JP4540100B2 - Two-layer flexible copper-clad laminate and method for producing the two-layer flexible copper-clad laminate - Google Patents

Description

  The present invention relates to a so-called two-layer flexible copper-clad laminate in which a conductor layer and a flexible base material layer are directly bonded without using an adhesive layer, and a method for producing the two-layer flexible copper-clad laminate.

  Polyimide resin is flexible and flexible, and has excellent properties such as mechanical strength, heat resistance, and electrical properties. Traditionally, tape automate bonding (a type of flexible printed wiring board and flexible printed wiring board) TAB) has been widely used as a base material for products and the like.

  In order to obtain the above products, a three-layer substrate bonded with a copper foil using an adhesive has been conventionally used. However, demands for downsizing electrical and electronic products in recent years have become stronger, and it has been required to reduce the thickness and size of flexible printed wiring boards for placement in narrow spaces, improving wiring density and improving bending strength. From the viewpoint of improvement, the supply of a two-layer substrate in which the adhesive layer is omitted and the conductor layer is directly provided on the surface of the polyimide resin film has been activated.

  Vapor deposition, casting, plating, and direct metallization methods have been widely used as methods for forming a copper layer on a surface of a polyimide resin film without using an adhesive to form a two-layer substrate. Among these, in particular, the direct metallization method disclosed in Patent Document 1, Patent Document 2, and the like, in particular, can maintain relatively good adhesion between the polyimide resin film and the copper layer. Has been advocated.

  Unlike ordinary rigid-type printed wiring boards, the above-mentioned flexible printed wiring boards and COF and TAB products that can be said to be a kind of flexible printed wiring boards are generally formed with extremely fine fine pitch circuits. In addition, since the high-temperature heat treatment is performed in the manufacturing process, the peel strength after heating from the polyimide film base material of the conductor layer has been considered as an important product quality. And those skilled in the art recognize that it is possible to improve the peel strength after heating by providing a Cr-based intermediate layer as a seed layer between the polyimide film substrate and the copper conductor layer. In addition, as shown in Patent Document 3, development of a two-layer flexible copper-clad laminate provided with an intermediate layer containing chromium and nickel has been underway.

  As for the peel strength after heating, it is common for those skilled in the art to use the value after heating for 168 hours in an air atmosphere at 150 ° C. as a substitute characteristic (hereinafter referred to simply as “after heating” in this specification). This is called “stripping strength”). The peeling strength after heating of the conventional two-layer flexible copper clad laminate showed a value of around 0.4 kgf / cm.

JP 2001-73159 A Japanese Patent Laid-Open No. 2001-72787 JP 2004-31588 A

  However, due to the recent increase in international environmental awareness in order to improve the above-mentioned peeling strength after heating, the crackdown on the use of toxic substances such as chromium has been strengthened, crossing the border of products using chromium. There is a growing tendency to restrict trading.

  In addition, if a seed layer having a high nickel content is formed, it is difficult to remove the seed layer with a copper etchant, and a nickel component may remain between the circuits, which may be a starting point for occurrence of surface layer migration.

  Therefore, in the market, it is a case of using a direct metallization method that can obtain a two-layer state of a polyimide film substrate and a conductor layer, and the polyimide resin film and the conductor layer are good without using Cr Thus, a two-layer flexible copper-clad laminate that can maintain the peel strength and chemical resistance performance after heating and can be satisfactorily etched with a copper etchant has been desired.

  Therefore, as a result of diligent research, the present inventors have adopted a flexible copper-clad laminate having a layer structure according to the following invention, and without using a Cr-based seed layer, good peeling strength after heating. The idea was to obtain chemical resistance and good etching performance. Hereinafter, the present invention will be described.

(Flexible copper-clad laminate)
Before describing the present invention, in order to facilitate understanding of the present invention, a brief description will be given of the theory adopted to improve the peel strength after heating. The phenomenon in which the peel strength after heating deteriorates as viewed from the normal peel strength is simply due to the deterioration of the constituent resin of the polyimide resin film substrate after high-temperature heating. If the heating temperature is constant, the deterioration level of the constituent resin of the polyimide resin film substrate depends on the metal component constituting the interface with the polyimide resin film substrate of the conductor layer. That is, it is considered that the metal component contributes as a decomposition catalyst for the constituent resin of the polyimide resin film substrate. In particular, copper, which is a main component constituting the conductor layer, has been proposed for a long time to contribute as a decomposition catalyst for base resins such as epoxy and polyimide, which are organic materials.

  Accordingly, conventionally, the copper component constituting the conductor layer (in the above and below, the copper layer and the seed layer are collectively referred to as “conductor layer”) does not diffuse toward the base resin during high-temperature heating. As described above, a technique has been employed in which a high melting point metal component equal to or higher than copper is provided as a barrier layer, and the peeling strength after heating is kept high by preventing diffusion of copper.

  On the other hand, it is known that it is necessary to form a good physical adhesion structure at the interface between the conductor layer and the polyimide resin film layer in order to keep the peel strength after heating high. ing. That is, an electrolytic copper foil or the like used for a normal copper-clad laminate has a roughened surface on which fine copper particles are adhered, and this roughened surface can be used as an adhesive surface with a base resin. The copper particles are hard to get into the base resin and exert an anchor effect. The more uniform and large the fine copper particles are, the higher the peel strength after heating. However, when the conductor layer is formed directly on the surface of the polyimide resin film substrate by the direct metallization method, it is not possible to form a rough surface like a normal copper foil. It has been considered that it is almost impossible to obtain a strength improvement effect.

  As described above, in order to increase the peeling strength after heating, it is considered that the seed layer must be designed in consideration of the following two points. That is, the seed layer must be excellent in adhesion to the polyimide resin film layer and excellent in etching characteristics and chemical resistance while preventing decomposition of the copper polyimide resin film in a high temperature environment. .

  As a two-layer flexible copper-clad laminate that satisfies these requirements, “2 obtained by a direct metallization method in which a seed layer is formed on one side of a polyimide resin film substrate and a copper layer is formed on the seed layer 2” In the single-layer flexible copper-clad laminate, the seed layer is a single-sided two-layer flexible copper-clad laminate in which a cobalt layer in contact with a polyimide resin film substrate and a nickel-cobalt film are in a laminated state. To do. A cross section of this single-sided two-layer flexible copper-clad laminate is schematically shown in FIG. The drawings used for explaining the present invention are schematic diagrams showing the layer configuration of the two-layer flexible copper-clad laminate according to the present invention in an easy-to-understand manner, and the layer thickness is the actual product thickness. It is not something that was made to correspond.

  In addition, in the double-sided two-layer flexible copper-clad laminate obtained by a direct metallization method in which a seed layer is formed on both sides of a polyimide resin film substrate and a copper layer is formed on each seed layer, The layer employs a double-sided, two-layer flexible copper-clad laminate in which a cobalt layer in contact with a polyimide resin film substrate and a nickel-cobalt film are in a laminated state. A cross section of this double-sided two-layer flexible copper-clad laminate is schematically shown in FIG.

  The above flexible copper-clad laminate is characterized by the structure of the seed layer, and is composed of “cobalt film” and “nickel-cobalt film”. These two two-layer flexible copper-clad laminates are either a flexible copper-clad laminate 1a in which the conductor layer 2 (including the seed layer 3) is formed only on one side of the polyimide resin film F as shown in FIG. The only difference is the flexible copper-clad laminate 1b in which the conductor layer 2 as shown is formed on both sides of the polyimide resin film F, and the essential configuration is the same. Therefore, since it thinks that it can understand also about a double-sided two-layer flexible copper clad laminated board by explaining about a single-sided two-layer flexible copper clad laminated board, it demonstrates below focusing on a single-sided two-layer flexible copper clad laminated board.

