JPS6164189A - Method of producing ceramic multilayer circuit 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 Field of the Invention The present invention relates to a ceramic multilayer wiring board that can be used as a board for high-density mounting of circuits including ICs, LSIs, chip components, etc., and a method for manufacturing the same.

Conventional configurations and their problems In recent years, demands for smaller devices and more multi-functionality have become stronger over the years, and in order to meet these demands, high-density mounting of circuit components has become an important technology. ing. In particular, I
With the development of C, LSI and chip components, the miniaturization of circuits is progressing rapidly.

In order to achieve high-density mounting of components, it is necessary to mount as many components as possible within a limited area.To do this, it is necessary to make the components smaller and to increase the effective area of the board on which the components are mounted. be. In order to increase the effective mounting area of components, it is necessary to increase the density of the wiring formed on the substrate.In recent years, as mentioned above, advances in small components have been seen in IC, LSI, and chip components. On the other hand, one way to increase the wiring density is to make the wiring sufficiently fine.
There are two methods: a line or a multilayer wiring structure.

Creating fine-line wiring requires advanced printing or etching techniques, but even then there are limits to the extent to which they can be achieved. The most effective way to increase wiring density is to use multiple layers of wiring.

Conventionally, substrates for mounting components having a multilayer structure are typified by those based on organic resin and those based on ceramic. Among these, resin-based ones (1) As shown in Figure 1, conductor connections between conductor layers inside the board are made by providing through holes on the front and back of the board and plating the inner walls of these through holes. When there are many connection points between the inner conductor layers, the number of through holes also increases, and the effective mounting area for component mounting becomes smaller.

(2) As the mounting density of parts increases, if heat is generated from the parts themselves, the heat dissipation is poor because the thermal conductivity of the resin is low.

(3) If the component is, for example, a silicon semiconductor chip and you try to attach it directly to a substrate, the difference in thermal expansion coefficients between silicon and organic resin is too large, so it is difficult to attach the semiconductor chip directly to a resin substrate from a reliability standpoint. .

Due to these problems, resin substrates cannot cope with high mounting density.

On the other hand, as shown in Figure 2, in a multilayer board configuration made of ceramic, conductor connections (piers) between the eyebrows can be formed inside the board, and the thermal conductivity of ceramic is much higher than that of resin, so it has excellent heat dissipation. -Furthermore, it has a small coefficient of thermal expansion close to that of silicon, so it has the advantage of being able to directly attach chips, making it extremely suitable as a substrate for high-density packaging. Conventional ceramic multilayer substrates can be roughly divided into two configurations.

One of the seven methods is to alternately print gold or silver-palladium conductive paste and glass insulating paste on a sintered ceramic substrate (for example, an alumina substrate) and repeat firing to create a multilayer structure. With this method, vias can be formed inside the board, increasing the effective area for mounting components, making it suitable for high-density mounting boards. However, this configuration uses a noble metal such as gold or silver-palladium as the conductor material, making it expensive. As a result, the use of ceramic multilayer substrates having this configuration is limited to extremely limited fields such as industrial equipment, and the reality is that there are no examples of application to consumer equipment. Another example of a multilayer board using ceramic is to print tungsten or molybdenum conductive paste on a green sheet made of inorganic powder mainly composed of alumina and an organic binder, and then print multiple sheets of these sheets after drying. This is a method in which the layers are laminated by heating and pressure bonding, and then sintered at a high temperature of 1500 to 160° C. in a reducing atmosphere. In this method, the layers are laminated in an unsintered state.

Since it is multi-layered, multi-layering is extremely easy. Furthermore, since it is composed of alumina, tungsten, and molybdenum, it exhibits extremely high stability and has the advantage of low material cost. However, this configuration requires high temperatures, which requires large-scale equipment, and it is not possible to solder directly to tungsten or molybdenum, so nickel is actually used on the surface of the tungsten or molybdenum conductor layer.

There are problems such as the need for gold plating.

As mentioned above, in recent years, parts have become smaller year by year, and the current situation is that these small parts are often used not only in industrial equipment but also in consumer equipment. On the other hand, not only in the field of industrial use but also in the field of consumer equipment, devices are becoming more multi-functional and smaller, and multi-layered boards are desired for component mounting boards as well. However, current multilayer board technology has the above-mentioned problems and has not been widely used.
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OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide a method for manufacturing a ceramic multilayer board that is low cost and enables high-density mounting of components.

