JPH0332100A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To improve the heat dissipating property by arranging a heat conductive plate member on the outermost layer surface and subjecting the portion of said plate member where a conductor part is to be formed to a clearance treatment. CONSTITUTION:A ceramic plate member 6 is buried in the outermost layer surface. This plate member 6 is made of the ceramic having a good heat dissipating property and a good heat conductivity. In this plate member 6, the portion where a conductor part is to be formed, for example, where a through-hole 5 penetrates, is subjected to a clearance treatment. By thus arranging the plate member 6, if the mounted electronic part emits heat, the heat can be dispersed to the whole wiring board, so that concentration of the heat can be prevented. Accordingly, the whole wiring board works as a heat dissipating area and a heat dissipating efficiency is improved. As a thermal expansion coefficient of the plate member 6 is small, a warpage caused by thermal expansion does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer printed wiring board with good heat dissipation.

[Conventional technology]

Conventionally, a multilayer printed wiring board has a structure in which a plurality of layers of conductive circuits are laminated with insulating layers interposed therebetween, as shown in FIG. In FIG. 3, 1 is the surface of the outermost layer forming the conductive circuit, 2 is the conductor circuit surface immediately inside thereof, and 3 is the conductor circuit surface inside thereof. These outermost layer surfaces and conductor circuit surfaces are laminated with a prepreg 4, which is an insulating layer, interposed therebetween. 5 is a through hole communicating from the top surface to the bottom surface.

This through hole 5 is a hole for attaching components or forming an electric circuit between the conductor circuit surfaces. The prepreg 4 is made of glass cloth as a base material, which is impregnated with epoxy resin, polyimide resin, modified polyimide resin, or the like.

However, such an insulating layer made of prepreg 4 is inferior in terms of heat dissipation, and for this reason, failures due to heat generation or heat accumulation may occur when heat-generating components are mounted on the outermost layer surface 1 or when high-density mounting is performed. There were drawbacks such as the occurrence of In addition, there is a problem in that there is a limit to the number of heat-generating components that can be mounted to prevent this failure. Therefore, in order to promote heat dissipation, heat dissipation fins are provided on top of the heat generating components mounted, or heat dissipation fins are provided at the end of the outermost layer surface 1, but in this case, the heat dissipation fins themselves become too tall. Therefore, there are problems such as there being a limit to the miniaturization of the electronic device that can be obtained and the mounting density of the card assembly not being able to be increased.

[Problem to be solved by the invention]

The present invention was made in order to eliminate the above-mentioned drawbacks and problems, and an object of the present invention is to provide a multilayer printed wiring board with good heat dissipation. This multilayer printed wiring board can be particularly suitably used in electronic equipment using high-speed, high-density integrated circuit elements, such as high-speed computers and LSI testers.

[Means to solve the problem]

The gist of the present invention is to provide a multilayer printed wiring board in which a thermally conductive ceramic plate-like body is disposed on the surface of the outermost layer, with a clearance processed at a location where a conductor portion is to be provided.

This means will be explained in detail below.

Note that the same parts and parts as in FIG. 3 are represented by the same numbers.

FIG. 1 and FIG. 2 are respectively cross-sectional explanatory views of an example of the multilayer printed wiring board of the present invention. In FIG. 1, a ceramic plate-like body 6 is embedded in the outermost layer surface 1. As shown in FIG. In FIG. 2, the ceramic plate-like body 6 is arranged in a protruding state on the outermost layer surface 1. The ceramic plate-like body 6 is clearance-processed so that it does not come into contact with the through-hole 5, which is a conductor portion. 7 is copper placed around the through hole 5.

The ceramic plate-like body 6 may be disposed on either the outermost layer surface 1 on the upper surface or the outermost layer surface 1 on the lower surface, or may be placed on both the outermost layer surface 1 on the upper surface and the outermost layer surface 1 on the lower surface. .

The ceramic plate 6 is made of ceramic with good heat dissipation and thermal conductivity, and is made of ceramic such as aluminum straw, aluminum titanide, boron tinide, etc. in the form of a plate or sheet. or ceramic fibers made into cloth. To make it into a plate or sheet, for example,
This may be achieved by solidifying a powdered version of these ceramics with a small amount of a binder. Further, it may be made into a cloth form together with other ceramic short fibers. Ceramic plate-shaped body 6
There is no particular limit to the thickness of the
It is appropriate that the thickness is from m to 5.0 μm, preferably from 50 μm to 211 II. This ceramic plate-like body 6 includes
Clearance processing is applied to the portion where the conductor portion is to be provided, for example, the portion where the through hole 5 passes through as described above. That is, a hole with a diameter slightly larger than the hole diameter of the through-hole 5 is made at an appropriate location in the ceramic plate-like body 6.

