JP2984625B2 - Multilayer printed wiring board manufacturing method - Google Patents

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, and more particularly to a method for manufacturing a multilayer printed wiring board using a build-up method.

[0002]

2. Description of the Related Art As electronic devices have become smaller and have higher performance, high-density wiring of multilayer printed wiring boards on which electronic components are mounted has been demanded. Insulating resin and conductive circuit are alternately formed on
A method of manufacturing a multilayer printed wiring board of a build-up method in which interlayer connection is performed by via holes is disclosed. In order to achieve thin and high-density mounting of electronic components on the multilayer printed wiring board, an opening is provided on the surface of the multilayer printed wiring board, and the electronic component is bonded and mounted in the opening.

A conventional method for manufacturing a multilayer printed wiring board having openings will be described with reference to FIG. Gold plating is performed only on the pad 3 that is to be the open portion on the insulating substrate 1 such as an epoxy glass material on which the conductive circuit 2 is formed (FIG. 3A) to form a bonding pad portion 4 (FIG. 3 (b)). This gold plating is performed for two purposes: a metal resist at the time of etching in a later step and a surface treatment for bonding of the pad 3 at the time of mounting. Gold plating is about 0.3μ using an electroless gold plating bath using borohydride as a reducing agent.
A gold plating film having a thickness of about m is coated on the bonding pad portion 4.

Next, a conductive circuit 2 is formed using an aqueous cupric acid chloride solution.
After roughening the surface, the conductive circuit surface is oxidized with an alkaline potassium persulfate aqueous solution or the like to form copper oxide 5 (FIG. 3).
(C)). This copper oxide formation is used to improve the adhesion between the conductive circuit and the insulating resin built up thereon.

Next, as shown in FIG. 3D, a photosensitive liquid resin (including both photo-curable and thermo-curable components) is applied to the insulating substrate 1 to a thickness of several tens μm and dried. The layer 13 is formed. Then irradiate with ultraviolet light using a mask film,
The surface of the insulating layer 13 other than the opening 7 and the via hole 8 is photo-cured and then developed to form the opening 7 and the via hole 8 (FIG. 3E).

Next, after heat curing (130 ° C., 2H), the insulating layer 1
3 After mechanical polishing the surface and roughening with permanganate aqueous solution,
After copper plating, etching is performed to form a conductive circuit 11, and a multilayer printed wiring board 12 having openings 7 and via holes 8 is completed (FIG. 3F). The opening 7
Is also called a counterbore.

[0007]

The problem with the prior art described above is that the opening 7 is formed in the insulating layer 13 and, after thermosetting, the surface of the insulating layer 13 is improved in adhesion to the copper-plated insulating layer 13. When mechanical polishing is performed to prevent the bonding pad portion 4
Is liable to be polished by a mechanical polishing buff or the like, resulting in a defect. For this reason, it often happens that the bonding pad portion 4 cannot be bonded.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a multilayer printed wiring board which solves the above-mentioned problems of the prior art.

The method of manufacturing a multilayer printed wiring board according to the present invention comprises the steps of forming a conductive circuit on an insulating substrate; forming a bonding pad portion by partially plating a desired circuit of the conductive circuit with gold; Roughening the surface of the conductive circuit excluding the bonding pad portion, applying a photosensitive insulating resin on the insulating substrate to form a first insulating layer, and exposing the surface of the first insulating layer Developing and forming an opening and a via hole on a desired circuit of the conductive circuit so that the surface of the bonding pad portion of the insulating layer is exposed; and filling and coating the opening with a photosensitive insulating resin. Forming a second insulating layer and exposing; a step of mechanically polishing and chemically roughening the surfaces of the first insulating layer and the second insulating layer; and a step of plating and etching on the first insulating layer and the via. Led to the hall Forming a circuit, the second
Removing the insulating layer.

In the present invention, since the second insulating layer made of a photosensitive insulating resin is formed in the opening where the bonding pad portion is formed and the polishing is performed, the bonding pad is protected from mechanical polishing. In addition, there is an effect that the first insulating layer can be uniformly polished. The photocured surface layer of the second insulating layer has an effect of protecting the bonding pad when the first insulating layer is chemically roughened.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an enlarged cross-sectional view of a main part of a substrate, illustrating a process sequence from formation of a conductive circuit on an insulating substrate to formation of an opening and a via hole in a first insulating layer according to an embodiment of the present invention. . FIG. 2 is a cross-sectional view of the first embodiment after forming a conductive circuit on the first insulating layer and the via hole from the formation of the second insulating layer in the opening of the first insulating layer according to the embodiment of the present invention.
FIG. 4 is an enlarged cross-sectional view of a main part of a substrate for explaining a process order until an insulating layer is removed.

First, an insulating substrate 1 made of an epoxy glass material or the like is used.
A conductive circuit 2 is formed thereon using a conventional print etching technique (FIG. 1A). A circuit to be bonded by the conductive circuit 2 is indicated by a pad 3. The copper foil of the conductive circuit of the insulating substrate 1 may have a thickness of 18 μm or 35 μm. Next, the bonding portion of the pad 3 is plated with gold to form a bonding pad portion 4 (FIG. 1).
(B)). Gold plating is electroless gold plating bath (KAu (C
N) ₂ : 0.86 g / l, KCN: 6.5 g / l, KO
H: 11.2 g / l, KBH ₄ : 10.8 g / l)
Immersion at 0 ° C. for 15 minutes to form a gold plating film having a thickness of about 0.3 μm.

Next, the surface of the pad 3 and the surface of the other conductive circuit 2 except for the bonding pad portion 4 plated with gold with an aqueous solution of acidic cupric chloride are roughened, and then treated with an aqueous solution of alkaline potassium persulfate to form copper oxide 5. I do. To form copper oxide 5,
Alkaline sodium chlorite, potassium sulfide-ammonia chloride aqueous solution or the like may be used. The formation of the copper oxide 5 is performed in order to improve the adhesion between the conductive circuit and the insulating layer as in the above-described conventional technique.

Next, using a curtain coater, a liquid photosensitive insulating resin containing an epoxy resin as a main component is applied on the insulating substrate 1 and dried by touching at a temperature of 90 ° C. for 60 minutes to a thickness of about 60 μm. First insulating layer 6 is formed (FIG. 1
(D)). This photosensitive insulating resin contains both photo-curable and thermo-curable components, and has the property of being incapable of developing when thermally cured at 130 ° C. for about 2 hours. The application of photosensitive insulating resin
A method such as a roll coater or screen printing may be used.

Next, using a mask film, ultraviolet rays are selectively irradiated at an integrated exposure dose of 4000 to 6000 mJ / cm ² , and the opening 7 and the via hole 8 are formed in the first insulating layer 6.
Then, the surface of the insulating layer 6 except for the formation of the photo-curing layer is developed after photo-curing to form an opening 7 and a via hole 8 (FIG. 1E). By this ultraviolet irradiation, the surface of the insulating layer 6 is cured at a depth of about 10 μm. Next, the substrate is thermally cured at a temperature of 130 ° C. for about 2 hours. By this heat curing, the insulating layer 6 is considerably stabilized chemically.

Next, the photosensitive insulating resin is coated with a curtain coater,
A photosensitive insulating resin is applied on the substrate by a method such as a roll coater or screen printing, and the opening 7 is filled with the second insulating layer 9 (FIG. 2A). As the photosensitive insulating resin, a resin whose main component is an epoxy resin and whose surface is hardened to a depth of 10 μm by ultraviolet irradiation is suitable, and the same liquid photosensitive insulating resin as the first insulating resin layer is used. Is also good. By adjusting the surface hardening depth of the second insulating layer so as to be the same as the surface hardening depth of the first insulating layer, when removing the surface hardened film of the first insulating layer by mechanical polishing in a later process. , Second
The surface hardened film of the insulating layer can be effectively removed at the same time. When forming the second insulating layer, the photosensitive insulating resin may be filled in the via hole 8 in the same manner as the opening.

