201138583 六、發明說明： 【發明所屬之技術領域】 [0001] 本發明涉及電路板製作技術，尤其涉及一種具有較好彎 折性能之軟性電路板之製作方法。 【先前技術】 [0002] 隨著聚醯亞胺膜等柔性材料於電子工業中之廣泛應用（ 請參見Sugi mo to，E.於 1989 發表於 IEEE Electrical Insulation Magazine 第 5 卷第 1 期之 “Applica-tions of polyimide films to the electrical ◎ and electronic industries in Japan” )，柔性 電路板（Flexible Printed Circuit Board，FPCB )因具有可彎折、重量輕、佔用空間小、可立體配線等 優點，於筆記本電腦、液晶顯示器、數位相機、移動電 話等消費性電子產品方面具有十分廣泛之應用。 [0003] 柔性電路板通常採用柔性覆銅板（Flexible Copper Clad Laminate，FCCL )製成。市場上常見之柔性覆 q 銅板之厚度一般在50至100微米之間，由於一般製作柔性 電路板之過程中還會於柔性覆銅板之基礎上壓合黏合層 、覆蓋層等材料，如此會進一步增加生產出之柔性電路 板之厚度。而柔性電路板之厚度與柔性電路板之彎折性 能成反比，柔性電路板越厚，就會造成柔性電路板一方 面不易彎折，另一方面彎折多次後容易產生彎折疲勞， 易於失效。 [0004] 有鑑於此，有必要提供一種具有較好彎折性能之軟性電 路板之製作方法。 099113522 表單編號A0101 第3頁/共27頁 0992023868-0 201138583 【發明内容】 [0005] 以下將以實施例說明一種軟性電路板之製作方法。 [0006] —種軟性電路板之製作方法，包括步驟：提供軟性基板 ，所述軟性基板包括基底層與導電層；將所述導電層形 成導電圖形；於所述導電圖形上形成覆蓋層’以使導電 圖形位於基底層與覆蓋層之間；蝕刻所述基底層與覆蓋 層，以減少至少部分基底層之厚度，並減少至少部分覆 蓋層之厚度。 [0007] 本技術方案之軟性電路板之製作方法中，於製作導電圖 形後，蝕刻了基底層與覆蓋層，從而減少了至少部分基 底層之厚度，並減少了至少部分覆蓋層之厚度從而有 效減薄了製成之軟性電路板，可増強軟性電路板之彎折 性能以及使用壽命。 【實施方式】 [_ T面將結合附圖及實施例，對本技術方案提供之設備安 裝資料設計系統作進一步々詳細說明。 剛II參閱圖1，本技術方案實施例提供—種軟性電路板之製 作方法，包括以下步驟： [0010]第一步，請參閱圖2，提供一個軟性基板10。 _]所述軟性基板1〇包括基底層n及貼合於所述基底層心 側之導電層12。所述基底層11用於支撐導電層12，基底 層11之材料為柔崎I基底m常崎料為聚酿 亞胺（Polyimide，PI)，但亦可為聚乙烯對苯二曱酸 乙一醇酯（Polyethylene Terephtalate，PET)、聚 099113522 表單編號A0101 第4頁/共27頁 0992023868-0 201138583 萘二曱酸乙二酯（p〇ly(ethylene naphthalate)， PEN) '聚硫胺（Polyamide)或者其組合物等。所述基底 層11之厚度一般在2〇至50微米之間。所述導電層12用於 形成導電圖形，以實現訊號之傳輸及處理。導電層12一 般為具有較好撓折性之壓延銅箔，但亦可為其他鋁箔、 銀箔或者其他導電材料層。導電層12之厚度一般在10至 30微米之間。 [0012] Ο [0013] [0014] 〇 [0015] 所述基底層11與導電層12之間還可具有一黏膠層（圖未 示），以增強基底層11與導電層12間之黏結力。所述黏 膠層之材料可為環氧樹脂或丙烯酸樹脂。 第二步，請參閱圖3，將所述導電層12形成導電圖形12〇 。導電圖形120可藉由採用雷射直接燒蝕導電層12之方法 形成，亦可藉由採用化學蝕刻導電層12之方法形成。 採用化學姓刻以形成導電圖形12〇之前，通常先於導電層 12表面形成光阻層，並藉由曝光、顯影主序使得光阻層 圖案化，從而露出部分導電層12，再以銅敍刻液餘刻導 電層12露出之區域’從而除去·化之光阻層之後就 獲得了圖案化之導電層12。亦即，將導電層12製成了導 電圖形1 2 0。 第三步，請參閱圖4 ’於所述導電圖形12〇上形成覆蓋層 13 ’以保護所述導電圖形m，並使得導電圖形12〇位於 基底層11與覆蓋層13之間。 所述覆蓋層13之材财為紐材料，可為聚醯亞胺（ Polyimide，PI)、聚乙烯對苯二甲酸乙二醇醋 099113522 表單編號A0101 第5頁/共27頁 0992023868-0 [0016] 201138583 (Polyethylene Terephtalate，PET)、聚萘二甲酸 乙二酯（p〇ly(ethylene naphthalate)，PEN)、聚硫 胺（Polyamide)或者其組合物等。覆蓋層13之材料優選 為與基底層11之材料相同，當然亦可不同。本實施例中 ，基底層11之材料與覆蓋層13之材料均為聚醯亞胺。 [0017] 第四步，蝕刻所述基底層11與覆蓋層13，以減少至少部 分基底層11之厚度，並減少至少部分覆蓋層13之厚度。 [0018] 所述基底層11與覆蓋層13可藉由化學蝕刻液進行蝕刻。 當所述基底層11之材料與覆蓋層13之材料相同時，可採 用該種材料之化學蝕刻液一次性地完成基底層11與覆蓋 層13之蝕刻過程。當所述基底層11之材料與覆蓋層13之 材料不同時，可先採用基底層11材料之化學蝕刻液蝕刻 基底層11，再採用覆蓋層13材料之化學蝕刻液蝕刻覆蓋 層13，從而完成基底層11與覆蓋層13之蝕刻過程。所述 基底層11材料之化學蝕刻液係指可溶解基底層11或可與 基底層11發生反應而去除基底層11之化學溶液。所述覆 蓋層13材料之化學蝕刻液係指可溶解覆蓋層13或可與覆 蓋層13發生反應而去除覆蓋層13之化學溶液。 [0019] 本實施例中，基底層11與覆蓋層13之材料均為聚醯亞胺 ，可採用強鹼性溶液為化學蝕刻液，其主要成份可包括 氫氧化鉀（K0H)與一乙醇胺（Monoethanolamine， MEA)。 [0020] 採用化學蝕刻液蝕刻所述基底層11時，可使整個基底層 11均被化學蝕刻液均勻蝕刻，從而使得整個基底層11被 099113522 表單編號A0101 第6頁/共27頁 0992023868-0 201138583 Ο [0021] 減薄，即使得整個基底層11之厚度被降低，亦可使得部 分基底層11被化學蝕刻液蝕刻，從而使得部分基底層η 被減薄，即使得部分基底層11之厚度被降低。當需要減 少整個基底層11之厚度時，可直接將化學蝕刻液噴淋於 基底層11，或者可將基底層11浸置於化學蝕刻液中，從 而使得化學蝕刻液蝕刻基底層11 ^當僅需減少部分基底 層11之厚度時，可先藉由圖像轉移法於基底層u之表面 形成圖案化之光阻層，從而使部分基底層Π被露出，再 以化學蝕刻液蝕刻露出之基底層u，最後去除圖案化之 光阻層等步驟而實現。 银刻所述覆蓋層13時，亦可使整個覆蓋層13均被化學蝕 刻液均勻钮刻’從而使得整個覆蓋層13被減薄，即使得 整個、覆蓋層13之厚度被降低，亦可是使部分覆蓋層13被 化學姓刻液姓刻，從而使得部分覆蓋層13被減薄，即使 得部分覆蓋層13之厚度被降低。