JP2006108270A - Method of manufacturing flexible printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a flexible printed board having such properties as follows: first, flexible and easily bent; second, can be reduced in weight and thickness while being densified and microfabricated; and third, can be manufactured by simple processes and can be reduced in cost. <P>SOLUTION: In this manufacturing method, a penetration hole 5 for a through hole 4 is formed in a film base material 3 consisting of a double-sided copper clad laminate which is such that copper foils 2 are pasted on both faces of an insulating film 1 having a flexibility, and then the inner wall surface of the through hole 5 is treated for electric conduction. Next, with the whole surface of one face of the film base material being covered by a masking layer 13, the inner wall surface of the through hole 5 and the copper foil 2 on the opposite side of the film base material are applied with electric copper plating 6 and then copper is deposited. After removing the masking layer 13, a circuit pattern 7 is formed. For the masking layer 13 working as a plating resist, an alkali-soluble dry film, a PET resin film with an adhesive, etc. are used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a flexible printed circuit board. That is, it is related with the manufacturing method of a flexible printed wiring board by which the circuit pattern was formed on both surfaces of the insulating film provided with the softness | flexibility.

<Technical background>
Flexible printed circuit boards are flexible and flexible, and, like other printed circuit boards, the progress of high precision, high functionality, ultra-thinness, and light weight is remarkable, and circuit patterns are densified and miniaturized. Is remarkable.
In the flexible printed circuit board, as in other printed circuit boards, a number of through holes, which are fine through holes, are formed for connecting circuit patterns on both sides and for mounting semiconductor components and the like. And in the manufacturing process of a flexible printed circuit board, a panel plating method and a button plating method are typical about manufacture of such a through hole.
FIG. 3 is a front cross-sectional explanatory view showing an enlarged main part for explaining a method for manufacturing a flexible printed circuit board of this type of conventional example. And (1) figure shows the flexible printed circuit board manufactured by the panel plating method. (2) The figure shows the covering process of the button plating method, (3) The figure shows the exposure process of the button plating method, and (4) The figure shows the flexible printed circuit board manufactured by the button plating method.

<About panel plating method>
In the panel plating method shown in FIG. 3 (1), → First, about the film base 3 in which the copper foil 2 is pasted on both surfaces (the front surface and the back surface) of the insulating film 1 → the through hole for the through hole 4 After the hole 5 is drilled, the inner wall surface of the through hole 5 is subjected to a conductive treatment. For example, copper plating is performed by electroless copper plating or carbon treatment is performed by direct plating.
→ Then, the film substrate 3 was subjected to electrolytic copper plating 6. Therefore, the film base 3 was subjected not only to the inner wall surface of the through-hole 5 subjected to the conductive treatment, but also to the copper foil 2 on both sides being subjected to electrolytic copper plating 6.
→ The film base 3 is made of such electrolytic copper plating 6 to make the through-hole 5 conductive and obtain conductivity on both sides, and then follow known steps such as exposure, development, etching, peeling, etc. A circuit pattern 7 was formed, and the flexible printed board A shown in FIG. 3A was manufactured.

<About button plating method>
In the button plating method shown in FIGS. 3 (2), (3), and (4), first, as in the above-described panel plating method, copper foil is formed on both surfaces (front and back surfaces) of the insulating film 1. For the film substrate 3 to which 2 is attached, after the through hole 5 for the through hole 4 is drilled, the inner wall surface of the through hole 5 is subjected to a conductive treatment. For example, the inner wall surface is treated with carbon by direct plating.
Then, as shown in FIG. 3 (2), after coating both sides of the film substrate 3 with the photosensitive dry film 8 with a separator, → further outside thereof, in FIG. 3 (3) As shown, a photomask film 9 as a negative film is applied while being aligned, exposed and developed with a developer.
→ Then, the copper electroplating 6 was carried out with the photosensitive dry film 8 remaining and cured except for the vicinity of the opening of the through hole 5 as a plating resist. → As a result, the electrolytic copper plating 6 is selectively carried out only on the inner wall surface of the through hole 5 subjected to the conductive treatment and on the periphery of the openings on both sides of the through hole 5. 5, that is, the electrolytic copper plating 6 is formed in a flange shape and a button shape around the inner wall surface of the through hole 4 and the openings on both sides of the through hole 4.
→ In this way, after the through-hole 5 is made conductive to obtain both-side conduction, the film substrate 3 is formed with the circuit pattern 7 by following known steps, and thus (4) in FIG. The flexible printed circuit board B shown in the figure was manufactured.

