JP5505828B2 - Composite metal foil and method for producing the same - Google Patents

Description

The present invention relates to a composite metal foil and a manufacturing how.

  As is well known, electronic devices typified by mobile phones and digital cameras tend to be miniaturized, but are remarkably multi-functional and require improved processing speed. For this reason, printed wiring boards incorporated as components in these electronic devices have been increased in density so as to satisfy the two requirements of downsizing and improvement in processing speed.

  In order to realize high-density printed wiring boards, it is necessary to make the circuit a fine pattern by thinning the copper foil attached to the substrate that constitutes the printed wiring board. Ultra-thin copper foil is used. Such an ultrathin copper foil is likely to be wrinkled or cracked when attached to a substrate, and is very difficult to handle.

  For this reason, as a method that can be easily attached without causing wrinkles or cracks when attaching an ultrathin copper foil to a substrate, for example, in Patent Document 1 described later, a release layer is formed by chromate treatment. A conductive layer is formed on a substrate using a conductive material for a printed wiring board, in which a conductive layer made of a fine and fine powdery copper layer having a peelability of 0.3 to 1.5 μm is formed on the formed carrier. Is disclosed. Further, in Patent Document 2 described later, an ultrathin copper foil is transferred to a substrate using a composite copper foil for forming a printed wiring board having an organic release layer between a support metal layer and an ultrathin copper foil. A method is disclosed.

  However, when the release layer formed by the chromate treatment disclosed in Patent Document 1 or the organic release layer disclosed in Patent Document 2 is transferred to an ultrathin copper foil, There was a problem that a large amount was transferred to the base material side together with the ultrathin copper foil. The peeling layer residue transferred to the resin substrate causes problems in the masking process, the etching process, and the thick plating process for forming a circuit on the ultrathin copper foil, and is particularly formed by the thick plating process. This caused the thick plating layer to peel off.

  For this reason, in the following Patent Document 3, a composite copper foil for forming a printed wiring board having an organic release layer between a support metal layer and an ultrathin copper foil is used as an insulating substrate, and insulated from the ultrathin copper foil. Lamination is performed so that the substrate comes into contact, the support metal layer is peeled from the composite copper foil for forming a printed wiring board, the ultrathin copper foil is exposed, and the ultrathin copper foil remains on the surface. A method for producing a copper clad laminate in which an organic release layer is removed by washing with an aqueous alkali solution or aqueous hydrochloric acid solution is disclosed.

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

  As described above, in various conventional composite metal foils, when the ultrathin copper foil is transferred to the base material, a large amount of the release layer is transferred together with the ultrathin copper foil to the base material side. As disclosed, it was necessary to perform a treatment for removing the release layer residue, and the production efficiency was very poor.

The present invention, when transferring the ultra-thin copper foil to the substrate, the release layer to obtain a composite metal foil and a manufacturing how only a degree not causing a problem not transcribed in the step for forming the circuit As a technical issue, as a result of repeating trial production and experimentation, in order to realize its realization, the release layer constituting the composite metal foil may be formed by attaching a solution containing chromic acid and an organic compound. We have obtained remarkable knowledge and achieved the above technical problem.

  The technical problem can be solved by the present invention as follows.

That is, the method for producing a composite metal foil according to the present invention comprises one or two selected from chromic acid and adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid, terephthalic acid on the surface of the support made of the metal foil. A release layer forming step for forming a release layer containing 0.01 to 1.0 mg / m ^{2 of} Cr by attaching a solution containing the above organic compound, and a transfer layer for forming a transfer layer made of a metal foil on the release layer Forming step.

  Further, the present invention provides the method for producing a composite metal foil, wherein in the release layer forming step, the surface of the support made of the metal foil is selected from chromic acid, adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid, and terephthalic acid. The release layer is formed by electrolyzing the solution in a state where a solution containing one or two or more organic compounds is adhered.

  Further, the present invention provides the method for producing any one of the composite metal foils, wherein the chromic acid is one or more selected from chromium oxide, potassium dichromate, sodium dichromate, and lithium chromate. is there.

