Composite metal foil and method for producing the same

Abstract

To provide a composite metal foil in which a second copper layer is laminated on a nickel layer and which can be suitably used for a printed wiring board because a circuit can be formed by selective etching, the contrast between different kinds of metals is clear and can be easily identified, and erroneous detection and detection omission of a circuit pattern in image inspection and displacement in the case of multilayering hardly occur.SOLUTION: A composite metal foil comprising at least one layer structure of a first copper layer / a nickel layer / a second copper layer, wherein an absolute value of a difference between a lightness L * Cu value of a surface of the second copper layer and a lightness L * Ni value of a surface of the nickel layer on which the second copper layer is laminated is 15 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite metal foil, specifically a composite metal foil having a nickel layer and a second copper layer laminated thereon, which allows for the formation of circuits by selective etching and provides clear and easily distinguishable contrast between different metals, thereby reducing the risk of erroneous or missed detection of circuit patterns in image inspections and reducing positional deviations when multilayering, making the foil suitable for use in printed wiring boards. [Background technology]

[0002] Printed wiring boards are used in electronic devices and are generally manufactured using copper foil by subtractive or additive processes.

[0003] Manufacturing methods for printed wiring boards have become more diverse depending on the characteristics required of the boards. As described in Patent Documents 1 and 2 below, manufacturing methods have been developed that use composite metal foils made of different metals and selectively etch each metal (hereinafter referred to as "selective etching"), as well as manufacturing methods that use selective etching solutions that can selectively etch each metal.

[0004] In the manufacturing process of printed wiring boards, it is necessary to accurately identify circuit patterns, such as through-hole and via positioning, by image inspection (AOI inspection) of the circuit pattern and when multi-layering.

[0005] However, conventional composite metal foils have problems such as unclear contrast between different metals, making it difficult to accurately identify circuit patterns using image inspection, which can lead to false detections, missed detections, and misalignment of circuit patterns when layered.

[0006] Therefore, there is a need for the development of a composite metal foil that can be used for printed wiring boards, in which circuits can be formed by selective etching, has clear contrast between different metals, and allows circuit patterns to be accurately identified by image inspection, making it less likely to cause false detection, missed detection, or misalignment when layered. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2002-359471 [Patent Document 2] Patent Publication No. 2014-063950 [Patent Document 3] WO2012-132573 [Patent Document 4] Patent Publication No. 7-221449 Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 3 describes a composite copper foil made of copper / nickel / copper, on which a circuit can be formed by selective etching.

[0009] Patent Document 4 describes a method for manufacturing a multilayer wiring board using a dissimilar metal foil having a nickel layer or a nickel alloy layer between a first copper layer and a second copper layer.

[0010] However, the composite copper foil described in Patent Document 3 and the dissimilar metal foil described in Patent Document 4 do not have a clear contrast between the copper layer and the nickel layer, which may result in false detection or missed detection in image inspection, or in misalignment of the circuit pattern when multi-layering.

[0011] The inventors of the present invention have set solving the above-mentioned problems as a technical task, and as a result of numerous trial and error trials and experiments, have discovered a composite metal foil comprising a first copper layer and a nickel layer laminated on at least one surface of the first copper layer, and a second copper layer laminated on the nickel layer, and wherein the lightness L of the surface of the second copper layer as defined in JIS-Z8781-4 is * Value: Lightness L * Cu value, the lightness L of the nickel layer surface on which the second copper layer is laminated *Value: Lightness L * Ni Lightness L when set as a value * Cu Value and Lightness L * Ni The above technical object was achieved by finding that a composite metal foil in which the absolute value of the difference between the first copper layer and the second nickel layer is 15 or more allows a circuit to be formed by selective etching, and the contrast between the second copper layer and the nickel layer is clear and easy to distinguish, making it less likely to cause erroneous detection or missed detection of the circuit pattern in image inspection, and less likely to cause misalignment when multi-layered, resulting in a composite metal foil that can be suitably used for printed wiring boards. [Means for solving the problem]

[0012] The above technical problems can be solved by the present invention as follows.

