JP2020202154A - Powder composition for forming thick film conductor and paste for forming thick film conductor - Google Patents

Abstract

To provide a powder composition for forming a thick film conductor and a paste for forming a thick film conductor that can form a thick film conductor to be readily plated.SOLUTION: A powder composition for forming a thick film conductor contains conductive powder, copper-containing lead-free glass powder, and manganese oxide powder. The content of the lead-free glass powder is 1.5 pts.mass or more and 5 pts.mass or less with respect to the conductive powder 100 pts.mass, and the content of the manganese oxide powder is 0.5 pts.mass or more and 3.5 pts.mass or less with respect to the conductive powder 100 pts.mass.SELECTED DRAWING: Figure 1

Description

The present invention relates to a powder composition for forming a thick film conductor and a paste for forming a thick film conductor. More specifically, when manufacturing a chip resistor, a resistance network, a hybrid IC, or the like, a thick film conductor is formed on a ceramic substrate or the like. The present invention relates to a powder composition for forming a thick film conductor and a paste for forming a thick film conductor used for forming, particularly a lead-free powder composition for forming a thick film conductor and a paste for forming a thick film conductor.

When forming a thick film conductor using thick film technology, generally, a conductive powder having high conductivity is dispersed in an organic vehicle together with an oxide powder such as glass powder to obtain a thick film conductor forming paste. obtain. Then, this paste is applied onto a ceramic substrate such as an alumina substrate in a predetermined shape by a screen printing method or the like, and fired at 500 ° C. or higher and 900 ° C. or lower to form a thick film conductor. It has been.

As the conductive powder, powders having a high conductivity such as Au, Ag, Pd, and Pt that can be fired in an air atmosphere and having a number average particle diameter of 10 μm or less are used. Among these, inexpensive Ag powder and Pd powder are used. However, it is mainly used.

As the glass powder, lead borosilicate glass powder or lead aluminoborosilicate glass powder, which has easy control of the softening point and has high chemical durability, is used. However, in recent years, from the viewpoint of preventing environmental pollution, there is an increasing demand for lead-free conductor pastes, and therefore, as glass powder, a material alternative to these is required. And Patent Document 1 discloses a lead-free thick film conductor forming composition.

By the way, a thick film conductor formed by using such a thick film conductor forming composition is applied as an electrode of an electronic component such as a chip resistor, a resistance network, or a hybrid IC used in the electronic industry. For example, as shown in the schematic cross-sectional view of FIG. 1, the chip resistor 100 includes an alumina substrate 10, an internal electrode 20 composed of a top electrode 21 formed of a thick film conductor, a side electrode 22, and a back electrode 23, and oxidation. A resistance film 30 made of a ruthenium-based thick film resistor or the like and a protective film 40 of insulating glass covering the resistance film 30 are provided. In these positional relationships, a pair of upper surface electrodes 21 are arranged so as to face each other in a non-contact state at intervals, and a resistance film 30 is arranged so as to connect the intervals formed by the upper surface electrodes 21. Further, on the exposed electrode surface of the internal electrode 20, in order to improve solderability, an intermediate electrode 50 made of Ni plating or the like, Sn—Pb solder plating, or lead-free solder plating of a Sn-based alloy alternative thereto The external electrodes 60 made of the above and the like are further formed by electrolytic plating, respectively.

Japanese Unexamined Patent Publication No. 2012-043622

The composition for forming a thick film conductor contains glass powder in order to ensure the adhesion between the thick film conductor and a ceramic substrate such as an alumina substrate. However, if the content of the glass powder is large, there is a problem that the thick film conductor is difficult to be plated.

In view of such circumstances, it is an object of the present invention to provide a powder composition for forming a thick film conductor and a paste for forming a thick film conductor, which can form a thick film conductor which is easily plated.

In order to solve the above problems, the powder composition for forming a thick film conductor of the present invention contains a conductive powder, a lead-free glass powder containing copper, and a manganese oxide powder, and the content of the lead-free glass powder is high. , 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the content of the manganese oxide powder is 0.5 parts by mass or more and 3.5 parts by mass with respect to 100 parts by mass of the conductive powder. It is a powder composition for forming a thick film conductor having a mass of parts or less.

Copper contained in the lead-free glass powder may be contained in an amount of 0.05 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the conductive powder in terms of cupric oxide.

The manganese oxide powder may be Mn ₃ O ₄ powder.

The conductive powder may be at least one selected from silver powder, palladium powder and platinum powder.

The lead-free glass powder may have a glass transition temperature of 400 ° C. or higher and 600 ° C. or lower.

The lead-free glass powder may contain bismuth.

