JP2005060772A - Flexible printed circuit board manufacturing method, and base material for circuit used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed circuit board manufacturing method with which activation of a surface can be omitted when electroless nickel plating is applied to a polyimide resin film, and the adhesion reliability of an electroless nickel plating layer to a copper plating layer deposited on a surface thereof can be enhanced, and a base material for a circuit to be used therefor. <P>SOLUTION: Electroless nickel plating is applied to the surface of a polyimide resin film 1. Electrolytic copper plating or electroless copper plating is applied to the surface of an electroless nickel plating layer 2 while maintaining wetness of the surface of the electroless nickel plating layer 2, and a thin copper plating layer 3 of 0.1-1.0μm thick is deposited thereby to manufacture the base material A for the circuit. Thereafter, a thick electrolytic copper plating layer 4 for forming the circuit is deposited on the surface of the thin copper plating layer 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a flexible printed board and a circuit substrate used therefor.

  Conventionally, the flexible printed circuit board used the thing of the 3 layer base material which laminated | stacked the copper foil for circuit formation on the surface of the polyimide resin film via the adhesive agent. However, in recent years, with the advancement of the electronics industry, demand for materials that can withstand high temperatures has increased, whereas those of the three-layer base material have low heat resistance of the adhesive. Therefore, after the use of the adhesive is stopped and the polyimide resin film is made electroconductive by electroless plating, an electrolytic copper plating for forming a circuit is applied. And as the electroless plating, electroless nickel plating is adopted from the viewpoints of adhesion to polyimide (polyimide resin film) and barrier property against diffusion movement due to heat of copper (electrolytic copper plating) forming a circuit. .

However, nickel (electroless nickel plating) forms a strong oxide film on the surface in a relatively short time in air. When the electrolytic copper plating is performed in such a state that the oxide film is formed on the surface of the electroless nickel plating layer, the oxide film weakens the adhesive force between the electroless nickel plating layer and the electrolytic copper plating layer, The electroless nickel plating layer and the electrolytic copper plating layer are easily peeled off. For this reason, when performing electroless nickel plating, the activation process which removes the said oxide film is normally performed prior to electrolytic copper plating. As this activation treatment, for example, treatment with 10% hydrochloric acid (see Patent Document 1), washing with a solution containing at least one of hypochlorite ion, chlorite ion and perchlorate ion (patent) Reference 2), surface treatment with an aqueous solution containing any one of permanganate, hypochlorite, and peroxosulfate (see Patent Document 3) has been proposed. Then, after the activation treatment, for example, when a flexible printed circuit board is manufactured by a subtractive construction method, as shown in FIG. 11, first, the entire surface of the electroless nickel plating layer 2 is thick for circuit formation. An electrolytic copper plating layer 4 is formed, and then a circuit is formed. In FIG. 11, 1 is a polyimide resin film.
Japanese Patent Application Laid-Open No. Sho 62-115894 (page 3, lower left column, line 7) JP-A-5-327207 (Claim 1) Japanese Patent Laid-Open No. 6-200396 (Claim 1)

  Thus, when electroless nickel plating is performed on the polyimide resin film 1, an activation treatment step for removing the oxide film is usually required prior to subsequent electrolytic copper plating for circuit formation. However, since this activation treatment process uses a highly corrosive acid, there are difficulties in workability and waste liquid treatment.

  Further, when the oxide film on the surface of the electroless nickel plating is strong or uneven, the activation treatment may not sufficiently remove the oxide film, and the electroless nickel plating layer 2 and the electrolytic copper may not be removed. In some cases, peeling from the plating layer 4 cannot be completely prevented.

  The present invention has been made in view of such circumstances. In the case where electroless nickel plating is applied to a polyimide resin film, the activation treatment for the surface is unnecessary, and the electroless nickel plating layer and the surface thereof are formed. It is an object of the present invention to provide a method for producing a flexible printed board capable of enhancing the reliability of adhesion to a copper plating layer and a circuit substrate used therefor.

