JPH0724333B2 - Manufacturing method of insulating substrate with thin metal layer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an insulating substrate with a thin metal layer, which is used for manufacturing a printed wiring board.

(Prior Art) Copper-clad laminates used in the production of printed wiring boards include copper foil electrolytically deposited on a stainless steel rotating drum and paper or glass base material impregnated with a thermosetting resin. There was a laminate of the prepared prepreg. Further, as a film with a copper foil for a flexible wiring board and a multilayer flexible wiring board, for example, there is one in which a polyimide film and a rolled copper foil are thermocompression bonded via an adhesive. In this case, as the thickness of the copper layer, the one having a large thickness of 18 μm, 35 μm, and 50 μm was the mainstream.

As a method of manufacturing a printed wiring board using a copper-clad laminate or a film with a copper layer as described above, there are an etched foil method of etching a copper-clad laminate and the like for circuit processing, and a surface treatment for resist formation. There is an unclad method that performs circuit processing by resist formation → plating → plating resist removal → quick etching.

The etched foil method has a problem of side etching, and it is difficult to manufacture a high-density wiring board. The unclad method is based on a copper-clad laminate using copper foil of 5 to 9 μm. The fineness and high density of wiring in this method depends on the thickness of the underlying metal layer. That is, the thinner the underlying metal layer to be etched, the higher the etching accuracy. Therefore, when forming high-density wiring, the base is a copper-clad laminate using a thin copper foil of 5 to 9 μm.
Disadvantages, such as the need to physically or chemically remove the aluminum foil, which is the carrier of the copper foil, after lamination, and the need for rough surface treatment with good adhesion to, for example, resist after removing the carrier There is.

Other methods for forming a thin base metal layer include electroless plating, vacuum deposition, and sputtering. The electroless plating method requires a step of treating the surface of the insulating substrate with a physical or chemical method to make the surface of the substrate hydrophilic and rough, and the adhesive force between the generated metal layer and the substrate is low. For those that do not require high heat resistance, there is also a method of roughening the adhesive layer in which a catalyst for electroless plating is mixed with a rubber-based resin and then performing electroless plating. The metal catalyst remains between the circuits and in the adhesive layer, resulting in a defect in characteristics.

In the vacuum vapor deposition method and the sputtering method, for example, when a glass cloth-epoxy laminate or a glass cloth-polyimide laminate is used, vapor deposition due to the water content adsorbed on the glass cloth and the residual solvent component. Moisture and solvent are gasified under the high vacuum required for sputtering and spattering, causing peeling and voids at the glass cloth-resin interface. Further, it has a drawback of low throughput.

The present invention provides a method for manufacturing an insulating substrate with a thin metal layer that enables high-density wiring.

(Means for Solving the Problems) In the method of the present invention, first, after forming copper oxide on the copper foil surface, an insulating organic material is laminated facing the copper oxide layer, and the copper foil portion is removed by etching. Next, the copper oxide layer remaining on the surface of the insulating organic material is subjected to reduction treatment to obtain metallic copper and / or cuprous oxide. The metal layer may be plated to a desired thickness by electroless copper plating or a combination of electroless copper plating and electrolytic copper plating.

1 (a) to 1 (d) show an embodiment of the present invention.

Copper oxide 2 is formed on the surface of a 35 μm copper foil 1 for copper-clad laminate (FIGS. 1 (a) and (b)). The copper oxide treatment conditions are, for example, as follows.

_{NaOH = 15g / NaPO 4 · 12H} 2 O = 30g / NaClO 2 = 80g / become pure water = 1 amounts solution temperature = 85 ± 2 ° C. In addition, as a method of forming a copper oxide surface of the copper foil, the chlorite There is a method of treating with a treatment liquid containing an oxidizing agent such as sodium acid salt, sodium hypochlorite, potassium persulfate, potassium chlorate, and potassium perchlorate. As a pretreatment for the copper oxide treatment, the copper foil is immersed in neutral clean which is a degreasing liquid manufactured by Shipley Co., Ltd. for 5 minutes, washed with running water, and further
Immerse in 10% sulfuric acid for 2 minutes, wash with running water, and dry at 80 ° C for 30 minutes.