Further, in order to solve the above problems, the thick film conductor forming paste of the present invention is a thick film conductor forming paste containing the powder composition for forming a thick film conductor, a solvent, and a resin. ..

Further, in order to solve the above problems, the thick film conductor forming paste of the present invention contains conductive particles, lead-free glass particles containing copper, manganese oxide particles, a solvent, and a resin, and is lead-free. The content of the glass particles is 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive particles, and the content of the manganese oxide particles is 0.5 with respect to 100 parts by mass of the conductive particles. A paste for forming a thick film conductor having a mass of parts or more and 3.5 parts by mass or less.

With the powder composition for forming a thick film conductor and the paste for forming a thick film conductor of the present invention, a thick film conductor that can be easily plated can be obtained.

It is sectional drawing of the chip resistor. It is a figure which shows the SEM image of the thick film conductor by Example 1. FIG. It is a figure which shows the SEM image of the thick film conductor by the comparative example 1. FIG. It is sectional drawing of the cross section of the test body for measuring the resistance value of a resistor.

Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be appropriately modified without changing the gist of the present invention.

The composition for forming a thick film conductor of the present invention contains a conductive powder, a lead-free glass powder, and a manganese oxide powder. In such a composition, the content of the lead-free glass powder is 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the content of the manganese oxide powder is 100 parts by mass of the conductive powder. It is 0.5 parts by mass or more and 3.5 parts by mass or less with respect to parts by mass. With such a composition for forming a thick film conductor, as described below, it is possible to suppress the phenomenon of floating on the surface of the thick film conductor by melting the glass that is difficult to be plated by firing. , A thick film conductor excellent in plating can be obtained.

As a result of intensive research on the glass that emerges on the surface of the thick film conductor in order to improve the plating of the thick film conductor, the present inventors have added manganese oxide powder to the composition for forming the thick film conductor. Therefore, it was found that the glass floating on the surface of the thick film conductor obtained by firing can be suppressed. Furthermore, what is surprising is that the addition of manganese oxide forms a fine stepped striped pattern on the surface of the thick film conductor. Since a fine stepped pattern is deposited on the surface of the thick film conductor, it can be expected that the adhesion between the surface of the thick film conductor and the Ni plating film or the like is improved by the anchor effect. That is, the adhesion between the thick film conductor and the plating film becomes better due to the suppression of the floating of the glass and the anchor effect.

The present invention has been completed based on such findings. Hereinafter, the present invention will be described in detail in the order of (1) powder composition for forming a thick film conductor and (2) paste for forming a thick film conductor. Further, (3) a method for producing a thick film conductor using the thick film forming paste of the present invention and (4) a thick film conductor will be described in detail.

[(1) Powder composition for forming a thick film conductor]
In the present invention, a lead-free thick film conductor forming powder composition can be obtained, and such a composition can be composed of at least a conductive powder and an oxide powder. Here, lead-free means lead as an unavoidable impurity due to the case where lead is not contained and the raw material powder such as conductive powder or oxide powder containing lead or lead is mixed in the manufacturing process. Is included in the case where 100 mass ppm or less is contained.

(Conductive powder)
The conductive powder used in the present invention may be used for forming a normal thick film conductor, and examples thereof include precious metals such as Au, Ag, Pd, and Pt. These precious metal powders can be used alone or in combination of two or more. Among these, it is preferable to use Ag powder, Pd powder, or a mixed powder thereof from the viewpoint of low melting point and cost.

The number average particle size of the conductive powder is preferably 10 μm or less, and more preferably 0.1 μm or more and 5.0 μm or less from the viewpoint of deteriorating the coatability of the thick film conductor forming paste according to the present invention. .. If the number average particle size exceeds 10 μm, firing in the temperature raising process may be delayed, which is not preferable. For example, when a mixed powder of Ag powder and Pd powder is used, the Ag powder can be used from the viewpoint of deteriorating the coatability of the thick film conductor forming paste according to the present invention and from the viewpoint of homogeneous dispersion of Ag powder and Pd powder. It is preferable that the number average particle size is 0.1 μm or more and 3.0 μm or less, and the number average particle size of the Pd powder is 0.01 μm or more and 0.3 μm or less. Here, the number average particle size is the number average particle size obtained from a scanning micrograph (SEM image) of the powder. The shape of the conductive powder includes granules and flakes, and the shape to be used is appropriately selected according to the intended use.

