JP4941204B2 - Copper foil for printed wiring board and surface treatment method thereof - Google Patents

Description

The present invention relates to a copper foil for a printed wiring board that forms a glossy surface by subjecting a raw foil to a surface treatment, and a surface treatment method thereof, in particular, having a film excellent in heat discoloration resistance and acid solubility, The present invention relates to a copper foil for a printed wiring board in consideration of protection and a surface treatment method thereof.

  A printed wiring board is generally formed by bonding a copper foil and a base material such as a synthetic resin by thermocompression bonding to form a copper-clad laminate, and then printing a circuit using a photoresist to form a desired circuit, The circuit is formed by removing unnecessary copper portions by etching. The copper foil for printed wiring boards has a roughened surface that becomes an adhesive surface with a substrate and a glossy surface that becomes the surface of the wiring.

  Various surface treatments are performed on the roughened surface to ensure adhesion to the substrate, and to stabilize the adhesive properties such as heat resistance and chemical resistance, and etching properties in terms of adhesion to the substrate. Is granted.

  On the other hand, the glossy surface, which is the opposite side, requires heat discoloration resistance, solder wettability, resist adhesion, acid solubility, etc., and requires different treatment methods on the roughened surface side and the glossy surface side. It is being studied.

  In general, a glass epoxy base material, which is a rigid material, is used as a base material used for printed wiring boards. However, in recent years, printed circuit boards are thin and light, and bendability due to the small size and light weight of electronic devices. The demand for flexible substrates is excellent, and a polyimide base material is mainly used as the base material.

  When laminating a glass epoxy base material for a rigid substrate and a copper foil, it is thermocompression bonded at a temperature of 160 to 170 ° C. for 1 to 2 hours, but for a polyimide base material for a flexible substrate under a high temperature condition. Two-layer flexible (a polyimide substrate and a copper foil layer have a two-layer structure). In other words, heat discoloration resistance is one of the most important characteristics among the glossy surface side characteristics of the copper foil.

  In addition, copper foils have recently become thinner due to finer wiring, and after bonding the substrate and copper foil, the copper foil is dissolved with acid, so acid solubility is also an important characteristic. It has become.

  In the heat discoloration resistance, until now, it has been necessary to oxidize at a temperature of 200 to 250 ° C. for about 10 minutes. No heat discoloration resistance is required. On the other hand, for acid solubility, the dissolution rate of the surface treatment layer using an acid solution for copper is required to be equivalent to that of copper.

  The prior art document information related to the invention of this application includes the following.

Japanese Patent No. 2517503 Japanese Patent Laid-Open No. 10-135594 JP 2006-319287 A JP 2003-201585 A JP-A-9-87888 JP 2006-319286 A JP-A-2005-240132

  In general, in the treatment on the glossy surface side, the chromate treatment is performed by galvanizing, but this treatment has only heat discoloration resistance at 200 to 250 ° C. for about 10 minutes. Therefore, a surface treatment that does not change color even at a high temperature treatment of 300 ° C. for 30 minutes and has good acid solubility is required.

  Furthermore, the chromate treatment to be performed is a treatment using hexavalent chromium, and it is preferable that the chromate treatment is not used in an environmental problem that has become stricter in recent years.

  Therefore, the object of the present invention is to increase the heat discoloration resistance of the glossy surface of the copper foil so as not to cause discoloration even at a high temperature treatment of 300 ° C. and 30 minutes compared to the conventional galvanizing and chromate treatment, and the solubility in acid. Is to provide a copper foil for printed wiring boards and a surface treatment method thereof in consideration of the environment in which hexavalent chromium is not used.

