JPH03285208A - Conductive paste - Google Patents

Abstract

PURPOSE:To make the sintering shrinkage timing of conductive paste agree with that of the material of a substrate to increase reliability by a method wherein conductive paste has an inorganic component containing glass frit and MgO powder in addition to CuO powder and an organic vehicle component made up of at least an organic binder and a solvent. CONSTITUTION:This conductive paste has an organic vehicle component made up of an inorganic component containing CuO powder at 87.0-99.4wt.%, glass frit at 0.5-10.0wt.% and MgO powder at 0.1-3.0wt.%, and an organic vehicle component made up of at least an organic binder and a solvent. Moreover, this conductive paste has an inorganic component containing CuO powder at 67.0-96.4wt.%, MgO powder at 0.1-3.0wt.% and at least one or more of Al2O3, SnO2, TiO2 and MnO2 at 3.0-20.0wt.%, and an organic vehicle component made up of at least an organic binder and a solvent. The amount of addition of MgO is 0.5-3wt.%. It is thereby possible to make the sintering shrinkage timing and the contraction volume of the conductive paste agree with those of the material of a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a conductive paste for circuit boards, and in particular to low-temperature fired ceramic multilayer wiring boards (hereinafter referred to as MLC).
It is abbreviated as ) and a conductive paste used as an electrode material for a pier hole.

Prior Art Conductor compositions applied to ceramic dielectric substrates include Au
, those using noble metals such as Ag/Pd, and those using precious metals such as Vv', M
Base metals such as O, Ni, Cu, etc. may be used. In particular, in MLC, a conductive pattern is formed by adding an organic binder and a solvent to this metal material to form a paste, which is screen printed onto an insulating substrate such as alumina, and then baked. In addition to these conductor pastes, ceramic multilayer boards can also be multilayered by using ceramic or glass powder as insulating materials dispersed in a solvent containing an organic binder, or by using the above-mentioned insulating powders and organic binders. There is a method in which a pattern formed with the conductive paste is laminated on a green sheet made of a material such as the above to form a multilayer structure. Focusing on the metal conductor materials used in these, A
Although Ag/Pd can be fired in air, it is expensive because it is a noble metal. On the other hand, W, Ni, and Cu are base metals and are inexpensive, but the firing must be performed in a reducing atmosphere or a neutral atmosphere. Further, in the case of W and Mo, the firing is performed at a high temperature of 1500° C. or higher. Furthermore, in terms of reliability, Au
Solder erosion is a problem, and Ag/Pd has problems of high migration and conductor resistance.

Therefore, C
The composition of Cu paste is also disclosed in JP-A-56-93396.

The former describes a composition containing Cu powder and glass frit, and the latter describes a composition containing no glass frit.

However, there are also problems when using Cu. This is because firing the dielectric substrate using the Cu electrode creates a reducing or neutral atmosphere, making it difficult to decompose and remove the organic binder in the paste. This is because the binder does not decompose because the oxygen concentration in nitrogen is low, and it remains in the form of carbon, which adversely affects metallization performance. Conversely, if the oxygen concentration is high,
The Cu electrode becomes oxidized and diffuses into the dielectric and no longer functions as an electrode. Therefore, firing is performed by controlling and supplying a small amount of oxygen to the nitrogen atmosphere.

Then, the remaining carbon reacts with the copper oxide, causing blisters to occur in the electrode layer and causing poor matching between the electrode and the dielectric.

C+2CuO→Co2↑+2Cu As described above, Cu paste has many problems when using an organic binder.

) Therefore, in recent years, a new method for manufacturing a Cu electrode multilayer ceramic substrate using CuO as the starting material for the conductor material has been developed. That is, a step of forming a wiring pattern using a CuO conductor composition on a ceramic green sheet, and after lamination, thermally decomposing the organic residue in the CuO conductor composition and the ceramic green note by heat treatment in an oxidizing atmosphere;
It has a structure in which it is manufactured by a process of reducing Cu metal by heat treatment in a reducing atmosphere and a process of firing a ceramic substrate in a nitrogen atmosphere.

For example, Japanese Patent Application Laid-Open No. 61-26293, U.S. Patent No. 4.7
No. 95.512, also U.S. Pat. No. 4.863.6
It is disclosed in the specification of No. 83. According to this method of manufacturing a ceramic laminate, the organic binder in the insulating substrate and paste can be easily decomposed and removed, and good Cu metallization can be obtained.