By arranging the ceramic plate-like body 6 in this way, even if the mounted electronic components generate heat, the heat can be dispersed throughout the wiring board, thereby avoiding the concentration of heat. Since it becomes a heat dissipation area, the heat dissipation effect is improved.

In addition, in order to further enhance the heat dissipation effect, if there is a gap between the mounted electronic components and the surface of the wiring board, a material with heat dissipation properties may be placed between them as shown in Figure 4. The void may be eliminated. In FIG. 4, between the electronic component 8, which is a flat type IC, and the outermost layer surface 1, and
Between the electronic component 9, which is an IP type IC, and the outermost layer surface 1,
A heat dissipating material 10 is arranged in each case. Thereby, the heat generated by the electronic component can be dissipated to the wiring board through the heat dissipation material 10, and further to the ceramic plate-like body 6, and the heat dissipation effect can be further enhanced. This heat dissipation material 10 has a thermal conductivity of 0.5 x 1O-3
cal/cm HSec H'c group or higher is preferable, and for example, ceramic powder such as alumina or aluminum ξnium tinide, mica, etc. is blended with an organic material. Examples of the organic material include epoxy resin, acrylic resin, polyimide resin, modified polyimide resin, and silicone resin.

As shown in FIG. 5, electronic components may be placed on the ceramic root-like body 6;
If there is a gap between the two, the above-mentioned heat dissipating material may be placed in between to eliminate the gap. In FIG. 5, an electronic component 8, which is a flat IC, is placed on a ceramic plate 6. The ceramic plate-like body 6
An electronic component 9, which is a DIP type IC, is placed on top of the electronic component 9. A heat dissipating material 10 is placed in the gap between the electronic component 9 and the ceramic plate 6. In addition, in both FIG. 4 and FIG. 5, the heat dissipating material 10 may be placed by screen printing, a dispenser, or the like.

Further, it is preferable to leave a portion of the outermost layer surface 1 where no circuit is formed at a suitable location (either the end portion or the central portion) as a heat dissipation promotion area. As a result, the heat dissipated in the ceramic plate-like body 6 can be guided to this heat dissipation promotion area and dissipated to the outside.
It is possible to further enhance the heat dissipation effect.

Next, an example of the manufacturing procedure of the multilayer printed wiring board of the present invention will be specifically explained.

■ Preparation of inner layer material.

The inner layer material may be manufactured by a normal multilayer board manufacturing method. For example, a double-sided copper-clad laminate is leveled, a photosensitive photoresist is laminated on that surface, circuits are formed on both sides through processes such as exposure, development, etching, and photoresist peeling, and if necessary, a black layer is applied. Copper oxide treatment and drying. One of the laminates with circuits formed on both sides in this way is the inner layer material, or multiple laminates are interposed through a prepreg made of glass cloth impregnated with epoxy resin, polyimide resin, modified polyimide resin, etc. The layered material is the inner layer material.

■ Preparation of outer layer material.

Clearance processing is performed at the location where the conductor part of the ceramic plate (for example, aluminum plate) is to be installed.In other words, if the conductor part is a through hole, the diameter is slightly larger than the hole diameter of the through hole. Drill a hole in the ceramic plate. This hole may be made by drilling or laser processing.

Copper foil is attached to one side of this ceramic plate-like body with an adhesive or as it is.

The copper foils may be laminated using a real roll laminator or a hot press as appropriate. In this way, the outer layer material is obtained.

■ Lamination of inner layer material and outer layer material.

As shown in FIG. 6, the outer layer material is superimposed on the inner layer material via the prepreg 4, with the ceramic plate 6 on the inside and the copper foil 11 on the outside. Next, by heat-pressing, a multilayer board with copper foil 11 bonded to both sides is obtained.

