JPH06136298A - Low temperature-baking paste for outer conductor of multi layer circuit board having copper inner conductor - Google Patents

Abstract

PURPOSE:To provide a low temperature-baking paste comprising copper-silver alloy powder containing the copper and the silver in a specific composition, high in the concentrations of the silver on the surfaces of the particles, and comprising a specific particle diameter, glass frit and an organic vehicle, and having excellent migration resistance, adhesive force and oxidation resistance. CONSTITUTION:100 pts.wt. of copper alloy powder represented by formula: AgxCu1-x(0.01<=x<=0.4, atomic ratio), and having an average particle diameter of 0.1-20mum wherein the concentration of the silver on the surfaces of the particles is >=2.1 times than the average concentration of the silver and wherein the concentration of the silver increases toward the surfaces of the particles, and containing the >=20mum diameter powder in an amount of >=90%, 0.1-20 pts.wt. of glass frit having an average particle diameter of 0.1-10mum and containing the <=10mum diameter particles in an amount of >=90%, and an organic vehicle comprising a solution containing ethyl cellulose, an acrylic resin, etc., are compound with each other and kneaded to provide the objective paste excellent in migration resistance, adhesion, and oxidation resistance, and giving multilayer circuit boards having excellent electric joints to inner conductors and capable of being highly densified.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The paste for an outer conductor for a low temperature fired multilayer circuit board of the present invention can be used as an outer conductor for a low temperature fired multilayer circuit board exhibiting excellent characteristics in high density and high speed signal transmission. It can also be used as a hybrid IC circuit.

[0002]

2. Description of the Related Art In recent years, in the field of electronic materials, with increasing integration and densification, multi-layer technology for hybrid IC substrates has been advanced. Among them, low-temperature firing green sheet multi-layering is being promoted. As a multi-layer method, a noble metal powder such as silver, silver-palladium, silver-platinum, or gold is used as a conductor on a green sheet (substrate before firing) that is prepared by drilling or punching holes for via holes or through holes in advance. Paste, also copper,
Paste Further, if necessary, a dielectric and a resistance paste are printed, the printed green sheet is multilayered, and the temperature is 550 to 1060 ° C. in an oxygen-containing atmosphere or an inert atmosphere.
It is used as a multi-layer circuit board by co-firing at low temperature. After the outer conductor of the multilayer circuit board is formed in this way,
A method is known in which, if necessary, printing and firing of a crossover glass, an overglass, an external resistor and the like is repeated to form a circuit as a low temperature firing multilayer circuit board.

[0003]

The silver, silver-palladium, silver-platinum, gold, and copper used as the outer conductor of a low-temperature fired multilayer circuit board have the following problems. That is, in the case of silver, when it is used as an internal conductor, since it is laminated, the migration property between the internal conductors does not matter so much. Silver migration between outer conductors between high density patterns becomes a problem.

In the case of silver-varadium, the impedance is too high to be suitable for practical circuits. The silver-platinum outer conductor has good reliability and good solder erosion during soldering of a fine line circuit, but has a problem in migration property. Gold is not only too costly, but also easily erodes solder. When copper is used as the outer conductor, the impedance in the fine line is low and the electrical characteristics are excellent, but since it is produced by firing in an inert atmosphere, the green sheet and the inner conductor paste, the outer conductor paste The organic vehicle had to be completely burned out and the amount of oxygen added had to be controlled quite strictly to prevent oxidation of the copper conductor. For this reason, firing in a nitrogen atmosphere containing about 10 ppm of oxygen has been generally used. However, there are many problems such as unburned residue of the organic vehicle and defective soldering. For example, if the amount of oxygen doping is increased, and the outer conductor most susceptible to the firing atmosphere is copper, even a small amount of copper powder during firing is bonded to the inner conductor (via the via-hole conductor and the through-hole conductor). When oxidation occurs, alloying with an internal conductor (via a via hole or a through hole conductor) is likely to be insufficient, and electrical defects and soldering defects on the joint surface are likely to occur. In addition, when the oxygen doping amount is reduced, the residue of the organic vehicle is left unburned,
There is a problem such as a defective joint with the internal conductor.

[0005]

The present invention is directed to the general formula Ag _x C
u _1-x (where 0.01 ≦ x ≦ 0.4, atomic ratio), and the silver concentration on the grain surface is higher than 2.1 times the average silver concentration, and the silver concentration increases toward the grain surface. The average particle size having a region in which is increased is 0.1 to 20 μm, and 20
The average particle size is 0.1 to 10 μm and 10 with respect to 100 parts by weight of the copper alloy powder having 90% or more of the powder having a size of μm or less.
Glass frit in which 90% or more of powder having a size of μm or less is used.
1 to 20 parts by weight and an organic vehicle are contained, and the paste for the outer conductor of the low temperature fired multilayer circuit board whose inner conductor is made of copper or copper-silver alloy, and the paste of the composition are sintered. The general formula Ag _x Cu is characterized in that the silver concentration on the surface is 2 times or more of the average silver concentration.
_{The present} invention relates to a low-temperature fired multilayer circuit board including an outer conductor represented by _1-x (where 0.01≤x≤0.4, atomic ratio).