The present invention has been devised to achieve the above object, and the invention of claim 1 is such that an alloy layer made of nickel and cobalt is formed on the surface of a raw foil, and a zinc layer and hexavalent chromium are formed thereon. In the copper foil for printed wiring boards, in which a glossy surface is formed by forming a rust preventive layer composed of a chromate layer formed without using an alloy, the alloy layer has a nickel adhesion amount of 0.5 μg / cm ² or more. 0 μg / cm ² or less, and the cobalt adhesion amount is 40% or more and 80% or less with respect to the total of the nickel adhesion amount and the cobalt adhesion amount, and as a result of forming the rust preventive layer thereon , 300 ° C. of the shiny side, 30 minutes for resistance to heat discoloration resistance to high-temperature heat treatment (JIS Z 8729) color difference with small have a resistance to thermal discoloration than 0.5 based on, and acid dissolution rate of the shiny side of copper The acid dissolution rate of the foil alone The copper foil for printed wiring boards is superior in heat discoloration resistance and acid solubility against high-temperature heat treatment on the glossy surface of the copper foil, characterized by having a value of about 90% or more.
In addition, said raw foil shall mean the copper foil of the state which has not performed any surface treatment etc. in this application.
In addition, the above color difference means that the copper foil is heat-treated at 300 ° C. for 30 minutes using a thermostatic bath, and the degree of discoloration before and after the treatment is determined by using a chromaticity meter, L ^* (brightness), a ^* (red-green axis chromaticity), b ^* (yellow-blue axis chromaticity) are measured, and based on (JIS Z 8729), ΔE ^* ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (ΔE ^* ab).
The above acid dissolution rate is determined from the weight measurement before and after dissolution in an etching solution mainly composed of hydrogen peroxide and sulfuric acid. ) Is a value of about 90% or more in comparison with the acid dissolution rate when etched with the same etching solution.

In the invention of claim 2, the zinc adhesion amount of the zinc layer is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, and the chromium adhesion amount of the chromate layer formed without using hexavalent chromium is 0. according to .3μg / cm ² or more 1.2 ug / cm ² or less is claim 1 is the copper foil for printed wiring boards that resistance to thermal discoloration and acid solubility was excellent for high-temperature heat treatment in the copper foil glossy surface .

In the invention of claim 3, after forming a rough plating layer on the back surface of the original foil, the alloy layer, the zinc layer, and the chromate layer formed without using the hexavalent chromium are sequentially formed on the original foil. The copper foil for printed wiring boards, which is formed simultaneously with the glossy surface of the surface and forms a roughened surface, wherein the copper foil glossy surface has excellent heat discoloration resistance and acid solubility against high-temperature heat treatment. It is.

In the invention of claim 4, an alloy layer made of nickel and cobalt is formed on the surface of the raw foil, and a rust prevention layer made of a zinc layer and a chromate layer formed without using hexavalent chromium is formed thereon. In the copper foil surface treatment method for forming a glossy surface, the alloy layer has a nickel adhesion amount of 0.5 μg / cm ^{2 to} 2.0 μg / cm ² and a cobalt adhesion amount of nickel adhesion. The mass ratio of 40% to 80% with respect to the total amount of cobalt and the amount of cobalt adhered, and as a result of forming the rust-preventing layer thereon, heat resistance to high-temperature heat treatment of the glossy surface at 300 ° C for 30 minutes the discoloration (JIS Z 8729) color difference with small have a resistance to thermal discoloration than 0.5 based on, and the glossy surface of the acid dissolution rate of approximately 90% or more as compared with an acid dissolution rate of the copper foil itself values Forming to have A surface treatment method for a copper foil for printed wiring boards, which is excellent in heat discoloration resistance and acid solubility against high-temperature heat treatment on a glossy surface of copper foil.

According to a fifth aspect of the invention, the alloy layer and the zinc layer are formed by electroplating , and the chromate layer formed without using the hexavalent chromium is formed by dipping with a trivalent chromate treatment solution. 4 is a surface treatment method for a copper foil for printed wiring boards, which is excellent in heat discoloration resistance and acid solubility against high-temperature heat treatment on the glossy surface of the copper foil.

The invention of claim 6, formed after the formation of the roughened plating layer on the back surface of the original foil, on the surface and the back surface of the original foil, the alloy layer, the zinc layer, and without using the hexavalent chromium and according to claim 4 or 5 to form a chromate layer sequentially at the same time, a method of surface treatment of copper foil for printed wiring boards that resistance to thermal discoloration and acid solubility was excellent for high-temperature heat treatment in the copper shiny side.

  According to the present invention, the glossy surface of the copper foil has heat discoloration resistance that does not change even when subjected to high-temperature heat treatment during the production of the printed wiring board, and the copper foil is thinned as the printed wiring board is refined. Therefore, it is possible to realize a copper foil for a printed wiring board having good acid solubility with respect to acid treatment for the purpose.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a copper foil for a printed wiring board showing a preferred embodiment of the present invention.

