JPH0685467B2 - Method for manufacturing metal core printed wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a metal core printed wiring board, and more particularly to a method for manufacturing a metal core printed wiring board having through holes.

[Conventional technology]

As a printed wiring board, a copper clad laminate provided with an insulating layer made of an epoxy resin containing a glass cloth base material is generally used for industrial purposes. Printed wiring boards have become desired. In order to meet this demand, a metal core printed wiring board has been developed in which a metal such as aluminum, copper or iron is used as a core, an insulating layer is formed thereon, and a metal plating layer is further formed thereon. This kind of wiring board has dimensional stability,
It has excellent mechanical strength and bendability, is flame-retardant, can be used as a housing, and can be loaded with heavy parts. In recent years, a wiring board in which a large number of through holes (through holes) are provided at predetermined positions of a metal plate and a metal plating layer is also provided on the inner wall of the through hole by an additive method has also appeared. According to this, it is possible to form a circuit in which the front and back of the wiring board are connected through the through hole, and the through hole portion can be used as a component insertion port, which is suitable for high-density mounting.

As a method of manufacturing such a metal core printed wiring board, a metal plate with through holes is directly insulated by a fixed thickness by electrodeposition coating or powder coating using a water-based paint, and then a circuit is formed by an additive method. Forming method, or by heat-pressing a metal plate with through holes together with prepreg and copper foil, the resin contained in the prepreg is poured into the through holes of the metal plate to fill holes, and after heat curing it is formed on the metal plate. There is a method of using the resin contained in the prepreg for insulating the through hole by forming a through hole smaller than the original hole at the same position as the hole. In any case, how to form the insulation of the through hole is a key in manufacturing the metal core printed wiring board.

[Problems to be solved by the invention]

Among these methods, the method of applying insulation by electrodeposition coating or powder coating has been highlighted as an excellent method for uniformly insulating the inner wall of the through hole portion. (1) Electrodeposition coating and powder coating are the conventional methods. Since it is different from the stacking method by pressing, new equipment must be introduced.

(2) The coating materials for electrodeposition coating and powder coating are limited.

(3) It is necessary to perform additive plating to form a circuit.

As described above, there are drawbacks that it is difficult to put into practical use immediately because it involves steps different from the conventional printed wiring board manufacturing process.

Also, in the method of using the resin contained in the prepreg for the insulation of the through hole part, the resin that completely fills the through hole part of the metal plate must be supplied from the prepreg. In the prepreg used for, the resin content is about 50%, and the absolute amount of resin is insufficient to completely fill the through hole part, so air bubbles are mixed in the insulating layer of the formed through hole part, A highly reliable through-hole insulating layer cannot be obtained.

The present invention is to solve the above-mentioned problems of the prior art, and does not significantly change the conventional printed wiring board manufacturing process, does not contain air bubbles and has a highly reliable through-hole insulating layer containing a metal core. It is an object of the present invention to provide a method for manufacturing a metal-core printed wiring board capable of manufacturing the printed wiring board.

[Means for Solving Problems] The method for producing a metal-core printed wiring board according to the present invention includes a metal plate having a through hole, an inorganic filler, and a glass transition temperature of 35 ° C. or higher, 120 ° C. Melt viscosity at 5
B-stage resin is obtained by laminating a prepreg and a copper foil or a copper-clad laminate with a B-stage resin sheet in the range of 10 ³ to 10 ⁶ centipoise and hot pressing in a vacuum degassed state. In a through hole, extruding excess resin from the peripheral portion, and heating and curing the filled B-stage resin and prepreg to form an insulator, and the through hole in the obtained laminated plate. It includes a step of forming a smaller through hole at the same position, a step of plating the formed through hole portion, and a step of forming a circuit.

As the metal plate used here, aluminum, iron,
It may be copper, nickel, or an alloy thereof. The through holes of the metal plate can be formed by batch punching with an NC drill, press, etc., split punching with a uni-punch press, chemical milling, etc., and the drilling method is not limited. The edge portion of the through hole may be processed by deburring, trimming by sandblasting, etching, or the like. The number and size of through holes are not limited. Further, in order to prevent bubbles from being entrained when the B-stage resin flows into the through hole portion, the metal plate must have excellent surface smoothness, and the maximum surface roughness is preferably within ± 200 μm.

