JPH07147349A - Multilayer circuit board and its manufacture - Google Patents

Abstract

PURPOSE:To provide a multilayer circuit board in which a low-resistance conductor interconnection is built, whose thermal resistance is low and which is used for a small and high-density hybrid IC. CONSTITUTION:A multilayer circuit board has a structure wherein a conductor pattern 11 which forms a desired electric circuit is arranged on an insulator 18 and the conductor pattern 11 is connected electrically, by wires 19, to a heat-generating electronic circuit component 17. In the multilayer circuit board, a glass is used as the insulator 18, and a metallized layer 13, for discharging, which is electrically independent or which is connected to a grounding layer is formed in other surface parts excluding the conductor pattern arranged on the surface. The metallized layer is constituted preferably by using at least one out of Au, Ag, Cu, Pt and Pd as a main component, its ratio of area occupied to the surface area of the multilayer circuit board is preferably at least 20%, and its thickness is preferably 5 to 80mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer circuit board used in the electronics industry such as for consumer use and computers, and more specifically, it has a high-density multi-layer circuit containing low resistance conductor wiring and good heat dissipation. Substrate and manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, hybrid ICs have been required to be smaller and have a higher density, by forming electrode patterns on a green sheet by printing, laminating and sintering them, or by repeating screen printing. A ceramic multilayer wiring board having a wiring pattern inside the board by multilayering and sintering has been used. There are two main types of substrates. As one of them, for example, W and Mo are used as wiring conductors as described in Japanese Patent Publication No. 3-78798.
There is a ceramic multilayer substrate that is co-fired at a high temperature of 00 to 1600 ° C.

As another one, for example, JP-A-63-2
As disclosed in Japanese Patent No. 44899, usually 1000 ° C.
There are low-temperature sinterable ceramic substrates that can sinter the insulator at the following relatively low temperatures. The above-mentioned substrate fired at a high temperature has a high resistivity of the conductor, which makes it difficult to apply to a high-frequency circuit, and the wiring resistance increases, so that the circuit density cannot be increased by fine wiring. was there.

On the other hand, since a low temperature sinterable substrate has a low firing temperature, it is possible to use A as a conductor material for internal wiring to be fired at the same time.
So-called low resistance conductor materials such as u, Ag and Cu can be used. Therefore, the above-mentioned problem regarding the conductor resistivity can be solved. However, glass is usually used as an insulating material for this kind of low temperature sintered body substrate. This low temperature sinterable glass has extremely low thermal conductivity as compared with, for example, an alumina substrate. Therefore, if a heat-generating electronic component such as an LSI chip with large power consumption is mounted, the temperature of the substrate is likely to rise, and it is difficult to exhibit desired characteristics as a circuit.
This problem is even more prominent in a substrate having a high density because the heat generation density is high.

[0005]

As described above, there is a problem that it is difficult to obtain sufficient heat dissipation characteristics in a multilayer circuit board having a low resistance conductor wiring built-in and a heat generating electronic circuit arranged on the surface thereof. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a small-sized, high-density, multi-layer circuit board for the electronic industry including high-frequency applications, which has a built-in conductor wire having low resistance, and a manufacturing method thereof.

[0006]

In order to solve the above problems, according to the present invention, a conductor pattern forming a desired electric circuit is arranged on an insulator, and the conductor pattern and the heat-generating electronic circuit component are electrically connected. In a multi-layer circuit board having an electrically connected structure, glass is used as the insulator, and is electrically independent or connected to a ground layer on the other surface portion excluding the conductor pattern arranged on the surface. The metallization layer for discharge is formed.

In the above-mentioned multilayer circuit board, the heat-generating electronic circuit component is preferably placed on a part of the geometrically continuous metallization layer, and the metallization layer is
The multilayer circuit board has a surface area ratio of at least 2
The thickness is preferably 0%, the thickness is 5 to 80 μm, and the material is preferably composed mainly of at least one of Au, Ag, Cu, Pt, and Pd.

Further, in order to solve the above-mentioned other problems, in the present invention, a multilayer electronic circuit having an electronic circuit in which a conductor layer is arranged on an insulating layer made of a glass material and which realizes desired electric characteristics. In the method for producing a substrate, a metallized layer that is electrically insulated from the electronic circuit and has an area ratio of at least 20% to the surface of the substrate is formed in the surface layer portion, and the heat-generating electron is formed on the metallized layer. The parts are to be placed.

