JPH0561799B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method of manufacturing a ceramic multilayer substrate. Conventional technology In recent years, thick film multilayer boards using copper as the conductor material have been put into practical use in many fields because thick film paste is readily available and the manufacturing method itself is simple, making it relatively easy to manufacture. I am trying to do. However, in most cases of this thick film printing method, the conductive layer and the insulating layer are fired in a neutral atmosphere each time after printing, which makes it difficult to remove the binder from the paste, causing blisters in the insulating layer and Leads to sexual deterioration. Additionally, there are drawbacks such as increased equipment costs and longer lead times.
Therefore, a method of using copper oxide as the starting material of the conductor has solved the above-mentioned drawbacks. This makes it possible to easily remove the binder in the atmosphere, eliminating the need to repeat baking each time after printing, and reducing the binder once.
It is only necessary to carry out a continuous process of firing. The manufacturing method of this multilayer board is described in Japanese Patent Application No. 147833/1983,
No. 147832, and the copper oxide paste was patented in 1982.
-23846 and Japanese Patent Application No. 60-140816, respectively. An example of a method for manufacturing a printed multilayer board using the above-mentioned copper oxide will be described below with reference to the drawings. FIG. 4 shows the manufacturing process of a printed multilayer board using copper oxide. An insulating layer is formed by printing a wiring layer with a copper oxide paste on a fired ceramic substrate, and after drying, printing a thick film insulating paste on the ceramic substrate. The copper oxide paste and the insulating paste are laminated and printed a desired number of times to form multiple layers, and then the binder is removed by heat treatment in the air or an oxidizing atmosphere. Then, heat treatment is performed in a reducing atmosphere and a neutral atmosphere to obtain a printed multilayer substrate. Problems to be Solved by the Invention However, when lint is mixed into the thick film printing method, including the method described above, the thickness of the insulating layer formed is very thin, so there is a problem that some shorts may occur between the wiring layers. There is a point. As a solution to the above problem, a method has been adopted to increase the thickness of the insulating layer by repeatedly printing the insulating paste, but this method is complicated, and repeating printing and drying creates an opportunity for lint to get mixed in. It's not a complete solution because it's a lot. Further, as another solution, it is possible to use a metal mask or a low mesh screen mask in order to obtain a thick film thickness with one printing, but this is impractical because the thickness unevenness and pores of the printed film are severe. Another solution is to prevent shorts between wiring layers by using a green sheet lamination method in which a printed multilayer board is obtained by laminating multiple unfired green sheets with wiring conductors printed in advance and then firing them all at once. A method has also been proposed (patent application 1983).
147833, etc.), but this method is not practical because the ceramic substrate itself shrinks by more than 10% due to the sintering reaction, resulting in very large dimensional variations due to warpage of the substrate. In order to solve the above-mentioned problems, the present invention provides an insulating layer with no unevenness in thickness or pores, a smooth surface, and a uniform thickness, so that there is no shortening between wiring layers, and there is no warping of the board, resulting in high dimensional accuracy. A method for manufacturing a ceramic multilayer substrate is provided. Means for Solving the Problems In order to solve the above problems, the present invention provides an unfired wiring layer on a fired ceramic substrate using a copper oxide paste containing copper oxide as a main component. An unfired insulating layer is formed by pasting an insulating layer formed with an insulating paste containing a low-temperature sintered ceramic material as a main component on top, and then adhering an unfired green sheet with a wiring layer made of the copper oxide paste. , heat treatment is performed in air or an oxidizing atmosphere at a temperature sufficient to decompose the organic components in the green sheet, and then in a reducing atmosphere at a temperature below the temperature at which the green sheet sinters and the copper oxide becomes a metal. A sintered insulating layer is obtained by performing heat treatment at a temperature higher than that at which it is reduced to copper, and then firing at a temperature lower than the melting point of copper in an atmosphere that is non-oxidizing to copper. Function As described above, the present invention provides a wiring layer formed of a copper oxide paste on a fired ceramic substrate with a wiring layer formed of a copper oxide paste, after an insulating layer formed of an insulating paste containing a low-temperature sintered ceramic material as a main component. By thermally bonding unfired green sheets with a wiring layer made of paste, a dense insulating layer with a smooth surface and uniform thickness is formed without unevenness or pores, making it possible to create a dense insulating layer with a uniform thickness, making it easier to use than conventional thick film printing methods. This eliminates the occurrence of shorts between wiring layers, which is the biggest problem in producing ceramic multilayer substrates, and uses a sintered ceramic substrate as the base instead of the green sheet that is the base in the green sheet lamination method. , a substrate with high dimensional accuracy without substrate warpage can be obtained. In addition, since the fired ceramic substrate and unfired green sheet are bonded via the insulating paste, which is mainly composed of low-temperature sintered ceramic material, without the need for heat or pressure, even in the case of highly laminated multilayer boards, the heat to the insulating paste is reduced. The ceramic sintered substrate and the green sheet can be reliably bonded without any problem with the effectiveness of pressure or pressure. Embodiments Hereinafter, a method for manufacturing a ceramic multilayer substrate according to an embodiment of the present invention will be described with reference to the drawings. 1 and 3 are manufacturing process diagrams of a ceramic multilayer substrate according to an embodiment of the present invention, and FIGS. 2a and 2b are
is a sectional view of the same ceramic multilayer substrate. First, a wiring layer 2 is screen printed in advance using copper oxide paste on an alumina fired substrate 1 and dried. Next, a wiring layer 2 is printed using the copper oxide paste on unfired green sheets 4 of different thicknesses with holes drilled at desired locations and dried. An insulating paste is printed on the alumina fired substrate 1 to form a thin unfired insulating layer 3, and before the unfired insulating layer 3 dries, the unfired green sheet 4 is stacked on top of the alumina fired substrate 1 and unfired green. Sheet 4 was adhered. The unfired green sheet 4 was obtained by kneading glass ceramic powder consisting of borosilicate glass powder and alumina powder with an organic binder to form a slurry, and stretching the slurry by a doctor blade method or the like. . The insulation paste was obtained by kneading low-temperature sintered ceramic material powder and an organic binder. Next, the board that has been bonded is placed in the air at 300 to 700℃.
The copper oxide paste and the organic components in the green sheet were completely removed and the binder was removed. Subsequently, the copper oxide was reduced to metallic copper at 300 to 500°C in a nitrogen gas atmosphere containing 5 to 40% hydrogen gas, and then the metallic copper and green sheet were fired at 850 to 1000°C in a nitrogen gas atmosphere. When the insulation resistance between the wiring layers of the board obtained in this example was measured, as shown in the results shown in the table, shots were generated using the conventional thick film printing method, and the occurrence rate was high. According to the method of the present invention, there was no occurrence of shoots, and the insulation resistance value between wiring layers was obtained to be a highly reliable value of 10 ¹³ Ω or more.

