JPH0426794B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to copper foil for printed circuits, more specifically, it is soluble in all etching solutions, especially soluble in alkaline etching solutions, does not cause undercutting during etching, and can be etched easily. The present invention relates to a printed circuit molten copper foil suitable for high-density wiring, which has resistance to Brownian transfer on the rear substrate surface, as well as excellent chemical resistance and heat resistance. [Prior Art] Printed circuit boards are mainly manufactured by the so-called subtractive method, in which copper foil is laminated on a synthetic resin-impregnated base material, heat-pressed at high temperature, circuits are printed, and unnecessary portions are removed by etching. With the reversal of semiconductors and electronic devices, printed circuit boards have solidified their position as one of the electronic components, and are rapidly becoming more densely packed. Conductor width and conductor spacing continue to become narrower, and the copper foil used has not only adhesion to the base material but also etching properties (versatile, soluble in all etching solutions, and no undercutting). ), appearance after etching (brown transfer resistance), insulation, chemical resistance during the manufacturing process or after becoming a product (acid resistance, alkali resistance, plating liquid resistance, solvent resistance),
Requirements such as heat resistance are becoming increasingly strict. Undercutting here refers to undercutting when a circuit is etched, especially near the bonding surface between the board and copper foil, and brown transfer refers to the etching that occurs in printed circuits using glass epoxy base materials. Refers to discoloration, discoloration, and dirt on the board. Copper foil for printed circuits is typically manufactured as follows. First, as basic copper foils, there are electrolytic copper foils obtained by cathodic electrolysis in an electrolytic bath containing copper ions, and rolled copper foils. In order to improve the properties, granular copper, dendritic copper, etc. are provided by electrolysis. Next, in order to obtain a non-reactive property with the adhesive resin, a barrier coating of a different metal or an alloy with copper is applied to the surface, or various anti-corrosion treatments are applied. For example, Patent Publication No. 51-35711 discloses that a copper foil surface is coated with a layer selected from the group consisting of zinc, indium, brass, etc., and Patent Publication No. 53-39376 discloses that a copper foil layer is coated with a layer selected from the group consisting of zinc, indium, brass, etc. and a layer made of a metal that has no chemical activity with respect to the substrate to be bonded, such as zinc, brass, nickel, cobalt, etc.
Coating with a layer of chromium, cadmium, tin, bronze, etc., or depositing spherical or dendritic zinc and coating this layer with copper, arsenic, bismuth, brass, bronze, etc. , coating with one or more of nickel, cobalt or zinc or an alloy thereof;
No. 155593 proposes applying chromate cathode electrolytic treatment to the nickel plating layer. However, conventional coated barrier layers have the following problems. When a copper foil with a layer mainly made of zinc, such as zinc, brass, or zinc-nickel, is applied to a printed circuit board,
The adhesive surface between the copper foil and the base material and its vicinity have very low hydrochloric acid resistance, and in the printed circuit board manufacturing process,
While being immersed in pickling or various activation treatment solutions, the peel strength deteriorates due to the weak corrosion resistance at the interface, and especially in the case of recent circuits with narrow conductor widths, thermal shock or mechanical The drawback is that there is a possibility that the conductor may peel off or fall off due to impact or the like. In addition, cupric chloride etching and the like still have the disadvantage of causing undercutting because the adhesive surface between the copper foil and the base material is weak. Nickel has excellent chemical and heat resistance, and although it is soluble in commonly used ferric chloride and cupric chloride etching solutions, it is soluble in alkaline etching solutions that have recently become popular. It has the serious drawback that it is insoluble and produces etching residue (stain) that impairs electrical insulation. Further, by subjecting the nickel plating layer to a chromate cathode electrolytic treatment, the layer becomes soluble in ammonium persulfate etching solution, but is insoluble in alkaline etching solution and produces stain. In addition, tin, chromium, and bismuth are also insoluble in alkaline etching solutions, cobalt is soluble in alkaline etching solutions but has problems with chemical resistance, indium is expensive, brass,
Cyanide baths are used in bronze plating, but they each have their own drawbacks, such as the problem of pollution, and arsenic and cadmium are also avoided due to their toxicity. Merely focusing on performance cannot fully satisfy the rapidly increasing density and diverse demands of printed circuit boards. [Problems to be solved by the present invention] Therefore, in order to solve all the problems of the conventional technology as a copper foil for printed circuits, various etching solutions,
In particular, it is soluble in alkaline etching solutions, does not produce harmful stains, does not cause undercutting due to etching, has brown transfer resistance on the substrate surface after etching, and has excellent chemical resistance and heat resistance after circuit formation. The present invention was completed as a result of various studies on copper foil barrier layers. [Means for solving the problem] That is, the present invention has a nickel layer containing molybdenum on at least one side of a copper foil, and optionally a chromate treatment layer on the surface of the nickel-molybdenum layer. Using an electrolytic bath containing nickel and molybdenum ions and one or more of citric acid or tartaric acid, the copper foil is cathodically electrolyzed in the electrolytic bath to form a nickel-coated circuit.