As described above, in the present invention, the metallization layer for heat dissipation having high heat conductivity such as Au, Ag, and Cu is provided on the surface layer portion of the substrate on which the insulating material is laminated, which constitutes a predetermined electric circuit. A multilayer circuit board for the electronic industry, which is small in size, has a high density, and has high-frequency applications, has a highly accurate electrical characteristic by facilitating heat dissipation from the board by arranging it electrically isolated from the pattern. It will be realized.

As described above, the insulating material is usually made of low temperature sinterable glass having a low softening point and is fired at the same time as the wiring conductor. There are the following two methods for forming the heat dissipation metallization layer in the surface layer portion. One is a method of directly forming the metallization layer for heat dissipation on the surface portion of the substrate where the surface layer circuit pattern does not exist. The other one is
In this method, an insulating layer for coating is first formed on the surface circuit pattern, and then the metallized layer is formed thereon. The former is a simple method, and the latter has a high degree of freedom in pattern design and has a larger heat dissipation effect. By forming the heat dissipation metallization layer on the surface of the laminated circuit board according to the present invention, heat dissipation from the board is facilitated, high-precision electrical characteristics are achieved, and high-density conductive wiring with low resistance is built in. The multilayer circuit board of is obtained.

For example, by using lead borosilicate glass as the insulating material for the inner layer of the multilayer circuit board according to the present invention, it is possible to sinter even at a temperature of about 850 ° C.
Low resistance conductor wiring can be built in, and
By providing the heat dissipation metallized layer made of a material having high thermal conductivity such as u, Ag, or Cu, heat dissipation characteristics can be improved. Since the multilayer circuit board obtained by the present invention includes the metallization layer for heat dissipation in the surface layer and has the conductor wiring with the built-in low resistance, the portable camera-integrated video device and the signal are speeded up. It can be effectively used as an electronic circuit board that constitutes a communication electronic device or a computer.

[0012]

The present invention has a structure in which a conductor wire having a low resistance is built in, a heat dissipation metallization layer is formed on the surface of the conductor wire, and a heat-generating electronic component is arranged. Therefore, the tendency for the heat generated in the electronic circuit to stagnate locally is improved, and the heat is dispersed over a large area,
It can dissipate heat efficiently into the atmosphere. This is
Regarding the thermal conductivity, the glass used as the insulator has a thermal conductivity of 2 W / mk, while the discharge metallized layer used in the present invention has a thermal conductivity of 4 W / mk.
Because it is 20 W / mk. Incidentally, the thermal conductivity of AlN is 200 W / mk and BeO is 300 W / mk, and when these are used as the insulator, the metallization layer is not necessary. Therefore, it is also effective for increasing the circuit density.
Further, the metallized layer formed on the surface layer of the substrate has a function of absorbing and reducing unnecessary radiation waves.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples. Embodiment 1 FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 shows a partial cross-sectional view including a heat-generating electronic component of a multilayer circuit board according to the present invention, and FIG. 2 shows a plan view thereof. The multilayer circuit board is manufactured as follows. First, lead borosilicate glass powder and alumina powder as heat resistant frit,
Add an organic solvent such as polyvinyl butyral and stir to make a sludge. This sludge is made into a green sheet by a casting film forming method using a doctor blade, and a plurality of unfired electrically insulating green sheets are formed.

Next, the green sheet is formed by inserting a mold made of stainless steel or the like and punching the outer shape and a plurality of holes (via holes) at the same time. On this green sheet, a conductor paste containing silver as a main component, which usually has a resistivity lower than 3 μm Ω-cm, is applied by a screen printing method to form a surface layer pattern 11 or an inner layer conductor wiring 14 and a via hole 16. Fill. It stacks up sequentially using a plurality of similarly prepared green sheets. Then, using a heat press machine or the like, a temperature of 120
A green sheet laminate is obtained by thermocompression bonding from the upper and lower surfaces under the conditions of ° C and pressure of 200 kg / cm ² .

