JPH0652721A - Conductor - Google Patents

Abstract

PURPOSE:To obtain a conductor excellent in soldering and an anti-oxidation property as a hybrid IC, a through hole conductor, a multilayer substrate circuit, a multilayer ceramic capacitor outer electrode and a terminal electrode of a ruthenium group resistor. CONSTITUTION:A conductor to be expressed by a general formula to be formed on a ceramic base material AgxCu1-x (provided that 0.001<=x<=0.4, atomic ratio) while having the surface silver concentration higher than the average silver concentration 7 and having a region increasing the silver concentration toward the surface is manufactured. Thereby, this conductor is excellent in properties of soldering, solder errosion resistance, leading-out of a lead wire, plating and an overcoat glass matching, etc., when it is used for a conductive circuit using the conductor, through hole conduction, a multilayer substrate circuit, a multilayer ceramic capacitor outer electrode and a ruthenium group resistor terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor having excellent conductivity, silver migration resistance, and storage stability, and a conductive circuit using the conductor, a conductive circuit for a multilayer substrate, a laminated ceramic capacitor external electrode, a through hole. The present invention relates to a conductor and a terminal electrode of a ruthenium-based resistor.

[0002]

2. Description of the Related Art Conventionally, silver, silver-palladium, silver-platinum, copper, gold, nickel and the like have been known as those used as conductors on ceramic substrates. These conductors are used as conductive circuits. , Used as capacitor electrodes, through-hole conductors, and ruthenium-based resistor terminals.

[0003]

The conductive material used as a known conductor has the following problems. For example, silver is not suitable for practical use due to the serious problem of silver migration as the wiring on the ceramic substrate or the space between the through holes becomes narrower as the line becomes finer. In addition, solder erosion is likely to occur and the wire is easily broken. With silver-palladium, impedance increases significantly due to fine lines, and it is difficult to use as wiring. In the case of silver-platinum, not only is the cost high, but there is still a problem of silver migration as fine lines are advanced.

There is also a conductor made of copper, but when it is used by soldering to a circuit, it is difficult to get solder, or when glass is used as an insulating paste by overcoating, an overcoat glass or a crossover glass is used. The conductor is oxidized, causing a change in conductivity or discoloration. Therefore, it is difficult to store. Further, when used as a terminal of a ruthenium resistor, oxygen is transferred from the ruthenium resistor to a copper conductor and copper is oxidized at the interface, which easily causes current noise. That is, there is a serious problem that oxygen is easily transferred between the conductor and the base material as a partner, and the copper conductor is oxidized to cause inconveniences in terms of electrical properties, solderability, and the like. Also, when it is used as an external electrode of a monolithic ceramic capacitor, there is a problem in terms of solderability or plating property due to poor oxidation resistance.

[0005]

In order to solve the above-mentioned problems, the structure of the present invention comprises a conductor as described in the claims and a conductive circuit using a conductor of the composition, a through-hole conductor, and a laminate. The present invention relates to an external electrode of a ceramic capacitor, a conductive circuit for a multilayer substrate, and a ruthenium-based resistor terminal electrode.

The conductor of the present invention can be prepared by a conductive paste, plating, vapor deposition or sputtering, but it is preferable to use the conductive paste. In particular, the present inventor has already filed an application (Japanese Patent Application No. 3-7).
8298) It is preferable to use a conductive paste. According to the disclosure, the conductive paste is of the general formula Ag _x Cu.
_1-x (where x is represented by 0.001 ≦ x ≦ 0.4,
A conductive paste comprising a copper alloy powder having a surface silver concentration higher than the average silver concentration and having a region where the silver concentration increases toward the particle surface, glass frit, and an organic vehicle. When silver is concentrated on the surface of the present invention using a paste and a conductor having a region where the silver concentration increases toward the surface is prepared, the ceramic base material used in the present invention is an alumina substrate, A little alumina substrate, a glass substrate, a little silicon substrate, and a crossover glass substrate printed and baked on the substrate,
It is obtained by printing and applying the paste on a ceramic substrate such as a green sheet for a multilayer substrate, a laminated ceramic capacitor, and a ruthenium-based resistor, and firing at a high temperature. As a mechanism for obtaining the conductor of the present invention when the conductive paste having the composition is used, the general formula is Ag _x C
u _1-x (provided that 0.001 ≦ x ≦ 0.4, atomic ratio), and is composed of a copper alloy powder having a high silver concentration on the particle surface and having a region where the silver concentration increases toward the surface. When the conductive paste is sintered in the above-mentioned temperature range in an inert atmosphere, the powders sinter, the powders bond with each other, and the particle shape deteriorates. Although each particle has a structure rich in silver on the surface, during the production of the conductor of the present invention by sintering, the silver concentration on the surface of the particle starts to diffuse toward the lower concentration. However, since the conductor of the present invention is produced by sintering at a temperature equal to or lower than the melting point rather than forming a conductor by melting, the silver concentration does not average, and the silver concentration increases toward the surface. Is maintained. Examples of the inert gas atmosphere for sintering include nitrogen, argon, helium, hydrogen and mixed gas thereof. However, in order to prevent the unbaked product of the organic vehicle from remaining in the conductor of the present invention, it is preferable to mix a small amount of oxygen or water vapor in the baking atmosphere. In this case, the oxygen doping amount is preferably 60 ppm or less. If it exceeds this value, the surface silver concentration of the conductor of the present invention decreases, and it becomes impossible to obtain a region where the silver concentration increases. Not only that, but the copper oxide on the surface increases. It is preferably 40 ppm or less.

