JPH0762275A - Conductor paste for baked ceramic substrate - Google Patents

Abstract

PURPOSE:To obtain a conductor paste for baked ceramic substrate giving a baked film having excellent adhesive strength, especially adhesive strength after thermal aging treatment, solder wettability and electrical conductivity by baking on a substrate. CONSTITUTION:This conductor paste for baked ceramic substrate containing Al2O3 is produced by dispersing (A) 100 pts.wt. of a copper alloy powder expressed by the general, formula AgxCu1-x ((x) is atomic ratio satisfying 0.001<=x<=0.4), having higher silver concentration at the surface of the particle than the average silver concentration and containing a region near the surface of the particle to increase the silver concentration toward the surface, (B) 0.1-30 pts.wt. of glass frit, (C) 0.2-2 pts.wt. of MnO2 powder and (D) 0.3-3 pts.wt. of Cr2O3 powder in an organic vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor paste,
In particular, the present invention relates to a conductor paste which is printed and fired on the surface of a ceramic fired substrate containing Al ₂ O ₃ .

[0002]

2. Description of the Related Art Conventionally, a conductive thick film paste is known in which a conductive metal powder and a glass frit are dispersed in an organic binder and a solvent as necessary, and as the conductive metal powder, silver, Silver-palladium, silver-platinum, gold, copper and the like are known. However, there were problems in both cases. When silver is used as the conductive powder, migration easily occurs between patterns such as circuits. In the case of silver-palladium, the impedance is too high to be used as a fine line. In the case of silver-platinum, there is still a problem with migration, and gold is too costly. When copper is used as the conductor powder, it is necessary to perform firing in an inert atmosphere, but unless the amount of oxygen added for completely firing the organic vehicle is strictly controlled, the organic vehicle remains unburned. Occurs, or the conductor is oxidized, so that the predetermined characteristics cannot be obtained.

Further, in the paste containing copper as the conductive particles, there is a problem that the adhesive strength with the ceramic substrate containing Al ₂ O ₃ , particularly the adhesive strength with the substrate after use under high temperature for a long time is lowered. There is. As a means for improving the adhesive strength, it is known to add copper oxide, cuprous oxide, bismuth oxide, etc., but by adding these, solder wettability inhibition, conductivity inhibition, etc. However, it is difficult to add the amount necessary to obtain a predetermined adhesive strength.

Further, a ceramic fired substrate containing a large amount of a glass component has come to be used in comparison with a conventional ceramic fired substrate containing 90% by weight or more of Al ₂ O ₃ , but it is printed on the surface of the substrate. In the conductor paste, the glass contained in the paste diffuses on the conductor surface during the firing process, and as a result, the solder wetting of the conductor is reduced,
Moreover, since the adhesive strength, particularly the adhesive strength after aging, is reduced, there is a problem that the reliability as a substrate is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to Al ₂ O ₃
Provided is an electrically conductive paste for a ceramic fired substrate, which has excellent adhesive strength of a fired film printed on a ceramic fired substrate containing a metal, particularly excellent adhesive strength after thermal aging, and also has excellent solder wettability and electrical conductivity. .

[0006]

The present invention provides a general formula Ag _x
Cu _1-x (however, 0.001 ≦ x ≦ 0.4, atomic ratio)
And the silver concentration on the grain surface is higher than the average silver concentration, and the glass frit is 0.1 parts by weight with respect to 100 parts by weight of the copper alloy powder having a region where the silver concentration increases toward the surface in the vicinity of the grain surface. ~ 30 parts by weight, MnO ₂ powder 0.2-2
Parts by weight and 0.3 to ₃ parts by weight of Cr ₂ O ₃ powder dispersed in an organic vehicle, Al ₂ O ₃
It is a conductor paste for a ceramic fired substrate containing.

The present invention will be described in detail below. The preparation of the copper alloy powder used in the present invention is described in US Pat.
The method described in the specification No. 40 is preferable. According to the disclosure, it is prepared by atomizing a melt of silver and copper with a high-pressure inert gas, and it is particularly preferable to use nitrogen gas or helium gas as the inert gas. The amount of oxygen and water contained in the inert gas is preferably 1% or less, more preferably 0.1% or less.