  In order to achieve the above object, the present invention provides a flexible printed circuit board comprising the steps of applying electroless nickel plating to the surface of a polyimide resin film and applying electrolytic copper plating for circuit formation to the surface of the electroless nickel plating layer In this manufacturing method, after electroless nickel plating is applied to the surface of the polyimide resin film, electrolytic copper plating is applied to the surface of the electroless nickel plating layer while keeping the surface wet of the electroless nickel plating layer. By forming a thin copper plating layer having a thickness of 0.1 to 1.0 μm by the above process, and then, as a first gist, a method for producing a flexible printed board in which electrolytic copper plating for circuit formation is applied to the surface of the thin copper plating layer, A polyimide resin film, a nickel plating layer formed on the surface of the polyimide resin film, The circuit substrate and a thin copper-plated layer of 0.1~1.0μm thickness formed on the surface of the nickel plating layer and a second gist.

  That is, in the method for producing a flexible printed board of the present invention, after electroless nickel plating is performed on the surface of the polyimide resin film, the surface of the electroless nickel plating layer is maintained in a state where the surface of the electroless nickel plating layer is kept wet. In order to apply electrolytic copper plating to form a thin copper plating layer on the surface, until the thin copper plating layer is formed on the surface of the electroless nickel plating layer, the surface of the electroless nickel plating layer is hardly exposed to air. There is no touch, and almost no oxide film is formed on the surface. For this reason, the activation process which removes the oxide film becomes unnecessary. Moreover, since the said oxide film is hardly formed, the said thin copper plating layer adheres firmly with an electroless nickel plating layer, and does not peel practically. Further, the thin copper plating layer and the thick copper plating layer for circuit formation formed on the surface thereof are firmly bonded and practically do not peel off. Therefore, the adhesion reliability between the electroless nickel plating layer and the thin copper plating layer and the adhesion reliability between the thin copper plating layer and the thick copper plating layer for circuit formation are also high. In addition, since the thin copper plating layer has a thickness of 0.1 to 1.0 μm, moisture contained in the polyimide resin film easily evaporates in a drying process after the completion of the thin copper plating. Yes. Furthermore, since the electric conductivity is improved by forming the thin copper plating layer, it is easy to form a thick copper plating layer for forming a circuit later, and the time can be shortened.

  According to the method for producing a flexible printed board of the present invention, after electroless nickel plating is performed on the surface of the polyimide resin film, the surface of the electroless nickel plating layer is maintained in a state where the surface of the electroless nickel plating layer is kept wet. Since electrolytic copper plating for forming a thin copper plating layer on the surface is performed, an oxide film can be hardly formed on the surface of the electroless nickel plating layer. For this reason, the activation process which removes the oxide film can be made unnecessary, and the manufacturing process of a flexible printed circuit board can be simplified. Moreover, since the said oxide film is hardly formed, the said electroless nickel plating layer and a thin copper plating layer can be firmly adhere | attached so that it may not peel practically. Furthermore, the thin copper plating layer and the thick copper plating layer for circuit formation formed on the surface of the thin copper plating layer can be firmly bonded so that they are not practically peeled off. Therefore, the adhesion reliability between the electroless nickel plating layer and the thin copper plating layer and the adhesion reliability between the thin copper plating layer and the thick copper plating layer for circuit formation can be improved. Moreover, the water | moisture content contained in the polyimide resin film can be made easy to evaporate by making the thickness of the said copper plating layer thin in the range of 0.1-1.0 micrometer. And since the electroconductivity is improved by the formation of the thin copper plating layer, it is easy to form a thick copper plating layer for forming a circuit later, and the time can be shortened.

  In particular, when the electrolytic copper plating for forming the thin copper plating layer is performed using an electrolytic copper plating bath having a pH in the range of 7.0 to 10.0, a polyimide resin film, an electroless nickel plating layer, It is possible to further increase the peel strength after the heat load between.

