Composite metal foil and production method for said composite metal foil

Abstract

[Problem] To provide a composite metal foil having a second copper layer laminated on a dissimilar metal layer, wherein a circuit can be formed by selective etching, and since it is easy to clearly distinguish the contrast between the dissimilar metal layer and the second copper layer, erroneous or missed detection of a circuit pattern during image inspection, as well as positional deviation in multilayering are unlikely to occur, as a result of which the composite metal foil can be suitably used for a printed wiring board. [Solution] A composite metal foil including at least one layer structure comprising a first copper layer, a dissimilar metal layer, and a second copper layer, wherein the value obtained by subtracting the lightness L*Cu value of the surface of the second copper layer from the lightness L*A value of the surface of the dissimilar metal layer on which the second copper layer is laminated is 15 or more.

Description

Composite metal foil and method for producing the same

[0001] The present invention relates to a composite metal foil, specifically to a composite metal foil having a second copper layer laminated on a dissimilar metal layer, which allows a circuit to be formed by selectively etching the second copper layer, and the contrast between the dissimilar metal layer and the second copper layer is clear and easy to distinguish, making it less likely to cause erroneous detection or oversight of circuit patterns in image inspections or to cause misalignment when layers are stacked, making it suitable for use in printed wiring boards.

[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 in which composite metal foils made of different metals are used to selectively etch each metal (hereinafter referred to as "selective etching"), and manufacturing methods using selective etching solutions that can selectively etch each metal.

[0004] In the manufacturing process of printed wiring boards, it is necessary to accurately identify the circuit pattern, such as by image inspection (AOI inspection) of the circuit pattern and the positions of through holes and vias 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, in which the contrast between the dissimilar metal layer and the second copper layer is clear, and in which the circuit pattern can be accurately identified by image inspection, thereby reducing the risk of false detection, missed detection, and misalignment when layering.

[0007] JP 2002-359471 JP 2014-063950 WO 2012-132573 JP 7-221449

[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 may cause 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 dissimilar metal selected from nickel, iron, cobalt, tin, indium, and bismuth laminated on at least one surface of the first copper layer, and a second copper layer laminated on the dissimilar metal layer, wherein the lightness L of the surface of the second copper layer as defined in JIS-Z8781-4 is 0.015 or less. ＊ Value: Lightness L ＊ Ｃｕ the lightness L of the surface of the different metal layer on which the second copper layer is laminated; ＊ Value: Lightness L ＊ Ａ The lightness L when the value ＊ Ａ Value - Lightness L ＊ Ｃｕ The above technical objective was achieved by finding that a composite metal foil having a value of 15 or more allows a circuit to be formed by selective etching, and the contrast between the different metal layer and the second copper 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.

[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 dissimilar metal selected from Group A below laminated on at least one surface of the first copper layer, and a second copper layer laminated on the dissimilar metal layer, wherein the lightness L of the surface of the second copper layer as defined in JIS-Z8781-4 is: ＊ Value: Lightness L ＊ Ｃｕ the lightness L of the surface of the different metal layer on which the second copper layer is laminated; ＊ Value: Lightness L ＊ Ａ The lightness L when the value ＊ Ａ Value - Lightness L ＊ Ｃｕ A composite metal foil having a value of 15 or more. Group A: Nickel, iron, cobalt, tin, indium, bismuth

[0014] The present invention also relates to the composite metal foil, wherein the dissimilar metal of Group A is nickel.

[0015] Furthermore, the present invention provides a method for manufacturing a thermoplastic resin having the above-mentioned lightness L ＊ Ｃｕ The composite metal foil has a value of 65 or less.

[0016] The present invention also relates to the composite metal foil, wherein the ten-point average roughness Rzjis of the surface of the different metal layer is 5 μm or less.

[0017] The present invention also provides a nickel layer having 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 The composite metal foil is as follows:

[0018] 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 dissimilar metal layer is not laminated is surface-treated.