As shown in FIG. 1, the copper foil 1 for printed wiring boards which concerns on this embodiment forms the alloy layer 3 which consists of nickel and cobalt on the surface s1 of the original foil 2, and forms the zinc layer 4 and hexavalence on it. A glossy surface S is formed by forming a rust preventive layer composed of a chromate layer 5 formed without using chromium. The alloy layer 3 composed of nickel and cobalt has a nickel adhesion amount of 0.5 μg / cm ^2. above 2.0 [mu] g / cm ² or less, preferably 0.7 [mu] g / cm ² or more 2.0 [mu] g / cm ² or less, more desirably not more than 1.2 ug / cm ² or more 2.0 [mu] g / cm ^2, the cobalt coating weight The mass ratio is 40% or more and 80% or less, preferably 60% or more and 80% or less, and more preferably 65% or more and 80% or less with respect to the total amount of nickel adhesion and cobalt adhesion.

This is because when the nickel adhesion amount is less than 0.5 μg / cm ² , discoloration occurs due to high-temperature treatment (for example, heat treatment at 300 ° C. for 30 minutes), heat discoloration resistance deteriorates, and 2.0 μg / cm ² is reduced. This is because the surface color becomes gray and the solder wettability deteriorates.

  Further, if the cobalt adhesion amount is less than 40% with respect to the total of the nickel adhesion amount and the cobalt adhesion amount, the acid solubility deteriorates, and if the mass ratio exceeds 80%, the effect is not changed, which is uneconomical.

The alloy layer 3 made of nickel and cobalt improves heat discoloration resistance and moisture discoloration resistance, and at the same time has good acid solubility. Nickel and cobalt each have heat discoloration resistance and moisture discoloration resistance even with single plating, but the effect can be enhanced by using an alloy composed of nickel and cobalt. Further, the alloy layer 3 made of the nickel and cobalt, also functions as a barrier layer for preventing diffusion of copper atoms of the original foil 2, further the original foil 2 and the zinc layer 4 prevents alloying. Further, cobalt is considered to activate the reaction of polyimide, and when polyimide is used as a base material (not shown), there is also an effect of improving the adhesion with the base material on the roughened surface M.

As the raw foil 2, a rolled copper foil or an electrolytic copper foil (however, the copper foil here is synonymous with the original foil) may be used.

Further, the copper foil for printed wiring boards 1 according to the present embodiment, a zinc coating weight of the zinc layer 4 is 0.5 [mu] g / cm ² or more 2.0 [mu] g / cm ² or less was formed without using hexavalent chromium chromium deposition amount of the chromate layer 5 may is 0.3 [mu] g / cm ² or more 1.2 ug / cm ² or less.

This is because if the zinc adhesion amount of the zinc layer 4 is less than 0.5 μg / cm ^2, it does not play a role as a rust preventive layer, and it becomes difficult to control the chromium adhesion amount, and 2.0 μg / cm ² is reduced. This is because, when the printed wiring board is formed, zinc exposed to the circuit side surface by etching is easily eluted by hydrochloric acid or electroless tin plating solution during the manufacturing process. Electroless tin plating may be applied in the printed wiring board manufacturing process for the purpose of improving anticorrosion and solder wettability, etc. on the parts connected to other printed wiring boards and electronic components and soldered parts. is there.

Also, rust capacity and the amount of chromium deposited is less than 0.3 [mu] g / cm ² is insufficient, the formed chromate layer 5 is thick vulnerable without using hexavalent chromium exceeds 1.2 ug / cm ^2, Easy to peel.

The chromate layer 5 formed without using hexavalent chromium is preferably formed by dipping with a trivalent chromate treatment solution that does not contain harmful hexavalent chromium.

The zinc layer 4 assists the formation of the chromate layer 5 formed without using hexavalent chromium and functions as a rust preventive layer. The chromate layer 5 formed without using hexavalent chromium functions as a rust preventive layer. Provides corrosion resistance.

