JPS61292392A - Manufacture of ceramic wiring board - 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] Industrial Application Field The present invention is a device equipped with an IC, an LSI, a chip component, etc.
The present invention also relates to a method of manufacturing a ceramic wiring board with high heat dissipation that can be used as a board for high-density mounting of interconnected circuits.

BACKGROUND OF THE INVENTION Today, there is an extremely high demand for smaller size, lighter weight, higher speed, and higher axial power in not only computers and communication equipment but also consumer equipment. The semiconductors used in these devices are rapidly progressing toward higher chip integration, multi-chip modularization, and higher output. Correspondingly, how to deal with the increasing heat generation of elements has become a major problem for substrates on which semiconductors are mounted.

Conventionally, BeO substrates, hollow substrates, and metal core substrates have been commonly used as substrates with high heat dissipation properties. However, although BeO is a material with a thermal conductivity more than 10 times that of alumina, it is toxic and has limited applications.
Furthermore, it has the problem of being expensive.

Next, the enamel board is made by coating the surface of a low carbon steel plate with enamel and forming a wiring pattern with conductive paste on top of it, but since the melting point of enamel is low, the firing temperature is 550~550℃. The current situation is that there is no conductive paste that has sufficient electrical characteristics when burned at such a low temperature of 600°C. Furthermore, there are other problems, such as the raised areas around the substrate and through-holes, making it difficult to print in these areas, migration of alkali metal ions contained in the enamel, and small cost benefits. .

Finally, the metal core substrate is produced by coating the surface of an Fe plate with epoxy resin, pasting Cu foil thereon, and then forming a wiring pattern by etching. However, since epoxy resin is used, it has low heat resistance, and there are problems with waste disposal due to the use of etching liquid.Furthermore, although double-sided mounting is possible via through holes, multilayer wiring structure is required on one side. The problem is that it cannot be taken.

Therefore, as shown in Figure 6, a Cu green sheet made of Co powder and an organic binder is used as a substrate, and glass and
A paste made of an insulator such as ceramic and an organic binder is screen printed to form an insulating layer, and then a Cu paste made of Co powder and an organic binder is screen printed on top of this to form a Cu circuit pattern. A method of firing was proposed.

(Literature name, for example, Japanese Patent Application Laid-Open No. 107295/1983)
This method allows firing at a temperature of around 900°C.
It is now possible to use conductor paste for alumina substrates.

Problems to be Solved by the Invention However, using the method disclosed in Japanese Patent Application Laid-Open No. 55-107295, there are major problems in the manufacturing process. It can be used for Cu green sheet, insulating paste and C
This means that the organic components in the u-paste are not completely removed by combustion. For this purpose, firing must be carried out in an atmosphere containing N2 and 02, but it is extremely important to control the oxygen partial pressure in the furnace to a level that does not oxidize the Cu and allows the organic components to be completely burned off. It is difficult to If the oxygen partial pressure is high, the Cu surface will be oxidized, resulting in poor soldering properties and a decrease in electrical conductivity. Conversely, if the oxygen partial pressure is too low, the organic components will not be completely burned off as described above. It is said that organic binders do not decompose especially at temperatures below the melting point of Cu. (
(Literature (for example, Japanese Unexamined Patent Publication No. 55-128899)) Further, due to the remaining organic components, there are problems such as poor adhesion of metallization and poor heat dissipation.

In addition, when using metal Cu, even if the binder removal process and the Cu baking process are separated, the metal Cu is oxidized in the binder removal process, causing volumetric expansion, and is further reduced during firing to become metal Cu. There is a problem that the conductor layer may peel off due to the change in volume due to returning to its original state.

Means for Solving the Problems In order to solve the above-mentioned problems, in the method for manufacturing a ceramic wiring board of the present invention, the binder removal temperature, the reduction process, and the firing process are performed separately.

