JPS6361799B2 - - 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 were manufactured by printing a conductive paste on a pre-sintered ceramic substrate, then printing an insulating paste, repeating this several times to form a multilayer circuit, and then firing it. According to the authors, the insulating layer shrinks more during firing than the pre-sintered ceramic substrate, so the insulating layer has the disadvantage of cracking and warping. Furthermore, the above method has the disadvantage that printing smudges, smearing, and blurring occur. 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 by printing together with the insulating paste in the same way 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, 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. Furthermore, by adding a process such as printing the conductive paste on the green sheet and crimping it with a press to smooth it, it was possible to reduce or prevent defects such as warping, printing smearing, dripping, and blurring. It was not possible to prevent the occurrence of cracks. The object of the present invention is to provide a method for manufacturing a ceramic multilayer circuit board that does not have these drawbacks. The present inventors have found that the following are the main causes of cracks and warpage occurring in the insulating layer. That is, when the conductive paste is printed and the raised conductive paste is pressed with a press, the conductive paste temporarily sinks into the green sheet. Therefore, the density of this part increases, and since strain is applied to the binder that bonds the ceramic particles, there is an inherent force to restore the structure. If fired in this condition, the firing shrinkage rate of this part will be smaller than that of the part not subjected to pressure bonding force, and furthermore, when the binder softens, a restoring force will be generated, causing cracks, warping, etc. in the insulating layer. . As a result of various studies in view of the above-mentioned drawbacks, the inventors of the present invention succeeded in flattening a multilayer printed green sheet by applying pressure, then leaving it in an organic solvent vapor, and then co-firing the green sheet, conductive paste, and insulating paste. However, it has been discovered that it is possible to produce a ceramic multilayer circuit board with no cracks or warpage in the insulating layer, and no bleeding, sagging, or blurring of printing. The present invention is a method of manufacturing a ceramic multilayer circuit board by printing a conductor paste and a ceramic insulating paste multiple times on a green sheet and firing them simultaneously. The present invention relates to a method for manufacturing a ceramic multilayer circuit board, in which a green sheet, a conductive paste, and an insulating paste are simultaneously fired after being left in steam. Note that the organic solvent used in the present invention has a boiling point
Preferably below 150℃, butanol, trichloroethylene, toluene, xylene, benzene, acetic acid ethyl ester, methyl ethyl ketone,
Ethanol and the like are applicable, but there are no particular limitations, although it is more desirable to use the organic solvent used for casting. The longer the time, the better, but there is no particular limit.Although the temperature at which it is left to stand is around room temperature, it is preferable to leave it in steam at 15 to 40℃ for at least 2 hours. It is more preferable to raise the temperature to a temperature exceeding the boiling point of the solvent, but this is not a limitation. In the present invention, the thickness and material of the insulating paste and the thickness and material of the conductive paste printed are not limited at all. The higher the vapor pressure of the organic solvent, the better the saturated vapor pressure. The present invention will be explained below with reference to Examples. Example 1 4 parts by weight of the flux shown in Table 1 was added to 96 parts by weight of high-purity alumina (alumina purity of 99.5% or more) having an average particle size of 2 μm and mixed uniformly to obtain ceramic powder. 100 parts by weight of this ceramic powder, 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 organic solvents were added, and mixed uniformly in a ball mill to form a ceramic slip. After that, a green material with a thickness of 0.8 mm was made using the tape casting method. Got a sheet. Next, W (tungsten) conductor paste (manufactured by Asahi Chemical, trade name:
3TW-1000) to form a circuit with a thickness of 20 μm, and then smoothed with a pressure of 10 Kg/cm ² . Furthermore, the above-mentioned ceramic strip was printed as an insulating paste on top of it to a thickness of 50 μm, and this process was repeated four times to form a four-layer circuit. then 30±5
The green sheet on which the multilayer circuit was printed was left to stand for 8 hours in saturated vapor of the above-mentioned mixed organic solvent, and then heated to 120° C. in the saturated vapor state to remove internal distortion of the green sheet on which a multilayer circuit was printed. This stuff in air up to 300℃ 50
Heating at a heating rate of ℃/hour, and then heating from 300℃ to 1500℃ at a heating rate of 30℃/hour in a hydrogen atmosphere.
The green sheet, conductive paste, and insulating paste were co-fired by raising the temperature to ℃ to obtain a ceramic multilayer circuit board. When the appearance of this ceramic multilayer circuit board was observed, no cracks or warpage occurred in the insulating layer. Furthermore, there was no occurrence of printing smudges, drips, or haze. 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. Comparative Example 1 The green sheet of Example 1 on which a multilayer circuit was printed was not subjected to strain removal using saturated steam, but the green sheet, conductor paste, and insulating paste were co-fired under the same conditions as Example 1 to produce a ceramic multilayer circuit board. I got it. When the appearance of this ceramic multilayer circuit board was observed using a microscope, no bleeding, sagging, or blurring of the print occurred, but warping and cracks 1 occurred in the insulating layer 2 as shown in FIG.

[Table] Example 2 The green sheet of Example 1 on which a multilayer circuit was printed was placed in a sealed container (18 cans) with the same mixed organic solvent as in Example 1, and this was heated at 50° C. for 3 hours. Next, it was cooled to 25°C while being sealed and left for 24 hours. After unsealing the can, the temperature was raised to 120°C at a temperature increase rate of 5°C/hour with the lid on, and the temperature was further maintained at 120°C for 2 hours. Removed distortion. Thereafter, it was fired in the same manner as in Example 1 to obtain a ceramic multilayer circuit board. When the appearance of this ceramic multilayer circuit board was observed, no cracks or warpage occurred in the insulating layer. Also, printing smudges,
No blurring occurred. The present invention pressurizes a green sheet on which a multilayer circuit is printed, then leaves it in organic solvent vapor, and then simultaneously fires the green sheet, conductive paste, and insulating paste, thereby removing internal distortion of the green sheet and insulating it. It is possible to prevent cracks, warping, etc. that occur in the layer, and it is also possible to prevent bleeding, sagging, and blurring of printing.

[Brief explanation of drawings]

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 ceramic green sheet on which the multilayer circuit is printed is pressed, and then an organic solvent is applied to the ceramic green sheet. 1. A method for manufacturing a ceramic multilayer circuit board, which comprises simultaneously firing a ceramic green sheet, a conductive paste, and an insulating paste after leaving the ceramic green sheet in steam.