JP5151761B2 - Method for producing rolled copper foil for printed wiring board - Google Patents

Description

  The present invention relates to a rolled copper foil for a printed wiring board having a roughened surface and a glossy surface, and in particular, locally on the glossy surface of the rolled copper foil for a printed wiring board after soft etching treatment. The present invention relates to a rolled copper foil for printed wiring boards, which has a film that prevents the occurrence of eroded dents and has excellent heat discoloration resistance and acid solubility, and a method for producing the same.

  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.

  On the roughened surface, various surface treatments are carried out to ensure adhesion to the substrate, and to stabilize adhesion and etching properties such as heat resistance and chemical resistance in adhesion to the substrate. Processing has been granted.

  On the other hand, the glossy surface which is the opposite surface is required to have heat discoloration resistance, solder wettability, resist adhesion, solubility during soft etching, surface uniformity, and the like.

  Therefore, different treatment methods are necessary and studied on the roughened surface side and the glossy surface side, respectively.

  In particular, rolled copper foils for printed wiring boards exhibit bending properties superior to electrolytic copper foils, such as mobile phone bent parts and slide parts, movable parts such as digital cameras and printers, and disks such as HDDs, DVDs, and CDs. Widely used as wiring material for movable parts of related equipment. In rolled copper foil, due to the thermal history when forming a copper clad laminate, the crystal grains grow large and there are few grain boundaries, and the crystal grains show high orientation, which causes cracks to develop during bending. Slow down and develop excellent bending properties.

  However, it cannot be denied that a portion having a different crystal orientation is locally generated instead of a complete single crystal state.

  Here, the characteristic requested | required by the glossy surface side of the copper foil for printed wiring boards is described in detail.

  Recently, the demand for flexible substrates that are particularly thin, light, and excellent in bendability is increasing for printed wiring boards due to the reduction in size and weight of electronic devices, and polyimide substrates are mainly used as substrates. When a glass epoxy base material for a rigid substrate is bonded to a copper foil, it is heat-pressed at a temperature of 160 to 170 ° C. for 1 to 2 hours, but it is bonded to a polyimide base material for a flexible substrate under a high temperature condition. In particular, a two-layer flexible film that does not use an adhesive (referred to as a two-layer flexible because a polyimide substrate and a copper foil layer have a two-layer structure by applying a polyimide varnish directly on a copper foil and forming a flexible substrate). ), The heat discoloration resistance is one of the most important characteristics among the glossy surface side characteristics of the copper foil. However, for the two-layer flexible film described above, heat discoloration resistance that does not cause oxidative discoloration even at 30 ° C. for 30 minutes is required. There.

  In addition, with the finer wiring, thinning of copper foil, ensuring adhesion with dry film resist during wiring formation, and using an acid solution consisting of hydrogen peroxide and sulfuric acid in the pretreatment of plating, a desired amount of soft Etching is performed. Soft etching requires solubility in an acid solution and surface uniformity.

  For acid solubility, it is necessary that the dissolution rate of the surface treatment layer should be equal to that of copper using an acid solution for copper.

  As for surface uniformity, in particular, in the rolled copper foil, in the part where the crystal orientation is partially different, the etching rate is different and the locally eroded dent (when soft etching is about 3 μm, the size is small. An erosion dent having a depth of 50 to 100 μm and a depth of 1 to 2 μm was generated. This resulted in a partial defect after the wiring was formed, and it was necessary to prevent the occurrence.

  Generally, in the processing on the glossy side of copper foil for printed wiring boards, chroming treatment is applied as a rust-proof layer by galvanizing directly on the copper foil material surface. An eroded dent is formed, and only exhibits heat discoloration resistance at 200 to 250 ° C. for about 10 minutes.

  Thus, as shown in Patent Document 4, a copper foil for printed wiring boards having a heat discoloration resistance at 300 ° C. for 30 minutes has been proposed by forming a copper plating layer on the surface of the copper foil. Moreover, as shown in Patent Document 3, a copper foil having good adhesive strength and flexibility has been proposed by applying a copper plating layer.

  Further, as disclosed in Patent Documents 1 and 2, it has been proposed to improve the surface of the glossy surface by etching the surface of the copper foil.