當需要減少整個覆蓋層 13之厚度時’可直接將化學蝕刻液噴淋於覆蓋層13，或 Ο 者可將覆蓋層13浸置於化學姓刻液中，從而使得化學钮 刻液蝕刻覆蓋層13。當僅需減少部分覆蓋層13之厚度時 ，可先藉由圖像轉移法於覆蓋層13之表面形成圖案化之 光阻層，從而使部分覆蓋層13被露出，再以化學蝕刻液 蝕刻露出之覆蓋層13，最後去除圖案化之光阻層等步驟 而實現》 本實施例中，以去除中央部分之基底層11與中央部分之 覆蓋層13為例’說明蝕刻基底層11與覆蓋層13之具體步 驟。首先，請參閱圖5,於基底層11表面以壓合、貼覆、 099113522 表單編號A0101 第7頁/共27頁 0992023868-0 [0022] 201138583 塗布或其他方法形成第—光阻層i4，於覆蓋層i3表面以 壓合、貼覆、塗布或其他方法形成第二光阻層15。所述 第-光阻層14與第：光阻層15可為正型光阻，亦可為負 型光阻。本實施财，僅以正型歧為例，說明其後之 曝光、顯影等工序。其次，請參閱圖6，藉由第一光罩16 對第-光阻層U進行曝光，藉由第二光罩17對第二光阻 層15進行曝光。所述第一光軍16具有第一通孔ΐ6ι，所述 第—通孔161所在區域與基底層11待減薄之區域相對應。 所述第二光罩17具有第二通孔171，所述第二通孔⑺所 在區域與覆蓋層13待減薄之區域相對應。本實施例中， 第-通孔161位於第-光罩16之中央部位，第二通孔m 位於第二光罩17之中央部位。曝光時，與第-通孔161及 第之光阻受到光線照射，發生分解反應， 而沒有受到光線照射之光阻則不發生反應。再次，請參 閱圖7以第-嘴淋系統18於基底層u與覆蓋層^之表面 喷淋顯影液’發生了分解反應之光阻於顯影液中具有高 溶解度，可被顯影液溶解；而未發生分解反應之光阻則 於顯影射具有低轉度，何_雜賴。因此， 經過顯衫工序後’第一光阻層14於與第一通孔對應之 區域形成第三通孔141，亦即，形成了圖案化之第一光阻 層14。第二光阻層15於與第二通孔171對應之區域形成第 四通孔151亦即，形成了圖案化之第二光阻層。所述 第三通孔141位於第一光阻層14之中央區域，所述第四通 孔151位於第一光阻層！5之中央區域，如圖8所示。然後 β參閱圖9 ’以第二喷淋系統19於基底層丨丨與覆蓋層13 0992023868- 之表面噴淋化學糊液，由於第三通孔141處之基底層η 099113522 表單編號Α0101 第8頁/共27頁 201138583 與第四通孔151處之覆蓋層13暴露於化學蝕刻液中，可被 化學蝕刻液溶解或與化學蝕刻液發生反應而去除。而其 他區域之基底層11與覆蓋層13則被剩餘之第一光阻層14 或第二光阻層15覆蓋，不與化學蚀刻液接觸，亦不會被 化學蝕刻液蝕刻。從而，可於基底層丨丨之中央區域形成 第一開口 111，於覆蓋層13之中央區域形成第二開口 131 ，如圖10所示。如此，則減薄了部分之基底層u與部分 之覆蓋層13。所述第一開口 iU為不貫穿基底層丨丨之盲槽 ，所述第二開口 131為不貫穿覆蓋層13之盲槽，亦即，所 〇 述導電圖形120不暴露於第一開口 111與第二開口 131中 。所述第一開口 111之深度在5至15微米之間，所述第二 開口 131之深度亦一般在5至15微米之間。最後，於去除 圖案化之剩餘第一光阻層14與第二光阻層15之後，就獲 得了撓折性能較好之軟性電路板1〇〇，如圖u所示。 _] -併參閱圖U至圖13，本實施例中，所述軟性電路板 100具有依次連接之第一連接區101、撓折區1〇2以及第 〇 二連接區103。所述第一連接區101用於與-個電子元器 件或者用於與一個硬性電路板電連接，所述第二連接區 103用於與另一個電子元器件或者用於與另一個硬性電路 板電連接。所述撓折區丨02連接於第一連接區1〇1與第二 連接區103之間，並對應於所述基底層11之第一開口 lu 與覆蓋層13之第二開口 13卜亦即，第—開口⑴與第二 開口 131均位於撓折區1G2 n使得所述撓折區1〇2 之厚度小於第-連接區1Q1之厚度，亦小於第二連接區 1〇3之厚度。如此，即可使得撓折區1〇2之柔性優於第一 099113522 表單編號A0101 第9頁/共27頁 0992023868-0 201138583 連接區101之柔性，亦優於第二連接區1 03之柔性。亦即 ，撓折區10 2具有優良之彎折性能，於經受多次地折撓後 亦不易發生疲勞’不易失效’從而可進一步地增加軟性 電路板100之使用壽命。 [0024] 當然，本領域技術人員可以理解，若使得基底層丨丨整體 之厚度均被減薄’覆蓋層13整體之厚度均被減薄，亦可 獲得具有優良之彎折性能之軟性電路板。 [〇〇25] 本技術方案之軟性電路板之製作方法中，於製作導電圖 形後，蝕刻了基底層與覆蓋層，從而降低了至少部分基 底層之厚度，並降低了至少部分覆致層之厚度，從而有 效減薄了製成之軟性電路板，可增強軟性電路板之彎折 性能以及使用壽命。 [0026] 综上所述，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園。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】 [0027] 圖1為本技術方案實施例提供之軟性電路板之製作方法之 流程示意圖。 [〇〇28]圖2為本技術方案實施例提供之包括基底層與導電層之軟 性基板之剖面示意圖。 [0029]圖3為將圖2之軟性基板之導電層形成導電圖形後之剖面 示意圖。 099113522 表單編號A0101 第10頁/共27頁 0992023868-0 201138583 [0030] 圖4為於圖3之導電圖形上形成覆蓋層後之剖面示意圖。 [0031] 圖5為於圖4之基底層與覆蓋層上分別形成光阻層之後之 剖面示意圖。 [0032] 圖6為採用光罩曝光光阻層之剖面示意圖。 [0033] 圖7為對曝光後之光阻層顯影時之示意圖。 [0034] 圖8為顯影後之光阻層之剖面示意圖。 [0035] 圖9為對顯影後之軟性基板進行蝕刻時之示意圖。 Ο [0036] 圖10為蝕刻後之軟性基板之剖面示意圖。 [0037] 圖11為去除剩餘之光阻層之後得到之軟性電路板之剖面 示意圖。 [0038] 圖12為圖11之軟性電路板之仰視示意圖。 [0039] 圖13為圖11之軟性電路板之俯視示意圖。 [0040] 【主要元件符號說明】 軟性基板：10 [0041] 基底層：11 [0042] 導電層：12 [0043] 導電圖形：120 [0044] 覆蓋層：13 [0045] 第一光阻層：14 [0046] 第二光阻層：1 5 099113522 表單編號A0101 第11頁/共27頁 0992023868-0 201138583 [0047] 第一光罩：16 [0048] 第一通孔：161 [0049] 第二光罩：17 [0050] 第二通孔：171 [0051] 第三通孔：141 [0052] 第四通孔：151 [0053] 第一喷淋系統：18 [0054] 第二喷淋系統：19 [0055] 第一開口 ： 111 [0056] 第二開口 ： 131 [0057] 軟性電路板：100 [0058] 第一連接區：101 [0059] 撓折區：102 [0060] 第二連接區：103 099113522 表單編號A0101 第12頁/共27頁 0992023868-0201138583 VI. Description of the Invention: [Technical Field] The present invention relates to a circuit board manufacturing technology, and more particularly to a method for fabricating a flexible circuit board having better bending performance. [Prior Art] [0002] With the wide application of flexible materials such as polyimide membranes in the electronics industry (see Sugi mo to, E., 1989, IEEE Electrical Insulation Magazine, Vol. 5, No. 1 "Applica - tions of polyimide films to the electrical ◎ and electronic industries in Japan"), Flexible Printed Circuit Board (FPCB) has the advantages of being bendable, light weight, small footprint, and three-dimensional wiring. There are a wide range of applications in consumer electronics such as liquid crystal displays, digital cameras, and mobile phones. [0003] Flexible circuit boards are usually made of Flexible Copper Clad Laminate (FCCL). The thickness of the flexible coated copper plate commonly found in the market is generally between 50 and 100 microns. Since the flexible circuit board is generally pressed, the adhesive layer, the cover layer and the like are pressed on the basis of the flexible copper clad plate, so that further Increase the thickness of the flexible circuit board produced. The thickness of the flexible circuit board is inversely proportional to the bending performance of the flexible circuit board. The thicker the flexible circuit board, the more difficult the flexible circuit board is to bend on the one hand, and the bending fatigue is easy to occur after bending many times. Invalid. In view of the above, it is necessary to provide a method of fabricating a flexible circuit board having better bending properties. 099113522 Form No. A0101 Page 3 of 27 0992023868-0 201138583 SUMMARY OF THE INVENTION [0005] A method of fabricating a flexible circuit board will be described below by way of embodiments. [0006] A method for fabricating a flexible circuit board, comprising the steps of: providing a flexible substrate, the flexible substrate comprising a base layer and a conductive layer; forming the conductive layer into a conductive pattern; forming a cover layer on the conductive pattern The conductive pattern is positioned between the base layer and the cover layer; the base layer and the cover layer are etched to reduce the thickness of at least a portion of the base layer and reduce the thickness of at least a portion of the cover layer. [0007] In the method for fabricating a flexible circuit board of the present invention, after the conductive pattern is formed, the base layer and the cover layer are etched, thereby reducing the thickness of at least a portion of the base layer and reducing the thickness of at least a portion of the cover layer, thereby effectively The thinned circuit board is made thinner, which can weaken the bending performance and service life of the flexible circuit board. [Embodiment] The device installation data design system provided by the technical solution will be further described in detail with reference to the accompanying drawings and embodiments. Referring to FIG. 1, the embodiment of the present invention provides a method for fabricating