線路之後以推 敍妃鋁石榴石（Nd.YAG)雷射燒钱而製成。 r 參閱圖4，於銅箱112上依次疊層黏接層16及第一覆 銅層壓板13,於第二銅箔122上疊層黏接層17及第二覆銅 層壓板14,然後壓合。第一覆鋼層壓板13包括絕緣層i3i 及形成於絕緣層131上之銅箔132。第二覆銅層壓板14包 括絕緣層141及形成於絕緣層141上之銅箔142。絕緣層 131與黏接層16相鄰。絕緣層141與黏接層17相鄰。 參閱圖5，形成導通孔is以導通銅箔112，銅箔122， 銅、洛132及銅箔142。導通孔18可採用機械鑽孔或者雷射 燒孔（Laser-ablation)等方式形成。導通孔18内壁上可鍍上 導電層，如鍍上一層銅。或者於導通孔18内填充導電膠。 本實施例當中，導通孔18内壁上鍍有銅層。 參閱圖6,於銅箔132及銅箔142上形成線路並同時於 銅磘132上與側邊154及凹槽114相對應之區域形成凹槽 134得到預製電路板19。凹槽134可以與線路同時蝕刻形 成，也可於形成線路之前或者形成線路之後以Nd:YAG雷 射燒出。 一併參閱圖7及圖8，以二氧化碳雷射對準凹槽134 11 200824526 切割絕緣層131、黏接層16及絕緣層111形成切口 191。 一般情·況下，二氧化碳雷射於絕緣層/黏接層中鑽孔時之鑽 孔速度.很快，惟其波長不同於能被銅箔吸收之波長，因此銅 箔124不能被二氧化碳雷射切割，從而可以作爲截止層， 當切割完絕緣層111後，銅箔124可防止二氧化碳雷射進 一步向下切割。 圖9係圖10中之預製電路板之俯視示意圖。邊界192 内之部分爲最終成品電路板所在之區域。參閱圖9，沿邊界 192裁切預製電路板19去除預製電路板19上邊界192以外 之部分。裁切後於預製電路板19上形成侧面194。參閱圖 11，側面194以及切口 191共同於預製電路板19上圍成去 除區193。而此時由於去除區193剛好對應於開口 152上， 去除區193也就與預製電路板19之間脫離連結關係。去除 區193即可從預製電路板19上脫脫落而得到具有斷差結構 之柔性電路板100。裁切時可採用模具沖切或者刀具切割等 方式。 本實施例當中，銅箔112及銅箔132中分別形成凹槽 114及凹槽134，因此二氧化碳雷射可以順利切割絕緣層 111、絕緣層131及黏接層16，由於截止銅箔124之存在， 可防止二氧化碳雷射進一步向下切割而破壞電路板100。 本實施當中形成的為部分區域爲四層，另一部分區域 爲兩層之柔性電路板。然而於第一覆銅層壓板11、粘接層 15及第二覆銅層壓板12壓合並形成線路之後，即可利用雷 射切割第一覆銅層壓板11從而得到一部分爲兩層，一部分 12 200824526 爲單層之柔性電路板。或者於第—覆銅層壓板i3與第 銅壓板·14上還積層另外的覆銅層壓板。其他處理過程後綠 與第-實施例之製作具有斷差結構之柔性電路板之方法= 似。 本實施例當中，於黏接声1 s τζ ,、 舶接層15兩表面上分別積層覆銅芦 壓板並在覆銅層壓板的銅箱上形成、線路。可選的，也可二 積層已經預先形成有線路的覆銅層壓板。其他㈣ = 一實施例相似。 相較於先前技術，本實施例之製作具有斷差 性電路板之方法具有如下優點：Μ，於電路板上形成= 路或者通孔時’電路板上並無斷差結構，因此可以避免銅 層剝離、斷線等不良之産生，可提高產品良率。其次，: 電路板上形成線路或者軌時，電路板上也無㈣ ^ 刀口，可避免形祕路或者通孔時藥水從刀口中侵入= =:。最後’利用雷射進行切割可以得到更二 第二實施例之製作具有斷差結構之柔性電路板 與弟-實施例相似，不同之處在於，參閱圖12， 層堡板22包括緣層221，形成於絕緣層221上之 = 及截止層224。截止層224形成於與侧邊2Μ對齊之^八^ 域内。截止層224之材料可選自金屬如鉻、銅、刀: 二層224可以用電鐘或者_之方法形成於第二絕缘： 日守，製作截止層224時，事先貼上—層掩膜，、= 截止層224之區域’再進行電錢或者係 = 13 200824526 層224之後即可將掩膜去除。 參·閱圖13，截止層224所起作用與銅箔124相似，防 止雷射.完成切割任務後進一步破壞電路板。利用截止層224 取代銅箔124，則電路板可以做的更薄，其抗撓曲性能也更 強。 第三實施例之製作具有斷差結構之柔性電路板之方法 與第二實施例相似，不同之處在於，於銅箔312、銅箔332 上並不形成與側邊354對齊之凹槽。 參閱圖14至圖17,當形成預定層數之預製電路板之 後，以兩種不同之雷射對準側邊354進行切割，其中第一 雷射381用於切割銅箔312及銅箔332,第二雷射382用於 切割黏接層36、絕緣層311及絕緣層331。第一雷射爲固 體雷射如Nd:YAG雷射，第二雷射爲氣體雷射如二氧化碳 雷射。由於NchYAG雷射適合切割銅箔，但其頻率不同於 絕緣層311或者黏接層36材質，因此很難切割絕緣層311 或者黏接層36，而二氧化碳雷射剛好與此相反。 綜上所述，本發明確已符合發明專利之要件，遂依法 提出專利申請。惟，以上所述者僅為本發明之較佳實施方 式，自不能以此限制本案之申請專利範圍。舉凡熟悉本案 技藝之人士援依本發明之精神所作之等效修飾或變化，皆 應涵蓋於以下申請專利範圍内。 【圖式簡單說明】 圖1至圖11係第一實施例之製作具有斷差結構之柔性 14 200824526 電路板之方法示意圖。 圖-12至圖13係第二實施例之製作具有斷差結構之柔 性電路板之方法示意圖。 圖14至圖17係第三實施例之製作具有斷差結構之柔 性電路板之方法示意圖。 圖18至圖23係先前技術製作具有斷差結構之柔性電 路板之方法示意圖。 【主要元件符號說明】 111，211，121，221，131，331，141 112,212,312，122,222，132,332，142，124 15,25，16,36，17 154,254,354 114,134 導通孔 18 19 切口 191 192 侧面 194 224 第一雷射 381 382 第一覆銅層壓板 11，13,21 第二覆銅層壓板 12, 14,22 絕緣層 銅箔 黏接層 側邊 凹槽 預製電路板 邊界 截止層 第二雷射 15200824526 IX. Description of the Invention: [Technical Field] The present invention relates to a method of fabricating a flexible circuit board, and more particularly to a method of fabricating a flexible circuit board having a stepped structure. [Prior Art] Flexible Printed Circuit Board (FPCB) is widely used in electronic products with relative motion between components to provide power/signal transmission with its excellent buckling resistance. For example, a folding hand: a machine, a print head, and a hard disk drive read head. The trend toward miniaturization of electronic products requires that the amount of signals that can be transmitted by the same area of the board is getting higher and higher. If the board area is not increased, the signal transmission amount can only be increased to increase the number of layers. However, as the number of layers is increased, the flexural resistance is lowered and the life of the flexible circuit board is also lowered. Therefore, it is necessary to develop a multilayer flexible circuit board having excellent flexural resistance. Referring to FIG. 18, it is a schematic diagram of a flexible circuit board structure with a fault structure. The flexible circuit board has different layers in different regions, and the region with a small number of layers has high flexural resistance, and the