《Information on prior art documents》
As a conventional example of such a button plating method, for example, the one disclosed in Patent Document 1 below can be cited.
JP-A-11-195849

By the way, in such a conventional example, the following problems have been pointed out.
<About the first problem>
First, about the manufacturing method of the flexible printed circuit board A by the panel plating method, the problem was pointed out in the softness | flexibility of the manufactured flexible printed circuit board A, and a flexibility.
That is, in the panel plating method, as described above, not only the through hole 5 but also the copper foil 2 on both surfaces (front surface and back surface) of the film substrate 3 is subjected to the electrolytic copper plating 6. That is, in this film base material 3, copper was deposited on the entire outer surface of the copper foil 2 on both sides for forming the circuit pattern 7 in order to make the through hole 5, that is, the through hole 4 conductive.
Therefore, in the manufactured flexible printed circuit board A, the outer surfaces of all the circuit patterns 7 formed on both sides are all electroplated with copper 6, and the flexibility and flexibility are reduced accordingly. I was sorry. Therefore, when the flexible printed circuit board A manufactured by such a panel plating method is used, the flexible wiring board 10 shown in the schematic plan view of FIG. There was a problem.

About the second problem
Secondly, regarding the method of manufacturing the flexible printed circuit board A by the panel plating method, the weight surface and the thick surface of the manufactured flexible printed circuit board A, and the densification and miniaturization surface of the circuit pattern 7 are also provided. The problem was pointed out.
That is, in the panel plating method, as described in the first point, the outer surface of all the circuit patterns 7 formed on both surfaces (the front surface and the back surface) of the manufactured flexible printed circuit board A are entirely covered. Therefore, there is a problem in that the weight is increased and the thickness is increased, which is contrary to the progress of weight reduction and ultrathinning of the substrate.
Moreover, when forming the circuit patterns 7 on both sides in the final process, the electrolytic copper plating 6 formed on the outer surface of the copper foil 2 of the film base material 3 becomes a hindrance to etching and the like, and is miniaturized to that extent. Some pointed out that the circuit pattern 7 is difficult to form.

<< About the third problem >>
Thirdly, regarding the method of manufacturing the flexible printed circuit board B by the button plating method, the manufacturing process is long and complicated, the yield is poor, and a problem has been pointed out in terms of cost.
That is, in the button plating method, as described above, prior to the electrolytic copper plating 6 of the film base 3, an exposure and development process using a photosensitive dry film 8 or a photomask film 9 for plating resist is added. The manufacturing process is complicated and cumbersome. In addition, the alignment of the through hole 5 (position) of the film base 3 and the position of the photomask film 9 (corresponding position) is generally performed visually. It was not easy and very troublesome and annoying.
As described above, the button plating method is an improvement of the above-described difficulty of the panel plating method, and the copper electroplating 6 is performed only in the vicinity of the through hole 4 and is excellent in flexibility and flexibility. There is no problem, and it is possible to cope with higher density and smaller size. However, the process is very complicated and troublesome, the yield is poor, and a big problem is pointed out in terms of cost.

<< About the present invention >>
The manufacturing method of the flexible printed circuit board of this invention is made | formed as a result of an inventor's earnest research effort in order to solve the subject of the said prior art example in view of such a situation.
The film substrate is characterized in that the through hole for the through hole is made conductive, the one side is covered with a masking layer, and then the through hole is plated with copper.
Therefore, the present invention is firstly excellent in flexibility and flexibility, and secondly, it is possible to achieve weight reduction, ultrathinning, high density and miniaturization, and thirdly, the process is simplified and the cost is reduced. It is an object of the present invention to propose a method for manufacturing a flexible printed circuit board, which is superior to the above.

