JPS5889702A - Conductive paste - 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 The present invention relates to a conductive paste, and an object of the present invention is to provide a conductive paste that is inexpensive and has excellent conductivity and corrosion resistance.

Conventionally, noble metals such as Au, Ag, and Pd have been used as conductive powder in this type of conductive paste. Generally, muq is used as the conductive powder, and pbo is used.

The main components are Bi2O5 and ZnO, and also B2O3,5i
A paste dispersed in a vehicle together with a glass frit containing O2゜Q203 and the like is applied to a ceramic substrate by a method such as screen printing, and then fired at a high temperature to produce ceramic capacitors and piezoelectric elements.

It has been used as an electrode for semiconductor ceramics and as a wiring conductor for electronic circuits.

However, in recent years, due to the rise in the price of precious metals, especially Aq, as an alternative to conductive paste, conductive paste using inexpensive conductive powder, and Cu and Ni plating are used as electrodes for ceramic baking. Many proposals have been made, including electrodes. For example, as a substitute for Ag powder, inexpensive base metal powder such as Ni or Cu, or TiN,
Conductive 6-strokes using conductive metal compound powder such as SnO2 have been developed and are now commercially available in some cases.

However, since the powder itself of conductive pastes such as TIN and 5n02 is a material with relatively high resistance, it is difficult to obtain conductive pastes with low resistance.
N has the disadvantage that it cannot be used in high-temperature baking type conductive pastes because it oxidizes when baked in the atmosphere. In addition, as a product using oxide powder, MuQ20
There is also a conductive paste using a conductive powder coated with 5 powder, but this type of conductive paste has the disadvantage that the conductive film after firing has no solderability. On the other hand, Ni,
Conductive pastes using base metal powders such as Cu are difficult to sinter in the atmosphere, and Cu-based pastes have drawbacks in corrosion resistance.

On the other hand, as a method for improving the oxidation of Ni in high-temperature atmosphere, it is known to add B to Ni. N1-
Alloy B generates less oxide scale even when heated in an oxidizing atmosphere.

This is B20 on the surface. It is thought that a thin layer of oxidation is generated to prevent the progress of oxidation of the alloy. However, it does not reach the point where sufficient oxidizing properties are obtained as a conductive paste. Therefore, as a material with improved oxidation resistance, Si
There are proposals for pastes in which conductive powder is made of Ni-8t-B alloy powder.

Although this method is effective in improving the resistance value, it has the disadvantage that soldering properties are lost.

As mentioned above, various conductive pastes have been proposed as substitutes for muq, but all of them are unsatisfactory in terms of conductivity, corrosion resistance, or solderability. The emergence of a high-temperature baking type conductive paste is desired.

As a result of research and study on alloy powders mainly composed of base metals, the inventors of the present invention have found that Ni It has been found that an alloy containing B as the main component and to which B and an are added satisfies the above properties to a considerable degree.

The present invention will be explained in detail below.

In the conductive paste according to the present invention, the conductive powder is a Ni-B-8n alloy powder. Its composition ratio is 8
3-10% Sn, 3-15% Sn.

The remainder consists of Ni.

Presumably, the desired conditions for this type of conductive paste, especially the powder that serves as the conductive medium for high-temperature baking type conductive paste, are: (,) conductivity, ■) thermal oxidation resistance, (C) For example, it must be possible to solder.

Ni, which is the main component of the conductive powder in the present invention, is a metal with excellent conductivity, but it cannot be said to have good corrosion resistance and thermal oxidation resistance. In particular, it is unsuitable as a conductive medium for high-temperature baking pastes because a large amount of oxide scale is generated on its surface, making it impossible to obtain conductivity. It has been found that the addition of B and Sn improves the Ni −
In the paste using B-8n alloy powder as conductive powder, the SnO thin layer oxide combined with B strengthens the oxidation resistance, and on the other hand, in terms of conductivity, since 8n oxide is a semiconductor, it is not practical. suppressed to an acceptable range. On the other hand, regarding soldering properties, the addition of B produces a B2O5 film, so the fired film cannot be said to be good as it is, but if it is polished with Scotchbrite etc., the effect of the addition of Sn can be improved. This has been significantly improved and there is no problem in practical use.

In the present invention, the composition ratio at which the effect of adding Hi[B and Sn can be found is 83 to 10% by weight.

Sn is 3 to 16% by weight, and the balance is Ni. The lower limit of the amount added is the minimum amount at which the above-mentioned effect can be found. The upper limit is mainly limited by the ease of producing alloy powder, and if the amount of Sn is excessive, the Sn oxide film will become thick, leading to an increase in resistance value.

