JPH0685464B2 - Manufacturing method of electronic component mounting board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electronic component mounting substrate that blocks infiltration of moisture into an electronic component such as a chip element or a semiconductor element and is excellent in heat dissipation. It relates to a manufacturing method.

[Prior art]

Conventionally, an electronic component such as a semiconductor element is directly mounted on a printed wiring board, and a board electrically connected by wire bonding is used as an inner layer board for a watch, a camera, or the like.

FIG. 5A is an example of an electronic component mounting board in the case where electronic components such as the semiconductor element 12 are directly mounted on the printed wiring board 1. A ceramic substrate or an organic resin substrate is used as the printed wiring board.

Further, as another structure of the printed wiring board, as shown in FIG. 5 (b), a recess is formed in the printed wiring board 1 in a mounting portion of an electronic component such as a semiconductor element by a counterbore processing or a lamination molding. There is also one in which an electronic component is mounted in the recess.

In FIGS. 5A and 5B, reference numeral 2 is a copper foil, 7 is a metal plating film, 13 is a bonding wire, and 14 is a sealing resin.

Among the materials for the printed wiring board, the organic resin material is excellent in that it is lightweight, easy to process, and inexpensive.

[Problems to be solved]

However, in these conventional printed wiring boards, sufficient heat dissipation from the heat generated from the mounted electronic components cannot be obtained. Therefore, it is applied only to electronic components with relatively low output, that is, electronic components that generate little heat. When mounting high-power electronic components, it is necessary to take measures such as providing fins for heat dissipation.

In particular, printed wiring boards using organic resin materials are
Compared to metals and the like, it has a low thermal conductivity and is inferior in heat dissipation from electronic parts. On the other hand, even ceramic substrates such as alumina are insufficient for mounting recent highly integrated and high-power electronic components.

In addition, a drawback of printed wiring boards using organic resin materials is that their moisture resistance is much lower than that of ceramics boards.
Therefore, as shown in FIG. 5 (b), in the case of a structure in which a concave portion is provided in the substrate and the electronic component is arranged in the concave portion, moisture from the outside may pass through the substrate and reach the electronic component. .

Such ingress of moisture corrodes electronic components. Therefore, it is difficult to use a printed wiring board made of an organic resin material in a field requiring high reliability in moisture resistance.

As a countermeasure against the above problems when using an organic resin material, the inventors previously applied for a patent for "a substrate for mounting electronic parts and a method for manufacturing the same" (Japanese Patent Application No. 59-15642).
6, JP 61-34990).

In the invention of this prior application, “(a) a first through hole is formed in an electronic component mounting portion of a first printed wiring board made of an organic resin material, and (b) A second printed wiring board having a second through hole larger than the first through hole is joined, and then (c) the second through hole is formed.
A heat-dissipating metal plate is joined to the back surface side of the first printed wiring board in the through hole to form a recess for mounting electronic components on the front surface side of the first printed wiring board, and then (d) the recess and heat dissipation are performed. A metal plating film is formed on the surface of the printed wiring board including the metal plate for use. "

According to this method, although an organic resin material is used, heat dissipation is improved and moisture resistance is also improved.

However, it cannot be said that the moisture resistance has been completely solved. That is, as described above, the moisture permeates the printed wiring board from all parts and into the recess for mounting the electronic component. Therefore, also in the above-mentioned prior invention, if the metal plating film is insufficient, moisture penetrates into the recess.

In the above-mentioned prior invention, the heat-dissipating metal plate is bonded to the back surface side of the first printed wiring board, but they are only bonded via the adhesive layer.

Further, the metal plating film is formed on the surface of the heat dissipation metal plate and the surface of the printed wiring board. However, since the printed wiring board is made of an organic resin material, it cannot be said that the adhesiveness with the metal plating film is sufficient, the plating is not completely formed, and it has fine pinholes. is there.

Further, a metal plating film is formed on the surface of the recess for mounting the electronic component with respect to the printed wiring board, but this metal plating film may have a pinhole.

If such pinholes are present, moisture may penetrate into the printed wiring board through the pinholes and damage electronic components.

