JP4824828B1 - Composite metal foil, method for producing the same, and printed wiring board - Google Patents

Abstract

The present invention provides a composite metal foil that easily peels off after a heat-compression step even if an acidic plating bath is used, and a residue that hardly remains on a substrate side of a printed wiring board, and a method for producing the same.
SOLUTION: The surface of a carrier 2 made of a metal foil comprises a diffusion prevention layer 3 for preventing metal diffusion to metal atoms constituting the carrier 2 and a metal layer formed by a physical film formation method. It has the peeling layer 4 and the transfer layer 5 formed by the plating method, and the peeling layer 4 and the transfer layer 5 are comprised with the same kind of metal atom.
[Selection] Figure 1

Description

  The present invention relates to a composite metal foil, a method for producing the same, and a printed wiring board.

  2. Description of the Related Art Recently, electronic devices that are required to be reduced in size and improved in processing speed have electronic elements mounted at high density using a multilayer printed wiring board on which fine patterns (fine patterns) are formed.

  As a method of manufacturing a printed wiring board suitable for fine pattern formation, a copper-clad laminate formed by bonding ultra-thin copper foil onto an insulating resin (hereinafter simply referred to as “base material”) is patterned by an etching method or the like. There is a method of forming. However, when the thickness of the copper foil is 12 μm or less, wrinkles and cracks are likely to occur when the copper clad laminate is formed. Therefore, a method for producing a copper clad laminate using a composite metal foil obtained by laminating an ultrathin copper foil on a support (hereinafter referred to as “carrier”) is known.

  In Patent Documents 1 to 3, copper foil is provided on a carrier via various peeling layers such as an inorganic coating containing chromium (Cr) or an organic coating such as a nitrogen-containing compound having a substituent (functional group). A method of forming and separating with this release layer and transferring a copper foil film onto a substrate is disclosed (Patent Documents 1 to 3).

  In Patent Document 4, a metal layer (I) deposited on an interface with a metal carrier on a metal carrier and one or more metal layers formed on the metal layer (I) by vapor deposition or electroplating. A peelable metal foil having a laminated structure consisting of (II) and a method for producing the same are disclosed.

Japanese Patent Publication No.56-34115 JP-A-11-317574 JP 2000-315848 A JP 2009-90570 A

  However, since the “peeling layer” disclosed in Patent Documents 1 to 3 is a member different from the transfer layer, when the ultrathin copper foil is transferred to the substrate, a part of the peeling layer is formed. There was a problem that the residue was easily formed by being transferred to the substrate side. Such peeling layer residue may cause various problems (for example, chromium on the ultrathin copper foil side) in various processes (masking process, etching process, thick plating process, etc.) for forming a circuit pattern on the ultrathin copper foil later. In order to prevent this, a process for removing the residue may be separately required.

  On the other hand, in the “peelable metal foil” disclosed in Patent Document 4, in particular, the metal carrier, the metal layer (I), and the metal layer (II) are all copper, and the metal layer (II) is plated. When an acidic copper plating bath is used, the metal layer (I) diffuses to the metal carrier side in the subsequent heating and compression step, which makes it difficult to peel off. In Example 4 of Patent Document 4, in order to avoid this problem, an example is described in which a plating solution mainly composed of an “aqueous copper cyanide solution” is used as an alkaline copper plating bath. However, since an aqueous copper cyanide solution is harmful to the human body, it is not preferable to use it industrially.

  This invention is made | formed in view of the above, and makes it a main technical subject to provide the composite metal foil and its manufacturing method which are easy to peel after a heating compression process even if it uses an acidic plating bath.

The composite metal foil according to the present invention is formed on the surface of a carrier made of copper foil, and a diffusion prevention layer for preventing diffusion of the metal into the carrier , and a physical film formation method on the diffusion prevention layer a release layer comprising a formed copper by, on the release layer, anda transfer layer formed by plating using an acidic plating bath, plating the diffusion barrier layer comprises a molybdenum or phosphorus or both thereof And an induced eutectoid film deposited from a plating solution comprising a solution and a plating solution in which at least one of nickel and cobalt is selected.
The release layer and the transfer layer are both made of copper and are in direct contact with each other.