[0013] The present invention provides a composite metal foil comprising a first copper layer and a nickel layer laminated on at least one surface of the first copper layer, and a second copper layer laminated on at least one surface of the nickel layer, wherein the lightness L of the surface of the second copper layer as defined in JIS-Z8781-4 is * Value: Lightness L * Cu value, the lightness L of the nickel layer surface on which the second copper layer is laminated * Value: Lightness L * Ni Lightness L when set as a value * Cu Value and Lightness L * Ni The absolute value of the difference between the values ​​is 15 or more.

[0014] The present invention also provides a method for manufacturing a thermoplastic resin having the above-mentioned lightness L * Cu Value - the lightness L * Ni The composite metal foil has a value of 15 or more.

[0015] The present invention also provides a method for manufacturing a thermoplastic resin having the above-mentioned lightness L * Ni The composite metal foil has a value of 57 or less.

[0016] The present invention also relates to the composite metal foil, wherein the nickel layer is a nickel layer provided with a roughening treatment layer made of nickel particles having an average particle size of 3 μm or less on the second copper layer side.

[0017] The present invention also relates to the composite metal foil, wherein the nickel layer surface has a ten-point average roughness Rzjis of 5 μm or less.

[0018] The present invention also provides a method for manufacturing a nickel-based electrolytic capacitor having a nickel layer with a nickel purity of 99.6% by weight or more and a square meter weight of 2.7 g / m 2 or more, and 27g / m 2 The composite metal foil is as follows:

[0019] The present invention also relates to the composite metal foil, wherein at least a portion of the surface of the first copper layer or the second copper layer on which the nickel layer is not laminated is surface-treated.

[0020] The present invention also relates to the composite metal foil described above, which is for use in a printed wiring board.

[0021] The present invention also provides a method for producing the composite metal foil, comprising the steps of: forming the first copper layer; laminating the nickel layer on at least one surface of the first copper layer; and laminating a second copper layer on at least one surface of the laminated nickel layer.

[0022] The present invention also provides the method for producing a composite metal foil, wherein the laminating step is electroplating. [Effects of the Invention]

[0023] The composite metal foil of the present invention is a composite metal foil having at least one layer structure of a first copper layer / nickel layer / second copper layer, and is a composite metal foil in which a circuit can be formed by selectively etching the second copper layer.

[0024] Also, the lightness of the second copper layer L * Cu Value and lightness of nickel layer L * NiSince the absolute value of the difference in values ​​is 15 or more, the contrast between different metals is clear and easy to distinguish, so erroneous detection or detection failure of circuit patterns in image inspection and misalignment when multi-layering are unlikely to occur, making this a composite metal foil that can be suitably used for printed wiring boards.

[0025] Especially the lightness L * Cu Value-Lightness L * Ni If the value is 15 or more, the contrast between the different metals can be made clear by lowering the brightness of the nickel layer, and there is no need to apply any treatment to the surface of the second copper layer to lower the brightness, resulting in a composite metal foil that is not at risk of reducing selectivity or removability in selective etching.

[0026] Also, the brightness L * Cu Value-Lightness L * Ni When the value is 15 or more, the lightness L * Ni A value of 57 or less will make the nickel layer appear sufficiently dark to provide a clearer contrast with the second copper layer.

[0027] In addition, if the nickel layer is a nickel layer consisting of a nickel layer and a roughened layer made of nickel particles, the brightness L * Ni The value is low, the contrast between the different metals is clear, and the anchoring effect of the nickel particles results in a composite metal foil with excellent adhesion between the nickel layer and the second copper layer.

[0028] Furthermore, if the ten-point average roughness Rzjis of the nickel layer surface is 5 μm or less and the average particle size of the nickel particles is 3 μm or less, the resulting composite metal foil will have better adhesion and will be able to form circuits with excellent circuit shape precision.

[0029] In addition, the nickel layer has a nickel purity of 99.6% by weight or more and a square meter weight of 2.7 g / m 2 or more, and 27g / m 2If the thickness is less than this, the composite metal foil will have excellent selectivity and removability by selective etching.

