JPS62198198A - Manufacture of ceramic multilayer interconnecting 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 a method of manufacturing a ceramic multilayer wiring board on which semiconductor LSIs, chip components, etc. are mounted and interconnected.

Conventional technology Ceramic multilayer substrates currently have three layers depending on their multilayering method.
It is classified into two methods. The first is the thick film printing method, which is typified by hybrid ICs.

This involves screen printing a thick film paste of a conductor or insulator on a sintered ceramic substrate and repeating firing each time to create a multilayer structure. The second method is the green sheet printing method, in which unfired ceramic powder is used as the substrate material with an organic binder, plasticizer, etc. This method uses a slurry made with 8 agents and a film formed into a sheet (referred to as a green sheet) using a doctor blade method. Conductor and insulator pastes are printed on this green sheet and firing is completed in one go. The third method is the green sheet one-layer method, in which a desired number of green sheets with conductive patterns formed on them are laminated and pasted together.A multilayer board can be obtained by firing once, similar to the green sheet printing method. It is something that can be done.

On the other hand, when focusing on conductive materials used in ceramic multilayer substrates, Au, Au-Pt, and Ag-Pt are used.

Those using noble metals such as Ag and Ag-Pd, and those using W, M
o, a high melting point metal such as Mo-Mn, and Cu.

It can be broadly classified into base metals with relatively low melting points such as Ni. First, noble metal pastes are widely used because they can be processed in air and have high reliability. However, precious metals have the problem of high cost. In addition, high melting point metals such as W, Mo, Mo-Mn, etc.
Since it is necessary to simultaneously fire at a high temperature of about °C, that is, at a temperature higher than the sintering temperature of the green sheet, it is suitable for multilayer formation, but on the other hand, it is dangerous because it needs to be fired in a reducing atmosphere. Further, the conductor resistance is high, and Ni or Au plating is required for soldering.

Therefore, materials such as Cu and Ni, which can be processed at low temperatures and are inexpensive, are attracting attention.

Therefore, an example of a method for manufacturing a ceramic multilayer wiring board using Cu paste will be described. The method involves screen printing Cu paste on a sintered substrate such as alumina to form a wiring pattern, and after drying, the temperature is below the melting point of Cu (
850 to 950° C.) and in a nitrogen atmosphere in which the oxygen partial pressure is controlled so that the Cu is not oxidized and the organic components in the conductor paste are sufficiently combusted. When multi-layered, the insulating layers are printed and fired under the same conditions.

However, when using the above-mentioned Cu paste, there are some problems. First of all, it is difficult to control the atmosphere in the firing process to an appropriate oxygen partial pressure. If there is too much oxygen, Cu will be oxidized, and if there is too little oxygen, the organic binder in the paste will not be decomposed and removed, and good metallization will not be obtained.Secondly, when creating multiple layers, after printing each paste, It is necessary to repeat firing, which increases lead time.
This has problems such as increasing the cost of equipment. Therefore, in the production of a ceramic multilayer substrate in Japanese Patent Application No. 147833 of 1983, the process of removing pine mites,
A method having three steps, a reduction step and a calcination step, has already been disclosed. It is a reduction process in which cupric oxide is used as the starting material for the conductor, and the depinemization step is carried out in an oxidizing atmosphere sufficient for carbon and at a temperature sufficient to thermally decompose the internal organic binder, reducing it to cupric oxide. This method consists of a firing process in which the substrate is sintered. This makes it easier to control the atmosphere during firing and allows a dense sintered body to be obtained.

Problems to be Solved by the Invention However, the following problems have become apparent. This is because there is a limit to the materials that can be used as the insulating material for green sheets, which is the substrate material, in the production of ceramic multilayer substrates. This is because, in the manufacturing method that uses cupric oxide as a starting material and includes a heat treatment process in a reducing atmosphere as described above, the insulating material (glass-ceramic) contains a metal oxide (PbO) to be reduced. and P b O+ a M e −+ P b + M e
a 0Me: Another metal reaction occurs, including metallized PB! ! ! The I edge layer no longer functions as an insulator. Therefore, when using a base metal such as Cu as a conductive material, the insulating material should be Al2O3 or BtOs+, which are metal oxides that are thermodynamically stable and do not cause oxidation or reduction reactions with Cu.
Bad, Sioz, Cab, NazO.

It should be selected from MgO, TatOs, NbzOs, etc. On the other hand, it is said that low-temperature sintered substrate materials containing PbO, TtOz, etc. cannot be used. However, substrate materials made of non-PbO-based oxides as described above have many disadvantages. For example, the above materials tend to have low insulation resistance and poor dielectric loss (tan δ). In addition, it is known that the softening point tends to be relatively high, and such systems have problems such as difficulty in lowering the sintering temperature and difficulty in short-term firing. . On the other hand, since the top layer wiring of the multilayer body after sintering uses cupric oxide as a starting material, volume reduction (CuO-*Cu) occurs during the reduction treatment process, resulting in a large number of cranks on the electrode surface. Therefore, the electrode cannot be called dense. For the wiring in the top layer where the highest reliability is required, the one using CuO as a starting material is not optimal.

