JPH0320916B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 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 multifunctionality have become stronger year by year, and in order to meet these demands, high-density mounting of circuit components has become an important technology. It's coming. In particular, the miniaturization of circuits is progressing rapidly with the development of ICs, LSIs, and chip components. To achieve high-density mounting of components, it is necessary to mount as many components as possible within a limited area, and to achieve this, it is necessary to reduce the size of the components and increase the effective area of the board on which the components are mounted. In order to increase the effective mounting area of components, it is necessary to increase the density of wiring formed on the board. In recent years, as mentioned above, there has been great progress in small parts, as seen in ICs, LSIs, and chip parts. On the other hand, methods for increasing the wiring density include making the wiring sufficiently fine-lined or making the wiring a multilayer structure.
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 include those based on organic resin and those based on ceramic. Among these, resin-based ones, as shown in Figure 1, conductor connections between the 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 conductor layers, the number of through holes also increases, and the effective mounting area for component mounting becomes smaller. As the mounting density of components increases, if heat is generated from the components themselves, the thermal conductivity of the resin is low, resulting in poor heat dissipation. When the component is, for example, a silicon semiconductor chip and it is attempted to be directly attached to a substrate, the difference in thermal expansion coefficients between silicon and organic resin is too large, making it difficult to attach the semiconductor chip directly to the resin substrate from the viewpoint of reliability. Due to these problems, resin substrates cannot cope with high packaging density. On the other hand, in a multilayer board configuration using ceramics, the second
As shown in the figure, conductor connections (vias) between layers can be formed inside the board, ceramic has a much higher thermal conductivity than resin, so it has excellent heat dissipation, and it has a small coefficient of thermal expansion. Since it has a thermal expansion coefficient close to that of silicon, it has the advantage of allowing direct attachment of chips, and has extremely excellent properties as a substrate for high-density packaging. Conventional ceramic multilayer substrates can be roughly divided into two configurations. One method is to alternately print gold or silver-palladium conductor paste and glass insulation paste on a sintered ceramic substrate (e.g. alumina substrate).
This is a method of repeating firing to create multiple layers. 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 with this configuration is limited to extremely limited fields such as industrial equipment.
The reality is that there are no examples of its application to consumer devices. 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 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 1600°C in a reducing atmosphere. In this method, since the materials are laminated and multilayered in an unsintered state, multilayering 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 extremely high temperatures, which requires large-scale equipment, and it is not possible to solder directly to tungsten or molybdenum, so in practice, nickel or gold plating is applied to the surface of the tungsten or molybdenum conductor layer. There are problems such as the need to perform As mentioned above, in recent years, parts have become smaller year by year,
Currently, these small components are widely 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, the current multilayer board technology has the above-mentioned problems and has not been widely used. 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 ceramic multilayer substrate of the present invention is produced by applying iron oxide, nickel oxide, cobalt oxide, or a mixed powder thereof to a sintered substrate mainly composed of alumina using an organic binder and an organic solvent. It does not oxidize the paste and iron, nickel, cobalt, or their alloys, which are mixed together with the vehicle.