[0019] The present invention also relates to the composite metal foil described above, which is for use in a printed wiring board.

[0020] The present invention also provides a method for producing the composite metal foil, comprising the steps of: forming the first copper layer; laminating the dissimilar metal 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 dissimilar metal layer.

[0021] The present invention also provides the method for producing a composite metal foil, wherein the laminating step is electroplating.

[0022] The composite metal foil of the present invention is a composite metal foil having at least one layer structure of a first copper layer / a dissimilar metal layer / a second copper layer, and a circuit can be formed by selectively etching the second copper layer.

[0023] In addition, the lightness L of the different metal layer ＊ Ａ Value - Lightness L of the second copper layer ＊ Ｃｕ Since the value is 15 or more, the contrast between the dissimilar metal layer and the second copper layer is clear and easy to distinguish, so that 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.

[0024] Also, the brightness L ＊ Ｃｕ If the value is 65 or less, the second copper layer appears sufficiently black, so that the contrast with the dissimilar metal layer becomes clearer.

[0025] Furthermore, if the ten-point average roughness Rzjis of the surface of the different metal layer is 5 μm or less, the composite metal foil can be used to form a circuit with excellent circuit shape precision.

[0026] In addition, when nickel is selected as the dissimilar metal, the purity of nickel is 99.6 wt % or more, and the square meter weight is 2.7 g / m ２ or more, and 27 g / m ２ If the thickness is less than this, the composite metal foil will have excellent selectivity and removability by selective etching.

[0027] 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.

[0028] 1 is a schematic diagram of one embodiment of a composite metal foil according to the present invention, 2 is a schematic diagram of one embodiment of a composite metal foil according to the present invention, 3 is a schematic diagram of one embodiment of a composite metal foil according to the present invention, 4 is a schematic diagram of one embodiment of a composite metal foil according to the present invention.

[0029] 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 dissimilar metal layer (30) / a second copper layer (40).

[0030] (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.

[0031] 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.

[0032] 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.

[0033] If the thickness is less than 9 μm, wrinkles and cracks may occur when the dissimilar metal layers are laminated, and if it exceeds 300 μm, the overall rigidity of the composite metal foil may become too strong, making it difficult to handle.

[0034] (Dissimilar Metal Layer) In the composite metal foil of the present invention, a dissimilar metal layer (30) is laminated on a first copper layer (20).

[0035] The surface on which the different metal layer is laminated may be either one surface or both surfaces of the first copper layer, and may be appropriately selected as required.

[0036] The surface of the first copper layer on which no different metal layer is laminated may be subjected to a surface treatment.

[0037] 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.

[0038] The ten-point average roughness Rzjis of the surface of the dissimilar metal layer on which the second copper layer is laminated, measured in accordance with JIS-B0601 (2013), is preferably 5 μm or less, and more preferably 3 μm or less.

[0039] If the ten-point average roughness Rzjis of the surface of the dissimilar metal layer exceeds 5 μm, the unevenness becomes too large, which may result in poor adhesion between the dissimilar metal layer and the second copper layer or a deterioration in the precision of the circuit shape.

[0040] The different metal layer in the present invention is made of a metal that can be selectively etched relative to copper, such as nickel, iron, cobalt, tin, indium, or bismuth.

[0041] The following description will be given taking a nickel layer and an iron layer as examples of dissimilar metal layers.

[0042] The nickel purity of the nickel layer is preferably 99.6% by weight or more.

[0043] If the purity of nickel is low, the selectivity and removability of the selective etching may decrease.

[0044] The square meter weight of the nickel layer in the present invention is 2.7 g / m ２ ~27g / m ２ is preferable, and more preferably 4.5 g / m ２ ~18g / m ２ is.

[0045] 2.7 g / m ２ If the thickness 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.

[0046] The method for forming the nickel layer is not particularly limited, but it is preferably formed by an electrolytic method.