Furthermore, as shown in FIG. 4 of the prior invention (see FIG. 3 of the present application), there is no sufficient space between the second through hole and the heat dissipation metal plate, and sometimes a corner portion or the like is present. In some cases, the side wall of the second through hole and the side wall of the heat-dissipating metal plate may have a side wall proximity portion in which they are close to each other.

Therefore, particularly in the portion near the side wall, the metal plating film forms a bridge, and a pinhole is likely to be formed. This is because there is a gap of, for example, 0.1 to 0.5 mm in the portion near the side wall, but the plating solution does not sufficiently enter the gap, resulting in poor plating and pinholes.

Therefore, in the above-mentioned prior invention, there is a possibility that moisture may penetrate into the inside of the printed wiring board from the metal plating film between the second through hole and the heat dissipation metal plate.

Further, in the above-mentioned prior invention, the heat radiation metal plate is directly bonded to the printed wiring board. Therefore, heat dissipation is not sufficient.

In view of the above-mentioned problems of the prior invention, the present invention completely applies a metal plating film between the heat radiating metal plate and the second through hole, particularly in the side wall proximity portion without generating pinholes. It is an object of the present invention to provide a method of manufacturing a substrate for mounting electronic components, which is capable of achieving excellent humidity resistance and heat dissipation.

[Means for solving problems]

The present invention includes: (a) a step of forming a first through hole 3 in a place where an electronic component is to be mounted on a first printed wiring board 1 made of an organic resin material; and (b) the first print. From the back side of the wiring board 1,
The second through hole 6 which is larger than the opening of the first through hole 3
A step of joining the second printed wiring board 4 made of an organic resin material having the above through the adhesive layer 5 so that the two through holes 3 and 6 correspond to each other, and (c) the first through hole 3 and the above. A step of forming a first metal plating film 7 on the surface of the substrate including both hole surfaces of the larger second through hole 6, and (d) the first printing inside the second through hole 6. The first through hole 3 is closed from the back surface side of the wiring board 1, and the concave portion 8 for mounting an electronic component is formed on the front surface side of the first printed wiring board 1 via the adhesive layer 5. A step of joining a heat-dissipating metal plate 9 on the first metal plating film 7, and (e) a surface of both printed wiring boards 1 and 4 including the recess 8 and a surface of the heat-dissipating metal plate 9. Manufacture of a board for mounting electronic parts, which comprises a step of forming a second metal plating film 10 There is the law.

What is most noticeable in the present invention is that the first and second printed wiring board surfaces including the hole surfaces of the first through hole and the second through hole are formed on the surface of the first and second through holes before joining the heat dissipation metal plate. Forming the metal plating film (step c), joining the heat-dissipating metal plates (step d), and then forming a second layer on the surfaces of the first and second printed wiring boards and the heat-dissipating metal plate including the recesses. The second step is to form a metal plating film (step e).

In the method of the present invention, as a method for forming the metal plating film on the printed wiring board made of an organic resin material, there is a known electroless copper plating method. For example, there is a known through-hole plating method in which when a through-hole is plated, the surface of the substrate or its recess is plated at the same time (Japanese Patent Laid-Open No. 59-67686).

Similarly, as a method for plating the surface of the substrate with a metal, there are known electroless plating methods (chemical plating methods) disclosed in Japanese Patent Application Laid-Open No. 50-145856 and Japanese Patent Publication No. 56-9024. ).

[Action and effect]

In the present invention, the first metal plating film is formed before joining the heat dissipation metal plate.

Therefore, the first through hole, the hole surface of the second through hole, the first,
A metal plating film is formed on the entire outer surface of the second printed wiring board. What is most noticeable here is that the metal plating film is formed before joining the heat-dissipating metal plates, so that all the above-mentioned surfaces remain in a large area, and good plating conditions can be obtained, resulting in poor plating. Is not to occur.

That is, in the prior invention shown in the conventional example, since the metal plating film is formed after the metal plate for heat radiation is joined to the second through hole, the side wall proximity portion between the both side walls of the metal plate for heat radiation and the through hole is formed. There is a risk of defective plating.

However, in the present invention, since there is no such portion near the side wall, the metal plating film is well formed and no pinhole is generated.