area with a high number of layers can be improved. Line density in boards of the same area. Referring to Figures 18-23, the method of fabricating such a flexible circuit board by the lamination method of the prior art is not intended. Referring to Figures 18 and 19', a first copper clad laminate (CCL) 41, a first adhesive layer 45, and a second copper clad laminate 42 are laminated and pressed. Referring to Figures 20 and 21, after lamination, a dry film is applied to the first copper clad laminate 41 and the second copper clad laminate 42 to etch the wiring. When the circuit is etched, a dry film 412, 422 is applied on the first copper clad laminate 41 and the second cover 200824526 copper laminate 42, respectively, but the length of the first copper clad laminate 41 and the second copper clad laminate 42 Inconsistent, there is a gap structure between the first copper clad laminate 41 and the second copper clad laminate 42. The dry film 412 is bent in the vicinity of the sectional structure and cannot be closely adhered to the first copper clad laminate. 41 and the surface of the second copper clad laminate 42 with a void 46' therebetween, during which the etching syrup penetrates from the pores so that r %:_ is combined with the first copper clad laminate 41 and the second copper clad laminate 42 The insulation layer reacts, causing the copper layer to burst and peel off. And the second layer of the copper-clad laminate 43 and the second copper-clad laminate 44 are laminated on the first copper-clad laminate and the second copper-clad laminate 42, and the wood is further patterned by the dry film method. . By analogy, this process can be repeated until a predetermined number of layers of boards are obtained. Referring to Fig. 23, after a predetermined number of layers of the circuit board are obtained, via holes 47 are formed on the circuit board. When the via hole is formed, it is necessary to mine the conductive f' electric material layer in the drilled hole. The surface of the second copper clad laminate 42 is in the electroplating solution, thereby forming copper scraps 48 on the surface of the insulating layer. And the outermost layer is formed on the copper-clad laminate 43 and the second copper-clad laminate 44. The resin layer for protecting the second copper-clad laminate 42 is adhered to the tree with a dry film: but the copper shavings 48 will pierce the dry film. If the second copper clad laminate 42 is covered with copper foil on both sides, the etching solution etches the copper layer to cause disconnection. In view of the above, it is necessary to provide a method of fabricating a flexible circuit board by avoiding damage to the copper layer and the insulating layer inside the board during the manufacturing process. There is a gap 8 200824526 [Description of the Invention] The following describes an embodiment to avoid damage to the inner copper layer and the insulating layer of the flexible circuit board during the manufacturing process, and a method of manufacturing a flexible circuit board having a stepped structure can be formed. & The method comprises the steps of: providing a first copper clad laminate, an adhesive layer and a second copper clad laminate, the first copper clad laminate comprising an insulating layer and a copper foil formed thereon, the second copper clad The laminate includes an insulating layer, a 2 r copper box and a cut-off layer formed on the insulating layer; a predetermined area is formed on the adhesive layer, the adhesive layer includes a side adjacent to the opening; and the first copper layer is formed The pressure plate, the adhesive layer and the second copper (four) plate are: laminated and pressed together, so that the service layer is connected with the adhesive layer; on the copper foil of the first copper clad laminate and the second copper clad laminate Forming a circuit to obtain a prefabricated circuit board; using a laser to