  Here, the physical film forming method is specifically a vacuum deposition method, a sputtering method, an ion plating method, or the like. That is, according to the configuration of the above invention, since the diffusion preventing layer is provided, the problem that the metal atoms constituting the transfer layer and the release layer diffuse to the carrier side by the heat compression process and the separation is difficult to occur.

The thickness of the diffusion barrier layer is a ^{0.05mg / m 2 ~1000mg / m 2} , the release layer and the total thickness of the transfer layer is 0.1μm or more, it is preferable to 12μm or less. A similar laminated film may be formed on the back side of the carrier.

The method for producing a composite metal film according to the present invention includes a step of preparing a carrier made of copper foil (S1), and a diffusion prevention layer forming step of forming a diffusion prevention layer on at least one surface of the carrier (S2). When the peeling layer formation process by forming a peeling layer made of copper by physical deposition method on the surface of the diffusion preventing layer (S3), copper by plating using an acidic plating bath to the surface of the release layer And a transfer layer forming step (S4) formed by forming a transfer layer to be configured.

The plating method used in the transfer layer forming step (S4) can use an acidic plating bath. This is because a diffusion preventing layer for preventing metal diffusion is provided between the transfer layer and release layer and the carrier.
The method for producing a composite metal foil according to the present invention includes the diffusion preventing layer forming step (S2) and the peeling layer forming step (S3), and can be peeled even when heated to a temperature range of 250 ° C. It is characterized by.

  A printed wiring board according to the present invention is a copper-clad laminate obtained by laminating the above-described composite metal foil according to the present invention on a substrate for forming a printed wiring board and peeling the carrier with the peeling layer. It is obtained by using.

  According to the composite metal foil according to the present invention, the provision of the diffusion preventing layer causes a problem that the metal atoms constituting the transfer layer and the release layer are diffused to the carrier side by the heat compression process, thereby making the release difficult. Hateful. Moreover, according to the manufacturing method of the composite metal foil obtained by the manufacturing method of this invention, a transfer layer can be formed using an acidic plating bath. Therefore, compared with the case where an alkaline plating bath is used, special equipment is not required, so that manufacturing costs can be suppressed. Moreover, when the composite metal foil obtained in this way is used, even if the heat compression for transferring to the base material side is implemented, the diffusion prevention layer suppresses the diffusion of copper.

It is sectional drawing of the composite metal foil of 1st Embodiment. It is a modification of the composite metal foil of 1st Embodiment. It is process drawing which shows the manufacturing method of the composite metal foil of 2nd Embodiment. (A)-(d) is process sectional drawing corresponding to each step of FIG. It is process drawing which shows the manufacturing method of the copper clad laminated board of 3rd Embodiment. It is sectional drawing which shows the printed wiring board of 4th Embodiment.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. However, each embodiment and each example do not give a limited interpretation in the recognition of the gist of the present invention. The same or similar members are denoted by the same reference numerals, and the description thereof may be omitted.

First Embodiment-Structure of Composite Metal Foil-
FIG. 1 is a schematic cross-sectional view showing an example of a composite metal foil in the present invention. The composite metal foil 1 includes a carrier 2 serving as a support for the laminated film, a diffusion prevention layer 3 formed on the surface of the carrier 2, a release layer 4 formed on the surface of the diffusion prevention layer 3, and a release layer 4. And a transfer layer 5 formed on the surface. The carrier 2 is not particularly limited as long as it has heat resistance within an assumed process temperature and is a member that serves as a support for a laminated film formed on the carrier 2. For example, a metal foil such as a copper foil or a copper alloy foil formed by a rolling method or an electrolytic method can be used.

  When using copper foil as the carrier 2, the thickness of the copper foil is preferably 9 to 300 μm and more preferably 18 to 35 μm from the viewpoint of handling. If the carrier is less than 9 μm, wrinkles and cracks are likely to occur, making it difficult to use as a carrier, and if it exceeds 300 μm, the waist is too strong and difficult to handle.