Next, in the present invention, when only the Ni-B-8n alloy powder is used as a conductive medium, the conductivity is often insufficient due to the characteristics of the fired paste film, and there are restrictions on its use. In order to compensate for this point, N1
- It is proposed to add Muq powder to B-8n alloy powder and use the mixed powder as a conductive hard body. The addition of muq powder further improves the conductivity and solderability of the fired conductive paste film.

Explaining the mixing ratio of N1-B-8n alloy powder and Mq powder, using Mq powder in addition to Ni-Sn-B alloy powder as a conductive medium improves conductivity,
Soldering makes it possible to improve the properties. The proportion of lii-B-an alloy powder in the conductive medium is 80%.
If the amount exceeds 20% by volume, the effect of adding the muq powder will be small, and if it becomes less than 20% by volume, the purpose of the present invention, which is to provide an inexpensive conductive paste, will not be met. The mixing ratio is Ni-B-an alloy powder amount 2
A range of 0 to 80 volumes is desirable.

According to the present invention, a Ni-B-Sn alloy powder or a mixed powder of this powder and Muq powder is used as a conductive medium of a conductive paste, but generally the powder is mixed with PbO. ,
It is dispersed in a vehicle and a glass frit consisting of Bi2O5, B2O5, 5t02, MuQ205, etc. to form a conductive paste. This paste is applied to a ceramic substrate by a method such as screen printing in the same way as a paste using ordinary muq powder, and then fired at a high temperature and used as an electrode or a conductive path.

The particle size of the powder is in the range of 0.06 to 10μ, preferably O,
Approximately S~6μ is good. When the thickness exceeds 10μ, printability during screen printing deteriorates, and surface resistance after final firing increases.

Next, examples will be described in detail in order to make the present invention more concrete.

The Ni-B-Sn alloy powder used in the present invention was produced as follows. according to the composition according to the invention) it-
Each material of B master alloy, LIT, and Sn was weighed, and the total amount was set to 19. This was dissolved in argon gas and further pulverized by a molten metal spray method. Nitrogen gas was used as the spray medium and cooled by cooling it in water.

The particle size of the obtained powder is about 6 to 100μ, but this is re-pulverized using a mechanical crusher, and the average particle size is about 2.
The Ni-B-Sn alloy powder obtained by the above method was weighed to a total amount of 3q. In addition, when mixing muq powder with this alloy powder, weigh the muq powder (flat particle size approximately 2μ) so that the predetermined mixing ratio is obtained, and the total amount is 39. . This is ethyl cellulose (1oocps)
and terpineol were kneaded together with Gmu-6 (manufactured by Nippon Electric Glass Co., Ltd., lead borosilicate glass frit) using a Hubermala. The amount of metal powder was 80% by weight of the total amount, and kneading using a Funoku-Mate was repeated 4 times at a load of 10 mm and 40 revolutions.

The paste prepared above was printed in a predetermined shape on an alumina substrate using a screen printing method, and then 120C
The film was dried at 850° C. for 10 minutes in the air, and then fired under the conditions of a 1-hour cycle including temperature increases and decreases before and after that for 10 minutes.

As a result of measuring the resistance value between both ends of the above firing pattern, the values shown in the following table were obtained. For reference, the table shows the properties of the fired films prepared using Muq powder, Ni powder, and mixed powder of Ni powder and Muq powder prepared by the same method. is also shown in the same way.

Regarding solderability of the fired film surface, after polishing with a Scotch Bride roll, 230℃ 501
50 an - Apply pine tar flux to the Pb bath 3
The solder was immersed for seconds, and the adhesion ratio of the solder to the turn surface was evaluated in three grades: ◯, △, and ×.

(The following is a blank space) As is clear from the above table, the conductive paste according to the present invention exhibits values comparable to the conventional paste using muq powder. On the other hand, pastes using Ni powder are not completely satisfactory.

As explained above, the conductive paste according to the present invention is
Since it has sufficient performance for practical use and can be produced economically by reducing muq, its industrial value is considerable.

Claims (1)

[Claims] 0) 83-10% by weight, Sn 3-15% by weight, balance Ni
A conductive paste characterized by dispersing an alloy powder having the composition of the following in a vehicle together with a glass frit. (2) B3-10% by weight, Sn 3-15% by weight
, balance 20 to 80% by volume of alloy powder with a composition of Ni
A conductive paste characterized in that a mixed powder containing 80 to 20% by volume of solid powder is dispersed in a vehicle together with glass frit.