  In addition, after forming the thin copper plating layer, prior to electrolytic copper plating for circuit formation, when heat treatment is performed within the range of 80 to 100 ° C., moisture contained in the polyimide resin film can be quickly removed. Can be evaporated. Furthermore, the heat treatment can further stabilize the interface between the polyimide resin film and the electroless nickel plating layer, and also stabilize the electroless nickel plating layer and the thin copper plating layer, thereby allowing adhesion between the two plating layers. Power can be strengthened.

  Moreover, according to the base material for circuits of this invention, the polyimide resin film, the nickel plating layer formed in the surface of this polyimide resin film, and the thickness 0.1-1. Since a 0 μm thin copper plating layer is provided, if a substrate for a circuit of the present invention is used in a method for producing a flexible printed circuit board, an activation process prior to thick electrolytic copper plating for circuit formation may be eliminated. It is possible to simplify the manufacturing process of the flexible printed circuit board. Furthermore, a thick copper plating layer for circuit formation can be firmly adhered to the surface of the thin copper plating layer.

  Next, the present invention will be described in detail with reference to the drawings.

  1-6 has shown one Embodiment of the manufacturing method of the flexible printed circuit board of this invention. The manufacturing method of this flexible printed circuit board includes the steps of applying electroless nickel plating to the surface of the polyimide resin film 1 and applying electrolytic copper plating for circuit formation to the surface of the electroless nickel plating layer 2. In FIG. 2, the formation of an oxide film on the surface of the electroless nickel plating layer 2 is prevented, thereby eliminating the need for an activation process for removing the oxide film, and improving the adhesion reliability of the thick copper plating layer 4 for circuit formation. It is a manufacturing method that enhances. Hereinafter, this production method will be described.

  First, the surface of the polyimide resin film 1 is surface-treated. This surface treatment is usually performed using an alkali metal hydroxide, and the alkali metal hydroxide is not particularly limited, and examples thereof include sodium hydroxide and potassium hydroxide. Further, prior to the surface treatment, the surface of the polyimide resin film 1 may be subjected to plasma treatment or short wavelength ultraviolet treatment. When plasma treatment or the like is performed in this manner, surface treatment with an alkali metal hydroxide is performed efficiently and uniformly, and the surface treatment can be light (low alkali concentration, low treatment temperature, short treatment time). Thereby, the influence with respect to the polyimide resin film 1 weak to an alkali can be decreased.

  Next, after applying a metal catalyst to the surface of the polyimide resin film 1, reduction treatment is performed using a reducing agent. The metal catalyst is not particularly limited, and commonly used palladium and platinum are exemplified. The reducing agent is not particularly limited, and examples thereof include sodium hypophosphite, sodium borohydride, dimethylamine borane and the like.

  Next, as shown in FIG. 1, the surface of the polyimide resin film 1 is subjected to electroless nickel plating. This electroless nickel plating is performed using, for example, an alkaline nickel solution, and the thickness of the formed electroless nickel plating layer 2 is usually set to be in the range of about 0.05 to 0.3 μm. When the thickness of the electroless nickel plating layer 2 is less than 0.05 μm, the decrease in adhesive strength after heat load increases, and when it is greater than 0.3 μm, the productivity decreases, and as described in detail later, Evaporation of moisture contained in the polyimide resin film 1 becomes difficult.

  When the electroless nickel plating is finished, the electroless nickel solution is taken out from the alkaline nickel solution and washed with water while the surface of the formed electroless nickel plating layer 2 is wet with the alkaline nickel solution. Then, when the washing with water is finished, the surface of the electroless nickel plating layer 2 is immersed in an electrolytic copper plating bath while being wet with water. Then, as shown in FIG. 2, electrolytic copper plating is performed to form a thin copper plating layer 3 having a thickness of 0.1 to 1.0 μm. When the thickness of the thin copper plating layer 3 is less than 0.1 μm, the electroless nickel plating layer 2 is not uniformly coated with copper, and when the thickness is more than 1.0 μm, the moisture contained in the polyimide resin film 1 is evaporated. It becomes difficult, and the adhesiveness of the polyimide resin film 1 and the electroless nickel plating layer 2 falls. Thus, after the electroless nickel plating layer 2 is formed, the surface of the electroless nickel plating layer 2 is formed with a thin copper plating layer 3 while maintaining its wetness. Is not formed.