This molded body was degreased in air at a temperature of 350 ° C. for about 1 hour, and then 800-1000 in air as well.
By firing at 10 ° C. for about 10 minutes, a multi-layer circuit board in which the low-resistance inner-layer conductor wiring portion 14 is embedded in the low-temperature sinterable glass-ceramic composition portion 18 is obtained. A coating insulating layer 20 is formed on a surface layer portion of the substrate other than a portion where a chip component, a passive element or the like is arranged, and a conductor paste is used for screen printing-drying and firing to radiate a metallizing layer for heat radiation. 13 is formed. Further, Ru is placed at a predetermined position on this substrate.
After forming the resistor 12 mainly composed of O ₂ by screen printing, it is dried and baked to form a thick film resistor. Usually, a glass paste is further printed-dried on this resistor and baked at a low temperature of 600 ° C. or lower to form a protective glass film 15 to form a multilayer circuit board. An electronic component 17 including a heat-generating LSI chip is mounted on this substrate,
If necessary, they are electrically connected by means such as wire bonding 19 to complete the multilayer circuit board.

In this embodiment, the wire bonding 19 is used as an LSI chip connecting method.
Other methods such as TCP (Tape Carrier Package) or CCB (Chip Carier Bonding) or LCC (Le
It may be a means such as adless Chip Carier). Further, although an example using Ag as the conductor material of the inner layer has been described in detail, Au, Pt, Pd and alloys thereof can also be used in the same manner. Similarly, Cu can be applied by firing in an inert gas.

Example 2 By the same procedure as in Example 1, a multi-layer circuit board in which the low-resistance inner layer conductor wiring portion 14 was embedded in the low temperature sinterable glass ceramic composition portion 18 was obtained. A copper coating having a thickness of about 2 μm is formed on the entire surface of the surface layer portion connecting the LSI chip on this substrate by electroless plating. Further, the thickness of the copper coating is increased to about 25 μm by the electrolytic plating method.
Number of layers: 5 layers, 50 mm, including a heat dissipation metallization layer 13 having a desired shape by using a so-called photoresist method in which a photosensitive resin is applied to the surface of the film and patterned.
A multilayer substrate having a corner and a thickness of 0.8 mm was produced. Thus, by forming the heat dissipation metallization layer 13 by the plating method, good film thickness controllability and surface smoothness of the film can be obtained.

Example 3 By the same procedure as in Example 1, a multi-layer circuit board in which the low-resistance inner layer conductor wiring portion 14 was incorporated in the low temperature sinterable glass ceramic composition portion 18 was obtained. The metallized layer 13 is formed by using a so-called direct bonding method in which a copper foil is directly bonded to the surface layer portion of the substrate to which the LSI chip is connected. In this method, the copper oxide formed on the surface of the copper foil and the oxide forming the ceramic substrate are bonded by a chemical reaction. Usually, the bonding process temperature is equal to or higher than the eutectic point (1065 ° C.) of the copper oxide, Melting point of copper (1
083 ° C) or lower. The copper foil used here may cover the entire surface, or may be optionally patterned in advance. Example 2 in the former case
Similarly, the metallization layer 13 for heat radiation having a desired shape is formed by using the photoresist method.

Example 4 According to the same procedure as in Example 1, the number of conductor layers was 5 and the length was 50 m.
A multi-layer substrate having an m-square and a thickness of 0.8 mm and including the heat dissipation metallization layer 13 was produced. At this time, the heat dissipation metallization layer 1
The area ratio occupied by 3 is 7.8 with respect to the surface area of the substrate on one side.
%, 15%, 30%, 50%, and 75% were adjusted in five stages to form a pattern, and the film thickness was constant at 15 μm. 11.6mm square, power consumption 1.
One 7W LSI 17 is mounted for wire bonding 1
9 was used to connect to a predetermined portion of the substrate.

For each of these five types of substrates, L
The rated power was added to SI, and the steady-state temperature of the LSI surface was measured under the condition that the air velocity was 2 m / sec on the substrate surface. As a result, the temperature is higher in the ascending order of the area ratio of the metallized layer 13,
77.5 ° C, 75 ° C, 68.5 ° C, 48 ° C, 4
It was 1.5 ° C. From this result, it can be said that the heat dissipation effect is insufficient when the area ratio is 20% or less, but practically, it is preferable to form the heat dissipation metallization layer 13 having an area ratio of more than 20%.