The firing temperature or heat treatment temperature is required to be 400 ° C. or higher in order to promote the sintering sufficiently and to secure the strength of the conductor sufficiently, and in order to obtain further strength, the temperature is 550 ° C. or higher. Is preferred. If the strength of the conductor is not sufficient, the conductivity may be inconvenienced or the solder may be eaten away. Further, if the firing or heat treatment temperature is too high, melting rather than sintering occurs, so that the composition inside the conductor is made uniform, silver is concentrated on the surface of the present invention, and silver increases toward the surface. It becomes impossible to obtain a conductor having a region to be filled. Further, the melting may change the shape of the conductor such as a circuit, or the shape of the external electrodes of the monolithic ceramic capacitor. The firing or heat treatment temperature is preferably 1000 ° C or lower, more preferably 900 ° C or lower.

When the conductor of the present invention is produced by using the conductive paste having the composition, if necessary, after sintering,
The conductor of the present invention can also be produced in the same manner by vapor-depositing, sputtering or plating a small amount of silver on the surface, and then treating at the heat treatment temperature in an inert atmosphere to diffuse silver into the conductor. The conductor of the present invention has the general formula Ag _x Cu _1-x (where 0.001 ≦ x ≦
0.4, atomic ratio), and the average silver concentration on the surface of the conductor is high, and there is a region where the silver concentration increases toward the surface of the conductor. 2.1 times or more of the silver concentration of, and more than 3 times 3
It is preferably 0 times or less. When silver completely covers the surface of the conductor, the migration resistance is rather deteriorated. Since there is a region where the silver concentration increases toward the surface on the surface of the conductor, there is little solder erosion of the conductor, and good solderability is maintained for a long time even if the conductor is left at high temperature. Has the advantage of Further, since the conductor itself contains a small amount of silver, the impedance is low, and since silver is concentrated to a high concentration on the surface, resistance to high frequencies is also low. If this is a conductor obtained by plating a copper conductor with silver, not only does the adhesiveness with the conductor be insufficient with respect to solder, but also the copper conductor is rather oxidized by the plating silver. is doing.

The silver concentration of the conductor of the present invention means Ag / (Ag
+ Cu), the copper concentration is Cu / (Ag + Cu) (atomic ratio)
Is. The silver concentration and copper concentration on the surface and near the surface were measured by the following method using XPS (X-ray photoelectron spectroscopy analyzer). Device: XSAM800 manufactured by KRATOS, Inc. Sample: A conductive double-sided adhesive tape was attached to a sample stand, and the conductor of the present invention was attached so as to completely cover the double-sided tape so as not to deform the surface.

Etching conditions: Argon ion gas is added
Fast voltage 2 KeV, for argon ion beam sample surface
Incident angle 45 degree, room pressure 10^-75 minutes each time at torr
went. Measurement conditions for silver concentration: Magnesium Kα ray (electric
A pressure of 12 KeV and a current of 10 mA) are applied to collect the photoelectrons.
The projecting angle is 90 degrees with respect to the sample surface, and the room pressure is 10 ^-8
It was done at torr. Silver concentration is measured by
And repeat this 5 times, average the first 2 times
The values were defined as the surface silver concentration x and the surface copper concentration 1-x.

