JPS62142389A - Copper foil for printed circuit and manufacture of the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] Wood powder is used for copper foil for printed circuits, more specifically, it is soluble in all types of etching solutions, especially soluble in alkaline etching solutions, and is effective in etching. The present invention relates to a copper foil for printed circuits that does not cause undercutting, has brown transfer resistance on the substrate surface after etching, and has excellent chemical resistance and heat resistance, and is suitable for high-density wiring.

[Conventional technology]

The mainstream method for producing printed circuit boards is the so-called subtractive method, in which copper foil is laminated on a synthetic resin-impregnated base material, heat-pressed at high temperatures, circuits are printed, and unnecessary portions are removed by etching.

With the development of semiconductors and electronic equipment, printed circuit boards have solidified their position as one of the electronic components and are rapidly becoming denser. The conductor width and ring spacing continue to become narrower, and the copper foil used also has improved adhesion to the substrate (O), etching resistance (versatility of being soluble in all etching solutions, and no undercutting). ), appearance after etching (brown transfer resistance), insulation properties,
Requirements for chemical resistance (acid resistance, alkali resistance, plating liquid resistance, solvent resistance), heat resistance, etc. during the manufacturing process or after the product is made are becoming increasingly strict.

Undercutting here refers to undercutting when a circuit is formed by etching, 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 steel, dendritic steel, 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 describes coating a copper foil surface with a layer selected from the group consisting of zinc, indium, brass, etc., and Patent Publication No. 53-39376 discloses a two-layer electrodeposited copper layer. and further coated with a layer of a metal that is not chemically active on the substrate to be bonded, such as zinc, brass, nickel, cobalt, chromium, cadmium, tin, and bronze; Patent Publication Showa 5
No. 8-500149 deposits spherical or dendritic zinc, and this layer is coated with copper, arsenic, bismuth, brass, bronze,
coating with one or more of nickel, cobalt or zinc or an alloy thereof;
No. 155593 proposes applying chromate cathode electrolytic treatment on a nickel plating layer.

However, there are problems with conventional single-layer coated barriers as shown below.

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 the printing During the circuit board manufacturing process, when the circuit board is pickled or immersed in various activation treatment solutions, the corrosion resistance at the interface is weak, resulting in a deterioration in beer strength, especially in the case of recent circuits with narrow conductor widths. Due to thermal shock or mechanical shock,
There is a drawback that the conductor may peel off or fall off. In addition, chlorinated corundum/7-ching and the like have the disadvantage of causing undercutting because the adhesive surface between mf/li and the base material is weak.

Nickel has excellent chemical and heat resistance, and is soluble in the ferric chloride and cupric chloride etching solutions commonly used for It has the serious disadvantage of being insoluble in liquids and producing etching residue (stain) that impairs electrical insulation.Also, by applying chromate cathode electrolytic treatment on the nickel plating layer, ammonium persulfate etching Although it is soluble in etching solutions, it is insoluble in alkaline etching solutions and causes staining.

The reasons for this are that 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, it is soluble in various etching solutions, especially alkaline etching solutions, does not cause harmful streaks, does not cause undercutting due to etching, and is easy to use after etching. The present invention was completed as a result of various research into a copper foil barrier layer that has Brownian transfer resistance on the substrate surface and also has excellent chemical resistance and heat resistance after circuit formation.

[Means for solving problems]

That is, the present invention has a nickel layer containing molybdenum on at least one surface of the copper foil, and if necessary, the nickel layer contains molybdenum.
A copper foil for printed circuits is characterized in that a chromate treatment layer is formed on the surface of the molybdenum layer, and an electrolytic bath containing nickel and molybdenum ions and one or more of citric acid or tartaric acid is used. This is a method for manufacturing a copper foil for printed circuits, characterized in that after cathodic electrolyzing the foil to form a nickel-molybdenum layer, a chromate treatment layer is provided on the layer.

[Effect]

The thickness of the molybdenum-containing nickel layer of the present invention is 0.001
= 0.5. crm (approximately 0.1 to 50 mg/dm”)
, preferably 0.005 to 0.2 μm (approximately 0.5 to 2
If it is less than 0.001 μm, the barrier effect of the present invention cannot be fully exhibited;
．． When the thickness is 5 μm or more, the purity of the copper foil decreases and the electrical conductivity decreases. Moreover, the cost ratio of the barrier increases, making it uneconomical.

