JPH06232550A - Manufacture of ceramic multilayer wiring board - Google Patents

Abstract

(57) [Summary] [Structure] After the reduction step of forming a wiring pattern containing CuO as a main component on the green sheet, stacking and multilayering, and performing heat treatment in a reducing atmosphere to reduce to Cu, the total amount of Cu is reduced. The green sheet is sintered in a non-oxidizing atmosphere through an oxidation treatment step for partial oxidation so that the amount of CuO with respect to 3 is in the range of 3 to 30 mol%. [Effect] Since the contraction rates of copper and ceramic can be matched and the wettability of both can be improved, it is possible to prevent warpage and deformation of the multilayer substrate, peeling of the conductive material, and formation of voids in the inner layers of the multilayer substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a ceramic multilayer wiring board for mounting semiconductor LSIs, chip parts and the like and interconnecting them.

[0002]

2. Description of the Related Art In recent years, gold, silver, palladium, or a mixture thereof is usually used as a conductive material for a ceramic multilayer substrate. However, these metals are precious metals, are expensive, and have large price fluctuations. Therefore, it is desired to use Cu electrode materials that are inexpensive and have little price fluctuations.

Therefore, an example of a method for manufacturing a multilayer substrate using Cu electrodes will be described. The method is to form a wiring pattern by screen-printing a Cu paste on a sintered substrate such as alumina, and after drying, a temperature (850 to 9) below the melting point of Cu.
Firing is performed at about 50 ° C.) in a nitrogen atmosphere in which the oxygen partial pressure is controlled so that Cu is not oxidized and the organic components in the conductor paste are sufficiently burned. In the case of multiple layers, it is obtained by printing and firing the insulating layer under the same conditions. However, when using the Cu paste as described above, there are some problems. First of all, it is difficult to control the atmosphere in the firing step under an appropriate oxygen partial pressure. That is, if oxygen is large, Cu is oxidized, and if it is small, the organic binder in the paste is not decomposed and good metallization cannot be obtained. Secondly, in the case of forming multiple layers, it is necessary to repeat firing each time after printing each paste, which leads to a long lead time, leading to an increase in the cost of equipment and the like. Therefore, in Japanese Patent Laid-Open No. 3-20914, there has been already disclosed a method of using a cupric oxide paste in three steps of a binder removal step, a reduction step, and a firing step in manufacturing a ceramic multilayer substrate. It uses cupric oxide as a starting material for a conductor to form a multilayer body, and in the binder removal step, heat treatment is performed in a sufficient oxygen atmosphere for carbon and at a temperature sufficient to thermally decompose the organic binder inside. Next, the reduction step of reducing cupric oxide to copper and the firing step of sintering the substrate are established. As a result, it became easy to control the atmosphere during firing, and a dense sintered body could be obtained.

[0004]

However, the following problems have become clear. This is because the contraction start temperature of copper, which is a conductor material, differs depending on the material used for the ceramic multilayer, the contraction degree after firing is different, and in addition, the reduction is completely performed to prevent wetting of copper and ceramics. Since it is bad, no reaction occurs and good adhesion cannot be achieved. As a result, the multilayer board is warped, deformed, and the conductor material is peeled off, and a cavity is formed between the insulating material and the conductor material in the inner layer of the multilayer board.

[0005]

In order to solve the above problems, the manufacturing method of the present invention comprises a step of forming a wiring pattern containing CuO as a main component on a green sheet and laminating a desired number of layers to form a multilayer structure. In the method for manufacturing a ceramic multilayer wiring board, which includes a reducing step of heat-treating in a reducing atmosphere to reduce CuO and a firing step of sintering the green sheet in a non-oxidizing atmosphere, between the reducing step and the firing step. Then, an oxidation treatment step of partially oxidizing so that the existing amount of CuO with respect to the total Cu amount is in the range of 3 to 30 mol% is added to produce a ceramic multilayer wiring board.

[0006]

According to the present invention, the conductive Cu reduced by adding the oxidation treatment step between the reduction step and the firing step as described above.
Is slightly oxidized to form CuO in a part of the Cu conductor.
By doing so, it is possible to control the shrinkage rate during firing, and it is possible to match the shrinkage rate of the insulating material with that of the conductor.
Moreover, it became possible for some CuO to assist the reaction between the conductor layer and the substrate.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, the method for producing a ceramic substrate will be described. The ceramic powder having the above-mentioned substrate composition is used as an inorganic component, polyvinyl butyral as an organic binder, di-n-butyl phthalate as a plasticizer, and a mixed solution of toluene and isopropyl alcohol (30). (70 weight ratio) was mixed to form a slurry. This slurry was formed into a sheet on an organic film by the doctor blade method. At this time, a system was used in which each step of continuously drying, punching, and if necessary, through hole processing from the film formation was performed. A conductor pattern was formed on this green sheet by using a copper oxide paste by a screen printing method. The conductor paste is an organic binder in which 5 wt% of glass frit (# 7059 glass powder manufactured by Corning Inc., average particle size 3 μm) for obtaining adhesive strength is added to CuO powder (average particle size 3 μm) as an inorganic component. Ethyl cellulose was added together with a vehicle dissolved in terpineol, and mixed by a three-stage roll so as to have an appropriate viscosity. A predetermined number of the printed green sheets were prepared, thermocompression bonded to form a laminate, and fired by the method described below.

Next, the firing process will be described. The first is a binder removal step. The organic binders of the green sheet and CuO paste used in the invention are PVB and ethyl cellulose. Therefore, since the decomposition temperature in air should be 500 ° C. or higher, the temperature was 600 ° C. Then, the laminated body was reduced in an atmosphere of 100% hydrogen gas at 300 ° C. for 5 hours. When the Cu layer at this time was analyzed by X-ray diffraction, it was confirmed to be 100% Cu. A perspective view of the ceramic multilayer wiring board is shown in FIG. Reference numerals 11, 12, 13, and 14 denote laminated ceramic insulating layers, and reference numerals 15 and 16 denote conductors.

Next, the process conditions of the oxidation treatment process of the present invention were determined by the following experiments. First, a CuO green sheet containing an organic binder and a plasticizer is prepared. A desired number of sheets are laminated to form a CuO green sheet having a thickness of 2 mm. The CuO green sheet is cut into strips to form 2 × 2 × 15 mm pillars. The columnar material is heated in air under the same conditions as described above until the organic binder inside the CuO green sheet is decomposed and scattered. After that, the columnar material is reduced in hydrogen or 100% hydrogen atmosphere. At this time, when the reduced columnar material was analyzed by X-ray diffraction, it was confirmed to be 100% Cu. After the reduction, the weight of the columnar product is measured. Next, the columnar article is subjected to oxidation treatment with a dryer under the conditions shown in (Table 1), and the weight of the columnar article after oxidation is measured. The increase in weight is calculated from the above measurement results to obtain the degree of oxidation of the columnar material. The degree of oxidation O is defined as the degree of oxidation. The degree of oxidation O is defined as the increased weight (oxygen weight) converted into CuO and expressed as a molar ratio to Cu (100 fraction). The temperature settings and the degree of oxidation at that time are shown in (Table 1).

[0011]

[Table 1]

Next, the firing shrinkage curve of the oxidized columnar article was measured by a thermal analyzer. The measurement results are shown in (FIG. 3). This figure shows the relationship between firing temperature and shrinkage and C
It shows the relationship between the degree of oxidation of u and the shrinkage. The contraction rate ΔL / L of the substrate is defined as follows.

