JPS6238878B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a ceramic multilayer circuit board. 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 multi-layer printing method using a conductive paste and an insulating paste on a ceramic green sheet (hereinafter referred to as "green sheet") is proposed. 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. 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, after crushing the green sheet containing the aforementioned flux,
The structure is similar to that of a method in which a multilayer circuit is formed by a printing method using an insulating paste that has been redissolved by adding a solvent together with a conductor paste, and then fired at the same time, and has the disadvantage that cracks may occur in the insulating layer. Furthermore, in order to compensate for the above-mentioned drawbacks, the inventors of the present invention conducted various studies, and as a result, formed a multilayer circuit using a conductor paste containing the same flux as that contained in the insulating paste, and simultaneously fired it to form a ceramic multilayer circuit board. When it was manufactured, the crack,
It was possible to prevent the occurrence of warping, etc. However, on the other hand, the adhesive strength of the metallized portion of the outermost conductor layer deteriorated, resulting in the delamination of silver-brazed lead pins, terminals, and soldered chip carriers. An object of the present invention is to provide a method for manufacturing a ceramic multilayer circuit board in which no cracks or warpage occur in the insulating layer, and the adhesive strength of the metallized portion of the outermost conductor layer does not decrease. 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, we decided to use a conductor paste that does not contain a flux component for the conductor paste that forms the outermost conductor layer, and a conductor paste that does not contain flux components for the conductor paste that forms the inner conductor layer (through-hole part and circuit part).
It has been discovered that by using a conductor paste containing a flux component, it is possible to produce a ceramic multilayer circuit board without cracking or warping, and in which silver-brazed lead pins, terminals, and soldered chip carriers do not peel off. The present invention is a method for manufacturing a ceramic multilayer circuit board by printing a conductor paste and a ceramic insulating paste on a green sheet multiple times and firing them simultaneously, in which the conductor paste forming the outermost conductor layer contains a flux component. The present invention relates to a method of manufacturing a ceramic multilayer circuit board using a conductor paste containing no flux component and a conductor paste containing a flux component for the conductor paste forming the internal conductor layer. In the present invention, the ceramic material is not limited in any way, and for example, alumina is often used. Furthermore, there are no restrictions on the thickness, material, flux, etc. of the green sheet. In the present invention, it is necessary to use a conductor paste that does not contain a flux component as the conductor paste that forms the outermost conductor layer, and a conductor paste that contains a flux component as the conductor paste that forms the inner conductor layer. However, if the conductor paste that forms the outermost conductor layer contains flux, the adhesive strength of the metallized part will decrease, and if the conductor paste that forms the inner conductor layer does not contain a flux component, the insulating layer will burn out. The lack of binding cannot be resolved, and the object of the present invention cannot be achieved. The internal conductor layer in the present invention refers to the through-hole part and the circuit part, and the flux used is preferably the same as the flux contained in the insulating paste, and there are no restrictions on the content. However, it is preferable that the paste contains 20% by weight or less (not including 0% by weight). The type of conductive paste used in the present invention, the printing thickness, etc. are not limited at all. The present invention will be explained below with reference to Examples. Example 1 3.8 parts by weight of the flux 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.
And so. 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 for 50 hours. After that, a green sheet with a thickness of 0.8 mm was obtained by tape casting. On the other hand, the ceramic strip described above was used as is as an insulating paste. Next, 10 parts by weight of the flux shown in Table 1 was added to 90 parts by weight of W (tungsten) conductor paste (manufactured by Asahi Chemical, trade name 3TW-1000) and mixed uniformly with a pestle to create a flux-containing conductor paste. did. Next, add a diameter of 0.3mm to the aforementioned green sheet.
After forming a through hole (φ), apply flux-cored conductor paste to this through-hole, and then form a circuit with flux-cored conductor paste on each of the front and back sides of the green sheet (in this state, the front and back sides of the green sheet are conductive). Then, the above-mentioned insulating paste was printed on top to a thickness of 30 μm, and this process was repeated 4 times on the front side and 2 times on the back side to form a 6-layer multilayer circuit, and then a flux component was applied to the outermost conductor layer. A W-containing conductor paste (manufactured by Asahi Chemical, trade name 3TW-1000) was applied. The green sheet is then heated to 300°C in air at a heating rate of 50°C/hour, and from 300°C to 1500°C at a heating rate of 30°C/hour in a hydrogen atmosphere.
A flux-containing conductor paste, a W conductor paste containing no flux component, and an insulating paste were simultaneously fired to obtain a ceramic multilayer circuit board. When the appearance of this ceramic multilayer circuit board was observed, no cracks or warping 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. In FIG. 1, reference numeral 3 denotes a conductor layer on the lower surface of the insulating layer 2. Furthermore, lead pins were bonded onto the terminals of the metallized portion using silver solder, but no peeling of the lead pins occurred.

[Table] Comparative Example 1 A flux-free W conductor paste (manufactured by Asahi Chemical, trade name 3TW-1000) was applied to the through holes of the green sheet used in Example 1, and then applied to the front and back sides of the green sheet. A 6-layer multilayer circuit was formed in the same manner as in Example 1, except that the same W conductor paste that did not contain the flux component as described above and the insulating paste used in Example 1 were used. This product was 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 microscope, microcracks 1 and warpage were found in the insulating layer 2 above the through holes, as shown in FIG. However, although the lead pin was bonded to the terminal of the metallized part using silver solder, the lead pin did not peel off. In addition, in Figure 2, 3
is a conductor layer on the lower surface of the insulating layer 2. Comparative Example 2 The flux-cored conductor paste used in Example 1 was used for the outermost conductor layer, and the other parts were as in Example 1.
A ceramic multilayer circuit board was obtained using the same method and conditions. When we observed the appearance of this ceramic multilayer circuit board using a microscope, we found that there were no microcracks or warping in the insulating layer above the through holes, but when lead pins were silver soldered onto the terminals in the metallized part, the lead pins adhered. The strength was reduced to about 50% of that in Example 1, and the lead pin was peeled off by applying only a small amount of pressure. In the present invention, a conductor paste that does not contain a flux component is used as the conductor paste that forms the outermost conductor layer, and a conductor paste that contains a flux component is used as the conductor paste that forms the inner conductor layer. The lack of sintering is eliminated, eliminating the occurrence of cracks, warping, etc., and the adhesive strength of the metallized part of the outermost conductor layer does not decrease, so lead pins, terminals, chip carriers, etc. can be manufactured in a ceramic multilayer circuit board that does not peel off. can do.

[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 conductor paste and a ceramic insulating paste multiple times on a ceramic green sheet and firing them simultaneously, a flux component is added to the conductor paste forming the outermost conductor layer. A method for producing a ceramic multilayer circuit board, characterized in that a conductor paste containing no flux component is used as a conductor paste that does not contain a flux component, and a conductor paste that contains a flux component is used as a conductor paste that forms an internal conductor layer.