JPS6238880B2 - - 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. 56-7957, 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. In addition, this method has the disadvantage that the adhesive strength between the metallized portion of the outermost conductor layer and the material to be silver soldered is reduced, and lead pins and terminals soldered with silver may peel off. On the other hand, we attempted a method in which a green sheet containing flux was pulverized, then an insulating paste was redissolved by adding a solvent, and a multilayer circuit was formed by printing together with a conductive paste in the same manner as described above, followed by simultaneous firing. 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, as a result of various studies in order to compensate for the above-mentioned drawbacks, the present inventors found that a conductive paste that does not contain a flux component was used for the conductive paste that forms the outermost conductive layer, and that the conductive paste that does not contain a flux component is used for the conductive paste that forms the outermost conductive layer. When a multilayer circuit was formed using a conductor paste containing a flux component and simultaneously fired to produce a ceramic multilayer circuit board, it was possible to prevent the occurrence of cracks, warpage, etc., and to achieve the best results. Lead pins, terminals, etc. that are silver-brazed to prevent a decrease in adhesive strength between the metallized part of the outer conductor layer and the material to be silver-brazed.
It was possible to prevent peeling of soldered chip carriers, etc. However, on the other hand, since the same conductive paste is used for the through-hole portion and the circuit portion, there is a drawback that the resistivity of the circuit increases. The present invention does not cause cracks or warpage in the insulating layer, and the adhesive strength between the metallized portion of the outermost conductor layer and the material to be silver-brazed is reduced, resulting in silver-brazed lead pins, terminals, soldered chip carriers, etc. The object of the present invention is to provide a method for manufacturing a ceramic multilayer circuit board that prevents peeling of the ceramic material and does not cause an increase in the resistivity of the circuit. The present inventors have 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 further investigation, we decided to use a conductor paste that does not contain flux components for the conductor paste that forms the outermost conductor layer, and that the conductor paste that forms the internal circuit contains the same flux as the insulating paste. A conductive paste containing flux is used, and the conductive paste that makes the through-hole part conductive contains the same flux as that contained in the insulating paste, and the conductor paste contains more flux than the conductive paste that forms the internal circuit. When using the paste, there were no cracks or warping, and silver-brazed lead pins, terminals, etc.
Soldered chip carriers etc. do not peel off,
We have also discovered that it is possible to produce a ceramic multilayer circuit board without an increase in the resistivity of the circuit. 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 conductive paste for internal circuit formation, the insulating paste, and the conductive paste for through-hole continuity are the same, and the conductive paste for through-hole continuity contains flux. The present invention relates to a method for manufacturing a ceramic multilayer circuit board in which the amount of flux is greater than the flux content of the internal circuit-forming conductive paste. In the present invention, the ceramic material is not limited in any way, and for example, alumina is generally used. Further, the green sheet used in the present invention is not limited in terms of thickness, material, flux, etc. In the present invention, it is necessary to use a conductor paste that does not contain a flux component as the conductor paste forming the outermost conductor layer, and if the conductor paste contains a flux component, the adhesive strength of the metallized part will decrease, and the There is a drawback that soldered chip carriers such as brazed lead pins and terminals may peel off. The conductive paste used for through-hole continuity and internal circuit formation should contain the same flux as the insulating paste, and the content should be determined by considering the effect of increasing specific resistance. The circuit is 8% by weight or less, and the through-hole part is 15% by weight.
It is preferably less than % by weight. However, it is necessary that the amount of flux contained in the through-hole conductive conductive paste is greater than the amount of flux contained in the internal circuit-forming conductive paste. If the amount of flux contained in the through-hole conductive paste is smaller than the amount of flux contained in the internal circuit-forming conductive paste, a disadvantage arises in that the resistivity of the circuit increases. In addition, unless a flux component is included in the internal circuit-forming conductive paste and the through-hole conductive conductive paste, insufficient sintering of the insulating layer cannot be solved, and the object of the present invention cannot be achieved. 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. 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, 8 parts by weight of the flux shown in Table 1 was added to 92 parts by weight of W (tungsten) conductor paste (manufactured by Asahi Chemical, trade name 3TW-1000) and mixed uniformly with a pestle to obtain flux-containing conductor paste A. Created. In addition, in addition to 85 parts by weight of the W conductor paste mentioned above,
Flux-containing conductor paste B was prepared by adding 15 parts by weight of the flux shown in the table and mixing uniformly with a pestle. Next, attach the green sheet mentioned above to a diameter of 0.3 mm (φ).
After forming a through hole, apply flux-cored conductor paste B to the through-hole, and then form a circuit with flux-cored conductor paste A 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 not electrically conductive). ), print the above-mentioned insulating paste on top to a thickness of 30 μm,
This process was repeated four times on the front side and twice on the back side to form a six-layer multilayer circuit, and then a flux-free W conductor paste (manufactured by Asahi Chemical, trade name 3TW-1000) was applied to the outermost conductor layer. 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.
An insulating paste, a W conductor paste containing no flux component, and flux-containing conductor pastes A and B 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. Lead pins were bonded onto the terminals of the metallized portion using silver solder, but no peeling of the lead pins occurred. Further, the resistivity of the circuit did not increase.