  The layer structure of the single-sided two-layer flexible copper clad laminate 1a is such that the single-sided surface of the polyimide resin film F and the cobalt layer 4 are in contact with each other, as can be seen from FIG. The cobalt layer 4 is necessary for ensuring adhesion with the polyimide resin film F and confirming the peel strength after heating.

  Strictly speaking, the cobalt layer 4 is not a pure cobalt layer but a mixed layer of cobalt particles (partly considered to be cobalt oxide) 5 and the polyimide resin R. When this state is observed with a transmission electron microscope, it is as shown in FIG. FIG. 3 shows an enlarged photograph showing the mixed state of the cobalt layer at 500,000 times. From these, the cobalt particles 5 grow in a dendritic shape and seem to be in a state of being hard to be embedded in the polyimide resin R. Therefore, the dendritic cobalt particles 5 are considered to be anchors for improving the physical adhesion with the polyimide resin film F.

Then, the cobalt layer is of is preferably in the range of ^{40mg / m 2 ~300mg / m 2} ( in terms of thickness 5Nm～34nm) weight thickness. When the weight thickness of a cobalt layer is less than 40 mg / m < ² >, the adhesiveness of a cobalt layer and a polyimide resin film cannot fully be improved. On the other hand, when the weight thickness of the cobalt layer exceeds 300 mg / m ² , the cobalt layer rich in reactivity becomes thick, and the cobalt layer dissolves at the time of circuit etching and contact with the plating solution. Will deteriorate.

  In the present invention, the nickel-cobalt film 6 is located on the cobalt layer 4. The nickel-cobalt film 6 and the cobalt layer 4 are formed by a manufacturing method based on the direct metallization method described below, and the nickel-cobalt film 6 and the cobalt layer 4 are very excellent interlayers. It shows adhesion. In addition, the nickel-cobalt film 6 exhibits very excellent interlayer adhesion with the copper layer.

  As will be described later, this cobalt film is formed by subjecting a polyimide resin film of the direct metallization method to an alkali treatment to open the imide ring to form a carboxyl group on the surface, and using the acid solution for the carboxyl group formed by the ring opening. The polyimide resin film is made by repeating the steps of forming a carboxyl cobalt salt by contacting the neutralized carboxyl group with a cobalt ion-containing solution to adsorb a cobalt component and reducing the carboxyl cobalt salt. A cobalt layer in contact with the surface is obtained at the same time.

  Next, a nickel-cobalt film 6 is provided on the surface of the cobalt film 4. This nickel-cobalt film 6 has excellent corrosion resistance and is intended to improve the chemical resistance of the peel strength by preventing erosion by an acidic solution when a flexible copper-clad laminate is processed into a flexible printed wiring board. At the same time, it acts as a diffusion barrier to the polyimide resin film of copper that degrades the peel strength after heating the circuit.

  Since this nickel-cobalt film is a mixed layer of cobalt particles and polyimide resin, the surface of the cobalt film and nickel ions and cobalt ions are removed using a direct metallization method as described later. It can be obtained by repeating the steps of bringing the solution into contact with each other, forming a carboxyl nickel salt and a carboxyl cobalt salt, and reducing the carboxyl nickel salt and the carboxyl cobalt salt.

  The nickel-cobalt film 6 desirably employs a composition of 50% by weight to 95% by weight of nickel and the remaining cobalt (a composition that does not take into account inevitable impurities in the nickel-cobalt film is employed). Here, the nickel-cobalt film is used because it has excellent corrosion resistance, is easily dissolved in an acid solution used for circuit etching, and facilitates dissolution and removal of nickel that is difficult to dissolve in a copper etching solution by itself. Therefore, when the cobalt content is less than 5 wt%, it becomes difficult to dissolve the nickel-cobalt film with the copper etching solution, and the nickel component tends to remain as an etching residue during circuit etching, resulting in insufficient circuit insulation. This is a cause of occurrence of short circuit and surface layer migration. On the other hand, when the content ratio of cobalt exceeds 50 wt%, the corrosion resistance of the nickel-cobalt film is lowered and the chemical resistance performance of the circuit is deteriorated. Furthermore, in order to more reliably prevent the occurrence of etching residue and improve the chemical resistance, it is preferable to have a composition containing nickel 60 wt% to 90 wt% and cobalt 40 wt% to 10 wt%.

  The thickness of the seed layer is also a problem in order to improve the adhesion with the polyimide resin substrate and at the same time improve the chemical resistance. Considering the mechanism of the occurrence of the phenomenon of etching liquid or plating liquid from the edge portion of the circuit, when the circuit 9 is exposed to a plating liquid during or after circuit etching, as shown in FIG. An acidic solution such as an etching solution permeates the interface A between the polyimide resin substrate F and the adhesiveness of the circuit, and the solution enters the interface A to dissolve the seed layer 3. Therefore, the thinner the seed layer 3 is, the less the solution enters and the better the chemical resistance. This chemical resistance is evaluated by alternative methods such as hydrochloric acid resistance.

The nickel-cobalt film 6 preferably has a weight thickness in the range of 380 mg / m ^{2 to} 750 mg / m ² (converted thickness 43 nm to 84 nm). When the weight thickness of the nickel-cobalt film is less than 380 mg / m ² , it cannot serve as a copper diffusion prevention barrier under heating conditions of 150 ° C. × 168 hours, and the chemical resistance of the peel strength is improved. It can not be done. When the weight thickness of the nickel-cobalt film 6 exceeds 750 mg / m ² , simultaneous removal with a copper etching solution cannot be performed well when performing copper circuit etching, and the nickel-cobalt film 6 tends to remain.

  The copper layer 7 is positioned on the surface of the nickel-cobalt film 6 constituting the seed layer 3. As the thickness of the copper layer 7, any thickness can be adopted depending on the application when used as a flexible printed wiring board, and there is no particular limitation on the thickness. The copper layer 7 is a main body as the conductor layer 2 and constitutes a conductor such as a signal circuit and a power circuit when a circuit is formed.

  By adopting a single-sided or double-sided flexible copper-clad laminate with the above layer structure, it has a peeling strength after heating after heating at 150 ° C. for 168 hours without containing repellent components such as Cr. It is considered to be good, and further excellent in chemical resistance and excellent in solubility in a copper etching solution.

  Further, in the case of a single-sided two-layer flexible copper-clad laminate, as shown in FIG. 5, the other side of the surface on which the copper layer 7 is present is covered with a water-resistant film 8 such as a PET (polyethylene terephthalate) film, thereby allowing flexible It is possible to prevent water absorption and moisture absorption from the other side when exposed to a solution in a processing process for a printed wiring board, and to obtain a higher peeling strength after heating.

(Method for producing a two-layer flexible copper-clad laminate)
The method for producing a single-sided, two-layer flexible copper-clad laminate according to the present invention comprises the steps (a) to (j) described below.