  The diffusion prevention layer 3 is a film formed on the surface of the carrier 2 and is provided to prevent metal atoms constituting the release layer 4 and the transfer layer 5 from diffusing to the carrier side in a subsequent heat treatment step. Examples of such a material include an induced eutectoid film deposited from a plating solution comprising a plating solution containing molybdenum or phosphorus or both, and a plating solution in which at least one of nickel and cobalt is selected.

The thickness of the diffusion preventing layer is 0.05mg ^{/ m 2} ~1000mg ^/ m 2 is preferred. The reason why the film thickness is shown by the amount of adhesion (mass per unit area) is that the film thickness of the diffusion preventing layer 3 is very thin and it is not easy to measure directly.

When the thickness of the diffusion preventing layer is very thin, a sufficient diffusion preventing function cannot be exhibited. That is, when the printed wiring board is heated and compressed, the metal atoms constituting the release layer 4 and the transfer layer 5 are easily diffused to the carrier 2 side, which makes it difficult to release. In addition, about this thickness, it is good to adjust suitably according to the kind of metal element which forms a diffusion prevention layer. However, exceeding 1000 mg / m ² is not preferable because it leads to an increase in the cost of film formation.

  The release layer 4 is formed by vacuum deposition or sputtering. The thickness of the release layer is preferably 50 to 8000 mm. If it is less than 50 mm, it does not become a film but an island structure, which is not preferable. Moreover, since it will lead to the cost increase of film formation when it exceeds 8000cm, it is not preferable.

  Also, in order to use an acidic plating bath as the transfer layer forming bath, the release layer 4 is dissolved and reacted in the acidic plating bath, and if it is less than 50 mm, it is difficult to maintain the film, which is not preferable.

  The transfer layer 5 is a layer serving as a conductor of a base material constituting the printed wiring board, and a metal having high conductivity may be used. Specifically, copper is preferable.

  The thickness of the transfer layer is preferably within a predetermined range because it affects the fine patterning of the circuit when transferred to the substrate constituting the printed wiring board. This is because a film that is too thin is difficult to form a film, and conversely, if it is too thick, it is difficult to form a fine pattern.

  When the transfer layer was formed of a copper film formed with a copper sulfate plating bath, the range of 0.1 μm to 12 μm, particularly 0.1 μm to 9 μm was a preferable range as a result of the experiment. When the thickness is less than 0.1 μm, it is difficult to form a film, and when it exceeds 12 μm, it is difficult to form a fine pattern.

  However, since a part of the release layer may accompany the transfer layer, care must be taken in adjusting the thickness. Further, the diffusion preventing layer may accompany the release layer, but it is extremely small and does not cause a problem.

  FIG. 2 is a diagram illustrating a modification of the first embodiment. That is, in the case of the composite metal foil of FIG. 1, the laminated film is formed only on one side of the carrier 2, but FIG. 2 is an example in which the same laminated film is formed on both sides of the carrier 2.

(2nd Embodiment)-Manufacturing method of composite metal foil-
Next, as a second embodiment, a method for manufacturing the composite metal foil described in the first embodiment will be described.
FIG. 3 is a diagram illustrating a procedure of the method for manufacturing the composite metal foil of the second embodiment. 4 is a process cross-sectional view corresponding to each step of FIG.

-Step S1-
First, as the carrier 2, a metal foil formed by a rolling method or an electrolytic method is prepared (FIG. 4A). Here, untreated electrolytic copper foil (copper foil not subjected to surface treatment) obtained by an electrolytic method is used. The thickness is set to 35 μm, for example.