As a method for producing the copper alloy powder that can be used in the present invention, the atomizing method already applied for by the present inventor is preferable (USP 5091114). According to the disclosure, in an inert gas atmosphere, copper and silver having such a composition at a high temperature of several thousand and several hundred degrees are melted, the melt is atomized using a high-speed inert gas, and rapidly solidified to obtain a fine powder. Is a method of manufacturing.

When the amount x of silver is less than 0.01, sufficient oxidation resistance is not obtained during firing as an outer conductor, and sufficient bonding with the inner conductor made of copper or copper-silver alloy cannot be obtained. If it exceeds 0.4, migration of silver between the outer conductors is likely to occur. It is preferably 0.01 to 0.35, and more preferably 0.01 to 0.25. Also,
The silver concentration on the surface of the copper alloy powder that can be used in the present invention is higher than the average silver concentration, and there is a region where the silver concentration increases toward the grain surface, but the silver concentration on the surface is the average silver concentration. It is more than 2.1 times the concentration. If it is less than 2.1 times, not only the oxidation resistance of the conductor during firing is insufficient, but also the bonding with the internal conductor is insufficient. It is preferably 2.1 times or more and 40 times or less. Further, it is preferably 3 times or more and 30 times or less.

The external conductor paste of the present invention obtains sufficient electrical conduction by alloying with the internal conductor during firing. That is, since the copper alloy powder used in the present invention contains copper as a main component and has a high silver concentration on the surface, copper or a copper-silver alloy inner conductor (via hole or through hole conductor) and an outer conductor paste having such a composition are used. One of the advantages is that they are easily alloyed during firing. Also,
Since the outer conductor is most likely to be affected by the firing atmosphere, the oxidation resistance during firing is high, and sufficient electrical connection can be obtained, which is another advantage. Further, as an outer conductor after sintering, one of the advantages is that the average silver concentration is low and there is no problem of migration between conductors.

The copper alloy powder used in the present invention has an average particle size of 0.1 to 20 μm. If the average particle size is less than 0.1 μm, the amount of oxygen contained in the particles is high and a conduction failure during firing is likely to occur. If it exceeds 20 μm, the sinterability is insufficient,
Therefore, electrical connection with the internal conductor through the via hole or the through hole tends to be insufficient. The average particle size is preferably 0.1 to 10 μm. for that reason,
If the existence ratio of particles of 20 μm or less is not 90% or more, the contact point of sintering becomes insufficient. It is preferably at least 95%.

The average particle diameter used in the present invention means a volume cumulative average particle diameter. The measurement was performed by using a laser diffraction type average particle size measuring device (SALD1100 manufactured by Shimadzu) by completely dispersing the copper alloy particles in ethylene glycol as a solvent. The presence of powder having a particle size of 20 μm or more was similarly determined from the particle size distribution using a laser diffraction type average particle size measuring device.

The low temperature fired multilayer circuit board outer conductor paste of the present invention comprises glass frit and copper alloy powder 100.
It is contained in an amount of 0.1 to 20 parts by weight with respect to parts by weight, but the role of the glass frit is to give a strong adhesive force to the multilayer circuit board. The average particle size of the glass frit is 0.1 to 10 μm. The measurement was carried out in the same manner as the copper alloy powder, and a laser diffraction particle size distribution measuring device (S
ALD1100) was used for volume integration. When the average particle size is less than 0.1 μm, it is difficult to disperse in the paste, and when it exceeds 10 μm, insufficient sintering occurs, printability is poor, and sedimentation easily occurs. Preferably, the average particle size is 0.2 to 8 μm. Also 10μ
Those having a ratio of m or less of 90% or more can be used. 9
If it is less than 0%, alloying with the internal conductor is hindered. It is preferably 99% or more.

Further, the glass frit is less than 0.1 part by weight.
In the case of, there is not sufficient adhesive strength and it exceeds 20 parts by weight.
In this case, the sintering of the copper alloy powder will be insufficient. Preferably
Is 0.2 to 15 parts by weight. Glass frit ingredients
As PbO, SiO₂, B₂O₃, ZnO, Al
₂O₃The main component is at least one selected from O
As the glass frit used, for example, P
bO-SiO₂-B₂O₃, PbO-SiO₂-Zn
O, PbO-SiO₂-Bn₂O₃-ZnO, PbO-
SiO₂-CaO, PbO-SiO₂-BaO, PbO
-SiO₂-MgO, PbO-SiO₂-MnO, Pb
OB₂O₃, PbO-B₂O₃-ZnO, PbO-B
₂O₃-CaO-ZnO, PbO-B₂O₃-SiO₂
-CaO, PbO-B₂O₃-SiO ₂-MgO, Pb
O-SiO₂-Al₂O₃, PbO-SiO₂-B₂O
₃-Al₂O₃, PbO-B₂O₃-Al₂O₃, Pb
O-SiO₂-Al₂O₃-CaO, PbO-SiO₂
-Al₂O₃-MgO, PbO-B₂O₃-Al₂O₃
-CaO, SiO₂-B₂O₃Amorphous system, or
It is preferred to use a crystalline glass frit. Inside
However, a glass frit containing a PbO component is preferable. Moth
The role of the lath frit is as a low temperature firing multilayer circuit board
To improve the adhesion with the outer conductor of such composition
Yes, it is preferable to combine with a multilayer circuit board when firing
The softening point of the glass frit is 650 ° C or lower 3
A temperature of 00 ° C or higher is preferable, and 550 ° C or lower 3
It is preferably 50 ° C. or higher. In addition, the difference in the coefficient of thermal expansion is
It is preferably less than 80% with the substrate.