(Copper-containing lead-free glass powder)
In the present invention, as lead-free glass powder containing copper, SiO ₂ −B ₂ O ₃ − alkaline earth oxide glass powder, Bi ₂ O ₃ − SiO ₂ −B ₂ O ₃ based glass powder and ZnO − Lead-free glass powder such as SiO _2- B ₂ O ₃ glass powder can be used. Considering the firing temperature for forming a thick film conductor, it is desirable that the glass transition point of these lead-free glass powders is 400 ° C. or higher and 600 ° C. or lower. The lead-free glass used may be crystallized glass or non-crystallized glass. The lead-free glass powder is a glass powder that does not contain lead or a glass powder that contains 100 mass ppm or less of lead as an unavoidable impurity. Here, the glass transition point is a temperature indicating the bending point of the thermal expansion curve when a rod-shaped sample obtained by remelting lead-free glass powder is measured in the atmosphere by a thermomechanical analysis method (TMA). Be measured.

As the lead-free glass powder containing copper, one kind of lead-free glass powder may be used, or a plurality of lead-free glass powders may be mixed and used. When a plurality of lead-free glass powders are mixed and used, at least one of these lead-free glass powders needs to contain copper. For example, when cupric oxide (CuO) is contained in the lead-free glass powder as a copper component, the effect of improving the adhesive strength of the thick film conductor can be obtained.

The amount of total copper contained in the lead-free glass powder is preferably 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the conductive powder in terms of CuO. If the amount of total copper contained in the lead-free glass powder is less than 0.05 parts by mass with respect to 100 parts by mass of the conductive powder in terms of CuO, improvement in the adhesive strength of the thick film conductor may not be expected.

On the other hand, if the amount of total copper is more than 0.5 parts by mass with respect to 100 parts by mass of the conductive powder in terms of CuO, it may affect the electrical characteristics of the resistance film formed on the surface of the thick film conductor. .. Further, the resistance film used together with the thick film conductor is used by applying a thick film resistance paste and firing it, and CuO is added to the formed resistance film as an additive for adjusting the electrical characteristics. There are times when Since there is a concern that CuO contained in the thick film conductor diffuses into the resistance film when the thick film resistor paste is fired and changes the electrical characteristics of the resistance film, copper is reduced to 0 as described above. It is not preferable to contain more than 5 parts by mass.

As described above, since the lead-free glass powder contains copper as in the powder composition for forming a thick film conductor according to the present invention, the effect of improving the adhesion strength can be expected even with the above-mentioned addition amount. Further, the lead-free glass powder containing copper improves the Ni plating property on the thick film conductor, and also has the effect of increasing the Ni plating film thickness.

Further, by including bismuth together with copper in the lead-free glass powder, the effect of improving the adhesive strength between the internal electrode formed by the thick film conductor and the ceramic substrate such as the alumina substrate can be obtained. For example, when the content of bismuth in the lead-free glass powder is 30% by mass or more and 70% by mass or less as Bi ₂ O ₃ , the effect of improving the adhesive strength can be obtained.

The content of lead-free glass powder in the powder composition for forming a thick film conductor is 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the adhesive strength with the substrate, the plating property, and the solder In consideration of the wettability and the like, it is more preferably 1.5 parts by mass or more and 3 parts by mass or less, and further preferably 1.5 parts by mass or more and 2.7 parts by mass or less. If the content of the lead-free glass powder is less than 1.5 parts by mass, the adhesive strength with the ceramic substrate may decrease. Further, if the content is more than 5 parts by mass, a phenomenon that the glass floats on the surface of the thick film conductor may occur, which may reduce the plating property of the thick film conductor, the wettability of the solder, and the like. is there.

As the composition of the glass in the lead-free glass powder, those having a composition capable of realizing the above-mentioned glass transition point and softening point can be used. The content of SiO ₂ in the lead-free glass powder is preferably 15% by mass or more and 60% by mass or less. If the content of SiO ₂ is less than 15% by mass, the chemical resistance of the glass may be lowered, and the weather resistance, water resistance and chemical resistance of the glass in the thick film conductor may be lowered, and as a result. When Ni plating or the like is applied to a thick film conductor, problems such as plating defects may occur. On the other hand, if the content of SiO ₂ is more than 60% by mass, the temperature at which the glass softens becomes too high, which may impair the adhesion between the thick film conductor and the ceramic substrate.

The shape of the lead-free glass powder includes various shapes such as spherical and needle-shaped, and is not particularly limited, but the cumulative volume particle size measured by a particle size distribution meter using laser diffraction of the lead-free glass powder. The D ₅₀ diameter (median diameter) of the distribution is preferably 10 μm or less, and is 0.5 μm or more from the viewpoint of the coatability of the thick film conductor forming paste according to the present invention and the uniform dispersion of the conductive powder and the lead-free glass powder. It is more preferably 3 μm or less. When the diameter of D ₅₀ is 10 μm or more, the uniform dispersion of the conductive powder and the lead-free glass powder is hindered, the lead-free glass powder is biased, and the adhesive strength between the thick film conductor and the substrate tends to decrease, which is not preferable.