The average silver and copper concentrations were measured by cutting a small amount of the conductor, dissolving the sample in concentrated nitric acid, and using an ICP (high frequency inductively coupled plasma emission spectrometer). The conductor of the present invention may have various shapes depending on the application and is not particularly specified. For example, in the case of a conductive circuit or a multi-layer substrate circuit, a linear shape (for example, a thickness of 3 μm to 100 μm, width 10 to 1000 μm) and pad-like (thickness 3 to 100 μm). Examples of the through hole use include a conductor formed on the inner wall of a hole formed in a ceramic substrate or a glass substrate having a diameter of 0.1 to 3 mm.

Further, as the external electrodes of the monolithic ceramic capacitor, the internal electrodes are nickel, palladium,
It can be used as an external electrode of a dielectric that is copper. The conductor of the present invention as the external electrode may have any shape as long as it is formed so as to sufficiently cover the surface of the internal electrode from which the terminal is exposed. For a multilayer substrate circuit, an inner layer circuit obtained by stacking several layers of green sheets printed with a conductive paste and firing the circuit, especially a line thickness of 3 to 50
It has a fine line shape or a pad shape (thickness 3 to 1000 μm) with a width of 3 to 1000 μm.

As the terminal electrode of the ruthenium-based resistor,
It is formed on the ruthenium resistor and has a portion that directly contacts the ruthenium resistor. The shape is a line or pad, but the size is not specified. Further, it may have a direct contact portion with the silver-palladium-based conductor, if necessary. In the case where the conductor is produced by sintering, it is preferable that the space inside the conductor is small, that is, the state where the sintering is sufficiently advanced, and the void ratio of the conductor is preferably less than 30%. The porosity is measured by a mercury penetration type pore distribution (mercury porosimeter, manufactured by Kahero Elbe). That is, when the space exceeds 30 Vol%, the conductivity is poor and the solderability is 150
The test is not good if left in the air at ℃. Preferably 0.1
% To 30 wt%, and further 0.5 to 25 wt%.

The conductor of the present invention has a region in which the silver concentration on the surface is higher than the average silver concentration and the silver concentration increases toward the surface, but when used for the above-mentioned use, it has the following advantages. . In other words, since there is a lot of silver on the surface, it has good solderability even when it is stored in a bad environment such as high temperature for a long time, and since the concentration of silver decreases toward the inside, good solder corrosion resistance, There are few failures due to solder non-bonding and erosion in the circuit. In addition, a conductive circuit is usually treated with an insulating overcoat glass or a crossover glass for use, but even if such an insulating paste is overcoated on the conductor of the present invention, the conductor is not oxidized by the coated glass. This does not occur, and the characteristics of the conductor are not inferior even if the circuit is multilayered.

Further, when used for the terminal of the ruthenium-based resistor, the oxide resistor does not oxidize the conductor at the interface, and there is no electrical noise. Furthermore, when it is used as an external electrode of a monolithic ceramic capacitor, its surface has good oxidation resistance, so it is easy to plate in the plating process, and since the silver concentration decreases toward the inside, diffusion inside the dielectric occurs. Hateful.

When the conductor of the present invention is manufactured, it is preferable to use a conductive paste. Therefore, depending on the application, it is preferable that the glass component is used in the paste in order to have excellent adhesiveness on the substrate or the base material, but the glass component is mixed in the produced electric conductor of the present invention to the extent that characteristics are not impaired. It may be done. For example, glass components used include PbO, B ₂ O ₃ , and Si.
O ₂ , ZnO, CaO, Al ₂ O ₃ , Na ₂ O, K
Examples include those containing components such as ₂ O, MgO, Bi ₂ O ₃ , TiO ₂ , and ZrO ₂ . The amount of the mixed glass component is preferably 30 parts by weight or less, and more preferably 15 parts by weight or less with respect to 100 parts by weight of the conductor. If it exceeds 30 parts by weight, the electrical conductivity of the conductor will be remarkably poor.

