JPH10173341A - Ceramic multilayer board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic multilayer board, capable of integrating the resistor of ruthenium base material in high reliability having superior migration resistance. SOLUTION: This ceramic multilayer board 10 is formed of four layer ceramic insulator layers 11, formed of green sheets made of ceramic mainly comprizing barium oxide, aluminum oxide and silica. A via holes 12 to be filled up with palladium are provided in respective ceramic insulating layers 11, while inner conductors 13 made of copper are provided in the ceramic insulator layers 11 as the second, third layers from the top layer as well as the lowermost layer. At this time, a laminate 14 is formed by laminating these ceramic insulator layers 11 to be sintered integrally at about 850 deg.C in the reducing atmosphere. Later, the surface of the laminate 14 is printed with surface conductors 15, made of silver and resistors 16 made of ruthenium-base material to be backed at about 850 deg.C in an oxidizing atmosphere. Later if necessary, an overcoat 17 is provided on the surface of the ceramic board 10, while an active element 18 and a passive element 19 are packaged on the underside of the ceramic board 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multi-layer substrate, and more particularly to a ceramic multi-layer substrate used for electronic devices for consumer use, computers and the like.

[0002]

2. Description of the Related Art Conventionally, wiring boards using ceramics as insulators have been used as circuit boards for use in electronic equipment. As a typical example, there is a ceramic multilayer substrate using tungsten or molybdenum as a conductor and firing in a reducing atmosphere so as not to oxidize the conductor. However, since this ceramic multilayer substrate uses tungsten or molybdenum for the conductor, the conduction resistance is 10 to 2 times.
As high as 0 mΩ / □, it is necessary to perform gold plating in order to have solder wettability. Also, if a resistor made of a highly reliable ruthenium-based material that needs to be fired in an oxidizing atmosphere is formed, the conductor is oxidized. There were problems such as doing.

[0003] In order to solve these problems, a silver-based conductor having a low conduction resistance and capable of being oxidized and fired, or a conduction resistance as small as 1.5 to 3 mΩ / □, having resistance to migration and resistance to solder erosion. Copper-based conductors having excellent properties have been developed.

[0004]

However, in a conventional ceramic multilayer substrate using a silver-based material for the conductor, the silver or the like of the conductor formed inside tends to cause migration, resulting in poor insulation or short-circuit. There was a problem.

On the other hand, in a conventional ceramic multilayer substrate using a copper-based material for a conductor, a ruthenium-based resistor, which is known as a highly reliable resistor, requires firing in an oxidizing atmosphere, and thus requires a surface electrode. However, there is a problem that the copper constituting the copper oxide cannot be used because it is oxidized.

The present invention has been made to solve such a problem, and provides a ceramic multilayer substrate which is excellent in migration resistance and can integrate a highly reliable resistor of a ruthenium-based material. The purpose is to do.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a conductor formed inside is formed of a copper-based material, and a conductor formed on the surface is formed of a silver-based material. It is characterized by the following.

According to the ceramic multilayer substrate of the present invention, copper is used for the conductor formed inside, and silver is used for the conductor formed on the surface. It is possible to obtain an inner conductor and an outer conductor that maintain a good balance.

[0009]

FIG. 1 is a sectional view showing one embodiment of a ceramic multilayer substrate according to the present invention. The ceramic multilayer substrate 10 is formed of four ceramic insulator layers 11 formed of green sheets made of ceramic containing barium oxide, aluminum oxide and silica as main components.
A via hole 12 filled with palladium is provided in the ceramic insulator layer 11 of each layer, and a second, third, and lowermost ceramic insulator layer 11 from the top is provided.
Is provided with a conductor formed inside of copper, that is, an internal conductor 13.

Then, these ceramic insulator layers 11
Are laminated and integrally sintered at about 850 ° C. in a reducing atmosphere to form a laminate 14. Thereafter, a conductor formed on the surface made of silver, that is, a surface conductor 15 and a resistor 16 made of a ruthenium-based material are printed on the surface of the laminate 14 and fired at about 850 ° C. in an oxidizing atmosphere. At this time, a circuit is formed by the via hole 12, the internal conductor 13, and the surface conductor 15. Thus, the ceramic multilayer substrate 10 is completed. And, if necessary,
On the front surface of the ceramic multilayer substrate 10, an overcoat 17 is provided at necessary places, and on the back surface, an active element 18 and a passive element 19 are mounted.

The TCR of the ceramic multilayer substrate 10 having the above-described structure, that is, the resistance temperature change characteristics was evaluated. Table 1 shows the results. For comparison, a ceramic multilayer substrate using copper for the inner conductor and the outer conductor was simultaneously evaluated.

[0012]

[Table 1]

From Table 1, it can be seen that TC from -55 ° C. to room temperature (RT)
It can be seen that ruthenium-based resistance is better for both R and TCR at room temperature (RT) to 150 ° C. Therefore, by using silver for the external conductor, a highly accurate ruthenium-based resistor can be used.

The reliability characteristics (85 ° C., 80%, 50 V applied) of the ceramic multilayer substrate 10 were evaluated. Table 2 shows the results. For comparison, a ceramic multilayer substrate using silver for the inner conductor and the outer conductor was simultaneously evaluated.

[0015]

[Table 2]

From Table 2, it can be seen that no failure occurs in 20 pieces after 1000 hours in this embodiment, but 500H in the comparative example.
It can be seen that two out of 20 failures occur after elapse of r and five out of 20 failures occur after 1000 Hr. Therefore, by using copper for the internal conductor, migration resistance is excellent and reliability is improved.

As described above, in the above-described embodiment, since copper is used for the internal electrode and silver is used for the surface electrode, high-precision resistance, migration resistance and the like can all be maintained in a well-balanced manner. .

[0018]

According to the ceramic multilayer substrate of the present invention,
Since copper is used for the conductor formed inside and silver is used for the conductor formed on the surface, high precision resistance, migration resistance and the like can all be maintained in a well-balanced manner.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment according to a ceramic multilayer substrate of the present invention.

[Explanation of symbols]

 Reference Signs List 10 ceramic multilayer substrate 12 conductor formed inside (inner conductor) 15 conductor formed on surface (surface conductor)

Claims (1)

[Claims] 1. A ceramic multilayer substrate wherein a conductor formed inside is formed of a copper-based material and a conductor formed on the surface is formed of a silver-based material.