(Manganese oxide powder)
The content of the manganese oxide powder is 0.5 parts by mass or more and 3.5 parts by mass or less with respect to 100 parts by mass of the conductive powder. If the content is less than 0.5 parts by mass, the effect of suppressing the embossment of the glass on the surface of the thick film conductor may not be expected, and the plating property may not be improved. On the other hand, if the content is 3.5 parts by mass, the effect of improving the plating property can be sufficiently obtained, and even if the content is higher than this, the effect of improving the plating property is not improved.

The plating property of thick film conductors will be considered. If the glass floats on the surface of the thick film conductor, the plating property such as Ni plating on the surface of the thick film conductor deteriorates. Ni plating and Sn alloy plating are not easily attached to the surface of the thick film conductor, and if there are holes such as pinholes on these plated surfaces, the Ag of the thick film conductor is sulfided by the sulfur component in the atmosphere. It may lead to poor connection of electronic parts.

By the way, when examining the meltability of lead-free glass and glass containing lead as a constituent component, not inevitably, in the process of raising the temperature, lead-free glass is better at the same softening point. The melting temperature is on the high temperature side. In the firing process for obtaining a thick-film conductor, the glass is bound to a ceramic substrate such as an alumina substrate in a limited time during which the glass is melted while the temperature is rising and the peak temperature is maintained for a certain period of time. , Ensuring the adhesion of thick film conductors. Since lead-free glass is difficult to melt, it is necessary to increase the content of lead-free glass powder in the powder composition for forming a thick film conductor using lead-free glass in order to adhere to the substrate. However, if the content of the lead-free glass powder exceeds 1.5 parts by mass with respect to 100 parts by mass of the conductive powder, the lead-free glass may be raised on the surface of the thick film conductor. Even if the content of the lead-free glass powder exceeds 1.5 parts by mass with respect to 100 parts by mass of the conductive powder, if the content of the lead-free glass powder is close to 1.5 parts by mass, the lead-free glass is embossed. Locally, as the content of lead-free glass increases, the area where the glass emerges on the surface of the thick-film conductor increases. Therefore, by setting the content of manganese oxide powder to 100 parts by mass of the conductive powder to 0.5 parts by mass or more and 3.5 parts by mass or less, the plating property of the thick film conductor is improved, and the plated thick film conductor is provided. As a result, poor connection of electronic components can be improved by preventing the sulphurization of Ag.

When a thick film conductor is formed using a powder composition for forming a thick film conductor using lead-free glass, if the content of manganese oxide with respect to 100 parts by mass of the conductive powder is less than 0.5 parts by mass, the ceramic substrate Adhesion with and is improved, but the plating property may not be improved. On the other hand, if the content of manganese oxide with respect to 100 parts by mass of the conductive powder exceeds 3.5 parts by mass, the adhesion of the ceramic substrate may decrease. Then, in order to more effectively prevent the sulfide of Ag of the plated thick-film conductor, the content of manganese oxide with respect to 100 parts by mass of the conductive powder is preferably 0.5 parts by mass to 3 parts by mass. More preferably, 5 parts by mass to 2.5 parts by mass.

The number average particle size of the manganese oxide powder is preferably 0.8 μm or less, and is 0.2 μm or more and 0.8 μm or less from the viewpoint of suppressing the phenomenon that the glass floats on the surface of the thick film conductor. More preferred. If the number average particle size is larger than 0.8 μm, uniform dispersion with the conductive powder or lead-free glass powder may not be possible, and the manganese oxide powder may be unevenly distributed. Further, although it is possible to use a powder having a number average particle diameter of less than 0.2 μm, in general, a powder having a diameter of 0.2 μm or more can be easily obtained. Here, the number average particle size is the number average particle size obtained from a scanning micrograph (SEM image) of the powder.

Further, as manganese oxide, MnO ₂ (manganese dioxide), Mn ₃ O ₄ (trimanganese tetraoxide) and the like can be used. For example, by using Mn ₃ O ₄ (trimanganese tetraoxide), a thick film conductor can be used. A fine stepped striped pattern is formed on the surface of the manganese, and the anchor effect can be exhibited.