Japanese Patent Laid-Open No. 7-74464 JP 2004-238647 A JP 2007-19322 A Japanese Patent No. 311445

  However, a copper foil for printed wiring boards that satisfies both the prevention of the occurrence of locally eroded dents after the soft etching treatment and the resistance to heat discoloration has not been obtained.

  The object of the present invention is to prevent the formation of locally eroded dents during the soft etching process on the glossy surface side of the rolled copper foil, and without causing discoloration even at a high temperature treatment of 300 ° C. for 30 minutes. It is providing the copper foil for printed wiring boards with the favorable solubility with respect to a solution, and its manufacturing method.

The production method of the present invention is a method for producing a rolled copper foil for a printed wiring board in which it is essential to perform desired soft etching as a surface treatment in a later production process, and the rolled copper foil material used as a material On the glossy surface side, a copper plating layer having a thickness equal to or greater than the depth etched during the soft etching and formed by plating using an electrolytic plating bath is formed, and on the roughened surface side Forming a rough plating layer, and then forming an alloy layer made of nickel and cobalt, a zinc layer and a chromate layer on both the glossy surface side and the rough surface side in order , thickness of 0.1μm or more and 7μm or less, a nickel adhesion amount in the alloy layer made of the nickel and cobalt 0.5 [mu] g / cm ² or more, and 2.0 [mu] g / cm ² or less, with cobalt The amount of 40% or more with respect to the total nickel deposition amount and cobalt deposition amount, and 80% or less by weight, a zinc coating weight of the zinc layer 0.5 [mu] g / cm ² or more, and 2.0 [mu] g / cm ² or less the chromium add-on amount of the chromate layer 0.3 [mu] g / cm ² or more, 1.2 ug / cm ² or less and a manufacturing method of the printed wiring board rolled copper foil, characterized by.

Production method of the present invention, the thickness of the copper plating layer is 0.3 [mu] m or more, may Ru der below 7 [mu] m.
Here, the soft etching for making the surface of the rolled copper foil uniform may be performed by the thickness of the copper plating layer or the thickness of the copper plating layer or less. Or it is good to carry out so that a part of copper plating layer may remain after performing soft etching.

  According to the present invention, a copper plating layer having a thickness (0.1 μm or more and 7 μm or less) corresponding to the depth of soft etching is applied to the surface of the rolled copper foil material, and an alloy layer made of nickel and cobalt is formed thereon, zinc By forming a glossy surface consisting of a layer and a chromate layer, there is no dent that is locally eroded in the appearance after soft etching, and the copper foil for printed wiring boards that does not change color at 300 ° C for 30 minutes at high temperature Can be provided.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a detailed cross section of a copper foil A for printed wiring board according to the present invention.

  In FIG. 1, 10 is a rolled copper foil material, one of which is a glossy surface 11g and the other is a roughened surface 11r.

  On the rolled copper foil material 10 on the glossy surface 11g side, a copper plating layer 12, a nickel-cobalt alloy layer 13, a zinc layer 14, and a chromate layer 15 are formed in this order to form a glossy surface 11g. Is done. On the roughened surface 11r side, a roughened plated layer 16, an alloy layer 17 made of nickel and cobalt, a zinc layer 18 and a chromate layer 19 are sequentially formed to form the roughened surface 11r. When the alloy layer 17, the zinc layer 18 and the chromate layer 19 are formed on the rough plating layer 16, the alloy layer 13 on the glossy surface 11g side, the zinc layer 14, Plating may be performed simultaneously with the chromate layer 15.

  Furthermore, a silane coupling layer 20 is formed on the chromate layer 19 on the roughened surface 11r.

  Thus, in the present invention, a copper plating layer 12 having a thickness corresponding to the depth of soft etching is applied to the surface of the rolled copper foil material 10, and an alloy layer 13 made of nickel and cobalt is formed thereon, and further The zinc layer 14 and the chromate layer 15 are sequentially formed on the surface to form the glossy surface 11g, so that a locally eroded dent is not generated during the soft etching process, and the high temperature is 300 ° C. for 30 minutes. It can be set as the copper foil A for printed wiring boards which does not discolor also by a process and has the further favorable solubility with respect to an acid solution.

