JP5870550B2 - Manufacturing method of flexible printed circuit board - Google Patents

Description

  The present invention relates to a method for producing a flexible printed circuit board.

  A method of manufacturing a flexible printed circuit board in which a nickel plating layer is formed on the surface of a polyimide film and then a copper layer for forming a wiring pattern is formed by copper plating has been studied.

  For example, in Patent Document 1, the surface of a polyimide film is hydrophilized, a catalyst is provided, electroless plating is performed, heat treatment is performed in an inert atmosphere, and then electroless copper plating or electroless copper plating is followed by electrolytic copper. When producing a copper polyimide substrate by performing plating, the hydrophilic treatment of the polyimide film surface is performed using an aqueous solution containing any one of permanganate or hypochlorite, and after application of the catalyst, An electroless plating film made of any one of nickel, cobalt, or an alloy of these metals is formed on the surface so as to have a thickness of 0.01 to 0.1 μm and an impurity content in the film of 10% by weight or less. And the obtained substrate has a maximum temperature of 350 to 540 ° C. and a thermal load coefficient D of 0.3 to 3.5. Method for producing a copper polyimide substrate has been disclosed as will be characterized by a heat treatment in an inert atmosphere.

  In patent document 2, in the manufacturing method of the flexible printed circuit board provided with the process of forming a nickel plating layer on both surfaces of a polyimide film, and forming the copper plating layer for wiring pattern formation on the surface of each nickel plating layer, the said nickel plating layer The formation of is divided into two steps, and in the first step, after forming a first nickel plating layer that is thin by electroless nickel plating, specifically having a thickness of 0.01 to 0.1 μm, this is dried, Next, in the second step, the second nickel plating layer is formed on the surface of the thin first nickel plating layer by electroless nickel plating or electrolytic nickel plating, preferably the thickness of the first nickel plating layer and the second Disclosed is a method for manufacturing a flexible printed circuit board, characterized in that the total thickness of nickel plating layers is 0.2 to 1.0 μm. ing.

  The nickel plating layer formed between the polyimide film and the copper plating layer is the copper polyimide film side that causes a decrease in the adhesive strength of the circuit (copper plating layer) during a long-term thermal load in actual use of the flexible printed circuit board. This prevents diffusion migration to However, this nickel plating layer is formed by electroless plating (wet plating), and the polyimide film absorbs moisture during formation. In a flexible printed circuit board where moisture exists in the polyimide film, the moisture in the polyimide film expands during high-temperature and short-time heat loads such as solder bonding, causing a decrease in the adhesion between the polyimide film and the nickel plating layer. Usually, after the nickel plating layer is formed and before the copper plating layer is formed, heat treatment is performed to evaporate water contained in the polyimide film. The nickel plating layer needs to have a certain thickness in order to exhibit barrier properties against copper diffusion and migration under a long-term heat load. However, if the nickel plating layer is formed on both sides of the polyimide film, moisture is required. When the high-temperature and short-time heat load is applied to the manufactured flexible printed circuit board, the moisture in the polyimide resin film expands and the adhesive force between the polyimide film and the nickel plating layer may decrease. . In the method described in Patent Document 2, as described above, the formation of the nickel plating layers on both the front and back surfaces is divided into two steps. First, after forming a thin first nickel plating layer on both surfaces of the polyimide film, the polyimide film is dried to form the inside of the polyimide film. By evaporating the moisture, and then forming a second nickel plating layer to thicken the nickel plating layer to a thickness that exhibits barrier properties, thereby reducing the adhesive strength due to diffusion migration of copper during a long-term thermal load. In addition, both the adhesive strength reduction due to the rapid expansion of moisture in the polyimide film at the time of high-temperature and short-time heat load such as solder bonding is prevented.

Japanese Patent Laid-Open No. 5-129377 JP 2005-154895 A

  The object of the present invention is to heat the copper polyimide film at the time of long-term heat load without heating at a high temperature after the formation of the electroless nickel plating layer, and further without forming the electroless nickel plating layer in a plurality of steps. To provide a method for producing a flexible printed circuit board that suppresses a decrease in adhesion strength due to diffusion to the surface, is excellent in heat resistance against long-term heat load, and is also excellent in heat resistance against high-temperature and short-time heat load and solder heat resistance. It is.

The present invention relates to the following matters.
(1) Using a double-sided nickel-plated laminated polyimide film, one side (A) of the polyimide film has wiring and the other side (B) is a part where the polyimide film is exposed partly or entirely by wiring processing. In a method of manufacturing a flexible printed circuit board having:
The double-sided nickel plating laminated polyimide film to be used is a heated laminated film after forming an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm on both sides of the polyimide film by one plating. A method for producing a flexible printed circuit board characterized by
(2) The double-sided nickel plating laminated polyimide film is a laminated film heated in a range of 80 to 150 ° C. after forming an electroless nickel plating layer on both sides of the polyimide film by one plating. The manufacturing method of the flexible printed circuit board as described in (1).
(3) The above (1) or (2) is characterized in that the surface treatment of the polyimide film with an alkali metal hydroxide or an aqueous solution thereof is performed before forming the electroless nickel plating layer on both sides of the polyimide film. The manufacturing method of the flexible printed circuit board of description.
(4) The flexible printed circuit board according to any one of the above (1) to (3), further comprising a step of heating the flexible printed circuit board obtained by wiring processing in a range of 80 to 250 ° C. The manufacturing method.

(5) In a method for producing a flexible printed board having wiring on at least one surface of a polyimide film by wiring processing using a double-sided nickel plating laminated polyimide film,
The double-sided nickel plating laminated polyimide film to be used is in the range of 100 to 180 ° C. after forming an electroless nickel plating layer by one plating on both sides of the polyimide film heat-treated at a maximum heating temperature of 530 ° C. or more during imidization. A method for producing a flexible printed board, which is a laminated film heated for 2.5 hours or more.
(6) In a method of manufacturing a flexible printed board having wiring on at least one surface of a polyimide film by wiring processing using a double-sided nickel plating laminated polyimide film,
The double-sided nickel plating laminated polyimide film to be used is heated at a temperature of 100 to 180 ° C. for 2.5 hours or more after forming an electroless nickel plating layer by one plating on both sides of the polyimide film heat-treated at 490 ° C. or more. A method for producing a flexible printed circuit board characterized by being a laminated film.
(7) The flexible printed circuit board according to (5) or (6) above, wherein the thickness of the electroless nickel plating layer formed on both sides of the polyimide film is more than 0.1 μm and less than 0.3 μm The manufacturing method.
(8) The surface treatment of the polyimide film with an alkali metal hydroxide or an aqueous solution thereof is performed before forming the electroless nickel plating layer on both sides of the polyimide film. The manufacturing method of the flexible printed circuit board of any one of Claims 1.
(9) The above-mentioned flexible printed circuit board, wherein one surface (A) of the polyimide film has wiring and the other surface (B) has a metal plating layer on the entire surface ( The manufacturing method of the flexible printed circuit board of any one of 5)-(8).

(10) The process for producing a flexible printed board according to any one of (1) to (9), wherein the wiring process is a wiring process by a semi-additive method or a subtractive method.
(11) The wiring processing is wiring processing by a semi-additive method, and includes a step of forming a plating resist layer by any one of the following methods (i) to (iii). Manufacturing method for flexible printed circuit boards.
(I) A method of forming a plating resist layer after sequentially forming an electroless copper plating layer and an electrolytic copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Ii) A method of forming a plating resist layer after forming an electroless copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Iii) A method of directly forming a plating resist layer on the electroless nickel plating layer of the double-sided nickel plating laminated polyimide film.

(12) One side (A) of the polyimide film has a wiring, and the other side (B) is a flexible printed circuit board having a portion where the polyimide film is exposed partly or entirely,
Manufactured by wiring processing using a heated double-sided nickel-plated laminated polyimide film after forming an electroless nickel-plated layer with a thickness of more than 0.1 μm and less than 0.3 μm on both sides of the polyimide film in a single plating A flexible printed circuit board characterized by being made.
(13) A flexible printed board having wiring on at least one surface of the polyimide film,
Double-sided nickel that was heated for 2.5 hours or more in the range of 100 to 180 ° C after forming an electroless nickel plating layer on both sides of the polyimide film heat-treated at a maximum heating temperature of 530 ° C or higher during imidization. A flexible printed circuit board produced by wiring processing using a plated laminated polyimide film.
(14) A flexible printed circuit board having wiring on at least one surface of a polyimide film,
After forming an electroless nickel plating layer on both sides of a polyimide film heat-treated at 490 ° C. or more by one plating, a double-sided nickel plating laminated polyimide film heated at 100 to 180 ° C. for 2.5 hours or more is used. A flexible printed circuit board manufactured by wiring processing.

  In the manufacturing method of the 1st flexible printed circuit board of this invention, after forming the electroless nickel plating layer each thickness exceeding 0.1 micrometer and less than 0.3 micrometer on both surfaces of a polyimide film by one plating, it heated both surfaces Using a nickel-plated laminated polyimide film, by flexible wiring, one surface (A) of the polyimide film has wiring, and the other surface (B) has a portion where the polyimide film is exposed partially or entirely. A substrate is manufactured.

