JPH0284791A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To change a wiring board into multilayers easily, and to obtain a method through which continuous production is enabled, by easily manufacturing the wiring board with a fine circuit pattern and acquiring the wiring board with a smooth surface by forming a circuit onto a conductive thin-foil with the smooth surface through plating and shaping an insulating layer onto the circuit. CONSTITUTION:The reverse image of a desired circuit is formed onto a thin-foil 1 having conductivity and a smooth surface by a plating resist, and a conductor circuit 2 is shaped through electroplating or chemical plating. Said plating resist is removed, and the conductor circuit 2 is fixedly embedded with a synthetic resin 3 in a quantity sufficient for coating the conductor circuit 2. The dry film of the plating resist is thermocompression-bonded with the surface of the aluminum box 1, the reverse image of the circuit is baked and developed through a photomask method, and the circuit 2 is shaped through copper plating while employing the aluminum foil 1 as a cathode. The resist is removed, the upper section of the surface is coated with a polyimide resin, and a wiring board (a) is acquired through heating and curing. The wiring (a) is dipped into a dilute alkali aqueous solution, whereby the aluminum foil 1 is removed and the wiring board (b) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing wiring boards used in the electronics field, such as printed circuit boards and PGASTAB.

[Conventional technology]

Printed wiring boards can be broadly classified into the following three types based on their manufacturing method. (2) the subtract method, in which a copper foil bonded to the surface of an FLL board is etched to form a desired circuit; (2) the abu-ibub method, in which a conductive circuit is formed by electrolessly plating a copper circuit on the surface of an insulating board; 3) A method of forming a desired conductor circuit on a smooth metal surface and transferring it to an insulating substrate.

[Problem to be solved by the invention]

The above-mentioned conventional techniques are all characterized by forming a conductor circuit on a ready-made substrate, but there are the following problems when using such methods.

(1) Advanced technology is required to bond the conductor and insulating substrate.

That is, an adhesive that can withstand solder temperature and has excellent electrical properties is required, and the adhesive surface of the conductor requires advanced treatment such as uneven treatment.

(2) The surfaces of the conductor and insulating substrate do not match.

(3) Dimensional changes due to thermal expansion, moisture absorption and desorption of the insulating substrate cause problems in mounting components.

(4) The surface roughness of the insulating substrate is large, making it impossible to form fine circuits. Currently, the limit for mass production is 100 μm.

(5) Advanced technology is required to balance the circuit processability (drilling, through-hole plating, process transfer due to warping, twisting, etc.) of the insulating substrate.

The present invention provides a method of manufacturing a wiring board that makes it possible to solve or significantly reduce such problems.

[Means to solve the problem]

That is, in the present invention, a plating resist is applied to a continuous conductive thin foil such as aluminum foil, a reverse image of a desired circuit is formed with the resist, a circuit is formed by electroplating or chemical plating, and then the plating resist is applied. This method is characterized by manufacturing a wiring board by peeling and removing, filling the removed area with an insulating synthetic resin, and further covering the conductor to embed and fix the conductor circuit.

The present invention will be explained below with reference to the process diagram shown in FIG. Step (2) is the preparation of a conductive thin foil. The conductive m-foil is a metal foil made of aluminum, nickel, copper, tin, iron, or stainless steel, or a thin foil made of a plastic film such as polyester or polycarbonate on which a thin metal film is formed. Its thickness is 10. 50 from un
The thickness is preferably about 0 μm, preferably about 20 to 100 μm. There is no particular restriction on the width, but a width of 300 to 6001 cm provides excellent workability. By providing carrier guide holes (perforations) on both sides of the thin foil that match the width of the wiring board, feeding the thin foil, post-processing, or positioning during multilayering becomes easier.

The surface of the conductive thin foil is desirably smooth in terms of circuit miniaturization, and the surface roughness is preferably 10 μm or less, more preferably 5 μm or less.

Further, the surface of these Fi foils may be subjected to surface treatment within a range that does not interfere with plating.

Next, step (■) is the process of applying a plating resist to form the circuit pattern.The plating resist can be in the form of a photosensitive dry film, liquid resist can be dried into a solid film, or it can remain in liquid form. Liquid resists that can be used to form a pattern include photo-curable resists and heat-curable resists, and photomask methods, silk screen methods, offset methods, and the like can be applied.

The circuit pattern formed in this step proceeds to the next plating step (2). Plating can be either electroplating or chemical plating. In the case of electroplating, electroplating is performed by a conventional method using a conductive thin foil as a cathode and a metal such as copper or nickel that forms a conductive circuit as an anode. In the case of chemical plating, the conductive thin foil is immersed in an aqueous metal salt solution containing a reducing agent. The thickness of the conductor circuit formed by plating is preferably 10 to 30 μm.

Next, the plating resist is peeled off and removed using a method suitable for the resist used in step ① (mechanical polishing, alkaline method, solvent method, etc.). However, on the traces of the resist that was removed afterwards,
Insulating synthetic resin is applied in the process. The synthetic resin is applied by coating and drying in the case of a liquid resin, and by UV or electron beam irradiation in the case of a solvent-free photocurable resin.