align the layers of the side-cutting prefabricated circuit board on the first-copper layer to form a side-cut σ; cutting the prefabricated circuit board along a predetermined boundary to form a side surface The side surface and the slit define a removal area corresponding to the opening on the prefabricated circuit board. After the section 4 is formed, the removal area can be detached from the prefabricated circuit board to form a fault structure. Flexible circuit board. Compared with the prior art, the method for fabricating a flexible circuit board having a stepped structure has the following advantages: First, when a circuit or a via hole is formed on a circuit board, there is no fault structure on the circuit board, so (4) copper-free The occurrence of defects such as layer peeling and wire breakage can improve product yield. Secondly, when a circuit or a via is formed on the circuit board, there is no pre-formed edge on the circuit board, which can avoid the shape, the line or the through hole (4). The towel caused the board to be unjust. After taking it, laser cutting can be used to obtain a more accurate section 9 200824526 size. [Embodiment] A method of fabricating a circuit board having a stepped structure in the first embodiment of the present technical solution will be described in detail with reference to Figs. Referring to FIG. 1, first, a first copper clad laminate (CCL) 11, a second copper clad laminate ι2, and an adhesive layer μ are provided, and an opening 152 is formed on the adhesive layer 15, and the adhesive layer is formed. 15 has a side 154 at the opening 152. The opening 152 can be of various shapes, such as rectangular, circular, square, as desired. The opening 152 is rectangular in shape in this embodiment. The first copper clad laminate 11 includes an insulating layer 111 and a copper foil 112 formed on the insulating layer m. The second copper clad laminate 12 includes an insulating layer ι21 and a copper foil 122 and a copper foil 124 respectively formed on both surfaces of the insulating layer 121. The most common material of the insulating layer 111, the insulating layer 121 and the adhesive layer 15 is polyimide (PI), but may also be selected from the following polymers such as Teflon, Polyamide, Polymethylmethacrylate, Polycarbonate, Polyethylene Terephtalate (PET) or Polyimide-Polyethylene Poly(ethylene terephthalate) copolymer (Polyamide polyethylene- Terephthalate copolymer) or a combination thereof. Copper clad laminates can also be replaced with other copper clad laminates such as silver, gold, and the like. Copper foil or other metal foil is typically formed on the insulating layer by deposition methods such as electroplating, sputtering, or lamination. Referring to Fig. 2, the first copper clad laminate 11, the adhesive layer 15, and the second copper clad laminate 12 are laminated in this order and pressed. The insulating layer 111 and the cut-off copper 200824526 are prepared to be in close contact with the two surfaces of the dot layer. Referring to Fig. 3', the copper foil 112 and the copper foil 122 are formed on the upper surface 112 and the side surface 154. When the line is formed, the process of surname engraving, 1 and the body of the bag = 112, exposure, development, (10), etc. may be employed. The concave sample is formed by the dry film galvanic formation, and can also be made by deriving the yttrium aluminum garnet (Nd. YAG) laser burnt money before or after the formation of the line. r Referring to FIG. 4, the adhesive layer 16 and the first copper clad laminate 13 are sequentially laminated on the copper box 112, and the adhesive layer 17 and the second copper clad laminate 14 are laminated on the second copper foil 122, and then pressed. Hehe. The first steel-clad laminate 13 includes an insulating layer i3i and a copper foil 132 formed on the insulating layer 131. The second copper clad laminate 14 includes an insulating layer 