JP6031332B2 - Surface-treated copper foil, laminate using the same, printed wiring board, electronic component, and method for producing surface-treated copper foil - Google Patents

Description

  The present invention relates to a surface-treated copper foil, a laminate using the same, a printed wiring board, an electronic component, and a method for producing the surface-treated copper foil.

  In a small electronic device such as a smartphone or a tablet PC, a flexible printed wiring board (hereinafter referred to as FPC) is adopted because of easy wiring and light weight. In addition, for FPC, a desired wiring is formed by a subtractive method or an additive method using a two-layer flexible substrate in which a base layer made of metal or metal oxide is directly provided on an insulator substrate and a copper conductor layer is formed. There is a two-layer flexible printed wiring board on which a pattern is formed.

  Flat rolled copper foil is widely used for such a two-layer flexible printed wiring board. In recent years, a copper foil having a smaller thickness is preferably used in order to improve flexibility and fine etching. However, the highly flexible rolled copper foil becomes soft because the crystal size becomes large after recrystallization, and in the case of a thin foil of 10 μm or less, the apparent peel strength is lowered, and there is a problem in bonding with a resin substrate. May occur.

Therefore, for the purpose of improving the peel strength, a method of surface treatment of the adhesive surface of the copper foil resin with a silane coupling agent containing hexavalent chromium has been proposed. Silane precipitates when mixed with hexavalent chromium.
For example, Patent Documents 1 to 5 disclose these conventional techniques.

Japanese Patent No. 3292774 Japanese Patent No. 3306404 Japanese Patent No. 3906347 International Publication No. 2009-81889 Japanese Patent Laid-Open No. 11-158652

However, when surface treatment of the adhesive surface with copper foil resin is performed with a silane coupling agent containing hexavalent chromium, it does not match the manufacturing process of the two-layer flexible printed wiring board, and the peel strength is reduced. There is a problem that silane aggregation in the silane coupling agent is promoted. In Patent Document 5, electrolytic copper foil is immersed in an alkaline solution of chromic anhydride (chromic anhydride: 6 g / l; sodium hydroxide: 15 g / l; pH: 12.5; bath temperature: 25 ° C.) for 5 seconds. However, the surface-treated copper foil is produced by forming a rust preventive film on both sides of the copper foil. When a treatment liquid having a high pH is used, NaOH and KOH are taken out of the treatment liquid and dried. , Salt is formed, and good peel strength cannot be obtained.
Then, an object of this invention is to provide the manufacturing method of surface treatment copper foil with favorable peel strength, a laminated body using the same, a printed wiring board, an electronic component, and surface treatment copper foil.

  As a result of extensive research, the present inventor has formed a chromium oxide surface treatment layer on the side of the copper foil that adheres to the resin substrate, and the surface treatment layer is immersed in a nitric acid bath under predetermined conditions. It was found that the peel strength of the surface-treated copper foil was improved by controlling the amount of copper eluted at the time.

The present invention completed on the basis of the above knowledge has, in one aspect, a surface treatment layer formed of chromium oxide, and after applying heat treatment at 250 ° C. for 10 minutes, only the surface of the surface treatment layer is applied. When exposed to a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. for 30 seconds, the surface-treated copper foil has an elution amount of copper of 0.0030 g / 25 cm ² or less.

  In one embodiment of the surface-treated copper foil according to the present invention, the adhesion amount of hexavalent chromium is 0.1% or less of the adhesion amount of trivalent chromium in the surface treatment layer.

  In another embodiment of the surface-treated copper foil according to the present invention, the surface-treated layer has a thickness of 0.1 to 2.5 nm.

  In still another embodiment of the surface-treated copper foil according to the present invention, a base layer is formed between the copper foil and the surface-treated layer.

  In still another embodiment of the surface-treated copper foil according to the present invention, the foundation layer includes a roughened layer.

  In still another embodiment of the surface-treated copper foil according to the present invention, the foundation layer includes a heat discoloration prevention layer and / or a rust prevention layer.