To the low temperature fired multilayer circuit board outer conductor paste of the present invention, it is preferable to add cuprous oxide powder in order to increase the adhesive strength and wettability with the glass frit. The average particle size of the cuprous oxide powder is 0.1 to
It is better to use the one with 10 μm. If it is less than 0.1 μm, the dispersibility in the paste is poor. If it exceeds 10 μm, the sintering of the copper alloy powder is hindered. It is preferably 0.1 to 7 μm. The cuprous oxide powder is 1
It is preferable that the proportion of powder of 0 μm or less is 90% or more. If it is less than 90%, not only the screen printability but also the sintering of the copper alloy powder is hindered. It is preferably at least 95%. The amount of cuprous oxide added is 0.1 to 100 parts by weight of the copper alloy powder.
15 parts by weight can be added and used. When it is less than 0.1, sufficient adhesive strength cannot be obtained, and when it exceeds 15 parts by weight, sintering of the copper alloy powder is hindered. It is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 7 parts by weight. Also in the case of cuprous oxide powder, the average particle size and particle size distribution were measured by volume integration in the same manner as in the measurement method of copper alloy powder. The ratio of 10 μm or less was obtained from the volume cumulative particle size distribution.

In addition, cupric oxide, bismuth oxide, lead oxide, magnesium oxide, zinc oxide, boron oxide, silica, cadmium oxide, in order to further improve the adhesiveness to the low temperature firing multilayer circuit board and the wettability. It is also possible to add 0.01 to 10 parts by weight of fine powder (preferably, an average particle diameter of 0.1 to 10 μm) to 100 parts by weight of the copper alloy powder.

The low-temperature fired multilayer circuit board outer conductor paste of the present invention contains an organic vehicle. The organic vehicle may be any known organic vehicle without any particular limitation. The role of the organic vehicle is to provide the paste with an appropriate viscosity and thixotropy, for example, a known organic binder such as ethyl cellulose, methyl cellulose, acrylic resin, butyral resin, etc. It is something to give. As the solvent, a known solvent can be used.

If necessary, coupling agents (titanium coupling agents, silane coupling agents), hydrogenated castor oil, colloidal silica, thixotropic agents such as polyethylene oxide, and higher fatty acids (eg stearic acid, linolenic acid). Acid, linoleic acid, palmitic acid, etc.) and their copper salts can also be added. The amount of the organic vehicle used is 1 to 200 with respect to 100 parts by weight of the copper alloy powder.
Parts by weight are preferred. Furthermore, 2-150 weight part is more preferable. Further, the additive is preferably 0.001 to 30 parts by weight with respect to 100 parts by weight of the copper alloy powder.

By printing the external conductor paste of the present invention,
When firing, it is preferable to fire in an inert atmosphere, but as the inert atmosphere, nitrogen, argon, hydrogen, or helium atmosphere is preferable. In particular, the nitrogen atmosphere is preferable from the economical viewpoint. When firing in an inert atmosphere, it is preferable to fire at a low temperature of about 350 to 1050 ° C. to form a crystal body. At this time, it is more preferable to dope oxygen to 300 to 600 ° C. in order to burn out the organic vehicle sufficiently. For example, 1-1000
It is preferably doped with ppm. As the firing furnace, a resistance heating furnace or a known firing furnace such as a near infrared furnace may be used, but a belt conveyor type furnace is preferable. The firing time is not particularly specified, but is 3 minutes to 120 at the maximum firing temperature.
Minutes are preferred.

In the outer conductor of the present invention formed as a sintered body by firing at the above temperature, it is particularly preferable that the silver concentration on the conductor surface is higher than the average silver concentration. The silver concentration on the surface of the outer conductor is preferably at least twice the average silver concentration, and further 3
It is preferably not less than twice and not more than 50 times. When it is less than 2, the solderability becomes poor. That is, since the temperature is for sintering, the sintering starts from the contact point between the particles rather than the melting of the particles. At this time, the surface of the obtained outer conductor also has a conductor surface having a high silver concentration. However, the firing temperature is 1
If the temperature exceeds 100 ° C., the outer conductor is melted and fluidized so that the shape of the conductor is broken and the silver concentration is averaged. Further, if the oxygen doping amount enters excessively, the copper concentration on the conductor surface will rather increase.

The low temperature fired multilayer circuit board outer conductor of the present invention is
Due to the high silver concentration on the surface, lanthanide series, rutheni
U-type external resistor, glass paste, insulation paste
In addition, even when coated on the outer conductor and heat treated,
Oxidizing, little deterioration of electrical and solder wettability
There are advantages. For low temperature firing multilayer substrates that can be used in the present invention
As a green sheet (before stacking and firing)
A known material can be used for
Na (Al ₂O₃), Forsterite (2MgO ・ Si
O₂), Mullite (3AI₂O₃・ 2SiO₂), Co
Jillite (2MgO / 2Al₂O₃・ 5 SiO₂), C
aZrO₃With B as the main component₂O₃, SiO₂Glass
Ingredients added and β-spodumene (Li₂O
Al₂O₃・ 4SiO₂) System and BaO / SnO₂, T
iO₂, B₂O₃Consisting of BaSn (BO₃)₂System, B
aTi (BO3) 2 system, Al₂O₃, CaO, Si
O₂, MgO, B₂O₃System consisting of etc., BaO, Al
₂O₃, SiO₂A glass system consisting of and additives is preferred
Yes.

