JPH0263141A - Manufacture of substrate for electronic component loading use - Google Patents

Abstract

PURPOSE:To enhance moistureproofness and a degree of freedom in a circuit design by a method wherein one part of a substrate, a bonding layer and a metal sheet is buckled from the surface side of the substrate, a recessed part for electronic-component loading use is formed and a contact exposed part is coated with a metal plated film. CONSTITUTION:A metal sheet 2 which is larger than a recessed part 15 for electronic- component loading use and is smaller than a substrate 1 is bonded, via a bonding Iayer 3 using a glass cloth impregnated with an unhardened epoxy resin, to the rear surface of the copper-plated substrate 1 where copper foil layers 4 have been formed on both faces. After that, a buckling operation is executed from the top surface of the substrate 1; a through hole 14 which has pierced the substrate 1 and the bonding Iayer 3 and where the top surface of the metal sheet 2 has been cut a little is mad. The top surface and the rear surface of the substrate 1 are coated with metal plated films 4. Since exposed parts are coated with the metal plated films 4, moisture does not creep, from the outside, into end faces of the substrate 1, the bonding layer 3 and the metal sheet 2 which form side faces of the recessed parts 15 for electronic-component loading use. In addition, since the whole rear of the substrate 1 is covered with the metal sheet 2 for radiation use, it is possible to install a conductor circuit on the surface other than a part where the metal sheet is bonded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a substrate for mounting electronic components, which has excellent moisture resistance and a high degree of freedom in designing a single circuit.

[Prior Art] Conventionally, electronic component mounting boards for mounting electronic components such as semiconductor elements directly onto printed wiring boards and electrically connecting the two by wire bonding have been used as interior boards for watches, cameras, etc. ing.

FIG. 4 shows an example in which electronic components are directly mounted on a printed wiring board, and the printed wiring board 90 is
A ceramic substrate or an organic resin substrate is used. In addition, the code|symbol 91 is a conductor circuit.

In FIG. 5, a recess 95 for mounting electronic components is provided on a printed wiring board 90 by counterbore processing or laminated molding, and a semiconductor element (the path shown in the figure) is mounted in the recess 95. Compared to the printed wiring board shown in FIG. 4, the printed wiring board shown in FIG. 5 has the advantage of being thinner as a whole when a semiconductor element is mounted thereon.

However, these conventional printed wiring boards do not provide sufficient heat dissipation for heat generated from mounted semiconductor elements.

Especially printed wiring boards made of organic resin.

Compared to metals, it has a lower thermal conductivity and is inferior in heat dissipation from semiconductor elements. On the other hand, ceramic substrates such as alumina are also insufficient for mounting recent highly integrated, high output electronic components.

Also, in Japanese Utility Model Application Publication No. 56-172970.

A reinforcing plate made of metal, ceramics, etc. is laminated with an adhesive layer on one side of the printed wiring board.

A printed wiring board for a watch is shown in which the board has a recess for mounting electronic components that reaches the reinforcing plate.

[Problem to be solved]

However, in the printed wiring board (hereinafter also referred to as a board) shown in the above publication, although the reinforcing plate is useful for the heat dissipation, moisture is allowed to reach the electronic components through the adhesive layer between the board and the reinforcing plate. There is a problem that the lifespan of electronic components is shortened because of the infiltration.

Moreover, the printed wiring board mentioned above is laminated with a reinforcing plate on the entire back surface of the board.

It is not possible to form a circuit on this back surface, which hinders the degree of freedom in designing the nine circuits.

Further, as mentioned above, printed wiring boards installed in watches, cameras, etc. are required to be as compact as possible, that is, to be mounted at high density.

In view of the above-mentioned conventional problems, the present invention has excellent flexibility in moisture-resistant three-circuit design, heat dissipation, and high-density packaging. The present invention aims to provide a method for manufacturing a board for mounting electronic components.

[Means for solving problems]

The present invention includes a step of bonding a metal plate for heat dissipation to the lower surface of a printed wiring board via an adhesive layer, and a layer of the printed wiring board, an adhesive layer, and a further layer above the metal plate. forming a recess for mounting an electronic component by counterboring a part of the substrate, and metal plating on the lower surface side of the second substrate and the exposed contact portion between the metal plate, the adhesive layer, and the substrate in the recess. The method of manufacturing a substrate for mounting electronic components comprises a step of coating a film, and the metal plate has a shape larger than the size of the through hole and smaller than the substrate.