In the case of water-dispersible resins, electrodeposition is also possible. For solid resin, methods such as melt coating and powder coating are used. The coating thickness is not particularly limited as long as it is sufficient to sufficiently cover the conductor circuit. The types of resins used include thermosetting,
Any thermoplastic resin is possible, such as phenolic resin, epoxy resin, polyimide resin, polyester resin, DA
Examples include thermosetting resins such as P resin, melamine resin, urethane resin, and their prepregs, and thermoplastic resins such as polyamide, polybonate, polyethersulfone, polyetheretherketone, PET resin, PBTm resin, and polysulfone. . Other additives such as fillers, flame retardants, and flexibility imparters may be added as necessary. In the case of a thermosetting resin, sufficient curing treatment is performed in step (3).

After step (2), the conductive thin foil is peeled off and a process of applying solder resist, overlay film, etc. is started as a material for a single-sided flexible printed wiring board or a single-sided rigid printed wiring board. Separately, the material in step ① is used as a multilayer material, and the conductive TR foil is left as it is, and the guide hole is used to make 2 layers.
A two-layer circuit printed wiring board is obtained by bonding the sets back to back using an adhesive (FIG. 4). If this method is applied one after another, a multilayer wiring board can be obtained. It is also possible to provide wiring to the molded product itself by peeling off the thin foil of the product in step (2) and injection molding the product in close contact with the inner surface of the mold.

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

〔Example〕

Aluminum foil equivalent to JIS-84170 (
100 μm thick steel, surface roughness 2 μm) was used, and Hotesoku [F] (Hitachi Chemical Co., Ltd.) was used as a plating resist on the surface.
After thermocompression-bonding a dry film (manufactured by Dry Film), a reverse image of the circuit was printed and developed using a photomask method. Next, copper plating was performed using aluminum foil as a shade to form a circuit with a circuit width of 5 μm and a thickness of 25 μm. After that, the resist is removed by immersion in a stripping solution, and polyimide resin (Hitachi Chemical Co., Ltd.) is applied on top of it.
Vl-203) manufactured by Co., Ltd. was coated to a total thickness of 50 μm, and the wiring board (A) shown in FIG. 2 was obtained by heating and curing.

Next, the wiring board (A) is immersed in a dilute alkaline aqueous solution and the aluminum foil 1 is removed to obtain a wiring board as shown in FIG. 3(B). The copper circuit 2 was covered on three sides with an insulating layer 3, and its peeling force was about 1.5 kg/cm or more. Figure 3 (C) is
In addition, a solder resist 5 is applied to the circuit surface, making it sufficiently usable as a flexible wiring board.

Figure 4 (D>) is the two sheets shown in Figure 2 (A>) symmetrically pasted together with an adhesive. Examples of adhesives include polyimide-based Vl-205 manufactured by Hitachi Chemical Co., Ltd. can be used. When bonding, the upper and lower copper circuits can be aligned using the guide holes 4 provided on both sides of the aluminum foil 1 in (D) as a reference. Also, the upper and lower circuits can be connected through the through holes 7 using the usual method. It is possible to make it conductive by applying copper plating 8 to the surface, and by applying a solder resist, it is possible to create a flexible wiring board (E) with double-sided circuits.
is obtained. Figures 5 (F) and (G) are the 41st! l
In addition to (E), the addition of a layer was added to give a three-layer structure.

Figure 6 shows a phenolic resin laminate (LP-437F manufactured by Hitachi Chemical Co., Ltd.) with a thickness of 1.5 fins on the back side of the wiring board in Figure 3 (C).
) are pasted together to form a rigid circuit printed wiring board with a single-sided circuit.

〔Effect of the invention〕

As described above, the present invention is to manufacture a printed circuit board by forming a circuit on a conductive thin foil with a smooth surface by plating, and then forming an insulating layer on this. The wiring board is easy to manufacture, and since the insulating layer wraps around the conductor circuit on three sides, the circuit itself is held firmly, and the surface of the conductor circuit in the insulating layer is flush with the surface of the conductive thin foil, creating a smooth surface. Since a wiring board having the following properties can be obtained, multilayering is easy. Furthermore, since the conductive thin foil can be supplied as a continuous elongated body, continuous production is possible, and its industrial value is great.

[Brief explanation of drawings]

The drawings all show examples of the present invention; FIG. 1 is a process diagram, FIG. 2 is a cross-sectional view of a wiring board obtained from the process shown in FIG. 1, and FIG. 3 is a single-sided wiring board ( 4 is a sectional view of a double-sided wiring board (D) and a wiring board with through holes (E), and FIG. ) and a cross-sectional view of a wiring board provided with through holes, and FIG. 6 is a cross-sectional view of a beam-width wiring board. Explanation of symbols 1 Conductive thin foil 2 Circuit 3 Insulating layer 4 Guide hole solder resist through hole adhesive layer plated laminate (a) Figure (b) (c) Figure (d) (e) Figure (+) Figure Figure (CI)

Claims (4)

[Claims] 1. On a conductive thin foil with a smooth surface, a reverse image of a desired circuit is formed using a plating resist, and a conductive circuit is formed by electroplating or chemical plating, and then the plating resist is removed and the conductive circuit is covered. A method of manufacturing wiring boards that consists of embedding and fixing conductor circuits with a sufficient amount of synthetic resin. 2. 2. The method of manufacturing a wiring board according to claim 1, wherein the conductive thin foil is a metal foil or a plastic film formed with a conductive thin film having a thickness of 10 to 500 μm. 3. The method for manufacturing a wiring board according to claim 1, wherein the conductive thin foil has a surface roughness of 10 μm or less. 4. 2. The method of manufacturing a wiring board according to claim 1, wherein guide holes are bored on both sides of the conductive thin foil.