-Step S2-
Next, the diffusion preventing layer 3 is formed on the surface of the carrier 2 (FIG. 4B). Specifically, a plating bath for forming the diffusion preventing layer is prepared, and the surface of the carrier 2 is immersed in the plating bath, and the diffusion preventing layer 3 is formed on the surface of the carrier 2 by electroplating. The diffusion prevention layer is an induced eutectoid film deposited from a plating solution comprising a plating solution containing molybdenum and / or phosphorus and a plating solution in which at least one of nickel and cobalt is selected. An alloy layer of phosphorus is formed as a diffusion preventing layer. The thickness is, for example, 290 mg / m ² .

-Step S3-
Next, a release layer 4 is formed on the surface of the diffusion preventing layer 3 (FIG. 4C). As a method for forming the release layer 4, a physical film forming method such as a known vacuum deposition method, sputtering method, or ion plating method can be used. The release layer 4 is preferably made of the same kind of metal atoms as the transfer layer 5 formed in the next step S4.

-Step S4-
Next, the transfer layer 5 is formed on the surface of the release layer 4 (FIG. 4D). The transfer layer can be formed by a chemical film formation method using a plating method, for example, an electrodeposition bath. Considering that copper is used for the transfer layer, it is preferable to use an acidic plating bath, for example, a “copper sulfate plating bath” in consideration of industrial mass production. As the copper sulfate plating bath, for example, a transfer layer is formed so as to have a predetermined thickness by immersing it in an electrolyte containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate and applying a predetermined current. It ’s fine. By this step, the composite metal foil 1 suitable for manufacturing a printed wiring board is completed.

  The transfer layer 5 formed by the plating method, which is a representative chemical film forming method, and the release layer 4 formed by the physical film forming method have low adhesion and can be easily peeled off with a certain force or more. Has been clarified through experiments. Even if the release layer 4 remains as a residue on the surface of the transfer layer 5, the release layer is composed of the same copper as the transfer layer, so there is almost no adverse effect.

  In addition, when manufacturing the printed wiring board mentioned later is assumed, as a further step, a roughening process is performed on the surface of the transfer layer 5 in order to improve the adhesion with the base material constituting the printed wiring board. May be.

  In this case, the transfer layer 5 formed on the carrier 2 may be subjected to cathodic electrolysis in a copper sulfate-sulfuric acid solution in the vicinity of the limit current density, and a roughened surface may be formed by dendritic or fine copper powder. In this case, the surface roughness of the roughened surface may be adjusted by the type of base material and the required adhesion with the base material. The surface roughness is preferably Rz: 6 μm or less, and more preferably Rz: 2 μm or less when an extremely fine fine pattern is formed. In addition, Rz means the ten-point average roughness described in JIS standard B0601: 1994.

  Furthermore, in order to prevent scattering of the copper powder, the transfer layer that has been subjected to the roughening treatment may be subjected to a coating treatment as necessary.

  When forming a printed wiring board to be described later, the bonding between the substrate and the transfer layer may be reduced due to the heat compression process or etching process for that purpose. Coating with different metals such as chromium, cobalt, molybdenum, nickel, phosphorus, tungsten, chromate treatment with solutions containing dichromate ions, organic protection with solutions containing benzotriazole, silane coupling agents or their derivatives Rust treatment or the like may be further performed.

(Third Embodiment) -Method for Manufacturing Printed Wiring Board-
Next, the method for manufacturing a printed wiring board using composite metal foil is demonstrated. FIG. 5 is a diagram showing a process of transferring the composite metal foil onto the substrate of the printed wiring board. FIG. 6 is a cross-sectional view showing a circuit pattern formed on a printed wiring board.

  As shown to Fig.5 (a), first, the composite metal foil 1 and the base material 6 which comprises a printed wiring board are faced, and both are made to closely_contact | adhere after that. Next, as shown in FIG.5 (b), the laminated body of the composite metal foil 1 and the base material 6 is formed by heat-compressing in the contact | adhered state.

  Next, as shown in FIG.5 (c), the transfer layer 5 was bonded together on the base material 6 by peeling off a carrier (upper layer part from the peeling layer 4 of the composite metal foil 1) from a laminated body. It will be in a state and a copper clad laminated board will be completed.