The molybdenum content in the nickel-molybdenum layer of the present invention is 21 w% or more, more preferably 27-t% or more. If it is less than 21 wt%, it is not only insoluble in alkaline etching solutions but also in ammonium persulfate etching solutions and chloride. They are sparingly soluble or insoluble even in cupric etching solutions.They are all soluble in ferric chloride etching solutions.Moreover, the molybdenum content is 21 to 27-t.
%, if the nickel-molybdenum layer is non-uniform, it may become insoluble in alkali etching, so it is more preferably 27-t% 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, but the method is most suitable for industrial production lines. What seems to be the aqueous solution electroplating method. As the electrolytic bath, acidic citric acid bath,
An ammonia-alkali citric acid bath, an ammonia-alkali tartaric acid bath, etc. are preferred.

For example, regarding an ammonia-alkali 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 or 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 single barrier layer of the present invention requires a relatively high content of molybdenum,
It is better to make the amount of molybdenum ions in the electrolytic bath considerably larger than the amount of nickel ions. The amount of molybdenum ions is preferably approximately 60 to 70-t% or more based on the total amount of metal ions. The bath temperature is preferably around 30°C to prevent ammonia from scattering and to reduce costs.

The current density can be applied over a wide range of 1 to 20 A/dm2. Further, an insoluble anode, a nickel-molybdenum alloy, or nickel is used as the anode.

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 substrate and improves brown transfer resistance. , corrosion resistance can also be improved. The chromate treatment may be performed by immersion in a water/8 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, nickel sulfate (hexahydrate) 30g/(! Sodium molybdate (dihydrate) 70g/l citric acid Trisodium acid (dihydrate) 50g/βPH (adjusted with ammonia) 10.5 anode
7n of copper at 30°C in a platinum and toshiko bath.
Cathodic electrolysis was performed at a current density of 8 A/dm2 and an electrolysis time of 10 seconds. This copper foil was washed with water and then dried. This copper foil was laminated on an epoxy resin-impregnated glass substrate of FR-4 grade, molded, and various characteristic tests of the copper-clad laminate were conducted, and the results are shown in Table 2. The thickness of the nickel-molybdenum layer formed on this copper foil was 5.0 mH/dm'', and the molybdenum content was determined by atomic absorption spectrometry to be 38 wt%.

Example (2) A nickel-molybdenum layer was formed on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, under the same bath composition and electrolytic conditions as in Example (1), washed with water, and then dichromated. /N aqueous solution for 10 seconds, washed with water, and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2.

Example (3) A 35μ electrolytic copper foil whose surface had been electrolytically roughened in advance was prepared, and nickel sulfate (hexahydrate) 30 g/(mono-sodium molybdate (dihydrate) 100 g/β trisodium citrate (dihydrate) ) 50g/1lPH (
Adjusted with ammonia) 10.5 anode
Copper foil at 30° in this platinum bath
C, cathode electrolysis was performed at a current density of 10 A/dm2 and an electrolysis time of 10 seconds. This copper foil was washed with water and then dried. FR this copper foil
-Laminated on 4 grade epoxy resin impregnated glass substrate,
The molded copper-clad laminate was subjected to various characteristic tests, and the results are shown in Table 2. The thickness of the nickel-molybdenum layer formed on this 1iil fi was 5.4 mg/dm'', and the molybdenum content was determined by atomic absorption spectrometry to be 41 wt%.

Example (4) A nickel-molybdenum layer was formed on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, under the same bath composition and electrolytic conditions as in Example (3), washed with water, and then treated with sodium dichromate l.
og/1. After being immersed in an aqueous solution for 10 seconds, it was washed with water and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2.

Example (5) - 0ω On the surface of a 35μ electrolytic copper foil that had been electrolytically roughened in advance, trisodium citrate (dihydrate) was applied at 50 g/β, pH (adjusted with ammonia) was set at 10.5, and the bath temperature was set at 30°C. Nickel sulfate (hexahydrate), sodium molybdate (dihydrate)
, current density, and electrolysis time according to Examples (5) to Table 1.
After forming a nickel-molybdenum layer by making various changes as shown in column 00), it was washed with water, then immersed in an aqueous solution of sodium dichromate lOg/j2 for 10 seconds, washed with water, and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2.

Example (11) Prepare a 35μ electrolytic copper foil that has been electrolytically roughened in advance, and add 17 g of nickel sulfate (hexahydrate)/30 lonocell salt of sodium dimolybdate (dihydrate).
200g #! PI-1 (adjusted with ammonia) 10.5 anode
Platinum copper foil in this bath at 30°C1 current density 1
0A/dm" and cathodic electrolysis for 20 seconds. This copper foil was washed with water (and dried for 2 hours). This copper foil was laminated on an FR-4 grade epoxy resin-impregnated glass substrate, molded, and copper-clad. Various characteristic tests were conducted on the laminate, and the results are shown in Table 2.

The thickness of the nickel-molybdenum layer formed on this copper foil was 1.0 mg/dm'', and the molybdenum content was determined by atomic absorption spectrometry to be 58 wt%.