(A) A ring-opening step of forming an carboxyl group on the surface by alkali-treating the exposed surface of the polyimide resin film having one surface or one surface of the polyimide resin film covered with a water-resistant film to open the imide ring.
(B) A neutralization step of neutralizing a carboxyl group formed on one side by ring opening using an acid solution.
(C) A cobalt ion adsorption step of forming a carboxyl cobalt salt on one side of a polyimide resin film by bringing a neutralized carboxyl group on one side into contact with a cobalt ion-containing solution to adsorb a cobalt component.
(D) The cobalt film formation process which reduces the carboxyl cobalt salt formed in the single side | surface of a polyimide resin film, and forms a cobalt film in the single side | surface of a polyimide resin film.
(E) A cobalt film growth step of growing a cobalt film by repeating the steps (c) and (d) a plurality of times.
(F) Mixed ion adsorption in which the surface of one side of the cobalt film is brought into contact with a solution containing nickel ions and cobalt ions to adsorb the nickel component and the cobalt component to form a carboxyl nickel salt and a carboxyl cobalt salt on the cobalt film surface. Process.
(G) A nickel-cobalt film forming step of forming a nickel-cobalt film on the cobalt film by reducing carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film.
(H) A cobalt film growth step in which the step (f) and the step (g) are repeated a plurality of times to grow a cobalt film.
(I) A copper layer forming step of forming a copper layer for forming a circuit on the surface of the nickel-cobalt film on one side using an electrochemical method.
(J) A drying step of drying the single-sided two-layer flexible copper-clad laminate obtained as described above in a reduced pressure atmosphere at 80 ° C. to 160 ° C. for 10 minutes to 80 minutes.

  And the method of manufacturing the double-sided two-layer flexible copper clad laminated board which concerns on this invention comprises the process of (a)-(j) described below, It is characterized by the above-mentioned.

(A) A ring-opening step in which both sides of the polyimide resin film are alkali-treated to open the imide ring to form carboxyl groups on the surface.
(B) The neutralization process which neutralizes the carboxyl group formed on both surfaces by ring-opening using an acid solution.
(C) The cobalt ion adsorption process which forms the carboxyl cobalt salt on both surfaces of a polyimide resin film by making the carboxyl group and cobalt ion containing solution which were neutralized both surfaces contact, and making a cobalt component adsorb | suck.
(D) The cobalt film formation process which reduces the carboxyl cobalt salt formed on both surfaces of the polyimide resin film, and forms a cobalt film on both surfaces of the polyimide resin film.
(E) A cobalt film growth step of growing a cobalt film by repeating the steps (c) and (d) a plurality of times.
(F) Mixed ion adsorption in which the surfaces of the cobalt films on both sides are brought into contact with a solution containing nickel ions and cobalt ions to adsorb the nickel component and the cobalt component to form a carboxyl nickel salt and a carboxyl cobalt salt on the cobalt film surface. Process.
(G) A nickel-cobalt film forming step of forming a nickel-cobalt film on the cobalt film by reducing carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film.
(H) A cobalt film growth step in which the step (f) and the step (g) are repeated a plurality of times to grow a cobalt film.
(I) A copper layer forming step of forming a copper layer for forming a circuit on the surfaces of the nickel-cobalt films on both sides using an electrochemical method.
(J) A drying step of drying the double-sided two-layer flexible copper-clad laminate obtained as described above in a reduced pressure atmosphere at 80 ° C. to 160 ° C. for 10 minutes to 80 minutes.

  The two-layer flexible copper-clad laminate obtained by the direct metallization method according to the present invention is composed of a cobalt film having excellent adhesion to a polyimide resin and a nickel-cobalt film having excellent corrosion resistance. The circuit has excellent peel strength after heating and chemical resistance, and can be easily removed with a copper etchant.

  Moreover, the manufacturing method of the said 2 layer flexible copper clad laminated board is a manufacturing method with few quality variations, in order to manufacture the 2 layer flexible copper clad laminated board which concerns on this invention, and industrially favorable production It is possible to secure a yield.

(Embodiment)
The embodiment regarding the manufacturing method of the 2 layer flexible copper clad laminated board described above is described. Regarding this manufacturing method, it can be divided into “a method for manufacturing a single-sided two-layer flexible copper-clad laminate according to the present invention” and “a method for manufacturing a double-sided two-layer flexible copper-clad laminate according to the present invention”. I can do it. However, the only difference is whether the conductor layer is formed on one side of the polyimide resin film or the conductor layer is formed on both sides, and there is no fundamental difference between the two manufacturing methods. In other words, the following processes (a) to (i) are performed only on one side or both sides. Therefore, the method for producing a single-sided two-layer flexible copper clad laminate will be mainly described, and each step will be described.

  The manufacturing method of this flexible printed wiring board is a single-sided two-layer flexible copper-clad laminate or a double-sided two-layer flexible copper-clad laminate (both above and below) composed of a conductor layer and a polyimide resin film layer using a so-called direct metallization method. Or simply referred to as “two-layer substrate”). Hereafter, each process of the manufacturing method which concerns on this invention is demonstrated later on.

Step (a): In the direct metallization method, the surface of the polyimide resin film must necessarily be subjected to a ring-opening treatment in order to form a conductor layer. Therefore, the first step (a) is a ring-opening step of forming a carboxyl group on the surface by alkali-treating the polyimide resin film to open the imide ring. The polyimide resin film referred to here is assumed to be a commercially available product type Kapton film (manufactured by Toray DuPont Co., Ltd.) such as H type and EN type. This is because these are excellent in wettability with an alkaline solution and easy to perform ring-opening treatment. However, even when using the brand names Kapton V type (made by Toray DuPont Co., Ltd.) and Upilex S (made by Ube Industries Co., Ltd.) having moisture absorption resistance, etc., by adjusting the concentration of the alkaline solution used for ring opening, Similar effects can be obtained. In addition, by coating one side of these polyimide resin films with the above-mentioned water-resistant film in advance, even when exposed to a solution in the direct metallization process described below, water absorption and moisture absorption from the coated surface can be achieved. Thus, it is possible to obtain a single-sided two-layer flexible copper-clad laminate (a schematic cross-sectional view is shown in FIG. 5) having a high and stable peel strength after heating. This water-resistant film is finally peeled off and removed.

  The alkali treatment is performed by a technique such as immersing a polyimide resin film in an alkali solution or spraying an alkali solution on the surface of the polyimide resin film. The solution used for the alkali treatment is preferably a potassium hydroxide solution or a sodium hydroxide solution. This is because neutralization to be performed later is easy and there is little residue on the surface.

  The higher the concentration of the alkaline solution used here, the easier the ring-opening treatment of the polyimide resin film can be performed in a short time. However, in the production method according to the present invention, a re-ring closing step described later is indispensable, and a ring opening process at a level that makes this ring closing process difficult is impossible. Therefore, it is preferable to employ conditions in which the concentration of the alkaline solution is 3.0 mol / l to 10.0 mol / l, the solution temperature is 20 ° C. to 70 ° C., and the treatment time is 1 minute to 30 minutes. If the alkali treatment conditions that are more severe than these conditions are adopted, the surface of the polyimide resin film causes deterioration of the entire resin more than simply ring opening, and the subsequent re-ring closure cannot be performed satisfactorily. On the other hand, the ring-opening treatment itself cannot be performed satisfactorily under the alkali treatment conditions below the range listed here.

Whether the ring is open or not is determined by using a Fourier transform absorption spectrum analyzer (FT-IR), a 1647 cm ⁻¹ ring-opening amide (C═O) that is not found in a ring-closed polyimide resin. An absorption spectrum, a ring-opening amide (N—H) absorption spectrum appearing in the vicinity of 1554 cm ⁻¹ is observed, and further 1774 cm ⁻¹ (C═O), 1720 cm ⁻¹ (C═O) and 1381 cm ^{− which} are characteristic of the imide ring. ^This is possible by confirming the disappearance of the absorption spectrum of ¹ (C—N—C). Further, the absorption spectrum is believed to be derived from a carboxyl group (COO) is ^{1579cm -1, 1371cm -1,} are observed in the vicinity of 1344cm ^-1. All these spectra can be observed on the polyimide resin film that has been subjected to alkali treatment.