  Next, as shown in FIG. 6, a transfer layer 5a patterned by an etching method or the like is formed, thereby completing a printed wiring board 7 on which a circuit pattern is formed. Further, if necessary, a composite laminated board may be further laminated to form a printed wiring board having a multilayer structure.

  The peeling strength when the carrier is peeled off from the laminate is preferably 0.01 to 2.0 N / cm, and more preferably 0.05 to 1.0 N / cm. In some cases, a part of the diffusion preventing layer 3 becomes a residue during peeling, but the amount was confirmed to be extremely small.

  Hereinafter, the embodiment will be described in detail.

Example 1
First, in order to form the carrier 2, an electrodeposition bath filled with an electrolytic solution containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate was prepared. Then, the electrodeposition bath maintained at a bath temperature of 40 ° C. was electrolyzed at a current density of 10 A / dm ^{2 for} 15 minutes and 35 seconds to form a carrier (untreated electrolytic copper foil) 2 made of a copper foil having a thickness of 35 μm ( Step S1). The carrier was immersed in 1.8 wt% sulfuric acid for 60 seconds and then washed with ion exchange water for 15 seconds. Next, in order to form the diffusion preventing layer 3, nickel sulfate hexahydrate 30 g / l, sodium hypophosphite monohydrate 1 g / l, sodium acetate trihydrate 10 g / l, adjusted to pH 4.5 The plating bath was prepared, the carrier 2 was immersed, and cathodic electrolysis was performed at a current density of 2 A / dm ^{2 for} 5 seconds to form a diffusion prevention layer 3 made of nickel-phosphorus, and this copper foil was subjected to ion exchange water for 15 seconds. It was washed and air dried (step S2).

Next, in order to form the peeling layer 4, a 0.3 μm copper layer was formed by a sputtering method (step S3). Further, in order to form the transfer layer 5 on the surface, the carrier on which the release layer is formed is immersed in an electrolytic solution containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate to 5 A / dm ² . For 4 minutes and 27 seconds to form a transfer layer made of a copper foil having a thickness of 5 μm (step S4). Since the release layer 5 is a copper layer, if it is immersed for a long time, the dissolution reaction in the copper sulfate plating bath is accelerated and the release layer may be dissolved. The electrodeposition work to form must be started.

  Finally, the transfer layer 5 was roughened by a known method. This is performed for the purpose of improving the adhesive strength with the transfer layer when the substrate is a resin. In this case, the roughening process precipitated dendritic or fine copper powder.

As a roughening treatment, an electrodeposition bath filled with an electrolytic solution containing 100 g / l sulfuric acid and 50 g / l copper sulfate pentahydrate was prepared for forming fine copper powder, and the bath temperature was maintained at 40 ° C. The electrodeposition bath was subjected to cathodic electrolysis at a current density of 10 A / dm ^{2 for} 10 seconds to precipitate fine copper powder.

Next, in order to prevent the copper powder of the transfer layer subjected to the roughening treatment from falling off and scattering, coated copper was formed. In forming the coated copper, an electrodeposition bath filled with an electrolytic solution containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate was prepared, and the electrodeposition bath maintained at a bath temperature of 40 ° C. was used as a current density. Cathodic electrolysis was performed at 5 A / dm ^{2 for} 1 minute and 20 seconds.

Next, a chromate film was formed on the surface of the transfer layer on which the coated copper was formed. Specifically, an electrodeposition bath containing sodium dichromate 5 g / l and adjusted to pH 13 was prepared, and cathodic electrolysis was performed at a bath temperature of 30 ° C. and a current density of 2 A / dm ^{2 for} 5 seconds to form a chromate film. Thereafter, a silane coupling agent layer-forming bath containing 2 m / l of γ-aminopropyltriethoxysilane was prepared, immersed for 15 seconds at a bath temperature of 30 ° C. to form a silane coupling agent layer, and then dried to form a composite metal. A foil was obtained. Next, a prepreg in which glass fiber was impregnated with an epoxy resin was prepared as a base material constituting the printed wiring board. And the laminated body which bonded the transfer layer to the surface of the base material was heat-compressed for 60 minutes at 170 degreeC * 4MPa in the state which accumulated the composite metal foil so that it might transfer to a base material.