A paste made by kneading glass powder or powder consisting of glass powder and alumina powder, which is sintered at a temperature lower than the melting point of iron, nickel, and cobalt, with a vehicle consisting of an organic binder and an organic solvent is alternately printed and dried repeatedly. A process in which the substrate obtained in that process is heat-treated in air at a temperature that does not cause the insulating layer to start sintering to burn off the organic binder, and a process in which the substrate obtained in that process is heat-treated in a reducing atmosphere to form iron oxide. , a process of reducing nickel oxide, cobalt oxide, or a mixed powder of these to metal, and firing the substrate obtained in this process at a temperature lower than the melting point of iron, nickel, or cobalt to form a glass or a mixed phase of glass and alumina. This manufacturing process consists of a step of densifying the metal, and this makes it possible to manufacture extremely low-cost ceramic multilayer plates using iron, nickel, or cobalt. Description of Examples Each step of the present invention will be described in detail below. In the present invention, iron oxide, nickel oxide, and cobalt oxide are used as the starting materials for conductors of iron, nickel, and cobalt, and the insulating material is sintered at a temperature below the melting point of iron, nickel, and cobalt. Or use glass or a mixture of glass and alumina that does not oxidize cobalt. The most typical iron oxide is Fe ₂ O ₃ (red iron), NiO for nickel, and CoO for cobalt, but of course oxides with other valences may be used. Examples of insulating materials include BaO,
There are glasses composed of components such as B ₂ O ₃ , CaO, MgO, Al ₂ O ₃ , and SiO ₂ . These components are thermodynamically stable enough to not oxidize the metals iron, nickel, and cobalt. Conductive powder and insulating material powder made of such components are kneaded with a vehicle made of an organic binder and an organic solvent to form a paste. This paste is screen printed on a sintered alumina substrate in a predetermined pattern, and then dried, and then an insulating paste is printed on top of this and dried. If necessary, this process is repeated to form layers. then this
Heat treated in air at 600℃~800℃. This step is a step to completely dissipate the organic binder in the paste. An organic binder is usually a polymer composed of carbon and hydrogen, and when it is heat-treated in a neutral atmosphere or a reducing atmosphere, carbon remains at the end and is difficult to completely dissipate. When a green ceramic containing an organic binder is sintered in an oxygen-free system, the most important problem in sintering technology is often to completely dissipate the organic binder. On the other hand, in the present invention, a printed and laminated paste containing an organic binder is heat-treated in air, so a sufficiently large amount of oxygen exists in the atmosphere. Therefore, the organic binder is dispersed, and even if carbon remains at the end, it is burned by the oxygen in the surrounding atmosphere and becomes a gas called CO or CO ₂ , and the organic binder is completely dissipated to the outside. In this in-air heat treatment process, the conductor iron oxide, nickel oxide, or cobalt oxide and the insulating layer are layered alternately and are in contact with each other, but the temperature is not yet high enough, so the gap between these conductor oxides and the insulating layer is Only a minimal amount of interdiffusion occurs. If interdiffusion occurs completely in this temperature range, it would be inconvenient from a structural standpoint, and therefore it is necessary to select a material for the insulating layer that is difficult to interdiffuse with the conductor oxide. After completely dissipating the organic binder in this manner, it is heat treated at 700 to 900°C in a reducing atmosphere. The key point of this process is to reduce the oxide portion of the conductive material to metal. In this step, it is necessary for the reducing gas to sufficiently diffuse into the laminated portion, so it is important to prevent the laminated portion from becoming dense. In addition, it is of course undesirable for the insulating layer components to contain components that are easily reduced, and if such components are included, they may cause poor insulation of the insulating layer or re-oxidize the conductor parts that have been reduced. lead to phenomena. The reducing atmosphere is generally hydrogen or a mixed gas of hydrogen and nitrogen. Next, while maintaining a reducing atmosphere to the extent that the reduced metal is not oxidized, the temperature is raised to sinter and densify the metal layer and the insulating layer. During the densification process, the adhesion between the metal and the insulating layer is ensured, and the insulating layer and metal are laminated to obtain a multilayer integrated structure. Specific examples of the present invention will be described below. Example: 10w of iron oxide (α-Fe ₂ O ₃ ) powder and turpentine oil
% of ethylcellulose was kneaded with a three-stage roll to form a conductive paste. Further, the above vehicle was kneaded with powder of glass #7070 manufactured by Corning Co., Ltd. and alumina (AL-30) manufactured by Showa Denko Corporation in a weight ratio of 50/50 to form an insulating paste. The above conductive paste was printed in a predetermined pattern on a sintered 96% alumina substrate and dried. Furthermore, the above insulation paste was printed on this and dried. Small holes (vias) are provided at predetermined locations on this insulating layer for the purpose of connecting the conductor layer formed thereon and the lower conductor layer. A conductor layer was further printed in a predetermined pattern on the insulating layer and dried. This laminate was heat treated in air at 700°C for 30 minutes. Further, this laminate was heat-treated at 850° C. in a mixed gas of 10% H ₂ and 90% N ₂ for 30 minutes. Next, this was heat treated at 1200° C. for 1 hour in a 1% H ₂ -99% N ₂ mixed gas atmosphere. The thus obtained laminate had a monolithic structure, and the iron was a complete metal layer, and electrical continuity was obtained between the uppermost iron layer and the lower iron layer. Typical characteristics of the laminate thus obtained are shown below.

