JPS6271294A - 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 multilayer ceramic substrate, particularly a highly thermally conductive multilayer ceramic substrate using zirconium nitride as a conductor.

(Prior art and its problems) With the dramatic progress in 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 a substrate is increasing. On the other hand, LSI
, the higher the speed of operation, the more heat generated from the chip tends to become a trap. As a result, the heat generated by the substrate increases significantly, and in the alumina substrate, an interlayer is formed in which the heat dissipation property is insufficient. Therefore, an insulating substrate, which has high thermal conductivity as well as alumina substrates and is concerned about heat dissipation, has become necessary.

Therefore, a ceramic substrate mainly composed of silicon carbide was developed as a material with excellent heat dissipation properties.
-180006). Silicon carbide itself electrically belongs to a semiconductor, has a specific resistance of about 1 to 10 Ω·1, and has poor 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 produced by the 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 10'6Ω.
・It will be 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 IMHz, and even with the addition of additives, the insulation between particles drops rapidly when the voltage reaches about 5V. 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 point of view, it is necessary to apply the hot press method, which makes the equipment large and bulky), and the shape of the substrate makes it difficult to increase the area, and the surface smoothness is also affected. There are many problems. 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 method multilayer ceramic substrate technology referred to here is the technology shown below. First, ceramic powder is mixed with an organic vehicle to form a slurry. This slurry is formed into a film of 10 mm to
A sheet having a certain thickness is formed on the organic film. After cutting the sheet into a predetermined size and forming through holes for establishing conduction between each layer, a predetermined conductor pattern is formed by thick film printing. 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) Low dielectric constant with respect to electrical properties, low dielectric loss, and excellent electrical insulation, (2) Sufficient mechanical strength, (3) High thermal conductivity, ( 4)
The coefficient of thermal expansion is close to that of silicon chips, etc. (5
) It must have excellent surface smoothness, and (6) it must be easy to increase the density.

The above-mentioned ceramic substrates cannot be said to be sufficient in terms of these substrate properties in general.

On the other hand, aluminum nitride has been developed as a material for highly thermally conductive substrates (Japanese Unexamined Patent Publication No. 59-50077, etc.)
. However, this material also has to be sintered at high temperatures, and hot pressing has become the mainstream manufacturing method.
A multilayer wiring board using aluminum nitride has not yet been realized.

(Purpose of the invention) The invention has excellent thermal conductivity, has a high density conductor inside,
An object of the present invention is to provide a multilayer ceramic substrate with high thermal conductivity.

(Structure of the Invention) According to the present invention, there is provided a highly thermally conductive multilayer ceramic wiring board characterized in that the ceramic layer is composed of a polycrystalline body mainly composed of aluminum nitride, and the conductor layer is mainly composed of zirconium nitride. can get.

(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 insulating ceramic material 7 constituting the multilayer ceramic substrate. After firing, this material forms a dense structure of polycrystalline aluminum nitride. In order to obtain high thermal conductivity, it is preferable that the amount of oxygen contained in the sintered body is small, and therefore it is preferable to add a reducing agent having a reducing effect as an additive.

Next, regarding the conductor layer, multiple conductor layers such as a power supply layer, a ground layer, and fine signal lines are formed on a ceramic layer made of aluminum nitride, and these multiple conductor layers are provided in 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. Reference numeral 2 denotes a conductor layer for signal lines, power supply, etc., which is mainly made of zirconium nitride, and electrically connects each layer through a peer hole 3 formed in the insulating ceramic layer. 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, and a die pad 4 and a bonding pad 5 are formed to allow signals to be taken out from the mounting board or input into the board. A blade pad 6 for sharpening is formed on the back surface of the board. Heat generated from the LSI chip mounted on the substrate is diffused into the ceramic substrate via the die pad 4. Due to the high thermal conductivity of the ceramic substrate, heat diffusion is carried out efficiently.
It is possible to prevent the chip from increasing in temperature due to heat generation.

The method for manufacturing the wiring board of this example is as follows. Ceramic materials constituting the substrate of the present invention include:
C as an additive to improve the sinterability of aluminum nitride
ab, is mixed. First, aluminum nitride powder and CaC powder were weighed and wet mixed in an organic solvent using a ball mill for 48 hours.

This mixed powder is dispersed in a K11 medium with an organic binder that is easily decomposed in a neutral atmosphere, such as polycaprolactone or polyacrylate resin, and the viscosity is 3000~
Make 1 serum in the range of 7000 cp.

The mud leaves are coated with F>10pm~zo by casting film forming method.
OPM A green sheet is created on an organic film so that it has a uniform thickness.

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 mainly composed of a zirconium compound, which becomes zirconium nitride when fired in a nitrogen atmosphere, other neutral atmosphere, or reducing atmosphere, is placed in a predetermined position onto the green sheet in which the pier holes are formed using a screen printing method. Print a predetermined pattern. A desired number of green sheets having conductors printed thereon are laminated and hot pressed. 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°C. During firing, the temperature rises to 40
The binder was sufficiently removed at a temperature of 0° C. to 600″C. The properties of the prepared substrate are shown in the table.

Below, ZrN, ZrHe, ZrF4, and Zr(QC,H,)4 were used as blank conductor paste materials.

The CaC* value shown here is the value when aluminum nitride is taken as 100. Further, the amount of frit 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 l
Must be O″Ω・1 or more, dielectric constant is &7 (IMHz),
The dielectric loss was less than 1×10 (IMHz). It can be seen that the electrical characteristics are also equivalent to or higher than conventional boards, and are sufficient as a mounting board.

On the other hand, CaO, B as additives to aluminum nitride
@o, YIOI, CuO, AgO, BaC, firc,
.

N*@C@, ni@C@, CuC@, M,,c,
, kg@C@, ZrC@, etc., the effect of improving the sinterability of aluminum nitride was obtained.

(Effects of the Invention) As is clear from the examples, the multilayer ceramic wiring board of the present invention can easily form a high-density circuit having conductors including signal lines and power supply layers, and has excellent heat dissipation properties. However, a highly effective multilayer ceramic substrate with high thermal conductivity can be obtained.

The thermal conductivity of the conventionally used alumina substrate is 17W/
mK, it can be seen that the thermal conductivity of the substrate of the present invention is at a very high level. Further, in terms of thermal expansion coefficient, while the alumina substrate has a coefficient of 65 x 10''/l, the substrate of the present invention has a small value, which is advantageous because it is close to that of a silicon chip.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a highly thermally conductive multilayer ceramic substrate showing an embodiment of the present invention. 1--Insulating ceramic layer, 2
--- Conductor layer, 3 --- Pier hole, 4 --- Die pad, 5 --- Bonding pad, 6- --- Input/output pad.

Claims (1)

[Claims] A multilayer ceramic wiring board comprising a ceramic layer containing aluminum nitride as a main component and a conductor containing zirconium nitride as a main component.