JPH07297547A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To prevent generation of a haloing phenomenon by conducting selective chemical plating without performing pretreatment on the printed wiring board where a conductive layer is formed by plating. CONSTITUTION:The circuit 2 on a board 1 is made of copper oxide, liquid insulating resin is coated on the substrate 1, the resin is cured, and a via hole 5 is formed. Then, the substrate is dipped into a chemical plating solution without having a pretreatment, a metal film is selectively formed on the via hole part, and the dissolution (haloing phenomenon) of the copper oxide caused by acid can be prevented by forming a mask for a heat treatment to be performed later.

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 multilayer printed wiring board in which conductive circuits are additionally formed sequentially by plating on an insulating layer, and more particularly to a method for manufacturing a multilayer printed wiring board having via holes. is there.

[0002]

2. Description of the Related Art Conventionally, a manufacturing technique of a multilayer printed wiring board in which a conductive circuit is additionally formed on an insulating layer by plating to form a via hole will be described with reference to FIG.

A copper foil is etched with a ferric chloride aqueous solution or the like on a substrate 1 made of an epoxy glass material or the like to form a conductive circuit 2 (FIG. 3 (a)). Then, the surface of the conductive circuit 2 is roughened with an acidic cupric chloride aqueous solution, and then the conductive circuit surface is oxidized with an alkaline potassium persulfate aqueous solution or the like to form copper oxide 3 (FIG. 3 (b)), (b ')). . This copper oxide formation is a technique widely used in printed wiring boards to structure the adhesion between the conductive circuit and the insulating layer.

Next, as shown in FIG. 3C, a photosensitive liquid insulating resin or the like is applied on the substrate 1 to a thickness of several tens of μm and dried to form an insulating layer 4.
To form. Then, the surface of the insulating layer 4 other than the via hole is cured and developed by ultraviolet irradiation to form a via hole 5 (FIG. 3 (d)). Incidentally, the thermosetting insulating resin is used instead of the photosensitive liquid insulating resin. The via hole can be formed by using a laser beam when used, then, after thermal curing, the surface of the insulating resin 4 is chemically roughened with an aqueous solution of permanganate, and then an aqueous solution of sulfuric acid, etc. Neutralize with.
A roughened surface 7 is formed on the surface of the insulating layer as shown in FIG. Next, the conductive layer 8 is formed by electroless copper plating and electrolytic copper plating (FIG. 4). By repeating such steps, a multilayer printed wiring board is manufactured.

[0005]

The above-mentioned prior art has the following drawbacks. That is, after the via hole is formed, when the insulating layer is treated with a permanganate aqueous solution and neutralized with a sulfuric acid aqueous solution, the sulfuric acid aqueous solution penetrates at the interface 9 (FIG. 4) between the conductive circuit 2 and the insulating layer 4 below the via hole 5. This causes a phenomenon in which the copper oxide 3 on the surface of the conductive circuit is dissolved (called a haloing phenomenon). Due to this haloing phenomenon, there is a problem that the insulating layer 4 is separated from the conductive circuit 2 below the via hole.

As a method for preventing this haloing phenomenon, a method of forming a copper oxide on a conductive circuit and then chemically reducing the entire surface of the copper oxide to improve the acid resistance is disclosed in JP-B-64-8.
No. 479, gazette. Although the haloing phenomenon is suppressed by this method, special chemicals and equipment are required, and the reduction of the entire surface of the conductive circuit causes an increase in the chemical cost. An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board, which solves the drawbacks of the prior art.

[0007]

According to the present invention, after forming copper oxide on the surface of a conductive circuit formed on a substrate, a step of forming an insulating layer and forming a via hole penetrating a desired conductive circuit in the insulating layer. Multi-layer printed wiring including a step, electroless plating on the surface of the conductive circuit under the via hole, a step of treating the insulating layer surface with an aqueous alkaline permanganate solution, and a step of forming a copper electrolytic layer on the insulating layer surface by plating A method for manufacturing a plate is provided.

[0008]

【Example】

(A) A copper foil is etched with a ferric chloride aqueous solution or the like on a substrate 1 made of an epoxy glass material or the like to form a conductive circuit 2 (FIG. 1A). Then, after roughening the surface of the conductive circuit 2 with an acidic cupric chloride aqueous solution, the conductive circuit surface is oxidized by oxidizing with an alkaline potassium persulfate aqueous solution, an alkaline sodium zincate solution, an aqueous solution of ammonium sulfide ammonium chloride, etc. Copper 3 is formed (Fig. 1
(B), (b ')).