Further, as shown in the conventional example, the printed wiring board made of an organic resin material and the metal plating film cannot be said to have sufficient adhesiveness, and the metal plating film may have fine pinholes. However, in the present invention, the heat-dissipating metal plate is joined after the first metal plating film is formed, and then the second metal plating film is formed.

Therefore, even if some pinholes are formed in the first metal plating film, the pinholes are blocked by the second metal plating film and no pinhole remains.

Further, when the second metal plating film is formed, the side wall proximity portion is formed between the heat dissipation metal plate and the through hole. However, even if the metal plating film on the side wall proximity portion is defective in plating, a good first metal plating film has already been formed inside the side wall proximity portion, that is, on the back surface side of the first printed wiring board. Has been formed. Therefore, the infiltration of moisture from the side wall adjacent part is completely prevented.

As described above, the “first formation of the metal plating film (step c) before joining the heat-dissipating metal plate” in the present invention refers to the hole surface of the first and second through holes, the first and second through holes. A good metal plating film is formed on the surface of the second printed wiring board, and an excellent moisture resistance effect against plating failure in the portion near the side wall is exhibited.

Further, even if there are some pinholes in the first metal plating film, these are completely blocked by the second metal plating film, and no pinhole remains. Therefore, it has high humidity resistance.

In addition, since the heat dissipation metal plate is bonded onto the first metal plating film, the heat dissipation property is better than that in the case where the heat dissipation metal plate is directly bonded to the printed wiring board as in the conventional example. Are better.

Therefore, according to the present invention, the metal plating film between the heat radiating metal plate and the second through hole, particularly the portion near the side wall, can be completely applied without generating pinholes, and the moisture resistance and the heat resistance can be improved. It is possible to provide a method of manufacturing a substrate for mounting electronic components, which has excellent radiation performance.

〔Example〕

A method of manufacturing an electronic component mounting substrate according to an embodiment of the present invention will be described first with reference to FIGS.

In this example, first, as shown in FIG. 2A, a first printed wiring board 1 made of an organic resin material is prepared, and the first through hole 3 is formed by punching or the like.
To drill. This through hole 3 is for forming a recess 8 (see FIG. 2 (f)) for mounting an electronic component. The first printed wiring board 1 has a layer of copper foil 2 on the front surface.

Next, as shown in FIG. 2B, a second through hole 6 larger than the opening of the through hole 3 is provided from the back surface side of the first printed wiring board 1. The second printed wiring board 4 for the lower board is arranged so that both through holes 3 and 6 correspond to each other.
Bonding is performed via the adhesive layer 5.

The second printed wiring board 4 for the lower substrate is made of an organic resin material like the first printed wiring board 1 for the upper substrate. Further, the through hole 6 is also formed in the same manner.

Next, as shown in FIG. 2 (c), the first printed wiring boards 1 and 4 and the wall surfaces of the through holes 3 and 6 are bonded to each other.
The metal plating film 7 for the second time is formed. As a method of forming the metal plating film, there is a known electroless copper plating method as described above.

Next, as shown in FIG. 2 (d), the through hole 3 is closed from the back surface side of the printed wiring board 1,
The heat dissipation metal plate 9 is joined by the adhesive layer 5. As a result, the through hole 3 of the first printed wiring board 1 for the upper board is formed.
The heat-dissipating metal plate 9 forms the recess 8 for mounting electronic components.

Then, as shown in FIG. 2 (e), the second metal plating film 7 is formed on the surfaces of both the printed wiring boards 1 and 4 including the recess 8 in the same manner as the first metal plating film 7. A plating film 10 is formed. As shown in FIG. 2 (e), the metal plating film 10 is further formed on the surface of the heat radiating metal plate 9 and the inner wall surface of the through hole 6 continuous with the surface.

After that, as shown in FIG. 2 (f), the semiconductor element 12 is mounted in the recess 8 and the bonding wire 13 is connected,
It is sealed with the sealing resin 14.

The details of each step will be specifically described below.

FIG. 2 (a) shows the first through-hole 3 in the single-sided copper film printed wiring board 1 where the electronic component is to be mounted by punching, router processing or counterbore processing.
FIG. 6 is a vertical cross-sectional view in which

Typical examples of printed wiring boards are glass fiber reinforced epoxy resin boards, paper phenol resin boards, paper epoxy resin boards, glass polyimide resin boards, glass triazine resin boards, and the like. Then, a copper coating such as the copper foil 2 may be previously formed on the surfaces of these substrates.