When the glass component is mixed, it is preferable that the glass component is not present on the surface of the conductor of the present invention as much as possible. When the glass component is present in a large amount on the surface of the conductor, soldering is performed. It is extremely inferior in sex. It is preferable that the total amount of the glass components is 100 parts by weight or less based on 100 parts by weight of the total silver and copper components on the surface.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples. Powder preparation example

[0019]

Example 1 10 g of conductive powder having an average particle diameter of 10 μm and a surface silver concentration of 0.8 atomic ratio, an average silver concentration of 0.1 atomic ratio, and a copper concentration of 0.9 atomic ratio, PbO-B ₂ O ₃ −
ZnO glass frit 0.2 g, ethyl cellulose 0.
A paste consisting of 02 g, terpenol 0.2 g, and cuprous oxide 0.1 g was screen-printed on an alumina substrate to form a circuit having a line with a width of 100 μm and a thickness of 15 μm. After printing, in a nitrogen atmosphere at 900 ° C (<10pp
m oxygen) for 10 minutes. At this time, 60 ppm of oxygen was doped up to 550 ° C.

The resulting conductor was cut into a 5 mm square while still attached to the alumina substrate, and XPS measurement was performed. The silver concentration on the surface of the conductor is 0.6, 0.5, 0.3, 0.2,
At 0.15, the surface silver concentration was 0.55. Also,
When the conductor was dissolved in concentrated nitric acid and analyzed, the average silver concentration x was 0.1, and the surface silver concentration was 5.
It was 5 times. A part of the conductor was cut off, and the porosity of the conductor was measured with a porosimeter to find that it was 15 Vol%.

The conductivity was as good as 2 × 10 −6 Ω · cm. The solderability was 100%. Furthermore, when the obtained conductor was left in the air at 150 ° C. for 100 hours and then soldered, a solderability close to 100% was exhibited. Also, the solder erosion test is performed 260
When a dip was conducted in a eutectic solder bath at 10 ° C for 10 seconds, no disconnection was observed.

When the overcoat glass paste was printed on the linear conductor and fired in a nitrogen atmosphere, the linear conductor was not oxidized by the overcoat glass. When a migration test was conducted, the leakage current between the conductor lines was as small as that of copper.

[0023]

Example 2 The conductive paste used in Example 1 was printed on the inner wall of a hole by screen printing in a 0.3 mmφ hole formed on an alumina substrate. After that, 850 ℃
It was fired in a nitrogen atmosphere (5 ppm oxygen doped) to obtain a through-hole conductor. The obtained conductor was cut into a 3 mm square while being attached to the substrate, and the surface of the conductor was analyzed using XPS. The silver concentration on the surface of the conductor is 0.5, 0.45, 0.
3, 0.3, 0.2, and the surface silver concentration is 0.475.
Met. The average silver concentration was 0.1, and the surface silver concentration was 4.75 times the average silver concentration. The porosity of the conductor was 20 Vol%.

The conductivity was as good as 2 mΩ. Also,
The solderability was 100%. Furthermore, 150 ℃ 1
After leaving it in the air for 00 hours, a soldering test
It showed 100% solderability. Also, the overcoat glass paste was screen-printed on the through-hole conductor. When printed and fired, the conductor was not oxidized into a glass paste and had good electrical characteristics.

When the migration test was conducted between the through-hole conductors (at intervals of 0.3 mm) at 10 V, 60 ° C. and 90% relative humidity, the migration property was almost the same as that of the copper conductor and was small. When a solder erosion test was performed, solder erosion did not occur in the dip test at 260 ° C. for 10 seconds.

[0026]

Example 3 The conductive paste used in Example 1 was applied to the deposition surface of the internal electrode as an external electrode of a laminated ceramic capacitor having nickel as an internal electrode. Furthermore, 80
Firing was performed for 10 minutes in a 0 ° C. nitrogen atmosphere (10 ppm oxygen dope). Using the obtained conductor as a capacitor, X
When measured by PS, the silver concentration on the surface was 0.
5, 0.45, 0.35, 0.25, 0.15,
The surface silver concentration was 0.475. The average silver concentration is 0.1, and the surface silver concentration is 4.75 of the average silver concentration.
It was double. The electric capacity of the obtained capacitor showed the standard electric capacity. Also, when nickel was plated on the conductor, it could be plated 100% completely. 150 ° C 1
When the conductor was left for 00 hours and plated in the same manner, 10
Complete plating of 0% was completed.

When a copper lead wire was attached using solder, the attachment was complete in terms of adhesive strength. Also, 1
When the lead wire was attached using solder in the same manner after 100 hours at 50 ° C., good attachment was possible. 60 ° C 9
When left to stand with a voltage of 100 V applied in 0% humidity, migration of silver into the dielectric body was not observed. For the measurement, the dielectric body is cut after the test, and EP
This was done using MA.