<About each claim>
The technical means of the present invention for solving such a problem is as follows. First, claim 1 is as follows.
In the method for manufacturing a flexible printed board according to the first aspect, a through hole for a through hole is first provided in a double-sided copper-clad laminate, and the inside of the through hole is subjected to a conductive treatment, and then one side is covered with a masking layer. Then, the through holes and the like are plated with copper. Then, the circuit pattern is formed after removing the masking layer.

Claim 2 is as follows. A second aspect of the present invention relates to the method for manufacturing a flexible printed circuit board according to the first aspect, in which the circuit pattern is formed on both surfaces of a flexible insulating film, and includes the following steps.
First, a step of perforating the through hole for a through hole on a film substrate made of a double-sided copper-clad laminate in which a copper foil is attached to both sides of the insulating film, and then an inner wall surface of the through hole And a step of forming a conductive film by a direct plating method or electroless copper plating.
Next, a step of covering the entire surface of one side of the film base material with the masking layer, and then performing electrolytic copper plating on the film base material, the copper foil on the opposite surface side and the inner wall surface of the through hole The conductive film includes a step of depositing copper to obtain conduction of the through hole. And after the peeling process of this masking layer, it goes to the formation process of this circuit pattern about both surfaces of this film base material, It is characterized by the above-mentioned.
Claim 3 is as follows. The method for producing a flexible printed board according to claim 3 is characterized in that, in claim 2, an alkali-soluble film or a PET resin film with an adhesive is used as the masking layer.

<About action>
Since the present invention is configured as described above, it is as follows. In this manufacturing method, a through-hole is formed in a film substrate of a double-sided copper-clad laminate and a conductive coating is formed on the inner wall surface, and then one surface is covered with a masking layer.
Then, in this manufacturing method, the film substrate is subjected to electrolytic copper plating. That is, copper is deposited on the copper foil on the opposite surface side and the conductive coating on the inner wall surface of the through hole, and the through hole is made conductive. Then, the copper foil is patterned to form a circuit pattern.
Therefore, according to the manufacturing method of the present invention, it is as follows.

(1) First, since copper electroplating is performed after masking one surface with a masking layer, the copper foil on one surface is not electroplated with copper.
Therefore, the manufactured flexible printed circuit board has a copper foil on one side, that is, a circuit pattern, which is not electroplated with copper. Therefore, compared with the case where both sides are electroplated with copper, it is rich in flexibility and flexibility. The portion that becomes the bent wiring portion can be smoothly folded or bent.
(2) Secondly, since the circuit pattern on one side of this flexible printed circuit board is not electroplated with copper, the weight is lighter and thinner than the case where both sides are electroplated with copper. Densified and miniaturized circuit patterns can be formed.
(3) Thirdly, in terms of process and method, a masking layer covering process and a peeling process functioning as a plating resist are only added before and after the plating process on one side. Therefore, the process is simplified compared to a method of forming a plating resist using a photomask film, and a troublesome and troublesome alignment operation is not required.

<Features of the present invention>
The method for producing a flexible printed circuit board according to the present invention, as described above, for a film base, → conducts through holes for through holes, → coats one side with a masking layer, and then copper-plats through holes and the like. It is characterized by this.
Therefore, the present invention exhibits the following effects.

<< First effect >>
First, a flexible printed circuit board having excellent flexibility and flexibility is obtained. That is, in the manufacturing method of the present invention, since the copper electroplating is performed after masking one surface of the film substrate, the copper foil on one surface is not electroplated at all.
Like this conventional example of the panel plating method described above, the copper foil of the film base is not subjected to electrolytic copper plating on both the front and back surfaces. Thus, the manufactured flexible printed circuit board is rich in flexibility and flexibility, and can be folded and bent smoothly.

<< Second effect >>
Second, it is possible to obtain a flexible printed circuit board that is reduced in weight, extremely thinned, densified and miniaturized.
That is, in the manufacturing method of the present invention, as described in the first point described above, the circuit pattern on one side of the manufactured flexible printed circuit board is not electroplated with copper.
Therefore, compared to this type of conventional panel plating method, in which the circuit patterns on both sides are entirely plated with copper, a flexible printed circuit board that is lighter and thinner than that is obtained. It is possible to cope with the progress of downsizing and ultrathinning. Furthermore, when forming the circuit pattern on one side, the copper foil is not subjected to electrolytic copper plating, so that etching and the like are smoothed accordingly, and a high-density fine circuit pattern can be formed.