For example, PbO-SiO₂-B₂O₃−
CaO glass + Al₂O₃, CaO-Al₂O₃-S
iO₃-B₂O₃System glass + Al₂O₃, BaO-Al
₂O ₃-SiO₃-B₂O₃Glass, SiO₂-B₂
O₃System glass + Al₂O₃+ CaZrO₃, SiO₂−
B₂O₃System glass + Al₂O₃, SiO₂-B₂O₃system
Glass + Al₂O₃2MgO-SiO₂, 2MgO-
2 Al₂O₃-5 SiO₂System, ZnO-MgO-Al₂
O₃-SiO₂System, BaSnB₂O₆-BaTiB₂O
₃System, Al₂O₃-CaO-SiO₂-MgO-B₂O
₃System, BaO-SiO₂-Al₂O₃-CaO-B₂O
₃System, etc. The thickness of the green sheet
5 μm to 2000 μm can be used
However, it is not specified.

The silver concentration on the surface of the copper alloy powder used in the present invention and the silver concentration on the surface of the outer conductor obtained by the outer conductor paste for a low temperature firing multilayer circuit board of the present invention are measured by XPS (X-ray photoelectron Spectroscopic analyzer: XSAM800 manufactured by KRATOS) was used. Measurement conditions: Carbon double-sided tape was attached to the sample table, copper alloy powder or external conductor chips (barred without overcoating) were attached to cover the entire surface, and vacuum deaeration was sufficiently performed, followed by argon atmosphere < 10 ⁻⁸ torr MgKα ray Sample current 10 mA 12 kV Measurement was performed at an extraction angle of 90 degrees. Etching conditions: Argon gas 3 keV 10 ⁻⁷ t
orr 5 minutes Measurement and etching are alternately repeated 5 times under the above conditions, and the average value of the first 2 measured values is the silver concentration on the surface x = Ag /
(Ag + Cu), copper concentration 1-x = Cu / (Ag + Cu)
And The average silver concentration of the copper alloy powder and the outer conductor was measured by dissolving the sample in concentrated nitric acid solution and then dissolving the sample in concentrated nitric acid using ICP (high frequency inductively coupled plasma emission spectrometer). It was measured.

In the migration test, an outer conductor width of 80 μm and an interval of 100 μm were prepared and the temperature was 60 ° C. and 90%.
The migration time was measured when 50 DCV was applied to the conductor spacing in relative humidity. A time of 5 hours or more was evaluated as good and a time of less than 5 hours was evaluated as bad. Further, the electrical connection on the connection surface between the inner conductor and the outer conductor was judged by measuring the impedance between the conductor of the second layer and the outer conductor connected by the via hole.

Solder wettability (solderability) of the outer conductor
Was dipped in a 230 ° C. tin / lead eutectic solder bath for 10 seconds to make the wet area 95% or more good. Anything less than that was considered defective. The impedance of the outer conductor was measured using the 4-terminal method. Examples will be shown below.

[0024]

【Example】

[0025]

[Powder Preparation Example 1] 571.5 g of copper particles and 108 g of silver particles
Thoroughly mixed in a graphite crucible in a nitrogen atmosphere at 1700
It melted by heating to ℃. The melt was jetted into the nitrogen atmosphere from the tip of the crucible, and simultaneously with the jetting, 40 kg / cm ² of nitrogen gas was jetted to the melt to atomize. The obtained powder had an average particle size of 11 μm. The silver concentration on the surface of the copper alloy powder was 0.5, 0.4, 0.3, 0.2, and 0.14, and the silver concentration on the surface was 0.45. The average silver concentration x was 0.1, and the surface silver concentration was 4.5 times the average silver concentration.

A production example of a copper alloy powder produced in the same manner is shown below.

[0027]

[Table 1]

[0028]

Example 1 Among the copper alloy powders obtained in Powder Preparation Example 1,
A powder having a size of 10 μm or less was classified. The obtained powder had an average particle size of 4.2 μm (20 μm or less and 99% or more).
10 g of the powder and PbO—B ₂ O ₃ —ZnO glass frit (average particle size 5 μm, 10 μm or less 99% or more)
0.2 g, ethyl cellulose 0.05 g acrylic resin 0.5 g, terpenol 1 g, butyl carbitol 2
g, butyl carbitol acetate 2 g, cuprous oxide powder (average particle diameter 2 μm, 10 μm or less 99% or more).
1 g, palmitic acid 0.1 g, silicone oil 0.00
1 g, a titanium coupling agent 0.0001 g, and hydrogenated castor oil 0.002 g were mixed to form a paste. Separately, a known copper paste was printed as a circuit on a green sheet formed by adding B ₂ O ₃ , CaO, and MgO to mullite, and 10 layers were similarly prepared. Further, after printing the above-prepared outer conductor paste on the outer conductor of the outer layer green sheet, the via hole for internal connection or the through hole, the paste was laminated by a known method and baked at 700 ° C. for 60 minutes in nitrogen. At this time, 300 ppm of oxygen was doped up to 500 ° C.