[0030] Therefore, with the composite metal foil of the present invention, circuits can be formed using common methods such as subtractive methods and additive methods, and erroneous detection or missed detection of circuit patterns during image inspection, as well as misalignment when multi-layering, are less likely to occur. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a schematic diagram of one embodiment of a composite metal foil according to the present invention. [Figure 2] 1 is a schematic diagram of one embodiment of a composite metal foil according to the present invention. [Figure 3] 1 is a schematic diagram of one embodiment of a composite metal foil according to the present invention. [Figure 4] 1 is a schematic diagram of one embodiment of a composite metal foil according to the present invention. [Figure 5] 1 is an SEM image (5000x magnification) of a roughened layer in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0032] The composite metal foil of the present invention is a composite metal foil having at least one layer structure of a first copper layer (20) / a nickel layer (30) / a second copper layer (40).

[0033] (First copper layer) The first copper layer (20) in the present invention is not particularly limited, and copper foil formed by rolling or electrolysis or copper alloy foil can be suitably used.

[0034] The first copper layer may be a copper foil or copper alloy foil that has been subjected to a release treatment so that the front and back surfaces can be separated in the thickness direction.

[0035] The thickness of the first copper layer is not particularly limited and may be appropriately selected depending on the intended use, but is preferably 9 μm to 300 μm, more preferably 12 μm to 105 μm.

[0036] If the thickness is less than 9 μm, wrinkles and cracks may occur when the nickel layer is laminated, and if it exceeds 300 μm, the overall rigidity of the composite metal foil may become too strong, making it difficult to handle.

[0037] (nickel layer) The composite metal foil of the present invention has a nickel layer (30) laminated on a first copper layer (20).

[0038] The nickel layer (30) may be a nickel coating layer (30a) only (FIG. 1), or may have a roughened layer (30b) made of nickel particles on the nickel coating layer (30a) (FIG. 2).

[0039] In this specification, the term nickel layer (30) is used to mean both a nickel layer consisting of only a nickel coating layer (30a) and a nickel layer having a roughened layer (30b) made of nickel particles on the nickel coating layer (30a).

[0040] The surface on which the nickel layer (30) is laminated may be either one surface or both surfaces of the first copper layer, and may be appropriately selected as required.

[0041] The surface of the first copper layer on which the nickel layer (30) is not laminated may be subjected to a surface treatment.

[0042] The surface treatment is not particularly limited, and examples thereof include roughening treatment, heat resistance / chemical resistance treatment, rust prevention treatment, and chemical conversion treatment.

[0043] When the brightness of the nickel layer (30) surface is lower than that of the second copper layer surface, the brightness L of the nickel layer surface is * Ni The value is preferably 57 or less, more preferably 53 or less.

[0044] Lightness L * Ni If the value exceeds 57, the lightness L of the nickel layer (30) and the second copper layer *This is because the difference in values ​​is unlikely to be 15 or more, which may make it difficult to accurately identify the circuit pattern during image inspection.

[0045] The nickel layer (30) of the present invention may have a roughened layer (30b) made of nickel particles on a nickel coating layer (30a).

[0046] By providing the roughened layer (30b) made of nickel particles, the brightness L * Ni This is because the value becomes lower, the contrast with the second copper layer becomes clearer, and the anchor effect results in a composite metal foil with excellent adhesion between the nickel layer and the second copper layer.

[0047] The average particle size of the nickel particles in the roughened layer is preferably 3 μm or less, and more preferably 2 μm or less.

[0048] If the average particle size exceeds 3 μm, the contrast between different metals becomes unclear, which may make it difficult to accurately identify circuit patterns during image inspection.

[0049] Furthermore, if the average particle size exceeds 3 μm, the unevenness becomes too large, which may cause poor adhesion between the nickel layer (30) and the second copper layer and may deteriorate the precision of the circuit shape.

[0050] The ten-point average roughness Rzjis of the surface of the nickel layer (30) on which the second copper layer is laminated, measured in accordance with JIS-B0601 (2013), is preferably 5 μm or less, more preferably 3 μm or less.