《Third effect》
Third, the process is simplified and the cost is excellent. That is, in the manufacturing method of the present invention, the masking layer covering and peeling processes are only added before and after the plating process.
Unlike the above-described conventional example of the button plating method, since a photomask film is not used for forming a plating resist, the process is simplified correspondingly, and a troublesome and troublesome alignment operation is not required. Therefore, according to the manufacturing method of the present invention, the yield is improved and the cost is reduced.
As described above, the effects exerted by the present invention are remarkably large, such as all the problems existing in this type of conventional example are solved.

《About drawing》
Hereinafter, a method for producing a flexible printed board of the present invention will be described in detail based on the best mode for carrying out the invention shown in the drawings. 1 and 2 serve to explain the best mode for carrying out the present invention.
FIG. 1 is an explanatory front sectional view showing an enlarged main part of one example. (1) FIG. 1 shows a prepared film substrate, (2) FIG. 3 shows a drilling step, (3) FIG. (4) shows the soft etching step, and (5) shows the covering step with the masking layer.
FIG. 2 is an explanatory front sectional view showing an enlarged main part of one example. (1) FIG. 2 shows a plating step, (2) FIG. 2 shows a masking layer peeling step, and (3) FIG. The flexible printed circuit board manufactured through the process is shown. FIG. 4 is a schematic enlarged plan view showing a flexible printed circuit board.

《About flexible printed circuit board F》
First, the flexible printed circuit board F will be described with reference to FIG. In the flexible printed circuit board F, that is, the flexible printed circuit board (FPC), the circuit pattern 7 is formed as a conductor layer on the outer surface of the insulating base material similarly to the rigid rigid printed circuit board.
In the flexible printed circuit board F, the insulating base material, which is a base material, is made of the flexible insulating film 1, and the circuit pattern 7 is formed on both surfaces (the front surface and the back surface, the upper surface and the lower surface, and the opposite surface of the one surface). .
The insulating film 1 which is an insulating base material is provided with flexibility, and its thickness is, for example, about 20 μm to 60 μm, but about 12 μm also appears. The thickness of the copper foil 2 forming the circuit pattern 7 is, for example, about 4 μm to 35 μm. Further, the inter-circuit space between the circuit patterns 7 is also about 10 μm to 30 μm and tends to be miniaturized.
The flexible printed circuit board F has a film shape having flexibility, flexibility, and flexibility as a whole, and is used by being folded or bent three-dimensionally. In addition, as with other printed boards, the progress of high precision, high functionality, finer, ultra-thin, light weight, etc. is remarkable, and the density and miniaturization of the circuit pattern 7 to be formed are remarkable. .
FIG. 4 shows an example of such a flexible printed circuit board F, which is roughly divided into a wiring end portion 11, a bent wiring portion 10, and a wiring end portion 12 in terms of structure area. The central bent wiring portion 10 is actually a portion where the bent wiring portion 10 is practically folded or bent, and terminals 14 are arranged at the ends of the wiring end portions 11 and 12. Further, the bent wiring portion 10 generally has a circuit pattern 7 formed on only one of both surfaces, and the wiring end portion 11 becomes a double-sided wiring portion in which the circuit pattern 7 is formed on both surfaces. And land are arranged.
The illustrated flexible printed circuit board F is used as an optical pickup for reading or writing, for example, in a CD player or a DVD player.
The flexible printed circuit board F is roughly like this.

<< Outline of manufacturing method >>
Hereinafter, with reference to FIG. 1, FIG. 2, etc., the manufacturing method of the flexible printed circuit board F of this invention is demonstrated.
In this manufacturing method, for the film base 3 made of a double-sided copper-clad laminate, first, a through hole 5 for a through hole 4 is first provided, the inside of the through hole 5 is subjected to a conductive treatment, and then one side is masked 13 Then, in this manufacturing method, the electrolytic copper plating 6 is performed in the through hole 5 and the like, the masking layer 13 is removed, and then the circuit pattern 7 is formed.
Such a manufacturing method will be described in further detail below.