When the silver concentration on the surface of the obtained conductor was measured, the silver concentration was 0.6, 0.52, 0.45 from the surface.
0.4 and 0.3, the surface silver concentration was 0.56, which was 2.8 times the average silver concentration. The outer conductor and the inner conductor in the surface layer were well joined, and almost no increase in the resistance value was observed at the inner and outer joint surfaces. Further, as a printed resistor, a lanthanum boride type resistor was printed between the conductors and fired at 900 ° C. in a nitrogen atmosphere. No increase in resistance was observed due to the conductor electrode. Further, even when overcoat glass was printed and treated in a nitrogen atmosphere at 550 ° C., discoloration of the conductor surface was not observed.

The migration test was successful. The impedance of the outer conductor was also good.

[0031]

[Example 2] 4 of the copper alloy powders obtained in Powder Preparation Example 1
The powder having a particle size of μm or less was classified. The obtained powder had an average particle diameter of 2 μm (20 μm or less and 99% or more). The resulting classification powder _{10g, PbO-B 2 O 3} -ZnO-SiO 2
Glass frit (average particle size 0.3 μm, 10 μm or less 99% or more) 0.3 g, cuprous oxide powder (average particle size 0.2 μm, 10 μm or less 99% or more) 0.1 g, ethyl cellulose 0.02 g, acrylic resin 0.04g, methylcellulose 0.001g, butyral resin 0.02
g, butyl carbitol acetate 0.6 g, cuprous oxide powder (average particle size 0.2 μm, 10 μm or less 99% or more) 0.1 g, stearic acid 0.0001 g, and anti-settling agent 0.001 g are thoroughly mixed. And made a paste.

Separately, forsterite is added to B ₂ O ₃ and Si.
A paste using a known copper-silver alloy (5% by weight of silver) is printed on a green sheet in which a via hole is formed by adding O ₂ , and a known dielectric glass paste is printed on the green sheet, and copper is also used in the via hole. -Silver alloy (5% by weight of silver) conductor paste was printed to produce 6 green sheets in the same manner. The outer conductor paste prepared above is printed on the outer layer green sheet on the outer conductor, inner conductor connecting via hole or through hole, and laminated by hot pressing.
It was co-fired in nitrogen at 00 ° C. for 2 hours.

Up to 550 ° C., 500 ppm of oxygen was doped. The silver concentration on the surface of the obtained outer conductor was 0.9,
It was 0.8, 0.7, 0.5, 0.4, and the surface silver concentration was 0.85, which was 3.4 times the average silver concentration. The outer conductor and the inner conductor thus obtained were joined well, and the conductivity was not found to increase in resistance at the joint surface. Moreover, the result of the migration test was good.

Further, a lanthanum boride-based resistor paste and a dielectric glass paste were coated and fired in a nitrogen atmosphere. The change in resistance value at the junction between the resistor and the outer conductor was good at 0.1% or less.

[0035]

[Example 3] 2 of the copper alloy powders obtained in Powder Preparation Example 3
The powder having a particle size of μm or less was classified. The obtained classified powder had an average particle diameter of 0.9 μm (20 μm or less and 99% or more).
Classifying powder _{10g, PbO-SiO 2 -B 2} O 3 -ZnO
Glass frit (average particle size 1 μm, 10 μm or less 99
% Or more) 0.02 g, acrylic resin 1 g, butyl cellosolve 0.2 g, butyl carbitol acetate 0.1
g, silicone oil 0.001 g, thixotropic agent 0.000
1 g, cuprous oxide powder (average particle size 0.2 μm, 10 μm
Below 99%) 0.8 g, cadmium oxide 0.1 g,
Bismuth oxide 0.1g (average particle size 0.5μm, 10μ
m or less and 99% or more). Palmitic acid 0.1 g and stearic acid 0.1 g were mixed to form a paste.

Separately, B ₂ O ₃ was added to alumina and cordierite.
A known copper-silver alloy (30% by weight of silver) paste was used to form a circuit on the green sheet in which the via hole was formed. Furthermore, by printing a known dielectric paste,
After printing on the via holes as well, eight layers of green sheets were similarly prepared. Further, after printing the prepared external conductor paste in via holes or through holes for connecting the external conductor and the internal conductor of the outer layer green sheet, they were laminated by hot pressing and cofired in 900 ° C. nitrogen for 1 hour.

At this time, 300 ppm of oxygen was doped up to 500.degree. When the silver concentration on the surface of the obtained outer conductor was measured, the silver concentration was 0.88, 0.8, 0.
7, 0.6, 0.5, and the surface silver concentration was 0.84. The average silver concentration was 0.25 and the surface silver concentration was 3.3 times the average silver concentration. The outer conductor and the inner conductor were joined well, and no increase in resistance was observed at the joint surface. Moreover, the result of the migration test was good.