[0051] If the ten-point average roughness Rzjis of the surface of the nickel layer (30) exceeds 5 μm, the unevenness becomes too large, which may cause poor adhesion between the nickel layer and the second copper layer or deteriorate the precision of the circuit shape.

[0052] In the present invention, the nickel purity of the nickel layer (30) is preferably 99.6% by weight or more.

[0053] If the purity of nickel is low, the selectivity and removability of the selective etching may decrease.

[0054] The square meter weight of the nickel layer (30) in the present invention is 2.7 g / m 2 ~27g / m 2 is preferred, and more preferably 4.5 g / m 2 ~18g / m 2 is.

[0055] 2.7g / m 2 If it is less than 27 g / m, the selectivity of the selective etching may be reduced. 2 Even if the thickness exceeds this value, no further improvement in performance can be expected, and the time required for selective etching increases.

[0056] The method for forming the nickel layer (30) is not particularly limited, but it is preferably formed by electrolysis.

[0057] This is because the electrolytic method can achieve a nickel purity of 99.6% by weight or higher.

[0058] (nickel coating layer) The plating bath used when forming the nickel coating layer (30a) of the present invention by electrolysis is not particularly limited, but may be a Watts bath (nickel sulfate 240 g / L to 300 g / L, nickel chloride 40 g / L to 70 g / L, boric acid 30 mL / L to 45 mL / L, pH 3.8 to pH 4.2, bath temperature 50°C to 60°C, current density 0.5 A / dm 2 ~8A / dm 2 ) or sulfamic acid bath (nickel sulfamate 440g / L-500g / L, boric acid 30mL / L-50mL / L, pH 3.8-4.4, bath temperature 50℃-60℃, current density 2A / dm 2 ~40A / dm 2 The first copper layer can be immersed in the nickel coating layer (30a) and electroplated to form a nickel coating layer (30a) on the first copper layer.

[0059] If necessary, brighteners, sodium naphthalenesulfonate, sodium dodecyl sulfate, saccharin, and known plating bath additives such as those disclosed in Japanese Patent Application Laid-Open No. 55-62188 may be added to the Watts bath or sulfamic acid bath.

[0060] (roughened layer) The roughened layer (30b) made of nickel particles can be formed on the nickel coating layer (30a) by using a Watts bath or a sulfamic acid bath as a plating bath, for example, according to the method disclosed in Japanese Patent Laid-Open Publication No. 24929 / 1973.

[0061] After the roughening treatment layer is formed, a particle coating treatment may be carried out to prevent the roughening particles from falling off.

[0062] (Second copper layer) The composite metal foil of the present invention has a second copper layer laminated on a nickel layer.

[0063] The thickness of the second copper layer is not particularly limited, but is preferably 1 μm to 70 μm.

[0064] The surface of the second copper layer opposite to the nickel layer may be subjected to a surface treatment.

[0065] The surface treatment is not particularly limited, and examples thereof include roughening treatment, heat resistance / chemical resistance treatment, rust prevention treatment, and chemical conversion treatment.

[0066] The method for forming the second copper layer is not particularly limited, but may be a copper sulfate-sulfuric acid bath (copper sulfate pentahydrate 100 g / L to 300 g / L, sulfuric acid 50 g / L to 200 g / L, bath temperature 20°C to 50°C, current density 2 A / dm 2 ~60A / dm 2 ) and electroplating to form a second copper layer on the nickel layer.

[0067] Additives may be added to the plating bath used when forming the second copper layer by electroplating.

[0068] An example of an additive is gelatin.

[0069] In the composite metal foil of the present invention, the lightness L of the surface of the second copper layer specified in JIS-Z8781-4 * Value: Lightness L * Cu The lightness of the nickel layer surface on which the second copper layer is laminated is the lightness L * Ni When the value is * Cu Value and Lightness L * Ni The absolute value of the difference between the values ​​is preferably 15 or more, more preferably 20 or more.

[0070] If the absolute value of the difference in lightness L value is less than 15, the contrast between the nickel layer and the second copper layer will not be clear, which may make it difficult to accurately identify the circuit pattern through image inspection or may cause the pattern to be misaligned when multi-layered. [Example]

[0071] Examples and comparative examples of the present invention are shown below, but the present invention is not limited to these.