Structure of the Invention In order to achieve the above object, the present invention provides a method of manufacturing a glass powder or glass and aluminum powder that is sintered at a temperature lower than the melting point of iron, nickel, cobalt, or an alloy thereof, an organic binder, and a plasticizer. A paste obtained by kneading iron oxide, nickel oxide, cobalt oxide, or a mixed powder thereof with a vehicle consisting of an organic binder and an organic solvent is printed on the green sheet and on the inner walls of the small holes for through holes provided in the green sheet. A process of forming a patterned film, a process of laminating and laminating a plurality of the printed green sheets by heating and pressure, and a process of laminating the printed green sheets by heating and applying air at a temperature that does not cause the glass or a mixture of glass and alumina to begin to sinter. a process of heat treatment in a reducing atmosphere to burn the organic binder; a process of heat treatment in a reducing atmosphere to reduce iron oxide, nickel oxide, cobalt oxide, or a mixed powder of these to metal; The manufacturing process consists of firing at a temperature lower than the melting point and densifying the glass or glass/alumina mixed phase and metal.This process makes it possible to produce extremely low-cost ceramic multilayer substrates using iron, nickel, or cobalt. This makes it possible to manufacture

Description of examples Each step of the present invention will be explained in detail below.

In the present invention, iron oxide and nickel oxide are used as starting materials for conductors of iron, nickel, and cobalt, respectively.

Cobalt oxide is used, and iron is used as the insulating material.

Sintered below the melting point of nickel, cobalt, and iron.

Use glass or a mixture of glass and alumina that does not oxidize nickel or cobalt. The iron oxide of the conductor raw material is F.
The most typical example is e2O2 (red iron), NiO for nickel, and Coo for cobalt, but of course oxides with other valences may be used. Examples of the insulating material include BaO.

BaO5, CaO, MgO, Mu120s, 5iOz
There are glasses composed of such components and mixtures of this and alumina. Components such as these are thermodynamically stable enough to not oxidize metals such as iron, nickel, and cobalt. First, glass powder or a mixture of glass powder and alumina powder as described above is kneaded with an organic solvent such as toluene and an organic binder such as polyvinyl pteral to form an ink-like mixture (generally referred to as slip) and a doctor blade film. Run it through a machine and dry it to make green sheets.

Further, iron oxide, nickel oxide, cobalt oxide, or a mixture thereof is kneaded with a vehicle consisting of an organic binder and an organic solvent to form a paste. This base p is printed on the green sheet and dried.

In this case, the green sheet has small holes for peer holes, and the paste is filled into these small holes at the same time when printing the paste. A plurality of green sheets printed in this way are laminated and integrated using heat and pressure. Here, since a thermoplastic binder such as polyvinyl butyral is used for the green sheet, these can be bonded and integrated using heat and pressure. Next, add this to 6
Heat treatment at 00 to 80°C in air. This step is a step to completely dissipate the organic binder in the paste. Organic binders are usually polymers mainly composed of carbon and hydrogen, and when they are heat-treated in a neutral or reducing atmosphere, carbon remains at the end and is difficult to completely dissipate. be. When sintering green ceramic containing an organic binder in an oxygen-free system,
Complete dissipation of organic binders is often a problem in sintering technology. In the present invention, since the green sheet and paste containing the organic binder' are heat-treated in air, a sufficiently large amount of oxygen is present in the surrounding atmosphere. Therefore, even if the organic binder is decomposed and carbon remains at the end, it is burned by oxygen and becomes CO or COz gas, which is completely dissipated to the outside. Of course, since it is necessary for oxygen to enter the interior, it is inconvenient for this system to start sintering due to the reaction between the binder and oxygen. , layers of nickel oxide or cobalt oxide and insulating layers are laminated alternately and are in contact with each other, but the temperature is still high enough that there is no bond between the oxide and the insulating layer, which will serve as the conductor layer. A very small amount of interdiffusion layer is formed, but they do not mix with each other.

After the organic binder is completely purified in this way, it is heat-treated at 700 to 900° C. in a reducing atmosphere. The point of this process is to reduce the conductive material oxide layer to metal. In this step, the reducing gas needs to sufficiently diffuse into the laminated portion, so it is important that the entire layer does not become dense.

Also, of course, it is undesirable for components that are easily reduced to be included in the insulating layer components.If such components are included, insulation defects may occur in the insulating layer, and the reduced conductor may The reducing atmosphere is generally hydrogen or a mixture of hydrogen and nitrogen.Next, a reducing atmosphere is maintained to the extent that the reduced metal is not oxidized, and the temperature is raised to remove the metal. The layer and the insulating layer are sintered and densified.During the densification process, the adhesion between the metal and the insulating layer is ensured, and the insulating layer and the metal layer are laminated and integrated.