Further, an insulating glass paste was printed on the outer conductor and fired in a nitrogen atmosphere at 550 ° C. At this time, 5
Up to 00 ° C., 100 ppm of oxygen was doped. No discoloration or the like due to the glass coating of the obtained outer conductor circuit was observed.

[0039]

[Example 4] 3 of the copper alloy powders obtained in Powder Preparation Example 4
The powder having a particle size of μm or less was classified. The obtained powder is 1.2 on average.
It was μm (20 μm or less and 99% or more). Classification powder 10
g, PbO—SiO ₂ —CaO—ZnO—B ₂ O ₃ glass frit (average particle size 0.5 μm, 10 μm or less 99
% Or more) 1 g, copper oxide 0.1 g, bismuth oxide 0.00
2 g, cuprous oxide (average particle size 0.2 μm, 10 μm or less 99% or more) 0.025 g, ethyl cellulose 0.2
g, acrylic resin 0.2 g, butyral resin 0.1 g,
Stearic acid 0.0001 g, thixotropic agent 0.0002
g, butyl carbitol acetate 0.5 g, and α-terpenol 0.5 g were sufficiently mixed to obtain a paste.

Separately, β-spodumene and BaO-Al ₂
A known copper paste was printed as a conductor circuit on a green sheet made of O ₃ —SiO ₂ glass in which a via hole was already formed. Further, after printing via holes and ruthenium-based resistor paste, 6 green sheets were similarly prepared. Printing was performed using the above-prepared external conductor paste as via holes or through holes for connecting the external conductor and internal conductor of the outer layer green sheet. Further, they were laminated by a hot press and baked in a nitrogen atmosphere at 700 ° C. for 30 minutes. At this time, oxygen up to 550 ℃ 1
Doped with 00 ppm. No increase in resistance was observed at the joint surface between the inner conductor and the outer conductor. The migration test was good.

The silver concentration on the surface of the outer conductor is 0.
3, 0.25, 0.24, 0.2, 0.15, the surface silver concentration was 0.275, and the average silver concentration was 5.
It was 5 times.

[0042]

[Comparative example]

[0043]

Comparative Example 1 63.5 g of copper particles and 108 g of silver particles were mixed and put in a graphite crucible and heated and melted at 1700 ° C. in a nitrogen atmosphere. The melt was jetted into the nitrogen atmosphere from the tip of the crucible, and at the same time, 40 kg / cm ² G of nitrogen gas was jetted to the melt to atomize. The obtained powder had an average particle size of 13 μm. The average silver concentration x was 0.5 and the average copper concentration was 0.5. Of the obtained copper alloy powder, a powder having a particle size of 10 μm or less was classified. The average particle size of the powder after classification is 5 μm (20 μm or less and 99% or more)
Met. Copper alloy powder 10g after classification, PbO-B ₂ O
_3- SiO ₂ (average particle size 1 μm, 10 μm or less 99%
(Above) 0.2 g of glass frit, cuprous oxide powder (average particle size 0.5 μm, 10 μm or less 99% or more) 0.01
g, ethyl cellulose 0.3 g, terpenol 0.6
g, butyl carbitol acetate 0.3 g, and an anti-settling agent 0.001 g were sufficiently mixed to obtain a paste.

Commercially available copper paste was mixed with alumina and BaO-B ₂
Printing was also performed on the green sheet of O ₃ —SiO ₂ glass on which a via hole was already formed and on the via hole. Further, after printing the dielectric material, six green sheets were similarly prepared. The above-prepared external conductor paste was printed on the outer layer green sheet on the via holes or through holes for connecting the external conductor and the internal conductor, followed by thermocompression bonding with a hot press and simultaneous firing at 700 ° C. for 50 minutes in the air. Further, after printing a known lanthanum boride type resistor, it was baked at 900 ° C. for 10 minutes.

When a migration test was performed on the outer conductor produced by firing, the migration was remarkable. Further, the silver concentration on the surface of the outer conductor is 0.
It was 1, 0.2, 0.3, 0.4 and 0.5, and the surface silver concentration was 0.15, which was 0.3 times lower than the average silver concentration.

[0046]

Comparative Example 2 Commercially available copper particles (average particle size 2 μm, 20 μm
m inclusive 99%) 10g, PbO-CaO -SiO 2
-B ₂ O ₃ (average particle size 1 μm, 10 μm or less 99% or more) 1 g, acrylic resin 0.1 g, terpenol 0.1
g, butyl cellosolve 0.3 g, butyl carbitol acetate 0.5 g, cupric oxide powder (average particle size 1 μm,
0.2 g of 10 μm or less and 99% or more) and 0.0002 g of a titanium coupling agent were sufficiently mixed to obtain a paste.
The produced external conductor paste was printed as via holes or through-hole conductors for connecting the external conductor and the internal conductor of the outer layer green sheet, and then laminated with 6 green sheets produced in the same manner as in Comparative Example 1 by hot pressing. Further, it was baked in a nitrogen atmosphere at 600 ° C. for 60 minutes (100 ppm oxygen was doped up to 500 ° C.).
The connection between the outer conductor and the inner conductor was not so good, and the resistance value increased. Further, a lanthanum boride-based resistor was printed and fired at 900 ° C. for 10 minutes in a nitrogen atmosphere. The matching with the resistor was poor and the noise was high. Also, the solderability of the external conductor was poor.