Means for Solving the Problems In order to solve the above problems, in the method of manufacturing a ceramic multilayer wiring board of the present invention, it is possible to use lead-based glass as an insulating material, which is highly reliable and suitable for mass production. This can be obtained by configuring the manufacturing process conditions as desired. In other words, the purpose of this study was to examine in detail the conditions of each step in the manufacturing process and achieve both non-reduction of lead oxide and reduction of cupric oxide.

Further, the conductor paste for the uppermost layer wiring is mainly composed of metallic copper, and is formed after the reduction of the multilayer body, and the firing of the multilayer body and the firing of the uppermost layer conductor are performed simultaneously in nitrogen.

Function The present invention consists of the manufacturing method and manufacturing process conditions as shown below, and is an insulating material containing lead-based glass that is highly reliable in terms of electrical insulation and can be fired at low temperatures and in a short time. This is a ceramic multilayer substrate that enables the use of

The present invention will be explained in detail below.

First, to explain the manufacturing method of the present invention, there is a step of forming a multilayer body using cupric oxide as a conductive material and a low-temperature sintered material containing lead-based glass as an insulating material, and a depinemation process to remove the binder. The process consists of a reduction process in which CuO is reduced to Cu, a top layer Cu conductor printing process in which the top layer wiring is formed using Cu paste, and finally a firing process in which the multilayer body and the top layer wiring are simultaneously fired.

In the depinemation process, the organic binder in the substrate is decomposed and removed in an oxidizing atmosphere such as air at a temperature below the softening point of the insulating glass. Then, in the reduction step, cupric oxide is reduced. As described above, since heat treatment in a reducing atmosphere is included in the manufacturing process, it has conventionally been said that insulating materials containing metal oxides that are reduced by heat treatment in a reducing atmosphere cannot be used. However, as a result of repeated studies from various viewpoints, the inventors found that by setting the conditions for each process of reduction and firing to certain values, it is possible to prevent lead oxide from being reduced to metallic lead and to reduce it to copper. I found out.

In other words, after removing the binder from the unsintered multilayered body in which a conductor pattern was formed using cupric oxide, we conducted an experiment to determine the temperature at which it could be reduced to metallic copper. The reduction reaction occurred at about 250°C in an atmosphere containing . Also, at this temperature, the Pb contained in the multilayer body
O was not reduced to pb. Next, when the reduction temperature was gradually raised in the same atmosphere, it reached approximately 600℃ or higher.
It was found that Pb reduction occurred simultaneously with Cu reduction.

In addition, when reducing at 250°C, depending on the heat treatment time, some parts may remain that are not reduced to copper. Conversely, if the temperature is high, the glass softening point is exceeded and the inner layer remains as cupric oxide before being sufficiently reduced to steel. Therefore, the practical effective range is between 300 and 500°C.

After sufficient reduction is completed, the top layer wiring is made of metal C.
Print with a paste whose main ingredient is U powder.

In the firing process, the Cu paste and the insulating material are fired simultaneously in a neutral atmosphere such as nitrogen. As a result, PbO in the insulating material is not reduced and exhibits a good insulating function. Furthermore, the uppermost Cu layer, which is co-fired with the insulating material, is also dense and provides good metallization properties.

Examples are shown below.

Example First, alumina 9 was used as a ceramic sintered substrate according to the present invention.
6% (96A 1 z 03 ) was used. (thickness 0
．． 8. 1) Next, the conductor paste for the inner layer is cupric oxide powder (
The inorganic component is 5 wt% of glass frit (manufactured by Corning, #70593μm average particle size) to improve adhesive strength, and the organic binder ethylcellulose is dissolved in terpineol. In addition, the material was kneaded using three-stage rolls to obtain an appropriate viscosity.

Next, the insulating paste used was one in which an insulating material having the composition shown in Table 1 containing lead-based glass was used as an inorganic component, and a vehicle was added and kneaded in the same manner as the conductive paste.

The insulating material is manufactured by first melting it at a high temperature so that it has the glass composition shown in Table 1, then dropping it into water to rapidly cool it, and then grinding it wet to an average particle size of about 2 μm. Further, alumina powder having an average particle size of 0.8 μm is mixed as a ceramic material to obtain an inorganic powder.

A multilayer body is produced using the inner layer conductor paste produced as described above and the insulating paste. In this method, a wiring pattern is formed on the alumina substrate by screen printing using a conductive paste for the inner layer, and after drying, an insulating paste is further screen printed on top of the wiring pattern. This step is repeated a predetermined number of times to produce a multilayer body. In case of , 2, the top layer wiring is not printed, and an insulating layer with via holes for necessary connections is formed on top. A cross-sectional view of the multilayer body thus obtained is shown in FIG. In the figure, 1 is C
2 is an insulating layer, and 3 is an alumina substrate.

Next, the binder from this unsintered multilayer body is removed.