  In still another embodiment of the surface-treated copper foil according to the present invention, the heat discoloration prevention layer and the rust prevention layer are Zn, Cu, or an alloy thereof, respectively.

  In still another embodiment of the surface-treated copper foil according to the present invention, the rust preventive layer includes a chromate layer or a zinc chromate layer.

  In still another embodiment of the surface-treated copper foil according to the present invention, the foundation layer includes a silane coupling layer.

  In still another embodiment of the surface-treated copper foil according to the present invention, a silane coupling layer is formed on the surface-treated layer.

  In another aspect, the present invention is a laminate of the copper foil of the present invention and a resin substrate.

  In one Embodiment of the laminated body of this invention, the said copper foil and the said resin substrate are laminated | stacked without the adhesive agent.

  In yet another aspect, the present invention is a printed wiring board made from the laminate of the present invention.

  In still another aspect, the present invention is an electronic component including the printed wiring board of the present invention.

  In another aspect of the present invention, the step of providing a chromate solution over the entire surface of the copper foil to be treated, and the surface treatment of the chromium oxide by drying the chromate solution without washing with water after providing the copper foil surface. It is a manufacturing method of the surface treatment copper foil provided with the process of forming a layer.

  In one embodiment of the method for producing a surface-treated copper foil of the present invention, in the step of forming the surface treatment layer of the chromium oxide, after the chromate solution is provided on the surface of the copper foil, the liquid is drained and then not washed with water. The surface treatment layer of chromium oxide is formed by drying with.

In another one Embodiment of the manufacturing method of the surface treatment copper foil of this invention, the quantity which provided the said chromate liquid to the copper foil surface is 5-20 mg / dm < ² > after the said liquid draining.

  In another embodiment of the manufacturing method of the surface-treated copper foil of this invention, the said liquid draining is performed by spraying a roll, a braid | blade, and / or gas.

  In another embodiment of the method for producing a surface-treated copper foil of the present invention, the step of providing the chromate solution over the entire surface to be treated of the copper foil is performed by applying the chromate solution to the copper foil surface by showering. .

  In another embodiment of the method for producing a surface-treated copper foil of the present invention, the step of providing the chromate solution over the entire surface to be treated of the copper foil is performed by applying the chromate solution to the surface of the copper foil with a roller. .

  In another one Embodiment of the manufacturing method of the surface treatment copper foil of this invention, pH of the said chromate liquid is 1-10.

  In another one Embodiment of the manufacturing method of the surface treatment copper foil of this invention, pH of the said chromate liquid is 4-10.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of surface treatment copper foil with favorable peel strength, a laminated body using the same, a printed wiring board, an electronic component, and surface treatment copper foil can be provided.

[Configuration of surface-treated copper foil]
The copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil. The surface-treated copper foil of the present invention has a surface-treated layer formed of chromium oxide, and after heat treatment at 250 ° C. for 10 minutes, only the surface of the surface-treated layer is exposed. When immersed in a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. for 30 seconds, the elution amount of copper into the nitric acid bath is 0.0030 g / 25 cm ² or less. As the surface treatment, there is a method in which a metal chromium layer is formed on the surface of the copper foil by sputtering or the like. On the other hand, the surface treatment layer of the present invention is formed of chromium oxide, and the amount of copper eluted into the nitric acid bath is 0 when immersed in a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. for 30 seconds. Since it is controlled to be not more than .0030 g / 25 cm ^{2, the} corrosion resistance against the etching solution is good. In addition, the controlled amount of copper eluted into the acid in this way indicates that the surface treatment layer is densely and uniformly formed by the chromium oxide, so that the adhesion to the resin substrate is improved. And the peel strength is improved. The above “after heat treatment at 250 ° C. for 10 minutes” defines general heat treatment conditions for bonding to the polyimide substrate.

  In the surface-treated copper foil of the present invention, the amount of hexavalent chromium attached is preferably 0.1% or less of the amount of trivalent chromium attached in the surface treatment layer. According to such a configuration, the ratio of the amount of hexavalent chromium deposited is controlled, which is advantageous from the viewpoint of safety.