  In this production method, the heat treatment after the formation of the electroless nickel plating layer and before the formation of the copper plating layer is performed in order to ensure adhesion between the electroless nickel plating layer and the polyimide film that can withstand wiring processing. Then, after forming the copper plating layer, one side (A) of the polyimide film has wiring, and the other side (B) forms wiring so that the polyimide film is partially or entirely exposed. Thus, a moisture escape path is ensured so that the moisture in the polyimide film can be sufficiently removed, and then heat treatment is further performed to remove the moisture in the polyimide film. Thereby, the water | moisture content in a polyimide film can fully be reduced, and the fall of the adhesive strength at the time of high temperature heat load like solder joining can be suppressed. On the other hand, since the electroless nickel plating layer having a thickness exceeding 0.1 μm can prevent diffusion and migration of copper to the polyimide film side during a long-term heat load, it also suppresses a decrease in adhesion strength during a long-term heat load. be able to. That is, it is possible to ensure adhesion between the electroless nickel plating layer and the polyimide film that can withstand both a long-term heat load and a high-temperature heat load. In addition, when the thickness of the electroless nickel plating layer is 0.3 μm or more, the adhesion between the electroless nickel plating layer and the polyimide film is reduced by the heat treatment after the formation of the electroless nickel plating layer and before the formation of the copper plating layer. There is.

  As described above, according to the present invention, after forming the electroless nickel plating layer on both sides of the polyimide film, without heating at a high temperature, and further without forming the electroless nickel plating layer in a plurality of steps, it can be performed for a long time. Suppresses the decrease in adhesion strength due to the diffusion of copper to the polyimide film side during heat load, and has excellent heat resistance against long-term heat load, and also excellent heat resistance against high temperature and short time heat load and solder heat resistance One surface can form a wiring pattern, and the other surface can obtain a flexible printed board having a polyimide film exposed partly or entirely.

  In the second method for producing a flexible printed board of the present invention, a polyimide film obtained by heat treatment at a maximum heating temperature of 530 ° C. or higher during imidization, or imidization (even if the maximum heating temperature is 530 ° C. or higher, 530 The polyimide film obtained by (1) may be less than 490 ° C., preferably on the both sides of the polyimide film heat-treated for 1 minute or more, and the thickness is preferably more than 0.1 μm by one plating. After forming an electroless nickel plating layer of less than 0.3 μm, using a double-sided nickel-plated laminated polyimide film heated for 2.5 hours or more in the range of 100 to 180 ° C., by wiring processing, at least one surface of the polyimide film A flexible printed circuit board having wiring is manufactured. When heat-treating the polyimide film at 490 ° C. or higher, the heating time is, for example, 1 to 5 minutes.

  In this production method, a polyimide film obtained by heat treatment at a maximum heating temperature of 530 ° C. or higher higher than that at the time of imidization, or a polyimide film obtained by imidation regardless of the maximum heating temperature at the time of imidation is 490. Use a polyimide film that has been heat-treated at a temperature of not lower than 1 ° C., preferably for 1 minute or longer, and after the electroless nickel plating layer is formed, heat treatment before the formation of the copper plating layer is relatively long, specifically, a temperature range of 100 to 180 ° C. In this way, although the electroless nickel plating layer is formed on both sides of the polyimide film, the moisture in the polyimide film can be sufficiently removed and reduced, such as solder bonding. It is possible to suppress a decrease in adhesion strength during high temperature heat load. When using a polyimide film with a maximum heating temperature of less than 530 ° C. and not heat-treated at 490 ° C. or higher after imidation, the moisture in the polyimide film cannot be reduced sufficiently, A decrease in adhesion strength may not be sufficiently suppressed. On the other hand, in particular, the electroless nickel plating layer with a thickness exceeding 0.1 μm can sufficiently prevent diffusion migration of copper to the polyimide film side during a long-term heat load. The decrease can be suppressed. That is, it is possible to ensure adhesion between the electroless nickel plating layer and the polyimide film that can withstand both a long-term heat load and a high-temperature heat load. In addition, when the thickness of the electroless nickel plating layer is 0.3 μm or more, the adhesion between the electroless nickel plating layer and the polyimide film is reduced by the heat treatment after the formation of the electroless nickel plating layer and before the formation of the copper plating layer. There is.

  In this second flexible printed board manufacturing method, unlike the first flexible printed board manufacturing method described above, the moisture in the polyimide film is sufficiently removed by heat treatment after forming the electroless nickel plating layer and before forming the copper plating layer. Can be reduced. Therefore, it is necessary to secure the passage of moisture by forming the wiring so that one surface (A) of the polyimide film has wiring and the other surface (B) has at least a portion where the polyimide film is exposed. There is no. According to this second flexible printed circuit board manufacturing method, a flexible printed circuit board having a wiring on one surface and a metal layer on the other surface, that is, a portion having no exposed polyimide film can be manufactured. .

  As described above, according to the present invention, after forming the electroless nickel plating layer on both sides of the polyimide film, without heating at a high temperature, and further without forming the electroless nickel plating layer in a plurality of steps, it can be performed for a long time. Suppresses the decrease in adhesion strength due to the diffusion of copper to the polyimide film side during heat load, and has excellent heat resistance against long-term heat load, and also excellent heat resistance against high temperature and short time heat load and solder heat resistance A flexible printed board having a wiring pattern on at least one surface can be obtained.

<< Production Method of First Flexible Printed Circuit Board of the Present Invention >>
In the manufacturing method of the 1st flexible printed circuit board of this invention, as above-mentioned, each electroless nickel plating with each thickness exceeding 0.1 micrometer and less than 0.3 micrometer on both surfaces of a polyimide film by electroless nickel plating once. After forming the layer, a heated double-sided nickel-plated laminated polyimide film is used.

  As a polyimide film, the commercially available polyimide film etc. which can be used suitably for various boards, such as a wiring board, can be used.

As a polyimide film, it is preferable that a linear expansion coefficient (50-200 degreeC) is near the linear expansion coefficient of copper laminated | stacked on a polyimide film, and the linear expansion coefficient (50-200 degreeC) of a polyimide film is 0.5 * 10 < ^- >. It is preferably ^{5 to} 2.8 × 10 ⁻⁵ cm / cm / ° C.

  In addition, a polyimide film having a thermal shrinkage rate of 0.05% or less is preferable because of its small thermal deformation.

  As the polyimide film, a polyimide film excellent in heat resistance, electrical insulation and the like can be suitably used.

  The thickness of the polyimide film is not particularly limited as long as the thickness can sufficiently support the metal layer and wiring pattern layer to be formed and can be handled without problems, and preferably 1 to 500 μm, more preferably 2 to 300 μm. More preferably, it is 5 to 200 μm, more preferably 5 to 175 μm, and particularly preferably 5 to 100 μm.

  As the polyimide film, a single layer, a multilayer film in which two or more layers are laminated, or a sheet-like one can be used.

The polyimide film can be produced by a known method. For example, a single-layer polyimide film is
(1) A method in which a polyamic acid solution, which is a polyimide precursor, is cast or applied to a support and imidized;
(2) A method in which a polyimide solution is cast or applied to a support and heated as necessary.
Etc.
Two or more layers of polyimide film
(3) A polyamic acid solution, which is a polyimide precursor, is cast or coated on a support, and a polyamic acid solution, which is a polyimide precursor of the second layer or more, is sequentially cast or coated on the support before. A method of casting or coating on the upper surface of the polyamic acid layer and imidizing;
(4) A method in which a polyamic acid solution, which is a precursor of two or more layers of polyimide, is simultaneously cast or applied to a support and imidized;
(5) The polyimide solution is cast or coated on the support, and the polyimide solution of the second layer or more is sequentially cast or coated on the upper surface of the polyimide layer previously cast or coated on the support. Heating method,
(6) A method in which two or more layers of polyimide solution are simultaneously cast or coated on a support and heated as necessary.
(7) It can be obtained by a method of laminating two or more polyimide films obtained in (1) to (6) directly or via an adhesive.

  As a polyimide film, for example, tetra-containing a main component containing a component selected from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), and the like. Mainly a carboxylic acid component and a component selected from paraphenylenediamine (PPD), 4,4′-diaminodiphenyl ether (4,4′-DADE), 3,4′-diaminodiphenyl ether (3,4′-DADE), etc. A polyimide synthesized from a diamine component contained as a component can be used.

  Suitable polyimide films include, for example, the following polyimides (1) to (4).

  (1) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and paraphenylenediamine (PPD) and optionally 4,4′-diaminodiphenyl ether (4,4′-DADE) ) And polyimide produced from. In this case, the PPD / 4,4'-DADE (molar ratio) is preferably 100/0 to 85/15.

  (2) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4′-diaminodiphenyl ether Polyimide produced from (4,4'-DADE). In this case, s-BPDA / PMDA is preferably 15/85 to 85/15, and PPD / 4, 4'-DADE is preferably 90/10 to 10/90.

  (3) A polyimide produced from pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4'-diaminodiphenyl ether (4,4'-DADE). In this case, the 4,4′-DADE / PPD is preferably 90/10 to 10/90.