Next, FIG. 2 (b) shows an organic resin material having a second through hole 6 larger than this so as to surround the through hole 3 from the back side of the first printed wiring board 1. FIG. 3 is a vertical cross-sectional view in which a second printed wiring board 4 made of is laminated and formed via an adhesive layer 5.

The adhesive layer 5 is an uncured epoxy resin-impregnated glass cloth, a heat-resistant adhesive sheet, a liquid resin, or the like, and an adhesive layer having various properties such as adhesiveness, heat resistance, and durability is preferable.

FIG. 2C shows at least the through hole 3 of the laminated substrate.
FIG. 3 is a vertical cross-sectional view in which a first metal plating film 7 is formed on the surface of the substrate including. A metal plating film 7 formed on the wall surface of the through hole 3 and the surfaces of both printed wiring boards 1 and 4.
Is to prevent the permeation of moisture and improve heat dissipation.

FIG. 2D is a vertical cross-sectional view showing a state in which the heat-dissipating metal plate 9 is attached via the adhesive layer 5 so that the concave portion 8 is formed from the back surface side of the printed wiring board 1. is there.

As the heat-dissipating metal plate 9, one having a relatively large thermal conductivity such as copper, copper-based alloy, iron, iron-based alloy, aluminum or aluminum-based alloy is used. The size and thickness of the metal plate are not particularly limited, but a thicker plate and a larger surface area is advantageous in improving heat dissipation.

As a method of determining the mounting position of the heat-dissipating metal plate, as shown in FIGS. 3A and 3B, the plane shape of the second through hole 6 of the second printed wiring board is set to Alternatively, a substrate in which at least two corner portions are deformed may be used. Alternatively, as shown in (c) and (d) of FIG. 3, at least two positions of the sides or corners of the heat-dissipating metal plate 9 in the plan view are deformed, and the position of the heat-dissipating metal plate is thereby changed. There is a way to decide.

In the deformed portion of the side or the corner, a side wall proximity portion having a particularly small gap is formed between the side wall of the heat radiating metal plate 9 and the side wall of the second through hole 6.

FIG. 2 (e) shows a printed wiring board in which the metal plating film 10 is formed on the surface of the concave portion 8, the heat radiation metal plate 9, and the first and second printed wiring boards 1 and 4. Substrate 1,
FIG. 4 is a vertical cross-sectional view showing a state in which the heat radiating metal plate 4 and the heat radiating plate 4 are integrated.

The metal plating film 10 has an effect of blocking water from entering the adhesive layer 5 between the printed wiring board 1 and the heat radiating metal plate 9 and preventing water from entering the electronic component mounting portion. Further, since the metal plate 9 for heat radiation and the copper foil 2 on the surface of the printed wiring board are integrated by the metal plating coatings 7 and 10, heat generated from the electronic components is quickly transferred from the metal plate for heat radiation to the copper foil. Since it is conducted to the outside and dissipated to the outside, there is an advantage that the heat dissipation effect is improved.

FIG. 2F is a vertical cross-sectional view showing a state in which the semiconductor element 12 is mounted on the electronic component mounting substrate according to the present invention and connected by wire bonding, and the semiconductor element and its peripheral portion are sealed with the sealing resin 14. It is a figure. Examples of the sealing resin include epoxy resin and silicone resin. Further, reference numeral 15 is a dam frame for preventing the outflow of the sealing resin.

The electronic component mounting board of the present invention manufactured in this manner has the characteristics shown in the vertical sectional view of FIG. The feature is that the surface of the single-sided copper coating printed wiring board 1 made of an organic resin material has a concave portion 8 in which a conductor circuit and electronic parts are to be mounted, and the concave portion 8 is located on the rear surface side of the substrate for heat dissipation. Board 9
A second metal plated coating 10 in contact therewith.

On the back surface side of the first printed wiring board 1, a printed wiring board 4 having through holes 6 formed in advance is laminated. Further, after forming the first metal plating film 7, a heat radiating metal plate 9 is attached so as to close the through hole 3 from the back surface side of the printed wiring board 1.