[Table] In the above example, only one layer of unfired green sheets was bonded, but as shown in Figure 3, a desired number of unfired green sheets with wiring layers made of copper oxide paste are laminated to form an unfired insulating layer. The same results as in the above embodiments were also obtained when alumina was bonded to a fired alumina substrate via a multilayer film. In the above embodiments, a green sheet stretched by a doctor blade method or the like was used, but any unfired green sheet with a smooth surface may be used, and it may be obtained by other methods. Effects of the Invention As described above, according to the present invention, by using a sintered ceramic substrate as the base instead of the green sheet that is the base of the green sheet lamination method, it is possible to The green sheet lamination method takes advantage of the fact that it produces a dense insulating layer with a smooth surface and uniform thickness, without film thickness unevenness or pores, and that the multilayer board will not be destroyed due to shoots occurring between wiring layers. With,
Because the green sheet is temporarily fixed to the base sintered ceramic substrate, the green sheet will not shrink during firing and the substrate will not warp, making it possible to obtain a ceramic multilayer substrate with high dimensional accuracy. The advantages of ceramic multilayer substrates can also be realized. Furthermore, in the present invention, since the green sheet is fired after reducing the copper oxide to copper, the copper oxide is sufficiently reduced, and the conductor resistance of the conductor wiring layer decreases. ) increases, the performance as a circuit improves significantly, and
Since the heat generated by the conductor itself is also reduced, the heat dissipation effect of the circuit can be improved and power consumption can also be reduced. Furthermore, according to the present invention, since the ceramic fired substrate and the unfired green sheet are bonded via the insulating paste mainly composed of a low-temperature sintered ceramic material, no heat or pressure is required for bonding, and therefore the insulating paste Even in the case of highly laminated multilayer boards, the effectiveness of the heat and pressure applied to them does not matter, so even in the case of highly laminated multilayer boards, it is possible to reliably bond the fired ceramic board and the green sheet, creating a reliable ceramic multilayer board that will not peel off. can be obtained. Furthermore, since bonding is possible simply by placing an unfired green sheet on the insulating paste, it is possible to support multilayer substrates of various shapes.

[Brief explanation of the drawing]

1 and 3 are manufacturing process diagrams of a ceramic multilayer substrate according to an embodiment of the present invention, FIGS. 2a and 2b are cross-sectional views of the ceramic multilayer substrate during the manufacturing process, and FIG. 4 is a conventional printed multilayer substrate. 1 is a manufacturing process diagram showing the method. 1... Alumina fired substrate, 2... Wiring layer, 3...
...Insulating layer made of insulating paste, 4...Unfired green sheet.

Claims (1)

[Claims] 1. An unfired wiring layer is applied on a fired ceramic substrate using a copper oxide paste containing copper oxide as a main component,
An unfired insulating layer is formed on the fired ceramic substrate by bonding an unfired green sheet with a wiring layer made of the copper oxide paste after interposing an insulating layer formed of an insulating paste containing a low-temperature sintered ceramic material as a main component. A layer is formed and heat treated in air or an oxidizing atmosphere at a temperature sufficient to decompose the organic components in the green sheet, and then in a reducing atmosphere at a temperature below the sintering of the green sheet, and A sintered insulating layer is obtained by performing heat treatment at a temperature above which copper oxide is reduced to metallic copper, and then firing in an atmosphere that is non-oxidizing to copper and at a temperature lower than the melting point of copper. A method for manufacturing a ceramic multilayer substrate. 2. The method of manufacturing a ceramic multilayer substrate according to claim 1, wherein printing of copper oxide paste and adhesion of unfired green sheets are repeated a desired number of times to form a multilayer.