Example (12) A nickel-molybdenum layer was formed on the surface of a 35μ electrolytic copper foil, which had been electrolytically roughened in advance, under the same bath composition and electrolytic conditions as in Example (11), washed with water, and then treated with 10 g/l of sodium dichromate. Current density in aqueous solution 0.5A/dm", 5
After second cathodic electrolysis, it was washed with water and dried. This copper foil is FR-
The copper-clad laminates were laminated onto 4 grades of epoxy resin-impregnated glass substrates, molded, and subjected to various characteristic tests, and the results are shown in Table 2.
Shown below.

In addition, nickel sulfate, sodium molybdate (dihydrate), current density, electrolysis time,
N1-Mo The Mo content in N and the presence or absence of a chromate treatment layer are summarized in Table 1.

Comparative Example (1) Prepare a 35 μ electrolytic copper foil that has been electrolytically roughened in advance, and add nickel sulfate (hexahydrate) 30 g/j' trisodium citrate (2 water 50 g/IPH).
(adjusted with ammonia) 10.5 anode
Copper foil in platinum bath
℃, current density 8A/dm'', and electrolysis time 10 seconds. After washing this copper foil with water, sodium dichromate Log
/ jl! After being immersed in an aqueous solution for 10 seconds, it was washed with water and dried. This copper foil was laminated onto a FR-4 grade epoxy resin-impregnated glass base material, molded, and subjected to various characteristic tests of the copper-clad laminate. The results are shown in Table 2.

Comparative Example (2) Prepare a 35μ electrolytic copper foil that has been electrolytically roughened in advance, and add 200g of zinc sulfate! Ammonium sulfate 25g/IP H3.5 Anode Zinc Copper foil was heated in this bath at 30℃, current density 2A/dm''
Cathodic electrolysis was performed for 20 seconds. After washing this copper foil with water, it was immersed in a Log/l sodium dichromate aqueous solution for 10 seconds, washed with water, and dried. This copper foil was laminated onto an epoxy resin-impregnated glass base material of FR-4 wire, and the copper clad laminate was molded and subjected to various characteristic tests, and the results are shown in Table 2.

Comparative Example (3) A 35μ electrolytic copper foil that had been electrolytically roughened in advance was coated with sodium dichromate Log/! l After immersion in the aqueous solution for 10 seconds,
Washed with water and dried. This copper foil was applied to an FR-4 grade epoxy resin-impregnated glass substrate and molded, and various characteristic tests of the copper-clad laminate were conducted, and the results are shown in Table 2.

Table 1 Note) ml The adhesion test was conducted with a peel width of 11 (formed by ferric chloride etching), and other conditions were JIS-C-64.
81-1976, paragraphs 5 and 7.

*2 Adhesion strength after 11CI immersion is 20% in 20% hydrochloric acid aqueous solution.
Adhesion strength after immersion at ℃ for 20 minutes.

Book 3 Etching Stain Etching Liquid Method ○ No stain observed at all B: Stain is slightly observed Visually observe the appearance.

○: Good: Poor ×: Defective Book 5 A conductor with a width of Jmm was formed by undercut cupric chloride etching, and the peeled copper foil surface was observed using a stereoscopic microscope.

○: No X, practically impossible [Effects of the invention] As described above, the characteristics of the copper foil for printed circuits obtained by the present invention are extremely excellent.

Namely, ferric chloride, cupric chloride, ammonium persulfate,
The nickel-molybdenum layer of the present invention is soluble in alkaline etching and all types of etching solutions, making it versatile.Also, since the nickel-molybdenum layer of the present invention dissolves in etching solutions at almost the same rate as copper, undercutting does not occur and brown transfer resistance after etching is achieved. As for the quality, there is almost no discoloration and no stains. Furthermore, the adhesive strength hardly deteriorates after immersion in hydrochloric acid, and no liquid seepage is observed at all. Furthermore, it maintains an extremely excellent property of hardly deteriorating even after heat treatment at a high temperature of 180° C. for 48 hours for a long period of time, and there is no fear that the circuit will peel 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, the copper foil for printed circuits of the present invention, which has no restrictions on etching solutions, no undercutting due to etching, good brown transfer resistance, and excellent chemical and heat resistance, can be used not only for general printed circuit boards but also for high-density , suitable for ultra-high density multi-layer printed circuit boards.

Claims (3)

[Claims] (1) A copper foil for printed circuits, characterized by having 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 of citric acid or tartaric acid, cathodically electrolyze the copper foil in the electrolytic bath to form a nickel-molybdenum layer, and then chromate treatment on the layer. A method for producing copper foil for printed circuits, characterized by providing a layer.