Therefore, the metal plating film 7 exists between the first printed wiring board 1 and the heat dissipation metal plate 9. Therefore, it is possible to completely prevent the infiltration of moisture from this part.

FIG. 4 is a perspective view of the plug-in package substrate of the present invention. In this structure, a large number of conductor pins 18 are arranged in a row in a through hole 16 provided in the outer peripheral portion of the electronic component mounting board. As shown by the shaded area, a thermosetting resin sheet 17 is adhered on the outer peripheral portion of the substrate and the through holes 16. This is to completely cover the through hole.

As known from the above embodiment, in this embodiment, the first metal plating film 7 is formed before joining the heat dissipation metal plate 9. Therefore, the first through hole 3, the hole surface of the second through hole 6, and the first and second printed wiring boards 1,
The metal plating film 7 is formed on the entire outer surface of 4.

What should be noted here is that the metal plating film 7 is formed before joining the heat dissipation metal plate 9, so that the plating surface is wide and a good plating state can be obtained. That is, at the time of forming the first metal plating film 7, there is no narrow side wall proximity portion between the heat dissipation metal plate 9 and the through hole 6. Therefore, plating failure does not occur.

In addition, after joining the metal plate 9 for heat dissipation, the second metal plating film 10 is formed again. Therefore, even if some pinholes are formed in the first metal plating film 7, they are completely blocked by the metal plating film 10 and no pinhole remains.

Further, although the side wall proximity portion is formed after the heat dissipation metal plate 9 is joined, even if the second metal plating film 10 causes a plating failure in the side wall proximity portion, that is, inside the side wall proximity portion, that is, The first favorable metal plating film 7 of the first time is already formed on the back surface side of the printed wiring board 1.

Therefore, it is possible to completely prevent the infiltration of moisture from the portion near the side wall. Further, since the heat-dissipating metal plate is bonded onto the first metal plating film 7, the heat dissipation property is also excellent.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an electronic component mounting substrate of an embodiment according to the present invention, FIG. 2 is a vertical sectional view of the substrate showing a flow sheet of a method for manufacturing an electronic component mounting substrate, and FIG. 2 is a plan view showing a state of alignment when a heat-dissipating metal plate is attached to the second through hole of the printed wiring board 2; FIG. 4 is a perspective view of the plug-in package board of the present invention; 3 is a vertical cross-sectional view of the electronic component mounting board of FIG. 1,4 ...... Printed wiring board, 2 ...... Copper foil, 3,6 ...... Through hole, 5 ...... Adhesive layer, 7 ...... First metal plating film, 8 ...... Recess (for mounting electronic parts Recessed part), 9 ... Heat dissipation metal plate, 10 ... Second metal plating film, 11 ... Solder resist mask, 12 ... Semiconductor element, 13 ... Bonding wire, 14 ... Sealing resin, 15 ... … Resin encapsulation frame, 16… Through hole, 17… Thermosetting resin sheet, 18… Conductor pin,

Claims (1)

[Claims] 1. A step of (a) forming a first through hole 3 at a location where an electronic component is to be mounted on a first printed wiring board 1 made of an organic resin material, and (b) the above first step. From the back side of the printed wiring board 1,
The second through hole 6 which is larger than the opening of the first through hole 3
A step of joining the second printed wiring board 4 made of an organic resin material having the above through the adhesive layer 5 so that the two through holes 3 and 6 correspond to each other, and (c) the first through hole 3 and the above. A step of forming a first metal plating film 7 on the surface of the substrate including both hole surfaces of the larger second through hole 6, and (d) the first printing inside the second through hole 6. The first through hole 3 is closed from the back surface side of the wiring board 1, and the concave portion 8 for mounting an electronic component is formed on the front surface side of the first printed wiring board 1 via the adhesive layer 5. A step of joining a heat-dissipating metal plate 9 on the first metal plating film 7, and (e) a surface of both printed wiring boards 1 and 4 including the recess 8 and a surface of the heat-dissipating metal plate 9. Manufacture of a board for mounting electronic parts, which comprises a step of forming a second metal plating film 10 Law.