[Table] Multilayer substrates with nickel or cobalt conductors also use nickel oxide (NiO) and cobalt oxide (CoO) powders as conductor material raw materials and are kneaded with a vehicle to form a conductor paste. This was printed, dried, baked in air, heat treated in a reducing atmosphere, and heat treated at high temperature using the same insulating paste as for iron and the same procedures and conditions to create a laminate. In these cases, as in the case of iron, the metal layer and the insulating layer had an integral structure, and electrical continuity was obtained between the uppermost conductor layer and the lower conductor layer. The properties of these two materials were approximately the same, with an insulating layer resistance of >10 ¹² Ω, a conductor resistance of 7 to 9 mΩ/2, and an adhesive strength of 0.8 to 1.1 Kg/mm ² . In the above example, the number of layers was two conductor layers, but
The number of layers is not limited to two, but can be increased by repeating printing and drying. Effects of the Invention As is clear from the above description, the present invention involves alternately printing and drying a metal oxide conductive material paste and an insulating paste on an alumina sintered substrate, performing a binder removal heat treatment process in the air, and reducing the metal oxide. It consists of heat treatment, metal, and insulating layer sintering and densification processes, and the following effects can be obtained. (1) Since base metals such as iron, nickel, and cobalt are used as conductor materials, an extremely low-cost multilayer board can be obtained. (2) Since metal oxide is used for the conductor material during printing, the binder can be removed in the air, making it easy and complete to remove the binder and leaving the metal layer and insulating layer in a sintered state. Gives good results. (3) Sintering is performed in a completely reducing atmosphere, so
Excellent effects such as easy condition setting without the need for delicate atmosphere control can be obtained. As a result, multilayer boards can be manufactured at low cost and easily, providing low-cost, high-density mounting circuit modules, greatly contributing to the expansion of equipment miniaturization and multifunctionality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a resin multilayer board, and FIG. 2 is a sectional view of a ceramic multilayer wiring board. 1...Surface conductor, 2...Through-hole inner wall conductor,
3...Inner conductor, 4...Resin insulator, 5...Surface conductor, 6...Inner conductor, 7...Ceramic insulator.

Claims (1)

[Claims] 1 A paste prepared by kneading iron oxide, nickel oxide, cobalt oxide, or a mixed powder of these together with a vehicle consisting of an organic binder and an organic solvent, and iron, nickel, cobalt, or an alloy of these are placed on a sintered substrate mainly composed of alumina. without oxidizing, and iron,
A process of alternately printing and drying a paste made by kneading glass powder or powder consisting of glass powder and alumina powder, which is sintered at a temperature lower than the melting point of nickel or cobalt, with a vehicle consisting of an organic binder and an organic solvent. , a step in which the substrate obtained in that step is heat-treated in air at a temperature at which the insulating layer does not begin to sinter to burn off the organic binder, and a step in which the substrate obtained in that step is heat-treated in a reducing atmosphere to remove iron oxide,
A process of reducing nickel oxide, cobalt oxide, or a mixed powder thereof to metal, and firing the substrate obtained in this process at a temperature lower than the melting point of iron, nickel, or cobalt to form glass or a mixed phase of glass and alumina and metal. A method for manufacturing a ceramic multilayer wiring board, which comprises a step of densifying a ceramic multilayer wiring board.