JPH07180090A - Production of metallic foil for printed circuit board - Google Patents

Abstract

PURPOSE:To produce the metallic foil for a printed circuit board which is never curled by electroplating the roughened surface of the copper foil for a carrier with an Ni-P layer in specified thickness and further forming a copper layer to form a circuit on the surface. CONSTITUTION:The roughness for strengthening the adhesion with resin is formed on at least one surface to prepare a copper foil for the carrier. An Ni-P layer having 0.04-1.5mum thickness is formed on the roughened surface of the copper foil by electroplating. A plating soln. contg. the main agent consisting of nickel sulfate, phosphorous acid and boric acid and an additive selected from among o-sulfobenzimide, naphthalenesulfonic acids or their alkali metal salts is used. The content of the additive is preferably controlled to 2-10g/l and the pH of the plating soln. to 1.6-2.8. The plating soln. is kept at about 40-60 deg.C, and the current density is preferably adjusted to about 3-7A/dm<2>. The copper layer for a circuit is further formed on the copper foil surface. Consequently, the Ni-P layer as the intermediate layer relieves stress, and the foil is not curled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal foil used for printed wiring boards.

[0002]

2. Description of the Related Art With the development of electronic equipment, printed wiring boards are required to have high performance. For example, the wiring density is 0.15 when a so-called surface mount component that connects to an electronic component on the surface of a wiring board is developed and the distance between the connection terminals of the electronic component becomes small.
Those having a size of less than mm are beginning to be used, and it is required to form a circuit conductor according to this density.

As a method of manufacturing such a wiring board having a high wiring density, a copper-clad laminate obtained by bonding a copper foil to an insulating base material is used as a starting material, and a portion of the copper foil which does not serve as a circuit conductor is removed by etching. Circuit to form a circuit, an additive method to form a circuit by electroless plating to the required circuit shape on the surface of the insulating base material, a part of the circuit conductor such as the inner wall of the through hole is formed by electroless plating The semi-additive method and the like are generally known.

Among them, the subtractive method has been used for a long time, and in order to improve the wiring density, the copper foil of the copper-clad laminate is usually thinned. The reason for this is that when an etching resist is formed on the surface of the copper foil in the required circuit shape and the unnecessary copper foil exposed from the etching resist is removed with an etching solution, copper is etched from the side surface of the necessary circuit part. This is because a phenomenon called so-called side etching occurs, and as the copper foil is thicker, the amount removed from the circuit conductor by the side etching increases, and it becomes difficult to form a fine circuit.

Therefore, a thin copper foil for the copper clad laminate as a starting material is required, and such a thin copper foil is a rolled copper foil obtained by extending copper by heat and pressure or a metal such as stainless steel. An electrolytic copper foil having copper deposited on its surface by electrolytic plating is used, and a copper foil having a thickness of 18 to 70 μm is usually manufactured. Further, in recent years, an electrolytic copper foil in which a thin copper foil of about 5 μm is formed on an aluminum foil by electrolytic plating is also known.

Since such a thin copper foil is a copper-clad laminate which is a substrate for printed wiring boards, it is difficult to handle when laminating the copper foil and the uncured or semi-cured prepreg. , The copper foil is broken with a little force. In addition, such a problem often occurs due to the handling when manufacturing the copper foil. Therefore, a method has been proposed in which a thin copper foil is bonded to a plate or foil serving as a support having a strength that is easy to handle, and the support is removed after being bonded to an insulating base material or before being used. ing. As an example of this, Japanese Patent Laid-Open No. 58-108785 discloses a metal foil having a three-layer structure in which a carrier copper layer and nickel or the like having different etching removal conditions from copper are used as an intermediate layer and having a thin circuit copper layer. Japanese Patent Application Laid-Open No. 5-20659
No. 9 discloses that a nickel-phosphorus intermediate layer is formed using a plating solution containing nickel sulfate, phosphorous acid, and boric acid to improve the selective etching property of the intermediate layer.

[0007]

However, the plating solution containing nickel sulfate, phosphorous acid, and boric acid used for using this nickel-phosphorus as an intermediate layer has an electrodeposition stress of the deposited nickel-phosphorus alloy. The cost is high, and the end of the metal foil is curled, which causes a problem of difficulty in handling.

It is an object of the present invention to provide a nickel-phosphorus plating solution which is excellent in curling curls generated at the ends of a metal foil, and a method for producing a metal foil for printed wiring boards using this plating solution. And

[0009]

The nickel-phosphorus electroplating solution of the present invention comprises a main agent consisting of nickel sulfate, phosphorous acid and boric acid, and O-sulfobenzoic acid imide, naphthalene sulfonic acids, or alkali metals thereof. And an additive selected from salts. Representative examples of the naphthalene sulfonic acids used in the present invention include naphthalene sulfonic acid, naphthalene disulfonic acid, and naphthalene trisulfonic acid.