a flexible circuit board, comprising the following steps: [0010] In the first step, referring to FIG. 2, a flexible substrate 10 is provided. The flexible substrate 1 includes a base layer n and a conductive layer 12 bonded to the core side of the base layer. The base layer 11 is used to support the conductive layer 12. The material of the base layer 11 is a soft-sand I base m. The raw material is a polyimide (PI), but may also be polyethylene terephthalate. Polyethylene Terephtalate (PET), Poly 099113522 Form No. A0101 Page 4 / Total 27 Page 0992023868-0 201138583 Ethylene naphthalate (PEN) (Polyamide) or Polyamide Its composition and the like. The thickness of the base layer 11 is generally between 2 Å and 50 μm. The conductive layer 12 is used to form a conductive pattern for signal transmission and processing. The conductive layer 12 is generally a rolled copper foil having better flexibility, but may be other layers of aluminum foil, silver foil or other conductive material. The thickness of the conductive layer 12 is generally between 10 and 30 microns. [0012] [0015] [0015] The base layer 11 and the conductive layer 12 may further have an adhesive layer (not shown) to enhance the bonding between the base layer 11 and the conductive layer 12. force. The material of the adhesive layer may be an epoxy resin or an acrylic resin. In the second step, referring to FIG. 3, the conductive layer 12 is formed into a conductive pattern 12A. The conductive pattern 120 can be formed by directly ablating the conductive layer 12 by laser, or by chemically etching the conductive layer 12. Before the chemical pattern is formed to form the conductive pattern 12, the photoresist layer is usually formed on the surface of the conductive layer 12, and the photoresist layer is patterned by exposing and developing the main sequence, thereby exposing the portion of the conductive layer 12, and then The patterned conductive layer 12 is obtained after the engraving of the exposed region of the conductive layer 12, thereby removing the photoresist layer. That is, the conductive layer 12 is formed into a conductive pattern 120. In the third step, referring to Fig. 4', a cover layer 13' is formed on the conductive pattern 12'' to protect the conductive pattern m, and the conductive pattern 12 is placed between the base layer 11 and the cover layer 13. The material of the cover layer 13 is a New Zealand material, which may be Polyimide (PI), polyethylene terephthalate vinegar 099113522 Form No. A0101 Page 5 / Total 27 Page 0992023868-0 [0016 201138583 (Polyethylene Terephtalate, PET), polyethylene naphthalate (PEN), polyamide or a combination thereof. The material of the cover layer 13 is preferably the same as the material of the base layer 11, and may of course be different. In this embodiment, the material of the base layer 11 and the material of the cover layer 13 are both polyimides. [0017] In the fourth step, the base layer 11 and the cover layer 13 are etched to reduce the thickness of at least a portion of the base layer 11 and reduce the thickness of at least a portion of the cover layer 13. [0018] The base