Example 5 A test sample having an area ratio of the heat dissipation metallized layer to the entire substrate of 50% was prepared by the same procedure as in Example 2. At this time, the film thickness of this metallized layer was adjusted in 10 steps in the range of 3 μm to 200 μm by changing the screen printing conditions. The heat dissipation effect of the completed sample was evaluated in the same manner as in Example 2. As a result, the heat dissipation effect was insufficient when the film thickness was 5 μm or less. On the other hand, the film thickness is 80
When the thickness is more than μm, the strength of the metallized layer is relatively increased as compared with the ceramic substrate, and the substrate itself is deformed, which is not preferable. Therefore, it is necessary to set the film thickness of the metallized layer in consideration of both strength and heat dissipation effect of the ceramic substrate. Under the conditions of this embodiment, the film thickness is 5 μm.
It can be said that m-80 μm is the selectable proper film thickness range.

Embodiment 6 FIG. 3 shows an application example of the present invention. The figure shows a schematic diagram of the configuration of a communication electronic exchange system. A circuit module 35 according to the present invention including a heat generating LSI chip element 34 is constructed. A mother board 33, which is a multilayer printed circuit board on which the circuit module 35 is mounted, is mounted on the housing 32 to form a series of exchange circuit systems. The heat generated from the circuit is discharged to the outside of the system by the upward airflow of the fans 31 installed in the upper and lower parts of the housing 32.

In the present embodiment, an example of the cooling method by the air flow is shown. However, for example, this is a water cooling type or a method of directly cooling from the heat radiation metallization layer 13 formed in the circuit module 35 by using a heat pipe. High cooling effect can be expected. Although all of the above examples show examples of ceramic multilayer circuit boards, the present invention can be applied to, for example, a printed wiring board using glass epoxy as an insulating material. Further, as the means for forming the metallizing layer for heat dissipation, an example using a thick film and an example of plating or direct joining of copper foils are shown, but means combining these are also applicable.

[0024]

According to the present invention, since a low-resistance conductor wiring can be built-in and a low-heat resistance multilayer circuit board can be formed, it is possible to make the conductor pattern finer and to reduce the wiring from the board. The excellent heat dissipation property can contribute to downsizing or high density of electronic circuits, and can be effectively used especially for high speed or high frequency circuits. Furthermore, there is an effect of reducing noise due to unnecessary radiated radio waves.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a multilayer circuit board according to an embodiment of the present invention.

FIG. 2 is a plan configuration diagram of the multilayer circuit board of FIG.

FIG. 3 is a schematic configuration diagram of a communication electronic exchange system using the present invention.

[Explanation of symbols]

11: surface layer conductor pattern, 12: film thickness resistor, 13: heat dissipation metallized layer, 14: inner layer conductor, 15: protective glass film, 16: via, 17: heat generating electronic component, 18: insulator glass ceramic composition part , 19: bonding wire, 20: insulating layer for coating, 31: fan, 32: housing,
33: Motherboard, 34: Exothermic LSI chip, 3
5: Circuit module, 36: Lead pin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Hasegawa 7-1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A multi-layer circuit board having a structure in which a conductor pattern for forming a desired electric circuit is arranged on an insulator, and the conductor pattern and a heat-generating electronic circuit component are electrically connected to each other. A multi-layer circuit board characterized in that glass is used as a substrate, and a metallization layer for discharge is formed on the other surface portion excluding the conductor pattern arranged on the surface, either electrically independent or connected to a ground layer. . 2. The multilayer circuit board according to claim 1, wherein the heat-generating electronic circuit component is mounted on a part of the geometrically continuous metallization layer. 3. The multilayer circuit board according to claim 1, wherein the metallized layer occupies at least 20% of the surface area of the multilayer circuit board. 4. The metallized layer is made of Au, Ag, C
The multilayer circuit board according to claim 1, 2 or 3, wherein at least one of u, Pt, and Pd is a main component. 5. The metallized layer has a thickness of 5 to 80 μm.
The multilayer circuit board according to any one of claims 1 to 4, wherein m is m. 6. A method for producing a multi-layer electronic circuit board, wherein a conductor layer is arranged on an insulator layer made of a glass material, and the conductor layer is electrically insulated from the electronic circuit in a method of manufacturing the same. And a metallization layer having an area ratio of at least 20% to the surface of the substrate is formed in the surface layer portion, and a heat-generating electronic component is placed on the metallization layer. Manufacturing method.