In this case, the copper foil used may be another metal foil, a metal plate, an organic film or the like having a copper layer formed on a support. When using a foil made of only copper, there is no technical limit to the thickness, but in terms of handling and price, 10
˜70 μm is preferred.

Moreover, in order to enhance the adhesive force between the resin base material and the metal layer,
It is preferable that the copper foil surface is roughened in advance. The roughening methods include polishing, honing, etching, electroplating and electroless plating.

Next, it is pressure-laminated with an insulating organic glass cloth-epoxy prepreg 3 (FIG. 1 (c)). Laminating condition is molding pressure 35kg
/ cm ² , 170 ℃ for 60 minutes. As the insulating organic material to be laminated after forming the copper oxide 2, glass cloth impregnated with thermosetting resin such as modified polyimide, polyimide, or phenol, which is used for general copper-clad laminate, resin sheet, etc. are used. be able to.

Further, thermoplastic materials such as polyethylene, Teflon, polyether sulfone and polyether imide are also used.

Next, the copper foil 1 is removed by etching using a polyammonium salt-based etching solution. In this case, the copper oxide 2 remains on the surface of the organic base material 3 without being etched.

After washing with water, reducing agent aqueous solution (sodium borohydride 2 g /,
The copper oxide layer 2 is reduced by immersing it in NaOH 12.5 g /, liquid temperature 55 ° C.) for 10 minutes to form cuprous oxide or metallic copper 4. In this case, as a reducing aqueous solution, one of formalin, hypophosphorous acid, sodium hypophosphite, hydrazine hydrate, hydrazine hydrochloride, hydrazine sulfate, N, N'-trimethylborazane, N, N'-dimethylborazene or the like, or It may be a mixture of two or more kinds.

In addition to the above steps, the metal layer may be plated to a desired thickness by electroless copper plating with the following composition and conditions, or a combination of electroless copper and electrolytic copper plating.

CuSO ₄・ 5H ₂ O ＝ 10g / EDTA ・ 4Na ＝ 40g / pH = 12.3 37% HCHO ＝ 3 / plating solution addition amount ＝ small amount plating solution temperature ＝ 70 ℃ plating film thickness ＝ 3μm The re-laminated board can be used not only as an inner layer circuit board for wiring boards, but also as the outermost layer of a multilayer wiring board.

In the present invention, the copper oxide formed on the copper foil is a fibrous to columnar or granular crystal having a size of submicron or less. Therefore, copper oxide having high adhesiveness remains on the surface of the resin substrate from which the copper foil treated with copper oxide and the organic insulating material such as resin are laminated and the copper foil is removed.

Further, the thickness and shape of the copper and / or cuprous oxide layer formed on the resin substrate by the reduction treatment can be adjusted by appropriately changing the conditions in the copper oxide forming step or the reduction treatment step.

(Effect of the invention) In the present invention, since the thickness of the metal layer is as thin as 0.1 to 5 µm, the line width accuracy by etching in the wiring board manufacturing process by the unclad method is remarkably improved, and the high resolution positive Line / space is 30/3 if liquid resist is applied
Enables high-density wiring of about 0 μm.

Also, the adhesion between the insulating substrate and the metal layer is high, and the reliability is improved. Since the reduced copper or cuprous oxide surface and the resin substrate surface have fine irregularities, no roughening treatment is required for resist pattern formation or multilayer adhesion, and a catalyst for electroless plating is also required. Since no processing steps are required, the throughput is significantly improved.

[Brief description of drawings]

1 (a) to 1 (d) are cross-sectional views showing the method of the present invention. Explanation of code 1 …… Copper foil 2 …… Copper oxide 3 …… Prepreg (insulating base material) 4 …… Copper and / or cuprous oxide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyasu Minagawa 1500 Ogawa, Shimodate, Ibaraki Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (56) Reference JP-A-61-279531 (JP, A) JP 56-5079 (JP, B2)

Claims (1)

[Claims] 1. A copper foil is brought into contact with a treatment liquid containing an oxidizing agent to form copper oxide on the copper foil surface, an insulating organic material is laminated on the copper oxide surface, and an etching liquid is brought into contact therewith. A method for producing an insulating substrate with a thin metal layer, which comprises removing a copper foil and then bringing it into contact with a reducing agent solution.