JPS6237919B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing ceramic multilayer circuit boards. Conventionally, ceramic multilayer circuit boards are manufactured by printing conductive paste on a pre-sintered ceramic substrate, and then
Previously, they were manufactured by printing an insulating paste, repeating this multiple times to form a multilayer circuit, and then firing it.
According to this method, the insulating layer shrinks more during firing than the pre-sintered ceramic substrate, so it has the disadvantage that the insulating layer may crack or warp. In order to compensate for this drawback, as shown in Japanese Patent Publication No. 55-7957, Japanese Patent Publication No. 55-24271, etc., a multilayer printing method is used to print a ceramic green sheet (hereinafter referred to as "green sheet") using a conductive paste and an insulating paste. I tried forming the circuit and firing it at the same time, but it was not very effective. We also attempted a method of pulverizing a green sheet containing flux, then adding a solvent and remelting the insulating paste to form a multilayer circuit using a printing method along with a conductive paste in the same manner as above, and simultaneously firing it. Even with this method, when the multi-layer printed insulation paste is sintered, the insulation layer 2 is sintered as shown in Figure 3.
There was a defect that caused crack 1. In addition, in FIG. 3, 3 is a conductor layer on the lower surface of the insulating layer 2. In addition to the above, as shown in Japanese Patent Publication No. 54-38291, a conductive paste and an insulating paste containing flux are used on a temporary substrate to sinter the laminate together by a printing method, and during sintering or sintering. There is a method of manufacturing a laminated ceramic substrate by removing the above-mentioned temporary substrate from the laminate after drying, but this method involves forming an insulating layer (corresponding to a green sheet) on the top surface of the temporary substrate and other insulating layers. In order to use an insulating paste containing all fluxes of the same quality, a multilayer circuit is formed by a printing method using the insulating paste, which is re-dissolved by adding a solvent after crushing the green sheet containing the above-mentioned flux, along with the conductive paste. However, the structure is similar to that of the simultaneous firing method, which has the drawback of causing cracks in the insulating layer. The object of the present invention is to provide a method for manufacturing a ceramic multilayer circuit board free of such drawbacks. The present inventors focused on the fact that cracks, warpage, etc. that occur in the insulating layer are caused by insufficient sintering of the insulating layer,
As a result of various studies on the components, content, melting point, particle size, etc. of the flux contained in the insulating paste, we decided to use separate insulating pastes for the lower and upper layers, and the lower layer's insulating paste contained in the green sheet. Use an insulating paste that is the same flux as the flux contained in the green sheet and has a flux content equal to or greater than the flux contained in the green sheet, and the upper layer insulating paste contains a lower flux than the lower layer. By using an insulating paste that has a melting point and a flux content that is equal to or greater than the flux contained in the underlying insulating paste, insufficient sintering of the insulating layer can be eliminated and ceramics without cracks or warping can be created. It has been discovered that multilayer circuit boards can be manufactured. The present invention is a method of manufacturing a ceramic multilayer circuit board by printing a conductive paste and a ceramic insulating paste multiple times on a green sheet and firing them at the same time. For the insulating paste, use an insulating paste containing the same amount of flux as that contained in the green sheet or more than that contained in the green sheet,
A ceramic multilayer circuit in which the upper layer insulation paste uses an insulation paste that has a lower melting point than the flux contained in the lower layer insulation paste and contains the same amount of flux as or more than the flux contained in the lower layer insulation paste. Related to a method of manufacturing a substrate. In the present invention, the composition of the insulating paste used for the lower layer is not limited as long as it is the same as the flux contained in the green sheet serving as the base, and the content of flux contained in the insulating paste is the same as that contained in the green sheet. It is necessary to use the same amount as the flux or more than the green sheet. If the amount is less than the green sheet, it will not be possible to solve the problem of insufficient sintering of the insulating layer, and the object of the present invention will not be achieved. The insulating paste used for the upper layer has no restriction as long as it has a lower melting point than the insulating paste used for the lower layer, and the content of flux contained in the insulating paste is the same as the flux contained in the lower layer insulating paste. It is necessary to have more than the amount or green sheets. If the amount is smaller than the lower layer insulation paste, the problem of insufficient sintering of the insulation layer cannot be solved and the object of the present invention cannot be achieved. The lower layer refers to more preferably 1/2 or less of the number of layers on the green sheet side serving as the base, and the same concept applies when insulating layers are printed on both sides. In the present invention, the type of conductive paste to be printed is not limited, nor is the thickness of the insulating paste to be printed to be limited. The present invention will be explained below with reference to Examples. Example 1 3.8 parts by weight of flux X shown in Table 1 was added to 96.2 parts by weight of high-purity alumina (alumina purity of 99.5% or more) with an average particle size of 2 μm and mixed uniformly to obtain raw material powder A. To 100 parts by weight of this raw material powder A, 8 parts by weight of polyvinyl butyral resin as a binder, 4 parts by weight of phthalate ester as a plasticizer, 20 parts by weight of butanol and 50 parts by weight of trichlorethylene as a solvent were added, and the mixture was uniformly mixed in a ball mill. After that, a green sheet with a thickness of 0.8 mm was obtained by tape casting. Next, 5 parts by weight of the above-mentioned flux X was added to 95 parts by weight of the above-mentioned high-purity alumina and mixed uniformly to obtain raw material powder B, and the same process as above was performed to obtain insulation paste A. Separately from the above, 5.5 parts by weight of the flux Y shown in Table 1 was added to 94.5 parts by weight of the high-purity alumina and mixed uniformly to obtain raw material powder C. Further, the same process as above was performed to obtain insulation paste B. Ta. Next, apply W (tungsten) conductor paste (manufactured by Asahi Chemical, product name: 3TW) on the green sheet mentioned above.
-1000) to form a circuit, then print the above-mentioned insulating paste A on top of it to a thickness of 30 μm,
Repeat this process twice, that is, alternately print conductive paste and insulating paste A twice, then use insulating paste B on top of that, and repeat alternately print conductive paste and insulating paste B twice in the same way as above. , a four-layer multilayer circuit was formed.
After that, it is heated in air at a heating rate of 50°C/hour up to 300°C, and from 300°C in a hydrogen atmosphere at a heating rate of 30°C/hour to 1500°C to produce green sheets, conductive pastes, and insulating pastes. A and B were fired simultaneously to obtain a ceramic multilayer circuit board. The appearance of this ceramic multilayer circuit board was observed, and no cracks or warpage occurred.
FIG. 1 shows a microscopic photograph of the surface of the insulating layer 2 of the ceramic multilayer circuit board. It is clear from FIG. 1 that no cracks occur in the insulating layer 2. Note that in FIG. 1, 3 is a conductor layer on the lower surface of the insulating layer 2. Comparative Example 1 After printing the conductive paste used in Example 1 on the green sheet used in Example 1 to form a circuit, flux X shown in Table 1 was applied on top of it.
A ceramic strip containing 3.8 parts by weight was printed as an insulating paste to a thickness of 30 μm, and this process was repeated 4 times to form a 4-layer multilayer.
Thereafter, the green sheet, conductive paste and insulating paste were co-fired under the same conditions as in Example 1 to obtain a ceramic multilayer circuit board. When the appearance of this ceramic multilayer circuit board was observed using a microscopic photograph, minute cracks 1 were found in the insulating layer 2, as shown in FIG. Furthermore, the second
In the figure, 3 is a conductor layer on the lower surface of the insulating layer 2.