(Oxide powder)
In addition to the lead-free glass powder and manganese oxide powder described above, the powder composition for forming a thick film conductor can contain oxide powders other than these as long as the effects of the present invention are not impaired. For example, for the purpose of improving the adhesive strength, acid resistance, solder wettability, etc. of thick film conductors, at least one kind of oxide powder such as Bi ₂ O ₃ , SiO ₂ , ZnO, TiO ₂ , ZrO ₂ , MnO ₂ or more is used. Can be added. However, from the viewpoint of suppressing the increase in resistance value, the content of the oxide powder other than the lead-free glass powder and the manganese oxide powder is in the range of about 0 to 10 parts by mass in total with respect to 100 parts by mass of the conductive powder. It is preferable to keep it.

The powder composition for forming a thick film conductor of the present invention is preferably a mixture of a conductive powder, a lead-free glass powder, and a manganese oxide powder. By being a mixture, it is possible to obtain a thick film conductor forming paste or a thick film conductor having a more uniform content. As a mixing method, known techniques such as a ball mill and a bead mill can be used, and a sufficiently uniform mixture can be obtained by these techniques.

[(2) Paste for forming thick film conductor]
An example of the thick film conductor forming paste of the present invention is a paste containing the above-mentioned thick film conductor forming powder composition, a solvent, and a mixture of a resin.

As the solvent, tarpineol or butyl carbitol which are generally used for pastes can be used, and as the resin, ethyl cellulose or methacrylate which is generally used for pastes can be used. The resin and the solvent can be mixed in advance to form an organic vehicle, which can be used to produce a thick film conductor forming paste. For example, from the viewpoint of cost and ease of handling, an organic vehicle in which ethyl cellulose is dissolved in tarpineol can be used. In the organic vehicle, the ratio of the resin and the solvent is appropriately selected depending on the printability and the coating method in the final thick film conductor forming paste composition.

The content of the thick film conductor forming paste as an organic vehicle can be 15 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the conductive powder. If the content of the organic vehicle is less than 15 parts by mass, the viscosity may be too high to be applied substantially, and if the content exceeds 250 parts by mass, the particles settle or the thickness after firing. There is a risk that the film density of the film conductor will be significantly reduced. Considering printability, ease of coating, sedimentation of particles as a paste, and denseness of the film of a thick-film conductor, the content is preferably 20 parts by mass or more and 100 parts by mass or less.

The thick film conductor forming paste of the present invention can be produced by kneading a thick film conductor forming powder composition and an organic vehicle. The kneading method is not particularly limited, but kneading can be performed using a known technique such as a wet kneading mill, a roll mill, or a taper roll mill. The viscosity of the obtained conductor paste is appropriately selected depending on the film thickness of the target thick-film conductor, the type of ceramic substrate, and the like.

Further, examples other than the above-mentioned thick film conductor forming paste of the present invention include conductive particles, lead-free glass particles, manganese oxide particles, a solvent, and a resin, and the content of the glass particles is the above. 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of conductive particles, and the content of the manganese oxide particles is 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the conductive particles. A certain thick film conductor forming paste can be mentioned.

Regarding the content of conductive particles, lead-free glass particles, manganese oxide particles, lead-free glass particles, and the content of manganese oxide particles, the conductive powder and lead-free glass described in the above section of the powder composition for forming a thick film conductor. The contents are the same as those of the powder, the manganese oxide powder, the lead-free glass powder, and the manganese oxide powder, and the description thereof is omitted here. Further, the solvent and the resin are also described in the above-mentioned example of the thick film conductor forming paste, and thus the description thereof will be omitted.

The thick film conductor forming paste of the present invention can be produced, for example, by adding conductive particles, lead-free glass particles, and manganese oxide particles to an organic vehicle to form a mixture, and kneading the mixture. The kneading method is not particularly limited, but kneading can be performed using a known technique such as a wet kneading mill, a roll mill, or a taper roll mill. The viscosity of the obtained conductor paste is appropriately selected depending on the film thickness of the target thick-film conductor, the type of ceramic substrate, and the like.

In addition to the lead-free glass powder and manganese oxide powder described above, the thick film conductor forming paste described above can contain oxide powders other than these as long as the effects of the present invention are not impaired. is there. For example, for the purpose of improving the adhesive strength, acid resistance, solder wettability, etc. of thick film conductors, at least one kind of oxide powder such as Bi ₂ O ₃ , SiO ₂ , ZnO, TiO ₂ , ZrO ₂ , MnO ₂ or more is used. Can be added. However, from the viewpoint of suppressing the increase in resistance value, the content of the oxide powder other than the lead-free glass powder and the manganese oxide powder is in the range of about 0 to 10 parts by mass in total with respect to 100 parts by mass of the conductive powder. It is preferable to keep it.

[(3) Manufacturing method of thick film conductor]
The method for producing a thick film conductor is, for example, a coating step of applying the thick film conductor forming paste of the present invention to a ceramic substrate, a drying step of drying the substrate to which the paste is applied, and then a temperature of 500 ° C. or higher and lower than 900 ° C. A firing step of firing at temperature can be included.