[0072] (Examples 1 to 11) The first copper layer was made of electrolytic copper foil with a thickness of 70 μm.

[0073] The first copper layer was immersed in Watts bath A (bath composition: nickel sulfate 250 g / L, nickel chloride 50 g / L, boric acid 30 mL / L, pH 4.0, bath temperature 50°C) and treated under the conditions shown in Table 1 to form a nickel coating layer.

[0074] The surface on which the nickel coating layer was formed was immersed in Watts bath B (bath composition: nickel sulfate 50 g / L, nickel chloride 20 g / L, boric acid 30 mL / L, pH 4.0, bath temperature 50°C) and treated under the conditions shown in Table 1, and then immersed in Watts bath A under the conditions shown in Table 1 to form a roughened layer made of nickel particles.

[0075] The surface on which the roughened layer was formed was immersed in a copper sulfate-sulfuric acid bath (bath composition: copper sulfate pentahydrate 250 g / L, sulfuric acid 100 g / L, bath temperature 40°C) at a current density of 5 A / dm 2 for 18 minutes to form a second copper layer on the roughened layer.

[0076] Example 12 The same procedure as in Example 11 was repeated except that 30 ppm of chloride ions and 1.5 ppm of gelatin were added to the copper sulfate-sulfuric acid bath in which the second copper layer was formed.

[0077] Example 13 The same procedure as in Example 11 was repeated, except that 30 ppm of chloride ions, 100 ppm of polyethylene glycol, and 5 ppm of disodium bis-3-sulfopropyl disulfide were added to the copper sulfate-sulfuric acid bath used to form the second copper layer.

[0078] Example 14 As the first copper layer, a 70 μm thick electrolytic copper foil (drum surface) was used, and the first copper layer was immersed in a bath prepared by adding 30 g / L of L-cysteine ​​to Watts bath A at a current density of 5 A / dm 2 After forming a nickel coating layer by treating with 120 seconds, the surface on which the nickel coating layer was formed was immersed in a sulfuric acid-copper sulfate bath at a current density of 5 A / dm 2 for 18 minutes to form a second copper layer on the nickel layer.

[0079] Example 15 As the first copper layer, an electrolytic copper foil (drum surface) with a thickness of 70 μm was used.

[0080] The first copper layer was immersed in a Watts bath (bath composition: nickel sulfate 250 g / L, nickel chloride 50 g / L, boric acid 30 mL / L, pH 4.0, bath temperature 50°C) at a current density of 5 A / dm 2 The nickel coating layer was formed by treating with 120 seconds.

[0081] The surface on which the nickel layer was formed was immersed in a copper sulfate-sulfuric acid bath (bath composition: copper sulfate pentahydrate 250 g / L, sulfuric acid 100 g / L, bath temperature 40°C) at a current density of 5 A / dm 2 for 18 minutes to form a second copper layer on the nickel coating layer.

[0082] The surface on which the second copper layer was formed was immersed in a bath containing 40 g / L of copper sulfate pentahydrate, 100 g / L of pentasodium diethylenetriaminepentaacetate, pH 4.3, and a bath temperature of 40°C, at a current density of 2.0 A / dm 2 for 20 seconds to form a surface treatment layer with low brightness on the second copper layer.

[0083] (Comparative Examples 1 and 2) The same procedure as in Example 1 was followed, except for the items listed in Table 1 and the fact that the roughening treatment layer was not formed.

[0084] (surface roughness) The ten-point average roughness Rzjis of the nickel layer surface before forming the second copper layer was measured using a surface roughness measuring instrument SE-600 (manufactured by Kosaka Laboratory Co., Ltd.) in accordance with JIS-B0601 (2013).

[0085] (Lightness L * value) The nickel layer before the formation of the second copper layer and the second copper layer were measured for brightness L as specified in JIS-Z8781-4 using a spectrophotometer CM-600d (manufactured by Konica Minolta, Inc.). * Ni Value, Lightness L * Cu After measuring the values, the absolute value of the difference in brightness was calculated.

