JPS6276591A - 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 progress of semiconductor technology, IC.

L8I is becoming 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 is directly connected to LS1. 〇Generally, alumina is mainly used as the material for ceramic substrates, but in recent years electrical devices have become smaller and there is a strong demand for higher circuit densities. , the degree of integration of elements and circuit elements per unit area of the substrate is increasing.On the other hand, in LSIs, as they operate at high speeds, the chips tend to generate more heat. 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 insulating substrates that have high thermal conductivity and excellent heat dissipation properties, as well as alumina substrates.

Therefore, a ceramic substrate containing silicon carbide as a main component was developed as a material with excellent heat dissipation properties [JP-A-57
-180006 Publication]. Silicon carbide itself electrically belongs to a semiconductor, and has a resistivity of about 1 to 10 Ω・tan and is not electrically insulating, so it cannot be used as an insulating substrate.In addition, silicon carbide has a high melting point and is extremely difficult to sinter. Because it is difficult to sinter, a small amount of sintering aid is usually added during sintering, and the so-called hot press method is used, which involves applying pressure at high temperatures.

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 100.
・It becomes more than Tan. However, the dielectric constant, which is one of the most important factors in mounting boards such as %LSI, is as high as 40 at 1 h, and even with the addition of additives, the insulation between particles deteriorates when the voltage reaches about 5 V. There is also a problem with the withstand voltage due to the rapid drop in O.Also, although it is possible to create a multilayer ceramic substrate using BeO powder, it is difficult to put into practical use due to its toxicity.

On the other hand, from a process perspective, a hot press method must be applied, which not only increases the size of the equipment, 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. A sheet having a thickness of about IO μm to 400 μm is formed on an organic film by casting this slurry. After cutting the sheet into a predetermined size and forming through-holes for establishing conduction between each layer, a predetermined conductor pattern is formed using a thick film printing method. The green sheets are laminated and pressed, undergo a binder removal process, 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
) excellent surface smoothness, and (6) Ei1@
The above-mentioned ceramic substrates cannot be said to be sufficient for these general substrate properties, such as being easy to heat conductive. On the other hand, aluminum nitride is used as a material for highly thermally conductive substrates. It has been developed (Japanese Unexamined Patent Publication No. 1983-
50077, etc.). However, this material also has to be sintered at high temperatures, and hot-pressing is the mainstream manufacturing method, and a multilayer wiring board using aluminum nitride has not yet been realized.

(Object of the Invention) The present invention is to provide a high-density, high-thermal-conductivity multilayer ceramic wiring board that eliminates the drawbacks of the conventional ceramic wiring board described above and has a conductor inside a thermally conductive soaked interior. Arrangement of the Invention) According to the present invention, there is provided a high thermal conductivity multilayer ceramic wiring board in which the ceramic structure is composed of a polycrystalline body mainly composed of aluminum nitride, and the conductor layer is mainly composed of metal carbide. 0 (Detailed Description of Configuration) The present invention has solved the problems of the prior art by adopting the above-mentioned configuration.

First, aluminum nitride, which has high thermal conductivity, was used as the insulating ceramic material constituting the multilayer ceramic substrate. After firing, this material forms a dense structure of polycrystalline aluminum nitride.In order to obtain high thermal conductivity, the sintered body θ
] It is preferable to have a small amount of acid residue, and therefore it is preferable to add a reducing agent with a reducing effect as an additive.Next, regarding the threat to the conductor, it is preferable to add a reducing agent with a reducing effect as an additive. power layer.

Conductor layers such as a ground layer and fine signal lines are formed, and these multiple conductor layers are electrically connected via peer holes provided in the ceramic layer. Therefore, the wiring density of the mounting board is extremely high. At the same time, it becomes possible to efficiently dissipate heat generated from elements such as LSIs 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 wiring board according to the present invention. 02 is a conductor layer for signal lines, power supplies, etc., which is mainly composed of metal carbide, and is composed of polycrystalline aluminum nitride as a main component. Each layer is electrically connected through the formed peer hole 3. 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 so that a signal can be taken out from the mounting board or input into the board. An input/output pad 6 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. Ceramic substrate 0] Due to its high thermal conductivity) heat diffusion is carried out efficiently, and L S
It is possible to prevent the I-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 is added as an additive to improve the sinterability of aluminum nitride.
Contains aC2. First, aluminum nitride powder and Ca self-powder were weighed and wet mixed in an organic solvent using a ball mill for 48 hours.

This mixed powder is dispersed in a solvent with an organic binder that easily decomposes in a neutral atmosphere, such as polycaprolactone or polyacrylate resin, and the viscosity is 3000-70.
Creates a slurry in the range of 00 cp. A green sheet is formed on an organic film using the slurry casting method so as to have a uniform thickness of about 10 μm to 200 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 using other methods such as laser processing. A conductive paste mainly composed of a compound that becomes metal carbide when fired in a neutral or reducing atmosphere is applied to a predetermined size using a screen printing method.
Print the pattern.

A desired number of 81 tons of green sheets printed with conductors are layered and hot pressed. After that, cut it into the required shape using a cutter and heat it at 1400°C to 2000°C.
During firing, the binder was sufficiently removed at a temperature of 400° C. to 600° C. (U) during the heating process. Table 1 shows the composition of the conductor paste used in the prepared samples, and Table 2 shows the characteristics of the samples.

HfC, NbC, TaC as conductor paste materials.

'! 'A for 'iC, UC, VC and ZrC'ji-
7to The amount of ηx7IO compound (CaC2) 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 8 of the created substrate, the specific resistance was 1.
00.The dielectric constant is 8.7 (1% 1Hz).
, the dielectric loss was 1X10 or more (FCI MHz), and Tl (the air-bacteria properties were also at least the same level as the conventional board, indicating that it would be sufficient as a mounting board).

On the other hand, as additions, Cab, Bed, Y, O,, C
ub, Ago.

BaC2, SrC, , Na2C2, K2C2, CuC,
,MgC,,Ag,C,.

Aluminum nitride 0 even when using ZrC2 etc.
] The effect of improving sinterability was obtained.

(Effects of the Invention) As is clear from the examples, according to the present invention, it is possible to easily form a heavy-duty circuit having conductors including signal lines and a conductor layer, etc., and the heat dissipation property is improved. -C also provides a very effective fL-tube thermally conductive multilayer sesmic substrate.

The thermal conductivity of the conventionally used alumina substrate is 17W,
It can be seen 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 65×10 7° C., whereas the substrate of the present invention has a small value, which is advantageous because it is closer to the thermal expansion coefficient 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. 1... Insulating ceramic layer %2... Conductor layer, 3...
Beer hole k, 4... die pad, 5...-ponding pad, 6... input/output pad.

Claims (2)

[Claims] (1) A multilayer ceramic wiring board formed three-dimensionally inside a conductive ceramic structure, characterized by comprising a ceramic layer mainly composed of aluminum nitride and a conductor mainly composed of metal carbide. Multilayer ceramic wiring board. (2) Claim 1, wherein the metal carbide is one or a mixture of two or more selected from zirconium carbide, tantalum carbide, niobium carbide, vanadium carbide, uranium carbide, hafnium carbide, and titanium carbide. multilayer ceramic wiring board.