[0047] This is because the electrolytic method can achieve a nickel purity of 99.6% by weight or higher.

[0048] The plating bath used in forming the nickel layer 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 4.2, bath temperature 50°C to 60°C, current density 0.5 A / dm ２ ~8 A / dm ２) or sulfamic acid bath (nickel sulfamate 440g / L to 500g / L, boric acid 30mL / L to 50mL / L, pH 3.8 to pH 4.4, bath temperature 50°C to 60°C, current density 2A / dm ２ ~40 A / dm ２ The first copper layer can be immersed in the electrolytic plating solution to form a nickel layer on the first copper layer.

[0049] 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.

[0050] The iron layer was prepared using a sulfuric acid bath (iron (II) sulfate heptahydrate 200 g / L to 300 g / L, pH 2.8 to pH 3.5, bath temperature 30°C to 65°C, current density 4A / dm). ２ ~10 A / dm ２ ) and electroplating, a dissimilar metal layer made of iron can be formed on the first copper layer.

[0051] For other metals, a different metal layer may be formed by a known method such as electrolytic plating, electroless plating, physical film formation, or chemical film formation.

[0052] (Second Copper Layer) In the composite metal foil of the present invention, a second copper layer is laminated on the dissimilar metal layer.

[0053] The thickness of the second copper layer is not particularly limited, but is preferably 1 μm to 70 μm.

[0054] Lightness L of the second copper layer surface ＊ Ｃｕ The value is preferably 65 or less, because the contrast between the different metal layer and the second copper layer becomes clear and they are easy to distinguish.

[0055] The surface of the second copper layer opposite to the dissimilar metal layer may be subjected to a surface treatment.

[0056] 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.

[0057] 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 ~60 A / dm ２ ) and electroplating can be performed to form a second copper layer on the different metal layer.

[0058] Additives may be added to the plating bath used when forming the second copper layer by electroplating.

[0059] An example of an additive is gelatin.

[0060] The lightness L of the surface of the second copper layer that is not in contact with the dissimilar metal layer ＊ Ｃｕ In order to reduce the value to 65 or less, blackening treatment for forming needle-like crystals of copper oxide on the surface of the second copper layer or known techniques such as those disclosed in JP-A-2011-179078 may be applied.

[0061] 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 surface of the dissimilar metal layer on which the second copper layer is laminated is lightness L ＊ Ａ When the value is ＊ Ａ Value - Lightness L ＊ Ｃｕ The value is preferably 15 or more, more preferably 20 or more.

[0062] Lightness L ＊ If the difference in values ​​is less than 15, the contrast between the dissimilar metal layer and the second copper layer will not be clear, which may make it difficult to accurately identify the circuit pattern by image inspection or may cause the pattern to be misaligned when multi-layered.

[0063] Examples and comparative examples of the present invention are shown below, but the present invention is not limited to these.

[0064] Examples 1 to 6 As the first copper layer, an electrolytic copper foil having a thickness of 70 μm was used.

[0065] 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 for 120 seconds to form a nickel layer.

[0066] 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 layer.

[0067] The surface on which the second copper layer was formed was treated under the conditions shown in Table 1 to perform a surface treatment for reducing the brightness of the second copper layer.

[0068] Example 7 The same procedure as in Example 1 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.

[0069] Example 8 The same procedure as in Example 1 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.

[0070] (Example 9) The dissimilar metal layer was formed by iron plating in a sulfuric acid bath (iron (II) sulfate heptahydrate 250 g / L, pH 3.2, bath temperature 45°C, current density 7 A / dm ２ The fabrication was carried out in the same manner as in Example 1, except that the treatment time was 120 seconds.

[0071] Comparative Example 1 A comparative example was produced in the same manner as in Example 1, except that the second copper layer was not subjected to a surface treatment.

[0072] Comparative Example 2 A substrate was produced in the same manner as in Comparative Example 1, except that the treated surface was the deposition surface.