  In addition, it has confirmed that the composite metal foil as described in this Example has heat resistance up to at least 250 ° C. in the sense of heat resistance in the heat compression process.

(Example 2)
A plating bath adjusted to 40 g / l of cobalt sulfate heptahydrate, 25 g / l of disodium molybdate dihydrate, 45 g / l of sodium citrate, pH 5.5 as plating for forming the diffusion prevention layer in Example 1 above. The laminate was formed in the same manner as in Example 1 except that the carrier was immersed and cathodic electrolysis was performed at a current density of 7 A / dm ^{2 for} 2 seconds to form a diffusion prevention layer made of cobalt-molybten. .

(Examples 3 to 4)
A laminated body in the same manner as in Examples 1 and 2 except that in order to form a release layer in Examples 1 and 2, a 0.2 μm copper layer was formed by a known vapor deposition method instead of the sputtering method to obtain a release layer. Formed.

(Example 5)
In the formation of the diffusion preventing layer in Example 1, nickel sulfate hexahydrate 30 g / l, sodium hypophosphite monohydrate 1 g / l, sodium acetate trihydrate 10 g / l, and pH 4.5 were adjusted. A laminate was obtained in the same manner as in Example 1 except that a plating bath was prepared, the carrier was immersed, and cathodic electrolysis was performed at a current density of 2 A / dm ^{2 for} 20 seconds to form a diffusion prevention layer made of nickel-phosphorus. .

(Example 6)
In Example 1, the transfer layer forming step was immersed in an electrolytic solution containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate, and was subjected to cathodic electrolysis at 5 A / dm ^{2 for} 1 minute and 20 seconds. A laminated body was formed in the same manner as in Example 1 except that a transfer layer made of 1.5 μm copper foil was formed.
(Example 7)
In Example 2, the transfer layer forming step was immersed in an electrolytic solution containing 100 g / l of sulfuric acid and 250 g / l of copper sulfate pentahydrate, and was subjected to cathodic electrolysis at 5 A / dm ^{2 for} 8 minutes and 1 second. A laminate was formed in the same manner as in Example 2 except that a transfer layer made of 9 μm copper foil was formed.

(Comparative Example 1)
In Example 1, a diffusion preventing layer was formed on the carrier, but in Comparative Example 1, a laminate was formed in the same manner as Example 1 except that the diffusion preventing layer was not formed.
(Comparative Examples 2-3)
In the said Examples 1-2, the laminated body was formed like Example 1-2 except not having formed the peeling layer.
(Comparative Example 4)
In Example 1, a laminate was formed in the same manner as Example 1 except that the thickness of the transfer layer was 18 μm.
(Comparative Example 5)
As a method for forming the diffusion prevention layer in Example 1, a laminate was formed by the same method as in Example 1 except that an alloy layer made of nickel-chromium was formed to 10 nm by sputtering.

  Table 1 shows the results of the investigation of the peeled state that summarizes the above.

(Examples 8 to 11)
In Examples 1 to 4, laminates were obtained by changing the heat compression conditions for bonding the transfer layer to the surface of the substrate. Prepare a prepreg in which glass fiber is impregnated with epoxy resin as a base material and heat it at 190 ° C, 3 MPa, 100 minutes. Prepare a polyimide film and heat-compress it through an adhesive at 250 ° C, 3 MPa, 60 minutes. Obtained. Table 2 shows the results of the investigation of the peeled state that accompanies changes in the heat compression conditions.

(Peel test evaluation method)
In addition, about the evaluation of the peeling state in the said Example and comparative example, the measurement of peeling strength, and wiring workability, it investigated by the following methods.