layer 11 and the cover layer 13 may be etched by a chemical etching solution. When the material of the base layer 11 is the same as the material of the cover layer 13, the etching process of the base layer 11 and the cover layer 13 can be completed at one time using a chemical etching solution of the material. When the material of the base layer 11 is different from the material of the cover layer 13, the base layer 11 may be first etched by using a chemical etching solution of the material of the base layer 11, and the cover layer 13 may be etched by using a chemical etching solution of the cover layer 13 material. The etching process of the base layer 11 and the cover layer 13. The chemical etching liquid of the material of the base layer 11 means a chemical solution which can dissolve the base layer 11 or which can react with the base layer 11 to remove the base layer 11. The chemical etching solution of the material of the covering layer 13 means a chemical solution which dissolves the covering layer 13 or which can react with the covering layer 13 to remove the covering layer 13. [0019] In this embodiment, the material of the base layer 11 and the cover layer 13 are both polyimine, and a strong alkaline solution can be used as a chemical etching solution, and the main components thereof may include potassium hydroxide (K0H) and monoethanolamine ( Monoethanolamine, MEA). [0020] When the base layer 11 is etched by a chemical etching solution, the entire base layer 11 can be uniformly etched by the chemical etching liquid, so that the entire base layer 11 is 099113522 Form No. A0101 Page 6 / Total 27 Page 0992023868-0 201138583 减 [0021] Thinning, that is, the thickness of the entire base layer 11 is lowered, and part of the base layer 11 is also etched by the chemical etching liquid, so that part of the base layer η is thinned, that is, the thickness of the partial base layer 11 is made. Being lowered. When it is required to reduce the thickness of the entire base layer 11, the chemical etching liquid may be directly sprayed on the base layer 11, or the base layer 11 may be immersed in the chemical etching liquid, so that the chemical etching liquid etches the base layer 11 ^ when only When the thickness of the portion of the base layer 11 needs to be reduced, the patterned photoresist layer may be formed on the surface of the base layer u by image transfer, so that part of the base layer is exposed, and the exposed substrate is etched by a chemical etching solution. The layer u is finally removed by removing the patterned photoresist layer. When the cover layer 13 is engraved, the entire cover layer 13 can be uniformly engraved by the chemical etching solution, so that the entire cover layer 13 is thinned, that is, the thickness of the entire cover layer 13 is lowered, or The partial cover layer 13 is engraved by the chemical surname, so that the partial cover layer 13 is thinned, that is, the thickness of the partial cover layer 13 is lowered. When it is desired to reduce the thickness of the entire cover layer 13, the chemical etching solution may be directly sprayed on the cover layer 13, or the cover layer 13 may be immersed in the chemical surname to make the chemical button etching etching layer. 