(B) Next, a photosensitive liquid insulating resin is applied to the substrate 1 in a thickness of several tens of μm by a method such as a curtain coater, a roll coater or screen printing. For example, it is applied with a curtain coater to a thickness of 70 μm and dried by touch with the finger (90 ° C., 1 hour) to form the insulating layer 4 (FIG. 1C).

(C) Next, ultraviolet rays (integrated exposure amount 4000
˜6000 mJ) to be photo-cured, and the surface of the insulating layer 4 other than the formation of via holes is cured and then developed to form via holes 5 (via diameter 0.1 mm or more) (FIG. 1 (d)).
Heat cure (140 ° C., 1 hour).

(D) Next, in an electroless plating solution (Cu: 2
~ 3 g / l, NaOH: 9-12 g / l formaldehyde, (HCHO): 3-6 g / l, pH: 12-14)
Soak for about 20 minutes in the via hole to selectively remove about 0.3
Copper plating 6 is formed to a thickness of 0.6 μm (see FIG. 1).
(E)). In this treatment, the surface of the copper oxide 3 is HCHO.
As a result, it is reduced to copper and plated at the same time.

(E) The surface of the insulating layer 4 is polished by about 20 μm with a belt sander, jet scrub, buff or the like, for example, a belt sander, and an alkaline permanganate aqueous solution (KMnO ₄ : 40-60 g / l, normality: 1) is used. .0 to
As shown in FIG. 2 (a), the surface of the insulating layer 4 is chemically roughened with 1.2 N, 60 to 80 ° C. and neutralized with sulfuric acid (0.3 to 0.4 N, 40 to 50 ° C.). A roughened surface 7 is formed on the surface.

(F) Next, electroless copper plating and electrolytic copper plating are performed to form a conductive layer of several tens of μm, for example, a conductive layer of about 20 μm (FIG. 2 (b)). Further, the conductive layer may be formed only by electroless copper plating.

(G) By repeating the above steps, a multilayer printed wiring board is manufactured.

This embodiment is basically the same as the first embodiment, except that a thermosetting resin having no photo-curing property is used for the insulating layer and the via holes are formed by laser.

(B ') A thermosetting liquid resin is applied on the substrate 1 manufactured in (A) of Example 1 to a thickness of several tens of μm by a method such as a curtain coater, a roll coater, or screen printing. For example, apply 70 μm thick with a roll coater, dry to the touch (90 ° C, 1 hour), heat cure (170 ° C, 1 hour).
Then, the insulating layer 4 is formed.

(C ') Next, excimer laser, YA
A laser beam is irradiated by a G laser, a CO ₂ laser or the like to form a via hole of several tens μm. For example, an excimer laser is irradiated with ultraviolet light (200 to 300 nm) to form a via hole having a diameter of 100 μm (FIG. 1).
(D)).

The following steps are the same as the steps (D) to (G) of the first embodiment.

[0019]

As described above, according to the present invention, since the via hole portion is selectively plated without forming acid treatment which is a pretreatment for plating to form a mask, the circuit treatment can be performed by the acid treatment in the subsequent step. It has the result that there is no phenomenon of dissolving copper oxide (haloing phenomenon). In addition, since the special chemicals and devices required for the method of preventing the haloing phenomenon of the above-mentioned patent application publication are unnecessary, the present invention has a cost advantage that it can be performed on the present line.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a manufacturing process according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the manufacturing process of the embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a conventional manufacturing process.

FIG. 4 is a cross-sectional view illustrating a conventional manufacturing process.

[Explanation of symbols]

 1 substrate 2 circuit 3 copper oxide 4 insulating layer 5 via hole 6 selective copper plating 7 roughened surface 8 conductive layer 9 haloing phenomenon 10 prepreg 11 copper foil

Claims (3)

[Claims] 1. A step of forming an insulating layer after forming copper oxide on a surface of a conductive circuit formed on a substrate, a step of forming a via hole penetrating a desired conductive circuit in the insulating layer, and the via. A multilayer printed wiring board comprising: a step of electrolessly plating a surface of a conductive circuit below a hole; a step of roughening the surface of the insulating layer; and a step of forming a conductive layer on the surface of the insulating layer by plating. Manufacturing method. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the roughening step is a step of treating the surface of the insulating layer with an aqueous alkaline permanganate solution. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the electroless plating is electroless copper plating, and the method further comprises the step of forming the conductive layer by electrolytic copper plating.