  (4) 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4′-diaminodiphenyl ether (4 , 4'-DADE). In this case, it is preferable that BTDA / PMDA is 20/80 to 90/10, and PPD / 4, 4'-DADE is 30/70 to 90/10.

  In the synthesis | combination of a polyimide, you may use the other tetracarboxylic dianhydride and diamine which are the kind and quantity which do not impair the physical property of a polyimide.

  As the polyimide film, a polyimide film obtained by modifying the film surface with an inorganic oxide can be used. A polyimide film having a film surface modified with an inorganic oxide may have higher adhesion strength and heat resistance.

  The polyimide film modified with an inorganic oxide was manufactured by casting a solution of a polyimide precursor (polyamic acid or the like) obtained from an aromatic tetracarboxylic acid component and an aromatic diamine component on a support and heating. It is a film in which a solution containing an appropriate inorganic compound (for example, a metal compound) is applied to one or both sides of a self-supporting film of a polyimide precursor solution to modify the inorganic oxide. Inorganic oxide modification refers to a state modified with a metal oxide or an oxide of a semiconductor element that becomes a solid oxide similar to a metal oxide (hereinafter simply referred to as a metal oxide), and at least a part of the surface. Is a state where an inorganic substance (metal element or semiconductor element) -oxygen bond is formed.

  The polyimide film is preferably modified with aluminum oxide, titanium oxide or silicon oxide, and an aluminum-oxygen bond, a titanium-oxygen bond or a silicon (silicon) -oxygen bond is formed on at least a part of the surface. It is preferable.

  Inorganic oxide-modified state is not a complete oxide, for example, aluminum hydroxide, titanium hydroxyl group, silicon hydroxyl group, or dangling bonds are partly present, Bonds may be present.

  As the polyimide film, a polyimide film having at least one surface treated by corona discharge treatment, plasma treatment, chemical roughening treatment, physical roughening treatment or the like can also be used.

  The double-sided nickel-plated laminated polyimide film used in the first method for producing a flexible printed circuit board of the present invention has an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm on both sides of the polyimide film by one plating. It can be obtained by forming and then heating preferably in the range of 80-150 ° C.

  If the thickness of the electroless nickel plating layer of the double-sided nickel-plated laminated polyimide film is less than the above range, the decrease in adhesion strength due to copper diffusion during long-term heat load cannot be sufficiently suppressed, and adhesion due to long-term heat load May deteriorate. If it is thicker than the above range, the polyimide film covered on both sides with the electroless nickel plating layer will block the passage of moisture as much as possible. Adhesiveness with a polyimide film may deteriorate. Furthermore, when the electroless nickel plating layer is thick, it is difficult to remove the base including the electroless nickel plating layer in forming the wiring pattern, which may cause an undercut in the wiring by strengthening the removal process.

  The thickness of the electroless nickel plating layer is preferably more than 0.1 μm and less than 0.3 μm, more preferably from 0.11 μm to 0.28 μm, and from 0.12 μm to 0.27 μm. More preferred.

  In the manufacturing method of the 1st flexible printed circuit board of this invention, after forming an electroless nickel plating layer on both surfaces of a polyimide film, the obtained double-sided nickel plating laminated polyimide film is heated.

  The heating temperature of the double-sided nickel-plated laminated polyimide film is in the range of 80 to 180 ° C, preferably in the range of 80 to 150 ° C, more preferably in the range of 90 to 140 ° C, and still more preferably in the range of 100 to 130 ° C. preferable. When the heating temperature is lower than the above range, the heating time may become long and productivity may be a problem. When the heating temperature is higher than the above range, the moisture in the polyimide film vaporizes and expands at once, and the electroless nickel plating layer and the polyimide Adhesion with the film may be reduced.

  What is necessary is just to set time for heating time suitably, for example, Preferably it is 1 minute-24 hours, More preferably, it is 10 minutes-3 hours, More preferably, it is between 20 minutes-2 hours.

  When the electroless nickel plating layer is formed on both surfaces of the polyimide film, as a pretreatment, both surfaces of the polyimide film are surface-treated using an alkali metal hydroxide or an aqueous solution thereof. This is preferable in order to ensure adhesion at the polyimide film interface. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.

  As an example of a method for producing a double-sided nickel-plated laminated polyimide film from a polyimide film, at least the steps of applying a catalyst, the step of forming a nickel plating layer by electroless nickel plating, and the step of heating are performed in this order on both sides of the polyimide film. Furthermore, at least a step of treating with an alkaline solution, a step of applying a catalyst, a step of forming a nickel plating layer by electroless nickel plating, and a step of heating can be performed in this order. Also, in the step of treating with an alkaline solution, a basic amino acid is mixed with the alkaline solution, or after the step of treating with an alkaline solution, a step of treating with a basic amino acid solution is added, or a basic amino acid solution is added to the catalyst. Things can be used. By using a basic amino acid, a large amount of metal catalyst can be selectively adsorbed on the surface of the polyimide film, and in particular, the adhesion can be stabilized.

Each of the above steps for producing a double-sided nickel-plated laminated polyimide film from a polyimide film will be described in detail below.
1) In the step of treating with an alkaline solution, the surface of the polyimide film is treated by spraying or dipping the surface of the polyimide film into an alkaline solution, for example, an alkaline solution containing potassium hydroxide or sodium hydroxide. To do. For example, it can carry out by the method of immersion treatment at 25-80 degreeC for 10 second-10 minutes with potassium hydroxide or sodium hydroxide 10-200 g / L aqueous solution.
2) In the step of applying a catalyst, in order to form nuclei for electroless base metal precipitation on the surface of the polyimide film, the catalyst is applied to a part or all of the modified surface of the polyimide film by a method such as adsorption. For example, by immersing in an ionic palladium catalyst solution at 30 to 60 ° C. for 1 to 10 minutes to adsorb palladium ions on the surface of the polyimide film, and then immersing in a reducing solution to reduce the palladium ions to metallic palladium. It can be carried out.
3) In the step of forming the nickel plating layer, nickel is deposited by an electroless plating method to form an electroless base nickel layer. For example, it can be performed by immersing in a commercially available electroless nickel plating bath at 25 to 45 ° C. for 2 to 20 minutes.
4) In the heating step, the polyimide film having the electroless nickel plating layer formed on both sides is heated. Preferably, it can be performed by heating at 80 ° C. to 150 ° C. for 1 minute to 24 hours.

  As another example of a method for producing a double-sided nickel-plated laminated polyimide film from a polyimide film, a step of washing both surfaces of the polyimide film with an acid or an alkaline degreasing solution containing at least a surfactant, a step of treating with an alkaline solution, The step of treating with a basic amino acid solution, the step of applying a catalyst, the step of forming a nickel plating layer by electroless nickel plating, and the step of heating can be performed in this order.

Each of the above steps for producing a double-sided nickel-plated laminated polyimide film from a polyimide film will be described in detail below.
1) In the step of washing with an acid or alkaline degreasing solution containing a surfactant, the surface of the polyimide film is treated with a degreasing solution having a cleaning effect in order to remove oil components on the surface of the polyimide film. For example, dip oil and fat components by soaking in an alkaline solution containing a surfactant such as polyoxyethylene alkyl ether or dipropylene glycol monomethyl ether and sodium hydroxide or monoethanolamine at 30 to 60 ° C. for 1 to 10 minutes. Remove and wash the polyimide film.
2) In the step of treating with an alkaline solution, the surface of the polyimide film is treated by spraying or dipping the surface of the polyimide film into an alkaline solution such as an alkaline solution containing potassium hydroxide, sodium hydroxide or the like. To do. For example, it can carry out by the method of immersion treatment at 25-80 degreeC for 10 second-10 minutes with potassium hydroxide or sodium hydroxide 10-200 g / L aqueous solution.
3) In the step of treating with the basic amino acid solution, the surface of the polyimide film is brought into contact with the basic solution containing the amino acid by a method such as spraying or dipping. For example, the lysine hydrochloride adjusted to pH 6 with potassium hydroxide or an arginine hydrochloride 30-300 g / L aqueous solution can be used at 30 to 60 ° C. for 10 seconds to 10 minutes.
4) In the step of applying a catalyst, in order to form nuclei for electroless base metal precipitation on the surface of the polyimide film, the catalyst is applied to a part or all of the surface of the polyimide film by a method such as adsorption. For example, by immersing in an ionic palladium catalyst solution at 30 to 60 ° C. for 1 to 10 minutes to adsorb palladium ions on the surface of the polyimide film, and then immersing in a reducing solution to reduce the palladium ions to metallic palladium. It can be carried out.
5) In the step of forming the nickel plating layer, nickel is deposited by an electroless plating method to form an electroless base nickel layer. For example, it can be performed by immersing in a commercially available electroless nickel plating bath at 25 to 45 ° C. for 2 to 20 minutes.
6) In the heating step, the polyimide film having the electroless nickel plating layer formed on both sides is heated. Preferably, it can be performed by heating at 80 ° C. to 150 ° C. for 1 minute to 24 hours.

  In the manufacturing method of the 1st flexible printed circuit board of this invention, using the double-sided nickel plating lamination | stacking polyimide film obtained in this way, one surface (A) of a polyimide film has a wiring pattern, and the other surface ( B) manufactures the flexible printed circuit board which has the part which a polyimide film exposes in part or the whole surface.

