JPH06223621A - Conductor paste composition - Google Patents

Abstract

PURPOSE:To provide a low conductive resistance via electrode, which has no possibility of cavities inside via and ensures its adhesion to a via hole, for a ceramic multilayer wiring board which has an inside electrode made of copper and zero firing shrinkage in a plane direction. CONSTITUTION:Conductor for via has CuO powder as conductor material, inorganic components containing Cu powder of average size 5.0-20.0mum and composed of 30.0-70.0wt.% conductor material and 30.0-70.0wt.% crystallized glass ceramic powder with the glass transition temperature higher than the glass transition temperature of insulating material, and organic vehicle composed of at least organic binder and solvent. Conductor paste composition in which the Cu powder represents 10.0-60.0wt.% of the conductor material is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor paste composition for a circuit board, and more particularly to a conductor paste composition used as a via electrode material for a low temperature fired ceramic multilayer wiring board (hereinafter abbreviated as MLC). .

[0002]

2. Description of the Related Art A conductor composition applied to a ceramic dielectric substrate uses a noble metal such as Au or Ag / Pd.
Base metals such as W, Mo, Ni and Cu may be used. In particular, a ceramic multilayer wiring board is one in which an organic binder and a solvent are added to this metal material to form a paste, which is screen-printed on an insulating substrate such as alumina and baked to form a conductor pattern.

Further, in the ceramic multi-layer wiring board, in addition to these conductor pastes, a method in which ceramics or glass powder is dispersed as an insulating material in a solvent in which an organic binder is melted to form a multi-layer, and the above-mentioned insulation is used. There is a method in which a pattern formed of the conductor paste is laminated on a green sheet made of powder, an organic binder or the like to form a multilayer.

When attention is paid to the metal conductor materials used for these, Au and Ag / Pd can be fired in air, but they are expensive because they are precious metals. On the other hand, W, Mo, Ni, Cu
Is a base metal and is inexpensive, but it is necessary to perform the firing atmosphere in a reducing atmosphere or a neutral atmosphere. In addition, in W and Mo, high temperature firing of 1500 ° C or higher is performed. Further, in terms of reliability, solder erosion becomes a problem with Au, and with Ag / Pd,
There is the problem of high migration and high conductor resistance.

Therefore, Cu, which is inexpensive, has a low electric resistance, and has a good solderability, has come to be used.

For example, US Pat. No. 4,072,771 describes Cu
The composition of the paste is also disclosed in JP-A-56-93396. The former describes a composition containing a glass frit in Cu powder and the latter a composition containing no glass frit.

However, there are problems in using Cu. This is because the firing of the dielectric substrate by the Cu electrode reduces or becomes a neutral atmosphere, and it becomes difficult to decompose and remove the organic binder in the paste. This is because the oxygen concentration in nitrogen is low, so that the binder does not decompose and remains in the form of carbon, which adversely affects the metallization performance. On the other hand, when the oxygen concentration is high, the Cu electrode is oxidized and diffuses into the dielectric, so that it does not function as an electrode. Therefore, firing is performed by supplying a small amount of oxygen while controlling it in a nitrogen atmosphere. Then, the remaining carbon reacts with the copper oxide to generate blisters in the electrode layer or cause deterioration of the matching between the electrode and the dielectric. Like this
Pastes have many challenges in using organic binders.

Therefore, in recent years, a new method of manufacturing a Cu electrode ceramic multilayer wiring board using cupric oxide (CuO) as a starting material of a conductor material has been developed. That is, a wiring pattern is formed of a CuO conductor composition on a ceramic green sheet, and after stacking, the Cu is subjected to a heat treatment in an oxidizing atmosphere.
C in the step of thermally decomposing the organic residue in the O conductor composition and the ceramic green sheet and the heat treatment in the reducing atmosphere.
It is composed of a step of reducing to a metal and a step of firing a ceramic substrate in a nitrogen atmosphere.

