JPS63280496A - Manufacture for multilayer circuit board - Google Patents

Abstract

PURPOSE:To suppress side etching to a minimum limit while to form a fine circuit with high accuracy and high density, by forming a mask member of predetermined pattern on the exposed surface of metal conductor foil and an electroplating layer on the surface of the metal conductor foil so that a conductor layer of various thicknesses is easily formed. CONSTITUTION:A both-side metal conductor foil coated plate 3, after the perforation of a hole, activates the exposed surface by a Pd catalyst thereafter applies copper plating, forming an electroless-plated layer 5 on surfaces of metal conductor foils 2a, 2b containing inside a through hole 4 and a mask member 6, consisting of plating resist, in a predetermined region on both sides of the electroless-plated layer 5. Next, a thick thickness conductor part 13, comprising an electroplated layer 7, electroless-plated layer 5 and the metal conductor foil 2a, forms a circuit for large current use and a heat radiating part, and after removing the mask member 6, a thin thickness conductor part 11, comprising the electroless-plated layer 5 and the metal conductor foil 2a, forms a thin thickness circuit 8 in the predetermined part under a condition that the thick thickness conductor part 13 is protected. A both-size two-layered circuit board 15, thus obtained as described becomes the title circuit board independently.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of manufacturing a multilayer circuit board.

[Conventional technology and its problems]

In the conventional manufacturing method of multilayer circuit boards, when forming a metal plating layer in the through hole, the entire exposed surface including the conductor layer formed on the surface of the board is plated, so the conductor layer part is plated. It becomes thicker than necessary. Therefore, when etching is performed to form a predetermined circuit pattern on the conductor layer, the etching time becomes long and so-called side etching becomes large.

To solve this problem, there is a technique to use copper foil with a thickness of 9 μm, 12 μm, etc. when forming fine circuits, but the material cost is extremely high and it is difficult to use such thin copper foil. Handling is difficult. For this reason, special equipment for handling thin copper foil is also required, which poses a problem of increasing manufacturing costs.

On the other hand, even among minute circuits, where a large current capacity is required, such as in parts constituting power circuits, the thickness of one circuit must be increased. It is also necessary to increase the wall thickness in parts of the circuit that require high heat dissipation. For this reason.

In the manufacturing method of multilayer circuit boards, it has been desired to easily form fine circuits made of thick and thin conductor layers with high precision and high density.

The present invention has been made in view of these points, and is capable of easily forming thick and thin conductor layers, minimizing side etching, and forming predetermined fine circuits with high precision and high density. The present invention provides a method for manufacturing a multilayer circuit board.

[Means for solving problems]

The present invention includes a process of forming desired holes in a double-sided metal conductor foil clad plate obtained by pasting metal conductor foil on both sides of an insulating resin body, and a process of forming desired holes in a double-sided metal conductor foil clad plate obtained by pasting metal conductor foil on both sides of an insulating resin body. After forming an electroless plating layer on the entire exposed surface of the plate including the inside of the hole, a mask member having a desired pattern is formed on the exposed surface excluding at least the inside of the hole, or a mask member with a desired pattern is formed on the exposed surface excluding at least the inside of the hole. after forming a patterned mask member, forming an electroless plating layer on the entire exposed surface including inside the holes; forming an electroplating layer on the exposed surface of the electroless plating layer; and forming an electroplated layer on the exposed surface of the electroless plating layer; and forming a circuit in a desired portion of the mask member removal surface and the air plating layer forming surface.

In the present invention, the insulating resin body may be a rigid body such as an epoxy-impregnated glass cloth laminate or a polyimide-impregnated glass cloth laminate, or a flexible plastic foil body such as polyimide, polyester, or epoxy-impregnated glass cloth having a thickness of 25 to 150 μm. used. In addition, as a metal foil, copper foil has electrical conductivity, mechanical strength, chemical properties,
It is optimal in terms of economic efficiency, etc.