[0028]

Example 4 10 g of copper alloy powder having an average particle size of 5 μm and a surface silver concentration of 0.07 and an average silver concentration of 0.01,
PbO-SiO ₂ -B ₂ O ₃ based glass frit 0.3
g, ethyl cellulose 0.01 g, terpenol 0.5
g was thoroughly mixed to form a paste. The obtained paste was screen-printed on a green sheet containing mullite as a main component to print a fine line circuit having a width of 100 μm and a thickness of 10 μm. In the same way, make 6 green sheets to make multiple layers by hot pressing, and in a nitrogen atmosphere at 650 ° C (2
It was baked with 0 ppm oxygen dope) for 10 minutes. Further, it was fired in a nitrogen atmosphere containing 1% of hydrogen to produce a multilayer circuit board. A part of the obtained conductor was cut, and the surface was measured by XPS so that the surface of the conductor was not deformed. The silver concentration on the surface of the fine line conductor is 0.05, 0.04,
At 0.034, 0.03 and 0.025, the surface silver concentration was 0.045, and the average silver concentration was 0.01.
The silver concentration on the surface was 4.5 times the average silver concentration.

The fine line conductor obtained (width 100
When left at 10 V, 60 ° C., and 90% humidity for 10 μm), the migration was almost the same as that of the copper conductor and was very small. Porosity of conductor is 10 Vol
%Met. When it was soldered to the fine line conductor, it was 100% solderable. Also, 15
After leaving it in the air at 0 ° C. for 100 hours and then soldering, 100% soldering could be performed. Furthermore, 260 ° C 10
When a dip test was carried out in a second eutectic solder bath, there was almost no solder erosion and no wire breakage.

Furthermore, when crossover glass was applied onto the fine line conductor and fired, the fine line conductor was not oxidized and the conductivity was hardly changed.

[0031]

Example 5 A commercially available ruthenium-based resistor (for 1 MΩ) was provided on an alumina substrate with a width of 200 μm, a thickness of 15 μm, and a length of 20.
mm and printed in air at 850 ° C. Further, the conductive paste used in Example 4 was printed so as to partially overlap with both terminals of the previously burned ruthenium resistor by a length of 2 mm. Furthermore, in a nitrogen atmosphere at 600 ° C. (oxygen 30
(ppm dope) and baked for 10 minutes. The silver concentration on the surface of the conductor is 0.05, 0.044, 0.4, 0.
36 and 0.32, and the surface silver concentration was 0.047. The average silver concentration was 0.01, and the surface silver concentration was 4.7 times the average silver concentration.

The resistance value of the ruthenium resistor showed a specified resistance value, the resistance value after standing for 100 hours at 150 ° C. did not change from the initial resistance value, and there was no oxidation at the interface between the ruthenium resistor and the conductor. The porosity of the conductor was 25 Vol%.

[0033]

Example 6 The paste of Example 4 was applied as an external electrode of a monolithic ceramic capacitor whose internal electrode was copper. After coating, the coating was baked at 800 ° C. in a nitrogen atmosphere (50 ppm oxygen doping) for 10 minutes. As a result of the surface analysis of the obtained conductor, the silver concentration was 0.06, 0.05, 0.045,
0.42 and 0.36, and the surface silver concentration is 0.055
Which was 5.5 times the average silver concentration.

The electric capacity showed a specified capacity value. Also,
When a soldering test was performed after leaving it in the air at 150 ° C. for 100 hours, 100% solderability was obtained and the lead wire could be attached with sufficient adhesive force. Furthermore, when a nickel plating test was conducted, sufficient plating properties were obtained even at the initial stage and after standing at 150 ° C. for 100 hours. When a part of the conductor was cut off and the porosity was measured, it was 25 Vol%.

[0035]

Example 7 A copper alloy powder 10 having a surface silver concentration of 0.9 and an average silver concentration of 0.3 and an average particle diameter of 2 μm.
g, PbO—SiO ₂ —ZnO—B ₂ O ₃ -based glass frit 0.1 g, acrylic resin 0.2 g, and butyl carbitol acetate 0.4 g. Width of the obtained paste is 100μ on the glass substrate
m, and a fine line circuit having a thickness of 12 μm was printed. After printing, in a nitrogen atmosphere at 600 ° C (oxygen 30ppm dope)
And baked for 15 minutes. The silver concentration on the surface of the obtained conductor was 0.95, 0.9, 0.86, 0.6, 0.5, and the silver concentration on the surface was 0.925. The average silver concentration is 0.3, and the surface silver concentration is 3.
It was 1 time.

