JPH08191178A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE: To make a circuit flush with the board surface, and improve solderability of a land part, by setting transfer material on which a circuit pattern layer is formed in a metal mold, and performing de-smearing using oxidizing agent and/or acid after a circuit board is formed by transfer. CONSTITUTION: On an aluminum foil 1 80μm thick, insulating ink 2 is printed and hardened in a part where soldering is unnecessary. Copper paste ink 3 using epoxy resin as binder is printed on a necessary pattern part and hardened, thereby forming transfer material. It is so set in metal molds 4, 5 that the pattern printing surface faces the inside. Glass fiber-reinforced polyether imide in injection molded at an injection pressure of 600kgf/cm<2> , at a resin temperature of 350 deg.C, and at a metal mold temperature of 120 deg.C. A pin for forming a hole in the circuit board at the time of molding is formed in the metal mold. A board sheet of transfer material is peeled from a molded object. By using potassium permanganate, de-smearing is performed, unnecessary resin on the surface of a land part is dissolved and eliminated, and copper powder is exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit and an insulating ink layer which are buried in a substrate to form the same surface as the substrate surface, and
The present invention relates to a method for manufacturing a printed wiring board having excellent solderability of a land portion formed of a conductive ink.

[0002]

2. Description of the Related Art Conventionally, various methods for manufacturing a wiring board having a circuit formed on the same surface as a substrate surface, that is, a wiring board having a so-called horizontal circuit have been proposed. To describe representative ones, the first method is to coat a plating resist on a portion where a circuit is not required to be formed on a metal plate which is a base, and after metal plating is applied to an exposed portion of the metal plate, a prepreg is laminated, It is a method of heating and pressurizing and peeling only the base metal plate from the obtained laminate. The second method uses a transfer material in which a circuit pattern layer composed of conductive ink and insulating ink is designed on the base sheet, and the simultaneous circuit pattern layer is transferred at the time of molding the insulating substrate, and then the transfer material is transferred. This is a method of peeling the substrate sheet, and in order to stabilize the solderability of the land portion, polishing is performed to remove unnecessary resin (Japanese Patent Laid-Open No. 62-237793).

However, in the first method, when the underlying metal plate is peeled off, the coating resist or plating left on the metal plate may remain on the metal plate due to adhesion problems, and the circuit may not be completely transferred. In addition, the second method has a drawback in that even if the solder is polished, the solder only adheres to the scraped metal powder and does not uniformly adhere to the land.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a printed wiring board in which the circuit is made flush with the board surface and the land portion has good solderability.

[0005]

The present invention uses a transfer material in which a circuit pattern layer composed of an insulating ink and a conductive ink is provided on a base sheet, and the transfer material is mounted in advance in a mold. , A step (A) of molding a molded body for a circuit board by press-fitting a molten resin into a mold, peeling a substrate sheet of a transfer material from the molded body, transferring a circuit pattern layer on the transfer material,
Manufacturing of a printed wiring board, comprising a step (B) of forming a circuit board in which the circuit and the insulating ink pattern are flush with the molded body, and a step (C) of treating the circuit board with an oxidizing agent and / or an acid. Method.

The base sheet of the transfer material used in the present invention includes metal foils such as aluminum foil and stainless steel foil, polyester, polyimide, polyether sulfone, polysulfone, polyether ether ketone,
A single or composite film having heat resistance such as polyphenylene sulfide can be used.

The conductive ink includes silver, copper, aluminum, nickel, gold, carbon, graphite, etc. as conductive powder, and heat-resistant polyether sulfone, polyether imide, polyallyl sulfone, poly It can be obtained by using a thermoplastic resin such as arylate or a thermosetting resin such as an epoxy resin, a phenol resin, a polyester resin and an acrylic resin, and optionally using a surfactant, an antioxidant and the like.

Insulating inks are used as binders in the same manner as conductive inks, such as thermoplastic resins such as polyether sulfone, polyether imide, polyallyl sulfone, polyacrylate, etc., or epoxy resin, fettle resin, unsaturated polyester resin, acrylic. A thermosetting resin such as a resin is used, and if necessary, an insulating powder is used. As the above-mentioned insulating powder, inorganic powder such as mica, beryllium oxide, talc, magnesium oxide, silicon dioxide, alumina, boron nitride, zirconium oxide can be used, and if necessary, a surfactant, a thixotropic agent, etc. are added.

As a method for molding the transferred material, injection molding is preferable because of its high efficiency, but compression molding or transfer molding may be used. Thermoplastic resin and thermosetting resin can be applied to the molten resin. In the case of thermoplastic resin, polyethylene, polypropylene, polycarbonate, polyacetal, polyamide, ABS resin, AS resin, polysulfone, polyphenylene sulfide, polyethylene terephthalate, polyphenylene Oxide and the like, thermosetting resin, phenol resin, epoxy resin,
Examples include unsaturated polyester resins, urethane resins, melamine resins, diallyl phthalate resins and the like.