The copper alloy powder used in the present invention is represented by the general formula Ag _x Cu _1-x (where 0.001≤x≤0.4, atomic ratio), but when x is less than 0.001 Sufficient solder wettability and adhesive strength cannot be obtained. If x exceeds 0.4, silver migration between the electrodes becomes a problem. Preferably, 0.02 ≦ x ≦ 0.35. The copper alloy powder used in the present invention has a surface silver concentration higher than the average silver concentration, but is preferably 2.3 times or more. If it is less than 2.3 times, the copper concentration on the particle surface is high, and sufficient solder wettability and adhesive strength cannot be obtained, which is not preferable. It is more preferably 3 times or more and 80 times or less.

The shape of the particles is preferably spherical, but particles slightly deformed from the spherical shape may be used. For example, scaly,
Examples include dendritic shape. When the flaky powder is used, it is preferable to mechanically deform a spherical powder obtained by an inert gas atomizing method such as a ball mill or a stamp mill before use. In particular, flaky powder having a ratio of major axis (longest diameter of particles) to thickness of 2 or more is preferable.

For the silver concentration and average silver concentration on the surface of the copper alloy powder used in the present invention, the values measured by the following method were used. XPS (X-ray photoelectron spectroscopy analyzer: K
RATOS, XSAM800) was used. Etching condition: 10 ^-7 torr Argon Accelerating voltage 2k
eV 5 minutes Measurement conditions: 10 ⁻⁸ torr Argon Magnesium Kα ray Voltage 12 keV, current 10 mA Measurement and etching were repeated 5 times, and the average value of the first 2 measured values was defined as the surface silver concentration. That is, the silver concentration on the surface was Ag / (Ag + Cu) (atomic ratio), and the copper concentration on the surface was Cu / (Ag + Cu).

The average silver concentration was determined by dissolving the conductive powder in a concentrated nitric acid solution and then using an ICP (high frequency inductively coupled plasma emission spectrometer, Seiko Denshi JY88P2). Also,
The average particle size of the copper alloy powder used in the present invention is 0.1 to 1
0 μm is preferable. 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 is likely to occur, which is not preferable. More preferably, the average particle size is 0.2 to 7 μm. Also, among the existing particles, 15μ
It is preferable that the content of particles having a particle size of less than m is 90% or more. That is, when the particle size of less than 15 μm is less than 90%, it is not preferable because the print line may be blurred or the sintering may be insufficient.

Regarding the average particle size and particle distribution of the copper alloy powder used in the present invention, a laser diffraction type particle size distribution measuring device (SALD1100: manufactured by Shimadzu Corporation) was used.
0.01 to 1 g of copper alloy powder in ethylene glycol liquid
The measurement was performed by dispersing with an ultrasonic oscillator at a concentration of / cc. As the measured value, a particle size distribution based on volume was used. A value of 50% was used as the average particle size on a volume conversion basis.

The oxygen content of the copper alloy powder, which is a conductive powder, is preferably small for the oxidation resistance and conductivity of the contacts, and is preferably 2000 ppm or less. More preferably, it is 1000 ppm or less. The oxygen content means the total content on the surface and inside of the particle. The oxygen content was measured by heating 2 g of a copper alloy powder sample having such a composition with an oxygen / nitrogen analyzer (EMGA650: manufactured by Horiba Ltd.) to 2000 ° C.

In the present invention, it is most important to use a predetermined amount of MnO ₂ powder and Cr ₂ O ₃ powder together with the above copper alloy powder. The MnO ₂ powder is composed of glass components in the conductor paste and Al ₂ in the ceramic fired substrate.
It has the effect of reacting with O ₃ to improve solder wettability and adhesive strength after high temperature aging, but its addition increases the sheet resistance. Further, CrO ₂ powder is used as a glass component in the conductor paste and Al ₂ O ₃ in the ceramic fired substrate.
Reacts with to improve solder wettability but deteriorates the adhesive strength after high temperature aging. For these reasons, each alone cannot be added in an amount necessary to obtain a predetermined effect in improving solder wettability, adhesive strength after high temperature aging and sheet resistance. But,
By using the MnO ₂ powder and the Cr ₂ O ₃ powder together, a conductor paste having excellent adhesive strength, solder wettability and sheet resistance can be obtained.