In other words, the two-way method is to first bond a metal plate that is larger than the electronic component mounting recess and smaller than the board to the back side of the board for printed wiring, and then bond the board, adhesive layer, and metal plate together from the front side of the board. A recessed portion for mounting an electronic component is formed by counterboring the portion, and then the exposed contact portion is coated with a metal plating film.

In the present invention, before the plating film is formed, the recess for mounting the electronic component is formed by a hole provided in the substrate and a metal plate, as illustrated in FIG. 2C. The bottom surface of the recess is formed by a portion of the upper surface of the metal plate, and the side surfaces of the recess are formed by a portion of the metal plate, the adhesive layer, and the substrate. Further, on the lower surface side of the substrate, the substrate and the metal plate are bonded via an adhesive layer (FIG. 2C).

Therefore, in the present invention, the exposed contact portion refers to a portion where the adhesive layer between the metal plate and the substrate is exposed to the outside on the back side of the substrate and the inner surface of the recess, that is, the exposed contact portion. refers to exposed areas where moisture may enter from outside.

In the present invention, at least this contact exposed portion is coated with a metal plating film. It is also conceivable that such a metal plating film is particularly applied only to the exposed contact portion. Further, in many cases, the substrate has through-holes, and a step is taken to apply a metal plating film to the through-holes, so it is preferable to plate the exposed contact portions at the same time as through-ball plating.

Examples of such metal plating films include 2W4 plating, nickel plating, and gold plating.

In addition, since the metal plate is used for heat radiation,
It is sufficient to use a plate-shaped body that is slightly thicker than the recess for mounting electronic components, and it is similar to the reinforcing plate in the above-mentioned publication (it does not need to be provided on the entire surface of the board. Such metal plates include 9w4. copper alloy, iron, There are iron alloys, aluminum, aluminum alloys, etc.

Further, as the substrate, a glass fiber reinforced epoxy resin substrate, a polyimide resin substrate, a triazine resin substrate, etc. are used.

The adhesive layer may be an uncured epoxy resin-impregnated glass cloth 5, a heat-resistant adhesive sheet, or a liquid resin.

Thus, by the above manufacturing method, a printed wiring board and a through hole formed through the board.

It consists of a metal plate for heat dissipation that is attached to the lower side of the board via an adhesive layer so as to close the lower side of the through hole, and a recess formed by these for mounting electronic components. It has a shape larger than the size of the through hole and smaller than the substrate, and each exposed contact portion between the metal plate, the adhesive layer, and the substrate on the inner surface of the recess and the opposite side of the recess is covered with a metal plating film. A coated substrate for mounting electronic components is obtained.

(Operations and Effects) In the electronic component mounting substrate obtained by the manufacturing method of the present invention, the exposed contact portion is covered with a metal plating film (see FIG. 1).Therefore, the side surface of the electronic component mounting recess There is no possibility of warm air entering from the outside into the substrate, contact layer, and end face of the metal plate that form the
Since the electronic components are mounted above the recess and sealed with a sealing resin, moisture is prevented (see FIG. 3).

Furthermore, the contact exposed portion, which is the contact surface between the substrate, the adhesive layer, and the metal plate on the back side of the substrate, is also covered with a metal coating film. Therefore, there is no fear that moisture will infiltrate from the back side of the substrate through the adhesive layer.

Therefore, there is no possibility that moisture will infiltrate between the substrate and the metal plate, or even from the adhesive layer, into the electronic components mounted in the recesses in the substrate.

Further, the metal plate for heat dissipation is slightly larger than the recess for mounting electronic components, and does not cover the entire back surface of the board like the conventional reinforcing plate. Therefore, on the back side of the board,
A conductor circuit can be provided on the surface other than the part where the metal plate is attached. Therefore.

The electronic component mounting board of the present invention allows many conductor circuits to be formed on the front and back sides of the board, thereby increasing the degree of freedom in circuit formation.

In addition, the metal plate provided on the bottom of the recess for mounting electronic components is
Since it is located outside the bottom surface of the board, the heat of the electronic components can be efficiently dissipated to the outside. Further, since electronic components can be mounted in the recesses of the five substrates, high-density mounting can be promoted.

Therefore, according to the manufacturing method of the present invention, it is possible to easily manufacture an electronic component mounting board having excellent moisture resistance, three-circuit design freedom, etc. as described above.

〔Example〕

A method of manufacturing an electronic component mounting board according to an embodiment of the present invention will be explained using FIGS. 1 to 3.