Further, the composite metal foil according to the present invention comprises a support made of a metal foil, and one or two selected from chromic acid and adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid, and terephthalic acid on the surface of the support. Provided with a release layer containing 0.01 to 1.0 mg / m ^{2 of} Cr formed by adhering a solution containing more than one kind of organic compound, and a transfer layer made of a metal foil formed on the release layer It is.

  According to the present invention, since the release layer constituting the composite metal foil is formed by adhering a solution containing a chromium compound and an organic compound to the support, the ultrathin copper foil is transferred to the substrate. The release layer is transferred to the substrate side only to the extent that it does not cause a problem with respect to each step for forming a circuit, thereby removing the release layer residue from the ultrathin copper foil after transfer. A circuit can be formed without application.

  Therefore, it can be said that the industrial applicability of the present invention is very high.

It is sectional drawing which showed the composite metal foil which concerns on embodiment. It is sectional drawing which showed the composite metal foil which concerns on a modification. It is sectional drawing which showed the process of transcribe | transferring a transfer layer to a base material with the composite metal foil which concerns on embodiment.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view showing a composite metal foil in the present invention. FIG. 2 is a sectional view showing a modification of the composite metal foil in the present invention. FIG. 3 is a cross-sectional view showing a process of transferring a transfer layer to a substrate with the composite metal foil in the present invention. In these drawings, reference numeral 1 denotes a support 2, a release layer 3 formed by attaching a solution containing chromic acid and an organic compound to the surface of the support 2, and a metal formed in the release layer 3. It is a composite metal foil made of a transfer layer 4 made of foil.

  The support 2 is not limited as long as it is a metal foil having heat resistance. For example, it is preferable to use a copper foil, a copper alloy foil, an iron foil, an iron alloy foil, a nickel foil, a nickel alloy foil, an aluminum foil or the like formed by a rolling method or an electrolytic method, and in particular, use a copper foil. preferable. When a copper foil is used as the support 2, the thickness of the copper foil is preferably 18 to 100 μm, and more preferably 18 to 35 μm.

The release layer 3 is formed by attaching a solution containing chromic acid and an organic compound to the surface of the support 2. Specifically, a release layer is deposited on the surface of the support by depositing a solution containing chromic acid and an organic compound on the surface of the support 2. The release layer 3 formed on the surface of the support 2 preferably contains 0.01 to 1.0 mg / m ^{2 of} Cr, and more preferably 0.1 to 1.0 mg / m ² . When the Cr contained in the release layer 3 is within the above range, the peel strength between the support 2 and the transfer layer 4 at the time of transfer is 0.01 to 0.15 KN / m. If the external force is not applied to some extent, the transfer layer 4 is not peeled off, so that it becomes easy to handle in the manufacturing process.

  As chromic acid, one or more selected from chromium oxide, potassium dichromate, sodium dichromate, and lithium chromate may be used. In addition, when using sodium dichromate, it is preferable to contain 0.01-10 g / l with respect to the said solution, and it is more preferable to contain 0.01-1 g / l.

  As the organic compound, one or more selected from adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid, and terephthalic acid may be used. In addition, it is preferable to contain 0.01-10 g / l of organic compounds with respect to the said solution, and it is more preferable to contain 0.01-1.0 g / l.

  The transfer layer 4 is a layer that is transferred to the base material constituting the printed wiring board, and a highly conductive metal foil may be used. Specifically, it is preferable to use a copper foil. The thickness of the transfer layer is preferably 0.1 to 12 μm, and preferably 0.1 to 9 μm, because it affects the fine patterning of the circuit when transferred to the substrate constituting the printed wiring board. More preferred.

  The release layer 3 and the transfer layer 4 may be formed on only one side of the support 2 as shown in FIG. 1, or on both sides of the support 2 as shown in FIG. Also good.

  Next, the manufacturing method of the composite metal foil which concerns on this invention is demonstrated.