  Although it does not specifically limit as said electrolytic copper plating bath, When forming thin copper plating layer 3 immediately after electroless nickel plating layer 2 is formed, it is between polyimide resin film 1 and electroless nickel plating layer 2. From the viewpoint of increasing the peel strength (heat resistant adhesive strength) after the thermal load, it is preferable that the electrolytic copper plating bath has a pH in the range of 7.0 to 10.0. Examples of the electrolytic copper plating bath having a pH in the range of 7.0 to 10.0 include a copper pyrophosphate bath, a copper cyanide bath, a copper sulfate EDTA complex bath, and the like. In acidic baths where the pH is lower than 7.0 (copper sulfate bath, copper borofluoride bath, etc.), the electroless nickel plating layer 2 is unstable immediately after deposition and is easily dissolved, and the pH exceeds 10.0. In a plating bath (such as an electroless copper plating bath) in the region, the polyimide from the polyimide resin film 1 in the vicinity of the interface of the electroless nickel plating layer 2 is easily dissolved, and in either case, a higher heat-resistant adhesive strength tends not to be obtained. Because there is.

  Next, it is taken out from the electrolytic copper plating bath and dried. The moisture contained in the polyimide resin film 1 is evaporated by this drying. The reason that this evaporation is possible is because the thickness of the electroless nickel plating layer 2 and the thin copper plating layer 3 on the surface of the polyimide resin film 1 is thin, and in each plating layer, a large number of fine holes are penetrated. The moisture contained in the polyimide resin film 1 is diffused to the outside through the micropores of the electroless nickel plating layer 2 and the micropores of the thin copper plating layer 3. Moreover, in order to complete the said evaporation in a short time, you may heat-process in the case of the said drying. This heat treatment is preferably performed within a range of 80 to 100 ° C. This is because if the temperature of the heat treatment is less than 80 ° C., the efficiency of the heat treatment tends to deteriorate, and if it exceeds 100 ° C., the oxidation of the thin copper plating layer 3 proceeds greatly. By this heat treatment at 80 to 100 ° C., an oxide film is formed on the surface of the thin copper plating layer 3, but the oxide film is not strong and is in an electrolytic copper plating bath for circuit formation in the next step. Easy to remove. Moreover, although the time of heat processing is not specifically limited, Usually, it is about 1-3 hours. The heat treatment can further stabilize the interface between the polyimide resin film 1 and the electroless nickel plating layer 2, and can further stabilize the electroless nickel plating layer 2 and the thin copper plating layer 3. The adhesive force between the plating layers can be further strengthened.

  In this way, a circuit substrate A composed of the polyimide resin film 1, the electroless nickel plating layer 2, and the thin copper plating layer 3 as shown in FIG.

  And this base material A for circuits is used, and a flexible printed circuit board is produced. For example, when a flexible printed circuit board is manufactured by a subtractive construction method, first, as shown in FIG. 3, a thick (thickness for circuit formation) is formed on the entire surface of the thin copper plating layer 3 of the circuit substrate A. Electrolytic copper plating is applied. Next, as shown in FIG. 4, after patterning the circuit using the resist 5 on the surface of the thick copper plating layer 4, as shown in FIG. The plating layer 4, the thin copper plating layer 3 and the electroless nickel plating layer 2 are removed by etching. Then, as shown in FIG. 6, the resist 5 is removed to reveal a circuit. In this way, a flexible printed circuit board can be produced using the circuit substrate A.