  In the surface-treated copper foil of the present invention, the surface-treated layer preferably has a thickness of 0.1 to 2.5 nm. Thus, when the thickness of the surface treatment layer is reduced, the etching removal property and the manufacturing cost of the surface treatment layer are improved. The thickness of the surface treatment layer is more preferably 0.3 to 1 nm.

  In the surface-treated copper foil of the present invention, a base layer may be formed between the copper foil and the surface-treated layer for various purposes. The underlayer is not particularly limited, and a known layer can be used. The underlayer may include a roughening treatment layer, for example, in order to further improve the adhesion with the insulating substrate. The roughening treatment can be performed, for example, by forming roughened particles with copper or a copper alloy. The roughening process may be fine. The roughening treatment layer may be a single layer selected from the group consisting of copper, nickel, cobalt and zinc, or a layer made of an alloy containing one or more of them. Further, the underlayer may include a heat discoloration prevention layer and / or a rust prevention layer. The heat discoloration preventing layer and the rust preventing layer by preventing the diffusion of Cu can be formed of Zn, Cu or an alloy thereof, respectively. The rust preventive layer may include a chromate layer or a zinc chromate layer. The underlayer may include a silane coupling layer.

[Production method of surface-treated copper foil]
The manufacturing method of the surface treatment copper foil of this invention is demonstrated. First, a rolled copper foil or an electrolytic copper foil is prepared. Next, if necessary, a roughening treatment layer, a heat discoloration prevention layer, a rust prevention layer, a silane coupling layer, and the like are formed on the copper foil surface by a known means as a base layer. Next, the chromate solution is provided on the entire surface of the copper foil to be processed. Next, the surface treatment layer of chromium oxide is formed on the copper foil surface by drying the copper foil surface without washing. In the conventional method, when the surface treatment is performed with the chromate solution, the chromate solution is provided on the surface of the copper foil, and then washed with water a plurality of times for removing impurities before the drying step. However, this washing with water forms a non-uniform chromate layer, which adversely affects the peel strength. On the other hand, in the present invention, the water washing step is not performed, and after the chromate liquid is provided on the entire surface to be treated of the copper foil, the copper foil surface is dried without washing, thereby forming a uniform chromate layer, The peel strength of the treated copper foil is improved. The step of providing the chromate solution over the entire surface to be treated of the copper foil may be performed by applying the chromate solution to the copper foil surface by a shower, or by applying the chromate solution to the copper foil surface with a roller. .

Further, in the method for producing a surface-treated copper foil of the present invention, in the step of forming the surface treatment layer of chromium oxide, the chromate solution is provided on the surface of the copper foil, then drained, and then dried without washing with water. A chromium oxide surface treatment layer may be formed. The liquid draining can be performed by blowing a roll, a blade and / or a gas. After the chromate solution is provided on the surface of the copper foil in this way, the liquid is drained and the amount of the chromate solution on the copper foil surface is controlled to suppress the attachment of hexavalent chromium to the product, and residual ions (K ⁺ ) Is less likely to be taken into the chromate film. Moreover, it is preferable that the quantity which provided the chromate liquid to the copper foil surface is 5-20 mg / dm < ² > after draining. If the amount of chromate liquid provided on the copper foil surface is less than 5 mg / dm ² , there is a possibility that a desired peel strength cannot be obtained. Further, if the amount of chromate solution provided on the surface of the copper foil is more than 20 mg / dm ² , the salt of H ₂ SO ₄ and K added for pH adjustment is precipitated because the solution is treated with a solution having the composition described later. There is a risk of problems.

The conditions of the chromate solution used for the surface treatment are as follows.
Liquid composition: CrO ₃ : 1 to 6 g / l, Na ₂ Cr ₂ O ₇ and K ₂ Cr ₂ O ₇ : 1.5 to 9 g / l in total
pH: 1-10, preferably 4-10
Temperature: 10-60 ° C, preferably 25-40 ° C
As described above, when a treatment solution having a pH of 1 to 10 is used, the elution of Ni can be satisfactorily suppressed even when Ni or the like is used for the base treatment. Further, when a treatment solution having a pH of 4 to 10 is used, the elution of Zn can be satisfactorily suppressed even if Zn-chromate is used for the base treatment.

