JPH02207588A - Metallized paste and manufacture of ceramic circuit board using same - Google Patents

Abstract

PURPOSE:To preferably use copper as a conductor for metallized paste for simultaneous firing of ceramics at low temperature by employing as conductor powder plated powder yield by applying plating with oxidization resistance and heat resistance to copper powder. CONSTITUTION:Copper powder is stirred in alcohol, washed, and dispersed, and is then transferred into a gold plating solution kept at 70 deg.C. The copper powder in the solution is stirred with addition of a reducing agent for plating. The copper powder after so plated is taken out and washed to provide gold- plated copper powder. The resulting gold-plated copper powder is dispersed in a vehicle comprising an organic solvent and an organic binder to provide metallized paste, which paste is in turn subjected to screen printing on a glass ceramic green sheet. A plurality of those sheets are laminated by thermocompression bonding. The resulting laminate is unbound in the oxidative atmosphere at 300-400 deg.C to complete burn the binder in the green sheet without oxidizing the involved copper.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a metallization paste used in co-firing a low-temperature fired ceramic circuit board and a method for manufacturing a ceramic circuit board using this metallization paste.

(Background Art) In low-temperature fired ceramic circuit boards fired at about 1000°C, metallization pastes used when simultaneously firing the board and conductor parts have conventionally been made of gold, silver, silver/palladium, etc. as conductors. Those that do are used. This is because gold and silver are stable against heating and have excellent electrical properties as conductors.

However, gold is expensive, and silver threads have problems with electromigration and lack reliability in conductor parts, so copper is used in some cases as a conductor instead. Copper is inexpensive and has better conductivity than gold as a conductor. However, copper begins to oxidize at about 120 to 150°C, and is far more easily oxidized than gold or silver, and has the disadvantage that its conductivity decreases due to oxidation. Therefore, when used in co-firing a ceramic circuit board, it is necessary to prevent copper from oxidizing.

When firing ceramics, the binder is removed from the green sheet in an oxidizing atmosphere at 300 to 400°C, and then the temperature is raised and fired, but when copper is used as the conductive powder in the metallizing paste, In order to avoid oxidation, it is necessary to remove the binder in a non-oxidizing atmosphere with an oxygen concentration of several ppm or less. However, there is a problem in that the organic binder contained in the green sheet is not completely burned in a non-oxidizing atmosphere, and the organic binder becomes carbon and remains in the ceramic. As described above, when a metallizing paste containing copper as conductive powder is used, there is a difficulty in avoiding oxidation of the copper.

Therefore, the present invention solves this problem and provides a metallization paste in which copper can be suitably used as a conductor in a metallization paste for simultaneous firing of low-temperature fired ceramics, and a ceramic circuit board fired using this metallization paste. The present invention aims to provide a method for manufacturing.

(Means for solving problems) The present invention has the following configuration to achieve the above object.

In other words, in a metallizing paste used in the simultaneous firing of a low-temperature firing ceramic circuit board made by adding an organic solvent and an organic binder to a conductive powder, the conductive powder is a copper powder that is oxidation resistant at 300 to 400°C. It is characterized by using a plated copper powder which is plated with heat resistance and heat resistance, and is particularly effective when the plated copper powder is a gold-plated copper powder which is formed by plated copper powder with gold. .

Also, as a method for manufacturing ceramic circuit boards.

A metallized paste made by plating copper powder with oxidation resistance and heat resistance at 300 to 400°C and adding an organic solvent and an organic binder to the plated copper powder,
After coating on a low-temperature fired ceramic green sheet and removing the binder by heating the green sheet to 300 to 400°C in an oxidizing atmosphere, it is fired at a predetermined ceramic substrate firing temperature in a non-oxidizing atmosphere. It is characterized by

(Function) As the conductor powder of the metallized paste, plated copper powder is used to prevent the copper powder from being oxidized during heating in an oxidizing atmosphere by using plating treatment on the copper powder to have oxidation resistance and heat resistance. As a result, the binder can be removed from the green sheet in an oxidizing atmosphere, and the binder component can be sufficiently removed. Further, since copper is used as the main component of the conductor powder, by using the metallization paste, a conductor portion having good conductivity can be obtained in a ceramic circuit board.

[Example 1] Hereinafter, preferred embodiments of the present invention will be described in detail.

Gold plating was applied to the copper powder used as the conductor of the metallized paste as follows.

Spherical copper powder with a particle size of 1.0 to 2.0 μm was used as the copper powder. This copper powder was stirred in alcohol, washed and dispersed, and then placed in a gold plating solution kept at 70°C. Copper powder was transferred to a container, and a reducing agent was added while stirring to perform plating. The copper powder after plating was taken out and washed to obtain gold-plated copper powder.

The obtained gold-plated copper powder was dispersed in a vehicle consisting of an organic solvent and an organic binder to form a metallizing paste. As the organic solvent and organic binder, the organic solvent and organic binder that are normally used in metallizing paste are used. Examples of the organic solvent include terpineol, and examples of the organic binder include ethyl cellulose.

Fig. 1 is a graph showing the oxidation resistance of the gold-plated copper powder obtained in the above example, and Fig. 2 shows the results measured on ordinary copper powder without gold plating as a comparative example. In both figures, graph a shows the temperature of the sample, and graph b shows the weight of the sample. The vertical axis represents the sample temperature and sample weight.

The sample was heated almost constantly at a rate of about 10° C./min.