The composition ratio used in the present invention is nickel sulfate.
200-300g / l, phosphorous acid 0.2-20g / l, boric acid 20
~ 40g / l, O-sulfobenzoic acid imide, or naphthalene sulfonic acid, or their alkali metal salts 2
It is preferably in the range of -10 g / l. If the nickel sulfate is less than this range, the range of current density that can be plated becomes narrow, and plating burns easily occur.If it exceeds this range, the deposition rate of plating becomes high and the surface becomes rough, resulting in a uniform surface. Property and smoothness cannot be obtained. When the phosphorous acid is below this range, the amount of phosphorus deposited is reduced, and the selective removal property of the nickel-phosphorus layer after heating is reduced. The stress is high and the amount of curl increases. When the content of boric acid is less than this range, the buffering effect becomes small and the pH easily changes,
If it exceeds this range, it may be difficult to dissolve and precipitate. When the O-sulfobenzoic acid imide, naphthalene sulfonic acid, or alkali metal salt thereof is in this range or less, the effect of suppressing curling is small, and when it exceeds this range, the effect of suppressing curling does not change. ,
Not economical.

Using such a plating solution, a nickel-phosphorus layer is formed by electrolytic plating on a roughened surface of a copper foil which becomes a carrier having a roughness for strengthening adhesion with a resin on at least one surface, Further, a copper layer for forming a circuit can be formed on the surface. The thickness of the nickel-phosphorus layer is preferably 0.04 to 1.5 μm, more preferably 0.06 to 1.2 μm, and if it is less than 0.04 μm, the selective etching property of the nickel-phosphorus layer after heating is deteriorated. However, if the thickness exceeds 1.5 μm, it takes too much time to selectively etch the nickel-phosphorus layer, and the underlying copper layer may be damaged.

At this time, p of the nickel-phosphorus plating solution is used.
H is preferably in the range of 1.6 to 2.8, more preferably in the range of 1.8 to 2.2, and when the pH is less than 1.6, the concentration of precipitated phosphorus increases rapidly and the concentration of phosphorus is difficult to control. When it exceeds 2.8, plating burns occur, which is not preferable. As other plating conditions, the liquid temperature of the plating solution is preferably in the range of 40 to 60 ° C. If it is less than 40 ° C, the deposition rate of plating is small and the efficiency decreases, and if it exceeds 60 ° C, the deposition rate of plating is large. However, the energy consumption for controlling the plating bath and heating is large, which is not economical. Further, the current density is preferably in the range of 3 to 7 A / dm ² , and if it is out of this range, it becomes difficult to keep the ratio of nickel and phosphorus constant. When performing electrolytic plating,
It is preferable to perform air stirring or mechanical stirring because the uniformity of the plating solution is increased.

[0013]

By using the O-sulfobenzoic acid imide of the present invention, naphthalenesulfonic acid, or an alkali metal salt thereof, in a known nickel electroplating solution,
In a three-layer metal foil of carrier copper layer / nickel-phosphorus alloy layer / circuit copper layer, stress as an intermediate layer is relaxed.

[0014]

Example An electrolytic plating solution having the composition shown in Table 1 was prepared, and the plating stress and curl amount were measured.

[0015]

[Table 1]

(Plating stress) The test piece was plated with nickel-phosphorus plating at 0.2 μm on the test strip electrodeposition stress measuring piece using the plating solution and plating conditions shown in Table 1.
A sample having a thickness of m was formed to prepare each sample, and the measurement was performed by a test strip electrodeposition stress measuring method.

(Curl amount) A copper foil having a thickness of 18 μm is used as a carrier, and the roughened surface is plated with nickel-phosphorus having a thickness of 0.2 μm by using the composition shown in Table 1. A copper plate having a thickness of 5 μm was used and placed on a flat surface as shown in FIG. 1 to measure the curl amount at the end of the copper foil.

As can be seen from Table 1, in the examples of the present invention, the plating stress is small, and when the copper layer / nickel-phosphorus layer / copper layer has a three-layer structure, the curl amount can be reduced and the metal foil can be gripped. There is little gripping by the chuck or wrinkles during handling, and the transportability by machine is high. In comparison, as in Comparative Examples 1 to 3, those having the same composition as that of the present example but having an unsuitable composition ratio had a large plating stress, a large curl amount, and a chuck formed by a machine during conveyance. I couldn't grab and wrinkled.

[0019]

As described above, according to the present invention, it is possible to provide a method for producing a metal foil for a printed wiring board, which is excellent in suppressing curl generated at the end of the metal foil.

[Brief description of drawings]

FIG. 1 is a side view for explaining a measuring method used in an example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akashi Nakaso 1500 Ogawa, Shimodate, Ibaraki Pref., Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor Masashi Amata 1226 Shimoeren, Shimodate-shi, Ibaraki Nihon Denshi Co., Ltd. Shimodate factory

Claims (3)

[Claims] 1. A base material composed of nickel sulfate, phosphorous acid, and boric acid, and O- on the roughened surface of a copper foil serving as a carrier having a roughness for enhancing adhesion with a resin on at least one surface.
Using a plating solution containing sulfobenzoic acid imide, naphthalene sulfonic acids, or an additive selected from these alkali metal salts, a nickel-phosphorus layer having a thickness of 0.04 to 1.5 μm is formed by electrolytic plating, A method of manufacturing a metal foil for a printed wiring board, further comprising forming a copper layer for forming a circuit on the surface thereof. 2. O-sulfobenzoic acid imide, naphthalene sulfonic acid, or their alkali metal salts
The method for producing a metal foil for a printed wiring board according to claim 1, wherein the amount is in the range of -10 g / l. 3. The pH of the nickel-phosphorus plating solution is 1.6 to
The method for producing a metal foil for a printed wiring board according to claim 1 or 2, wherein the range is 2.8.