  As another method, in the case of the semi-additive method, first, as shown in FIG. 7, after patterning the circuit using the resist 5 on the surface of the thin copper plating layer 3 of the circuit substrate A, As shown in FIG. 8, thick electrolytic copper plating for circuit formation is applied to a portion not covered with the resist 5 to form a thick copper plating layer 4. Next, as shown in FIG. 9, after removing the resist 5, as shown in FIG. 10, the thin copper plating layer 3 and the electroless nickel plating layer 2 covered with the resist 5 are removed by soft etching. , Reveal the circuit. Even if it does in this way, a flexible printed circuit board can be produced using the above-mentioned substrate A for circuits.

  According to such a method for producing a flexible printed circuit board, an oxide film is not formed on the surface of the electroless nickel plating layer 2 when the substrate A for circuit is produced, so that an activation process for removing the oxide film is unnecessary. become. For this reason, the continuity with an electroless nickel plating process and a copper plating process becomes easy. As a result, productivity can be improved and production cost can be reduced. Furthermore, the thin copper plating layer 3 on the surface of the electroless nickel plating layer 2 does not form a strong oxide film on the surface even when dried, and is thin (0.1 to 1.0 μm). In the drying, moisture contained in the polyimide resin film 1 is easily evaporated.

  And when performing electrolytic copper plating for circuit formation, since the thin copper plating layer 3 is formed on the surface of the electroless nickel plating layer 2, the electroconductivity is good, and thick copper for circuit formation is formed on the surface. It is easy to form the plating layer 4. Moreover, since nickel has a large electric resistance, the current density cannot be increased only by the electroless nickel plating layer 2 and the productivity is not high. However, when the thin copper plating layer 3 is formed on the surface, the copper is Since the electric resistance is low, the current density can be increased and the thick copper plating layer 4 can be formed in a short time. For this reason, productivity can be improved and production cost can be reduced. In addition, the electroless nickel plating layer 2 and the thin copper plating layer 3 are firmly bonded, and when the thick copper plating layer 4 is formed, the oxide film on the surface of the thin copper plating layer 3 is the electrolytic copper. It is removed in the plating bath. Therefore, even after the thick copper plating layer 4 is formed, peeling between the electroless nickel plating layer 2 and the thin copper plating layer 3 and peeling between the thin copper plating layer 3 and the thick copper plating layer 4 occur. Thus, a stable circuit can be formed.

  Next, examples will be described together with comparative examples.

[Example 1]
As shown below, a circuit board was prepared, and a thick electrolytic copper plating for circuit formation was applied to the circuit board to obtain a copper plated substrate.

〔surface treatment〕
First, a 20 cm × 20 cm polyimide resin film (manufactured by Toray DuPont, Kapton 100EN) was surface-treated at 25 ° C. for 5 minutes using a 200 g / liter sodium hydroxide aqueous solution.

[Catalyst application and reduction treatment]
Subsequently, the catalyst was applied by treating with an OPC-50 inducer (Okuno Pharmaceutical Co., Ltd.) for 5 minutes at 40 ° C., and then at 25 ° C. with an OPC-150 crystalr (Okuno Pharmaceutical Co., Ltd.). Reduction treatment was performed by treating for 5 minutes.

[Electroless nickel plating and thin copper plating]
Subsequently, electroless nickel plating was performed at 40 ° C. for 5 minutes with an alkaline nickel solution (TMP-chemical nickel, manufactured by Okuno Pharmaceutical Co., Ltd.) to form an electroless nickel plating layer having a thickness of 0.2 μm. Subsequently, the surface of the electroless nickel plating layer was washed with water while the surface was wet with an alkaline nickel solution, and then the copper pyrophosphate bath having a pH of 8.8 (the composition was pyrroline) while the surface was wet with water. Acid copper: 94 g / liter, potassium pyrophosphate: 340 g / liter, 28% aqueous ammonia: 3 ml / liter). Then, electrolytic copper plating (55 ° C. × 2 minutes) was performed at a current density of 1 A / dm ² to form a thin copper plating layer having a thickness of 0.2 μm.