  First, a support 2 made of a metal foil formed by a rolling method or an electrolytic method is prepared. Next, a solution containing chromic acid and an organic compound is prepared, and the surface of the support 2 is immersed in the solution to attach the solution to the surface of the support 2. Thereby, the peeling layer 3 is deposited by the solution adhering to the surface of the support 2 (peeling layer forming step). Then, the transfer layer 4 is formed by immersing the surface of the release layer 3 formed on the support 2 in an electrodeposition bath and electrodepositing a metal foil having a thickness of 0.1 to 1.0 μm (transfer layer forming step). Thereby, the composite metal foil 1 is formed.

  In the release layer forming step, the surface of the support 2 is immersed in the solution to deposit the release layer 3, but the solution is electrolyzed in a state where the surface of the support 2 is immersed in the solution. The release layer 3 may be deposited.

Note that the time for immersing the support 2 in the solution in the release layer forming step is appropriately adjusted to vary depending on the concentration of chromic acid and organic compounds contained in the solution and whether or not the solution is electrolyzed, and at least precipitation The amount of Cr contained in the release layer is preferably adjusted to 0.01 to 1.0 mg / m ^2, and more preferably 0.1 to 1.0 mg / m ² .

  Further, as the electrodeposition bath for electrodepositing a metal foil on the surface of the release layer 3, it is preferable to use an electrodeposition bath having a pH value of weakly acidic to alkaline, and specifically, a pH value of 4 or more. The electrodeposition bath shown is preferred. The transfer layer 4 may be formed by electrodeposition of a metal foil that reaches a desired thickness only by the electrodeposition bath exhibiting the pH value. It may be formed by electrodeposition. When a plurality of electrodeposition baths are used in combination, an electrodeposition bath having the above pH value is used as the primary electrodeposition bath for electrodepositing a metal foil on the surface of the release layer 3, and the metal foil is made thinner than desired After the electrodeposition, the metal foil may be electrodeposited until the desired thickness is reached using an electrodeposition bath not limited to the pH value after the secondary electrodeposition bath. Examples of the electrodeposition bath exhibiting the pH value include a copper pyrophosphate electrodeposition bath and a copper citrate electrodeposition bath, and examples of the electrodeposition bath not limited to the pH value include a copper sulfate electrodeposition bath. .

  In addition, the transfer layer 4 is coated with a roughening treatment to improve physical bonding with the substrate constituting the printed wiring board, and a coating treatment to prevent the copper powder formed by the roughening treatment from falling off. Moreover, you may give a passivation process, an organic rust prevention process, etc. in order to improve a chemical bond with the base material which comprises a printed wiring board, an improvement in heat resistance and chemical resistance, and oxidation prevention. When the roughening treatment is performed, the transfer layer 4 may be cathodic electrolyzed in the vicinity of the limit current density in a copper sulfate-sulfuric acid solution to deposit dendritic or fine copper powder. When the coating treatment is performed, the transfer layer 4 is cathodic electrolyzed in a copper sulfate-sulfuric acid solution at a normal current density, and a copper foil is deposited to cover the copper powder. In addition, when performing passivation treatment, coating with a different metal from copper such as Zn, Cr, Co, Mo, Ni, P, W, etc., or chromate coating with a solution containing dichromate ions may be performed. . Moreover, what is necessary is just to form the film by the solution containing a benzodriazole, a silane coupling agent, or these derivatives when performing organic rust prevention processing.

  Next, the process of producing a printed wiring board using the composite metal foil according to the present invention will be described with reference to FIG.

  First, the transfer layer 4 of the composite metal foil 1 is brought into close contact with the base material 5 constituting the printed wiring board (see FIG. 3A). Next, the composite metal foil 1 is heated and compressed from the support side with the transfer layer 4 in close contact with the substrate 5 to bond the transfer layer 4 to the substrate 5 to form a laminate 6 (FIG. 3 ( b)). Thereafter, the transfer layer 4 is transferred to the substrate 5 by peeling off the support 2 from the transfer layer 4 (see FIG. 3C). Then, a printed wiring board is formed by forming a circuit on the transfer layer 4.