(Applying process)
The coating method is not particularly limited, and known techniques such as screen printing, printing methods such as letterpress printing and gravure printing, and drawing methods using a dispenser can be used, but an appropriate film thickness can be used. It is preferable to apply by screen printing from the viewpoint of mass production. As the ceramic substrate, a 96% alumina substrate, forsterite, or the like is used depending on the use of the electronic component, and the thick film conductor forming paste of the present invention can be applied to any substrate.

(Drying process)
After applying the thick film conductor forming paste, it is preferable to dry the coated film together with the ceramic substrate under a temperature condition of 80 ° C. or higher and 200 ° C. or lower for a time of 2 minutes or more and 15 minutes or less. By providing the drying step between the coating step and the firing step in this way, it is possible to prevent volatilization and combustion of the solvent and the like due to the remaining volatile components such as the solvent even during the firing, so that the firing step When a firing furnace is used, the effect of preventing contamination of the firing furnace can be obtained. In this step, the drying method is not particularly limited, and a known means such as an oven or a belt-type drying oven can be used, but from the viewpoint of mass productivity, drying is preferably performed in a belt-type drying oven. Further, if the drying temperature is less than 80 ° C., the time required for drying becomes long and the productivity deteriorates, which may not be preferable. Further, if the drying temperature exceeds 200 ° C., the resin may be oxidized and the dried film may become brittle, which is not preferable.

(Baking process)
In the firing step after the drying step, the film after drying is heated together with the ceramic substrate to fire the film. It is preferable to use a belt furnace as the firing method. In this case, the peak temperature in firing is 500 ° C. or higher and lower than 900 ° C., preferably 700 ° C. or higher and lower than 900 ° C. If the peak temperature is less than 500 ° C., the lead-free glass powder is not sufficiently melted, which may cause a problem of impairing the adhesion to the ceramic substrate. On the other hand, when the peak temperature is 900 ° C. or higher, the film may be oversaturated. Especially when a thick film conductor forming paste containing Ag having a low melting point as a main component is used, conductive particles and glass particles Etc. are separated and the thick film conductor is formed in an island shape, which may cause a problem that a uniform electrode film cannot be formed.

It is necessary to maintain the above peak temperature for 5 minutes or more and 20 minutes or less, preferably 7 minutes or more and 13 minutes or less. If the holding time of the peak temperature exceeds 20 minutes, the thick conductor film may be oversintered, and if the holding time is less than 5 minutes, the sintering may be insufficient. Further, the total time of the firing process of raising the temperature to the peak temperature, maintaining the peak temperature, and cooling from the peak temperature needs to be 20 minutes or more and 90 minutes or less, preferably 30 minutes or more and 60 minutes or less. .. If the total time is less than 20 minutes, the heating rate and cooling rate become too high, and there is a risk that the thick film conductor will crack due to a sudden temperature change. Further, if the total time exceeds 90 minutes, there may be a problem that productivity deteriorates.

In order to bake at the above peak temperature and firing time, the rate of temperature rise to the peak temperature is 20 ° C./min or more and 150 ° C./min or less, and the cooling rate from the peak temperature is 20 ° C./min or more and 200 ° C./min. The following is preferable. If the temperature rising rate is less than 20 ° C./min or the cooling rate is less than 20 ° C./min, productivity may deteriorate, which is not preferable. Further, when the temperature rising rate exceeds 150 ° C./min or the cooling rate exceeds 200 ° C./min, cracks may occur in the thick film conductor due to a sudden temperature change, which is not preferable.

The atmosphere during firing is not particularly limited, but it is preferable to fire in an air atmosphere from the viewpoint of softening the lead-free glass.

[(4) Thick film conductor]
The thick film conductor obtained from the thick film conductor forming paste of the present invention by the above production method contains a conductive component, a glass component obtained by melting a lead-free glass powder, and manganese oxide. Manganese oxide means a state in which it is dissolved in glass.

Since the thick film conductor contains manganese oxide, there is little glass embossment on the surface, and fine stepped striped patterns are generated on the surface.

The desirable film thickness of the thick film conductor is 5.0 μm or more and 10.0 μm or less. Within this film thickness range, it is possible to suppress the floating of the glass on the surface of the thick film conductor while satisfying the adhesion of the thick film conductor to the ceramic substrate.