  Having a wiring pattern on one surface (A) of the flexible printed circuit board includes, for example, inner leads with a pitch of 5 μm to 1000 μm, outer leads with a pitch of 5 μm to 5000 μm, lands with a diameter of 20 μm to 5000 μm, 5 μm to 5 μm It has a line having a width of 10,000 μm and the wiring pattern is not particularly limited, and any pattern may be used.

  Having a portion where the polyimide film is exposed on a part of the other surface (B) of the flexible printed board means, for example, an inner lead having a wiring pattern on the surface (B), for example, a 5 μm to 1000 μm pitch, or 5 μm to 5000 μm. It has a pitch outer lead, a land having a diameter of 20 μm to 5000 μm, a line having a width of 5 μm to 10,000 μm, and the wiring pattern is not particularly limited, and any pattern may be used.

  The wiring pattern of each (A) surface and (B) surface is not particularly limited, and the heat treatment performed after wiring processing does not damage the interface between the polyimide film and the electroless nickel plating layer. It suffices to be able to remove the moisture.

  For example, when the pattern portion where the wiring pattern on the (A) plane and the wiring pattern on the (B) plane face each other and overlap through the polyimide film is viewed as a projected figure from the polyimide film surface, all points in the projected figure are: It is preferable that the shortest distance to the edge of the projected figure is within a predetermined distance. The shorter the predetermined distance (the maximum value of the shortest distance from all points in the projected figure to the edge of the projected figure), the easier the moisture is removed, and it is usually within 2.5 mm, preferably within 1 mm. More preferably, it is within 0.5 mm.

  In the pattern design, when there is a point in the projected figure where the shortest distance to the edge of the projected figure exceeds 2.5 mm, the pattern on the (A) plane and / or (B) plane is a passage of moisture such as slits and holes. It is preferable to form a portion where the polyimide film is exposed by forming an opening.

  Having a portion where the polyimide film is exposed on the entire other surface (B) of the flexible printed circuit board means that it does not have any wiring pattern or metal layer, that is, the surface (B) also has an electroless nickel plating layer removed. The polyimide film is exposed on the entire surface.

The flexible printed circuit board of this invention can be manufactured by the wiring processing method in any one of following (1)-(2) using a double-sided nickel plating laminated polyimide film.
(1) A method of manufacturing a flexible printed board by performing wiring processing by a semi-additive method using a double-sided nickel plating laminated polyimide film.
(2) A method of manufacturing a flexible printed board by performing wiring processing by a subtractive method using a double-sided nickel-plated laminated polyimide film.

The method of manufacturing a flexible printed circuit board that performs wiring processing by a semi-additive method using a double-sided nickel-plated laminated polyimide film of method (1) is further performed by any of the following methods (i) to (iii): Can do.
(I) A method of manufacturing a flexible printed circuit board by wiring processing for forming a plating resist layer after sequentially forming an electroless copper plating layer and an electrolytic copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Ii) A method for producing a flexible printed board by wiring processing for forming a plating resist layer after forming an electroless copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Iii) A method for producing a flexible printed circuit board by wiring processing for forming a plating resist layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.

  Table 1 shows the order of steps of the wiring processing methods (i) to (iii). In Table 1, the numerical values described in the column of each method indicate the order of steps. In addition, the method of said (i)-(iii) can be performed also except the order of Table 1.

After the electroless copper plating layer and the electrolytic copper plating layer are sequentially formed on the electroless nickel plating layer of the double-sided nickel plating laminated polyimide film, the wiring processing by the semi-additive method shown in Table 1 method (i) is performed. To explain an example of a method for manufacturing a flexible printed circuit board,
at least,
i-1) an electroless copper plating layer forming step of forming an electroless copper plating layer on the electroless nickel plating layer;
i-2) an electrolytic copper plating layer forming step of forming an electrolytic copper plating layer on the electroless copper plating layer;
i-3) a plating resist layer forming step of providing a plating resist layer on the electrolytic copper plating layer;
i-4) an exposure process of exposing through a photomask of a wiring pattern;
i-5) a development step of developing and removing a portion to be a wiring pattern of the plating resist layer;
i-6) A pattern plating step of removing the plating resist layer and further performing electrolytic copper plating on the exposed electrolytic copper plating layer to form an electrolytic copper pattern plating layer;
i-7) a plating resist layer removing step of removing the plating resist layer by peeling;
i-8) Flash etching in which the electrolytic copper plating layer, the electroless copper plating layer, and the electroless nickel plating layer exposed by peeling off the resist layer are removed so that the polyimide film surface appears, and a wiring pattern is formed on the film surface. Process,
Etc. can be performed in this order.

Production of flexible printed circuit board by wiring process by semi-additive method shown in Table 1 method (ii) of forming plating resist layer after forming electroless copper plating layer on electroless nickel plating layer of double-sided nickel plating laminated polyimide film To explain an example of the method,
at least,
ii-1) an electroless copper plating layer forming step of forming an electroless copper plating layer on the electroless nickel plating layer;
ii-2) a plating resist layer forming step of providing a plating resist layer on the upper surface of the electroless copper plating layer;
ii-3) an exposure step of exposing through a photomask of the wiring pattern;
ii-4) A development step for developing and removing a portion to be a wiring pattern of the plating resist layer;
ii-5) a pattern plating step of removing the plating resist layer and further performing electrolytic copper plating on the exposed electroless copper plating layer to form an electrolytic copper pattern plating layer;
ii-6) a plating resist layer removing step of removing the plating resist layer by peeling,
ii-7) A flash etching step of forming a wiring pattern on the film surface by removing the electroless copper plating layer and the electroless nickel plating layer exposed by peeling off the resist layer so that the polyimide film surface appears.
Etc. can be performed in this order.

Explaining an example of a method for producing a flexible printed circuit board that performs wiring processing by the semi-additive method shown in Table 1 (iii) of forming a plating resist layer on an electroless nickel plating layer of a double-sided nickel-plated polyimide film,
at least,
iii-1) a plating resist layer forming step of providing a plating resist layer on the upper surface of the electroless nickel plating layer;
iii-2) an exposure step of exposing through a photomask of the wiring pattern;
iii-3) a development step for developing and removing a portion to be a wiring pattern of the plating resist layer;
iii-4) an electroless copper plating layer forming step of forming an electroless copper plating layer on the electroless nickel plating layer exposed by removing the plating resist layer;
iii-5) A pattern plating step of further performing electrolytic copper plating on the electroless copper plating layer to form an electrolytic copper pattern plating layer,
iii-6) a plating resist layer removing step of removing the plating resist layer by peeling,
iii-7) A flash etching step of forming a wiring pattern on the film surface by removing the electroless nickel plating layer exposed by peeling of the resist layer so that the polyimide film surface appears.
Etc. can be performed in this order.

  Each process in the manufacturing method of the flexible printed circuit board which performs the wiring process by a semi-additive method is demonstrated.

  In the step of forming the electroless copper plating layer, a known electroless copper plating process can be selected as appropriate. Electroless copper plating is not particularly limited. For example, it uses substitution type electroless plating in which metal ions are reduced and metal is deposited by using electrons from the dissolution of the base metal, and electrons are used by oxidation of the reducing agent. Then, reducing agent type electroless plating in which metal ions are reduced and metal is deposited can be mentioned. Examples of the substitution type electroless copper plating include Elf Seed Process ES-PCD manufactured by Sugawara Eugene Corporation. As a reducing agent type electroless copper plating, for example, Sulcup PEA manufactured by Uemura Kogyo is cited. The thickness of the electroless copper plating layer formed in the formation process of the electroless copper plating layer may be any thickness, but is preferably 0.01 to 1 μm.

In the step of forming the electrolytic copper plating layer, a known copper plating process can be selected as appropriate. For example, the exposed portion of the copper foil is washed with an acid or the like, and typically a solution mainly composed of copper sulfate. In particular, electrolytic copper plating can be performed at a current density of 0.1 to 10 A / dm ^{2 using} a copper foil as a cathode electrode to form a copper layer. As the plating solution, for example, copper sulfate is 180 to 240 g / l, sulfuric acid 45 to 60 g / l, chloride ion 20 to 80 g / l, and thiourea, dextrin or thiourea and molasses added as additives. Can do. The thickness of the electrolytic copper plating layer formed in the forming process of the electrolytic copper plating layer may be any thickness, but preferably the thickness of one side is 0.1 to 1 μm.

  In each step in the methods (i) to (iii), a suitable cleaning process may be performed as necessary. For example, cleaning using an alkaline aqueous solution or an acid aqueous solution can be performed before forming the plating resist layer, and cleaning with an acidic degreasing or acidic aqueous solution can be performed before the pattern plating step.

  In the plating resist layer forming process, a photoresist layer is provided as a plating resist layer, and a negative photoresist or a positive photoresist can be used as the photoresist layer. Etc. can be used. As a method for forming a photoresist layer, typically, a negative dry film type resist is laminated by thermal lamination, or a positive liquid type resist is applied and dried to form on a metal plating layer. The method of doing is mentioned. In the case of the negative type, parts other than the exposed part are removed by development, while in the case of the positive type, the exposed part is removed by development. A dry film type resist can be easily obtained in a thick thickness. Examples of negative dry film type photoresists include UFG-155 manufactured by Asahi Kasei and RY-3215 manufactured by Hitachi Chemical.