Moreover, in the copper foil 1 for printed wiring boards which concerns on this embodiment, after forming the rough plating layer 6 in the back surface s2 of the original foil 2, the alloy layer 33, the zinc layer 34, and hexavalent chromium which consist of nickel and cobalt The roughened surface M is formed by sequentially forming the chromate layer 35 formed without using . The rough plating layer 6 is formed in order to enhance the adhesiveness when the printed wiring board copper foil 1 and a base material (not shown) are bonded.

Furthermore, on the roughened surface M of the copper foil 1 for printed wiring boards, a silane coupling agent is applied on the chromate layer 35 formed without using hexavalent chromium , and this is dried to obtain a silane coupling treatment layer. 7 is formed. As the silane coupling agent, aminosilane or the like is preferably used when polyimide is used for the base material.

  Next, the surface treatment method of the copper foil for printed wiring boards according to the present embodiment will be described.

In the surface treatment method of the copper foil for printed wiring board according to the present embodiment, first, in order to clean the surface of the original foil 2, as a pretreatment, after cathodic electrolytic degreasing with an alkali solution such as sodium hydroxide or sodium carbonate, The acid treatment may be performed by dipping in an acid solution such as sulfuric acid.

After the pretreatment, the rough plating layer 6 is formed on the rough surface of the raw foil 2.

The roughened plating layer 6 may be formed, for example, by depositing granular copper on the roughened surface of the raw foil 2 by burn plating, or by performing selective etching of crystal grain boundaries using an acid.

Thereafter, alloy layers 3 and 33 made of nickel and cobalt are simultaneously formed on the front and back surfaces of the original foil 2 by electroplating (electrolytic plating).

  At this time, electroplating is performed using the plating apparatus 20 of FIG.

The plating apparatus 20 is an apparatus that performs electroplating on the surface of the original foil 2 to be plated, and includes a plurality of insoluble anode plates 22 (three in FIG. 2) and a plurality of conveyances that convey the original foil 21. And rolls 23 (three in FIG. 2), and electroplating is performed using the copper foil 2 as a cathode and the insoluble anode plate 22 as an anode.

  As the insoluble anode plate 22, for example, titanium, titanium alloy, platinum, platinum alloy, titanium plated with platinum, titanium with iridium oxide attached, or the like may be used.

  An example of the bath composition and processing conditions of the plating bath A for forming the alloy layers 3 and 33 made of nickel and cobalt is shown below.

Plating bath A
Nickel sulfate hexahydrate (NiSO ₄ .6H ₂ O): 150 to 200 g / L
Cobalt sulfate heptahydrate (CoSO ₄ .7H ₂ O): 20-30 g / L
Citric acid monohydrate (C ₆ H ₈ O ₇ .H ₂ O): 10 to 20 g / L
Liquid temperature: 35-45 degreeC
pH: 3.0-4.0
Current density Dk: 0.5 to 2.0 A / dm ²
Treatment time: 2 to 5 seconds After forming the alloy layers 3 and 33 composed of nickel and cobalt using the plating bath A, the zinc layers 4 and 34 are electroplated on the alloy layers 3 and 33 composed of nickel and cobalt. At the same time.

  An example of the bath composition and processing conditions of the plating bath B for forming the zinc layers 4 and 34 is shown below.

Plating bath B
Zinc sulfate heptahydrate (ZnSO ₄ .7H ₂ O): 80 to 100 g / L
Trisodium citrate _{(C 6 H 5 Na 3 O} 7): 15~25g / L
Liquid temperature: 15-25 ° C
pH: 3.0-4.0
Current density Dk: 0.3 to 2.0 A / dm ²
Treatment time: 2 to 5 seconds After forming the zinc layers 4 and 34 using the plating bath B, the chromate layers 5 and 35 formed without using hexavalent chromium by immersion treatment with a trivalent chromate treatment solution are simultaneously applied. Form.

An example of the bath composition and treatment conditions of the chromate treatment liquid C for forming the chromate layers 5 and 35 formed without using hexavalent chromium will be described below.

Chromate treatment liquid C
Chromium sulfate nonahydrate (Cr (SO ₄ ) ₃ · 9H ₂ O): 0.05 to 0.25 g / L
Nitric acid (HNO ₃ ): 2 to 20 g / L
Liquid temperature: 20-30 degreeC
pH: 3.0-4.0
Treatment time: 2 to 10 seconds After forming the chromate layers 5 and 35 formed without using hexavalent chromium using the chromate treatment liquid C, a silane coupling agent is applied on the chromate layer 35 on the roughened surface M. And this is dried and the silane coupling process layer 7 is formed.