This is a method for producing copper foil for printed circuits, which comprises forming a molybdenum layer and then providing a chromate treatment layer on the layer. [Function] The thickness of the molybdenum-containing nickel layer of the present invention is
0.001 to 0.5 μm (approximately 0.1 to 50 mg/dm ² ), preferably
Approximately 0.005 to 0.2 μm (approximately 0.5 to 20 mg/dm ² ) is preferable.
If the thickness is 0.001 μm or less, the barrier effect of the present invention cannot be sufficiently exhibited, while if the thickness is 0.5 μm or more, the purity of the copper foil decreases and the electrical conductivity decreases. Moreover, the cost ratio of the barrier layer increases, making it uneconomical. The molybdenum content in the nickel-molybdenum layer of the present invention is 21 wt% or more, more preferably 27 wt%
That's all. If it is less than 21 wt%, it is not only insoluble in alkaline etching solutions, but also sparingly soluble or insoluble in ammonium persulfate etching solutions and cupric chloride etching solutions. All were soluble in the ferric chloride etching solution.
Further, when the molybdenum content is 21 to 27 wt%, the nickel-molybdenum layer may become insoluble in alkali etching when there is non-uniformity, so it is more preferably 27 wt% or more. The nickel-molybdenum layer of the present invention can be formed on the surface of copper foil by various known methods such as electroplating, chemical plating, vacuum evaporation, and sputtering. The most suitable method for this purpose is aqueous electroplating. As the electrolytic bath, an acidic citric acid bath, an ammonia-alkali citric acid bath, an ammonia-alkali tartaric acid bath, etc. are preferable. For example, regarding an ammonia alkaline citric acid bath, nickel sulfate is preferred as the nickel ion source, sodium, potassium, or ammonium salts of molybdate are preferred as the molybdenum ion source, and citric acid and sodium, potassium, or ammonium salts of citric acid are preferred as the citric acid. Ammonia is added to these to make them alkaline. Molybdenum is an induced precipitation type for iron group metals, and does not precipitate in the absence of nickel ions. Since the barrier layer of the present invention requires a relatively high content of molybdenum, it is preferable that the amount of molybdenum ions in the electrolytic bath be considerably greater than the amount of nickel ions.
The amount of molybdenum ions is preferably about 60 to 70 wt% or more based on the total amount of metal ions. The bath temperature is preferably around 30℃ to prevent ammonia from scattering and to reduce costs. The current density can be applied over a wide range of 1 to 20 A/dm ² . In addition, the anode is an insoluble anode, nickel-
Use molybdenum alloy or nickel. After electrodepositing a nickel-molybdenum layer on a roughened copper foil under the above conditions, applying the commonly used chromate treatment increases adhesion to the base material and improves brown transfer resistance. Moreover, corrosion resistance is also improved. The chromate treatment may be performed by immersion in an aqueous solution containing a hexavalent chromium compound such as chromic acid or dichromate, or by cathodic electrolysis. [Example] Examples of the present invention will be shown below. Example 1 A 35μ electrolytic copper foil that had been electrolytically roughened in advance was prepared, and as shown in Table 1, 30 g of nickel sulfate (hexahydrate) / 70 g of sodium molybdate (dihydrate) / trisodium citrate (2 water salt) 50g / PH (adjusted with ammonia) 10.5 Anode Copper foil was heated at 30℃ in a platinum bath at a current density of 8A /
Cathode electrolysis was carried out at dm ² and electrolysis time for 10 seconds. This copper foil was washed with water and then dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass substrate, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2. Also, the nickel formed on this copper foil
The thickness of the molybdenum layer was 5.0 mg/dm ² , and the molybdenum content was determined by atomic absorption spectrometry to be 38 wt%. Example 2 Nickel was deposited on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, using the same bath composition and electrolytic conditions as in Example 1.
After forming a molybdenum layer, washing with water, and immersing it in a 10 g/aqueous solution of sodium dichromate for 10 seconds,
Washed with water and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass substrate, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2. Example 3 Prepare a 35μ electrolytic copper foil that has been electrolytically roughened in advance, and add 30 g of nickel sulfate (hexahydrate) / 100 g of sodium molybdate (dihydrate) / 50 g of trisodium citrate (dihydrate) / PH (ammonia) 10.5 Anode Platinum In this bath, the copper foil was heated at 30℃ and the current density was 10A/d.
m ² and cathodic electrolysis for 10 seconds. This copper foil was washed with water and then dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and various characteristic tests were conducted on the copper-clad laminate. The results are shown in Table 2.
Shown below. The thickness of the nickel-molybdenum layer formed on this copper foil was 5.4 mg/dm ² , and the molybdenum content was determined by atomic absorption spectrometry to be 41 wt%. Example 4 Nickel was deposited on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, using the same bath composition and electrolytic conditions as in Example 3.
After forming a molybdenum layer, washing with water, and immersing it in a 10 g/aqueous solution of sodium dichromate for 10 seconds,
Washed with water and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass substrate, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2. Examples 5 to 10 Trisodium citrate (dihydrate) 50g/PH on the surface of 35μ electrolytic copper foil which has been electrolytically roughened
(Adjusted with ammonia) 10.5, the bath temperature was 30°C, and the combinations of nickel sulfate (hexahydrate), sodium molybdate (dihydrate), current density, and electrolysis time are shown in the columns of Examples 5 to 10 in Table 1. After forming a nickel-molybdenum layer in various ways, it was washed with water, and then 10 g of sodium dichromate was added to the aqueous solution.