[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 each of the front and back sides of the green sheet was coated. A 6-layer multilayer circuit was formed in the same manner as in Example 1, except that the W conductor paste containing no 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. In FIG. 2, reference numeral 3 indicates a conductor layer on the lower surface of the insulating layer 2. In FIG. However, although lead pins were bonded onto the terminals of the metallized portion with silver solder, no peeling of the lead pins occurred, and no increase in the resistivity of the circuit was observed. Comparative Example 2 A ceramic multilayer circuit board was obtained using the flux-cored conductor paste A used in Example 1 for the outermost conductor layer, but in the same manner and under the same conditions as in Example 1 except for the fact that the flux-cored conductor paste A used in Example 1 was used for the outermost conductor layer. When we observed the appearance of this ceramic multilayer circuit board using a microscope, we found that there were no microcracks or warpage in the insulating layer above the through holes, and no increase in the resistivity of the circuit was observed. When silver brazing was performed on the terminal, the adhesive strength of the lead pin decreased to about 50% of that in Example 1.
It peeled off with just a little force applied to the lead pin. Comparative Example 3 Flux-cored conductor paste B was applied to the through-hole portions of the green sheet used in Example 1, and circuit paths were formed on the front and back sides of the green sheet using the same flux-cored conductor paste B as described above, and other A ceramic multilayer circuit board was obtained using the same method and conditions as in Example 1. When we observed the appearance of this ceramic multilayer circuit board using a microscope, we found that there were no microcracks or warpage in the insulating layer above the through-holes.Also, although lead pins were bonded with silver solder to the terminals in the metalized part, Although no separation occurred, the resistivity of the circuit increased by approximately 20%. The present invention uses a conductor paste that does not contain a flux component for the conductor paste that forms the outermost conductor layer, and the conductor paste that forms the internal circuit contains the same flux as that contained in the insulation paste. The conductive paste that makes the hole conductive contains the same flux as the insulating paste, and has a higher content than the conductive paste that forms the circuit, so there is no possibility of insufficient sintering of the insulating layer. This eliminates the occurrence of cracks, warping, etc., and the adhesive strength between the metallized part of the outermost conductor layer and the silver soldering material does not decrease, so lead pins, terminals, chip carriers, etc. do not peel off. It is possible to manufacture a ceramic multilayer circuit board without increasing the specific resistance of the circuit.

[Brief explanation of the drawing]

Fig. 1 is a microscopic photograph of the surface of the ceramic multilayer circuit board obtained in the example, Fig. 2 is a microscopic photograph of the surface of the ceramic multilayer circuit board obtained in the comparative example, and Fig. 3 is a microscopic photograph of the surface of the ceramic multilayer circuit board obtained by the conventional method. It is a micrograph of the surface of a 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. The conductor paste for internal circuit formation, the insulation paste, and the conductor paste for through-hole continuity are the same, and the flux content of the conductor paste for through-hole continuity is the same. A method for manufacturing a ceramic multilayer circuit board, characterized in that the flux content is greater than that of the internal circuit-forming conductor paste.