For example, it is disclosed in US Pat. No. 4,795,512 and US Pat. No. 4,863,683. According to this method for manufacturing a ceramic laminate, it is easy to decompose and remove the organic binder in the insulating substrate and the paste,
And good Cu metallization can be obtained.

As the conductor composition for vias used in the method for manufacturing the ceramic laminate, in order to match the firing shrinkage of the substrate and the vias, in addition to CuO powder, glass frit, MgO powder, and Al. ₂ O ₃ , SnO ₂ , Ti
It has been proposed that a conductor paste containing an organic vehicle component and an inorganic component containing at least one of O ₂ and MnO ₂ be used.

The ceramic multi-layer wiring board shrinks due to sintering during firing. The shrinkage due to this sintering is not only the management of the substrate material and the green sheet composition used,
Even if the powder lots are different and the lamination conditions (press pressure, temperature) are well controlled, it is said that shrinkage error of about ± 0.5% still exists. A method of manufacturing a ceramic multilayer wiring board which solves this problem and uses copper for the inner conductor and has zero shrinkage in the planar direction has been proposed.

Further, after laminating a desired number of green sheets made of glass / ceramic containing at least an organic binder and a plasticizer having an electrode pattern formed of a conductor paste composition containing CuO as a main component, the firing temperature of the glass / ceramic is set. Then, green sheets made of an inorganic composition that does not sinter are laminated on both sides or one side of the glass-ceramic laminate, and these are heat-treated in air at a temperature at which the organic binder inside the multilayer decomposes and scatters. After that, reduction heat treatment is performed in an atmosphere of hydrogen or a mixed gas of hydrogen and nitrogen, and further, the reduction heat treated multilayer body is sintered in a nitrogen atmosphere, and thereafter, the inorganic composition that is not sintered is removed. A method for manufacturing a ceramic multilayer wiring board has been proposed.

Further, in the above-mentioned ceramic multilayer wiring substrate having no shrinkage in the plane direction, since the firing shrinkage of the via occurs only in the vertical direction (the thickness direction of the substrate), the reliability of the dense structure which is surely adhered to the via hole is reliable. As a highly conductive via conductor, C
Proposal that it is appropriate to use a conductor paste composition including an inorganic component composed of a conductor material such as uO and a crystallized glass ceramic powder having a glass transition temperature higher than that of an insulating material, and an organic vehicle component Has been done.

[0014]

However, when the above-mentioned conductor paste for vias is used in the production of a ceramic multilayer wiring substrate which does not cause shrinkage in the planar direction, using CuO as a starting material for the copper internal electrodes as described above. , A highly reliable via having a dense structure which is surely adhered to the via hole is formed, but there arises a problem that the conductor resistance of the via becomes high.

In view of the above problems, it is an object of the present invention to provide a conductor paste composition for vias, which forms a highly reliable via having a low conductor resistance and being surely adhered to a via hole and having a dense structure. .

[0016]

A conductor paste composition for vias according to the present invention contains cupric oxide (CuO) powder as a conductor substance and copper (Cu) powder having an average particle size of 5.0 to 20.0 μm. An organic vehicle comprising at least an organic binder and a solvent, an inorganic component comprising 30.0 to 70.0% by weight of the conductor substance, 30.0 to 70.0% by weight of a crystallized glass ceramic powder having a glass transition temperature higher than the glass transition temperature of the insulating material. And a copper (Cu) powder of 10.0 to 60.0% of the conductive material.
It is characterized by occupying weight%.

[0017]

According to the present invention, after the insulating material forming the via hole is sintered and the via hole is formed, the glass component in the via conductor material inside the via hole is softened and the via conductor is sintered. , A via conductor with a fine structure can be formed, which is surely adhered to the via hole without disconnection at the via conductor portion or voids inside the via hole. Also, since the conductor material contains Cu powder, only the conductor material is CuO. As compared with the above case, a via electrode having a lower conductor resistance can be formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic multilayer wiring board according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of a green sheet laminate of one embodiment of the present invention.

