JPH0479290A - Manufacture of ceramic circuit board - Google Patents

Abstract

PURPOSE:To protect tungsten powder from increasing excessively in size by using a matellizing metal where rhenium is added to tungsten particles and adopting a board made of aluminum nitride. CONSTITUTION:In a manufacturing method of a ceramic circuit board which uses tungsten powder as a metallizing metal and incinerates simultaneously the powder with ceramic green sheet and forms a circuit pattern, metallizing metal is used where rhenium is added to tungsten powder while aluminum nitride is adopted for the board. This construction makes it possible to improve the smoothness effectively by grinding the surface of the board and hence obtain a circuit board which is excellent in terms of electric resistors or the like of a conductor circuit.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method of manufacturing a ceramic circuit board.

(Prior Art) When forming a circuit pattern on a ceramic circuit board, there is a method of forming the circuit pattern by using a metallization paste and co-firing it with a ceramic green sheet. Since the ceramic green sheet is fired at a high temperature, a high melting point metal such as tungsten is used as the metallizing metal used for the conductor circuit of the circuit pattern. For example, the firing temperature of ceramic is 1500-1600 for alumina.
00°C, and 1700 to 2000°C for aluminum nitride.

To manufacture these ceramic circuit boards, a ceramic green sheet is formed and metallized paste is applied in a predetermined pattern using a screen printing method, or if vias are formed, the metallized paste is applied inside the via holes provided in the green sheet. After filling, the ceramic green sheet and the metallization paste are co-fired at a predetermined temperature to form a ceramic circuit board.

(Problem to be Solved by the Invention) As mentioned above, ceramic circuit boards are fired at a fairly high temperature, but when manufacturing circuit boards by simultaneous firing with tungsten powder as a metallizing metal, excessive sintered tungsten particles There is a problem that it becomes grainy. This is thought to be because the firing temperature during simultaneous firing is extremely high, so that the tungsten grains grow and become large grains during firing.

Recently, there are ceramic circuit boards that require extremely fine circuit patterns, and for products that require particularly flat surfaces, the surface on which the circuit patterns are formed is polished to achieve flatness after firing. There is something.

When flattening the circuit pattern surface by polishing in this way, tungsten is highly brittle, so if the tungsten grains become too large during firing, the tungsten grains will chip and fall off during polishing, making it difficult to achieve the desired flatness. There is a problem of not being able to obtain a degree. This problem is particularly problematic in products with highly densely arranged vias.

Therefore, in order to prevent tungsten grains from growing and becoming excessively large during firing, a mixture of tungsten powder and ceramic powder is used as a metallizing paste to ensure that tungsten is evenly dispersed within the conductor circuit. , attempts have been made to prevent excessive grain growth of tungsten. However, a mixture of tungsten powder and ceramic powder has a problem in that the electrical resistance of the conductor circuit increases.

Therefore, the present invention has been made to solve the above problems, and its purpose is to effectively prevent tungsten from forming excessive grains during firing, and to flatten the surface by polishing. An object of the present invention is to provide a method for manufacturing a ceramic circuit board that is easy and has excellent electrical characteristics.

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

That is, in a method of manufacturing a ceramic circuit board in which a circuit pattern is formed by co-firing a ceramic green sheet using tungsten powder as a metallizing metal, the method is characterized in that a metallizing metal obtained by adding rhenium to the tungsten powder is used. . Further, the substrate is made of aluminum nitride.

(Summary of the Invention) The present invention uses tungsten powder as a metallizing metal to create a ceramic circuit board by co-firing with a ceramic green sheet. It is characterized by the fact that it can be fired simultaneously.

By using a metallizing paste made by adding rhenium to tungsten powder, it is possible to obtain a ceramic circuit board with a smoother surface, as will be described later, and the electrical resistance of the conductor circuit can be made almost the same as when using only tungsten powder. can do.

Rhenium is used in a mixture of 1 to 10 parts by weight to tungsten. It is thought that by adding rhenium to tungsten, it acts to prevent excessive grain growth of tungsten during high-temperature firing and to improve the toughness of tungsten.

Hereinafter, an example in which a circuit board was manufactured using a metallized paste containing rhenium, and an example in which a circuit board was manufactured by a conventional method as a comparative example will be described.

〔Example〕

An example in which aluminum nitride is used as the ceramic substrate and vias are formed as the conductive circuit will be described.

The metallization paste was prepared by adding 3 g of an acrylic binder to a mixture of 97 g of tungsten powder (average particle size: 1.2 μm) and 3 g of rhenium powder, and then adding 15 ml of a glycol solvent to form a paste.