  The rolled copper foil material 10 as the copper foil used in the present invention is not particularly limited in terms of thickness, surface roughness and form.

  The copper plating layer 12 to be formed on the glossy surface 11g side of the rolled copper foil material 10 is plated using an electrolytic plating bath, and the plating thickness is applied only to the thickness by which the copper foil is soft-etched. However, in general, etching is often performed in a range of about 0.1 μm to 7 μm, and the copper plating layer 12 is desirably applied in a range of about 0.1 μm to 7 μm. Moreover, since the copper foil in which wiring is formed has a regulation of thickness, the total thickness of the rolled copper foil material 10 and the copper plating layer 12 is set to a desired copper foil thickness (18.1 μm to 25 μm). Composed.

  The copper plating layer 12 is not particularly limited to matte or bright plating, and the type of bath is not limited, but a general copper sulfate-sulfuric acid bath is recommended in terms of environment and handling.

  A plating bath composition for copper plating and an example of processing conditions are shown below.

Copper sulfate pentahydrate (CuSO ₄ .5H ₂ O): 100 to 250 g / L
Sulfuric acid (H ₂ SO ₄ ): 50 to 150 g / L
Liquid temperature: 30-50 degreeC
Current density Dk: 1 to 20 A / dm ²
Processing time: Processing time corresponding to the thickness (depth) of soft etching depending on the current density After the copper plating layer 12 is applied, an alloy layer 13 of nickel and cobalt is formed.

Alloy layer 13 of nickel and cobalt, nickel adhesion amount using an electrolytic plating bath at 0.5 [mu] g / cm ² or more ~2.0μg / cm ² or less, cobalt deposition amount in the total of the nickel deposition amount and cobalt deposition amount It is plated at a weight ratio of 40 to 80%.

If the nickel adhesion is less than 0.5 μg / cm ² , discoloration occurs due to high temperature treatment at 300 ° C. for 30 minutes, and the heat oxidation resistance deteriorates. If it exceeds 2.0 μg / cm ² , the surface color becomes gray and the solder This is not preferable because the wettability deteriorates. On the other hand, with respect to the cobalt adhesion amount, if the weight ratio is less than 40% with respect to the sum of the nickel adhesion amount and the cobalt adhesion amount, the acid solubility deteriorates, and if the weight ratio exceeds 80%, the effect does not change and is uneconomical. is there.

  An example of a plating bath composition and processing conditions for performing nickel-cobalt plating is shown below.

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
Dk: 0.5 to 2.0 A / dm ²
Treatment time: 2 to 5 seconds After the nickel-cobalt alloy plating layer 13 is applied, the zinc plating layer 13 is applied.

  An example of the plating bath composition and processing conditions for galvanizing is shown below.

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
Dk: 0.3 to 2.0 A / dm ²
Processing time: adhesion amount of 2-5 seconds zinc is desirably 0.5 [mu] g / cm ² or more ~2.0μg / cm ² or less. If the zinc adhesion amount is less than 0.5 μg / cm ^2, it does not serve as a rust prevention layer, and it becomes difficult to control the chromium adhesion amount, and if it exceeds 2.0 μg / cm ² , a printed wiring board is formed. This is because zinc exposed to the circuit surface by etching tends to be eluted by hydrochloric acid or electroless tin plating solution during the manufacturing process.

  After the galvanized layer 14 is applied, a trivalent chromate treatment is performed by dipping to form the chromate layer 15.

  An example of the bath composition and treatment conditions for chromate treatment is shown.

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: 2-10 seconds Chromium coating weight 0.3 [mu] g / cm ² or more ~1.2μg / cm ² or less in the range is desirable. Chromium coating weight is insufficient anticorrosive ability is less than 0.3 [mu] g / cm ^2, becomes 1.2 ug / cm ² by weight, the chromate layer 15 is thick brittle, consisting apt to be removed.

  Further, the roughened surface 11r is formed by forming a rough plated layer 16 on the back surface of the rolled copper foil material 10, and subsequently forming an alloy layer 17, a zinc layer 18 and a chromate layer 19 made of nickel and cobalt by plating. The chemical surface 11r is formed.