Problems to be Solved by the Invention However, in the above configuration, the internal 1i of the MLC
When forming poles and pier holes, in order to reduce and sinter the CuO, a cavity 4 is created between each dielectric layer (green sheet) 2 and the internal electrode part 1 as shown in FIG. 2 by contraction of the metal Cu. occurs. Moreover, at the same time, a problem arises in that a cavity 4 is also generated in the gap between the peer hole electrode 3 and the dielectric layer 2. The former cavity is thought to occur because the timing of sintering contraction of the dielectric material and the Cu powder is not the same.
The latter is considered to be caused by a difference in shrinkage rate after sintering, in other words, a difference in volume after sintering (mismatch). When such a phenomenon occurs, there are disadvantages such as poor conduction between the internal electrode and the peer hole electrode, which significantly reduces reliability.

In view of the above problems, the present invention provides a highly reliable conductive paste for internal electrodes that has the same sintering shrinkage timing as the substrate material. Moreover, by controlling the sintered volume, a good conductive paste for pier holes is also provided.

Means for Solving the Problems In order to solve the above problems, the conductive paste of the present invention has the following features:
It consists of an inorganic component containing glass frit and MgO powder in addition to CuO powder, and an organic vehicle component consisting of at least an organic binder and a solvent.

In addition to CuO powder, one conductive paste contains glass frit, MgO powder, and A/20.

It consists of an inorganic component containing at least one of SnO2, Tie, and MnO2, and an organic vehicle component consisting of at least an organic binder and a solvent.

In particular, the former conductive paste is suitable for internal electrodes, and the latter is suitable for peer hole electrodes.

Function: According to the present invention, by using the CuO paste having the above-mentioned structure in making a ceramic laminate, it is possible to obtain good matching properties with the ceramic material.

The CuO paste of the present invention can be prepared by adding glass frit and MgO in addition to CuO, or by adding Al2O3 in addition to CuO.
, SnO2°T i 02. It is obtained by adding at least one kind of Mn02. The conductive paste of the present invention is mainly applied as a ceramic laminate to multilayer ceramic wiring boards (MLC), etc. For MLC, the CuO paste of the present invention can be used as a ceramic laminate by adding the above-mentioned additives to prevent sintering with the substrate material. It is possible to match the contraction timing and contraction volume and is suitable for integrating Cu and MLC.

Among the additives contained in the conductive paste of the present invention, Mg
As a result of various studies, it was found that O has the effect of inhibiting the sinterability of Cu powder. In other words, the Cu powder after the reduction process was sintered too early compared to the substrate material, which caused gaps and cracks in the ceramic layer, but by adding MgO, the substrate material The sintering reaction begins to occur near the sintering temperature, and the C of the present invention
The above-mentioned problems do not occur with the u○ composition. At this time, if the amount of MgO added is less than 0.1% by weight, the effect is small and the generation of cavities cannot be suppressed. Moreover, if it is more than 3% by weight, the sintering timing will be too slow, causing cracks to occur in the ceramic layer. Therefore, it is preferably 0.5 to 3%. Also, Al2O3°SnO2, Tio2. By simultaneously adding additives such as MnO□, the volumetric shrinkage of the electrode layer after sintering is not much different from that of the ceramic substrate material. As a result, good metallization can be obtained in electrode layers such as pier holes, and pier holes with good performance can be formed. Further, if the total amount of these additives is less than 3% by weight, volumetric shrinkage of the electrode layer cannot be suppressed. Therefore, a cavity is formed in the gap between the peer hole and the ceramic layer. Conversely, 20% by weight
Above this, the shrinkage of the conductor layer is too small, resulting in poor matching performance with the sintered body. Also, the impedance of the conductor layer becomes significantly high, which is not good. Preferably the additive is 10
~15% by weight is good.

EXAMPLE Hereinafter, a multilayer ceramic wiring board according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a multilayer ceramic wiring board in a first embodiment of the present invention. In FIG. 1, 1 is an internal electrode, 2
3 is a dielectric layer, and 3 is a peer hole electrode layer.