Therefore, the thick film conductor produced by using the thick film conductor forming paste of the present invention has excellent adhesive strength to the ceramic substrate and has extremely excellent characteristics of satisfying good plating adhesion. It has become. Good plating adhesion can be evaluated as the film thickness of Ni electroplating. When Ni electroplating is applied at the same current density, thick film conductors with glass embossing even locally on the surface are plated more than thick film conductors with manganese oxide added to suppress the embossing of the glass on the surface. It has been confirmed that the film thickness becomes thinner.

Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited by these Examples.

In Examples 1 to 3, Comparative Examples 1 and 2, and Reference Examples 1 and 2, using either the conductive powder and the manganese oxide powder shown below and the spherical lead-free glass powders 1 and 2 shown in Table 1 were used. A powder composition for forming a thick film conductor and a paste for forming a thick film conductor were prepared, and a thick film conductor was further produced. For the obtained thick film conductor, the firing film thickness was measured, the surface condition was observed, the resistance value was measured, and the adhesive strength with the substrate was evaluated. The total amount of alkali metal oxides in Table 1 is mainly the total amount of metal oxides of Li, K and Na.

(Conductive powder)
As the conductive powder, silver powder (number average particle diameter of 2.0 μm) was used.

(Manganese oxide powder)
Mn ₃ O ₄ (number average particle size 0.5 μm) was used as the manganese oxide powder.

[Preparation of powder composition for forming thick film conductors]
A powder composition for forming a thick film conductor was prepared by mixing a conductive powder, a lead-free glass powder, and a manganese oxide powder so as to have the compositions shown in Table 2 and stirring with a ball mill.

[Preparation of thick film conductor forming paste]
A paste for forming a thick film conductor was prepared by mixing 72.5% by mass of the powder composition for forming a thick film conductor prepared above and 27.5% by mass of an organic vehicle and then kneading with a three-roll mill. The organic vehicle was prepared by mixing 7% by mass of ethyl cellulose with 93% by mass of a tarpineol solution as a solvent and heating to dissolve the ethyl cellulose.

[Manufacturing of thick film conductors]
The thick film conductor forming paste prepared above is screen-printed on a 96% alumina substrate (25.4 mm × 25.4 mm × 1 mm) by a screen printing machine (coating step), and a belt-type drying furnace is used. It was dried at 150 ° C. for 5 minutes (drying step). The dried film and alumina substrate were fired in a belt furnace at a peak temperature of 850 ° C. for 9 minutes for a total of 30 minutes (firing step) to form a thick film conductor having a predetermined pattern.

[Evaluation of physical properties of thick film conductors]
With respect to the thick film conductor manufactured above, the fired film thickness was measured, the plating film thickness was observed, the surface condition was observed, the resistance value was measured, and the adhesive strength with the alumina substrate was evaluated by the methods shown below. The evaluation results are shown in Table 2.

(Measurement of firing film thickness)
The film thickness of the thick-film conductor after firing was measured using a contact-type surface roughness meter.

(Plating film thickness)
The thickness of the Ni electroplated surface from the alumina substrate of the sample in which the thick film conductor after firing was electroplated was measured with a contact type surface roughness meter, and the film thickness of the thick film conductor was subtracted from the obtained result. The plating film thickness was calculated.

(Observation of surface condition)
The surface condition of the thick film conductor was observed using an SEM (scanning electron microscope), and the presence or absence of a stepped striped pattern and the presence or absence of the raised glass were confirmed. Further, FIG. 2 shows an SEM image of the thick film conductor according to Example 1, and FIG. 3 shows an SEM image of the thick film conductor according to Comparative Example 1.

(Measurement of resistance value)
The resistance value of a sample of a thick film conductor formed in a pattern having a width of 0.5 mm and a length of 50 mm on an alumina substrate was measured with a digital multimeter.

(Evaluation of adhesive strength)
Nickel sulfate is 280 g / L, nickel chloride is 60 g / L, and boric acid is 40 g / L as a Ni plating solution on a thick film conductor created in a pad-like pattern of 2.0 mm × 2.0 mm on an alumina substrate. Using a plating solution prepared to be L, the current density was set to 5 × 10 ^-3 A / mm ² (5 × 10 ^-9 A / m ² ), and Ni electroplating was performed for 2 minutes to prepare a sample. .. A Sn-plated copper wire having a diameter of 0.65 mm was soldered to this plated sample using lead-free solder having a Cu composition of 96.5% by mass Sn-3% by mass Ag-0.5% by mass. The one was used as a test piece. The initial strength of the adhesive strength is determined by pulling the Sn-plated copper wire of the test piece in the direction perpendicular to the alumina substrate with a tensile tester, peeling the thick conductor film from the alumina substrate, and measuring the tensile force at the time of this peeling. , Maximum value, minimum value and average value were calculated and evaluated. Further, the heat-deteriorated adhesive strength is deteriorated by applying a heat load of 150 ° C. for 24 hours to the same test piece as described above, and then a tensile test is performed in the same manner to obtain the maximum value, the minimum value and the average value. Calculated and evaluated. Fifteen test pieces were evaluated for both the initial adhesive strength and the thermal deterioration adhesive strength.