Step (b): When the step (a) is completed, the polyimide resin film subjected to the ring-opening treatment is usually washed with water to enter the neutralization step of the step (b). It is a step of neutralizing a strongly alkalized polyimide resin surface by opening a ring to form a carboxyl group and using an acid solution. Here, hydrochloric acid is preferably used for the solution used for neutralization. This is because the residue on the surface of the polyimide resin can be completely eliminated by performing sufficient water washing after the neutralization treatment. The neutralization conditions used here may be a hydrochloric acid solution concentration of 2.0 mol / l to 6.0 mol / l, a solution temperature of 20 ° C. to 35 ° C., and a treatment time of 30 seconds to 1 minute. When the neutralization is completed, a water washing process is performed.

At the stage of the neutralization is completed, the analysis of the polyimide resin film by FT-IR, ring-opening amide 1647cm ^-1 (C = O) absorption spectrum, the ring-opening amide appearing near 1554cm ^-1 (N-H) The absorption spectrum can be confirmed. The ^{1579cm -1, 1371cm} -1 and 1344cm carboxyl group found at ^-1 (COO) absorption spectrum ^{1711cm -1, 1319cm -1,} shifted to the vicinity of 1296cm ^-1, a structure carboxyl group is COOH type by neutralization It is thought that it became preparation.

Step (c) Step (c) is a cobalt ion adsorption step in which a neutralized carboxyl group and a cobalt ion-containing solution are brought into contact with each other to adsorb a cobalt component to form a carboxyl cobalt salt on the surface of the polyimide resin film. is there. As the cobalt ion-containing solution used here, for example, a cobalt sulfate solution can be used. In this case, the cobalt sulfate solution should have a cobalt concentration of 0.01 mol / l to 1.0 mol / l, a solution temperature of 15 ° C. to 30 ° C., and a treatment time of 1 minute to 20 minutes. it can.

When directly measuring the amount of cobalt ions adsorbed on the polyimide resin film at the stage where step (c) is completed, 5 wt% nitric acid solution is used to dissolve the adsorbed cobalt ions and induce the solution. It is possible to analyze using a coupled plasma emission spectroscopic analyzer (ICP), and it is possible to adsorb cobalt ions of about 30 to 120 mg / m ² (converted thickness: 3 nm to 15 nm) by one adsorption treatment. I was able to confirm.

Step (d) In step (c), cobalt ions are adsorbed to form a carboxyl cobalt salt on the surface of the polyimide resin film and washed with water, and then the carboxyl cobalt salt formed on the surface of the polyimide resin film in step (d) is reduced. Then, a cobalt film is formed on the surface of the polyimide resin film. This is the cobalt film forming step. The reduction at this time is performed by bringing the surface of the polyimide resin film on which the carboxyl cobalt salt is formed into contact with the reducing agent. For example, as disclosed in Patent Document 1, the reducing agent in the case of carboxyl cobalt salt is sodium borohydride, hypophosphorous acid, dimethylamine whose concentration is 0.003 mol / l to 0.05 mol / l. Etc. can be used. These reducing agents for the carboxyl cobalt salt can be arbitrarily selected, and are not particularly limited.

Step (e) The step (e) is a cobalt layer forming step in which the step (c) and the step (d) are repeated a plurality of times to grow a cobalt film. Thus, the thickness of the cobalt film can be adjusted by repeatedly performing the steps (c) and (d). That is, if the steps (c) and (d) are not repeated, the cobalt layer does not grow.

The number of repetitions of step (c) and step (d) is preferably 2 to 6 times depending on the conditions such as the solution concentration and solution temperature used in the step. When the number of repetitions is less than 3, it is impossible to obtain a cobalt layer having a minimum necessary weight thickness (40 mg / m ² ). When the number of repetitions exceeding 6 is adopted, the weight thickness of the cobalt layer rich in reactivity with an acid solution such as an etching solution exceeds 300 mg / m ² , and good chemical resistance performance cannot be obtained.

Step (f): In the step (f), when the formation of the cobalt layer on the surface of the polyimide resin film substrate is completed as described above, a nickel-cobalt film is formed on the surface of the cobalt film. This is a mixed ion adsorption process in which the surface of the cobalt film is brought into contact with a solution containing nickel ions and cobalt ions to adsorb nickel ions and cobalt ions to form carboxyl nickel salt and carboxyl cobalt salt on the cobalt film surface.

  As the solution containing nickel ions and cobalt ions, for example, a mixed solution of a cobalt sulfate solution and a nickel sulfate solution can be used. In this case, the cobalt sulfate solution has a cobalt concentration of 0.01 mol / l to 1.0 mol / l, the nickel sulfate solution has a nickel concentration of 0.05 mol / l to 1.0 mol / l, and the solution temperature is 15 ° C. to 30 ° C. The thing of 1 degreeC can be employ | adopted for the processing time for 1 minute-20 minutes.

Step (g): Step (g) is a nickel-cobalt film forming step of forming a nickel-cobalt film on the cobalt film by reducing carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film. . For the reduction at this time, the same reduction method as that used when forming the cobalt film is used. Therefore, the duplicate description here is omitted.

Step (h): Step (h) is a nickel-cobalt film growth step in which the step (f) and the step (g) are repeated a plurality of times to grow a nickel-cobalt film. Thus, the thickness of the nickel-cobalt film can be adjusted by repeatedly performing the step (f) and the step (g).

The number of repetitions of step (f) and step (g) is preferably 3 to 7 times depending on the conditions such as the solution concentration and solution temperature used in the step. If the number of repetitions is less than 3, it is impossible to obtain a nickel-cobalt layer having a minimum weight thickness (380 mg / m ² ) necessary for improving chemical resistance. And if the number of repetitions exceeding 7 times is adopted, the weight thickness of the nickel-cobalt layer exceeds 750 mg / m ² and good chemical resistance performance cannot be obtained. As described above, a seed layer in which a cobalt film and a nickel-cobalt film are laminated is obtained.

  After the formation of the nickel-cobalt film, a nickel-based thin film formed by electrodeposition with an average thickness of 10 nm to 700 nm can be provided on the surface of the nickel-cobalt film. It is desirable from the viewpoint of improvement.

When the pure nickel-based thin film is formed by electrolysis, a solution used as a nickel plating solution can be widely used. For example, (i) nickel sulfate 240 g / l, nickel chloride 45 g / l, boric acid 30 g / l, liquid temperature 55 ° C., pH 5, current density 0.2-10 A / dm ² watt bath conditions, (ii) sulfamic acid Nickel 400 g / l, boric acid 30 g / l, liquid temperature 55 ° C., pH 4.5, current density 0.2-10 A / dm ² sulfamic acid bath conditions, (iii) nickel concentration using nickel sulfate is 5-30 g / l, potassium pyrophosphate 50 to 500 g / l, liquid temperature 20 to 50 ° C., pH 8 to 11 and current density 0.2 to 10 A / dm ² . Among these, in terms of compatibility with the nickel-cobalt film, it is preferable to employ a sulfamic acid bath. This is because, since the precipitated crystals are dense, a film having a uniform film thickness and excellent adhesion can be obtained. The “pure nickel thin film” as used in the present specification is used in the sense that no intentional alloying element is added, and means that it is 100% pure excluding inevitable impurities. Make it clear that it was not used.