[0086] (Binarization possibility) A portion of the second copper layer was removed with a selective copper etchant to expose the nickel layer, and an image of the boundary between the exposed nickel layer and the second copper layer was taken and binarized using the Threshold function of the image processing software ImageJ. Those that could be binarized were evaluated as ◯, and those that could not be binarized were evaluated as ×.

[0087] Table 1 shows the production conditions for each example and comparative example, and Table 2 shows the evaluation results.

[0088] [Table 1]

[0089] [Table 2]

[0090] In Examples 1 to 13, the average particle size of the roughening particles was 3 μm or less.

[0091] In Example 14, the brightness of the nickel layer alone was significantly reduced compared to Comparative Example 1.

[0092] In Comparative Examples 1 and 2, the contrast was not clear and binarization was not possible.

[0093] In particular, in Comparative Example 2, the interface between the nickel layer and the second copper layer was made extremely rough, but the contrast did not become clear.

[0094] The items listed in Table 2 prove that the composite metal foil of the present invention has a clear contrast between the nickel layer and the second copper layer and can be binarized, making it easy to identify the circuit pattern. [Industrial Applicability]

[0095] The composite metal foil of the present invention has a second copper layer laminated on a nickel layer, so that circuits can be formed by selective etching. Also, the brightness L * Cu Value and Lightness L * Ni The absolute value of the difference between the measured value and the measured value is 15 or more, and the contrast between the second copper layer and the nickel layer is clear and easy to distinguish. Therefore, erroneous detection or missed detection of circuit patterns in image inspection and misalignment when multi-layering are unlikely to occur, making this a composite metal foil that can be suitably used for printed wiring boards. Therefore, the present invention has a high industrial applicability. [Explanation of symbols]

[0096] 10 Composite metal foil 20 First copper layer 30 nickel layer 30a Nickel coating layer 30b Roughened layer made of nickel particles 40 Second copper layer

Claims

1. A composite metal foil comprising a first copper layer and a nickel layer laminated on at least one surface of the first copper layer, and a second copper layer laminated on the nickel layer, wherein the lightness L of the surface of the second copper layer as defined in JIS-Z8781-4 is ＊ Value: Lightness L ＊ Ｃｕ value, the lightness L of the nickel layer surface on which the second copper layer is laminated ＊ Value: Lightness L ＊ Ｎｉ The lightness L when the value ＊ Ｃｕ Value and Lightness L ＊ Ｎｉ The absolute value of the difference between the values ​​is 15 or more.

2. The lightness L ＊ Ｃｕ Value - the lightness L ＊ Ｎｉ 2. The composite alloy according to claim 1, wherein the value is 15 or more. Genus foil.

3. The lightness L ＊ Ｎｉ 3. The composite metal foil according to claim 2, wherein the value is 57 or less.

4. 3. The composite metal foil according to claim 1, wherein the nickel layer is a nickel layer having a roughening treatment layer on the copper second layer side, the roughening treatment layer being made of nickel particles having an average particle size of 3 μm or less.

5. 3. The composite metal foil according to claim 1, wherein the ten-point average roughness Rzjis of the surface of said nickel layer is 5 μm or less.

6. 5. The composite metal foil according to claim 4, wherein the ten-point average roughness Rzjis of the surface of said nickel layer is 5 μm or less.

7. The nickel layer has a nickel purity of 99.6% by weight or more and a square meter weight of 2.7 g / m ２ or more, and 27 g / m ２ 3. The composite metal foil according to claim 1, wherein:

8. 3. The composite metal foil according to claim 1, wherein at least a portion of the surface of said first copper layer or said second copper layer, which is not covered with said nickel layer, is surface-treated.

9. 3. The composite metal foil according to claim 1, which is for use in a printed wiring board.

10. forming the first copper layer; depositing the nickel layer on at least one surface of the first copper layer; The method for producing a composite metal foil according to claim 1 or 2, further comprising the step of laminating a second copper layer on at least one surface of the laminated nickel layer.

11. The method for producing a composite metal foil according to claim 10, wherein the laminating step is electroplating.

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