  The surface-treated copper foil of the present invention can be bonded to a resin substrate from the treated surface side to produce a laminate. The resin substrate is not particularly limited as long as it has characteristics applicable to a printed wiring board or the like. For example, a paper base phenol resin, a paper base epoxy resin, a synthetic fiber cloth base epoxy resin for rigid PWB Glass cloth / paper composite base material epoxy resin, glass cloth / glass nonwoven fabric composite base material epoxy resin, glass cloth base material epoxy resin, etc. can be used, and polyester film, polyimide film, etc. can be used for FPC. In addition, the surface-treated copper foil of the present invention has a high adhesion to the resin substrate, so the laminated body is formed by laminating the copper foil and the resin substrate without using an adhesive and pressing them. It is also possible to do.

  In the case of the rigid PWB, a prepreg is prepared by impregnating a base material such as a glass cloth with a resin and curing the resin to a semi-cured state. It can be carried out by superposing a copper foil on the prepreg from the surface opposite to the surface treatment layer and heating and pressing it.

  The laminate of the present invention can be used for various printed wiring boards (PWB) and is not particularly limited. For example, from the viewpoint of the number of layers of the conductor pattern, it is applied to single-sided PWB, double-sided PWB, and multilayer PWB. It is possible to apply to rigid PWB, flexible PWB (FPC), and rigid flex PWB from the viewpoint of the type of insulating substrate material. Moreover, the printed wiring board produced in this way can be mounted on various electronic components that require high-density mounting of the mounted components.

  As Examples 1-6 and Comparative Examples 1-5, the copper foil of the thickness of Table 1 was prepared, and arbitrary underlayers (a roughening process layer, a heat discoloration prevention layer, a rust prevention layer, As the silane coupling layer, plating treatment was performed under the conditions shown in Table 1, respectively. Here, as copper foils of Examples 1 to 5 and Comparative Examples 1 to 4, rolled copper foil of tough pitch copper (JIS H3100 C1100R) manufactured by JX Nippon Mining & Metals was used. Moreover, as copper foil of Example 6 and Comparative Example 5, JX Nippon Mining & Metals electrolytic copper foil HLPLC foil was used.

  Next, on the copper foil or the base layer on the copper foil, the surface treatment liquid is applied to the entire surface to be treated of the copper foil under the conditions of Table 2, and further, after arbitrary washing and draining, and drying, A surface treatment layer was formed.

Various evaluation was performed as follows about each sample of the Example and comparative example which were produced as mentioned above.
(1) Chromium adhesion amount;
The treatment layer was dissolved by boiling for 3 minutes in hydrochloric acid having a concentration of 10%, and the solution was analyzed by atomic absorption analysis to evaluate the amount of trivalent and hexavalent chromium deposited.

(2) thickness of the surface treatment layer;
The thickness of the surface treatment layer was converted from the adhering amount of trivalent chromium as a density of 7.2 g / cm ³ .

(3) Elution amount into nitric acid;
After applying heat treatment at 250 ° C. for 10 minutes, it was immersed in a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. for 30 seconds with only the surface of the surface treatment layer exposed by 25 cm ² using a masking tape. Thereafter, the elution amount (g / 25 cm ² ) of the sample into the nitric acid bath was measured.

(4) peel strength;
In accordance with PC-TM-650, the normal peel strength was measured with a tensile tester Autograph 100, and the normal peel strength of 0.7 kN / mm or more could be used for copper clad laminated substrate applications.

(5) PCT (pressure cracker test);
As a pressure cracker test, it was treated at 121 ° C. under 2 atm for 48 hours, and the tensile strength was measured by the method of JIS-K7054 using the test piece after the durability test.
Table 3 shows the conditions and evaluation of each test.

