JPS6276592A - Multilayer ceramic circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly thermally conductive multilayer ceramic wiring board.

(Prior art and its problems) With the rapid development of semiconductor technology, ICs and LSIs have come to be widely used for industrial and civilian purposes.

In particular, multilayer ceramic substrates are attracting attention as mounting substrates for high-speed operation LSIs with high integration density. This multilayer ceramic substrate can directly mount an LSI, and allows fine multilayer wiring.

Generally, alumina is mainly used as the material for ceramic substrates, but in recent years electrical devices have become smaller and smaller.
There is a strong demand for higher density circuits, and the degree of integration of elements and circuit elements per unit area of the substrate is increasing. On the other hand, LSI
, the chip tends to generate more heat as it operates at higher speeds. As a result, the heat generated by the substrate increases significantly, and the problem arises that the alumina substrate does not have sufficient heat dissipation properties. Therefore, there is a need for an insulating substrate that has higher thermal conductivity and better heat dissipation than an alumina substrate.

Therefore, a ceramic substrate mainly composed of silicon carbide was developed as a material with excellent heat dissipation properties (Japanese Patent Laid-Open No. 57
-180006). Silicon carbide itself is electrically layered on a semiconductor, has a specific resistance of about 1 to 10 Ω·1, and has no electrical insulation properties, so it cannot be used as an insulating substrate. Furthermore, since silicon carbide has a high melting point and is very difficult to sinter, it is usually sintered using a so-called hot press method in which a small amount of sintering aid is added and pressure is applied at high temperature. When beryllium oxide or boron nitride is used as this sintering aid, it is effective not only for the sintering aid but also for electrical insulation, and the specific resistance of the sintered substrate mainly composed of silicon carbide is 101%.
It becomes 0Ω・1 or more. However, the dielectric constant, which is one of the important factors in mounting boards such as LSI, is as high as 40 at 1 MHz, and even with the addition of additives, the insulation between particles drops rapidly when the voltage reaches 5V and 8 degrees. Therefore, there is also a problem with the withstand voltage.

Furthermore, although it is possible to create a multilayer ceramic substrate using BeO powder, it is difficult in practice due to its toxicity.

On the other hand, from a process standpoint, a hot press method must be applied, which not only makes the equipment bulky, but also makes it difficult to increase the size of the substrate, and there are problems with surface smoothness. There are many. Furthermore, in the case of ceramic substrates using silicon carbide, it is extremely difficult to use alumina multilayer ceramic substrate technology using the conventional green sheet method in terms of process.

The green sheet multilayer ceramic substrate technology referred to herein is the following technology. First, ceramic powder is mixed with an organic vehicle to form a slurry. This slurry is cast onto an organic film to form a sheet having a thickness of about 10 μm to 400 μm.

After cutting the sheet into a predetermined size and forming through holes for obtaining conduction between each layer, a predetermined conductor pattern is formed by a thick film printing method. The ceramic green sheets on which each of these conductor patterns have been formed are laminated and pressed, subjected to a binder removal step, and then fired.

The main properties that a high-density mounting board should have are (
1) It has a low dielectric constant with respect to its electrical properties, low dielectric loss, and is electrically insulating; (2) it has sufficient mechanical strength; (3) it has high thermal conductivity. (4)
Thermal expansion is close to that of silicon/chips, etc. (5
) It must have excellent surface smoothness, and 1'6) It must be easy to apply high-density heat treatment.

It cannot be said that the above-mentioned ceramic substrates are sufficient for all of these substrate properties.

On the other hand, aluminum nitride has been developed as a material for substrates with high thermal conductivity (Japanese Patent Laid-Open No. 59-50077, etc.). However, this material must also be sintered at a high temperature, and a hot pressing method has become the mainstream, and a multilayer wiring board using aluminum nitride has not yet been realized.

(Object of the Invention) The present invention aims to eliminate the drawbacks of the conventional ceramic wiring boards mentioned above and provide a high-density, high-thermal-conductivity multilayer ceramic wiring board having excellent heat conductivity and having conductors inside. be.

(Structure of the Invention) According to the present invention, the ceramic structure is composed of a polycrystalline body containing aluminum nitride as a main component, and the main component of the conductor layer is composed of a mixture of metal boride and metal carbide. A highly thermally conductive multilayer ceramic wiring board is obtained.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration.

First, aluminum nitride, which has high thermal conductivity, was used as the incomparable ceramic material constituting the multilayer ceramic substrate. After firing, this material forms a dense structure of polycrystalline aluminum nitride. In order to obtain a high heat transfer rate, it is preferable that the sintered body contains less oxygen, and therefore it is preferable to add a reducing agent having a reducing effect as an additive.

Regarding conductor layers, multiple power layers, ground layers, fine signal lines, and other conductor layers are formed on a ceramic layer made of aluminum nitride, and these multiple conductor layers are provided within the ceramic layer. It is electrically connected via a peer hole.