The solderability was 100%. Also,
When the solderability after standing at 150 ° C. for 100 hours was also tested, it was 100%. When the overcoated glass was printed on the conductor and fired, there was no discoloration and no oxidation of the conductor by the glass paste was observed. The porosity of the conductor was 15 Vol%.

[0037]

Example 8 A green sheet was multilayered using the conductive paste prepared in Example 7, and a fine line having a width of 80 μm and a thickness of 12 μm was screen-printed on the outermost layer of the multilayer substrate which was co-fired. 600 ° C in a nitrogen atmosphere (oxygen 6
It was heated and baked for 10 minutes with 0 ppm dope). The silver concentration on the surface of the conductor is 0.93, 0.88, 0.83,
It was 0.73 and 0.6, and the surface silver concentration was 0.905. The average silver concentration was 0.3 and the surface silver concentration was three times the average silver concentration.

When a soldering test was conducted, the initial value was 15
Even after standing in the air at 0 ° C. for 100 hours, 100% attachability was obtained.

[0039]

[Comparative example]

[0040]

[Comparative Example 1] The average silver concentration produced in Example 4 was 0.01,
Conductive paste consisting of copper alloy powder with a silver concentration of 0.07 on the surface is screen printed on an aluminum substrate,
A circuit having a width of 100 μm and a thickness of 10 μm was formed. Further, it was heated and baked at 900 ° C. in a nitrogen atmosphere (100 ppm oxygen dope) for 10 minutes. The silver concentration on the surface of the obtained conductor is 0.002, 0.003, 0.00 from the surface.
8, 0.005, 0.01, and the surface silver concentration is 0.
It was 0025. The average silver concentration was 0.01 and the surface silver concentration was 0.25 times the average silver concentration. Further, the copper on the surface was oxidized.

When the solderability was tested, the solderability was poor at 10% or less. Also, when left in the air at 150 ° C. for 100 hours, the solderability was poor and almost no soldering occurred. When the overcoat glass paste was printed and fired, the glass was oxidized and the surface of the conductor was discolored.

[0042]

Comparative Example 2 Copper alloy powder 10 having an average particle size of 5 μm and a surface silver concentration of 0.8 and an average silver concentration of 0.6.
_{g, PbO-ZnO-B 2} O 3 based glass frit 0.5
A circuit having a width of 100 μm and a thickness of 10 μm was formed by screen-printing a conductive paste composed of g, 0.1 g of ethyl cellulose and 0.3 g of butyl carbitol acetate on a multi-layered substrate of 6 layers. Further, it was heated and baked in a nitrogen atmosphere at 600 ° C. (10 ppm oxygen doping) for 10 minutes. The surface silver concentration of the conductor is 0.8, 0.7, 0.7,
It was 0.68 and 0.6, and the surface silver concentration was 0.75. The average silver concentration was 0.6, and the surface silver concentration was 1.25 times the average silver concentration.

The solderability was 100% at the initial stage and was 15
The solderability was 100% even if left in the air at 0 ° C for 100 hours, but dip in a solder bath at 260 ° C for 10 seconds.
Upon testing, solder erosion occurred and the wire was broken. Moreover, when a migration test was conducted, 10V, 60
A remarkable migration occurred at 90 ° C in a humidity of 90%, and it was colored black.

[0044]

[Comparative Example 3] Copper powder _{10g, PbO-ZnO-B 2} O 3
Glass frit 0.3 g, ethyl cellulose 0.2
and a conductive paste of 0.3 g of terpenol were formed on an alumina substrate by screen printing. Furthermore, in a nitrogen atmosphere at 900 ° C. (oxygen 5 ppm doping), 1
It was heated and baked for 0 minutes. The soldering test of the obtained conductor was 70%. However, 150 ° C 10
After a soldering test after leaving it in the air for 0 hours, 1
It was bad at 0% or less. Further, when the overcoat glass paste was printed and fired, the discoloration of the conductor and the conductivity were remarkably reduced.

