JPS6284595A - Multilayer ceramic wiring 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 are becoming widely used for industrial and civilian purposes.

In particular, multilayer ceramic substrates are attracting attention as mounting substrates for high-speed operation L8Is with high integration density. This multilayer ceramic substrate can directly mount an LSI, and allows fine multilayer wiring.

General〈Alumina is mainly used as a material for ceramic substrates, but in recent years electrical devices have become smaller and smaller.
There is a strong trend toward higher circuit densities, and the demand for higher integration of elements and circuit elements per unit area of the substrate is increasing. On the other hand L8
In I, the heat generated from the chip tends to increase as the chip 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. Therefore,
Insulating substrates that have higher thermal conductivity and better heat dissipation than alumina substrates have become necessary.

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 electrically belongs to a semiconductor, has a specific resistance of about 1 to 10 Ω·m, and is highly electrically insulating, so it can 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 during sintering. 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°Ω.
- 1 or more points. However, the dielectric constant, which is one of the important force factors in mounting board traps such as L8I, is quite high at 40 at 1MHz, and even with the addition of additives, the insulation between particles decreases rapidly when the voltage is about 5V. Therefore, there is also a problem with the withstand voltage.

Furthermore, although it is possible to create a multilayer chiramic 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 not only requires a large equipment but also makes it difficult to increase the shape of the substrate, making it difficult to achieve surface smoothness. There are also 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 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 used to form a sheet having a thickness of about 10 μm to 400 μm on an organic film by a casting method. After cutting the sheet into a predetermined size and forming through holes for establishing electrical conduction between each layer, a predetermined conductor pattern is formed using a thick film printing method. These ceramic green sheets with each conductor pattern fully formed are laminated and pressed,
After a binder removal step, it is 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 the mainstream manufacturing method is the hot press method.
A nine-layer wiring board using aluminum nitride has yet to be realized.

(Objective of the Invention) An object of the present invention is to provide a high-density, high-thermal-conductivity multilayer ceramic wiring board that eliminates the above-described drawbacks of the conventional ceramic wiring board and has excellent thermal conductivity and has a conductor inside.

(Structure of the Invention) According to the present invention, the ceramic structure is composed of a polycrystalline body mainly composed of aluminum nitride, and the main component of the conductor layer is composed of zirconium metal or a mixture of zirconium metal and zirconium nitride. A multilayer ceramic wiring board with characteristic high thermal conductivity can be 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 insulating ceramic material constituting the multilayer ceramic board. 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 L8I 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. Reference numeral 1 denotes an insulating ceramic layer, which is mainly composed of polycrystalline aluminum nitride. 2 is a conductor layer for signal lines, power supplies, etc., and is mainly made of zirconium metal or a mixture of zirconium metal and zirconium nitride, and conducts electricity between each layer through a peer hole 3 formed in the insulating ceramic layer. connected. On the multilayer ceramic substrate/C configured in this way, a die pad 4 and a bonding pad 5 are formed so that the L8I chip can be mounted, and the die pad 4 and the bonding pad 5 are formed so that the L8I chip can be mounted. An input/output pad 6 is formed on the back surface of the board.

Diffuse the heat generated from the LSI chip mounted on the substrate into the ceramic substrate via the die pad 4.

The high thermal conductivity of the ceramic substrate allows for efficient heat diffusion, which prevents the L8T chip from heating up and becoming too hot.

The method for manufacturing the wiring board of this example is as follows. Ceramic materials constituting the substrate of the present invention include:
C is added as an additive to improve the sinterability of aluminum nitride.
Contains aC1. Albanium oxide powder)
:Weigh CaC2 powder and wet mix in an organic solvent using a ball mill for 48 hours.This mixed powder is mixed with an organic binder that easily decomposes in a neutral atmosphere, such as polycaprolactone or polyacrylate resin, in a solvent. Dispersed in viscosity: +000~
Creates a sludge in the 7000cp range.

The slurry was coated with a coating film of 10μ to 200μ by the casting method.
A green sheet is created on the organic film so that it has a uniform thickness of 8 μm.

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 zirconium metal or a mixture of zirconium metal and zirconium nitride when fired under a ♀ cumulative atmosphere or other neutral atmosphere or reducing atmosphere is applied onto the green sheet in which the pier holes are formed. A predetermined pattern is printed at a predetermined position using a screen printing method. A desired number of green sheets having conductors printed thereon are laminated and hot pressed. After that, use a cutter to cut it into the required shape, 14
Calcinate in a non-oxidizing atmosphere at a temperature of 00'C to 2000C. During firing, the temperature rises from 4009C to 600℃
The binder was sufficiently removed at a temperature of .

The characteristics of the fabricated substrate are shown in the table.

Below, Zr metal, ZrN & ZrH are used as conductor paste materials.
l was used. The value t of the additive (CaC1) 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 1.
Q11Q working z or more, and the dielectric constant is 8.7 (IMHzχ
The dielectric loss was less than 1×10″S (IMUz).

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.

- CaO, BeO, Y2O3, Cub as power additives,
Ago.

Back, 5rC2, Na2C2, 2C1, CuC
Even when 2, MgC2, Ag2C2, Zr (4, etc.) were used, the effect of improving the sinterability of aluminum nitride was obtained.

(Effects of the Invention) As is clear from the examples, according to the present invention, it is possible to easily form a high-density variable power circuit having conductors including signal lines, power supply layers, etc., and the heat dissipation property is also improved. A highly effective and highly thermally conductive multilayer ceramic circuit board can be obtained.

The thermal conductivity of the conventionally used alumina substrate is 17 W.
/inK, which shows that the thermal conductivity of the substrate of the present invention is at an extremely high level. In addition, regarding the coefficient of thermal expansion,
While the alumina substrate has a value of 65 x 1O-77C, the substrate of the present invention has a small force value and is advantageous because it has a coefficient of thermal expansion closer to that of a silicon chip.

[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-13... Pier hole, 4... Die pad, 5... Bonding pad, 6... Input/output pad.

Claims (1)

[Claims] 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 zirconium metal alone or a mixture of zirconium metal and zirconium nitride are used. A multilayer ceramic wiring board characterized by: