JPS62145896A - Manufacture of ceramic copper multilayer wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to ceramic wiring that can be used as a high-density mounting board for circuits on which ICs, LSIs, chip components, etc. are mounted and interconnected. The present invention relates to a method of manufacturing a substrate.

BACKGROUND OF THE INVENTION Conventionally, the metals for conductive paste of ceramic wiring boards include Au, Au-Pt', and Ag-Pt.

Noble metals such as Ag-Pd, W, MO, Mo-M
High melting point base metals such as n were widely used. The former,
Noble metal pastes such as Au, Au-Pt, Ag-Pt, Ag-Pd, etc. can be baked in air, but have the problem of high cost.

Furthermore, the latter high-melting point base metals such as W, Mo, and Mo-Mn are dangerous because they have low conductivity and need to be fired in a reducing atmosphere. Also, add N to the conductor surface for soldering.
This method has problems such as the need to perform plating treatment using, for example, i. Therefore, Cu paste, which is inexpensive, has good conductivity, and has good soldering properties, has come to be used. Here, an example of a method for manufacturing a ceramic wiring board using Cu paste will be described. The conventional method is to screen print Cu paste on a sintered substrate such as alumina to form a wiring pattern, and after drying, apply carbon at a temperature below the melting point of Cu.
Firing is performed in a nitrogen atmosphere in which the oxygen partial pressure is controlled so that u is not oxidized and the organic components in the conductor paste are sufficiently combusted.

Furthermore, in the case of a ceramic multilayer wiring board using Cu paste, printing, drying, and firing in a neutral atmosphere are repeated for each of the insulating paste and Cu paste a desired number of times to form a multilayer structure.

Problems to be Solved by the Invention However, when using the above-mentioned Cu paste,
There are several major problems in the method of manufacturing ceramic wiring boards. First of all, in the firing process, Cu
It is extremely difficult to control the oxygen partial pressure in the furnace to a level that does not oxidize the Cu paste and completely burns the organic components in the Cu paste. If the oxygen partial pressure is even slightly high, the Cu surface will be oxidized and soldering will be poor.
On the other hand, if the oxygen partial pressure is too low, not only will good adhesion of the Cu metallization not be obtained, but the organic components contained in the Cu paste will not be completely burned off. It is said that organic binders do not decompose especially at temperatures below the melting point of Cu. (Japanese Unexamined Patent Publication No. 55-128899) In addition, when metal Cu is used, even if the binder removal process and the Cu baking process are separated, the metal Cu will be oxidized in the binder removal process, causing volume expansion. This causes problems such as peeling off from the substrate. Secondly, in the case of multi-layer printing, baking is performed each time after printing and drying, resulting in a long lead time. Therefore, in Japanese Patent Application No. 59-147833, we created a multi-layered structure by repeatedly printing insulating paste and conductive paste using CuO paste, creating an oxidizing atmosphere sufficient for carbon and sufficient to thermally decompose the organic components inside. heat treatment at a temperature of
Thereafter, the method for producing a ceramic multilayer wiring board is characterized in that an atmosphere is created that is non-oxidizing to Cu, and the printed CuO is reduced to metal Cu and sintered.
Already proposed. This method makes it easier to control the atmosphere during firing and allows simultaneous firing. However, new problems as shown below were discovered.

As shown in FIG. 6, there are cases in which the insulating layer 3 is partially printed on the conductor layer 2, and a structure in which the conductor layer is printed on top of it so as to intersect with the conductor layer below. When the cross section is as shown in Fig. 7, there is a problem that the insulating layer is not smooth and the thickness of the wiring pattern is not constant. In the case shown in the figure, if volumetric contraction occurs due to the reduction of CuO to Cu during firing, there is a problem that the wiring pattern of the same layer will be disconnected between the part covered with the insulating layer and the exposed part. be.

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method that eliminates the above-mentioned drawbacks and can form an inner layer conductor with high reliability.

Means for Solving the Problems In order to solve the above problems, in the method for manufacturing a ceramic copper multilayer wiring board of the present invention, an inorganic component containing CuO as a main component is added to an alumina sintered substrate or a green sheet. The conductor layer paste is made by adding an organic vehicle to the conductor layer and the insulating layer paste is made by adding an organic vehicle to glass or glass-ceramic. After repeating the printing and drying of the insulating layer for the desired number of layers, removal of the binder, reduction of CuO to Cu, and sintering are performed at a predetermined temperature and atmosphere to form the inner layer wiring bag, and then,
A Cu paste is used as the top layer, and after printing and drying, it is fired in a nitrogen atmosphere.

As described above, in the present invention, since the insulating layer is printed so as to cover the entire surface of the substrate except for the via portion, when the conductive layer is next formed on the insulating layer, the printing of the substrate is Since the surface is smooth, it is very easy to print, and the thickness of the formed wiring pattern is stable. Furthermore, since the wiring pattern in the lower layer is not partially covered, the wiring pattern is not cut between the portion covered with the insulating layer and the portion not covered.

Furthermore, in the present invention, since the depinemization step is carried out in an oxidizing atmosphere, the organic binder contained in the insulating layer can be completely decomposed and removed, making it possible to produce ceramic copper multilayer wiring boards that are extremely dense and have excellent insulating properties. It can be made.

Example Examples of the present invention will be described below.

Example 1: First, the CuO paste for the inner layer was commercially available special grade C.
#705 manufactured by Corning Co., Ltd. for uO (average particle size approximately 3 μm)
The material was prepared by adding 5 wt% of 9 glass (average particle size approximately 2 μm) and an organic vehicle in which ethyl cellulose, which is an organic binder, is dissolved in turpentine oil, and kneading the mixture to an appropriate viscosity using a three-stage roll. On the other hand, insulation paste
It was prepared by adding an organic vehicle similar to the CuO paste to an inorganic component consisting of a 1:1 weight ratio of borosilicate glass and alumina, and kneading the mixture to an appropriate viscosity using a three-stage roll.

Next, CuO paste was printed on a 96% alumina sintered substrate with a 250 mesh screen and dried (120°C).
(for 10 minutes) to form a conductor layer.

Then, using a screen with 200 meshes of insulating paste, print the previously printed and dried conductor layer so as to cover the entire surface of the board except for the via area, and dry (1
(at 20° C. for 10 minutes) to form insulation. Then, printing and drying of the CuO paste and the insulating paste were repeated to produce an unsintered ceramic wiring board having a cross section as shown in FIG. In the figure, (1) is a substrate, (2) is a conductor layer, and (3) is an insulating layer. The unsintered ceramic wiring board thus produced was debindered in air with the temperature profile shown in FIG. 2
0/80: Flow rate 2 j! /mjn) and finally calcined in N2 with the temperature profile shown in FIG.

On the ceramic copper multilayer substrate produced in this way, D
U Pont #9153 Cu paste was printed with a 325 mesh screen to form a wiring pattern, dried (110° C. for 10 minutes), and then baked at 900° C. (kept at peak temperature for 10 minutes) in N2. A cross-sectional view after firing is shown in FIG. As a result of a continuity test, the ceramic copper multilayer wiring board thus produced had no disconnection in the inner layer, and the thickness of the top layer was also measured and found to have a very uniform thickness.

Example 2: An experiment similar to that shown in Example 1 was conducted using a green sheet instead of the 96% alumina sintered substrate. Green sheets are made by adding debutyl phthalate, a plasticizer, to an organic solvent made by dissolving polyvinyl butyral, an organic binder, in toluene, to an inorganic component that is a mixture of borosilicate glass and alumina at a weight ratio of 1:1. The mixture was mixed in a ball mill, degassed, and then formed into a film using a doctor blade method, dried to a thickness of about 1 inch, and then cut into a predetermined size for processing.

Incidentally, since the green sheet undergoes volumetric shrinkage during the firing stage of the inner layer, it goes without saying that the screen for printing the top layer is prepared with the volumetric shrinkage due to firing taken into account in advance. As in Example 1, the ceramic steel multilayer board produced in this way also showed no disconnections in the inner layer at all as a result of the continuity test, and it was also found that the film thickness of the top layer wiring pattern was extremely uniform. It had a film thickness.

Furthermore, green sheets contain a large amount of organic components, but by removing the binder in the air as in the present invention, the organic components in the green sheets are completely decomposed and removed, making them extremely dense and strong. A substrate was obtained.

In this example, the case where there were three conductor layers was shown, but similarly good results were obtained with other numbers of layers.

Effects of the Invention As described above, the manufacturing method of the present invention makes it easier to print each conductor layer, provides a uniform film thickness, and is also a ceramic copper material that eliminates the risk of cutting the inner layer conductor. It has become possible to create multilayer wiring boards. Furthermore, since it is a copper multilayer board, it can take full advantage of Cu's low conductor resistance, good solderability, good migration resistance, and low cost, making it extremely effective industrially. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an unsintered ceramic wiring board manufactured by the method of manufacturing a ceramic cotton-like multilayer wiring board of the present invention, and FIG. 2 is a cross-sectional view of a ceramic copper multilayer wiring board manufactured by the manufacturing method of the present invention. , Fig. 3 is a characteristic diagram showing an example of the temperature profile during depine mite removal, Fig. 4 is a characteristic diagram showing an example of the temperature profile during the reduction process, and Fig. 5 is a characteristic diagram showing an example of the temperature profile during the baking process. , FIG. 6 is a perspective view showing a part of a ceramic/copper multilayer board manufactured by the method shown in the conventional example, and FIG. 7 is a sectional view of the ceramic copper multilayer board also shown in the conventional example. 1...Substrate, 2...Conductor layer, 3...
...Insulating layer.

Claims (2)

[Claims] (1) An insulating layer can be formed on an alumina sintered substrate using a conductor layer paste made of an inorganic component containing CuO as the main component plus an organic vehicle, and an insulating layer paste made of glass or glass-ceramic with an organic vehicle added. The lower conductor layer is made to cover the entire surface of the board except for the via area.
The process of repeating printing and drying of the conductive layer and the insulating layer a desired number of times to form wiring, and the process of forming the unsintered body in an atmosphere sufficiently oxidizing for carbon and thermally decomposing the organic components inside. On the ceramic copper wiring board obtained in this way, A method for manufacturing a ceramic copper multilayer wiring board, comprising a step of forming a wiring pattern using Cu paste, and then a step of firing in a nitrogen atmosphere. (2) The manufacturing method according to claim 1, wherein the unsintered body is formed by a green sheet printing method.