[0047]

Comparative Example 3 254 g of copper particles and 108 g of silver particles were mixed and put into a graphite crucible, which was heated and melted to 1700 ° C. in a nitrogen atmosphere. The melt was jetted into the nitrogen atmosphere from the tip of the crucible, and at the same time as the jetting, 7 kg / cm ² G of nitrogen gas was jetted to the melt for atomization. The obtained copper alloy powder had an average particle diameter of 30 μm.

The average silver composition x of the copper alloy powder was 0.2 and the average copper composition was 0.8. The silver concentration on the surface was 0.8, 0.76, 0.7, 0.6, 0.5 from the surface, and the silver concentration on the surface was 0.78. The silver concentration on the surface was 3.9 times the average silver concentration. 10 g of the obtained copper alloy powder
(Average particle size 30 μm, 20 μm or less 15%), PbO
-B ₂ O ₃ -SiO ₂ (average particle size 1 μm, 10 μm or less 99% or more) 0.3 g, terpenol 0.2 g, butyl cellosolve 0.2 g, cuprous oxide (average particle size 1 μm
m, 10 μm or less and 99% or more) 0.5 g and a titanium coupling agent 0.003 g were sufficiently mixed to obtain a paste.

Alumina and BaO--Al ₂ O ₃ --SiO ₂
Commercially available copper paste was printed on a green sheet having a via hole formed of glass, the copper paste was also printed on the inside of the via hole, and a publicly known resistance paste was also printed to produce 6 green sheets in the same manner. The prepared outer conductor paste was printed on the outer layer green sheet as via holes or through holes for connecting outer conductors and inner conductors.
Furthermore, after laminating with a hot press, it was co-fired in nitrogen at 700 ° C. for 60 minutes (oxygen 300 ppm up to 500 ° C.
Dope). The average particle diameter was large, sufficient sinterability was not obtained, and the outer conductor had high resistance. Also, the connection with the internal conductor was poor, and the resistance value increased remarkably. Also, the solder wettability was poor.

[0050]

[Comparative Example 4] 1 of the copper alloy powders prepared in Powder Preparation Example 5
Powder of 0 μm or less (average silver concentration 0.12, average particle size 4.5 μm, 20 μm or less 99% or more) 10 g, PbO
-B ₂ O ₃ -SiO ₂ glass frit (average particle size 10
μm, 10 μm or less 50%) 1 g, cuprous oxide powder (average particle size 0.5 μm, 10 μm or less 99% or more) 0.00
1 g, ethyl cellulose 0.3 g, and terpenol 3 g were mixed into a paste. The prepared outer conductor paste was printed on the same outer layer green sheet as in Comparative Example 3 as a via hole or a through-hole conductor for connecting an outer conductor and an inner conductor, and then copper was printed as an inner conductor prepared in the same manner as in Comparative Example 3. After stacking together with the above-mentioned six green sheets by hot pressing, it was baked in a nitrogen atmosphere at 600 ° C. for 40 minutes (oxygen 300 ppm was doped to 500 ° C.). Sufficient sinterability was not obtained, and the resistance value of the outer conductor was high. Further, the resistance value at the joint surface with the internal conductor was very high. However, the migration was good. Also, the solder wettability was poor.

[0051]

Comparative Example 5 The copper alloy powder obtained in Powder Preparation Example 1
It was classified by μm. The obtained powder after classification had an average particle size of 4.5 μm (20 μm or less and 99% or more). 10 g of powder after classification, PbO—SiO ₂ —ZnO (average particle diameter 30 μm, 10 μm or less 5%) glass frit 0.3
g, 0.5 g of ethyl cellulose, and 1 g of terpenol were sufficiently mixed to obtain a paste.

Commercially available copper paste was printed on a green sheet having via holes formed of forsterite and B ₂ O ₃ . After printing on the via hole, eight green sheets were similarly prepared. The prepared external conductor paste was printed on the outer layer green sheet as via holes or through holes for connecting the external conductor and the internal conductor, and then laminated and thermocompression bonded by hot pressing. Furthermore, 80
It was fired in a nitrogen atmosphere at 0 ° C. for 60 minutes (900 ppm oxygen up to 500 ° C.). In the obtained copper alloy conductor, the glass frit was deposited in the conductor film and the resistance was high.
The silver concentration on the surface of the outer conductor is 0.15, 0.18,
0.2, 0.2, 0.2 and the surface silver concentration is 0.1
At 65, it was lower than the average silver concentration.

[0053]

Comparative Example 6 The copper alloy powder obtained in Powder Preparation Example 1
It was classified by μm. The obtained classified powder has an average of 4.5 μm (2
0 μm or less and 99% or more). Powder after classification 10
g, PbO—SiO ₂ —B ₂ O ₃ (average particle size 1 μm,
10 μm or less and 99% or more) 5 g of glass frit, 0.3 g of ethyl cellulose, 1 g of terpenol, and 0.002 g of titanium coupling agent were sufficiently mixed to obtain a paste.