  In the exposure step, projection exposure, contact exposure, laser direct exposure, and the like can be used, but the exposure method is not limited.

  In the development step, a known agent for developing and removing the photoresist layer can be appropriately selected and used. For example, the photoresist layer can be developed and removed by spraying an aqueous sodium carbonate solution (1% or the like).

In the pattern plating process, a known copper plating process can be selected as appropriate. For example, the exposed portion of the copper foil is washed with an acid or the like, and typically the copper foil in a solution mainly composed of copper sulfate. The cathode layer can be used to perform electrolytic copper plating at a current density of 0.1 to 10 A / dm ² to form a copper layer. As the plating solution, for example, copper sulfate is 180 to 240 g / l, sulfuric acid 45 to 60 g / l, chloride ion 20 to 80 g / l, and thiourea, dextrin or thiourea and molasses added as additives. Can do.

  In the plating resist layer removing step, a known agent for peeling and removing the photoresist layer can be appropriately selected and used. For example, the photoresist layer can be peeled and removed by spraying a caustic soda aqueous solution (2% or the like). it can.

  In the flash etching step, the thin film copper (electrolytic copper plating layer and electroless copper plating layer) and electroless nickel plating layer other than the copper wiring pattern portion exposed by dipping or spraying are removed using a flash etching solution. As the flash etching solution, a known one can be used, for example, one in which hydrogen peroxide is mixed with sulfuric acid or one containing a dilute aqueous solution of ferric chloride as a main component. Examples thereof include FE-830 manufactured by Asahi Denka Kogyo and AD-305E manufactured by Asahi Denka Kogyo. Here, when the thin copper foil is removed, the copper in the wiring pattern portion (wiring) is also dissolved. However, since the etching amount necessary for removing the thin copper foil is small, there is substantially no problem.

  If the pitch of the pattern to be manufactured becomes finer and the electroless nickel plating layer cannot be sufficiently removed by the above flash etching, the electroless nickel plating layer can be removed with an electroless nickel etching solution or an alkaline solution as necessary. The polyimide surface layer may be removed.

Next, an example of a method for producing a flexible printed board that performs wiring processing by a subtractive method using the double-sided nickel plating laminated polyimide film of the method (2) will be described.
at least,
2-1) an electroless copper plating layer forming step of forming an electroless copper plating layer on the electroless nickel plating layer;
2-2) an electrolytic copper plating layer forming step of forming an electrolytic copper plating layer on the electroless copper plating layer;
2-3) Etching resist layer forming step of providing an etching resist layer on the electrolytic copper plating layer,
2-4) an exposure process of exposing through a photomask of the wiring pattern;
2-5) A development process for developing and removing a portion to be a wiring pattern of the etching resist layer,
2-6) an etching process for etching away a portion not protected by the etching resist layer;
2-7) Etching resist layer removing step of removing the etching resist layer on the wiring pattern portion by peeling,
Etc. can be performed in this order.

  Each process in the method for manufacturing a flexible printed circuit board that performs wiring processing by the subtractive method will be described.

  In the step of forming the electroless copper plating layer, a known electroless copper plating process can be selected as appropriate. Electroless copper plating is not particularly limited. For example, it uses substitution type electroless plating in which metal ions are reduced and metal is deposited by using electrons from the dissolution of the base metal, and electrons are used by oxidation of the reducing agent. Then, reducing agent type electroless plating in which metal ions are reduced and metal is deposited can be mentioned. Examples of the substitution type electroless copper plating include Elf Seed Process ES-PCD manufactured by Sugawara Eugene Corporation. As a reducing agent type electroless copper plating, for example, Sulcup PEA manufactured by Uemura Kogyo is cited. The thickness of the electroless copper plating layer formed in the formation process of the electroless copper plating layer may be any thickness, but is preferably 0.01 to 1 μm.

In the step of forming the electrolytic copper plating layer, a known copper plating process can be selected as appropriate. For example, the exposed portion of the copper foil is washed with an acid or the like, and typically a solution mainly composed of copper sulfate. In particular, electrolytic copper plating can be performed at a current density of 0.1 to 10 A / dm ^{2 using} a copper foil as a cathode electrode to form a copper layer. As the plating solution, for example, copper sulfate is 180 to 240 g / l, sulfuric acid 45 to 60 g / l, chloride ion 20 to 80 g / l, and thiourea, dextrin or thiourea and molasses added as additives. Can do. The thickness of the electrolytic copper plating layer formed in the forming process of the electrolytic copper plating layer may be any thickness, but preferably the thickness of one surface is 0.1 to 10 μm.

  In each step, a suitable cleaning process may be performed as necessary. For example, before the plating resist layer is formed, cleaning using an aqueous alkali solution or an aqueous acid solution can be performed.

  In the etching resist layer forming step, a photoresist layer is provided, and a negative photoresist or a positive photoresist can be used as the photoresist layer, and a liquid or film-like one can be used. Can do. As a method for forming a photoresist layer, typically, a negative dry film type resist is laminated by thermal lamination, or a positive liquid type resist is applied and dried to form on a copper foil. A method is mentioned. In the case of the negative type, parts other than the exposed part are removed by development, while in the case of the positive type, the exposed part is removed by development. Examples of the negative dry film type photoresist include UFG-102 manufactured by Asahi Kasei.

  In the exposure step, projection exposure, contact exposure, laser direct exposure, and the like can be used, but the exposure method is not limited.

  In the development step, a known agent for developing and removing the photoresist layer can be appropriately selected and used. For example, the photoresist layer can be developed and removed by spraying an aqueous sodium carbonate solution (1% or the like).

  In the etching process, a known etching solution can be appropriately selected and used. For example, an electrolytic copper plating layer, an electroless copper plating layer, or an electroless nickel plating by spraying a ferric chloride aqueous solution, a cupric chloride aqueous solution, or the like. The layer can be etched away.

  In the etching resist layer removing step, a known agent for peeling and removing the photoresist layer can be appropriately selected and used. For example, the photoresist layer can be peeled and removed by spraying with a caustic soda aqueous solution (2% or the like). it can.

  If the pitch of the pattern to be manufactured becomes finer and the electroless nickel plating layer cannot be sufficiently removed by the above etching process, the electroless nickel plating layer can be removed with an electroless nickel etching solution or an alkaline solution as necessary. The polyimide surface layer may be removed.

  In the manufacturing method of the 1st flexible printed circuit board of this invention, one side (A) of the polyimide film obtained in this way has wiring, and the other side (B) is a polyimide in part or the whole surface. The flexible printed circuit board having a portion where the film is exposed is further heated in the range of 80 to 250 ° C., more preferably in the range of 100 to 200 ° C., further preferably in the range of 120 to 180 ° C. It is preferable to remove the moisture.

  If the heating temperature of the flexible printed circuit board after wiring is lower than the above range, the heating time may become long and productivity may be a problem. If it is higher than the above range, the moisture in the polyimide film will vaporize and expand at once. , The adhesion may be reduced.

  What is necessary is just to set time for heating time suitably, for example, Preferably it is 1 minute-24 hours, More preferably, it is 10 minutes-3 hours, More preferably, it is between 20 minutes-2 hours.

  With the above manufacturing method, without heating at a high temperature after the formation of the electroless nickel plating layer, and without forming the electroless nickel plating layer in a plurality of steps, it has excellent heat resistance against a long-term heat load, In addition, it is excellent in heat resistance against high-temperature and short-time heat load and solder heat resistance. One surface has a wiring pattern, and the other surface is a flexible printed circuit board having a part or whole of the exposed polyimide film. Can be manufactured.

  Note that the wiring is not limited to copper wiring, but may be other metal wiring.

<< Production Method of Second Flexible Printed Circuit Board of the Present Invention >>
In the method for producing the second flexible printed board of the present invention, as described above, a polyimide film obtained by heat treatment at a maximum heating temperature of 530 ° C. or higher at the time of imidization by one electroless nickel plating, or imidization (The maximum heating temperature may be 530 ° C. or higher or less than 530 ° C.) The polyimide film obtained by 490 ° C. or higher, preferably on both sides of the polyimide film heat-treated for 1 minute or longer, preferably After forming an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm, a double-sided nickel plating laminated polyimide film heated in a range of 100 to 180 ° C. for 2.5 hours or more is used. When heat-treating the polyimide film at 490 ° C. or higher, the heat treatment time is, for example, 1 to 5 minutes.

  As a polyimide film, for example, a polyimide film obtained by imidization at a maximum heating temperature of 530 ° C. or more from a tetracarboxylic acid component and a diamine component constituting a polyimide film that can be suitably used for various substrates such as a wiring substrate, or A polyimide film obtained from a tetracarboxylic acid component and a diamine component constituting a polyimide film that can be suitably used for various substrates such as a wiring substrate is heat-treated at a temperature of 490 ° C. or higher, preferably 490 to 550 ° C. (hereinafter, additional) What is also called heat treatment can be used. When the additional heat treatment is performed, the heat treatment time is, for example, 1 to 5 minutes. Moreover, in the manufacturing method of the 2nd flexible printed circuit board of this invention, the commercially available polyimide film which can be used suitably for various board | substrates, such as a wiring board, is heat-processed in 490 degreeC or more, Preferably it is 490-550 degreeC, and is used. You can also Also when using a commercially available polyimide film, the time for additional heat treatment is, for example, 1 to 5 minutes.