When the depth of the hole 12 formed by clearance machining of the ceramic plate-like body 6 is deep, that is, when the thickness of the ceramic plate-like body 6 is thick, the outer layer material and the inner layer material are overlapped via the prepreg 4. If they are laminated together, air may accumulate in the holes 12 due to insufficient flow of resin, etc. into the holes 12. If vacuum forming is performed using a vacuum press or an autoclave in order to prevent this air pooling, dents will occur in the surface of the copper foil 11 corresponding to the holes 12. These defects do not pose a problem when the ceramic plate-like body 6 is thin, but become apparent when the thickness of the ceramic plate-like body 6 exceeds 0.2 mm. As a countermeasure against this, for example, a resin compound suitable for the volume of the hole 12 may be injected into the hole 12 prior to overlapping the outer layer material and the inner layer. As the resin compound, one having the same composition as the resin composition used for the prepreg 4 may be used.

As a method for injecting the resin compound into the hole 12, for example, a recently commercially available dispenser that can inject trace amounts of components with high precision may be used. The formulation may be embedded with a squeegee to smooth the surface.

■ Processing after lamination.

From the upper surface to the lower surface of the multilayer plate thus obtained, the seventh
As shown in Figure (A), the through hole 5 is passed through, and the inside of the through hole 5 is subjected to a pretreatment for chemical copper plating. Next, the inside of the through hole 5 is chemically copper plated to deposit copper, and as shown in FIG. 7(B), panel plating (electrolytic copper plating) is performed thereon to deposit an electric fI 22. Next, a photoresist is provided on the electrolytic copper 22 and the circuit is imaged (baked), as shown in FIG. 7(C).
As shown in FIG. 3, pattern plating (1! plating=copper plating and solder plating) is performed to adhere the cavities/solder 23, and the photoresist is peeled off and etching is performed. 7th
After soldering as shown in FIG. 7(D), the residue on the surface of the outermost layer is removed with chemicals to expose the surface of the ceramic plate 6, and the solder resist is removed as shown in FIG. 7(E). The area where the heat-generating component is mounted may be printed clear or may not be printed), and the solder 24 (solder leveler) is provided thereon. In this way, a multilayer printed wiring board can be obtained.

Moreover, the multilayer printed wiring board of the present invention can also be produced by other methods. That is, as shown in FIG. 8(A), after producing a conventional multilayer printed wiring board 30 as an inner layer material by a conventional method, as shown in FIG.
) As shown in FIG. 8 (C
) A multilayer board as shown is obtained.

Next, this multilayer plate is treated in the same manner as in FIGS. 7A to 7E, so that the ceramic plate 6 is formed on the surface of the outermost layer as shown in FIG. 8D. A multilayer printed wiring board with a protruding state can be obtained.

FIG. 9 shows an example of a completed product of the multilayer printed wiring board of the present invention. In FIG. 9, a ceramic plate-shaped body whose conductor portions such as through holes 5 are cleared is exposed on the surface.

Examples and comparative examples are shown below.

Example 1 An alumina plate having a predetermined through hole (diameter 2φ) and an 18 μΦ copper foil were laminated on the inner layer material with circuits already formed on both sides via prepreg (thickness 100 μ, 2 sheets), and Heat press at 170℃ for 2 hours, 40 kg
The prepreg is cured by heating and pressing at a pressure of /c+d,
A multilayer board with copper foil pasted on both sides was obtained (FIG. 6). Next, the surface of the multilayer board was etched to form a circuit using the method used to produce a normal multilayer printed wiring board. in this case,
On the surface where the copper foil was removed, there was a small amount of adhesive that had soaked in between the W4 foil and the aluminum plate during heating and pressurization, so it was removed by immersing it in concentrated sulfuric acid for 20 seconds. .

At the end of the surface of the outermost layer, a portion where no circuit was formed was left as a heat dissipation promoting area. The area of this heat dissipation promotion area is
The combined area of the heat dissipation promotion area and the conductor circuit surface on the surface of the outermost layer was 15% of the total area.

Example 2 First, clearance processing was performed on an aluminum board (thickness: 150 μm), which was an outer layer material, to match the through-hole portion of the inner layer board, which had already been processed as a multilayer printed wiring board, and the conductor portion on the surface.

The clearance processing at this time was performed using a laser processing method. That is, an alumina plate having a penetrating portion with a predetermined clearance (+0.5 mm) was produced using a carbon dioxide laser.

One side of this alumina board was coated with epoxy resin adhesive to a thickness of 10 μm uniformly using a roll coater, and then layered on the surface of the multilayer printed wiring board (Figure 8), and heated and pressed using a press to coat the adhesive. After curing, a multilayer printed wiring board of the present invention was finally obtained (FIG. 9).