When forming a zinc-nickel alloy thin film by electrolysis, for example, nickel sulfate is used and the nickel concentration is 1 to 2.5 g / l, and zinc pyrophosphate is used and the zinc concentration is 0.1 to 1 g / l. The conditions of 50 to 500 g / l, liquid temperature of 20 to 50 ° C., pH of 8 to 11, and current density of 0.2 to 10 A / dm ² are adopted.

When the nickel-cobalt alloy thin film is formed by electrolysis, for example, cobalt sulfate 80 to 180 g / l, nickel sulfate 80 to 120 g / l, boric acid 20 to 40 g / l, potassium chloride 10 to 15 g / l, phosphoric acid 2 Conditions such as sodium hydride 0.1-15 g / l, liquid temperature 30-50 ° C., pH 3.5-4.5, current density 0.2-10 A / dm ² are adopted.

Further, nickel-phosphorus alloy plating can be used by using a phosphoric acid-based solution. In this case, nickel sulfate 120-180 g / l, nickel chloride 35-55 g / l, H ₃ PO ₄ 30-50 g / l, H ₃ PO ₃ 20-40 g / l, liquid temperature 70-95 ° C., pH 0.5- The conditions of 1.5 and current density of 0.2 to 10 A / dm ² are adopted.

Step (i): Step (i) is a copper layer forming step for forming a copper layer for forming a circuit using an electrochemical method on the surface of the seed layer formed as described above. . Here, “using an electrochemical method” may be performed by electroless copper plating using a difference in ionization tendency, electrolytic copper plating, or a combination of electroless copper plating and electrolytic copper plating. This means that as a result, copper is deposited and a copper layer is grown to increase the thickness and to obtain a copper layer at a level capable of forming a circuit. The electroless copper plating bath used here, the composition of the electrolytic copper plating bath, and other plating conditions are not particularly limited. Any condition can be selected and used. At this stage, the formation of the conductor layer is completed.

Step (j): In the step (j), the single-sided two-layer flexible copper-clad laminate or the double-sided two-layer flexible copper-clad laminate obtained as described above is finally thoroughly washed, and 80 ° C to 160 ° C. It is a drying process in which drying is performed for 10 minutes to 80 minutes in a reduced pressure atmosphere of ° C. Here, drying in a general air atmosphere or vacuum drying may be employed. The reduced pressure atmosphere in the case of adopting vacuum drying is a low vacuum atmosphere of 2 hPa level. By adopting such a drying atmosphere, moisture and absorbed moisture adhered to the obtained two-layer flexible copper-clad laminate. Is fully discharged. It is preferable that the drying temperature is 80 ° C. to 160 ° C. as a temperature range in which moisture can be sufficiently removed without applying excessive thermal addition to the polyimide resin film.

  Here, a heating method for measuring the peel strength after heating will be described. Using the two-layer flexible copper-clad laminate obtained as described above, a two-layer flexible printed wiring board in which a 0.2 mm wide linear circuit capable of peeling strength measurement is formed on the copper layer is obtained. This is subjected to heat treatment. In this heat treatment, heating at a temperature of 150 ° C. is performed in an air atmosphere for 168 hours. The heating means can be heated in a furnace having a heating atmosphere of 150 ° C., or blast heating in which hot air having a temperature of 150 ° C. is blown can be employed. However, the blast heating method is more severe because the temperature rise of the two-layer flexible printed wiring board is more rapid. Therefore, in order to maintain good quality under more severe conditions, the present specification adopts a blast heating system.

  Hereinafter, a two-layer flexible copper-clad laminate was manufactured using the manufacturing method according to the present invention, a test circuit for measuring the peel strength was formed by etching, and the peel strength and hydrochloric acid resistance performance were measured after heating. Examples will be described.

  In this example, a single-sided two-layer flexible copper-clad laminate was manufactured using a 38 μm-thick polyimide resin film as a base material and using the manufacturing method according to the present invention. And the flexible printed wiring board for the measurement of the peeling strength after heating and hydrochloric acid resistance performance was manufactured using this single-sided two-layer flexible copper clad laminated board, and the peeling strength was measured after the heating. Hereafter, each process is demonstrated in order.

Step (a) : First, the polyimide resin film was alkali-treated to open an imide ring and form a carboxyl group on the surface. As the type of the polyimide resin film used here, trade name Kapton 150EN (Toray DuPont Co., Ltd.) was used.

  The alkali treatment in the step (a) was performed by spraying a solution having a potassium hydroxide concentration of 5.0 mol / l and a solution temperature of 60 ° C. on one side of the polyimide resin film for 5 minutes. When the alkali treatment was completed, the substrate was sufficiently washed with water, and the alkali solution adhered from the surface of the polyimide resin film was removed.

In the FT-IR analysis performed to determine whether or not the ring is open, a ring-opening amide (C═O) absorption spectrum of 1647 cm ⁻¹ , which is not found in the ring-closed polyimide resin, 1554 cm ^−1. A ring-opening amide (N—H) absorption spectrum appearing in the vicinity is observed, and 1774 cm ⁻¹ (C═O), 1720 cm ⁻¹ (C═O) and 1381 cm ⁻¹ (C—N—) characteristic of the imide ring. The disappearance of the absorption spectrum of C) was confirmed. Further, the absorption spectrum is believed to be derived from a carboxyl group (COO) is ^{1579cm -1, 1371cm -1,} which is observed in the vicinity of 1344cm ^-1.

Step (b): Next, the polyimide resin film that had been subjected to the ring-opening step in step (b) and washed with water was treated in a neutralization step. The polyimide resin film which was ring-opened to form a carboxyl group and was strongly alkalized was immersed in an acid solution for neutralization. Here, the solution used for neutralization was a hydrochloric acid solution, and the concentration of the hydrochloric acid solution was 6.0 mol / l, the solution temperature was 25 ° C., and the treatment time was 30 seconds. And when neutralization was complete | finished, the water washing process was performed.

At the stage of the neutralization is completed, the analysis of the polyimide resin film by FT-IR, ring-opening amide 1647cm ^-1 (C = O) absorption spectrum, the ring-opening amide appearing near 1554cm ^-1 (N-H) An absorption spectrum was confirmed. The ^{1579cm -1, 1371cm} -1 and 1344cm carboxyl group found at ^-1 (COO) absorption spectrum ^{1711cm -1, 1319cm -1,} was shifted to the vicinity of 1296cm ^-1.

Step (c): When the neutralization step is completed, the neutralized carboxyl group of the polyimide resin film is brought into contact with the cobalt-containing ion solution in the cobalt ion adsorption step of step (c), and cobalt ions are adsorbed on the carboxyl group. Carboxyl cobalt salts were formed on both sides of the polyimide resin film. The cobalt-containing ion solution used here was a cobalt sulfate solution having a concentration of 0.05 mol / l, the solution temperature was 25 ° C., and was immersed in this solution for 15 minutes. And it washed with water and the cobalt sulfate solution which remained on the surface of the polyimide resin film was removed.

Step (d): Subsequently, in the cobalt film forming step of step (d), the carboxyl cobalt salt formed on the polyimide resin film surface in the cobalt ion adsorption step was reduced to form a cobalt film on the surface of the polyimide resin film. . The reduction in this example is performed by immersing a polyimide resin film in which a carboxyl cobalt salt is formed in a sodium borohydride solution having a concentration of 0.01 mol / l and a solution temperature of 25 ° C. for 5 minutes, and then contacting with a reducing agent. went. And the reducing agent adhering from the surface was removed by washing with water.