As a polyimide film, it is preferable that a linear expansion coefficient (50-200 degreeC) is near the linear expansion coefficient of copper laminated | stacked on a polyimide film, and the linear expansion coefficient (50-200 degreeC) of a polyimide film is 0.5 * 10 < ^- >. It is preferably ^{5 to} 2.8 × 10 ⁻⁵ cm / cm / ° C.

  In addition, a polyimide film having a thermal shrinkage rate of 0.05% or less is preferable because of its small thermal deformation.

  As the polyimide film, a polyimide film excellent in heat resistance, electrical insulation and the like can be suitably used.

  The thickness of the polyimide film is not particularly limited as long as the thickness can sufficiently support the metal layer and wiring pattern layer to be formed and can be handled without problems, and preferably 1 to 500 μm, more preferably 2 to 300 μm. More preferably, it is 5 to 200 μm, more preferably 5 to 175 μm, and particularly preferably 5 to 100 μm.

  As the polyimide film, a single layer, a multilayer film in which two or more layers are laminated, or a sheet-like one can be used.

  The polyimide film used in the method for producing the second flexible printed board of the present invention is produced according to a known method except that the maximum heating temperature at the time of imidization is higher than that of the conventional film, or a predetermined additional heat treatment is performed after imidization. can do.

A conventional polyimide film can be produced by a known method. For example, a single-layer polyimide film is
(1) A method in which a polyamic acid solution, which is a polyimide precursor, is cast or applied to a support and imidized;
(2) A method in which a polyimide solution is cast or applied to a support and heated as necessary.
Etc. can be obtained.
Two or more layers of polyimide film
(3) A polyamic acid solution, which is a polyimide precursor, is cast or coated on a support, and a polyamic acid solution, which is a polyimide precursor of the second layer or more, is sequentially cast or coated on the support before. A method of casting or coating on the upper surface of the polyamic acid layer and imidizing;
(4) A method in which a polyamic acid solution, which is a precursor of two or more layers of polyimide, is simultaneously cast or applied to a support and imidized;
(5) The polyimide solution is cast or coated on the support, and the polyimide solution of the second layer or more is sequentially cast or coated on the upper surface of the polyimide layer previously cast or coated on the support. Heating method,
(6) A method in which two or more layers of polyimide solution are simultaneously cast or coated on a support and heated as necessary.
(7) It can be obtained by a method of laminating two or more polyimide films obtained in (1) to (6) directly or via an adhesive.

  As a polyimide film, for example, tetra-containing a main component containing a component selected from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), and the like. Mainly a carboxylic acid component and a component selected from paraphenylenediamine (PPD), 4,4′-diaminodiphenyl ether (4,4′-DADE), 3,4′-diaminodiphenyl ether (3,4′-DADE), etc. A polyimide synthesized from a diamine component contained as a component can be used.

  Suitable polyimide films include, for example, the following polyimides (1) to (4).

  (1) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and paraphenylenediamine (PPD) and optionally 4,4′-diaminodiphenyl ether (4,4′-DADE) ) And polyimide produced from. In this case, the PPD / 4,4'-DADE (molar ratio) is preferably 100/0 to 85/15.

  (2) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4′-diaminodiphenyl ether Polyimide produced from (4,4'-DADE). In this case, s-BPDA / PMDA is preferably 15/85 to 85/15, and PPD / 4, 4'-DADE is preferably 90/10 to 10/90.

  (3) A polyimide produced from pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4'-diaminodiphenyl ether (4,4'-DADE). In this case, the 4,4′-DADE / PPD is preferably 90/10 to 10/90.

  (4) 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), paraphenylenediamine (PPD), and 4,4′-diaminodiphenyl ether (4 , 4'-DADE). In this case, it is preferable that BTDA / PMDA is 20/80 to 90/10, and PPD / 4, 4'-DADE is 30/70 to 90/10.

  In the synthesis | combination of a polyimide, you may use the other tetracarboxylic dianhydride and diamine which are the kind and quantity which do not impair the physical property of a polyimide.

  As the polyimide film, a polyimide film obtained by modifying the film surface with an inorganic oxide can be used. A polyimide film having a film surface modified with an inorganic oxide may have higher adhesion strength and heat resistance.

  The polyimide film modified with an inorganic oxide was manufactured by casting a solution of a polyimide precursor (polyamic acid or the like) obtained from an aromatic tetracarboxylic acid component and an aromatic diamine component on a support and heating. It is a film in which a solution containing an appropriate inorganic compound (for example, a metal compound) is applied to one or both sides of a self-supporting film of a polyimide precursor solution to modify the inorganic oxide. Inorganic oxide modification refers to a state modified with a metal oxide or an oxide of a semiconductor element that becomes a solid oxide similar to a metal oxide (hereinafter simply referred to as a metal oxide), and at least a part of the surface. Is a state where an inorganic substance (metal element or semiconductor element) -oxygen bond is formed.

  The polyimide film is preferably modified with aluminum oxide, titanium oxide or silicon oxide, and an aluminum-oxygen bond, a titanium-oxygen bond or a silicon (silicon) -oxygen bond is formed on at least a part of the surface. It is preferable.

  Inorganic oxide-modified state is not a complete oxide, for example, aluminum hydroxide, titanium hydroxyl group, silicon hydroxyl group, or dangling bonds are partly present, Bonds may be present.

  As the polyimide film, a polyimide film having at least one surface treated by corona discharge treatment, plasma treatment, chemical roughening treatment, physical roughening treatment or the like can also be used. This surface treatment may be performed before the additional heat treatment or may be performed after the additional heat treatment in the case where the additional heat treatment of the polyimide film described later is performed.

  The polyimide film used in the method for producing the second flexible printed circuit board of the present invention is manufactured by heating and imidization at a maximum heating temperature of 530 ° C. or higher, preferably 540 to 580 ° C. at the time of imidation, or A polyimide film produced by heating and imidization at a maximum heating temperature of less than 530 ° C is 490 ° C or higher, preferably 490 to 550 ° C, preferably 1 minute or longer (additional heat treatment). Further, even when a polyimide film is produced by heating and imidization at a maximum heating temperature of 530 ° C. or higher, the obtained polyimide film may be used after additional heat treatment at 490 ° C. or higher, preferably 490 to 550 ° C.

  The heat treatment for imidization is not particularly limited. However, in the case where no additional heat treatment is performed, usually, the imidation of the polymer and the evaporation / removal of the solvent are gradually carried out at a temperature of about 100 ° C to 580 ° C in 0.05 to 5 hours. It is appropriate to do so.

  The maximum heating temperature in the heat treatment for imidization in this case is 530 ° C. or higher, preferably 540 to 580 ° C. as described above, and can be appropriately selected according to the composition of the polyimide, the thickness of the film, and the like. .

  The time for heating at 530 ° C. or higher, preferably 540 to 580 ° C. can be appropriately selected, but is preferably 5 seconds to 3 minutes, more preferably 10 seconds to 2 minutes. Note that the heating temperature may not be constant.

  In addition to the method of setting the maximum heating temperature in the continuous process of heating and imidization to 530 ° C. or higher, in the method for producing the second flexible printed circuit board of the present invention, the maximum heating temperature during imidization is less than 530 ° C. The manufactured polyimide film or the commercially available polyimide film may be subjected to heat treatment (additional heat treatment) at 490 ° C. or higher, preferably 490 to 550 ° C., more preferably 510 to 530 ° C., and preferably 1 minute or longer. The heat treatment time is, for example, 1 to 5 minutes, preferably 1.5 to 3 minutes. Even when the heat treatment for imidization is performed at a maximum heating temperature of 530 ° C. or higher, the obtained polyimide film may be additionally heated at 490 ° C. or higher, preferably 490 to 550 ° C.

  In the case of additional heat treatment, the heat treatment for imidization is not particularly limited, but at first, the imidation of the polymer and the evaporation / removal of the solvent at a temperature of about 100 ° C. to 400 ° C. It is appropriate to carry out gradually in 0.1 to 3 hours.

  The heating temperature in the additional heat treatment is 490 ° C. or higher, preferably 490 to 550 ° C., and can be appropriately selected according to the composition of the polyimide, the thickness of the film, and the like. The heating temperature is more preferably 500 ° C. or higher, and further preferably 510 ° C. or higher. The heating temperature is more preferably 540 ° C. or less, and further preferably 530 ° C. or less. Note that the heating temperature may not be constant.

  The additional heat treatment time (490 ° C. or higher, preferably 490 to 550 ° C.) can be appropriately selected, but is preferably 1 to 5 minutes, more preferably 1.5 to 3 minutes. If the additional heat treatment time is too long, the properties of the resulting polyimide film may be deteriorated.

  In the manufacturing method of the 2nd flexible printed circuit board of the present invention, what was heat-treated at 490 ° C or more, preferably 490-550 ° C, more preferably 510-530 ° C can also be used. The heat processing time which heat-processes a commercially available polyimide film is 1 to 5 minutes, for example, More preferably, it is 1.5 to 3 minutes.