Hereinafter, one method of the present invention will be explained with reference to the drawings.

As shown in FIG. 1, an insulating resin body 1 is prepared, and metal conductor foils 2* and 2b made of copper foil or the like are adhered to both sides of the body to form a double-sided metal conductor foil-clad board 3. here.

The thickness of the metal conductor foil 21 is 1, for example, 35μ.
m, 18 μm is used.

Further, the metal conductor foils 2m and 2b are attached by using, for example, an adhesive, or by direct thermocompression bonding.

Next, as shown in FIG. 2, a predetermined area of the double-sided metal conductor foil clad plate 30 is drilled or punched to form a through hole 4.

Next, as shown in FIG. 3, the exposed surface of the double-sided metal conductor foil clad plate 3 after drilling is activated with a Pd catalyst, and then copper plating is applied, and the metal conductor foil la, lb including the inside of the through hole 4 is coated with copper. An electroless plating layer 5 is formed on the surface. Electroless plating layer 5
It is preferable to use a thin material with a thickness of 5 μm or less.

Next, as shown in FIG. 4, mask members 6 made of plating resist are formed in predetermined areas of the electroless plating layer 5 on the front and back surfaces. Here, the electroless plating layer 5 and the fourth layer shown in FIG.
The procedure for forming the mask member 6 shown in the figure is 1. Contrary to what is shown in the figure, first, a mask member 6 made of, for example, photo-V cyst is formed on the exposed surface excluding the through holes 4, and then the entire area including the through holes 4 is exposed. An electroless plating layer 5 may be formed on the surface.

Next, as shown in FIG. 5, an electroplated layer 1 of, for example, copper is formed on the exposed surface of the electroless plating layer 5 including the inside of the through hole 4 using the mask member 6 as a mask.

Next, as shown in FIG. A circuit and a heat dissipation section for large percentage use are formed in the thick conductor section 13 made of the electroless plating layer 5 and the metal conductor foil 2a.

Next, as shown in FIG. 7, after removing the mask member 6t, the thin conductor portion 13 made of the electroless plated layer 5 and the metal conductor foil 2a is etched while the thick conductor portion 13 is protected from being etched. A thin circuit 8 is formed in a predetermined portion of the conductor portion 11. Here, the process for forming the circuit on the thick conductor part 13 and forming the thin circuit 8 on the thin conductor part 11 may be performed in a state where the previously formed circuit is protected and the procedure is reversed to that shown in the drawings.

The thus obtained double-sided two-layer circuit @15 may be used alone as a multilayer circuit board, or in the case of forming a multilayer circuit board with three or more layer circuits, a desired portion of the double-sided two-layer circuit board are laminated via prepreg as part or all of a multilayer circuit board to form a multilayer circuit board.

When particularly high heat dissipation is required, as shown in FIG. The metal substrate 10 may be made of, for example, a Cu plate, an A plate, or an Fe plate, or may be made of one of these plates subjected to insulation treatment. Further, no circuit is formed on the conductor surface of the top layer of the finally obtained multilayer circuit board, and after this is pasted on the metal substrate 10, a predetermined circuit is formed to form the metal base multilayer circuit board 16. good.

[Effect]

According to the method for manufacturing a multilayer circuit board according to the present invention, a mask member having a predetermined pattern is formed on the exposed surface of a metal conductor foil, and the electroplated layer is applied to the surface of the metal foil conductor using this mask member as a mask. Form.

Therefore, a thin conductor portion made of metal conductor foil and a thick conductor portion made of metal conductor foil and an electroplated layer can be selectively and easily formed on the substrate. As a result, side etching during circuit formation can be minimized, and a thin circuit can be easily formed on a thin conductor portion. Thick circuits such as power circuits and heat sinks can be easily formed on thick conductor parts.

〔Example〕

Examples of the present invention will be described below.

Electrolytic Cu foil with a thickness of 35 μm was adhered to both sides of a foil body made of polyimide with a thickness of 25 μm to obtain a double-sided steel foil-clad plate.