Step (e): In the cobalt layer growth step of step (e), step (c) and step (d) are further repeated a predetermined number of times as shown in Table 1 to grow a cobalt film.

Step (f): In the mixed ion adsorption step of step (f), the nickel-cobalt film is formed on the surface of the cobalt film obtained as described above. Then, nickel ion and cobalt ion were adsorbed by contacting with a solution containing carboxy nickel salt and carboxy cobalt salt on the cobalt film surface. The cobalt-containing ion solution used here employs a solution in which a cobalt sulfate solution having a concentration of 0.0025 mol / l and a nickel sulfate solution having a nickel concentration of 0.0475 mol / l are mixed, and the solution temperature is 25 ° C. It was immersed in this solution for 15 minutes. And it washed with water and removed the mixed solution which remained on the surface of the polyimide resin film.

Step (g): In the nickel-cobalt film forming step of step (g), nickel that forms a nickel-cobalt film on the cobalt film by reducing the carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film. -Cobalt film formation step. For the reduction at this time, the same reduction method as that used when forming the cobalt film in the step (d) was used.

Step (h): In the nickel-cobalt film growth step of step (h), the step (f) and the step (g) were repeated a plurality of times to grow a nickel-cobalt film. In this way, the thickness of the nickel-cobalt film was adjusted by repeating the steps (f) and (g) a predetermined number of times shown in Table 1.

Step (i): Then, in the copper layer forming step of step (i), a copper component was electrodeposited on the surface of the seed layer using an electrolytic method, and the copper thin film was plated up to a copper layer having a thickness of 18 μm. . The solution used for the electrolysis here was a copper sulfate solution having a concentration of 150 g / l sulfuric acid, 65 g / l copper, and a liquid temperature of 45 ° C. A DSE plate, which is an insoluble anode, was placed on the counter electrode during electrolysis, and electrolysis was performed under smooth plating conditions with a current density of 3 A / dm ² . When the plating up was completed, the copper sulfate solution adhered by washing with water was removed.

Step (j): In the drying step of step (j), the single-sided, two-layer flexible copper clad laminate obtained as described above is finally thoroughly washed, and the pressure is reduced to 60 ° C. in a reduced pressure atmosphere of 2 hPa level at 150 ° C. It was dried for a minute, and the moisture and absorbed moisture adhering to the obtained single-sided two-layer flexible copper-clad laminate were sufficiently removed to obtain the final single-sided two-layer flexible copper-clad laminate. In this example, the number of repetitions of step (e) and step (h) was changed, and a plurality of single-sided two-layer flexible copper-clad laminates according to the present invention were manufactured. These products are listed in Table 1 as Example 1a, Example 1b, Example 1c, Example 1d, and Example 1e.

  An etching resist layer was formed on the surface of the copper layer of the single-sided two-layer flexible copper-clad laminate obtained by the above direct metallization method, exposed, developed, and etched with a copper chloride-based etching solution. As a result, there was no problem in etching, and no etching residue was confirmed. And the single-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured.

  The single-sided two-layer flexible printed wiring board after circuit etching is sufficiently dried and immediately measured for normal peel strength. After that, hot air at 150 ° C. is applied in a single-layer two-layer flexible printed wiring in an atmospheric furnace. The plate was blasted, heated for 168 hours, and then peeled off after heating. The hydrochloric acid resistance deterioration rate was determined by preparing a sample for measuring the peel strength, measuring the normal peel strength measured immediately, and mixing the sample with hydrochloric acid: water = 1: 1 at room temperature. The peel strength after treatment with hydrochloric acid soaked for 1 hour (hereinafter simply referred to as “peel strength after treatment with hydrochloric acid”) is measured to indicate the degree of degradation. ] = ([Normal peel strength] − [Peel strength after treatment with hydrochloric acid]) / [Normal peel strength]. Therefore, the smaller the deterioration rate, the better the chemical resistance.

  In this example, the same polyimide resin film as used in the production of the single-sided two-layer flexible copper-clad laminate of Example 1 was used, which was obtained by pasting together a PET film, which is a water-resistant film, using an adhesive adhesive. However, since the manufacturing process itself is the same as that of Example 1, detailed description regarding the manufacturing method is omitted.

  Thereafter, in the same manner as in Example 1, an etching resist layer was formed on the surface of the copper layer of the single-sided two-layer flexible copper-clad laminate, exposed, developed, and etched with a copper chloride etching solution. As a result, there was no problem in etching, and no etching residue was confirmed. And the single-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured. In the same manner as in Example 1, the peel strength after heating and the hydrochloric acid resistance deterioration rate were measured. These results are shown in Table 1 so that they can be compared with the examples.

  While Example 1 and Example 2 produced a single-sided two-layer flexible copper-clad laminate, this example produced a double-sided two-layer flexible copper-clad laminate. The manufacturing method at this time is basically the same as that of the first embodiment. Therefore, only the different parts will be described with respect to the manufacturing method.

Step (a) The polyimide resin film was alkali-treated to open an imide ring and form a carboxyl group on the surface. The polyimide resin film used here was the same as in Example 1, and the solution used for the alkali treatment was also the same, and the ring-opened state similar to that in Example 1 was obtained. However, in this example, since both sides of the polyimide resin film need to be ring-opened, the treatment was performed by immersing the polyimide resin film in the alkaline treatment solution for 10 minutes. When the alkali treatment was completed, the substrate was sufficiently washed with water, and the alkali solution adhered from the surface of the polyimide resin film was removed.

Step (b) to step (e): Step (b) to step (h) are the same as in Example 1. However, the neutralization operation of the step (b), the cobalt ion adsorption step of the step (c), the cobalt film formation step of the step (d), and the cobalt film growth step of the step (e) are the steps (c) and ( d) was repeated three more times to form cobalt films on both sides of the polyimide resin film.

Step (f) to Step (h): The steps (f) to (h) are the same as those in Example 1. However, the nickel-cobalt ion adsorption step in step (f), the nickel-cobalt film formation step in step (g), and the nickel-cobalt film growth step in step (h) are the same as steps (f) and (g). Was further repeated 4 times to form a nickel-cobalt film on both sides of the polyimide resin film.

  Hereinafter, the double-sided two-layer flexible copper clad laminate according to the present invention was obtained through the step (i) (copper layer forming step) and the step (j) (drying step) as in Example 1.

  An etching resist layer was formed on the surfaces of the copper layers on both sides of the double-sided two-layer flexible copper-clad laminate obtained as described above, exposed, developed, and etched with a copper chloride etching solution. As a result, there was no problem in etching, and no etching residue was confirmed. And the double-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured. Then, in the same manner as in Example 1, the peel strength after heating on both surfaces (first surface and second surface) and the hydrochloric acid resistance deterioration rate were measured. These results are shown in Table 1 so that they can be compared with the comparative examples.

Comparative example

[Comparative Example 1]
In Comparative Example 1, a single-sided two-layer flexible printed wiring board having only a cobalt film as a seed layer was manufactured based on the manufacturing method of Example 1, and used for comparison with the Example. Therefore, only the different parts will be described with respect to the manufacturing method. Step (a) to step (d) are the same as those in the first embodiment, and thus description thereof will be omitted.

Step (e): In the cobalt layer growth step of step (e), step (c) and step (d) are repeated eight more times to grow a cobalt film. And the process (f)-the process (h) of Example 1 were abbreviate | omitted, and it progressed to the process (i).

