JPH01124287A - Manufacture of printed-circuit board - Google Patents

Abstract

PURPOSE:To manufacture a high-density printed-circuit board whose adhesion force between a circuit and an insulating substrate is excellent in a simple process by a method wherein a copper thin layer is formed on a provisional support base material and is brought into contact with a treatment liquid containing an oxidizing agent so as to transform the copper thin layer into copper oxide, an insulating organic material is laminated on a copper oxide face, the support base material is removed, this assembly is brought into contact with a solution of a reducing agent and, after that, a conductive metal is plated. CONSTITUTION:A copper thin layer 2 is formed on a Teflon tape 1; the copper thin layer 2 is transformed into copper oxide 3. Then, an insulating organic glass cloth is pressure-laminated to an epoxy prepreg material 4; the Teflon film 1 is stripped off and removed; this assembly is immersed in an aqueous solution of a reducing agent for 10 minutes and the copper oxide layer is reduced. Then, an electroless plating operation 5 is executed; a resist pattern 6 is formed; after that, copper is electroplated; a copper pattern 7 with a thickness of 30mum is formed in a desired part. Then, the resist pattern 6 is stripped off by using methylene chloride; the electroless plated layer 5 and one part of a reduction-generated and/or copper oxide layer 2' are etched by using a solution of ammonium persulfate; a desired wiring pattern 7 is obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing printed wiring boards.

(Prior art) Printed wiring boards are manufactured using the etched foil method, in which circuits are processed by etching a copper-clad laminate, or electroless plating is used to plate conductive metal on an insulating substrate to a desired thickness for wiring. An additive method for forming a pattern, and an unclad method for forming a thin base metal layer on an insulating substrate and performing circuit processing by forming a plating resist, pattern plating, removing the plating resist, and then quick etching have been proposed.

(Problems to be Solved by the Invention) In the etched foil method, there is a problem of side etching, making it difficult to manufacture high-density wiring boards. In the additive method, it is necessary to use a roughening liquid to roughen the surface of the substrate with the contact agent layer.Most of the roughening liquids that can be used in this case contain an oxidizing agent and are highly toxic. This requires a poor working environment and special waste liquid treatment. In addition, components soluble in the roughening solution generally have poor electrical insulation properties.

For example, there is deterioration in moisture-resistant insulation properties and high-temperature insulation properties. Additionally, the heat resistance of the adhesive layer is low.

Since the dimensional change rate is also high, there are limits to its application to multilayer printed wiring boards that require high dimensional accuracy and through-hole connection reliability.

The fineness and high density of wiring boards in the uncladding method depend on the thickness of the underlying metal layer.

In other words, the thinner the underlying metal layer to be etched, the higher the etching accuracy. Therefore, when forming a high-density wiring board, it is based on a copper-clad laminate using thin copper foil of 5 to 9 μm, but after laminating aluminum foil (about 50 μm thick), which is a carrier for 2W4 foil, physical or chemical It has disadvantages such as the need to remove it.

There is also a method of processing circuits by applying electroless plating on a rough surface with good adhesiveness formed by a replica method using a substrate with a rough surface, but this requires a process to form a rough surface as an original. be.

The present invention has excellent adhesive strength between the 9 circuits and the insulating substrate, and
The present invention provides a method for manufacturing a high-density printed wiring board through simple steps.

(Means for Solving the Problems) The present invention first involves forming a thin metallic copper layer on a temporary holding base material by electroless plating, vacuum evaporation, sputtering, etc. Next, an oxidizing agent is applied. Metallic copper is turned into copper oxide by contacting it with a processing solution containing it. Next, an insulating organic material is laminated, and the holding base material is removed. Next, oxidation 1i1 on the surface of the insulating organic material
The layer is subjected to a reduction treatment to form metallic copper and/or cuprous oxide. Next, a metal copper layer is formed to a desired thickness by electroless plating or a combination of electroless copper and electrolytic copper plating to form a plating circuit pattern.

FIGS. 1 fa) to (fl) show an embodiment of the present invention.

A thin copper layer 2 with a thickness of 1.5 μm is formed on a Teflon tape (trade name, manufactured by Chias Corporation) 1 using a sputtering device MLH-6315D (manufactured by Japan Vacuum Technology Co., Ltd.) under the following conditions (see Fig. 1). (al, (bl).

Output: 1.5KW Heating: 120°C, 45 minutes Pressure: 5 x 10-''Torr Ar gas flow: 1 353CCM In addition to fluororesin film, the temporary holding base material that can be used in this case is polyimide film, roughened adhesive film. Examples include a metal copper plate coated with fluorine-based or polyimide resin, a commercially available glass plate, and a mirror-finished stainless steel plate.The thickness of the thin copper layer is 0.5 μm.
~10 μm.

Next, the copper thin layer 2 is made of copper oxide 3 (FIG. 1(C)). The copper oxide treatment conditions are, for example, as follows.

NaOH=15g/I Naa Po ・12Hz O-30g/INa
CLOz = 80 g/1 pure water = 1 liter amount Liquid temperature: -85±2°C M4 thin immersion time: -180 seconds Other methods for forming copper oxide include:

There is a method of treatment using a treatment solution containing an oxidizing agent such as sodium chlorite, sodium hypochlorite, potassium persulfate, potassium chlorate, or potassium perchlorate.