The material used for the ceramic multilayer substrate of the present invention is borosilicate glass (#7059 manufactured by Corning Inc.) as a glass component.
A mixture of alumina powder and alumina powder in a weight ratio of 50:50 was used as a ceramic component. Next, the substrate material powder was used as an inorganic component, polybutylbutyral was used as an organic binder, di-n-butyl phthalate was used as a plasticizer, and a mixed solution of toluene and isopropyl alcohol (30:70 weight ratio) was added as a solvent as shown in Table 1. The composition was mixed to make a slurry.

Table 1 Dielectric composition, green sheet composition After thoroughly mixing this slurry, a film was formed on an organic film using a doctor blade method to form a green sheet. The film thickness after drying was approximately 200 mm. Pier holes are punched into this green sheet using a mold as needed. The pier hole diameter is
It was 0.2 Pengφ.

Next, the conductive paste was made of cupric oxide powder (average particle size 3 μm).
) was prepared by mixing glass frit and various additives in the composition shown in Table 2 to obtain adhesive strength.

The method for producing the conductive paste of the present invention is to add ethyl cellulose, which is an organic binder, to the inorganic powder having the above composition along with a vehicle dissolved in terpineol, and knead the mixture using three-stage rolls until a suitable viscosity is obtained.

The conductive paste thus obtained is printed on the green sheet by screen printing, and after drying, a desired number of heat and pressure are applied to laminate the sheets. Thereafter, heat treatment was performed in air for 30 minutes to remove pine mites. The temperature for debinding was 600°C. Next, as a reduction step, reduction treatment was performed at a temperature of 450° C. for 1 hour in a nitrogen atmosphere containing 10% hydrogen. and finally 10 in nitrogen atmosphere.
Bake for a minute. The firing temperature was 900°C. Each heat treatment is performed automatically in a Messiniherd furnace.

The metallization performance of the internal electrode portion of the completed MLC substrate was evaluated based on the sheet resistance value (converted to a film thickness of 10 μm). In addition, the effect of suppressing hollowing of the internal electrodes and the state of burying the electrodes in the peer holes were evaluated as peer hole matching properties. The evaluation of the cavity was expressed by the ratio of the thickness of the cavity to the film thickness of the internal electrode. That is, if there were no cavities at all, it was rated as Δ up to 10% of the film thickness of the 01 internal electrode, and if there were more cavities, it was rated as X. Since the evaluation of the peer hole matching property cannot be expressed quantitatively, it was evaluated visually using SEM observation. The above results are shown in Table 2. As is clear from Table 2, it is clear that the addition of MgO is effective in suppressing cavitation. Also, as additives Al2O3, SnO2, 'ri
o2. It can be seen that even when Mn0z is added, it is similarly effective on the matching properties of peer holes. Particularly in the case of this example, the conductive paste to which MgO is added is suitable for internal electrodes of the MLC, and the conductive paste to which Al2O3 is added as other additives is most suitable as a conductive paste for burying peer holes.

Effects of the Invention As described above, the CuO paste of the present invention can be prepared by adding glass frit and MgO in addition to CuO, or by adding A l 203 , S n 02 , T i
By adding at least one of 021M n O2, the sintering shrinkage timing and shrinkage volume can be matched with the substrate material, making it suitable for integrating Cu and MLC. This provides an MLC with more reliable Cu internal electrodes and peer holes.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the internal electrodes and peer holes of an MLC manufactured using a conductive paste according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the internal electrodes and peer holes of an MLC manufactured using a conventional CuO paste. . 1... Internal electrode, 2... Dielectric layer, 3
...Pier hole electrode layer, 4...Cavity part.

Claims (2)

[Claims] (1) 87.0-99.4% by weight of CuO powder, 0.5-10.0% by weight of glass frit, and 0.1% by weight of MgO powder.
A conductive paste comprising an inorganic component containing ~3.0% by weight and an organic vehicle component consisting of at least an organic binder and a solvent. (2) 67.0-96.4% by weight of CuO powder, 0.5-10.0% by weight of glass frit, and 0.1% by weight of MgO powder.
~3.0% by weight, further Al_2O_3, SnO_2,
3. At least one of TiO_2 and MnO_2.
A conductive paste comprising an inorganic component containing 0 to 20.0% by weight and an organic vehicle component consisting of at least an organic binder and a solvent.