  The rough plating layer 16 is formed in order to enhance the adhesiveness when bonding the copper foil A for printed wiring board and the substrate.

  Further, as described above, the silane coupling layer 20 is formed on the roughened surface 11r by applying a silane coupling agent on the chromate layer 19 and drying it. As the silane coupling agent, aminosilane or the like is preferably used when polyimide is used for the base material.

Example 1
The material used 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 carried out with a 10%, room temperature solution by acid treatment for 30 seconds. This copper foil was subjected to electrolytic treatment for 90 seconds at a current density of 10 A / dm ² using a plating bath adjusted to 200 g / L of copper sulfate pentahydrate, 100 g / L of sulfuric acid, and a temperature of 40 ° C. to give a copper plating layer. The amount of copper plating adhered was determined by a gravimetric method and confirmed to be 3 μm.

Next, a plating bath (A) prepared by adjusting the copper foil 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 3.3. Was used for electrolytic treatment at a current density of 0.8 A / dm ² for 3 seconds to give an alloy layer made of nickel and cobalt.

Next, this copper foil was electrolyzed for 3 seconds at a current density of 0.5 A / dm ² using a plating bath adjusted to 95 g / L of zinc sulfate heptahydrate, 20 g / L of trisodium citrate, temperature of 25 ° C. and pH of 3.2. Treated to give a galvanized layer.

  Next, this copper foil was subjected to a trivalent chromate treatment by dipping for 5 seconds using a bath 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, confirmed that the amount of nickel deposited is 1.2 ug / cm ² of 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 It was done.

Examples 2-8
In Examples 2-8, copper plating with an adhesion thickness of 3.0 μm was performed on the surface of the copper foil material in the same manner as in Example 1, and nickel adhesion was achieved by adjusting the current density and bath composition of the nickel-cobalt alloy layer. The amount, the amount of cobalt adhesion, and the cobalt weight ratio were changed.

Examples 9-14
In Examples 9 to 14, copper plating with an adhesion thickness of 0.5 μm, 7.0 μm, 1.0 μm, 5.0 μm, 0.1 μm and 0.3 μm was performed on the surface of the copper foil material, respectively, and the nickel adhesion amount and cobalt The amount of adhesion and the weight ratio of cobalt were prepared in the same manner as in Example 8.

Comparative Examples 1-6
As a comparative example, when the copper plating on the copper foil material surface is not performed (Comparative Example 1), when the nickel adhesion amount is less than 0.5 μg / cm ² in the alloy layer of nickel and cobalt (Comparative Example 2), the zinc plating adhesion When the amount was less than 0.5 μg / cm ² and the chromium adhesion amount of the chromate layer was less than 0.3 μg / cm ² (Comparative Example 3), there was no nickel-cobalt alloy layer, and only zinc plating and chromate treatment were performed. In the case (Comparative Example 4), in the case of a nickel simple substance layer (Comparative Example 5) instead of the nickel-cobalt alloy layer, a sample in the case of a copper foil simple substance (Comparative Example 6) was prepared.

  The properties of the glossy surface of the obtained copper foil were evaluated for the following items of heat discoloration resistance and acid solubility.

(1) Evaluation of local dent occurrence after soft etching The evaluation of local dent occurrence after soft etching is based on a commercially available etchant (CPE700, Mitsubishi Gas, which mainly contains hydrogen peroxide and sulfuric acid as a soft etchant. (Chemical) was subjected to an etching treatment corresponding to the thickness of the copper plating, and the appearance after the treatment was observed using an SEM.
Local recesses after the soft etching are shown in FIGS. 2 (a) shows the SEM appearance of 100 times and FIG. 2 (b) shows the appearance of SEM of 500 times. When an etching process equivalent to 3 μm is performed, the size is 50 to 100 μm and the depth is about 1 to 2 μm. The presence or absence of a defective part of the erosion dent was observed.

(2) Heat discoloration resistance Heat discoloration resistance was measured by heat treatment at 300 ° C. for 30 minutes using a thermostatic bath, and color change was evaluated by measuring L ^* , a ^* , b ^* using a color difference meter ( The color difference (ΔE * ab) shown in the formula (1) was evaluated based on JIS Z 8729).