[0013]

[Equation 1]

As is clear from FIG. 3, the shrinkage ratio ΔL / L can be changed depending on the degree of oxidation in the oxidation treatment step after reduction. This makes it possible to deal with a substrate material having an arbitrary shrinkage ratio. In the example, from this experiment, it was decided to perform the oxidation treatment step on the reduced substrate under the condition that the oxidation degree was 31%. Next, in the firing step, firing was performed in pure nitrogen in a mesh belt furnace at 900 ° C. As a result, good results were obtained even when manufactured as a ceramic multilayer wiring board. Next, in the ceramic multi-layer wiring board manufactured according to the above process, the inner layer states of the ceramic multi-layer wiring board with oxidation treatment and the ceramic multi-layer wiring board with no oxidation treatment (FIG. 2a) and (FIG. 2b) are shown. Shown in.

FIG. 2A is a cross section of the ceramic multilayer wiring board when the oxidation treatment is performed, and FIG. 2B is a cross section of the ceramic multilayer wiring board when the oxidation treatment is not performed. A cavity as shown in the figure is generated in the cross section of the ceramic multilayer wiring board when the oxidation treatment is not performed.

As described above, according to the present invention, CuO is 3% to 3% of the total amount of the conductor Cu in the manufacturing process of the ceramic substrate.
By providing an oxidation treatment step for oxidizing in the range of 30 mol%, the shrinkage rate of the insulating material and the shrinkage rate of the conductor can be made close to each other, the matching property after firing becomes good, and the insulating material and the conductor can be matched. Adhesion is improved and effective.

In the present embodiment, the reduction was carried out in an atmosphere of 100% hydrogen, but it goes without saying that similar results can be obtained even in an atmosphere of hydrogen mixed with nitrogen. Further, it goes without saying that the present method can be applied to not only a ceramic multilayer wiring board but also a multilayer ceramic capacitor having copper as an internal electrode.

[0018]

The present invention is rich in the matching of the insulating material and the conductor by performing the above-mentioned steps,
A ceramic multilayer wiring board is obtained.

First, in the manufacturing method of the present invention, copper oxide is used as a conductor material, and a substrate material having a glass ceramic composition is also used as an insulating material to form a multilayer body, a binder removal step for removing the binder, and CuO. Is reduced to Cu, followed by an oxidation treatment step of slightly oxidizing Cu into CuO, and a firing step of firing the laminated body after the oxidation treatment.

In other words, by adding an oxidation treatment step, the conductor Cu is slightly oxidized, CuO is formed in a part of the Cu conductor, and the shrinkage ratio during firing can be controlled. As a result, the contraction rate of the insulating material and the contraction rate of the conductor can be matched, and the matching of the insulating material is improved. Moreover, it became possible to prevent the delamination by helping the reaction between the conductor layer and the substrate.

[Brief description of drawings]

FIG. 1 is a perspective view of a cross section of a copper multilayer ceramic substrate of the present invention.

FIG. 2 is a cross-sectional view showing an inner layer state of a substrate after firing.
(A) is sectional drawing at the time of adding the oxidation process of this invention. (B) is a cross-sectional view when the oxidation treatment step is not added.

FIG. 3 is a graph obtained by measuring the expansion coefficient of a columnar object of CuO that has been subjected to an oxidation treatment with a thermal analyzer.

[Explanation of symbols]

 11, 12, 13, 14 Ceramic insulating layer 15 Inner conductor 16 Outermost layer conductor 22 Insulating layer 21 Conductor layer 23 Cavity

Claims (2)

[Claims] 1. A step of forming a wiring pattern containing CuO as a main component on a green sheet and laminating a desired number of layers to form a multilayer, a reduction step of heat-treating in a reducing atmosphere to reduce CuO, and the green sheet. In the method for manufacturing a ceramic multilayer wiring board having a firing step of sintering in a non-oxidizing atmosphere, between the reducing step and the firing step,
A method for producing a ceramic multilayer wiring board, comprising an oxidation treatment step for partial oxidation so that the amount of CuO present with respect to the total amount of Cu is in the range of 3 to 30 mol%. 2. The oxidation treatment step is performed in air at 100 ° C. to 30 ° C.
The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein the method is performed in a range of 0 ° C.