The mixing ratio of MnO ₂ powder is 1% of copper alloy powder.
It is necessary to be 0.2 to 2 parts by weight, preferably 0.3 to 1.5 parts by weight, relative to 00 parts by weight. 0.
If it is less than 2 parts by weight, the adhesive strength after high temperature aging is extremely deteriorated. On the other hand, if it exceeds 2 parts by weight, the sheet resistance increases. The compounding ratio of Cr ₂ O ₃ powder is 100% copper alloy powder.
It is necessary that the amount is 0.3 to 3 parts by weight, and preferably 1.5 to 2.5 parts by weight. If it is less than 0.3 parts by weight, the solder wettability and the adhesive strength after high temperature aging are low, and especially the solder wettability is extremely lowered, while if it exceeds 3 parts by weight, the solder wettability is lowered and the sheet resistance is increased. Occurs.

MnO ₂ powder and Cr used in the present invention
The average particle size of the ₂ O ₃ powder is preferably 3 μm or less. The glass frit used in the present invention is for melting at a predetermined temperature to firmly bond the metal powders or the metal conductor to the substrate. Known glass frits can be used for the conductor paste of the present invention, but those that recrystallize when heat-treated at 600 ° C. to 900 ° C. are preferable. Particularly preferably B ₂ O ₃ —SiO ₂ —
_{ZnO, B 2 O 3 -SiO 2} -PbO, PbO-ZnO
The _{-B 2 O 3, PbO-B} 2 O 3 is obtained by the main component. When a glass frit that does not recrystallize is used, when the resistor paste is printed after firing the conductor paste and firing is performed again, the glass component in the conductor paste remelts and exudes to the conductor surface, resulting in solder wettability. Is not preferable because it worsens.

The particle size of the glass frit is preferably 0.01 to 30 μm, more preferably 0.1 to 5 μm, in order to obtain sufficient sinterability. The average particle size described here indicates the average particle size measured by the laser diffraction method. The amount of the glass frit used is 0.1 to 30 parts by weight with respect to 100 parts by weight of the copper alloy powder, but if it is less than 0.1 parts by weight, sufficient adhesive strength with the substrate cannot be obtained. If it exceeds the weight part, the solderability becomes poor. The preferred amount of glass frit used is 0.5 to 20 parts by weight.

The organic vehicle is a paste in which each powder is dispersed. The organic vehicle is composed of an organic binder and / or a solvent. Examples of the organic binder include ethyl cellulose, hydroxyethyl cellulose, methyl cellulose, nitrocellulose, ethyl cellulose derivative, acrylic resin, butyral resin, alkyd phenol resin, epoxy resin and wood rosin. Examples of acrylic resins include those containing polymethacrylic acid butyl ester, polymethacrylic acid isobutyl ester, and lower alcohol polymethacrylate. As the butyral resin, a polyvinyl butyral resin is preferable. The organic binder preferably has a decomposition temperature of 500 ° C. or lower. If a material having a high decomposition temperature is used, the decomposition of the organic binder due to firing becomes insufficient, which hinders the solder wettability and conductivity of the fired film, resulting in a decrease in adhesive strength with the substrate. A thermobalance was used to measure the decomposition temperature, and the weight of the resin was 5
The temperature at the time of 0% weight loss was measured.

The amount of the organic binder used is preferably 5 parts by weight or less, more preferably 1 part by weight or less, and most preferably 0.5 part by weight or less with respect to 100 parts by weight of the conductive metal mixed powder. . The use of 5 parts by weight or more of the organic binder results in insufficient decomposition of the organic binder due to firing, impairs solder wettability and conductivity of the fired film,
This leads to a decrease in the adhesive strength with the substrate. When used in the present invention, these resins are preferably dispersed in a solvent or the like, and a known solvent can be used. However, it is not always necessary to use a resin, and only a solvent may be used as the organic vehicle as long as appropriate viscosity and printability are obtained.

A known solvent may be used as the solvent, but a solvent which is less volatile during storage of the composition, gives an appropriate viscosity, and is excellent in printability is preferable. For example, terpineol or butyl carbitol, ethyl carbitol, methyl carbitol, ethyl cellosolve, butyl cellosolve, ethers such as phenoxypropanol, butyl carbitol acetate, ethyl carbitol acetate, methyl carbitol acetate, ethyl cellosolve acetate, butyl cellosolve acetate,
Ethyl acetate, butyl acetate, dibutyl phthalate, 2,
Esters such as 2,4-trimethyl 1,3-pentanediol diisobutyrate and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, N
-Methylpyridine, mineral spirits, hydrocarbons such as toluene, xylene, cymene, ethyldecylbenzene, dodecylbenzene and mixtures of these solvents.