ΔE ^* ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (1)
According to JIS Z 8729, the color difference is evaluated as shown in Table 1 based on the ΔE ^* ab value.

(3) Acid solubility The acid solubility was determined by dissolving copper foil with a commercially available etching solution (CPE700, manufactured by Mitsubishi Gas Chemical Co., Ltd.) mainly composed of hydrogen peroxide and sulfuric acid, and measuring the dissolution rate by weight measurement before and after dissolution. . Evaluation was based on the dissolution rate of copper alone.

  Examples 1 to 14 and Comparative Examples 1 to 6 and evaluations are shown in Table 2.

  From the test results of Table 2, it can be seen that in Examples 1 to 14 according to the present invention, there is no uneven erosion locally eroded after soft etching, and both heat discoloration resistance and acid solubility are good.

On the other hand, when copper plating is not performed on the surface of the rolled copper foil (Comparative Example 1), dent unevenness that was locally eroded after soft etching was confirmed, and the nickel adhesion amount was less than 0.5 μg / cm ² (Comparison Example 2), zinc adhesion less than 0.5 μg / cm ² and chromium adhesion less than 0.3 μg / cm ² (Comparative Example 3), only with zinc plating and chromate treatment (Comparative Example 4) heat discoloration resistance However, when only nickel simple substance layer does not contain cobalt (Comparative Example 5), the acid dissolution rate is poor.

  Furthermore, in Examples 1-14, it turned out that it is an acid dissolution rate substantially equivalent to the comparative example 6 which is copper foil single-piece | unit.

From the above results, a copper plating layer having a thickness corresponding to the depth of soft etching is applied to the surface of the rolled copper foil material, and an alloy layer made of nickel and cobalt is formed thereon with a nickel adhesion amount of 0.5 μg / cm ² or more to 2.0 μg / cm ² or less, the amount of cobalt deposited is 40 to 80% of the total amount of nickel deposited and cobalt deposited, and the amount of zinc deposited on the zinc layer is 0.5 μg / cm further the configuration of the copper foil shiny side of chromium coating weight is made of 0.3 [mu] g / cm ² or more ~1.2μg / cm ² or less of the chromate layer thereon at least ^two ~2.0μg / cm ² or less, after the soft etching In the appearance of the material, there is no locally eroded dent, it is not discolored by high-temperature treatment at 300 ° C. for 30 minutes, and the acid solubility is superior to the nickel coating generally known as a barrier metal. Are shown, it is possible to provide a copper foil for printed wiring boards obtained good acid solubility equivalent to copper.

It is a cross-sectional view which shows one Embodiment of the copper foil for printed wiring boards of this invention. It is a local dent SEM external view after a soft etching process.

Explanation of symbols

10 Rolled copper foil material 11g Glossy surface 11r Roughened surface 12 Copper plating layer 13 Alloy layer made of nickel and cobalt 14 Zinc layer 15 Chromate layer

Claims (2)

It is a manufacturing method of a rolled copper foil for printed wiring boards that is required to perform a desired soft etching as a surface treatment in a subsequent manufacturing process,
A copper plating layer having a thickness equal to or greater than the depth etched during the soft etching on the glossy surface side of the rolled copper foil material that is the material and formed by plating using an electrolytic plating bath Then, a rough plating layer is formed on the rough surface side, and then an alloy layer made of nickel and cobalt, a zinc layer, and a chromate layer are sequentially formed on both sides of the gloss surface and the rough surface. Forming ,
The thickness of the copper plating layer is 0.1 μm or more and 7 μm or less, and the nickel adhesion amount in the alloy layer made of nickel and cobalt is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less. The amount is 40% or more and 80% or less with respect to the total of nickel adhesion and cobalt adhesion, and the zinc adhesion amount of the zinc layer is 0.5 μg / cm ² or more and 2.0 μg / cm ² or less. the chromium add-on amount of the chromate layer 0.3 [mu] g / cm ² or more, 1.2 ug / cm ² or less and a manufacturing method of the printed wiring board rolled copper foil, characterized by. The thickness of the copper plating layer is 0.3 [mu] m or more, a method for manufacturing a printed wiring board for rolled copper foil according to Der Ru請 Motomeko 1 below 7 [mu] m.