The softening point of each insulating glass used in this example was 6.
These temperatures are 26°C, 619°C, and 630°C, and it is necessary to remove the binder at a temperature below the softening point. Further, since the residual binder contained in the conductor and wA edge paste used in this example is ethyl cellulose, a temperature of about 550° C. or higher is desired for decomposition and removal in air. Therefore, the binder was removed at 600°C. The profile is shown in FIG.

Note that if the binder is removed at a temperature higher than the softening point, there is a risk that the cupric oxide inside will be sealed with the insulating material, so that it will not be possible to reduce it to Cu even in the subsequent reduction step. Also,
The decomposition and removal of ethyl cellulose, which is a binder, was carried out based on the results of thermal analysis, and it was also confirmed from the results of carbon content analysis after binder removal that sufficient removal was carried out. Next, the profile of the reduction process is shown in FIG. The binder-removed laminate was inserted into a 1201 mm diameter tube furnace, and nitrogen gas was introduced at a flow rate of 0.71/min and hydrogen gas was introduced at a flow rate of 0.7/min. The reduction temperature is
200℃, 300℃, 400℃, 500℃, 600℃.

Each temperature was maintained at 700° C. for 1 hour, and then taken out after cooling.

Reduction to copper almost occurs at temperatures other than 200°C, and at 30°C.
At 0°C, there is some presence of cupric oxide inside. There were some parts that appeared black, and it cannot be said that the reduction was carried out sufficiently.

Further, at a reduction temperature of 600° C. or higher, the insulating layer turned gray, indicating that pbo was reduced. From the above results, a temperature between 300°C and 500°C is suitable for the reduction step, and strictly speaking, a temperature between 400°C and 500°C is optimal.

Next, the metallic copper paste (
A wiring pattern was screen printed using Dupon Co., Ltd. (#9153) and dried (120° C. for 10 minutes).

The final calcination step was carried out continuously in a Metschwerd furnace in pure nitrogen. (200mm manufactured by BTU Engineering Co., Ltd.
(width belt furnace) The residual Ot inside was measured using a 02 densitometer and was found to be 0□ amount of 1 to 2 pp+w. An example of the temperature profile is shown in FIG.

The sintering of the reduced multilayer body and the top NCu metallization will be formed simultaneously.

The structure of the multilayer wiring board obtained as described above is shown in FIG. 2, and the evaluation results are shown in Table 2. 4 is a Cu metallized layer produced according to this example.

Table 2 Various properties of ceramic multilayer substrate As shown above, practically sufficient results were obtained. In addition, in terms of manufacturing conditions, the firing time is short, about 1 hr, and simultaneous firing is possible, so it can be said that the manufacturing method is highly suitable for mass production.

Among the evaluation methods, the adhesive strength was measured by forming a polar pattern of two square Cu1 on the ceramic multilayer substrate produced as described above, and placing lead wires (0,8
mmφ) were vertically soldered and their breaking strength was measured using a tensile tester.

Effects of the Invention As described above, the manufacturing method of the present invention provides an extremely reliable ceramic-copper multilayer substrate in which lead-based glass can be used as an insulating material. In other words, lead-based glass generally has high insulation resistance and is said to have excellent dielectric properties, and it is also possible to lower the softening point, making it easy to bake in short times and at low temperatures, making it an extremely suitable insulation for mass production. It can be said to be a material. Furthermore, by forming the top layer wiring after the reduction process as in the present invention, it is possible to perform the firing at the same time as the sintering of the insulating material, which improves metallization properties (
Cu has excellent adhesive strength, solderability, and surface density.
Wiring is what you get.

Furthermore, the copper metallization obtained by the manufacturing method of the present invention has Cu's low conductor resistance, good soldering properties,
This is an industrially extremely effective invention that can fully demonstrate the advantages of good migration resistance and low cost.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a ceramic multilayer board after printing and drying according to the present invention, Fig. 2 is a sectional view of the completed ceramic multilayer wiring board after forming the uppermost layer wiring and firing, Figs. , and FIG. 5 are schematic diagrams showing the temperature profiles of the depine mite step, the reduction step, and the firing step, respectively. 1... CuO layer, 2... Insulating layer, 3...
...Alumina substrate, 4...Cu metallized layer Name of agent Patent attorney Toshio Nakao Haka1 person / =
-CttO layer / Z etc. 2 Fig. 4--c Brittle metallized layer

Claims (1)

[Claims] A pattern is printed on a sintered ceramic substrate with a paste composition mainly composed of cupric oxide, and a pattern is further printed with an insulating paste made of a glass-ceramic composition containing lead oxide. A process of repeating printing the insulating paste on one or both sides of the sintered ceramic substrate a desired number of times to form a multilayer, and exposing the multilayer body to a temperature sufficient to cause the organic components inside the multilayer body to decompose and scatter in the air. Thereafter, a step of performing a reduction heat treatment at a temperature between 300° C. and 500° C. in an atmosphere containing a mixture of hydrogen and nitrogen, and adding metallic copper to the top layer of the reduced multilayer body. A method for manufacturing a ceramic multilayer wiring board, comprising the steps of forming a top layer wiring by printing paste and sintering it in a pure nitrogen atmosphere.