JPS6237917B2 - - 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 conductor 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, and conducted various studies on the components, content, melting point, particle size, etc. of the flux contained in the insulating paste. As a result of conducting this, we found that instead of the conventionally used insulating paste, the flux contained in the insulating paste had a lower melting point than the flux contained in the green sheet, and the content was the same as that of the flux contained in the green sheet, or It was discovered that by using more insulating paste than the green sheet, the lack of sintering was resolved, and a ceramic multilayer circuit board without cracks or warping could be manufactured. The present invention provides a method for 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 simultaneously, in which the flux contained in the insulating paste is lower than the flux contained in the green sheet. The present invention relates to a method for manufacturing a ceramic multilayer circuit board using an insulating paste having a melting point and a flux content equal to or greater than that of the flux contained in the green sheet. Note that the composition of the flux used in the insulating paste in the present invention is not limited as long as it has a lower melting point than the flux contained in the green sheet, and the content thereof must be the same as or greater than that of the green sheet. It is. 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 conductive paste used for printing is not limited in any way and may be a commonly used conductive paste. 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 forming a ceramic slip, a green sheet with a thickness of 0.8 mm was obtained by tape casting. Next, 5 parts by weight of flux Y, which has a lower melting point than flux
Then, an insulating paste was obtained through the same process as above. Next, apply W (tungsten) conductor paste (manufactured by Asahi Chemical, trade name:
3TW-1000) to form a circuit, the above-mentioned insulating paste was printed on top of it to a thickness of 30 μm, and this process was repeated four times to form a four-layer multilayer circuit. After that, it was heated in air at a heating rate of 50°C/hour to 300°C, and from 300°C in a hydrogen atmosphere to 1500°C at a heating rate of 30°C/hour. A ceramic multilayer circuit board was obtained by co-firing the insulating paste. The appearance of this ceramic multilayer circuit board was observed, and no cracks or warpage occurred in the insulating layer. 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 A four-layer multilayer circuit was formed on the green sheet used in Example 1 in the same manner as in Example 1 using a ceramic strip containing 3.8 parts by weight of flux X shown in Table 1 as an insulating paste. Thereafter, the green sheet, conductive paste and insulating paste were simultaneously 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 under a microscope, cracks 1 were found in the insulating layer 2 as shown in FIG. Note that in the second example, 3 is a conductor layer on the lower surface of the insulating layer 2.

[Table] In the present invention, the flux contained in the insulating paste forming the insulating layer has a lower melting point than the flux contained in the green sheet serving as the substrate, and the content is the same as that of the flux contained in the green sheet, or the flux contained in the green sheet Since a larger amount of insulating paste is used, insufficient sintering of the insulating layer is eliminated, and the occurrence of 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, the flux contained in the insulating paste is greater than the flux contained in the ceramic green sheet. A method for manufacturing a ceramic multilayer circuit board, characterized by using an insulating paste having a low melting point and a flux content equal to or greater than that of the flux contained in the ceramic green sheet.