Various through-holes with diameters of 0.5 to 2 degrees were made in this double-sided steel foil-clad plate by patching. Next, this was degreased and pickled, and then immersed in a 1% PdC() aqueous solution.

This was immersed in a chemical plating bath of Cu406 (Meltex Co., Ltd., trade name) for 20 minutes at a temperature of 35°C to form an electroless copper plating layer with a thickness of 0.5 μm on the entire surface including the through holes. did. Next, after applying masking tape to a part of the double-sided copper foil clad plate after electroless copper plating,
0g/no, Top Lucina (Okuno Pharmaceutical Co., Ltd., trade name) 5pp
The sample was immersed in a CuSO4 bath (30°0.5 A/dm") of 18 μm in thickness, and a Cu layer with a thickness of 18 μm was electroplated on the entire surface.

Next, leaving the masking tape as it is, apply a photosensitive dry film (DFR, Asahi Kasei Co., Ltd.) to the electroplated surfaces of both sides of the double-sided steel foil clad plate on which the electroplating layer has been formed.

(trade name) was crimped, exposed and developed, and then etched with a FeCJ solution to form a thick conductor circuit pattern on the thick conductor portion consisting of the Cu foil layer and the plating layer. Next, the remaining dry film was peeled off, and the masking tape was also peeled off.

Next, a thick conductor circuit pattern was formed on the thin conductor portion made of the Cu foil and the electroless plating layer on the surface from which the masking tape was removed in the same manner as in the case of the thick conductor circuit. Thereafter, solder resist (HR16, Taiyo Ink Co., Ltd., trade name) and 7lux were applied except for the pad portions to obtain a multilayer circuit board.

In the multilayer circuit board of the example thus obtained.

It was possible to form a circuit pattern with a width of Q, 1 Ote with good reproducibility using a thin conductor portion formed by masking in advance. On the other hand, in the conventional method without a masking step, the difference is 0.25 to 0.
The limit was to form a circuit pattern with a width of 30 words.

Further, in the multilayer circuit board of the example, no disconnection accident was observed in the initial stage, and when some of the circuits were cut and examined under a microscope, no cracks were observed at all. Furthermore.

Alternate immersion using 250°C oil and cold water was repeated 50 times, but the change in electrical resistance was within 5 degrees of the initial value.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a multilayer circuit board according to the present invention, thick and thin conductor layers can be easily formed, side etching when forming two circuits can be minimized, and
Predetermined fine circuits can be formed with high precision and high density.

[Brief explanation of drawings]

FIGS. 1 to 7 are explanatory diagrams showing the method of the present invention in the order of steps. FIG. 8 is a cross-sectional view of a metal-based multilayer circuit board obtained using the method of the present invention. 1...Plastic foil body, 2*, 2b...Metal conductor foil, 3...Double-sided metal conductor foil coating, 4...Through hole. 5... Electroless plating layer, 6... Mask member, 1...
・Electroplated layer, 8... Thin circuit, 9... Insulating layer,
10... Metal substrate, 1... Thin conductor part, 13.
・Thick conductor part, 15 ・Double-sided double-layer circuit board, 16・
...Metal paste multilayer circuit board. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] A step of drilling a desired hole in a double-sided metal conductor foil-clad plate obtained by pasting metal conductor foil on both sides of an insulating resin body, and forming holes in the double-sided metal conductor foil-clad plate that has been subjected to the perforation process. After forming an electroless plating layer on the entire exposed surface including the pores, a mask member having a desired pattern is formed on the exposed surface excluding at least the inside of the hole, or a mask member having a desired pattern on the exposed surface excluding at least the inside of the hole. forming an electroless plating layer on all exposed surfaces including inside the holes; forming an electroplating layer on the surface of the electroless plating layer; and removing the mask member. and forming a circuit on a desired portion of the mask member removal surface and the electroplating layer formation surface.