After forming the circuit board by transfer, a desmear process for melting the resin is performed as a method for removing the unnecessary resin in the land portion. In the present invention, the desmear treatment includes a method using an acid such as sulfuric acid and a method using an oxidizing agent such as potassium permanganate, but the latter has stronger dissolution and desorption force and can remove the unnecessary resin in a short time. Also, both may be combined.

[0011]

The method for manufacturing a printed circuit board according to the present invention will be described below with reference to specific examples. On an aluminum foil (1) with a thickness of 80 μm, an insulating ink (2) is printed and hardened on a portion where soldering is unnecessary, and a copper paste ink (3) using an epoxy resin as a binder is printed on a required pattern portion. A transfer material is prepared by curing (FIG. 1).

Next, as shown in FIG. 2, this transfer material is set in the molds (4) and (5) with the pattern printing surface inside, and glass fiber reinforced polyetherimide is injected at a pressure of 600 Kgf / c.
Injection molding was performed at m ² , resin temperature of 350 ° C., and mold temperature of 120 ° C. It is preferable that the mold is provided with a pin for forming a hole in the circuit board at the time of molding because it is possible to omit the post-processing of the circuit board. As shown in FIG. 3, the substrate sheet of the transfer material is peeled from the molded body (6).

Next, desmear treatment with potassium permanganate is performed in the step of FIG. 4 to dissolve and remove the unnecessary resin (8) on the surface of the land portion to expose the copper powder (7). Figure 5
An enlarged cross-sectional view of the land portion before and after desmearing is shown in FIG. The printed wiring board thus obtained had the insulating ink and the circuit layer on the same plane as the circuit board, and the solderability of the land portion was extremely excellent, and other problems did not occur in manufacturing. .

[0014]

According to the present invention, a desmearing treatment with an oxidizing agent and / or an acid is performed after forming a circuit board by molding transfer, so that a land portion is excellent in solderability in a horizontal circuit, and a solder bridge is also used. It is possible to obtain a printed circuit board which is more advantageous than the current subtractive method. Further, the circuit can be easily changed because it is only necessary to use another transfer material.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a transfer material.

FIG. 2 is a schematic cross-sectional view of a mold for molding a circuit board.

FIG. 3 is a cross-sectional view of the printed wiring board after transfer.

FIG. 4 is a process drawing of desmear.

FIG. 5 is an enlarged cross-sectional view of a land portion before and after desmear. (A)
Is before Desmear, (B) is after Desmear.

[Explanation of symbols]

 1 Aluminum foil 2 Insulating ink 3 Copper paste ink 4 Mold 5 Mold 6 Molded body 7 Copper powder 8 Unnecessary resin

[Procedure amendment]

[Submission date] September 24, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

After forming the circuit board by transfer, as a method for removing the unnecessary resin in the land portion, a resin dissolution treatment, which is the same treatment as the desmear treatment for removing the smear in the through hole of the multilayer board, is performed. In the present invention, the resin dissolution treatment includes a method using an acid such as sulfuric acid and a method using an oxidizing agent such as potassium permanganate, but the latter has a stronger dissolution desorption force and can remove the unnecessary resin in a short time. Also,
You may combine both.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Next, the obtained substrate is subjected to resin dissolution treatment in the step shown in FIG. Substrate 0.8N caustic solution
Immerse in (80 ° C) for 7 minutes, swell and wash with water.
It is immersed in a 0 g / l potassium permanganate solution for 6 minutes and then washed with water. Then, it is immersed in a 10% sulfuric acid solution for 5 minutes to neutralize potassium permanganate and wash with water. Through these steps, the unnecessary resin (8) in the land portion is dissolved and removed, and the copper powder (7) is exposed. FIG. 5 shows enlarged cross-sectional views of the land portion before and after the resin dissolution treatment. The printed wiring board thus obtained had the insulating ink and the circuit layer on the same plane as the circuit board, and the solderability of the land portion was extremely excellent, and no other manufacturing problems occurred. .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

According to the present invention, by forming a circuit board by molding transfer and then dissolving the resin with an oxidant and / or an acid, the solderability of the land portion is excellent in a horizontal circuit and the solder bridge It is possible to obtain a printed circuit board which is more advantageous than the current subtractive method. Further, the circuit can be easily changed because it is only necessary to use another transfer material.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a process diagram of resin dissolution processing.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 is an enlarged cross-sectional view of a land portion before and after a resin dissolving process.
(A) before resin dissolution treatment, (B) after resin dissolution treatment.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (1)

[Claims] 1. A transfer material, in which a circuit pattern layer composed of an insulating ink and a conductive ink is provided on a base sheet, the transfer material is mounted in advance in a mold, and a molten resin is placed in the mold. Step (A) of forming a molded body for circuit board by press-fitting, peeling the base sheet of the transfer material from the molded body, transferring the circuit pattern layer on the transfer material, and making the circuit and the insulating ink pattern flush with the molded body. A method of manufacturing a printed wiring board, comprising: a step (B) of producing a circuit board having the following structure; and a step (C) of treating the circuit board with an oxidizing agent and / or an acid.