Note that electroless plating is a method for forming the copper thin layer 2, but in this case, unlike the sputtering method, a step of physically or chemically roughening the surface of the holding base material is essential.

Next, the insulating organic glass cloth-epoxy prepreg 4 is laminated under pressure (Fig. 1 (dl), the lamination condition is 35 m
kg/cj, 60 minutes at 170°C. Other insulating organic base materials to be laminated after forming the copper oxide 3 include glass cloth, resin sheets, etc. impregnated with thermosetting resins used in general copper-clad laminates, such as modified polyimide, polyimide, and phenol. Can be used. Thermoplastic materials such as polyethylene, polyethersulfone, and polyetherimide can also be used.

Next, the Teflon film 1 was peeled off and removed.

Reducing agent aqueous solution (sulfur borohydride 2g/l
2 is reduced copper and/or cuprous oxide. 2 is reduced copper and/or cuprous oxide.

In this case, the reducing agent aqueous solution is combined with formalin.

Hypophosphorous acid, sodium hypophosphite, hydrazine hydrate,
hydrazine sulfate, N,N'-)limethylborazane,
It may also be one in which one or more of N,N'-dimethyliborazene and the like are dissolved.

Next, electroless copper plating 5 is performed with the following composition and conditions.

CuSO4・5Hz O=10g/I EDTA・4Na=40g/l pH-12.3 37%HCHO=3ml/1 Plating solution addition amount - Small amount Plating solution temperature -70℃ Plating film thickness -3μm After washing with water and drying, photo The resist was laminated using a roll laminator, a positive mask was applied, and ultraviolet rays were irradiated, followed by spraying a developer and developing. The lines/spaces of the formed resist pattern 6 are 50 μm and 150 μm (
Figure 1(e)). Next, electrolytic copper plating (sulfuric acid steel plating) was applied to form a copper pattern 7 having a thickness of 30 μm on a desired portion.

The resist pattern 6 is removed with methylene chloride, and a portion of the electroless plating layer 5 and the reduced copper oxide layer 2' are etched using an ammonium persulfate solution (11 degrees: 50 g/l liquid level: 45 degrees Celsius). 1 ffl>, a desired wiring pattern 7 was obtained. In this case, the etching solution is an oxygen-based etchant such as copper or iron salt of ammonium persulfate, or an alkaline-based etchant (polyammonium persulfate-based).
etc. can be used.

After peeling off the Teflon film 1 in the above process 1
The wiring pattern can also be obtained by various processes such as those described below.

A. Form a resist pattern, reduce the copper oxide exposed outside the resist pattern, form a pattern 7 with a desired thickness by electroless plating, and peel off the resist pattern.

A method to remove copper oxide at the bottom of the resist pattern by line etching.

B. Forming a resist pattern, reducing copper oxide exposed outside the resist pattern area, and forming a pattern with a desired thickness using a combination of electroless plating and electroplating;
A method of peeling off the resist pattern and using quick etching to remove the copper oxide located at the bottom of the resist pattern.

C. Form a resist pattern and remove copper oxide exposed outside the resist pattern area by quick etching.
A method in which after the resist pattern is removed, the remaining copper oxide is reduced and electroless plating is applied.

D. Oxide 1i13 is reduced, and after forming a resist pattern, electroless plating or a combination of electroless plating and electroplating is used to form a pattern 7 with a desired thickness, and after peeling off the resist pattern, reduction formation is performed. A quick etching method to remove copper or cuprous oxide.

In the present invention, the thickness and shape of the copper and/or cuprous oxide layer formed on the resin substrate by the reduction treatment depend on the thickness of the copper thin layer formed on the holding base material or the conditions in the reduction treatment step. It can be adjusted by changing it appropriately.

The adhesive strength of cuprous oxide and/or copper produced by reduction to the resin substrate depends on the adhesive strength of oxidized steel to the resin substrate, and can be adjusted by changing the shape of the copper oxide.

(Effect of the invention) According to the present invention, the following effects could be obtained.

fl) It was possible to produce a high-density printed wiring board that had excellent in-line accuracy and insulation properties by etching, and had high adhesive strength with wiring metal.

(2) Since the surface of copper or cuprous oxide produced by reduction has fine irregularities, roughening treatment for resist pattern formation is not necessary.

There is no need for a catalyst treatment step for electroless plating, which significantly improves throughput.

(3) Compared to the replica method, it is easier to form an adhesive layer (cuprous oxide or copper layer in the shape of copper oxide) and can be used directly as a base layer for wiring formation, reducing costs and improving productivity. We were able to achieve this goal.

[Brief explanation of the drawing]

Figures 1 fa) to ff) are cross-sectional views illustrating the method of the invention. Explanation of symbols 1 Holding base material 2 Thin copper layer 3 Oxidation m 4 Prepreg 5 Electroless copper plating 6 Resist 7 Wiring pattern (a) (b). (c) Figure 1

Claims (1)

[Claims] 1. forming a thin copper layer on a temporary holding substrate and contacting it with a treatment solution containing an oxidizing agent to turn the thin copper layer into copper oxide;
A method for manufacturing a printed wiring board, which comprises laminating an insulating organic material on a copper oxide surface, removing a holding base material, contacting a reducing agent solution, and performing circuit processing including the steps of plating a conductive metal. .