141 and a copper foil 142 formed on the insulating layer 141. The insulating layer 131 is adjacent to the adhesive layer 16. The insulating layer 141 is adjacent to the adhesive layer 17. Referring to FIG. 5, a via hole is formed to turn on the copper foil 112, the copper foil 122, the copper, the loupe 132, and the copper foil 142. The via hole 18 can be formed by mechanical drilling or laser-ablation. A conductive layer may be plated on the inner wall of the via hole 18, such as a layer of copper. Or, the conductive vias are filled in the via holes 18. In this embodiment, the inner wall of the via hole 18 is plated with a copper layer. Referring to Fig. 6, a wiring is formed on the copper foil 132 and the copper foil 142, and a recess 134 is formed on the copper yoke 132 at a region corresponding to the side 154 and the recess 114 to obtain a prefabricated circuit board 19. The recess 134 may be formed by etching simultaneously with the line, or may be fired by a Nd:YAG laser before or after the line is formed. Referring to FIG. 7 and FIG. 8, the slit 191 is formed by cutting the insulating layer 131, the adhesive layer 16, and the insulating layer 111 by the carbon dioxide laser alignment groove 134 11 200824526. Under normal circumstances, the drilling speed of carbon dioxide laser in the insulating layer/adhesive layer is very fast, but its wavelength is different from the wavelength that can be absorbed by the copper foil, so the copper foil 124 cannot be cut by carbon dioxide laser. Thus, it can serve as a cut-off layer, and after the insulating layer 111 is cut, the copper foil 124 can prevent the carbon dioxide laser from further cutting downward. Figure 9 is a top plan view of the prefabricated circuit board of Figure 10. The portion of the boundary 192 is the area where the final finished circuit board is located. Referring to Figure 9, the prefabricated circuit board 19 is cut along the boundary 192 to remove portions of the prefabricated circuit board 19 from the upper boundary 192. A side surface 194 is formed on the prefabricated circuit board 19 after cutting. Referring to Figure 11, side 194 and slit 191 are collectively disposed on prefabricated circuit board 19 as a removal zone 193. At this time, since the removal region 193 corresponds to the opening 152, the removal region 193 is also disconnected from the prefabricated circuit board 19. The removal region 193 can be detached from the prefabricated circuit board 19 to obtain a flexible circuit board 100 having a stepped structure. When cutting, die cutting or tool cutting can be used. In the embodiment, the recess 114 and the recess 134 are respectively formed in the copper foil 112 and the copper foil 132. Therefore, the carbon dioxide laser can smoothly cut the insulating layer 111, the insulating layer 131 and the adhesive layer 16, due to the existence of the cut-off copper foil 124. The carbon dioxide laser can be prevented from further cutting down to damage the circuit board 100. In the present embodiment, a partial circuit is formed in four layers, and the other portion is a two-layer flexible circuit board. However, after the first copper clad laminate 11, the adhesive layer 15 and the second copper clad laminate 12 are pressed and combined to form a line, the first copper clad laminate 11 can be cut by laser to obtain a part of two layers, a part of which is 12 200824526 is a single layer flexible circuit board. Alternatively, an additional copper clad laminate may be laminated on the first copper clad laminate i3 and the second copper press plate 14. Green after the other processes The method of fabricating a flexible circuit board having a stepped structure of the first embodiment is similar. In the present embodiment, a copper-clad laminate is laminated on both surfaces of the bonded layer 15 on the surface of the bonded layer 1 s τ 并 and formed on the copper box of the copper-clad laminate. Alternatively, a