Comparative Example A multilayer printed wiring board was obtained by a conventional method without using a ceramic board.

At this time, the thickness of the copper foil used for the outermost layer on both sides was 18 μm, and prepreg was used as the insulating layer between the circuits thereunder as in Examples 1 and 2.

Next, these multilayer printed wiring boards (Examples 1 to 2,
In order to see the heat dissipation effect of Comparative Example, when an electronic component 8 that is a flat type IC and an electronic component 9 that is a DIP type IC are mounted on a multilayer printed wiring board 30 of a comparative example as shown in FIG. As shown in Fig. 11, the electronic component 8 which is a flat type IC in the multilayer print distribution % Fis o of the comparative example.
and an electronic component 9 which is a DIP type IC, and a heat dissipation fin (heat sink) is placed on top of these electronic components 8 and 9.
31, when an electronic component 8 which is a flat type IC and an electronic component 9 which is a DIP type IC are mounted on a multilayer printed wiring board 30 with a heat dissipation promotion area 32 of the example construction as shown in FIG. , and as shown in FIG. 13, the electronic component 8 which is a flat/flat type IC and the electronic component 9 which is a DIP type IC are mounted on the multilayer printed wiring board 30 of Example 2. .9 was evaluated for the dissipation of the generated heat. The results are shown in Table 1.
In Figures 0 to 13, arrows indicate heat radiation.

Specification: Multilayer printed wiring board with 8.9 electronic components mounted on 23±
It was placed horizontally on a desk in a room at 2°C, the power was turned on, and it was left for 30 minutes until it reached a thermal equilibrium state. Next, electronic parts 8
, 9 was applied with a temperature measuring probe, and the temperature was measured after about 5 minutes. The case of Fig. 10 (without heat dissipation fins) is 0%, and the case of Fig. 11 (with heat dissipation fins) is 100%.
It was evaluated as %.

(Margins below Book R) - As is clear from Table 1, the multilayer printed wiring board of the present invention has better heat dissipation properties than the conventional multilayer printed wiring board (without heat dissipation fins as shown in Figure 10). In other words, it can be seen that the heat dissipation property is excellent.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects can be achieved because the thermally conductive ceramic plate-like body with clearance processed at the location where the conductor portion is to be provided is disposed on the surface of the outermost layer.

■ Heat is distributed throughout the multilayer printed wiring board, avoiding heat concentration.

4゜■ The entire multilayer printed wiring board becomes a heat dissipation area, increasing the heat dissipation effect.

- By providing a heat dissipation promotion area, heat can be guided to the outside from the heat dissipation area, and the heat dissipation effect can be further enhanced.

■ Since heat dissipation fins are not required, the mounting density of the card assembly can be increased.

■ Since the temperature inside the equipment equipped with the multilayer printed wiring board does not rise, the reliability of the equipment is improved.

■ Since the ceramic plate has a small coefficient of thermal expansion, no warping is observed in the multilayer printed wiring board due to thermal expansion of the ceramic plate.

[Brief explanation of drawings]

1 and 2 are respectively cross-sectional explanatory diagrams of an example of a multilayer printed wiring board of the present invention, FIG. 3 is a cross-sectional explanatory diagram of an example of a conventional multilayer printed wiring board, and FIGS. 4 and 5 are respectively FIG. 2 is an explanatory diagram showing how electronic components are mounted on a multilayer printed wiring board. Fig. 6, Fig. 7 (A) - (E), and Fig. 8 (A) -
(D) is an explanatory diagram showing an example of the manufacturing process of the multilayer printed wiring board of the present invention. FIG. 9 is an explanatory diagram showing an example of a completed product of the multilayer printed wiring board of the present invention, and FIGS. 10 to 13 are explanatory diagrams showing how electronic components are mounted on the multilayer printed wiring board and a heat dissipation test is performed. It is. 1... Outermost layer surface, 2, 3... Conductor circuit surface, 4...
・Prepreg, 5... Through hole, 6... Ceramic plate, 7... Copper, 8.9... Electronic component, 1
DESCRIPTION OF SYMBOLS 1...#R foil, 12... Hole, 30... Multilayer printed wiring board, 31... Heat radiation fin, 32... Heat radiation promotion area.

Claims (1)

[Claims] A multilayer printed wiring board consisting of a thermally conductive ceramic plate-like body with clearance processed on the surface of the outermost layer where conductor parts should be provided.