[Table] In the present invention, the insulating paste forming the insulating layer is used separately for the lower layer and the upper layer, and the lower layer insulating paste contains the same flux as that contained in the green sheet, or in an amount equal to or less than that contained in the green sheet. An insulating paste containing the above is used, and the upper layer insulating paste has a lower melting point than the flux contained in the lower layer insulating paste, and the flux content is the same as or higher than the flux contained in the lower layer insulating paste. Since an insulating paste is used, the insulating layer can be sufficiently sintered, and cracks, warping, etc. can be completely eliminated.

[Brief explanation of the drawing]

Figure 1 is a photomicrograph of the surface of the ceramic multilayer circuit board obtained in the example, Figure 2 is a photomicrograph of the surface of the ceramic multilayer circuit board obtained in the comparative example, and Figure 3 is the photomicrograph of the surface of the ceramic multilayer circuit board obtained by the conventional method. This is a microscopic photograph of the surface of a ceramic multilayer circuit board. Explanation of symbols 1...Crack, 2...Insulating layer, 3...Conductor layer.

Claims (1)

[Claims] 1. In a method of manufacturing a ceramic multilayer circuit board by printing a conductive paste and a ceramic insulating paste multiple times on a ceramic green sheet and firing them simultaneously, different insulating pastes are used for the lower layer and the upper layer, and the The insulation paste contains the same amount of flux as the ceramic green sheet, or more than the flux contained in the ceramic green sheet, and the upper layer insulation paste contains the same amount of flux as the ceramic green sheet. A method for producing a ceramic multilayer circuit board, characterized by using an insulating paste that has a lower melting point than the flux contained in the insulating paste and contains the same or more flux than the flux contained in the underlying insulating paste.