13. When it is only necessary to reduce the thickness of the portion of the cover layer 13, the patterned photoresist layer may be formed on the surface of the cover layer 13 by image transfer, so that the partial cover layer 13 is exposed and exposed by a chemical etching solution. The cover layer 13 is finally removed by the step of removing the patterned photoresist layer. In this embodiment, the base layer 11 and the central portion of the cover layer 13 are removed as an example to illustrate etching the base layer 11 and the cover layer 13 The specific steps. First, referring to FIG. 5, the first photoresist layer i4 is formed on the surface of the base layer 11 by press-fitting, pasting, 099113522, form number A0101, page 7/27, 0992023868-0 [0022] 201138583 coating or other method. The second photoresist layer 15 is formed by laminating, pasting, coating or other methods on the surface of the cover layer i3. The first photoresist layer 14 and the photoresist layer 15 may be positive photoresist or negative photoresist. In the present embodiment, the process of exposure, development, and the like will be described by taking only the positive type as an example. Next, referring to FIG. 6, the first photoresist layer U is exposed by the first mask 16, and the second photoresist layer 15 is exposed by the second mask 17. The first light army 16 has a first through hole ΐ6ι, and the area of the first through hole 161 corresponds to a region of the base layer 11 to be thinned. The second photomask 17 has a second through hole 171, and the area of the second through hole (7) corresponds to a region where the cover layer 13 is to be thinned. In the present embodiment, the first through hole 161 is located at a central portion of the first photomask 16, and the second through hole m is located at a central portion of the second photomask 17. At the time of exposure, the first through hole 161 and the first photoresist are irradiated with light to cause a decomposition reaction, and the photoresist which is not irradiated with light does not react. Again, referring to FIG. 7, the photo-resistance of the shower solution developed on the surface of the base layer u and the cover layer by the first-mouth shower system 18 has a high solubility in the developer and can be dissolved by the developer; The photoresist that does not undergo a decomposition reaction has a low rotation in the development shot, and is a miscellaneous. Therefore, after the shirting process, the first photoresist layer 14 forms a third via hole 141 in a region corresponding to the first via hole, that is, the patterned first photoresist layer 14 is formed. The second photoresist layer 15 forms a fourth via hole 151 in a region corresponding to the second via hole 171, that is, a patterned second photoresist layer is formed. The third through hole 141 is located in a central region of the first photoresist layer 14, and the fourth through hole 151 is located in the first photoresist layer! The central area of 5 is shown