The binder was removed in an atmosphere sufficiently oxidizing to carbon. As a result, the atmosphere can be controlled extremely easily, and the organic components in the green sheet, insulating paste, and conductive paste can be completely burned off. Therefore, if a base metal such as Cu is used as the inorganic component of the green sheet and conductive paste as in the conventional example, metal oxides (such as Cu
→Cub), and the volume change causes peeling of the conductor layer. Therefore, Cub, Few 03 , and C00% NiO, which are stable in a sufficiently oxidizing atmosphere with respect to carbon within the temperature range from room temperature to the debinding temperature, were used as the inorganic components of the green sheet and the conductive paste.

Note that the structure of the ceramic wiring board of the present invention is Cub;
An insulating paste made of glass or glass-ceramic and a conductive paste made of the metal oxide are applied to a desired number of layers by a thick film printing method on a green sheet made of Fezoff, CooSNiO, etc. and an organic component.
It is printed and laminated. After removing the binder, the ceramic wiring board having the above structure was heated with N2 +H at a temperature below the glass softening point.

The material is reduced in an atmosphere, and then fired and sintered in an N2 atmosphere.

Function As described above, the present invention is characterized in that the binder removal temperature, the reduction process,
Since the firing process is performed separately, it is possible to completely remove organic components, which is the biggest problem in producing ceramic wiring boards using base metal as a conductor layer.

Furthermore, since base metal oxides are used as the inorganic components of the green sheets and conductor pastes, there is no need to worry about volume changes due to changes from metals to metal oxides, unlike when base metals are used. Although various metal oxides can be used, it is desirable to use one that does not cause volume change (for example, due to contraction, expansion, crystal transformation), sublimation, unnecessary diffusion, etc. in the temperature range from room temperature to the debinding temperature. ,
Materials such as WO2 and Mo01, which sublimate when heat treated in an oxidizing atmosphere, are unsuitable.

Therefore, Cub and Fez are stable even at debinding temperatures.
03, Coo, and NiO are suitable as inorganic components for green sheets and conductive pastes.

In addition, it is possible to combine the above oxides, but CO5Fe, Co, and Ni can be mixed together,
Even when alloyed, there are few cases in which the melting point is lowered, and even if it is lowered, it is only a small amount, so it is clear that an inorganic component mixed with an oxide is also effective. Furthermore, it is also effective to use different metal oxides for the green sheet and conductive paste. For example, regardless of the metal oxide used for the green sheet, if CuO1NiO is used as the upper layer conductor paste, a ceramic wiring board that can be directly soldered can be produced.

Note that the binder removal is performed at a temperature below the softening point of glass, which is an inorganic component of the insulating paste. This is because, if the temperature is higher than the softening point, the metal oxide is sealed inside the insulating layer.1. Therefore, it is not reduced to metal even in the reduction process, and the conductor resistance becomes infinite. Furthermore, unnecessary diffusion may occur, resulting in problems such as deterioration of insulation properties.

Next is the reduction step, which also needs to be carried out at a temperature below the softening point of the glass to prevent metal oxides from being trapped in the insulating layer. The inorganic component of the insulating paste should preferably be chemically inert with base metals and thermodynamically stable, such as PbO.
Those that become PB upon reduction are unsuitable.

Finally, the firing step is carried out in N2 atmosphere.

By doing so, a ceramic wiring board with very good metallization properties can be produced. If it is carried out in a reducing atmosphere, the twisting between the conductive layer and the insulating layer will be poor and good metallization properties will not be obtained.

Example (Example 1) To 100 parts of commercially available CuO powder, 10 parts of polyvinyl butyral as a binder, 8 parts of dibutyl phthalate as a plasticizer, and 50 parts of isopropyl alcohol as a solvent were added to form a slurry. Knead and then
A film was formed using a doctor blade method and dried to create a green sheet with a thickness of about 1 basket. 2 on this green sheet
The insulation paste was printed using a 00 mesh screen and dried. The insulating paste contains 11kl of borosilicate glass powder (average particle size: approx. 3cm) as an inorganic component.
．． The 0 μm composition is shown in Table 1. ) and alumina powder in a weight ratio of 1:1, a vehicle consisting of turpentine oil and ethyl cellulose was added to this mixed powder, and the mixture was kneaded with three-stage rolls to an appropriate viscosity.