  As described above, the printed wiring board copper foil 1 according to the present embodiment is obtained.

  When producing a printed wiring board using the copper foil 1 for printed wiring boards according to the present embodiment, the printed wiring board copper foil 1 is heat-pressed with the base material with the roughened surface M of the copper foil 1 for printed wiring board as the base material side, or printed. A polyimide varnish is directly applied to the roughened surface of the copper foil 1 for wiring boards, and the substrate and the copper foil 1 for printed wiring boards are bonded. Then, after printing the circuit by a photoresist on the glossy surface S of the copper foil 1 for printed wiring boards, it is good to form a circuit by removing an unnecessary copper part by an etching. Moreover, you may perform the process which melt | dissolves the copper foil 1 for printed wiring boards with an acid for refinement | miniaturization of wiring.

  The operation of this embodiment will be described.

In the copper foil 1 for printed wiring board according to the present embodiment, the nickel adhesion amount of the alloy layer 3 made of nickel and cobalt is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, and the cobalt adhesion amount is nickel. The mass ratio is 40% or more and 80% or less with respect to the total of the adhesion amount and the cobalt adhesion amount.

  Thereby, it can prevent that nickel adhesion amount runs short and heat-resistant discoloration resistance falls, for example, it can prevent discoloration also by 300 degreeC and a high temperature process for 30 minutes.

  Moreover, since it can prevent that the cobalt adhesion amount runs short and acid solubility falls, the favorable acid dissolution rate equivalent to copper can be obtained.

  Further, it is possible to prevent the nickel adhesion amount from being excessively high and the solder wettability from being deteriorated, and the cobalt adhesion amount from being excessive and uneconomical.

Further, the copper foil for printed wiring boards 1 according to the present embodiment, a zinc coating weight of the zinc layer 4 is 0.5 [mu] g / cm ² or more 2.0 [mu] g / cm ² or less was formed without using hexavalent chromium chromium deposition amount of the chromate layer 5 is set to 0.3 [mu] g / cm ² or more 1.2 ug / cm ² or less.

As a result, it is possible to prevent the zinc adhesion amount and chromium adhesion amount from being insufficient and prevent the function as a rust-preventing layer from being deteriorated, and the zinc adhesion amount is too large, so that the zinc of the zinc layer 4 is eluted or chromium adhesion occurs. It is possible to prevent the chromate layer 5 formed without using hexavalent chromium from being too much to be easily peeled off.

Moreover, in the surface treatment method of the copper foil for printed wiring boards which concerns on this embodiment, the chromate layer 5 formed without using hexavalent chromium is formed by immersing with a trivalent chromate treatment solution.

  Thereby, since harmful hexavalent chromium is not used, the burden on the environment can be reduced.

Furthermore, the surface treatment method of the copper foil for printed wiring boards which concerns on this embodiment forms the rough plating layer 6 in the back surface s2 of the original foil 2, Then, the alloy layers 3 and 33 which consist of nickel and cobalt, and the zinc layer 4 , 34, and chromate layers 5 and 35 formed without using hexavalent chromium are sequentially formed simultaneously.

Thereby, the plating process can be simultaneously performed on the front surface s1 and the back surface s2 of the raw foil 2, and the working time can be shortened.

  Moreover, according to the surface treatment method of the copper foil for printed wiring boards which concerns on this embodiment, the copper foil 1 for printed wiring boards which concerns on this embodiment can be produced easily.

The raw foil 2 was a rolled copper foil having a thickness of 18 μm. In order to clean the rolled copper foil surface, sodium hydroxide 40 g / L, sodium carbonate 20 g / L, cathodic electrolytic degreasing with an alkaline solution at a temperature of 40 ° C. with a current density of 5 A / dm ² and a treatment time of 30 seconds, and then sulfuric acid A pretreatment was performed with a 10% room temperature solution for 30 seconds.