in Figure 8. Then, referring to FIG. 9 'spraying the chemical paste liquid on the surface of the base layer 丨丨 and the cover layer 13 0992023868- by the second spray system 19, since the base layer η 099113522 at the third through hole 141 is the form number Α0101, page 8 The cover layer 13 at the fourth via hole 151 is exposed to the chemical etching solution and can be removed by the chemical etching solution or reacted with the chemical etching solution. The base layer 11 and the cover layer 13 of other regions are covered by the remaining first photoresist layer 14 or second photoresist layer 15, are not in contact with the chemical etching solution, and are not etched by the chemical etching solution. Thereby, the first opening 111 can be formed in the central portion of the base layer, and the second opening 131 can be formed in the central portion of the cover layer 13, as shown in FIG. Thus, a portion of the base layer u and a portion of the cover layer 13 are thinned. The first opening iU is a blind groove that does not penetrate through the base layer, and the second opening 131 is a blind groove that does not penetrate the cover layer 13 , that is, the conductive pattern 120 is not exposed to the first opening 111 and In the second opening 131. The depth of the first opening 111 is between 5 and 15 microns, and the depth of the second opening 131 is also generally between 5 and 15 microns. Finally, after removing the patterned first photoresist layer 14 and the second photoresist layer 15, a flexible circuit board 1 with good flexing performance is obtained, as shown in FIG. _] - and referring to FIG. 9 to FIG. 13, in the embodiment, the flexible circuit board 100 has a first connection area 101, a flex area 1〇2, and a second connection area 103 which are sequentially connected. The first connection area 101 is used for electrical connection with an electronic component or for a rigid circuit board, and the second connection area 103 is used for another electronic component or for another rigid circuit board. Electrical connection. The flexing zone 丨02 is connected between the first connecting zone 1〇1 and the second connecting zone 103, and corresponds to the first opening lu of the base layer 11 and the second opening 13 of the cover layer 13 The first opening (1) and the second opening 131 are both located in the flexing zone 1G2 n such that the thickness of the flexing zone 1〇2 is smaller than the thickness of the first connecting zone 1Q1 and also smaller than the thickness of the second connecting zone 1〇3. In this way, the flexibility of the flexing zone 1〇2 is better than that of the first 099113522. Form No. A0101 Page 9 of 27 0992023868-0 201138583 The flexibility of the connecting zone 101 is also better than the flexibility of the second connecting zone 103. That is, the flexing zone 10 2 has excellent bending properties, and is less prone to fatigue 'fail to fail' after being subjected to multiple times of deflection, thereby further increasing the service life of the flexible circuit board 100. [0024] Of course, those skilled in the art can understand that if the