First, a method for producing a ceramic multilayer wiring board will be described.

The glass / ceramic substrate material is a composition in which glass powder is mixed with alumina powder as a ceramic material in a weight ratio of 50:50 (manufactured by Nippon Electric Glass Co., Ltd., MLS-2
7, glass transition temperature 520 ℃) was used. This glass-ceramic powder was 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) as a solvent was mixed and slurried.

This slurry was formed into a sheet having a thickness of about 200 μm on an organic film by a doctor blade method. At this time, a system was used in which each step of continuously drying, punching, and optionally processing a via hole was performed. The via hole diameter was 0.15 mmφ.

Next, as the internal electrode paste, Cu was used.
O powder (Kyoto Ellex Co., average particle size 3 μm), glass frit (Nippon Electric Glass Co., L
S-0803 glass powder, average particle size 2.5 μm) 3 wt% was added as an inorganic component, and an organic vehicle in which ethyl cellulose, which is an organic binder, was dissolved in terpineol was added, and a suitable viscosity was obtained with a three-stage roll. It was made by kneading.

As the via-hole electrode paste, CuO powder (manufactured by Kyoto Elex Co., average particle size: 3 μm), crystallized glass ceramic powder (manufactured by Nippon Electric Glass Co., Ltd., MLS05, glass transition temperature 670 ° C.), as an inorganic composition, Cu powder
(Fukuda Metal Foil & Powder Co., SRC, average particle size 15 μm)
As shown in, prepared by blending the Cu powder in various compositions, further adding an organic vehicle in which ethyl cellulose as an organic binder is dissolved in terpineol, and kneading with a three-stage roll until an appropriate viscosity is obtained. did. The conductor pattern was formed by using the above-mentioned conductor paste and the via-holes were filled and printed by the screen printing method.

[0024]

[Table 1]

Next, a green sheet that does not sinter is produced by using alumina (produced by Sumitomo Chemical Co., Ltd.) as an inorganic component.
ALM-41, average particle size 1.9 μm) powder only, with the same green sheet composition as the glass / ceramic substrate green sheet, and in the same manner as the green sheet (thickness 300
μm) was created.

A predetermined number of the glass-ceramic green sheets on which the conductor has been formed are stacked, and the alumina green sheets are further stacked on both sides thereof. In this state, thermocompression bonding was performed to form a laminate. The temperature for thermocompression bonding is 80
The temperature was 200 ° C. and the pressure was 200 kg / cm ² . FIG. 1 shows a cross-sectional view of the green sheet laminated body, 1 is a green sheet layer made of glass ceramic of the substrate material, 2 is an internal electrode layer,
Reference numeral 3 is a via electrode, and 4 is a green sheet layer made of alumina.

Next, the laminate was placed on a 96% alumina substrate and fired in the steps described below. The first is a binder removal step. The organic binders of the green sheet and CuO paste used in this example are polyvinyl butyral and ethyl cellulose. Therefore, the decomposition temperature in air should be 500 ° C. or higher, so the degreasing treatment of the laminate was performed at a temperature of 600 ° C. Then, the laminate was reduced at 200 ° C. for 5 hours in a 100% hydrogen gas atmosphere. When the Cu layer at this time was analyzed by X-ray diffraction, it was confirmed to be 100% Cu.

Next, in the firing step, firing was performed at 900 ° C. for 1 hour in pure nitrogen in a mesh belt furnace (holding time at 900 ° C. is about 12 minutes). At this time, in order to assist the warp of the substrate and the sinter contraction in the thickness direction, the alumina sintered substrate was placed and pressed so as to be fired. Since an unsintered alumina layer exists on the surface of the laminated body after firing, the alumina layer could be removed cleanly by ultrasonic cleaning in a butyl acetate solvent.