Next, the second insulating layer filled in the opening is touch-dried at a temperature of 90 ° C. for about 60 minutes, and then irradiated with ultraviolet rays at a cumulative exposure amount of 4000 to 6000 using a mask film.
mJ / cm ^{2 and} irradiate the surface of the second insulating layer 9 to a depth of about 1
Light cured at 0 μm. After the photo-curing, the photosensitive insulating resin for forming the second insulating layer attached to the portion other than the opening may be developed to remove it.

Next, the surface hardened films of the first insulating layer 6 and the second insulating layer 9 are removed by polishing, for example, with a belt sander using a method such as a buff or a belt sander. The thickness at which the insulating layer is polished with the belt sander is at least the first and second.
In this case, the resin polishing depth of the mechanical polishing was set to about 20 μm in order to completely remove the surface cured film. During this mechanical polishing, the pad 3 is not polished because it is protected by the second insulating layer 9. Then an alkaline permanganate aqueous solution (KMnO _4: 40 to 60
g / l, alkali normality: 1.0 to 1.2 N, liquid temperature: 60
-80 ° C) and neutralized with a sulfuric acid reducing agent. A roughened surface 10 is formed on the surfaces of the first insulating layer 6 and the second insulating layer 9 (FIG. 2B).

Next, electroless plating and electrolytic copper plating are performed to form a conductive layer having a thickness of about 20 μm, followed by etching with ferric chloride or the like to form a conductive circuit 11 (FIG. 2C). Further, the second insulating layer 9 is removed by development to expose the bonding pad portion 4 of the pad 3, and the opening (counterbore portion) 7 is formed.
Printed wiring board 12 having via holes 8
Is obtained (FIG. 2D).

[0020]

A first effect of the present invention is that a second insulating layer made of a photosensitive insulating resin is formed in an opening where a bonding pad portion is formed, and polishing is performed. Because it is protected, the reliability of the bonding can be improved.

The second effect of the present invention is that the opening is filled with the second insulating layer and the substrate surface is flattened, so that the first insulating layer can be uniformly polished.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a substrate, illustrating a process from forming a conductive circuit on an insulating substrate to forming an opening and a via hole in a first insulating layer according to an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention, in which a second insulating layer is filled in a first insulating layer opening, a conductive circuit is formed on the first insulating layer and a via hole, and then the second insulating layer is removed. It is an expanded sectional view of the important section of a substrate for explaining a process order until.

FIG. 3 is a cross-sectional view of a main part of a substrate for describing a process sequence of a conventional method for manufacturing a multilayer printed wiring board having openings.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Conductive circuit 3 Pad 4 Bonding pad part 5 Copper oxide 6 First insulating layer 7 Opening 8 Via hole 9 Second insulating layer 10 Roughened surface 11 Conductive circuit 12 Multilayer printed wiring board 13 Insulating layer

Claims (3)

(57) [Claims] 1. A step of forming a conductive circuit on an insulating substrate, a step of forming a bonding pad portion by partially plating a desired circuit of the conductive circuit with gold, and a surface excluding the bonding pad portion of the conductive circuit. Surface roughening;
Applying a photosensitive insulating resin on the insulating substrate to form a first insulating layer; and exposing and curing a desired portion of the surface of the first insulating layer and developing the exposed portion. Forming an opening so as to be exposed and a via hole on a desired circuit of the conductive circuit, filling and coating the opening with a photosensitive insulating resin to form a second insulating layer, and exposing and hardening; A step of chemically polishing and roughening the surfaces of the first and second insulating layers, and a step of forming a conductive circuit on the first insulating layer and in the via hole;
Removing the second insulating layer. 2. The method according to claim 1, wherein the exposure hardening depth of the second insulating layer is the same as the exposure hardening depth of the first insulating layer. 3. The mechanical polishing thickness of the first and second insulating layers is at least the greater of the exposure hardening depths of the first and second insulating layers. Production method of multilayer printed wiring board.