(1) Evaluation of peeled state A laminate cut into a size of 100 mm in length and 100 mm in width was prepared as a sample, and the peeled state of the carrier with respect to the transfer layer of the sample was visually confirmed. The case where the carrier was peeled from the transfer layer over the entire range was evaluated as “◯”, and the case where the carrier was partially or not peeled off from the transfer layer was evaluated as “x”.

(2) Measurement of peel strength The peel strength between the transfer layer and the carrier was measured based on JIS-C-6481 (1996).

(3) Wiring workability A laminate cut into a size of 200 mm in length × 150 mm in width is prepared as a sample, and the line width / line spacing (L: line / S: space) is 25 μm / 25 μm by a well-known method usually performed. A fine pattern was formed to investigate whether the wiring processing was completed beautifully. “○” when the wiring is beautifully formed, “△” when the wiring is formed but the line linearity or line width / line spacing is not good, and the target wiring is not formed. The case where a defect occurred was evaluated as “x”.

  From the results shown in Table 1, when Examples and Comparative Examples are compared, it can be seen that when the diffusion prevention layer 3 and the release layer 4 are not formed, the release after heat compression is impossible. Further, as in Comparative Example 1, when the sputtered film of the prior art is used as a peeling layer and the diffusion prevention layer is not formed, if an acid plating bath is used, peeling is possible before heat compression, but peeling is difficult after heat compression. It is confirmed that it becomes. Therefore, it can be seen that if a diffusion preventing layer is formed between the carrier and the release layer, the release is possible even after heat compression.

  Further, from the results in Table 2, it was confirmed that even when the heating and compression conditions were changed and increased to 250 ° C., a good peeled state could be obtained.

  When the composite metal foil according to the present invention is used, since the release layer is copper, the composite metal foil can be obtained without considering the adverse effect due to the residue of the release layer, and inexpensive acid-based plating in the transfer layer forming step Even if a bath is used, the composite metal foil can be provided at low cost because it can be peeled off even after heat compression.

DESCRIPTION OF SYMBOLS 1 Composite metal foil 2 Carrier 3 Diffusion prevention layer 4 Release layer 5 Transfer layer 5a Patterned transfer layer 6 Base material 7 Printed wiring board

Claims (6)

A diffusion preventing layer formed on the surface of the carrier made of copper foil and preventing diffusion of the metal to the carrier;
A release layer made of copper formed by a physical film formation method on the diffusion prevention layer,
On the release layer, a transfer layer formed by a plating method using an acidic plating bath,
Have
The diffusion prevention layer is composed of an induced eutectoid film deposited from a plating solution comprising a plating solution containing molybdenum or phosphorus or both, and a plating solution in which at least one is selected from nickel and cobalt,
Both the peeling layer and the transfer layer are made of copper and are in direct contact with each other. The thickness of the diffusion barrier layer is a ^{0.05mg / m 2 ~1000mg / m 2} ,
The total thickness of the release layer and the transfer layer is 0.1 μm or more and 12 μm or less;
The composite metal foil according to claim 1. The composite metal foil according to claim 1,
A composite metal foil, wherein a laminated film similar to the laminated film including the diffusion preventing layer, the release layer, and the transfer layer formed on the surface of the carrier is also formed on the back side of the carrier. Preparing a carrier made of copper foil (S1);
A diffusion preventing layer forming step (S2) formed by forming a diffusion preventing layer on at least one surface of the carrier;
A release layer forming step (S3) in which a release layer made of copper is formed on the surface of the diffusion prevention layer by a physical film formation method;
A transfer layer forming step (S4) formed by forming a transfer layer composed of copper on the surface of the release layer by a plating method using an acidic plating bath;
The manufacturing method of the composite metal foil characterized by having. By having the diffusion prevention layer forming step (S2) and the release layer forming step (S3),
The method for producing a composite metal foil according to claim 4, wherein the composite metal foil can be peeled even when heated to a temperature range of 250 ° C. On the base material for forming the printed wiring board,
Laminate the composite metal foil according to any one of claims 1 to 3,
A printed wiring board obtained by peeling the release layer and the transfer layer with the release layer.

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