Specific examples of the present invention will be described below.

2 kg of mixed powder of Corning glass #7070 powder and alumina powder in a weight ratio of 1:1, and 0.7 kg of an organic solvent of toluene and inpropyl alcohol in a weight ratio of 1:1.
kg, plasticizer 0.09 kg, polyvinyl bral o,
1 ekg was mixed in a ball mill, and after defoaming, a film was formed using a doctor blade and dried to create a green sheet with a thickness of 200 μm. Next, a vehicle containing iron oxide (α-Fezes) powder and 1% ethyl cellulose dissolved in turpentine oil was kneaded with a three-stage roll to form a conductive paste. Next, the green sheet was cut to a predetermined size and small holes were punched in the necessary places, and then 250 meshes of the above conductor paste was printed using a stainless steel screen with a thickness of 10 μm and dried. At the time of screen printing, small holes for vias were also filled with conductive paste. Next, stack the three sheets printed as above,
Lamination was carried out at a temperature of 0°C and a pressure of 20°C. The thus obtained laminate was heat treated in air at 700°C for 60 minutes. Furthermore, this laminate was heated at 850°C and 10% H2-9.
Heat treatment was performed for 30 minutes in a 0% N2 mixed gas. Next, this was heated for 1200' in a 1% 12-99% N2 mixed gas atmosphere.
C, heat treated for 1 hour. The laminate thus obtained had a dense structure, the iron was a complete metal layer, and electrical continuity was obtained between the top iron layer and the inner iron layer. Typical characteristics of the thus obtained laminate as a wiring board are shown below.

In the case of surface nickel conductors or cobalt conductors, nickel oxide (NiO) and cobalt oxide (Co) are used as conductor material raw materials.
The powder of (o) was used and kneaded with a vehicle to form a conductor paste. This is printed on a green sheet as in the case of iron,
It was dried and laminated.

Furthermore, heat treatment was performed in air and reduction treatment under the same conditions.

A dense monolithic structure was obtained by reduction and high temperature treatment. The characteristics of these two wiring boards were approximately the same, with an interlayer insulation resistance of 1012Ω, a conductor resistance of 7 to 9rrLΩ, and an adhesive strength of 1.0 to 1.5 kgAn7j. In the above embodiment, the number of conductor layers is three, but the number of layers is not limited to three and can be any number of layers.

Effects of the Invention As is clear from the above explanation, the present invention involves printing a paste made by kneading iron, nickel or cobalt oxide powder and a vehicle on a green sheet made of glass or glass, alumina and an organic binder, and , a laminate made by laminating a plurality of these sheets under pressure is subjected to an in-air heat treatment to remove the binder, a heat treatment to reduce metal and metal oxides, and an insulating layer sintering and densification process, which has the following effects. can get.

(1) Using a metal oxide as a starting material as a conductor material (
Green sheet: The organic binder contained in the conductor paste can be removed in the air, making it possible to achieve an extremely densified state.

(2) Since base metals such as iron, nickel, and cobalt are used as conductor materials, extremely low-cost multilayer substrates can be obtained.

(3) Since sintering is performed in a completely reducing atmosphere, excellent effects such as easy condition setting without requiring delicate atmosphere control can be obtained.

As a result, the multilayer board can be manufactured at low cost and easily, providing a low-cost, high-density mounting circuit module, which greatly contributes to the miniaturization and multifunctionality of equipment.

[Brief explanation of the drawing]

1...Surface conductor, 2...Through hole inner wall conductor, 3...Inner conductor, 4...Resin insulator, 6...Surface Conductor, 6... Internal conductor, 7... Ceramic insulator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] (1) For through-holes on and on green sheets made of glass powder or glass powder, alumina powder, organic binder, and plasticizer sintered at a temperature lower than the melting point of iron, nickel, cobalt, or their alloys. A step of printing a paste obtained by kneading iron oxide, nickel oxide, cobalt oxide, or a mixed powder thereof with a vehicle consisting of an organic binder and an organic solvent on the inner wall of the small hole to form a pattern film, and the above printing. A process of laminating and laminating a plurality of green sheets by heating and pressure, and a process of heat-treating the green sheets in air at a temperature at which the glass or a mixture of glass and alumina does not begin to sinter, and burning the organic binder. , heat-treating this in a reducing atmosphere to reduce iron oxide, nickel oxide, cobalt oxide, or a mixed powder of these to metal, and firing this at a temperature lower than the melting point of iron, nickel, and cobalt to form glass or glass. A method for manufacturing a ceramic multilayer wiring board comprising a mixed phase of alumina and a step of densifying metal.