[0073] (Surface Roughness) The ten-point average roughness Rzjis of the surface of the dissimilar metal layer before the formation of the second copper layer was measured in accordance with JIS-B0601 (2013) using a surface roughness measuring instrument SE-600 (manufactured by Kosaka Laboratory Co., Ltd.).

[0074] (Lightness L＊ The lightness L value as specified in JIS-Z8781-4 was measured for the dissimilar metal layer and the second copper layer before the formation of the second copper layer using a spectrophotometer CM-600d (manufactured by Konica Minolta, Inc.). ＊ Ａ Value, Lightness L ＊ Ｃｕ After measuring the value, the lightness L ＊ Ａ Value - Lightness L ＊ Ｃｕ The values ​​of the values ​​were calculated.

[0075] (Binarization Possibility) A portion of the second copper layer was removed with a selective copper etching solution to expose the heterogeneous metal layer, and an image of the boundary between the exposed heterogeneous metal layer and the second copper layer was photographed and binarized using the Threshold function of the image processing software ImageJ. The results were evaluated as ◯ if they could be binarized, and x if they could not.

[0076] The conditions for the surface treatment to reduce the brightness of the second copper layer surface are shown in Table 1. The evaluation results of the examples and comparative examples are shown in Table 2.

[0077]

[0078]

[0079] The examples and comparative examples have proven that the composite metal foil of the present invention provides a clear contrast between the dissimilar metal layer and the second copper layer, and can be binarized, making it easy to identify the circuit pattern.

[0080] In Comparative Examples 1 and 2, binarization was impossible because the contrast was not clear.

[0081] Furthermore, even if the interface between the different metal layer and the second copper layer was made extremely rough, the contrast did not become clear.

[0082] In the composite metal foil of the present invention, since the second copper layer is laminated on the dissimilar metal layer, a circuit can be formed by selective etching. ＊The difference in value is 15 or more, and the contrast between the dissimilar metal layer and the second copper layer is clear and easy to distinguish, so that the composite metal foil is less likely to be erroneously detected or missed in an image inspection, and is less likely to be misaligned when multi-layered, making it suitable for use in printed wiring boards.

[0083] 10 Composite metal foil 20 First copper layer 30 Dissimilar metal layer 40 Second copper layer

Claims

1. A composite metal foil comprising a first copper layer and a second copper layer laminated on at least one surface of a laminated metal foil having a dissimilar metal selected from Group A below laminated on at least one surface of the first copper layer, the second copper layer having a lightness L as defined in JIS-Z8781-4 on the surface of the second copper layer. ＊ Value is lightness L ＊ Ｃｕ the lightness L of the surface of the different metal layer on which the second copper layer is laminated; ＊ Value is lightness L ＊ Ａ The lightness L when the value ＊ Ａ Value - Lightness L ＊ Ｃｕ Composite metal foil with a value of 15 or more. Group A: Nickel, iron, cobalt, tin, indium, bismuth 2. The composite metal foil according to claim 1, wherein said dissimilar metal of group A is nickel.

3. The brightness L ＊ Ｃｕ 3. The composite metal foil according to claim 1, wherein the value is 65 or less.

4. A composite metal foil according to claim 1 or 2, wherein the ten-point average roughness Rzjis of the surface of said different metal layer is 5 μm or less.

5. 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 2, wherein:

6. The composite metal foil according to claim 1 or 2, wherein at least a portion of the surface of said first copper layer or said second copper layer on which said dissimilar metal layer is not laminated is surface-treated.

7. The composite metal foil according to claim 1 or 2, which is for use in printed wiring boards.

8. A method for producing a composite metal foil according to claim 1 or 2, comprising the steps of: forming the first copper layer; laminating the dissimilar metal 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 dissimilar metal layer.

9. The method for producing a composite metal foil according to claim 8, wherein said laminating step is electroplating.

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