After being immersed for a second, it was washed with water and dried. FR this copper foil
- Laminated on 4 grade epoxy resin impregnated glass substrate, molded and tested various properties of copper clad laminates,
The results are shown in Table 2. Example 11 Prepare a 35 μ electrolytic copper foil that has been electrolytically roughened in advance, and add 17 g of nickel sulfate (hexahydrate) / 30 g of sodium molybdate (dihydrate) / 200 g of Rothsell's salt / PH (adjusted with ammonia) 10.5 anode platinum Copper foil in a bath at 30℃, current density 10A/d
m ² and cathodic electrolysis for 20 seconds. This copper foil was washed with water and then dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass substrate, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2. The thickness of the nickel-molybdenum layer formed on this copper foil was 1.0 mg/dm ² , and the molybdenum content was determined by atomic absorption spectrometry to be 58 wt%. Example 12 Nickel was deposited on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, using the same bath composition and electrolytic conditions as in Example 11.
Form a molybdenum layer, wash with water, and then apply current density in 10 g of sodium dichromate/aqueous solution.
After cathodic electrolysis at 0.5 A/dm ² for 5 seconds, it was washed with water and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass substrate, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2. In addition, nickel sulfate, sodium molybdate (dihydrate), current density, electrolysis time,
Table 1 summarizes the Mo content in the Ni-Mo layer and the presence or absence of a chromate treatment layer. Comparative Example 1 Prepare a 35μ electrolytic copper foil that has been electrolytically roughened in advance, and add nickel sulfate (hexahydrate) 30g/sodium citrate (dihydrate) 50g/PH (adjusted with ammonia) 10.5 anode platinum in this bath. at 30℃, current density 8A/ ^dm2 ,
Cathodic electrolysis was performed for an electrolysis time of 10 seconds. After washing this copper foil with water, add 10 g of sodium dichromate/10 g of sodium dichromate to an aqueous solution.
After dipping for a second, it was washed with water and dried. FR this copper foil
- Laminated on 4 grade epoxy resin impregnated glass substrate, molded and tested various properties of copper clad laminates,
The results are shown in Table 2. Comparative Example 2 A 35μ electrolytic copper foil that had been electrolytically roughened in advance was prepared, and the copper foil was heated in this bath at 30℃ and a current density of 2A/d.
m ² and cathodic electrolysis for 20 seconds. After washing this copper foil with water, put it in 10g of sodium dichromate/aqueous solution.
After immersing for 10 seconds, it was washed with water and dried. This copper foil
The copper-clad laminate was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and subjected to various characteristic tests, and the results are shown in Table 2. Comparative Example 3 A 35μ electrolytic copper foil whose surface had been electrolytically roughened in advance was immersed in a 10 g/aqueous solution of sodium dichromate for 10 seconds, washed with water, and dried. This copper foil was laminated onto an FR-4 grade epoxy resin-impregnated glass substrate, molded, and various characteristic tests of the copper-clad laminate were conducted, and the results are shown in Table 2.

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〔Effect of the invention〕

As described above, the properties of the copper foil for printed circuits obtained by the present invention are extremely excellent. That is, it is soluble and versatile in all kinds of etching solutions, including ferric chloride, cupric chloride, ammonium persulfate, and alkaline etching, and the nickel-molybdenum layer of the present invention dissolves in etching solutions at approximately the same rate as copper. Therefore, undercutting does not occur, and there is almost no discoloration in terms of brown transfer resistance after etching.
No stains occur. Furthermore, the adhesive strength hardly deteriorates after immersion in hydrochloric acid, and no liquid seepage is observed at all. In addition, it maintains an extremely excellent property of hardly deteriorating even after being heated for a long time at a high temperature of 180℃ for 48 hours, so there is no need to worry about the circuit peeling off due to the effects of chemicals or heat. Therefore, it is thought that its performance will be demonstrated in printed circuits that are becoming significantly smaller, particularly in high-density circuits. As mentioned above, there are no restrictions on the etching solution, no undercutting due to etching, good brown transfer resistance, and chemical resistance.
The copper foil for printed circuits of the present invention, which has excellent heat resistance, is suitable for not only general printed circuit boards but also high-density and ultra-high-density multilayer printed circuit boards.

Claims (1)

[Scope of Claims] 1. A copper foil for printed circuits, comprising a nickel layer containing molybdenum on at least one surface of the copper foil. 2. The copper foil for printed circuits according to claim 1, characterized in that a chromate treatment layer is formed on the surface of the nickel-molybdenum layer. 3 Using an electrolytic bath containing nickel and molybdenum ions and one or more types of citric acid or tartaric acid,
A method for manufacturing a copper foil for printed circuits, which comprises cathodically electrolyzing the copper foil in the electrolytic bath to form a nickel-molybdenum layer, and then providing a chromate treatment layer on the layer.