  The double-sided nickel-plated laminated polyimide film used in the method for producing the second flexible printed board of the present invention is a polyimide film obtained by heat treatment at the maximum heating temperature of 530 ° C. or higher at the time of imidation as described above, or imidization (maximum The heating temperature may be 530 ° C. or higher, or less than 530 ° C.). The polyimide film (which may be a commercial product) obtained by heat treatment is 490 ° C. or higher, preferably 1 minute or longer. An electroless nickel plating layer, preferably an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm, is formed on both sides of the polyimide film by one plating, and then 2 in the range of 100 to 180 ° C. It can be obtained by heating for 5 hours or more.

  If the thickness of the electroless nickel plating layer of the double-sided nickel-plated laminated polyimide film is less than the above range, the decrease in adhesion strength due to copper diffusion during long-term heat load cannot be sufficiently suppressed, and adhesion due to long-term heat load May deteriorate. If it is thicker than the above range, the polyimide film covered on both sides with the electroless nickel plating layer will block the passage of moisture as much as possible. Adhesiveness with a polyimide film may deteriorate. Furthermore, when the electroless nickel plating layer is thick, it is difficult to remove the base including the electroless nickel plating layer in forming the wiring pattern, which may cause an undercut in the wiring by strengthening the removal process.

  In the manufacturing method of the 2nd flexible printed circuit board of the present invention, after forming an electroless nickel plating layer on both sides of a polyimide film, the obtained double-sided nickel plating lamination polyimide film is 100-180 ° C, preferably 130-160 ° C. For 2.5 hours or more, preferably 3 to 24 hours. Note that the heating temperature may not be constant.

  The heating temperature of the double-sided nickel-plated laminated polyimide film is preferably in the range of 100 to 180 ° C, preferably in the range of 130 to 160 ° C, and more preferably in the range of 140 to 155 ° C. If the heating temperature is lower than the above range, the moisture in the polyimide film may not be sufficiently removed / reduced. If the heating temperature is higher than the above range, the moisture in the polyimide film vaporizes and expands at once, and the electroless nickel plating layer Adhesion with the polyimide film may be reduced.

  The heating time is 2.5 hours or more, preferably 3 to 24 hours, and more preferably 3 to 10 hours. The upper limit of the heating time is not particularly limited, but if the heating time is too long, productivity may become a problem.

  When the electroless nickel plating layer is formed on both surfaces of the polyimide film, as a pretreatment, both surfaces of the polyimide film are surface-treated using an alkali metal hydroxide or an aqueous solution thereof. This is preferable in order to ensure adhesion at the polyimide film interface. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.

  Examples of the method for producing a double-sided nickel-plated laminated polyimide film from the polyimide film include the method described in the first method for producing a flexible printed board of the present invention. Also in the manufacturing method of the 2nd flexible printed circuit board of the present invention, a double-sided nickel plating lamination polyimide film can be manufactured by the same method as the manufacturing method of the 1st flexible printed circuit board. However, in the step of heating the polyimide film having the electroless nickel plating layer formed on both sides, as described above, the double-sided nickel plating laminated polyimide film is 100 to 180 ° C., preferably 130 to 160 ° C. for 2.5 hours or more, preferably Is heated for 3-24 hours.

  In the manufacturing method of the 2nd flexible printed circuit board of this invention, the flexible printed circuit board which has a wiring pattern in the at least one surface of a polyimide film is manufactured using the double-sided nickel plating lamination | stacking polyimide film obtained in this way. The polyimide film produced by the method for producing the second flexible printed board of the present invention does not need to have a wiring pattern on both surfaces, or a portion where the polyimide film is exposed on a part or the entire surface. According to the manufacturing method of the 2nd flexible printed circuit board of the present invention, the flexible printed circuit board in which one side has wiring and the other side has a metal layer in the whole surface can also be manufactured.

  Having a wiring pattern on one surface of the flexible printed circuit board means that the wiring pattern is, for example, an inner lead with a pitch of 5 μm to 1000 μm, an outer lead with a pitch of 5 μm to 5000 μm, a land with a diameter of 20 μm to 5000 μm, a width of 5 μm to 10,000 μm. The wiring pattern is not particularly limited, and may be any pattern.

The flexible printed circuit board of this invention can be manufactured by the wiring processing method in any one of following (1)-(2) using a double-sided nickel plating laminated polyimide film.
(1) A method of manufacturing a flexible printed board by performing wiring processing by a semi-additive method using a double-sided nickel plating laminated polyimide film.
(2) A method of manufacturing a flexible printed board by performing wiring processing by a subtractive method using a double-sided nickel-plated laminated polyimide film.

  In the second flexible printed circuit board manufacturing method of the present invention, the wiring process is performed by the semi-additive method or the subtractive method in the same manner as in the first flexible printed circuit board manufacturing method of the present invention. A substrate can be manufactured.

  In order to reinforce the copper plating film, the obtained flexible printed board can be heated in the range of preferably 80 to 250 ° C., if necessary.

  With the above manufacturing method, without heating at a high temperature after the formation of the electroless nickel plating layer, and without forming the electroless nickel plating layer in a plurality of steps, it has excellent heat resistance against a long-term heat load, In addition, it is possible to manufacture a flexible printed circuit board that is excellent in heat resistance against high-temperature short-time heat load and solder heat resistance.

  Note that the wiring is not limited to copper wiring, but may be other metal wiring.

  Here, in order to clearly explain the essence, an embodiment of a simple polyimide film is shown, but the present invention is not limited to this. For example, by using a polyimide film having through holes for conducting both surfaces by laser processing, punching, or the like, electroless nickel plating or the like may be performed simultaneously on both surfaces and the inside of the through holes. Furthermore, the effect is the same even if there is an adhesive layer or an inner layer substrate between the polyimide films on both sides. Typically, it is used for forming the outer layer wiring of a multilayer wiring board in which polyimide films are laminated on both sides of the inner layer substrate. The present invention is applicable.

  Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by the examples.

(Measurement of electroless nickel plating layer thickness)
The thickness of the electroless nickel plating layer was determined as follows. That is, after laminating a dry film resist UFG-072 (manufactured by Asahi Kasei E-Materials Co., Ltd.) on a polyimide film on which an electroless nickel plating layer is formed with a thermal laminate, a part of the exposure apparatus UFX-2023B-AJM01 (USHIO) And an exposure amount of 140 mJ / cm ² . Subsequently, the unexposed dry film resist was removed using a 1% sodium carbonate aqueous solution, and then the dry film was removed using a ferric chloride aqueous solution to remove the exposed electroless nickel plating layer. Subsequently, the dry film resist was removed using a 2% aqueous sodium hydroxide solution to form a step between a portion where the electroless nickel plating layer was present and a portion where the electroless nickel plating layer was absent. The thickness of the step was directly measured by an atomic force microscope (NANOSCOPE IIIa, manufactured by Digital Instruments). Then, this measurement was performed at arbitrary 10 points, and the average value was adopted.

(Measurement of peel strength)
Using a tensile tester (manufactured by Ebara Seisakusho Co., Ltd.) to peel off the copper plating layer from a flexible printed wiring board having a line width of 10 mm formed by wiring processing and cut into a strip shape including a line of 10 mm width 90 ° peel strength measurement was performed at the initial stage, after a high temperature and short time heat load, and after a long time heat load. Here, the initial is a heat treatment performed at 150 ° C. for 1 hour after the wiring processing, and the high temperature and short time thermal load is 260 ° C. so that the circuit formation surface is further in contact with the solder from the initial state. The liquid was indirectly liquid for 10 seconds in the solder bath, and after long-term heat load, it was further subjected to oven heating at 150 ° C. × 168 hours from the initial state.

(Examples A1 to A3, Reference Examples A1 to A2, Comparative Examples A1 to A2)
[Degreasing and surface treatment with alkali metal hydroxide aqueous solution]
First, a 10 cm × 10 cm polyimide film (manufactured by Ube Industries, Upilex 25SGA) is treated at 50 ° C. for 2 minutes on both sides of the polyimide film using Elf Seed Process Cleaner ES-100 (manufactured by Sugawara Eugleite). After performing the degreasing treatment by this, surface treatment with an aqueous alkali metal hydroxide solution was performed by treating at 50 ° C. for 30 seconds using an elf seed process modifier ES-200 (manufactured by Ebara Eugelite).

[Catalyst application and reduction treatment]
After both sides of the modified polyimide film were treated with an elf seed process activator ES-300 (manufactured by Ebara Eugelite Co., Ltd.) at 50 ° C. for 2 minutes, elf seed process accelerator ES- The reduction treatment was carried out by treating at 400 ° C. (manufactured by Ebara Eugelite) at 35 ° C. for 2 minutes.

[Formation of electroless nickel plating layer]
Next, electroless nickel plating was carried out at 35 ° C. for the time shown in Table 2 using electroless nickel plating ES-500 (manufactured by Ebara Eugene Corporation), and the thickness of the electroless nickel shown in Table 2 was applied to both sides of the polyimide film. A plating layer was formed.