The amount of the solvent used should be viscosity and printability.
It does not matter as long as it does not damage, for example, copper alloy powder 100
1 to 50 parts by weight is preferable, but more preferable.
It is preferably 2 to 20 parts by weight. Used in the present invention
Al₂O₃The fired ceramic substrate containing Al is Al ₂
O₃As a single component or as a component in the glass component
It includes. Al ₂O₃As for the content of ingredients,
The substrate has heat resistance suitable for the firing temperature of the
Keep good adhesion between the plate and the paste firing film,
In order to keep the solder wettability of the fired film good,
It is preferably 0% by weight or more. .

[0022]

EXAMPLES The properties of the composition of the present invention were measured in terms of resistivity, solder wettability and adhesive strength. The resistivity was determined by making a conductor of 0.5 mm × 35 mm and measuring the resistance value at both ends of the conductor using the 4-terminal test method.

The adhesive strength is measured on the substrate by 2 mm × 2 m.
A mild active flux is applied to a 20 μm thick film that has been baked to m, and it is immersed in a Pb / Sn / Ag eutectic solder bath at 230 ° C. for 5 seconds, and a Sn-plated copper wire with a diameter of 0.8 mm is soldered. The peel strength was measured using a Ron type tensile tester. The adhesive strength was measured immediately after firing and after standing at high temperature. When left at a high temperature, the fired film with the lead wire soldered is put in an oven at 150 ° C for 100 ° C in the air.
Went by keeping time.

The solder wettability was 20 mm × 20 mm.
After immersing in a Pb / Sn eutectic solder bath at 0 ° C. for 10 seconds, the wetted area by solder was measured. The solder wetting is preferably at least 90% or more, and therefore 90% or more was judged to be good, and less than 90% was judged to be bad.

[0025]

Examples 1 to 7 and Comparative Examples 1 to 4 As the conductive powder, those shown in Table 1 were used. Glass frit
Main component in _{PbO-ZnO-B 2 O 3} , average particle size 2.9
A material having a recrystallization temperature of 570 ° C. was used. The organic binder used was a solution of ethyl cellulose N-100 (manufactured by Hercules) dissolved in 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate so as to form an 8% solution.

The conductive powder and the glass frit were mixed in the proportions shown in Table 2, and then MnO ₂ and / or Cr ₂ were added.
O ₃ powder was added in the ratio shown in Table 2, and an organic vehicle was added so that the organic binder was 0.3 parts by weight with respect to 100 parts by weight of the copper alloy powder, and a solvent was further added if necessary. After that, each was sufficiently kneaded with a three-roll mill to prepare each paste.

The components of the ceramic fired substrate are Al ₂ O ₃ --ZnO ₂ --B ₂ O ₃ --SiO ₂ --CaO and Al ₂ O ₃ --ZnO ₂ --B ₂ O ₃ --SiO ₂ --Pb.
The one consisting of O was used. The content of Al ₂ O ₃ is 52
% By weight. The paste of each Example and Comparative Example,
Screen printing was performed on the surface of the ceramic fired substrate using a 300-mesh stainless screen.

The firing was carried out in a nitrogen atmosphere with a peak temperature of 650 ° C. for 10 minutes and a total firing time of 1 hour using a belt conveyor furnace manufactured by Watkins Johnson. During temperature increase 440
The zone up to ° C was doped with oxygen to 100 ppm. Table 2 shows the performance evaluation results of the baked thick film.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY The present invention provides a ceramic fired substrate containing Al ₂ O _3, which has remarkably excellent solder wettability and adhesive strength of a fired fired film, particularly adhesive strength after thermal aging and has low resistivity. It is possible to provide a conductor paste for use, which is very useful.

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Claims (1)

[Claims] 1. The general formula Ag _x Cu _1-x (provided that 0.0
01 ≦ x ≦ 0.4, atomic ratio), the silver concentration on the grain surface is higher than the average silver concentration, and the copper alloy powder 1 has a region near the grain surface where the silver concentration increases toward the surface.
0.1 to 30 parts by weight of glass frit, 0.2 to ₂ parts by weight of MnO ₂ powder and 0.3 to 3 parts by weight of Cr ₂ O ₃ powder, dispersed in an organic vehicle, relative to 00 parts by weight. A conductor paste for a ceramic fired substrate, containing Al ₂ O ₃ .