A plating bath A adjusted to 175 g / L of nickel sulfate hexahydrate, 25 g / L of cobalt sulfate heptahydrate, 15 g / L of citric acid monohydrate, temperature of 40 ° C. and pH of 3.3 was used for the raw foil 2. Then, electrolytic treatment was performed at a current density of 0.8 A / dm ² for 3.5 seconds to give alloy layers 3 and 33 made of nickel and cobalt.

Subsequently, electrolysis is performed at a current density of 0.5 A / dm ² for 3.5 seconds using a plating bath B adjusted to 95 g / L of zinc sulfate heptahydrate, 20 g / L of trisodium citrate, a temperature of 25 ° C. and a pH of 3.2. The zinc layers 4 and 34 were applied after treatment.

  Next, a trivalent chromate treatment was performed by immersion treatment for 5 seconds using a chromate treatment liquid C adjusted to 0.2 g / L of chromium sulfate nonahydrate, 10 g / L of nitric acid, a temperature of 25 ° C., and a pH of 3.7.

The plating adhesion amount was measured with an induction plasma emission spectroscopic analyzer (ICP-AES) after dissolving the film in acid. As a result, the nickel coating weight of 1.2 ug / cm ^2, the cobalt adhesion amount 2.2μg / cm ^2, the zinc coating weight is 1.2 ug / cm ^2, the amount of chromium deposited is 0.8 [mu] g / cm ² Confirmed (Example 1).

  In Examples 2 to 8, the current density and bath composition were adjusted to change the nickel adhesion amount, the cobalt adhesion amount, and the mass ratio of nickel and cobalt in the alloy layers 3 and 33 made of nickel and cobalt. The copper foil 1 for printed wiring boards was produced similarly to 1.

  The characteristics of the glossy surface S of the obtained copper foil 1 for printed wiring boards were evaluated for the following items of heat discoloration resistance and acid solubility.

(1) Heat discoloration resistance Heat discoloration resistance is heat-treated at 300 ° C. for 30 minutes using a thermostatic bath, and the color change is evaluated using a color difference meter using L ^* (brightness), a ^* (red-green Axis chromaticity) and b ^* (yellow-blue axis chromaticity) were measured and evaluated based on (JIS Z 8729) by the color difference ΔE ^* ab shown in equation (1).

ΔE ^* ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (1)
The color difference is evaluated as shown in Table 1 based on the ΔE ^* ab value.

(2) Acid solubility The acid solubility is obtained by dissolving the copper foil 1 for printed wiring boards with a commercially available etchant (CPE700, manufactured by Mitsubishi Gas Chemical Co., Ltd.) mainly composed of hydrogen peroxide and sulfuric acid, and measuring the weight before and after the dissolution. More dissolution rate was measured. Evaluation was based on the dissolution rate of copper alone.

As a comparative example, when the nickel adhesion amount is less than 0.5 μg / cm ² in the nickel-cobalt alloy layer (Comparative Example 1), there is no alloy layer composed of nickel and cobalt, and only zinc plating and chromate treatment are performed (Comparative Example 2) Samples for the case of a nickel simple substance layer (Comparative Example 3) and a copper foil simple substance (= raw foil) (Comparative Example 4) were prepared and implemented instead of an alloy layer composed of nickel and cobalt. Evaluation similar to the example was performed.

  The test results are summarized in Table 2.

From the test results of Table 2, it can be seen that in Examples 1 to 8 according to the present invention, both heat discoloration resistance and acid solubility are good. On the other hand, in Comparative Example 1 in which the nickel adhesion amount is less than 0.5 μg / cm ² and Comparative Example 2 in which only the zinc plating and the chromate treatment are performed, the heat discoloration resistance is poor and only the nickel single layer has no cobalt. In Example 3, the acid solubility is poor. Furthermore, it turned out that Examples 1-8 are an acid dissolution rate substantially equivalent to the comparative example 4 which is copper foil single - piece | unit (= raw foil) .

Therefore, before the zinc plating and chromate treatment on the surface of the original foil, the nickel adhesion amount is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, and the cobalt adhesion amount is the nickel adhesion amount. By forming at a mass ratio of 40% or more and 80% or less with respect to the total amount of cobalt adhesion, it is not discolored with respect to a heat discoloration test at 300 ° C. for 30 minutes, and in terms of acid solubility, it is generally used as a barrier metal. It was confirmed that the acid solubility was superior to that of the known nickel coating, and that good acid solubility was obtained, equivalent to the raw material copper.