〔Heat treatment〕
Subsequently, heat treatment was performed in a drying oven at 100 ° C. for 2 hours. In this way, a circuit substrate was produced.

[Thick electrolytic copper plating for circuit formation]
Subsequently, electrolytic copper plating was performed for 50 minutes at a current density of 2 A / dm ² in a copper sulfate plating bath on the surface of the thin copper plating layer without performing activation treatment on the circuit substrate. A thick copper plating layer for circuit formation of 20 μm was formed.

[Example 2]
After forming a thin copper plating layer in the same manner as in Example 1, the film was left at room temperature (25 ° C.) for 1 day without performing heat treatment. Thereafter, a thick copper plating layer for circuit formation was formed in a copper sulfate plating bath in the same manner as in Example 1. Other than that, it was the same as in Example 1 above.

Example 3
In the formation of the thin copper plating layer of Example 1 above, instead of the copper pyrophosphate bath, electrolytic copper plating (25 ° C. × 2 minutes) was performed at a current density of 1 A / dm ² using a copper sulfate plating bath having a pH of 1.0. went. Then, a thin copper plating layer having a thickness of 0.2 μm was formed. Other than that, it was the same as in Example 1 above.

Example 4
In the formation of the thin copper plating layer in Example 1, the copper pyrophosphate bath was adjusted to pH 6.0, and electrolytic copper plating (55 ° C. × 2 minutes) was performed at a current density of 1 A / dm ² . Then, a thin copper plating layer having a thickness of 0.2 μm was formed. Other than that, it was the same as in Example 1 above.

Example 5
In the formation of the thin copper plating layer in Example 1, the copper pyrophosphate bath was adjusted to pH 7.0, and electrolytic copper plating (55 ° C. × 2 minutes) was performed at a current density of 1 A / dm ² . Then, a thin copper plating layer having a thickness of 0.2 μm was formed. Other than that, it was the same as in Example 1 above.

Example 6
In the formation of the thin copper plating layer in Example 1, the copper pyrophosphate bath was adjusted to pH 10.0, and electrolytic copper plating (55 ° C. × 2 minutes) was performed at a current density of 1 A / dm ² . Then, a thin copper plating layer having a thickness of 0.2 μm was formed. Other than that, it was the same as in Example 1 above.

Example 7
In the formation of the thin copper plating layer of Example 1 above, instead of electrolytic copper plating using a copper pyrophosphate bath, a formaldehyde bath (electroless copper plating bath) having a pH of 12.5 was used, and electroless copper plating (40 ° C. X 6 minutes). And the thin copper plating layer of thickness 0.1 micrometer was formed. Other than that, it was the same as in Example 1 above.

[Comparative Example 1]
A heat treatment is performed after the electroless nickel plating in Example 1 above, and then a thin copper plating layer is formed in the same copper pyrophosphate bath as in Example 1 without performing an activation treatment. In the same manner as in Example 1, a thick copper plating layer for circuit formation was formed in a copper sulfate plating bath. Other than that, it was the same as in Example 1 above.

[Comparative Example 2]
A heat treatment is performed after the electroless nickel plating of Example 1, and thereafter, the circuit is formed in a copper sulfate plating bath in the same manner as in Example 1 without performing the activation process and forming a thin copper plating layer. A thick copper plating layer was formed. Other than that, it was the same as in Example 1 above.

[Comparative Example 3]
After the electroless nickel plating of Example 1 above, heat treatment is performed, and then activation treatment is performed with 10% hydrochloric acid at 25 ° C. for 1 minute, and then a thick copper plating layer for circuit formation is formed in a copper sulfate plating bath. Formed. Other than that, it was the same as in Example 1 above.

  For each of the copper plated substrates of Examples 1 to 7 and Comparative Examples 1 to 3 thus obtained, cut into a 1 cm wide strip, 180 ° was used using a tensile tester (Orientec Co., Ltd.). Peel strength measurement was performed at the initial stage and after heat load. Here, the initial state is a state before the heat load is applied, and the after heat load is a state after the heat load (150 ° C. × 3 days) is applied. These results are shown in Table 1 below.