  Example 1

First, in order to form a support, an electrodeposition bath filled with an electrolytic solution containing 100 g / l sulfuric acid and 250 g / l copper sulfate pentahydrate was prepared. The electrolytic 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, and the 35 μm thick copper foil deposited on the surface of the titanium plate was peeled off to produce a support. did. This support was immersed in 1.8 wt% sulfuric acid for 60 seconds and then washed with ion-exchanged water for 15 seconds.

  Next, in order to form a release layer on the support, a release layer forming bath filled with an aqueous solution containing 0.05 g / l adipic acid and 0.10 g / l sodium dichromate was prepared. Then, the support was immersed in a release layer forming bath maintained at a bath temperature of 25 ° C. for 30 seconds to form a release layer on the surface of the support. This release layer was washed with ion exchange water for 15 seconds.

Next, in order to form a transfer layer on the release layer by two-stage electrolysis, primary electrodeposition filled with an electrolyte having a pH value of 8.5 containing 50 g / l copper pyrophosphate and 500 g / l potassium pyrophosphate. A bath and a secondary electrodeposition bath filled with an electrolyte containing 100 g / l sulfuric acid and 250 g / l copper sulfate pentahydrate were prepared. Then, the support was immersed in a primary electrodeposition bath maintained at a bath temperature of 50 ° C. and electrolyzed at a current density of 3.0 A / dm ^{2 for} 89 seconds to form a 1.0 μm thick copper foil. This copper foil was washed with ion exchange water for 15 seconds. Further, the support was immersed in a secondary electrodeposition bath maintained at a bath temperature of 40 ° C. and electrolyzed at a current density of 5 A / dm ^{2 for} 214 seconds to form a copper foil having a thickness of 4.0 μm. Thereby, a transfer layer made of 5.0 μm copper foil was formed on the release layer.

Finally, a roughening process, a covering process, a passivating process, and an organic film forming process were sequentially performed on the transfer layer. Specifically, a roughening treatment bath filled with an aqueous copper sulfate solution containing copper sulfate pentahydrate 50 g / l and sulfuric acid 100 g / l is prepared for the roughening treatment, and the bath temperature is set to 40 ° C. The transfer layer was immersed in the maintained roughening bath and electrolyzed at a current density of 10 A / dm ^{2 for} 10 seconds to deposit fine copper powder on the surface of the transfer layer. Next, a coating treatment bath filled with an aqueous copper sulfate solution containing 250 g / l of copper sulfate pentahydrate and 100 g / l of sulfuric acid was prepared for the coating treatment, and the coating treatment was maintained at a bath temperature of 40 ° C. The transfer layer was immersed in a bath and electrolyzed at a current density of 5.0 A / dm ^{2 for} 80 seconds to deposit a copper foil covering the surface of the transfer layer with fine copper powder. Next, in order to perform the passivation treatment, a passivation treatment bath containing sodium dichromate 5 g / l and adjusted to pH 13 with sodium hydroxide was prepared, and the passivation temperature was maintained at 30 ° C. The transfer layer was immersed in a heat treatment bath and electrolyzed at a current density of 2.0 A / dm ^{2 for} 5 seconds to deposit a chromate film on the surface of the transfer layer. Next, an aqueous solution of a silane coupling agent containing 2 m / l of γ-aminopropyltriethoxysilane in order to improve the chemical bond strength with the base material constituting the printed wiring board and the rust prevention capability. An organic film forming treatment bath was prepared, and the transfer layer was dipped in a rust prevention treatment bath maintained at a bath temperature of 30 ° C. for 15 seconds and dried to deposit a silane coupling agent film on the surface of the transfer layer. A composite metal foil was obtained through the above steps.

  Subsequently, a prepreg in which glass fiber was impregnated with an epoxy resin was prepared as a base material constituting the printed wiring board. Then, a laminated body in which the composite metal foil was laminated so as to adhere the transfer layer to the substrate and heat-pressed at 170 ° C. and 4 MPa was obtained to bond the transfer layer to the surface of the substrate.