<< Regarding Prepared Film Base 3 >>
In the method for manufacturing the flexible printed board F, first, as shown in FIG. 1 (1), a film base 3 is prepared.
The film substrate 3 is made of a double-sided copper-clad laminate in which copper foils 2 are attached to both sides of the insulating film 1. The insulating film 1, that is, the insulating base material, which is a base material, includes a polyimide resin film, an aramid resin film, a liquid crystal polymer film, and other resin films having flexibility and insulating properties. As the copper foil 2, rolled foil, electrolytic foil, special electrolytic foil, plated foil, and the like are used.
Moreover, as such a film base material 3, there are a three-layer material type and a two-layer material type. In the three-layer material, the copper foil 2 is laminated on both surfaces of the insulating film 1 via an adhesive. As the adhesive, an epoxy resin, a halogen-free epoxy resin, a high Tg epoxy resin, or the like is used. In the two-layer material, the copper foil 2 is directly pasted and laminated on both surfaces of the insulating film 1. The two-layer material is manufactured by a casting method, a laminator method, a metalizing method (sputtering method), or the like.
The film substrate 3 is as described above.

《About drilling process》
Next, in this manufacturing method, as shown in FIG. 1 (2), the through hole 5 for the through hole 4 is punched in the film base material 3 thus prepared.
The through holes 4 are formed of fine holes penetrating between both surfaces (front and back surfaces, upper and lower surfaces, and one surface opposite to one surface) of the flexible printed circuit board F, and a very large number of the flexible printed circuit boards F are formed. The through-hole 4 is used for conductive connection between the circuit patterns 7 on both sides and for mounting a semiconductor component or the like mounted on the circuit pattern 7. The diameter is about 0.5 mm to 0.2 mm or less. The diameter is about 0.1 mm by the drill method, and about 0.05 mm is also seen by the laser method.
The through hole 5 to be used for such a through hole 4 is first perforated with respect to the film substrate 3. For this drilling, a drill, a laser, or the like is used, and is performed for each sheet or by NC processing of Roll to Roll.
The drilling process is performed in this way.

<< Regarding Step of Forming Conductive Film 15 >>
Next, in this manufacturing method, as shown in FIGS. 1 (3) and 4 (4), the inner wall surface of the through-hole 5 is formed on the film base material 3 in which the through-hole 5 has been drilled. In addition, the conductive film 15 is formed by a direct plating method or electroless copper plating.
In the case of the direct plating method shown in the drawing, first, as shown in FIG. 1 (3), the entire surface of the film substrate 3, that is, the outer surface of the copper foil 2 and the inner wall surface of the through hole 5 on both surfaces of the film substrate 3. The entire surface is continuously treated with carbon 16 to give fine irregularities of carbon 16.
Then, as shown in FIG. 1 (4), soft etching is performed, and the carbon 16 on the outer surface of the copper foil 2 is removed together with the outer surface of the copper foil 2 (a very thin partial surface of the copper foil 2). Is done. Therefore, the carbon 16 is directly applied to only the inner wall surface of the through hole 5, more specifically, only the surface of the insulating film 1 exposed on the inner wall surface of the through hole 5, and the carbon 16 is attached and remains. Such carbon 16 forms a conductive film 15 on the inner wall surface of the through hole 5.
In this direct plating method, carbon graphite, palladium, or other conductive material may be used instead of carbon 16. In addition, when the conductive film 15 is formed by electroless copper plating regardless of the direct plating method, not only the inner wall surface of the through-hole 5 but also the outer surfaces of the copper foils 2 on both sides are electroless copper plated.
Thus, the conductive film 15 is formed.

<Coating process with masking layer>
Then, in this manufacturing method, as shown in FIG. 1 (5), the entire surface of the film substrate 3 having the conductive film 15 formed in the through hole 5 is covered with the masking layer 13. Is done. That is, the film substrate 3 is entirely covered on one side (the back side and the bottom side in the illustrated example) by attaching the masking layer 13.
As the masking layer 13, an alkali-soluble dry film, a PET (polyethylene terephthalate) resin film with a slightly sticky adhesive, or other materials that can be dissolved and removed with an alkaline liquid stripping solution is used. The film base 3 is thus coated on one side with the masking layer 13.
In this way, coating with the masking layer 13 is performed.