The increase in weight of the sample indicates that the copper powder was oxidized and increased in weight, but with the gold-plated copper powder of the above example, almost no weight increase was observed even when the temperature was raised to about 300 ° C.
The weight starts to increase around 50°C. On the other hand, in the copper powder of the comparative example, an increase in weight is already observed from around 200°C. The it++ results show that the gold-plated copper powder of this example has greatly improved oxidation resistance compared to conventional copper powder.

When firing the ceramic circuit board, a metallization paste using the gold-plated copper powder as a conductor was screen printed on a glass ceramic green sheet, and a plurality of sheets were laminated by thermocompression bonding. This was heated to 300°C in an oxidizing atmosphere.
After removing the binder for 12 hours, it was fired at 950° C. in a nitrogen atmosphere.

With gold-plated copper powder, the copper powder is coated with a gold-plated film, so even when heated in an oxidizing atmosphere, the copper powder is protected from oxidation, and the binder in the green sheet is removed without oxidizing the copper. I was able to burn it completely.

Also, regarding the conductivity of the conductor portion formed on the glass ceramic by co-firing, results were obtained that were not significantly inferior to those using copper powder without gold plating. The conductor resistance was about 1.5 times that when copper powder was used, and almost the same as when a conventional metallized paste using gold powder as a conductor was used.

[Example 2] N1-Cu-P alloy plating was applied to the same copper powder as above.

The resulting plated copper powder was heated at approximately 320°C in an oxidizing atmosphere.
It was stable until then.

In addition, a metallized paste formed in the same manner using this plated copper powder was screen printed on glass ceramic and laminated in the same manner as above, and after removing the binder at 300°C in an oxidizing atmosphere, it was fired at 950°C. A ceramic circuit board was obtained. Although the conductivity of the obtained conductor portion was slightly inferior to that of Example 1, sufficiently good conductivity was obtained as a conductor portion of one circuit board.

[Example 3] Using the same copper powder as in the above example, this copper powder was plated with reni-nickel, and the upper layer was plated with rhodium,
Furthermore, the upper layer was plated with gold. This multilayer plated copper powder was stable up to about 400°C in an oxidizing atmosphere.

Similar to the above example, a metallization paste was prepared using this plated copper powder, printed and laminated on glass ceramic, and after debinding at 300°C in an oxidizing atmosphere,
A ceramic circuit board was obtained by firing at about 950°C. The characteristics of the obtained conductor part were such that it had sufficient conductivity as a conductor part of a circuit board.

In the metallizing paste shown in each of the above examples, the copper powder used as the conductor of the paste is plated in advance to make the surface of the copper powder oxidation resistant.

Since the copper powder is coated with a heat-resistant plating film, the oxidation resistance of the copper powder can be improved, resulting in a paste that can be used satisfactorily even in an oxidizing atmosphere at 300 to 400°C. As a result,
Binder removal can be performed in an oxidizing atmosphere, and binder components can be removed efficiently.

Furthermore, when comparing the characteristics of the conductor parts of the obtained ceramic circuit boards, it was found that in this example, since plated copper powder with excellent conductivity was used as the conductor powder, a conductor part with good conductivity could be formed. It has become possible to obtain conductivity characteristics comparable to or higher than that of a conductor part obtained by a conventional gold metallized paste using gold powder as a conductor powder. Furthermore, since the conductor portion is mainly made of copper, the cost can be much lower than that using gold as the conductor.

Note that the plating applied to the copper powder in advance is not limited to the above-mentioned plating, and any plating that can form a plating film having oxidation resistance and heat resistance at 300 to 400° C. can be similarly applied.

For example, similar effects can be obtained with plating such as N1-P and N1=B.

The present invention has been variously explained above using preferred embodiments, but the present invention is not limited to these embodiments.
Of course, many modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above, in the metallizing paste according to the present invention, plated copper powder obtained by plating copper powder with oxidation resistance and heat resistance is used as the conductor powder. The oxidation resistance of copper powder can be improved much compared to that of copper powder. As a result, when firing a ceramic circuit board, the binder from the green sheet can be removed in an oxidizing atmosphere, and the binder component can be effectively removed, making firing the ceramic circuit board extremely easy. be able to.

Moreover, by using plated copper powder with excellent conductivity as the conductor powder, the conductivity of the conductor portion of the obtained ceramic circuit board can be improved. Furthermore, since plated copper powder is used as the conductor powder, it can be manufactured at a much lower cost than when gold is conventionally used as the conductor powder.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are graphs showing the results of measuring the oxidation resistance of copper powders of Examples and Comparative Examples, respectively.

Claims (3)

[Claims] 1. In a metallizing paste used in the simultaneous firing of a low-temperature firing ceramic circuit board made by adding an organic solvent and an organic binder to a conductor powder, the conductor powder is a copper powder plated with oxidation resistance and heat resistance at 300 to 400°C. A metallizing paste characterized by using plated copper powder consisting of. 2. 2. The metallizing paste according to claim 1, wherein the plated copper powder is a gold-plated copper powder obtained by subjecting copper powder to gold plating. 3. Copper powder is plated with oxidation resistance and heat resistance at 300 to 400°C. A metallization paste, which is made by adding an organic solvent and an organic binder to plated copper powder, is coated on a low-temperature fired ceramic green sheet. A method for manufacturing a ceramic circuit board, which comprises heating a green sheet to 300 to 400°C in an atmosphere to remove the binder, and then firing the green sheet at a predetermined ceramic substrate firing temperature in a non-oxidizing atmosphere. .