  From the result of the said Table 1, in the copper plating board | substrate of Examples 1-7, compared with Comparative Examples 1-3, peeling has generate | occur | produced 100% between a polyimide resin film and an electroless nickel plating layer. It can be seen that the adhesion reliability is high. Moreover, also about the peeling, in the copper plating board | substrate of Examples 1-7, even if it does not perform an activation process, it can obtain the peeling strength equivalent to or higher than the comparative example 3 which performed the activation process. Understand. Here, in Comparative Example 3, since peeling occurs between the electroless nickel plating layer and the copper plating layer, the oxide film on the surface of the electroless nickel plating layer is sufficiently obtained even when the activation treatment is performed. It can be seen that it has not been removed. Moreover, when Example 1 and Example 2 are compared, since the peel strength is higher in Example 1 in which heat treatment is performed after forming a thin copper plating layer, the heat treatment further strengthens the adhesive strength. I understand. Further, when Examples 1, 2, 5, 6 and Examples 3, 4, 7 are compared, the pH of the electrolytic copper plating bath for forming a thin copper plating layer is in the range of 7.0 to 10.0. If it exists, it turns out that the peeling strength after a heat load can be enlarged more. Moreover, in Comparative Examples 1 and 2, since the peeling surface is between the electroless nickel plating layer and the copper plating layer, an oxide film is formed on the surface of the electroless nickel plating layer, and it is not removed I understand.

It is explanatory drawing which shows the manufacturing method of the base material for circuits in one Embodiment of the manufacturing method of the flexible printed circuit board of this invention. It is explanatory drawing which shows the manufacturing method of the said base material for circuits. It is explanatory drawing which shows the manufacturing method of the flexible printed circuit board by the subtractive construction method using the said base material for circuits. It is explanatory drawing which shows the said subtractive construction method. It is explanatory drawing which shows the said subtractive construction method. It is explanatory drawing which shows the said subtractive construction method. It is explanatory drawing which shows the manufacturing method of the flexible printed circuit board by the semi-additive construction method using the said base material for circuits. It is explanatory drawing which shows the said semi-additive construction method. It is explanatory drawing which shows the said semi-additive construction method. It is explanatory drawing which shows the said semi-additive construction method. It is explanatory drawing which shows the manufacturing method of the conventional flexible printed circuit board.

Explanation of symbols

A Circuit substrate 1 Polyimide resin film 2 Electroless nickel plating layer 3 Thin copper plating layer 4 Thick copper plating layer

Claims (4)

  In a method for producing a flexible printed circuit board comprising the steps of applying electroless nickel plating to the surface of a polyimide resin film and applying electrolytic copper plating for circuit formation to the surface of the electroless nickel plating layer, After the electrolytic nickel plating is performed, the surface of the electroless nickel plating layer is kept wet, and the surface of the electroless nickel plating layer is subjected to electrolytic copper plating so that the thickness is 0.1 to 1.0 μm. A method for producing a flexible printed circuit board, comprising: forming a copper plating layer, and then performing electrolytic copper plating for circuit formation on the surface of the thin copper plating layer.   The method for producing a flexible printed board according to claim 1, wherein the electrolytic copper plating for forming the thin copper plating layer is performed using an electrolytic copper plating bath having a pH in the range of 7.0 to 10.0.   The method for producing a flexible printed circuit board according to claim 1 or 2, wherein after the thin copper plating layer is formed, heat treatment is performed within a range of 80 to 100 ° C prior to electrolytic copper plating for circuit formation.   It is the base material for circuits used for the manufacturing method of the flexible printed circuit board as described in any one of Claims 1-3, Comprising: A nickel plating layer formed in the surface of this polyimide resin film, and this, A circuit base material comprising: a thin copper plating layer having a thickness of 0.1 to 1.0 μm formed on a surface of a nickel plating layer.

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