<< About plating process >>
Then, in this manufacturing method, as shown in FIG. 2 (1), electrolytic copper plating 6 is performed on the film base 3 covered on one side with the masking layer 13. Therefore, the through-hole 5 is made conductive by depositing copper on the copper foil 2 on the opposite surface side and the conductive coating 15 on the inner wall surface of the through-hole 5. So-called interlayer conduction between the front and back sides is obtained.
That is, the electrolytic copper plating 6 is carried out on the part of the film base 3 that is not masked by the masking layer 13 that functions as a plating resist. Accordingly, with respect to the film substrate 3, the outer surface of the copper foil 2 on the opposite surface (surface, upper surface in the illustrated example) side and the conductive coating 15 that forms the inner wall surface of the through-hole 5 are entirely and continuously formed. Copper is deposited and electrolytic copper plating 6 is performed.
Thus, the electrolytic copper plating 6 is implemented.

<< About the peeling process >>
Next, in this manufacturing method, as shown in FIG. 2B, the masking layer 13 is peeled off.
That is, on the film base 3 on which the electrolytic copper plating 6 has been performed, the masking layer 13 used as a plating resist is peeled off and peeled off and removed by spraying an alkaline stripping solution.
Thus, the masking layer 13 is peeled off.

<About the patterning process>
In this manufacturing method, the circuit pattern 7 is formed on both surfaces of the film substrate 3 as shown in FIG.
That is, by following known steps, for example, by following known steps such as photosensitive dry film pasting, exposure, development, etching, peeling, etc., both sides of the film base 3 are left. A circuit pattern 7 is formed of the copper foil 2.
Therefore, for example, the flexible printed board F shown in FIG. 2 (3) and FIG. 4 is manufactured. And the flexible printed circuit board F manufactured in this way is used for a semiconductor component etc. mounted.
In this way, patterning is performed.

《Action etc.》
The manufacturing method of the flexible printed circuit board F of this invention is comprised as demonstrated above. Therefore, it becomes as follows.
In this manufacturing method, first, a through hole 5 for a through hole 4 is formed on a film substrate 3 of a double-sided copper-clad laminate (see FIG. 1 (1)) (see FIG. 1 (2)). ) After forming the conductive coating 15 on the inner wall surface (see FIGS. 1 (3) and (4)), one side is covered with the masking layer 13 (FIG. 1 (5)). See).
Then, in this manufacturing method, the film base 3 is subjected to electrolytic copper plating 6. That is, with respect to the film base 3 coated on one side with the masking layer 13, copper is deposited in a limited and continuous manner only on the copper foil 2 on the opposite side and the conductive coating 15 on the inner wall surface of the through hole 5. Then, the copper electroplating 6 is performed, and the through hole 5 is conducted between the one surface and the opposite surface (see FIG. 2 (1)).
Then, after peeling off the masking layer 13 (see FIG. 2B), the copper foil 2 is patterned to form a circuit pattern 7 (see FIG. 2C3).
Therefore, according to the manufacturing method of the present invention, the following first, second and third are obtained.

(1) First, in this manufacturing method, one side of the film base 3 is covered and masked with a masking layer 13 functioning as a plating resist, and the electrolytic copper plating 6 is performed while limiting the area. Therefore, the copper foil 2 on one side of the film substrate 3 does not deposit copper and is not subjected to electrolytic copper plating 6 at all.
Therefore, the flexible printed circuit board F manufactured by this manufacturing method has the circuit pattern 7 formed on both surfaces thereof with such a copper foil 2, and the circuit pattern 7 on one side (for example, the back surface and the bottom surface) There is no electrolytic copper plating 6 on the entire surface, and no copper is deposited. However, the circuit pattern 7 on the opposite side (for example, the front surface or the upper surface) side is entirely plated with copper.
Now, when one side of the flexible printed circuit board F is used as a bent surface, that is, as described above, the bent wiring portion 10 often has the circuit pattern 7 formed only on either side. (1), the circuit pattern 7 of the bent wiring portion 10 is formed on one surface side of the copper electroplating 6 (see (3) of FIG. 2). 6) By forming the copper foil 2 without the copper foil 2), as compared with the case where the copper foil 2 on both sides and the circuit pattern 7 are both electroplated with copper 6, the overall flexibility and flexibility , It is rich in flexibility.
Therefore, for example, with respect to the wiring end portion 11 where the through hole 4 is located at the end portion, the portion that becomes the bent wiring portion 10 at the central portion can be smoothly folded or bent (see FIG. 4).