The B-stage resin sheet laminated on the metal plate is for filling through holes of the metal plate. Examples of the B stage resin include, but are not limited to, an epoxy resin, a phenyl resin, and a polyester resin.

In the present invention, the characteristics of the stage-shaped resin sheet used have a great influence on the characteristics of the final product, so that great care must be taken when manufacturing the resin sheet. The sheet must not contain air bubbles or foreign matters of a size (about 20 μm or more in diameter) that affects the electrical and mechanical properties of the final product, and the glass transition temperature of the B-stage resin sheet is 35 ° C. It is desirable to set it as above. If the glass transition temperature of the resin sheet is lower than 35 ℃, the working temperature (20 ~
At 25 ° C), stickiness and deformation occur and workability is significantly reduced. On the other hand, the extra resin not used for filling the holes in the metal plate is extruded to the outer periphery of the metal plate during hot pressing. Therefore, the melt viscosity of the resin sheet at this time must be sufficiently controlled. The melt viscosity is preferably in the range of 5 × 10 ³ to 10 ⁶ centipoise at 120 ° C., for example. If it is less than this viscosity, it will flow too much and air bubbles will be easily trapped in the through-hole portion. If it exceeds this viscosity, the flow will be insufficient and the resin will remain on the surface of the metal plate, increasing the thickness of the obtained laminate. .

Examples of the inorganic filler mixed in the resin sheet include alumina, fused silica, magnesium oxide, glass powder, glass chips, calcium carbonate, talc, spinel, kaolin, mica, zirconia, steatite, titanium white, and the like. May be used alone or in the form of a mixed powder of two or more kinds. Preferred inorganic fillers include glass chips alone or in combination with other inorganic fillers. By mixing such an inorganic filler in the resin, it is possible to reduce the volume shrinkage due to the curing of the resin and the change in the volume due to the temperature change of the cured product. Adhesion with a metal plate, crack resistance, and adhesion with through-hole plating are improved.

By setting the thickness of the resin sheet to be equal to or greater than the thickness of the metal plate, it is possible to prevent bubbles from being entrapped regardless of the number of through holes formed in the metal plate and the volume of the through holes.

As the prepreg to be laminated on the resin sheet, the same one as the conventional one, for example, glass cloth-containing epoxy resin prepreg can be used. Further, the same copper foil or copper clad laminate as the conventional one can be used.

In the manufacturing method of the present invention, a B-stage resin sheet containing an inorganic filler is first formed on a metal plate having through holes.
The prepreg and the copper foil or the copper clad laminate are laminated in the above order and hot pressed. The above-mentioned lamination may be performed on only one side, but it can be performed on both sides, and the metal plate, the resin sheet and the prepreg can be laminated in a plurality of layers via a multilayer inner layer plate.

The hot press is for filling B-stage resin into the through holes, extruding excess resin from the peripheral portion, and heating and curing the filled B-stage resin and prepreg to form an insulator. However, the means is not limited, but when the laminated product is pressed under vacuum with heating using a vacuum press die, even if a metal plate with poor surface smoothness is used, a resin that does not contain air bubbles Layers can be obtained.

Next, a through hole smaller than the original through hole is formed at the same position as the through hole of the metal plate on the laminated plate obtained as described above, and a circuit is formed after plating the through hole portion.

In order to improve the adhesion between the through-hole plating and the through-hole insulating layer (the layer formed by the above resin sheet), it is usual to perform acid etching treatment or plasma etching treatment on the wall surface of the through hole as a pretreatment for plating. Is desirable. In this case, when the fibrous substance is partially exposed from the wall surface of the through hole portion by the etching treatment, it exerts an anchoring effect on the through hole plating layer, and the adhesion between the plating layer and the insulating layer is significantly increased. For that purpose, a fibrous filler such as a glass chip (for example, Asahi Glass Co., Ltd., MF-A, MF-T-10) is used alone as an inorganic filler mixed in the resin sheet, or another inorganic filler is used. Good to use with.

[Action]

When the laminate is hot pressed, the B-stage resin is filled in the through holes of the metal plate, the B-stage resin and the prepreg are cured to form an insulating layer, and the entire laminate becomes a cured product. After that, a through hole smaller than the original through hole is formed in a portion where the B-stage resin is hardened, and a circuit is formed after plating to manufacture a metal core printed wiring board.