Commercially available copper paste was printed on both a circuit and a via hole on a green sheet made of BaO--Al ₂ O ₃ --SiO ₂ glass in which the via hole was previously formed. Further, a columnar boride-based resistor paste was printed to produce 6 green sheets in the same manner. Via holes or through holes for connecting the outer conductor and inner conductor of the outer layer green sheet were fired in air at 700 ° C. for 1 hour. further,
A silver conductor was similarly formed in the via hole for connection with the external conductor, and then the copper alloy paste was printed. After printing, it was heated and baked in a nitrogen atmosphere at 600 ° C. for 10 minutes (5
400 ppm oxygen was doped up to 00 ° C). After firing, glass was deposited on the surface of the outer conductor, and sufficient conductivity was not obtained at the joint surface with the inner conductor.

[0055]

[Comparative Example 7] The copper alloy powder obtained in Powder Preparation Example 1 was replaced with 10
It was classified by μm. The obtained classified powder has an average particle diameter of 4.5μ.
It was m. Powder after classification (average particle size 4.5 μm, 2
0 μm or less and 99% or more) 10 g, ethyl cellulose 0.
A paste was prepared by thoroughly mixing 3 g, 0.4 g of terpenol and 0.3 g of butyl carbitol acetate.

Screen printing was performed as an outer conductor of the multilayer circuit board prepared in Comparative Example 6. After printing, it was heated and baked in a nitrogen atmosphere at 600 ° C for 10 minutes (oxygen 4
00 ppm dope). The calcined copper alloy conductor lacked adhesive strength to the multilayer substrate and was easily peeled off from the substrate.

[0057]

Comparative Example 8 Of the copper alloy powders obtained in Powder Preparation Example 1, 1
10 g of powder of 0 μm or less (99% or more of powder having an average particle size of 4.5 μm and 20 μm or less), PbO—B ₂ O ₃ —Si
O ₂ glass frit (average particle size 1 μm, 10 μm or less 99% or more) 4 g, cuprous oxide (average particle size 18 μm,
10 μm or less 10%) 3 g, ethyl cellulose 0.7
g, butyl carbitol acetate 2 g, and an anti-settling agent 0.001 g were sufficiently mixed to obtain a paste. The obtained paste was screen-printed as an outer conductor of the same multilayer circuit board as in Comparative Example 7. After printing, it was baked at 800 ° C. for 30 minutes. (Oxygen 100 ppm doping up to 500 ° C.). The sintered copper alloy conductor was insufficiently sintered, and sufficient conductivity was not obtained at the joint surface with the internal conductor.

[0058]

According to the present invention, the general formula Ag _x Cu _1-x (0.
01 ≦ x ≦ 0.4, atomic ratio), the average particle diameter is 0, which has a region in which the silver concentration on the grain surface is higher than 2.1 times the average silver concentration and the silver concentration increases toward the grain surface. 1 ~
1 with an average particle size of 0.1 to 10 μm with respect to 100 parts by weight of a copper alloy powder of 20 μm and 20 μm or less of 90% or more
Glass frit 0.2 to 30 with 0 μm or less of 90% or more
It is intended to provide a paste for an external conductor of a low-temperature fired multilayer circuit board consisting of parts by weight and an organic vehicle, but not only has excellent adhesion to the board, solder wettability, migration resistance, and oxidation resistance, It is intended to provide an internal conductor made of copper or a copper-silver alloy, an external conductor having excellent electrical bonding property because it is easily alloyed during firing, and a low temperature firing multilayer circuit board.

Claims (5)

[Claims] 1. The general formula Ag _x Cu _1-x (provided that 0.0
1 ≦ x ≦ 0.4, atomic ratio), and the average particle has a silver concentration higher than 2.1 times the average silver concentration and has a region where the silver concentration increases toward the particle surface. 9 powders having a diameter of 0.1 to 20 μm and 20 μm or less
0% or more, with respect to 100 parts by weight of the copper alloy powder, the average particle size is 0.1 to 10 μm and 10 μm.
Glass frit in which 90% or more of m or less powder is 0.1
To 20 parts by weight of an organic vehicle, a paste for a low-temperature fired multilayer circuit board outer conductor having copper or a copper-silver alloy as an inner conductor 2. The paste according to claim 1, which has an average particle size of 0.1 to 10 μm and 90% of powder having a particle size of 10 μm or less.
A low-temperature fired multilayer circuit board outer conductor paste obtained by adding 0.1 to 15 parts by weight of the above cuprous oxide powder to 100 parts by weight of a copper alloy powder. 3. The glass frit according to claim 1 or 2, wherein the glass frit contains at least one oxide component selected from PbO, SiO ₂ B ₂ O ₃ , ZnO and Al ₂ O _3. A low-temperature-fired multilayer circuit board outer conductor paste characterized by the following: 4. The low-temperature fired multilayer circuit board outer conductor paste according to claim 1, which is printed on an outer layer of a low-temperature fired multilayer circuit board having copper or a copper-silver alloy as an inner conductor and sintered. The general formula Ag _x Cu _1-x (where
0.01 ≦ x ≦ 0.4, atomic ratio) A low temperature fired multilayer circuit board having an outer conductor. 5. A low temperature fired multilayer circuit board, wherein the silver concentration on the surface of the outer conductor according to claim 4 is higher than twice the average silver concentration.