First, as shown in FIG. 1, the electronic component mounting board obtained by the method of this example includes a board 1, which is a board for printed wiring, and a through hole provided through the board 1 from the top side to the bottom side. It consists of a hole 14 and a metal plate 2 for heat dissipation attached to the lower surface of the substrate 1 via an adhesive layer 3 so as to close the lower surface of the through hole 14 . A space surrounded by the through hole 14 and the metal plate 2 forms a recess 15 for mounting electronic components.

Further, on the inner surface of the recess 15, the contact exposed portion 32 between the two metal plates 2, the adhesive layer 3, and the substrate l is covered with a metal plating film 4.
covered by. The metal coating film 4 has a recess 15
It is provided all over the inside. On the other hand, on the lower surface side of the substrate l, 5
Contact exposed portion 31 between substrate 1, adhesive layer 3, and metal plate 2
is covered with a metal plating film 4. The metal plating film 4 is provided on the entire lower surface of the substrate 1. Further, a conductor circuit 110 is provided between the metal plating film 4 and the substrate 1.

Next, in manufacturing the electronic component mounting board, the steps shown in FIGS. 2A to 2E are used.

That is, first, as shown in FIG. 2A, a copper foil layer 11 is formed on one side.
A copper-clad substrate 1 provided with is prepared. Next, as shown in FIG. 2B, an electronic component mounting recess 15 is formed on the bottom surface of the substrate 1.
(Figure 2D) A metal plate 2 that is thicker than the substrate 1 and smaller than the substrate 1.
are bonded via an adhesive layer 3 made of glass cloth impregnated with uncured epoxy resin.

Thereafter, as shown in FIG. 2C, counterbore processing is performed from the upper surface of the substrate 1. Nine through holes 14 are provided through the adhesive layer 3 and by cutting the upper surface of the metal plate 2. Then, as shown in FIG. 2D, a metal plating film 4 is coated on the upper and lower surfaces of this substrate l. This metal plating film 4 is 9w4
This was done by plating. As shown in FIG. 2E, a conductive circuit 110 is formed on the substrate 1 through a normal process. In addition, we can print solder resist if necessary.
Enkel plated. Apply gold plating. In this way, the electronic component mounting board was manufactured.

Next, as shown in FIG. 3, on the electronic component mounting board, an electronic component 45 such as a semiconductor is mounted in the recess 15, and the electronic component 45 and the conductive circuit 110 are connected by a bonding wire 48. do. Then, the periphery of the electronic component 45 is sealed with an epoxy resin 47.

Since the electronic component mounting board of this example is configured as described above, the electronic component 45 is
There is no risk of moisture infiltrating.

Further, as described above, the metal plate 2 is slightly larger than the recess 15, and does not cover the entire back surface of the substrate as in the conventional technique, so that the degree of freedom in designing the nine circuits is improved.

Furthermore, the metal plate 2 improves the heat dissipation of the electronic component. Furthermore, since the electronic components 45 are mounted within the four parts 15, the overall thickness is reduced, contributing to high-density packaging.

Further, according to the above manufacturing method, the metal plate 2 of the above-mentioned size is adhered to the back surface of the substrate 1, and the metal plate 2 is counterbore-processed.

By forming a metal plating film, it is possible to easily manufacture an excellent electronic component mounting board as described above.

[Brief explanation of the drawing]

Figures 1 to 3 show the first embodiment, Figure 1 is a sectional view of a board for mounting electronic components, Figures 2A to 2E are explanatory diagrams showing the manufacturing process, and Figure 3 is an electronic component mounting board. 4 and 5 are explanatory diagrams of a conventional electronic component mounting board. Figure 1 1. 110. 14. 15. 2. 3°. 4. Board for printed wiring. , conductor circuit. Through hole. Recess for mounting electronic components. metal plate. Adhesive layer metal plating film.

Claims (1)

[Claims] A step of bonding a metal plate for heat dissipation to the lower surface of a printed wiring board via an adhesive layer, and a step of bonding the layer of the printed wiring board, the adhesive layer, and a part of the upper part of the metal plate from above the printed wiring board. a step of forming a recess for mounting an electronic component by counterboring, and a step of coating the exposed contact portion between the metal plate, the adhesive layer, and the substrate on the lower surface side of the substrate and in the recess with a metal plating film. A method of manufacturing a board for mounting an electronic component, wherein the metal plate has a shape larger than the size of the through hole and smaller than the board.