The ceramic substrate was prepared by mixing 100 g of aluminum nitride powder and 0.2 g of calcium carbonate with 11 g of an acrylic binder, 4 g of a plasticizer, and 100 mu of an organic solvent to form a slurry, and then forming a green sheet using a doctor blade method.

This green sheet was drilled with a diameter of 0.12 mm to form via holes, and the metallized paste was filled into the via holes.

After removing the binder in a nitrogen atmosphere, it was fired at 1750°C to obtain an aluminum nitride circuit board. The thickness of the aluminum nitride circuit board obtained was 1n+m. The thickness of the aluminum nitride circuit board is also the same in the following comparative examples.

[Comparative Example 1] In the same manner as in Example 1 above, an aluminum nitride ceramic circuit board in which vias were formed as conductive circuits was manufactured.

In this comparative example, it was used as a metallization paste for forming vias.

A mixture of 100 g of tungsten powder and 5 g of aluminum nitride powder, to which an acrylic binder and a glycol solvent were added, was used.

In the same manner as in Example 1, a slurry was formed using aluminum nitride powder, a green sheet was manufactured by the doctor blade method, and then a via hole with a diameter of 0.12 mm was formed.
The above metallized paste was filled. Firing was performed under the same conditions as in Example 1 to obtain an aluminum nitride circuit board.

[Comparative Example 2] A green sheet of aluminum nitride was formed in the same manner as in the above example using a metallization paste using only tungsten powder, and after filling the via hole with the metallization paste,
An aluminum nitride circuit board was obtained by firing under the same conditions.

a1 Measurement of surface smoothness The surface of the aluminum nitride circuit board obtained in the above examples and comparative examples was polished with diamond abrasive grains to make it a flat surface, and the maximum value in the depth direction of the recesses formed on the surface was measured. did.

Circuit board of Example: 0.07 μm Circuit board of Comparative Example 1: 0.11 μm Circuit board of Comparative Example 2: 5.0 μm The above results show that the circuit board using metallized paste made by adding rhenium to tungsten powder has the best smoothness. Indicates that

Compared to Comparative Example 2, which uses only tungsten, the smoothness is significantly improved.

The reason why the surface smoothness of the rhenium-added product was improved in this way is thought to be because the addition of rhenium prevented excessive grain growth of tungsten during firing.

b. Measurement of electrical resistance The electrical resistance values of the vias in the aluminum nitride substrates of the example and comparative example were measured. The measurement results are as follows.

Circuit board of Example 140mΩ Comparative Example 1
Circuit board of 300 mΩ Circuit board of Comparative Example 2 The 135 mΩ Example, that is, the one that uses a metallized paste made of tungsten powder and rhenium, and the one that uses Comparative Example 2, that is, that uses a metallized paste that contains only tungsten powder, have the same electrical resistance. Comparative Example 1 showed a considerably high electrical resistance value.

From the above measurement results a and b, by using a metallized paste made by adding rhenium to tungsten powder,
An aluminum nitride circuit board having a low electrical resistance value and a smooth surface can be easily obtained. As a result, it can be effectively used for ceramic circuit boards that require the formation of extremely high-density circuit patterns.

Although the above embodiment describes aluminum nitride, it can also be suitably used to manufacture a ceramic circuit board made of alumina or the like that requires high-temperature firing.

Note that this method is particularly effective for aluminum nitride, which requires a considerably higher firing temperature than other ceramics.

In addition, although the above embodiment describes the surface smoothness when vias are formed on the circuit board, it is also effective in improving the surface smoothness when a circuit pattern is formed on the surface of the circuit board. be.

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) According to the method for manufacturing a ceramic circuit board according to the present invention,
As mentioned above, a ceramic circuit board whose smoothness can be effectively improved by polishing the surface;
For example, it is possible to easily obtain a circuit board made of aluminum nitride, and also to obtain a ceramic circuit board having excellent characteristics such as electrical resistance of conductor circuits. Further, this provides remarkable effects such as being able to easily manufacture a ceramic circuit board having a higher density circuit pattern.

Claims (2)

[Claims] 1. A method for manufacturing a ceramic circuit board in which a circuit pattern is formed by co-firing a tungsten powder with a ceramic green sheet using tungsten powder as a metallizing metal, characterized in that the metallizing metal is made by adding rhenium to the tungsten powder. Substrate manufacturing method. 2. 2. The method of manufacturing a ceramic circuit board according to claim 1, wherein the substrate is made of aluminum nitride.