It is a cross-sectional view of the copper foil for printed wiring boards which shows suitable embodiment of invention. It is the schematic of the plating apparatus used for the surface treatment method of the copper foil for printed wiring boards which concerns on this embodiment.

DESCRIPTION OF SYMBOLS 1 Copper foil for printed wiring boards 2 Original foil 3 Alloy layer 4 Zinc layer 5 Chromate layer formed without using hexavalent chromium

Claims (6)

A glossy surface is formed by forming an alloy layer made of nickel and cobalt on the surface of the raw foil, and forming a rust preventive layer made of a zinc layer and a chromate layer formed without using hexavalent chromium on the alloy layer. In the copper foil for printed wiring boards, the alloy layer has a nickel adhesion amount of 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, and the cobalt adhesion amount is based on the total of the nickel adhesion amount and the cobalt adhesion amount. As a result of forming the rust-preventing layer thereon with a mass ratio of 40% to 80% , the heat discoloration resistance to high-temperature heat treatment of the glossy surface at 300 ° C. for 30 minutes (JIS Z 8729) based color difference with small have a resistance to heat discoloration resistance than 0.5, and the acid dissolution rate of the glossy surface is characterized by having a substantially 90% or more value than the acid dissolution rate of the original foil, copper foil High temperature heat treatment on glossy surfaces Copper foil for printed wiring boards with excellent heat discoloration resistance and acid solubility. The zinc adhesion amount of the zinc layer is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, and the chromium adhesion amount of the chromate layer formed without using the hexavalent chromium is 0.3 μg / cm ² or more and 1 .2μg / cm according ² to the is claim 1 below, copper foil for printed wiring boards that resistance to thermal discoloration and acid solubility was excellent for high-temperature heat treatment in the copper shiny side. After forming a rough plating layer on the back surface of the original foil, the alloy layer, the zinc layer, and the chromate layer formed without using the hexavalent chromium are sequentially formed simultaneously with the glossy surface on the surface of the original foil. The copper foil for printed wiring boards excellent in the heat discoloration resistance and acid solubility with respect to the high temperature heat processing in a copper foil glossy surface of Claim 1 or 2 which forms a roughened surface. A glossy surface is formed by forming an alloy layer made of nickel and cobalt on the surface of the raw foil, and forming a rust preventive layer made of a zinc layer and a chromate layer formed without using hexavalent chromium on the alloy layer. In the surface treatment method of the copper foil for printed wiring boards, the alloy layer has a nickel adhesion amount of 0.5 μg / cm ² or more and 2.0 μg / cm ² or less, a cobalt adhesion amount is a sum of the nickel adhesion amount and the cobalt adhesion amount. As a result of forming the rust-preventing layer thereon with respect to the mass ratio of 40% or more and 80% or less, the discoloration resistance to high-temperature heat treatment of the glossy surface at 300 ° C. for 30 minutes (JIS Z 8729) ) color difference with small have a resistance to thermal discoloration than 0.5 based on, and that the acid dissolution rate of the glossy surface is formed to have a substantially 90% or more value than the acid dissolution rate of the raw foil Characteristic, copper foil luster Surface treatment method of copper foil for printed wiring boards excellent in heat discoloration resistance and acid solubility against high temperature heat treatment on the surface. 5. The copper foil according to claim 4, wherein the alloy layer and the zinc layer are formed by electroplating , and the chromate layer formed without using the hexavalent chromium is formed by immersion treatment with a trivalent chromate treatment solution. A surface treatment method for a copper foil for printed wiring boards, which has excellent heat discoloration resistance and acid solubility against high-temperature heat treatment on a glossy surface. After the formation of the roughened plating layer on the back surface of the original foil, the on the front surface and the back surface of the original foil, the alloy layer, the zinc layer, and sequentially formed at the same time the chromate layer formed without using the hexavalent chromium The surface treatment method for a copper foil for printed wiring boards according to claim 4 or 5, wherein the copper foil glossy surface is excellent in heat discoloration resistance and acid solubility against high-temperature heat treatment.

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