Step (i): Then, in the copper layer forming step of step (i), a copper component is electrodeposited on the surface of the seed layer of only the cobalt film using an electrolytic method, and the copper thin film becomes a copper layer having a thickness of 18 μm. Plated up to. The solution used for the electrolysis here was a copper sulfate solution having a concentration of 150 g / l sulfuric acid, 65 g / l copper, and a liquid temperature of 45 ° C. A DSE plate, which is an insoluble anode, was placed on the counter electrode during electrolysis, and electrolysis was performed under smooth plating conditions with a current density of 3 A / dm ² . When the plating up was completed, the copper sulfate solution adhered by washing with water was removed.

Step (j): Then, drying is performed in the same manner as in Step (j) of Example 1, and moisture and absorbed moisture adhering to the obtained single-sided two-layer flexible copper-clad laminate are sufficiently removed. This is a single-sided two-layer flexible copper-clad laminate.

  Thereafter, in the same manner as in Example 1, an etching resist layer was formed on the surface of the copper layer of the single-sided two-layer flexible copper-clad laminate, exposed, developed, and etched with a copper chloride etching solution. As a result, there was no problem in etching, and no etching residue was confirmed. And the single-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured. In the same manner as in Example 1, the peel strength after heating and the hydrochloric acid resistance deterioration rate were measured. These results are shown in Table 1 so that they can be compared with the examples.

[Comparative Example 2]
In Comparative Example 2, a single-sided two-layer flexible printed wiring board having only a nickel-cobalt film as a seed layer was manufactured based on the manufacturing method of Example 1, and used for comparison with the Example. Therefore, only the different parts will be described with respect to the manufacturing method. Step (a) and step (b) are the same as those in Example 1, and thus the description thereof will be omitted.

  In Comparative Example 2, when the step (b) was completed, the steps (c) to (e) of Example 1 were omitted, and a manufacturing method jumping to the step (f) was adopted.

Step (f): When the neutralization step of step (b) is completed, the neutralized carboxyl group of the polyimide resin film is brought into contact with a solution containing nickel ions and cobalt ions to adsorb nickel ions and cobalt ions, and carboxyl nickel A salt and a carboxy cobalt salt were formed on the surface. The cobalt-containing ion solution used here employs a solution in which a cobalt sulfate solution having a concentration of 0.025 mol / l and a nickel sulfate solution having a nickel concentration of 0.0475 mol / l are mixed, and the solution temperature is 25 ° C. It was immersed in this solution for 15 minutes. And it washed with water and removed the mixed solution which remained on the surface of the polyimide resin film.

Step (g): Subsequently, in the nickel-cobalt film forming step of step (f), the carboxyl cobalt salt formed on the surface of the polyimide resin film was reduced to form a nickel-cobalt film on the surface of the polyimide resin film. The reduction in this example is performed by immersing a polyimide resin film in which a carboxyl nickel salt and a carboxyl cobalt salt are formed in a sodium borohydride solution having a concentration of 0.01 mol / l and a solution temperature of 25 ° C. It was performed by contacting with. And the reducing agent adhering from the surface was removed by washing with water.

Step (h): In the nickel-cobalt film growth step of step (h), the step (f) and the step (g) were repeated nine times to grow a nickel-cobalt film.

Step (i): In the copper layer forming step of step (i), a copper component is electrodeposited on the surface of the seed layer of only the nickel-cobalt film by using an electrolytic method, and the copper thin film is formed into a 18 μm thick copper layer Plated up until The solution used for the electrolysis here was a copper sulfate solution having a concentration of 150 g / l sulfuric acid, 65 g / l copper, and a liquid temperature of 45 ° C. A DSE plate, which is an insoluble anode, was placed on the counter electrode during electrolysis, and electrolysis was performed under smooth plating conditions with a current density of 3 A / dm ² . When the plating up was completed, the copper sulfate solution adhered by washing with water was removed.

Step (j): Then, drying is performed in the same manner as in Step (j) of Example 1, and moisture and absorbed moisture adhering to the obtained single-sided two-layer flexible copper clad laminate are sufficiently removed. This is a single-sided two-layer flexible copper-clad laminate.

  Thereafter, in the same manner as in Example 1, an etching resist layer was formed on the surface of the copper layer of the single-sided two-layer flexible copper-clad laminate, exposed, developed, and etched with a copper chloride etching solution. As a result, there was no problem in etching, and no etching residue was confirmed. And the single-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured. In the same manner as in Example 1, the peel strength after heating and the hydrochloric acid resistance deterioration rate were measured. These results are shown in Table 1 so that they can be compared with the examples.

[Comparative Example 3]
In Comparative Example 3, a single-sided two-layer flexible printed wiring board having only a nickel film as a seed layer was manufactured based on the manufacturing method of Example 1, and used for comparison with the Example. Therefore, only the different parts will be described with respect to the manufacturing method. Step (a) and step (b) are the same as those in Example 1, and thus the description thereof will be omitted.

  In Comparative Example 3, when the step (b) was completed, the steps (c) to (e) of Example 1 were omitted, and a manufacturing method that skipped to the step (f) was adopted.

Step (f): When the neutralization step of step (b) is completed, the neutralized carboxyl group of the polyimide resin film is brought into contact with a solution containing nickel ions to adsorb nickel ions to form a carboxyl nickel salt on the surface. . The nickel ion solution used here was a nickel sulfate solution having a nickel concentration of 0.05 mol / l, the solution temperature was 25 ° C., and the solution was immersed in this solution for 15 minutes. And it washed with water and removed the mixed solution which remained on the surface of the polyimide resin film.

Step (g): Subsequently, as the nickel film forming step of step (f), the carboxyl nickel salt formed on the surface of the polyimide resin film was reduced to form a nickel film on the surface of the polyimide resin film. The reduction in this example is performed by immersing a polyimide resin film in which a carboxyl nickel salt is formed in a sodium borohydride solution having a concentration of 0.01 mol / l and a solution temperature of 25 ° C. for 5 minutes and then contacting with a reducing agent. went. And the reducing agent adhering from the surface was removed by washing with water.

Step (h): In the nickel film growth step of step (h), the steps (f) and (g) were repeated nine times to grow a nickel film.

Step (i): Then, in the copper layer forming step of step (i), a copper component is electrodeposited on the surface of the seed layer of only the nickel film using an electrolytic method, and the copper thin film becomes a copper layer having a thickness of 18 μm. Plated up to. The solution used for the electrolysis here was a copper sulfate solution having a concentration of 150 g / l sulfuric acid, 65 g / l copper, and a liquid temperature of 45 ° C. A DSE plate, which is an insoluble anode, was placed on the counter electrode during electrolysis, and electrolysis was performed under smooth plating conditions with a current density of 3 A / dm ² . When the plating up was completed, the copper sulfate solution adhered by washing with water was removed.

Step (j): Then, drying is performed in the same manner as in Step (j) of Example 1, and moisture and absorbed moisture adhering to the obtained single-sided two-layer flexible copper-clad laminate are sufficiently removed. This is a single-sided two-layer flexible copper-clad laminate.

  Thereafter, in the same manner as in Example 1, an etching resist layer was formed on the surface of the copper layer of the single-sided two-layer flexible copper-clad laminate, exposed, developed, and etched with a copper chloride etching solution. As a result, the nickel film portion that remained without being dissolved by the etching solution was confirmed as an etching residue. And the single-sided two-layer flexible printed wiring board provided with the 0.2 mm width circuit for peeling strength measurement was manufactured. In the same manner as in Example 1, the peel strength after heating and the hydrochloric acid resistance deterioration rate were measured. These results are shown in Table 1 so that they can be compared with the examples.