The substrate after firing did not warp, the shrinkage ratio of the substrate was 0.1% or less, and there was no warpage. The uppermost layer pattern was formed by screen printing on both surfaces of the substrate with a commercially available Cu paste (QP153, manufactured by DuPont), dried, and baked at 900 ° C. for 1 hour in the same manner as the above baking.

In the ceramic multilayer wiring board thus obtained, the resistance of the via electrode was measured, and the bondability between the via and the internal electrode pattern and the via structure were confirmed by SEM observation of the substrate cross section. The results are shown in Table 1, and as is clear from Table 1, the resistance of the via electrode decreased as the Cu content in the conductor material increased.

In addition, regarding the compounding compositions Nos. 1, 2, 3, and 4, there is no disconnection at the contact portion between the via conductor and the wiring conductor or a void inside the via hole, and the dense composition is surely adhered to the inner wall of the via hole. A via conductor having a different structure could be formed. However, if the proportion of Cu powder in the conductor material exceeds 60% by weight, the firing volume of the conductor composition filled in the via becomes larger than the via hole volume of the substrate after firing, and the disconnection between the internal wiring conductor and the via electrode occurs. occured. The reason why the resistance value of the via in the composition No. 4 was slightly higher than that of the via of the composition No. 3 is considered to be due to the volume mismatch between the via hole and the via conductor.

A ceramic multilayer wiring board was manufactured in the same manner by preparing the via conductor paste in which the ratio of the conductor substance to the glass ceramic was changed. At this time, in the case of using the via conductor paste (there is a large amount of glass-ceramic component) in which the ratio of the conductor material is not more than 30% by weight, voids inside the via hole do not occur, and the via hole inner wall is firmly adhered. A via conductor having a dense structure was formed, but conduction could not be obtained because the glass ceramic component was too much.

On the other hand, in the case of using a via conductor paste (having a small glass-ceramic component) in which the ratio of the conductor substance exceeds 70% by weight, voids are formed inside the via hole or in the via-internal electrode pattern joint portion due to sintering shrinkage of the conductor. Occurred and a disconnection was also seen.

Also, a ceramic multilayer wiring board was manufactured and evaluated in the same manner by preparing the via powder containing Cu powder having different particle diameters. When Cu powder with a particle size of 3.0 μm was used, the volume expansion was large when Cu was oxidized to CuO in the binder removal step of firing the substrate, resulting in delamination between layers and via electrode destruction. On the other hand, when Cu powder having a particle size of 30 μm is used, it is difficult to disperse the Cu powder in the paste,
In addition, the filling of the via holes with paste could not be sufficiently performed.

[0035]

As described above, in the conductor paste composition of the present invention, after the insulating material forming the via hole is softened and sintered to form the via hole, the conductive material in the via conductor inside the via hole is formed. Since the glass component softens and the via conductor sinters, disconnection at the via conductor portion and voids inside the via hole do not occur, and it is possible to form a highly reliable via conductor with a dense structure that firmly adheres to the via hole. . Further, since the conductor material contains Cu powder, a via electrode having a lower conductor resistance can be formed as compared with the case where the conductor material is only CuO.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a green sheet laminate according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Glass / ceramic green sheet layer, 2 ... Internal electrode layer, 3 ... Via electrode, 4 ... Alumina green sheet layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/46 S 6921-4E

Claims (1)

[Claims] 1. A conductor material comprising cupric oxide powder and copper powder having an average particle diameter of 5.0 to 20.0 μm, wherein the conductor material is 30.0 to
70.0% by weight, a glass-ceramic powder having a glass transition temperature higher than the glass transition temperature of the insulating material 30.0
A conductor paste composition comprising an inorganic component consisting of ˜70.0 wt% and an organic vehicle component consisting of at least an organic binder and a solvent, wherein the copper powder constitutes 10.0 to 60.0 wt% of the conductor substance.