copper clad laminate having a line formed in advance may be laminated. Other (4) = An embodiment is similar. Compared with the prior art, the method for fabricating a circuit board having the same has the following advantages: Μ, when a circuit or a via hole is formed on the circuit board, there is no fault structure on the circuit board, so copper can be avoided. The occurrence of defects such as layer peeling and wire breakage can improve product yield. Secondly, when a circuit or a track is formed on the circuit board, there is no (4) ^ knife edge on the circuit board to avoid the intrusion of the syrup from the knife edge when the shape or the through hole is broken ==:. Finally, the cutting of the laser can be used to obtain a flexible circuit board having a stepped structure of the second embodiment, which is similar to the embodiment, except that referring to FIG. 12, the layer board 22 includes a margin layer 221, The = and the cut-off layer 224 are formed on the insulating layer 221. The cut-off layer 224 is formed in a region aligned with the side edges 2Μ. The material of the cut-off layer 224 may be selected from a metal such as chrome, copper, or a knife: the second layer 224 may be formed in the second insulation by an electric clock or a method: the keeper, when the cut-off layer 224 is formed, a layer mask is attached in advance. , = the area of the cut-off layer 224 're-telephone or system = 13 200824526 layer 224 can be removed after the mask. Referring to Figure 13, the cut-off layer 224 functions similarly to the copper foil 124 to prevent laser damage and further damage the board after completion of the cutting task. By replacing the copper foil 124 with the cut-off layer 224, the board can be made thinner and its flexural resistance is also stronger. The method of fabricating a flexible circuit board having a stepped structure of the third embodiment is similar to that of the second embodiment except that a groove aligned with the side edges 354 is not formed on the copper foil 312 and the copper foil 332. Referring to FIGS. 14-17, after forming a predetermined number of prefabricated circuit boards, the cutting is performed with two different laser alignment side edges 354, wherein the first laser 381 is used to cut the copper foil 312 and the copper foil 332. The second laser 382 is used to cut the adhesive layer 36, the insulating layer 311, and the insulating layer 331. The first laser is a solid laser such as a Nd:YAG laser, and the second laser is a gas laser such as a carbon dioxide laser. Since the NchYAG laser is suitable for cutting copper foil, the frequency is different from that of the insulating layer 311 or the adhesive layer 36, so it is difficult to cut the insulating layer 311 or the adhesive layer 36, and the carbon dioxide laser is just the opposite. In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the present invention are intended to be included within the scope of the following claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 11 are schematic diagrams showing the method of manufacturing a circuit board having flexibility of a first embodiment. Fig.-12 to Fig. 13 are views showing a method of fabricating a flexible circuit board having a stepped structure in the second embodiment. 14 to 17 are views showing a method of fabricating a flexible circuit board having a stepped structure in the third embodiment. 18 to 23 are schematic views showing a method of fabricating a flexible circuit board having a stepped structure in the prior art. [Description of main component symbols] 111,211,121,221,131,331,141 112,212,312,122,222,132,332,142,124 15,25,16,36,17 154,254,354 114,134 via hole 18 19 slit 191 192 side 194 224 A laser 381 382 first copper clad laminate 11,13,21 second copper clad laminate 12, 14,22 insulating layer copper foil adhesive layer side groove prefabricated circuit board boundary cutoff layer second laser 15