[Contrast between Example and Comparative Example]
In each of the above Examples, the normal peel strength is over 0.90 kgf / cm, the peel strength after heating is over 0.40 kgf / cm, and the hydrochloric acid resistance deterioration rate is 7.0% or less. A good value is shown, and a good result is obtained in the etching performance. In particular, Example 2 shows that the effect of preventing moisture absorption of the polyimide resin base material in the processing process using the water resistant film is clearly reflected.

  On the other hand, Comparative Example 1 in which the seed layer is composed of only a cobalt film shows a good value in the normal peel strength and the peel strength after heating, and the etching performance is also good. It can be seen that the acid degradation rate is very low at 22.0%.

  In Comparative Example 2 in which the seed layer was composed of only a nickel-cobalt film, the normal peel strength and the hydrochloric acid resistance deterioration rate showed good values and the etching performance was good, but the post-heating pulling was good. It can be seen that the peel strength is as extremely low as 0.11 kgf / cm.

  Further, Comparative Example 3 in which the seed layer is composed only of a nickel film shows good values for normal peel strength, peel strength after heating, and hydrochloric acid resistance deterioration rate, but there is a problem in etching performance. It can be understood that the product is difficult to be used in actual industrial use due to etching residue. The confirmation of the etching residue was judged by whether or not there was a portion through which light was not transmitted with an optical microscope by applying transmitted light from below to the polyimide resin substrate after copper etching.

  The two-layer flexible copper-clad laminate obtained by the direct metallization method according to the present invention is composed of a cobalt film having excellent adhesion to a polyimide resin and a nickel-cobalt film having excellent corrosion resistance. The circuit has excellent peel strength after heating and chemical resistance, and can be easily removed with a copper etchant. Therefore, the two-layer flexible printed wiring boards such as TAB and COF obtained from the two-layer flexible copper-clad laminate according to the present invention effectively prevent the copper circuit from peeling due to heat shock during component mounting. As a result, the quality and reliability of the flexible printed wiring board can be dramatically improved.

The schematic cross section of a single-sided two-layer flexible copper clad laminate. The schematic cross section of a double-sided two-layer flexible copper clad laminated board. A transmission electron microscope image showing the bonding state at each interface of polyimide resin film substrate / cobalt thin film / nickel-cobalt film / copper layer. The schematic diagram for demonstrating the chemical-resistant deterioration mechanism of peeling strength. The schematic cross section of the single-sided two-layer flexible copper clad laminated board provided with the water-resistant film layer on the one surface side.

Explanation of symbols

F Polyimide resin film R Polyimide resin 1a Single-sided two-layer flexible copper-clad laminate 1b Double-sided two-layer flexible copper-clad laminate 2 Conductor layer 3 Seed layer 4 Cobalt layer 5 Cobalt particles (including cobalt oxide particles)
6 Nickel-cobalt film 7 Copper layer 8 Water-resistant film 9 Circuit

Claims (5)

In a two-layer flexible copper-clad laminate obtained by a direct metallization method in which a seed layer is formed on one side of a polyimide resin film substrate and a copper layer is formed on the seed layer,
The seed layer is a single-sided two-layer flexible copper-clad laminate in which a cobalt layer in contact with a polyimide resin film substrate and a nickel-cobalt film are in a laminated state. The single-sided two-layer flexible copper-clad laminate is a single-sided two-layer flexible copper-clad laminate according to claim 1, wherein the other side where the copper layer is present is coated with a water-resistant film. In a double-sided two-layer flexible copper-clad laminate obtained by a direct metallization method in which a seed layer is formed on both sides of a polyimide resin film substrate and a copper layer is formed on each seed layer,
Each double-sided flexible copper-clad laminate is characterized in that each seed layer on both sides is in a laminated state of a cobalt layer in contact with a polyimide resin film substrate and a nickel-cobalt film. A method for producing a single-sided, two-layer flexible copper-clad laminate according to claim 1 or 2,
The manufacturing method of the single-sided two-layer flexible copper clad laminated board characterized by providing the process of (a)-(j) described below.
(A) A ring-opening step of forming an carboxyl group on the surface by alkali-treating the exposed surface of the polyimide resin film having one surface or one surface of the polyimide resin film covered with a water-resistant film to open the imide ring.
(B) A neutralization step of neutralizing a carboxyl group formed on one side by ring opening using an acid solution.
(C) A cobalt ion adsorption step of forming a carboxyl cobalt salt on one side of a polyimide resin film by bringing a neutralized carboxyl group on one side into contact with a cobalt ion-containing solution to adsorb a cobalt component.
(D) The cobalt film formation process which reduces the carboxyl cobalt salt formed in the single side | surface of a polyimide resin film, and forms a cobalt film in the single side | surface of a polyimide resin film.
(E) A cobalt film growth step of growing a cobalt film by repeating the steps (c) and (d) a plurality of times.
(F) Mixed ion adsorption in which the surface of one side of the cobalt film is brought into contact with a solution containing nickel ions and cobalt ions to adsorb the nickel component and the cobalt component to form a carboxyl nickel salt and a carboxyl cobalt salt on the cobalt film surface. Process.
(G) A nickel-cobalt film forming step of forming a nickel-cobalt film on the cobalt film by reducing carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film.
(H) A nickel-cobalt film growth step in which the step (f) and the step (g) are repeated a plurality of times to grow a nickel-cobalt film.
(I) A copper layer forming step of forming a copper layer for forming a circuit on the surface of the nickel-cobalt film on one side using an electrochemical method.
(J) A drying step of drying the single-sided two-layer flexible copper-clad laminate obtained as described above in a reduced pressure atmosphere at 80 ° C. to 160 ° C. for 10 minutes to 80 minutes. A method for producing a double-sided, two-layer flexible copper-clad laminate according to claim 3,
The manufacturing method of the double-sided two-layer flexible copper clad laminated board characterized by providing the process of (a)-(j) described below.
(A) A ring-opening step in which both sides of the polyimide resin film are alkali-treated to open the imide ring to form carboxyl groups on the surface.
(B) The neutralization process which neutralizes the carboxyl group formed on both surfaces by ring-opening using an acid solution.
(C) The cobalt ion adsorption process which forms the carboxyl cobalt salt on both surfaces of a polyimide resin film by making the carboxyl group and cobalt ion containing solution which were neutralized both surfaces contact, and making a cobalt component adsorb | suck.
(D) The cobalt film formation process which reduces the carboxyl cobalt salt formed on both surfaces of the polyimide resin film, and forms a cobalt film on both surfaces of the polyimide resin film.
(E) A cobalt film growth step of growing a cobalt film by repeating the steps (c) and (d) a plurality of times.
(F) Mixed ion adsorption in which the surfaces of the cobalt films on both sides are brought into contact with a solution containing nickel ions and cobalt ions to adsorb the nickel component and the cobalt component to form a carboxyl nickel salt and a carboxyl cobalt salt on the cobalt film surface. Process.
(G) A nickel-cobalt film forming step of forming a nickel-cobalt film on the cobalt film by reducing carboxyl nickel salt and carboxyl cobalt salt formed on the surface of the cobalt film.
(H) A nickel-cobalt film growth step in which the step (f) and the step (g) are repeated a plurality of times to grow a nickel-cobalt film.
(I) A copper layer forming step of forming a copper layer for forming a circuit on the surfaces of the nickel-cobalt films on both sides using an electrochemical method.
(J) A drying step of drying the double-sided two-layer flexible copper-clad laminate obtained as described above in a reduced pressure atmosphere at 80 ° C. to 160 ° C. for 10 minutes to 80 minutes.