According to Table 3, each of Examples 1 to 6 was subjected to a heat treatment at 250 ° C. for 10 minutes, and then a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. with only the surface of the surface treatment layer exposed. When immersed for 30 seconds, the elution amount of copper into the nitric acid bath was 0.0030 g / 25 cm ² or less, and the peel strength was good.
On the other hand, Comparative Examples 1 to 5 were all immersed in a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. with only the surface of the surface treatment layer exposed after heat treatment at 250 ° C. for 10 minutes. The amount of copper elution into the nitric acid bath exceeded 0.0030 g / 25 cm ² , and the peel strength was poor.

Claims (22)

Having a surface treatment layer formed of chromium oxide;
After heat treatment at 250 ° C. for 10 minutes, when immersed in a nitric acid bath having a concentration of 20 mass% and a temperature of 25 ° C. with only the surface of the surface treatment layer exposed, elution of copper into the nitric acid bath A surface-treated copper foil having an amount of 0.0030 g / 25 cm ² or less.   2. The surface-treated copper foil according to claim 1, wherein in the surface treatment layer, the amount of hexavalent chromium attached is 0.1% or less of the amount of trivalent chromium attached.   The surface-treated copper foil according to claim 1 or 2, wherein the surface-treated layer has a thickness of 0.1 to 2.5 nm.   The surface-treated copper foil in any one of Claims 1-3 in which the base layer was formed between the said copper foil and the said surface treatment layer.   The surface-treated copper foil of Claim 4 in which the said base layer contains a roughening process layer.   The surface-treated copper foil of Claim 4 or 5 in which the said base layer contains a heat discoloration prevention layer and / or a rust prevention layer.   The surface-treated copper foil according to claim 6, wherein the heat discoloration preventing layer and the rust preventing layer are Zn, Cu, or an alloy thereof, respectively.   The surface-treated copper foil of Claim 6 or 7 in which the said rust prevention layer contains a chromate layer or a zinc chromate layer.   The surface-treated copper foil in any one of Claims 4-8 in which the said foundation | substrate layer contains a silane coupling layer.   The surface-treated copper foil as described in any one of Claims 1-9 in which the silane coupling layer was formed on the said surface-treated layer.   The laminated body of the copper foil and resin substrate in any one of Claims 1-10.   The laminate according to claim 11, wherein the copper foil and the resin substrate are laminated without using an adhesive.   The printed wiring board which used the laminated body of Claim 11 or 12 as a material.   An electronic component comprising the printed wiring board according to claim 13. Step of providing a chromate solution on the entire processed surface of the copper foil, and, after providing the chromate bath on the copper foil surface, claim comprising the step of forming a surface treatment layer of chromium oxide by drying without water washing The manufacturing method of the surface treatment copper foil in any one of 1-10 .   In the step of forming the chromium oxide surface treatment layer, the chromium oxide surface treatment layer is formed by providing a chromate solution on the surface of the copper foil, then draining, and then drying without washing with water. 15. A method for producing a surface-treated copper foil according to 15. The amount provided the chromate solution to the copper foil surface, after the liquid cutting, a method for producing a surface-treated copper foil according to claim 16 which is 5 to 20 mg / dm ^2.   The method for producing a surface-treated copper foil according to claim 16 or 17, wherein the liquid draining is performed by spraying a roll, a blade and / or a gas. A step of providing a chromate solution over the entire surface of the copper foil to be treated, and a step of forming a chromium oxide surface treatment layer by drying without washing with water after the chromate solution is provided on the surface of the copper foil,
Step of providing the chromate bath on the entire processed surface of the copper foil, a manufacturing method of the row cormorants front surface treated copper foil by applying a shower chromate bath on the copper foil surface.   The method for producing a surface-treated copper foil according to any one of claims 15 to 18, wherein the step of providing the chromate solution over the entire surface to be treated of the copper foil is performed by applying the chromate solution to the surface of the copper foil with a roller.   The method for producing a surface-treated copper foil according to any one of claims 15 to 20, wherein the chromate solution has a pH of 1 to 10.   The method for producing a surface-treated copper foil according to claim 21, wherein the chromate solution has a pH of 4 to 10.