[Heat treatment]
After the electroless nickel plating layer was formed, heat treatment was performed at the time and temperature of the heat treatment shown in Table 2 in a drying oven, and then the film was taken out from the drying oven.

[Formation of copper plating layer for circuit formation]
Prior to electrolytic copper plating, after activating the electroless nickel plating film by conducting treatment at 25 ° C. for 1 minute in the Elf Seed Process ES-PDC, which is a substitution type electroless copper plating, the conductivity is improved. Then, electrolytic copper plating was performed in a copper sulfate plating bath at a current density of 2 A / dm ² for 22 minutes. The electrolytic copper plating thickness was 10 μm.

[Circuit formation]
By wiring processing using the subtractive method described in the above method (2), one surface (A) of the polyimide film has a wiring width of 10 mm, and the other surface (B) has the polyimide film exposed on the entire surface. A flexible printed circuit board was produced.

Details of the circuit formation are shown below.
The polyimide film with the electrolytic copper plating layer formed on both sides was washed with a 2% sodium hydroxide aqueous solution and a 5% sulfuric acid aqueous solution. Subsequently, dry film resist UFG-072 (manufactured by Asahi Kasei E-Materials Co., Ltd.) was laminated by thermal lamination, and a part of the dry film resist UFG-072 (manufactured by Ushio Electric Co., Ltd.) was exposed to 140 mJ / cm. ² was exposed through a mask capable of forming a 10 mm wide line. Subsequently, after removing the dry film resist not exposed with 1% aqueous sodium carbonate solution, the exposed electrolytic copper plating layer, electroless copper plating layer, and The electrolytic nickel plating layer was removed simultaneously. Subsequently, the dry film resist is removed with a 2% aqueous sodium hydroxide solution, one side (A) of the polyimide film has a line width of 10 mm, and the other side (B) exposes the polyimide film on the entire surface. A flexible printed circuit board having a portion was produced.

  The obtained flexible printed circuit board was heat-treated at 150 ° C. for 1 hour, and then the initial peel strength was measured. Furthermore, the peel strength after a high-temperature short-time heat load and the peel strength after a long-term heat load of the flexible printed circuit board were measured. The results are shown in Table 2.

  From the results, the flexible printed circuit boards of Examples A1 to A3 have good adhesion strength both after the initial and high-temperature and short-time heat loads and after the long-term heat load. In Reference Example A1, the adhesion strength comparable to that of Examples A1 to A3 was obtained after the initial and high-temperature and short-time heat load, but the adhesion strength was significantly deteriorated after the long-term heat load. In Reference Example A2, sufficient adhesion strength was not obtained from the beginning. In Comparative Example A1, electroless nickel plating was not uniformly deposited. In Comparative Example A2, blistering occurred during heat treatment after electroless nickel plating. From these facts, it can be seen that even when an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm is formed on both surfaces of the polyimide film at one time, it has good adhesion reliability.

(Examples B1 to B4, Comparative Examples B1 to B6)
[Production of polyimide film]
After adding a predetermined amount of N, N-dimethylacetamide and paraphenylenediamine (PPD) to the polymerization tank, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s -BPDA) was added to and reacted with PPD to approximately equimolar to obtain a polyamic acid solution. And the monostearyl phosphate ester was added to this polyamic acid solution in the ratio of 0.25 mass part with respect to 100 mass parts of polyamic acid, and the polyamic acid solution composition was obtained.

  This polyamic acid solution composition is continuously extruded from a slit of a T-die mold onto a smooth metal support in a casting / drying furnace to form a thin film, heated at 150 ° C. for a predetermined time, and then peeled off from the support. A self-supporting film was obtained.

  Next, the both ends of the self-supporting film in the width direction are gripped and inserted into a continuous heating furnace (curing furnace), and the film is heated from 100 ° C. under the condition that the maximum heating temperature is the temperature shown in Table 3. Thus, a long polyimide film having an average film thickness of 25 μm was produced.

  In Example B3, Example B4, and Comparative Example B6, the four sides of the polyimide film obtained in this way were gripped using a clip on a metal frame and held in a heating furnace at 520 ° C. for 2.5 minutes. Additional heat treatment was performed.

[Degreasing and surface treatment with alkali metal hydroxide aqueous solution]
The polyimide film obtained as described above is cut into a 10 cm × 10 cm square shape, and both sides of the polyimide film are treated at 50 ° C. for 2 minutes using Elf Seed Process Cleaner ES-100 (manufactured by Ebara Eugene Corporation). After performing the degreasing treatment by this, surface treatment with an alkali metal hydroxide aqueous solution was performed by treating at 50 ° C. for 20 seconds using an elf seed process modifier ES-200 (manufactured by Ebara Eugelite Co., Ltd.).

[Catalyst application and reduction treatment]
After both sides of the modified polyimide film were treated with an elf seed process activator ES-300 (manufactured by Ebara Eugelite Co., Ltd.) at 50 ° C. for 2 minutes, elf seed process accelerator ES- The reduction treatment was carried out by treating at 400 ° C. (manufactured by Ebara Eugelite) at 35 ° C. for 2 minutes.

[Formation of electroless nickel plating layer]
Subsequently, electroless nickel plating was carried out at 35 ° C. for 8 minutes with electroless nickel plating ES-500 (manufactured by Ebara Eugene Corporation) to form an electroless nickel plating layer having a thickness of 0.13 μm on both surfaces of the polyimide film.

[Heat treatment]
After the formation of the electroless nickel plating layer, heat treatment was performed at a heat treatment time and temperature shown in Table 3 in a drying oven, and then the electroless nickel plating layer was taken out from the drying oven.

[Formation of copper plating layer]
Prior to electrolytic copper plating, after activating the electroless nickel plating film by conducting treatment at 25 ° C. for 1 minute in the Elf Seed Process ES-PDC, which is a substitution type electroless copper plating, the conductivity is improved. Then, electrolytic copper plating was performed for 22 minutes at a current density of 2 A / dm ² in a copper sulfate plating bath to prepare a double-sided substrate in which a copper plating layer was formed on both sides of the polyimide film. The electrolytic copper plating thickness was 10 μm.

  The obtained double-sided substrate was heat-treated at 150 ° C. for 1 hour, and then the initial peel strength was measured. Furthermore, the peel strength after a high-temperature short-time heat load and the peel strength after a long-term heat load of the flexible printed circuit board were measured. The results are shown in Table 3.

  From the results, the double-sided substrates of Examples B1 to B4 have good adhesion strength both after the initial and high-temperature and short-time heat loads and after the long-term heat loads. In Comparative Examples B1 to B4 using a polyimide film having a maximum heating temperature of 520 ° C. at the time of imidization and not subjected to additional heat treatment after imidation, the adhesion strength was significantly deteriorated after a long-term heat load. A polyimide film imidized at a maximum heating temperature of 550 ° C. and a polyimide film heat-treated at 520 ° C. for 2.5 minutes after imidation are used, but the heating time of the heat treatment after forming the electroless nickel plating layer is as short as 2 minutes. In Comparative Examples B5 to B6, the adhesion strength was remarkably deteriorated after a long-term heat load. Therefore, the electroless nickel plating layer is applied once to both surfaces of the polyimide film heat-treated at the maximum heating temperature of 530 ° C. or higher during imidation or the polyimide film heat-treated in the range of 490 to 550 ° C. for 1 to 5 minutes after imidation. When the double-sided nickel-plated laminated polyimide film is used and then heated in the range of 100 to 180 ° C. for 2.5 hours or more, it can be seen that the obtained flexible printed circuit board has good adhesion reliability.

Claims (5)

Using a double-sided nickel-plated laminated polyimide film, one side (A) of the polyimide film has wiring, and the other side (B) has a portion where the polyimide film is exposed partially or entirely by wiring processing. In a method of manufacturing a printed circuit board,
The double-sided nickel plating laminated polyimide film to be used is formed in a range of 100 to 150 ° C. after forming an electroless nickel plating layer having a thickness of more than 0.1 μm and less than 0.3 μm on both sides of the polyimide film by one plating. Heated laminated film,
A method for producing a flexible printed circuit board, wherein the polyimide film uses polyimide produced from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine.   The method for producing a flexible printed circuit board according to claim 1, wherein surface treatment of the polyimide film with an alkali metal hydroxide or an aqueous solution thereof is performed before forming the electroless nickel plating layer on both surfaces of the polyimide film.   The method for producing a flexible printed circuit board according to claim 1 or 2, further comprising a step of heating the flexible printed circuit board obtained by wiring processing in a range of 80 to 250 ° C.   The method for producing a flexible printed circuit board according to any one of claims 1 to 3, wherein the wiring processing is wiring processing by a semi-additive method or a subtractive method. The flexible printed circuit board according to claim 4, wherein the wiring processing is wiring processing by a semi-additive method, and includes a step of forming a plating resist layer by any one of the following methods (i) to (iii): The manufacturing method.
(I) A method of forming a plating resist layer after sequentially forming an electroless copper plating layer and an electrolytic copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Ii) A method of forming a plating resist layer after forming an electroless copper plating layer on an electroless nickel plating layer of a double-sided nickel plating laminated polyimide film.
(Iii) A method of directly forming a plating resist layer on the electroless nickel plating layer of the double-sided nickel plating laminated polyimide film.