In the solder erosion test, solder erosion did not occur. In addition, as a result of the migration test, migration was extremely difficult to occur.

[0046]

[Comparative Example 4] 10 g of commercially available silver powder (average particle size 1 μm), P
bO-SiO ₂ -CaO glass frit 0.4 g, methyl cellulose 0.1 g, butyl cellosolve acetate 1
g was mixed thoroughly to form a paste. 100% of the obtained paste on a green sheet composed mainly of alumina.
20 μm lines (interval 100 μm) were printed. In the same manner, six green sheets were printed and laminated by hot pressing six sheets, and treated at 600 ° C. in air for 1 hour to remove the binder.

Further, in a nitrogen atmosphere containing 1% of hydrogen, 90
It was treated at 0 ° C. for 1 hour. The obtained conductivity is 1.5 mΩ / □
Met. However, when 10 V (DC voltage) was applied between the lines and left in an atmosphere of 60 ° C. and 90 humidity, migration occurred in an instant and a short circuit occurred. Also, as a result of solder erosion, wire breakage occurred.

[0048]

Comparative Example 5 The conductive paste prepared in Comparative Example 2 was applied as an external electrode of a laminated ceramic capacitor.
Firing was performed in a nitrogen atmosphere at 800 ° C. for 10 minutes. The silver concentration on the surface of the obtained conductor was 0.7, 0.65, 0.6, 0.
6, 0.6, and the surface silver concentration was 0.675. The average silver concentration was 0.6, and the surface silver concentration was 1.13 times the average silver concentration. When the lead wire was soldered and pulled, solder erosion occurred and it was easily removed from the mounting part.

When left at 60 ° C. and 90% humidity, diffusion of silver into the dielectric body occurred and migration short-circuited between the internal electrodes.

[0050]

Comparative Example 6 The copper paste prepared in Comparative Example 3 was printed on a ruthenium-based resistor that had already been formed by printing, and baked at 600 ° C. for 10 minutes in a nitrogen atmosphere (10 ppm oxygen doping). The resistivity of the obtained ruthenium-based resistor was higher than the standard value. Further, when the sample was aged in air at 150 ° C. for 100 hours, the resistance value was further increased. A large amount of copper oxide was formed at the interface between the ruthenium resistor and the copper conductor.

[0051]

The present invention is represented by the general formula Ag _x Cu _1-x (where 0.001 ≦ x ≦ 0.4, atomic ratio), and the surface silver concentration is higher than the average silver concentration, and The present invention relates to a conductor having a region where the silver concentration increases toward the surface, a circuit using the conductor, a through-hole conductor, a laminated ceramic capacitor external electrode, a ruthenium-based resistor terminal electrode, and a multilayer substrate circuit. However, as an effect, since silver is highly concentrated on the surface, when used as a conductor,
Solderability has the advantage that even if the component is left at high temperature, the defect rate is extremely small, and furthermore, lead wires can be attached and reliable soldering on fine lines is possible. .

Further, since the amount of silver decreases from the surface toward the inside, the occurrence of local batteries is small, corrosion is unlikely, and the solder is less eroded. Further, there is an advantage that the capacitance does not decrease due to migration in the case where the distance between the internal electrodes is small like the monolithic ceramic capacitor. Further, the oxidation of the conductor at the interface with the ruthenium resistor is suppressed, and a stable resistor can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/46 S 6921-4E

Claims (8)

[Claims] 1. A conductor formed on a ceramic substrate.
Is the general formula Ag_xCu _1-x(However, 0.001 ≦ x ≦
0.4, atomic ratio), and the silver concentration on the surface of the conductor is
Higher than the average silver concentration, and silver concentration increases toward the conductor surface.
A conductor having a region of increasing degree. 2. The porosity of the conductor according to claim 1 is 0.1.
% To 30 Vol%, a conductor. 3. A conductor, wherein the silver concentration on the surface of the conductor according to claim 1 or 2 is 2.1 times or more the average silver concentration. 4. A conductive circuit comprising the conductor according to claim 1, 2, or 3. 5. A laminated ceramic capacitor external electrode comprising the conductor according to claim 1. 6. A conductive circuit for a multilayer substrate, comprising the conductor according to claim 1, 2, or 3. 7. A through-hole conductor made of the conductor according to claim 1, 2, or 3. 8. A terminal electrode of a ruthenium-based resistor comprising the conductor according to claim 1, 2, or 3.