Since the B-stage resin sheet has a thickness equal to or larger than the thickness of the metal plate, the through holes are completely filled, air bubbles are not mixed, and a highly reliable through hole insulating layer is formed.

〔Example〕

A method of manufacturing a metal core printed wiring board according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration and process of an embodiment for manufacturing a double-sided printed wiring board. FIG. 1A shows a state before pressing, FIG. 1B shows a state after pressing, and FIG. 1C shows a state completed by through-hole plating. In the figure, (1) is a copper foil or a single-sided copper-clad laminate, (2)
Is a prepreg, (3) is a B-stage resin sheet,
(4) is a metal plate with through holes, (5) is a prepreg cured insulating layer, and (6) is a resin sheet cured insulating layer.

First, as shown in FIG. 1 (A), the manufacturing method is such that a resin sheet (3) is laminated on a metal plate (4) having through holes (4a), and prepregs (2) are laminated on both sides thereof, Further, a copper foil or a single-sided copper clad laminate (1) is laminated on both sides of these. Then, the material thus constructed is hot-pressed to obtain the cured laminated plate (7) of FIG. 1 (B).
Is obtained. After that, the metal plate (4) is attached to the laminated plate (7).
After forming a through hole (7a) smaller than the original hole at the same position as the through hole (4a), a plating layer (7b) is formed, and the same steps as those for manufacturing a general printed wiring board are performed. , A metal core double-sided wiring board (8) with through holes shown in FIG. 1 (C) is obtained.

FIG. 2 shows the construction of an embodiment of the present invention for manufacturing a multilayer printed wiring board. In the figure, (9) indicates a multilayer inner layer plate. The manufacturing method is such that a resin sheet (3) is laminated on a metal plate (4), and a laminate in which prepregs (2) are laminated on both sides of the resin sheet (3) is laminated via a multilayer inner layer plate (9). A copper foil or a single-sided copper clad laminate (1) is laminated on. Then, as in the case of FIG. 1, after hot pressing, through holes are formed and further plated to form a circuit to obtain a multilayer printed wiring board.

In addition, although the above-mentioned example explained the case of manufacturing a double-sided wiring board and a multilayer wiring board, the thickness of the metal plate used,
The number of sheets, the position, etc. are not particularly limited.

〔The invention's effect〕

According to the present invention, a prepreg and a copper foil or a copper clad laminate are laminated on a metal plate having a through hole via a specific B-stage resin sheet, and the through hole is formed by hot pressing in a vacuum degassed state. Since it is formed, the through holes of the metal plate are filled with the B-stage resin to fill the holes, and the excess resin is extruded, whereby air bubbles can be generated without greatly changing the conventional printed wiring board manufacturing process. It is possible to manufacture a metal core printed wiring board having a highly reliable through-hole insulating layer that does not mix.

[Brief description of drawings]

FIGS. 1 (A), (B), and (C) are sectional views showing respective steps of a method for manufacturing a metal core printed wiring board according to an embodiment of the present invention, and FIG. 2 is a step of another embodiment. FIG. In the drawings, the same reference numerals indicate the same or corresponding parts, and (1)
Is copper foil or single-sided copper clad laminate, (2) is prepreg,
(3) is a B-stage resin sheet, (4) is a metal plate,
(5) is a prepreg cured insulating layer, (6) is a resin sheet cured insulating layer, and (9) is a multilayer inner layer board.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-178595 (JP, A) JP-A-57-162498 (JP, A) JP-A-60-127782 (JP, A)

Claims (2)

[Claims] 1. A through-hole-formed metal plate containing an inorganic filler and having a glass transition temperature of 35 ° C. or higher and 120 ° C.
By laminating a prepreg and a copper foil or a copper clad laminate through a B-stage resin sheet having a melt viscosity in the range of 5 × 10 ³ to 10 ⁶ centipoise and hot pressing in a vacuum degassed state, A step of filling the B-stage-shaped resin into the through holes, extruding excess resin from the peripheral portion, and heat-curing the filled B-stage-shaped resin and prepreg to form an insulating material, and the obtained lamination. Manufacture of a metal-core printed wiring board, which comprises a step of forming through holes smaller than the through holes in the board at the same position, a step of plating the formed through hole portion, and a step of forming a circuit. Method. 2. The method for producing a metal-core printed wiring board according to claim 1, wherein the inorganic filler comprises glass chips alone or in combination with other inorganic fillers.