thickness of the entire base layer is reduced, the thickness of the entire cover layer 13 is thinned, and a flexible circuit board having excellent bending performance can also be obtained. . [〇〇25] In the method for fabricating a flexible circuit board of the present invention, after the conductive pattern is formed, the base layer and the cover layer are etched, thereby reducing the thickness of at least a portion of the base layer and reducing at least a portion of the overlying layer The thickness, which effectively thins the finished flexible circuit board, enhances the bending performance and the service life of the flexible circuit board. In summary, the present invention has indeed met the requirements of the invention patent, and the patent application is filed according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the patent application scope of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0027] FIG. 1 is a schematic flow chart of a method for fabricating a flexible circuit board according to an embodiment of the present technical solution. 2 is a schematic cross-sectional view of a flexible substrate including a base layer and a conductive layer according to an embodiment of the present technical solution. 3 is a schematic cross-sectional view showing a conductive layer of the flexible substrate of FIG. 2 after forming a conductive pattern. 099113522 Form No. A0101 Page 10 of 27 0992023868-0 201138583 [0030] FIG. 4 is a schematic cross-sectional view showing a cover layer formed on the conductive pattern of FIG. 5 is a schematic cross-sectional view showing a photoresist layer formed on the base layer and the cover layer of FIG. 4, respectively. [0032] FIG. 6 is a schematic cross-sectional view showing a photoresist layer exposed by a photomask. [0033] FIG. 7 is a schematic view showing development of a photoresist layer after exposure. 8 is a schematic cross-sectional view of a photoresist layer after development. 9 is a schematic view showing a state in which a soft substrate after development is etched. 10 is a schematic cross-sectional view of a soft substrate after etching. 11 is a schematic cross-sectional view of a flexible circuit board obtained after removing the remaining photoresist layer. 12 is a bottom plan view of the flexible circuit board of FIG. 11. 13 is a top plan view of the flexible circuit board of FIG. 11. [Description of main component symbols] Flexible substrate: 10 [0041] Base layer: 11 [0042] Conductive layer: 12 [0043] Conductive pattern: 120 [0044] Cover layer: 13 [0045] First photoresist layer: [0046] Second photoresist layer: 1 5 099113522 Form number A0101 Page 11 / Total 27 page 0992023868-0 201138583 [0047] First mask: 16 [0048] First through hole: 161 [0049] Second Photomask: 17 [0050] Second via: 171 [0051] Third via: 141 [0052] Fourth via: 151 [0053] First sprinkler system: 18 [0054] Second sprinkler system: [0055] First opening: 111 [0056] Second opening: 131 [0057] Flexible circuit board: 100 [0058] First connection area: 101 [0059] Flexing area: 102 [0060] Second connection area: 103 099113522 Form No. A0101 Page 12 of 27 0992023868-0