(2) Second, in the flexible printed circuit board F manufactured by this manufacturing method, the circuit pattern 7 on one side is not subjected to the electrolytic copper plating 6 at all. Therefore, compared with the case where the circuit patterns 7 on both sides are both electroplated with copper 6 and copper is deposited, the weight is lighter and the thickness is reduced accordingly.
Moreover, since the copper foil 2 on one side is not subjected to the electrolytic copper plating 6, etching or the like can be performed more smoothly on the one side than in the case where the copper is deposited by the electrolytic copper plating 6. Therefore, the circuit pattern 7 with higher density and fineness can be formed.

(3) Thirdly, in this manufacturing method, a method of covering one side of the film base 3 with the masking layer 13 is adopted. In other words, in terms of process, the masking layer 13 covering step and the peeling step functioning as a plating resist are only added before and after the plating step.
Therefore, compared to the case of using a photomask film 9 for forming a plating resist (see FIGS. 3 (2), (3), (4), etc.), the manufacturing process is omitted and simplified. In addition, the troublesome and troublesome alignment work of the photomask film 9 and the through hole 5 is also unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory front sectional view showing an enlarged main part of an example of the method for manufacturing a flexible printed circuit board according to the present invention. (2) Figure shows the drilling process, (3) Figure shows the conductive film formation process, (4) Figure shows the soft etching process, (5) Figure shows the masking process The coating process by a layer is shown. FIG. 2 is a front cross-sectional explanatory view enlarging a main part of one example for explaining the best mode for carrying out the invention. FIG. 1 shows a plating process and FIG. 2B shows a masking layer. FIG. 3 (3) shows a flexible printed circuit board manufactured through a patterning process. It is a front cross-sectional explanatory drawing which expanded the principal part for description of the manufacturing method of the flexible printed circuit board of this kind conventional example, and (1) figure shows the flexible printed circuit board manufactured by the panel plating method. (2) The figure shows the covering process of the button plating method, (3) The figure shows the exposure process of the button plating method, and (4) The figure shows the flexible printed circuit board manufactured by the button plating method. It is the plane schematic which showed the flexible printed circuit board and was expanded schematically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating film 2 Copper foil 3 Film base material 4 Thru hole 5 Through-hole 6 Electro copper plating 7 Circuit pattern 8 Photosensitive dry film 9 Photomask film 10 Bending wiring part 11 Wiring edge part 12 Wiring edge part 13 Masking layer 14 Terminal 15 Conductivity Film 16 Carbon A Flexible printed circuit board (conventional example)
B Flexible printed circuit board (conventional example)
F Flexible printed circuit board (present invention)

Claims (3)

  For a double-sided copper-clad laminate, first, a through hole for a through hole is provided, the inside of the through hole is subjected to a conductive treatment, one side is covered with a masking layer, and then the through hole is plated with copper, and the masking is performed. A method of manufacturing a flexible printed circuit board, comprising forming a circuit pattern after removing a layer. A method for producing a flexible printed circuit board according to claim 1, wherein the circuit pattern is formed on both surfaces of an insulating film having flexibility.
First, a step of perforating the through hole for a through hole on a film substrate made of a double-sided copper-clad laminate in which a copper foil is attached to both sides of the insulating film, and then an inner wall surface of the through hole , Forming a conductive film by direct plating or electroless copper plating,
Next, a step of covering the entire surface of one side of the film base material with the masking layer, and then performing electrolytic copper plating on the film base material, the copper foil on the opposite surface side and the inner wall surface of the through hole The conductive film is provided with a step of obtaining conduction of the through hole by depositing copper,
A method for producing a flexible printed circuit board, characterized in that, after the masking layer peeling step, the circuit pattern is formed on both sides of the film base.   3. The method for producing a flexible printed circuit board according to claim 2, wherein an alkali-soluble film or a PET resin film with an adhesive is used as the masking layer. .

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