Therefore, the wiring density of the mounting board can be greatly increased, and the heat generated from elements such as LSI can be efficiently dissipated to the outside.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an embodiment of a highly thermally conductive multilayer ceramic substrate according to the present invention. 1 is an insulating ceramic layer, which is mainly composed of polycrystalline aluminum nitride. 2 is the conductor layer for the signal + F wire and power supply, etc.
Pier hole 3 is formed mainly from a mixture of metal boride and metal carbide, and is formed in an insulating ceramic layer.
Each layer is electrically connected via .eta.j'. A die pad 4 and a bonding pad 5 are formed on the multilayer ceramic substrate configured in this manner so that an LSI chip can be mounted. An input/output pad 6 is formed on the back surface of the substrate. Heat generated from the LSI chip mounted on the substrate is diffused into the ceramic substrate via the die pad 4. The high thermal conductivity of the ceramic substrate allows for efficient heat diffusion, thereby preventing the LSI chip from increasing in temperature due to heat generation.

The method for manufacturing the wiring board of this example is as follows. The ceramic material constituting the substrate of the present invention includes:
C as an additive to improve the sinterability of aluminum nitride
aC, all are mixed. Aluminum nitride powder and CaC powder were weighed in ff amounts, and wet mixed in an organic solvent using a ball mill for 18 hours.

This mixed powder is dispersed in a solvent together with an organic binder that is easily decomposed in a neutral atmosphere, such as polykabu o, y lactone or polyacrylate resin, and the viscosity is 3000-7.
Create a slurry in the range of 000ep. F) A green sheet is prepared on an organic film so that the slurry has a uniform thickness of about 10 pm to 200 pm by a casting method.

Next, after this green sheet is peeled off from the organic film, peer holes are formed to electrically connect each layer. The pier holes formed here were punched out mechanically using a punch and die, but they can also be punched out by other methods such as laser machining.

A conductive paste whose main component is a compound that becomes a mixture of metal boride and metal carbide when fired in a nitrogen atmosphere, other neutral atmosphere, or reducing atmosphere is screen printed onto a green sheet with peer holes formed. A predetermined pattern is printed at a predetermined position. A desired number of green sheets having conductors printed thereon are laminated and heated under heat. Thereafter, it is cut into the desired shape using a cutter and fired in a non-oxidizing atmosphere at a temperature of 1400° C. to 2000 t. During firing, the temperature rises to 40
The binder was sufficiently removed at a temperature of 0°C to 600°C. Table 1 shows the composition of the conductive paste used in the prepared samples, and Table 2 shows the characteristics of the samples.

The following white conductor paste materials include T iB*, MoB, and VB.
, .

ZrB, , HfB, , NbJ, TaB, , and HfC, N
bC, TaC.

T+C, UC, 'VC, and ZrC were used.

The amount of additive (CaCs) shown here is the value when aluminum nitride is taken as 100. Further, the frit weight is a value relative to the combined weight of the conductor material and the frit material.

As a result of measuring the electrical characteristics of the created substrate, the specific resistance was 1.
0'1Ω・1 or more, dielectric constant is 87 (IMHz),
The dielectric loss was less than lXl0-3 (IMHz). It can be seen that the electrical characteristics are also at least the same as those of conventional boards, and are sufficient as a mounting board.

On the other hand, as additives CaO, B e O, Y, O*,
Cu O.

Ago, BaC,, S rC,, Na, C,, K, C
1.CuC,.

The effect of improving the sinterability of aluminum nitride was also obtained by using MgC9, AgtC*, Zrcl, etc.

(Effects of the Invention) As is clear from the examples, by having the structure of the present invention, it is possible to easily form a high-density circuit having conductors including signal lines and power supply layers, and to improve heat dissipation. A highly thermally conductive multilayer ceramic wiring board which is also very effective in terms of performance can be obtained.

The thermal conductivity of the conventionally used alumina substrate is 17W/
mK, which indicates that the thermal conductivity of the substrate of the present invention is at a very high level. In addition, the thermal expansion coefficient of the alumina substrate is 65X 1 o-'/l; whereas the present substrate has a small value, which is closer to the thermal expansion coefficient of a silicon chip, which is advantageous. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a highly thermally conductive multilayer ceramic wiring board showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 -- Insulating ceramic layer, 2 -- Conductor layer, 3 -- Pier hole, 4 -- Die pad, 5 -- Ponding pad, 6 -- Hitodeba pad.

Claims (3)

[Claims] (1) In a multilayer ceramic wiring board in which a conductor is formed three-dimensionally through a ceramic layer, a ceramic layer whose main component is aluminum nitride and a conductor whose main component is a mixture of metal boride and metal carbide are used. A multilayer ceramic wiring board characterized by: (2) The metal boride is one or more substances selected from titanium boride, tantalum boride, zirconium boride, niobium boride, vanadium boride, molybdenum boride, and hafnium boride. A multilayer ceramic wiring board according to scope 1. (3) The multilayer ceramic according to claim 1, wherein the metal carbide is one or more substances selected from zirconium carbide, tantalum carbide, niobium carbide, vanadium carbide, uranium carbide, hafnium carbide, and titanium carbide. wiring board.