  Example 2

In Example 1, in order to form a transfer layer in the release layer, only an electrodeposition bath filled with an electrolyte solution having a pH value of 8.5 containing copper pyrophosphate 50 g / l and potassium pyrophosphate 500 g / l was prepared. The substrate was immersed in an electrodeposition bath maintained at a bath temperature of 50 ° C., electrolyzed at a current density of 3.0 A / dm ^{2 for} 89 seconds, and a transfer layer made of a 1.0 μm thick copper foil was formed. A laminate was obtained in the same manner as in Example 1.

  Examples 3-7 and Comparative Examples 1-8

  In Example 1, the same procedure as in Example 1 except that a release layer forming bath filled with an aqueous solution containing an organic compound and / or chromic acid shown in the table was prepared to form a release layer on the support. Thus, a laminate was obtained.

  Comparative Example 9

In Example 1, the outer that the support was immersed for 3 minutes in the peeling layer formation bath, to obtain a laminate in the same manner as in Example 1.

The following measurements and evaluations were performed on the laminates obtained in Examples 1 to 7 and Comparative Examples 1 to 9. The results of measurement and evaluation are shown in the table.
a. Measurement of peel strength The peel strength between the transfer layer and the support was measured based on JIS-C-6481 (1996).
b. Evaluation of peeled state A laminated body cut to a size of 100 mm long × 100 mm wide was prepared as a sample, and the peeled state of the support with respect to the transfer layer of the sample was visually confirmed. “◯” indicates that the support is peeled from the transfer layer over the entire range, “△” indicates that the support is only partially peeled from the transfer layer, and the support is completely peeled from the transfer layer. Those that were not evaluated were evaluated as “x”.
c. Measurement of Cr adhesion amount Samples that were evaluated as “◯” or “Δ” in the evaluation of the release state were cut into a size of 10 mm × 40 mm, and the release layers attached to the transfer layer side and the support side were diluted. After dissolving in 100 ml of nitric acid, the amount of Cr contained in the solution was measured by ICP analysis. Further, the total amount of Cr measured from the paired transfer layer and the support was calculated as the total amount of Cr contained in the release layer.

  From the result of the measurement and evaluation, in the composite metal foil in which the release layer is formed by the release layer forming bath containing only one of chromic acid or the organic compound, the support is formed after the transfer layer is transferred to the substrate. In the composite metal foil in which the release layer is formed by the release layer forming bath containing both chromic acid and the organic compound, the transfer layer is transferred to the base material. It can be seen that the support can be completely peeled off.

Moreover, in the composite metal foil in which the amount of Cr contained in the release layer exceeded 1.0 mg / m ² as in Comparative Example 8 or 9, the peel strength was extremely reduced, making it difficult to handle.

DESCRIPTION OF SYMBOLS 1 Composite metal foil 2 Support body 3 Release layer 4 Transfer layer 5 Base material 6 Laminated body

Claims (4)

By attaching a solution containing chromic acid and one or more organic compounds selected from adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid and terephthalic acid to the surface of the support made of metal foil a peeling layer formation step of forming a 0.01 to 1.0 mg / m ² containing the release layer of cr, the separation layer of the composite metal foil and having a transfer layer forming step of forming a transfer layer made of a metal foil Production method. Solution containing one or more organic compounds selected from chromic acid and adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid, terephthalic acid on the surface of the support made of metal foil in the release layer forming step The method for producing a composite metal foil according to claim 1, wherein the release layer is formed by electrolyzing the solution in a state where the metal is adhered. The method for producing a composite metal foil according to claim 1 or 2, wherein the chromic acid is one or more selected from chromium oxide, potassium dichromate, sodium dichromate, and lithium chromate. . A support comprising a metal foil, and a solution containing one or more organic compounds selected from chromic acid and adipic acid, benzoic acid, salicylic acid, toluic acid, sulfanilic acid and terephthalic acid on the surface of the support. A composite metal foil comprising a release layer containing 0.01 to 1.0 mg / m ^{2 of} Cr formed by adhesion and a transfer layer made of a metal foil formed on the release layer.

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