After drying the insulating paste, the same vehicle as that used for the insulating paste was added to CuO, and a conductive paste adjusted to an appropriate viscosity was printed using a 250 mesh screen and dried. After drying, the conductor layer had a thickness of 10 μm or more. A cross-sectional view of the unfired ceramic wiring board after conductor printing is shown in FIG. Next, this dried substrate
Binder removal was carried out at a temperature of about 650°C in an air width. Note that the temperature and atmosphere for this binder removal are determined by conducting a thermal analysis of the organic binder used in air in advance to confirm whether or not the binder is completely removed. Therefore, since the decomposition temperature differs depending on the type of binder, it is natural that the temperature profile during binder removal also differs.

Next, this debinding substrate is heated to Nz + Hz (Hz / Nz =
20/80: Reduction in an atmosphere with a flow rate of 212/min,), and then N2 with the temperature profile shown in Figure 4.
Fired in an atmosphere. As a result, the CuO green sheet and the conductive paste were completely reduced to metal Cu, and furthermore, the organic components were completely burned off, making it possible to produce a dense ceramic wiring board with good heat dissipation properties.

A cross-sectional view of this sintered ceramic wiring board is shown in FIG.

(4 members under 1' Table 1 (Example 2) CuO green sheet produced in Example 1 and CuO
A ceramic wiring board was manufactured in the same manner using NiO instead of CuO as the paste.

However, the inorganic component of the insulating paste is borosilicate glass powder (average particle size, approximately 3.2 μm).
Shown in the table. ) and alumina powder in a weight ratio of 3:7. Further, the firing temperature used a temperature profile as shown in FIG. The ceramic wiring board produced in this way was also made of NiO
was completely reduced to metallic Ni, and furthermore, the organic components were completely burned off, resulting in a compact product with excellent heat dissipation properties.

As described above, in Examples 1 and 2, only one layer of conductive paste was printed, but this could be done by printing and drying the insulating paste, and then repeating the printing and drying of the conductive paste as many times as desired to create a multilayer structure. Similar results were obtained in this case.

Effects of the Invention As described above, the binder removal process of the present invention can completely remove the organic components in the green sheet, insulating paste, and conductive paste, and also reduces the firing process to N.
By carrying out the process in a 2 atmosphere, a ceramic wiring board with very good metallization properties can be produced. In addition, as starting materials for conductors, Cub, Fez Ox, Coo
Since base metal oxides such as , NiO, etc. are used, the cost can be extremely reduced. Further, since the ceramic wiring board of the present invention includes a metal plate layer, it has extremely good heat dissipation properties, and is an industrially extremely effective invention.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the unfired ceramic wiring board of Example 1, Fig. 2 is a cross-sectional view of the ceramic wiring board after firing of Example 1, and Fig. 3 is the temperature of the reduction step of Example 1. FIG. 4 shows the temperature profile of the firing process of Example 1, FIG. 5 shows the temperature profile of the firing process of Example 2, and FIG. 6 shows the conventional example. 1... CuO green sheet layer, 2...
- Insulating paste layer, 3...CuO paste layer,
4... CuO layer, 5... Insulating layer, 6...
... Cu metallized layer, 7 ... Cu green sheet layer, 8 ... Insulating paste layer, 9 ...
・Cu paste layer. Name of agent: Patent attorney Toshio Nakao (1 person) Figures 1 and 3 Figure 3 Figure 4

Claims (1)

[Claims] A green sheet or insulating paste containing glass or glass-ceramic as an inorganic component, and CuOFe_2
At least one layer of wiring is formed using a conductive paste containing at least one of O_3, CoO, and NiO as an inorganic component on a green sheet containing at least one of CuO, Fe_2O_3, CoO, and NiO as an inorganic component. a step of debinding the unsintered wiring board in an oxidizing atmosphere sufficient for carbon and at a temperature sufficient to thermally decompose the internal organic components; A method for manufacturing a ceramic wiring board, comprising the steps of heat treatment in a reducing atmosphere at a temperature below, and then sintering in a nitrogen atmosphere.