(8 μm conversion resistance value)
From the measurement result of the fired film thickness and the resistance value measurement result, the resistance value when the fired film thickness was converted to 8 μm was calculated.

(About the film thickness and resistance of thick-film conductors)
The film thickness of the thick film conductor was in the range of 5.0 μm or more and 10.0 μm or less in all of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 and 2, and an abnormality was observed in the film thickness. I couldn't. In addition, there was no abnormality in the resistance value, and there was no problem in any of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 and 2.

(Evaluation of adhesive strength)
There was no problem in the adhesive strengths of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 and 2 in both the initial evaluation and the evaluation after thermal deterioration. When a predetermined amount of lead-free glass powder containing bismuth was used as in Example 1, the effect of increasing the adhesive strength was observed both in the initial stage and after thermal deterioration.

Further, from the results of Examples 1 to 3 and Comparative Example 1, the effect of increasing the adhesive strength by containing manganese was observed both in the initial stage and after thermal deterioration. This effect has a great effect on the adhesive strength after thermal deterioration.

(Observation result of surface condition)
In Examples 1 to 3, Reference Examples 1 and 2, and Comparative Example 2, a stepped striped pattern due to the inclusion of manganese was observed, and the surface condition was such that improvement in plating adhesion due to the anchor effect could be expected. In Comparative Example 1, manganese was not contained and no striped pattern was observed.

Regarding the presence or absence of the floating of the glass, in Examples 1 to 3 and Reference Examples 1 and 2, no floating of the glass was observed due to the inclusion of manganese, and the Ni plating film thickness was larger than that of Comparative Example 1. From this, it was found that the Ni plating property was improved, so that the sulfide of silver could be suppressed. Further, in Comparative Example 1, floating of the glass was observed because it did not contain manganese, and it was suggested that the thin film thickness of the glass even if Ni plating or the like was applied may cause a sulfurization phenomenon of silver. The result was

Further, according to the results of Examples 1 to 3 and Comparative Example 2, it was observed that the Ni plating film thickness tended to increase as the copper content increased. Further, as compared with the Ni plating film thickness of Comparative Example 1, Examples 1 to 3 and Comparative Example 2 containing manganese oxide have a thicker Ni plating film thickness than Comparative Example 1 containing no manganese oxide. Understand. From this result, it was also clarified that the thick film conductor obtained from the powder composition for forming a thick film conductor to which manganese oxide was added was excellent in its Ni plating adhesion.

[Evaluation of resistance value of resistor]
Next, the effect of the thick film conductor on the electrical characteristics of the resistance film was evaluated. The thick film conductor forming paste according to Examples 1 to 3, Reference Examples 1 and 2 and Comparative Examples 1 and 2 is opposed to the alumina substrate 11 so that the pair of thick film conductors 25 face each other with an interval S of 1 mm. It was printed, dried at 150 ° C. for 5 minutes, and then fired in a belt furnace at a peak temperature of 850 ° C. for 9 minutes for a total of 30 minutes to form a thick film conductor 25 for evaluating a resistance film on an alumina substrate 11. ..

Then, a thick film resistor paste is printed between the pair of thick film conductors 25 so that the thickness after firing is 7 μm, dried at 150 ° C. for 5 minutes, and then dried at a peak temperature of 850 ° C. for 9 minutes. The resistance film 31 was obtained by firing in a belt furnace for a total of 30 minutes. The resistor film 31 is formed so as to connect a pair of thick film conductors 25 to form a resistor 101 (FIG. 4). Since the distance S between the thick film conductors 25 of the obtained resistance film 31 is 1 mm, the effective length that functions as a resistor is 1 mm, and the width of the resistance film 31 is set to 1 mm. In addition, 25 resistors 101 were formed for each of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 and 2 to form a test body, and the resistance value of the test body was measured with a digital multimeter. The average value of the resistance values of the 25 test pieces is shown in Table 2 as the resistance value of the resistor.

The thick film resistance paste for forming the resistance film 31 is prepared by mixing RuO ₂ powder as a conductive material and Si-B-Ba-Zn-based glass powder in a mass ratio of 15:85. This paste contains 40% by mass of an organic vehicle in which ethyl cellulose is dissolved in tarpineol so that the resulting inorganic component has a mass ratio of 60% by mass and ethyl cellulose and turpineol have a mass ratio of 15:85. This paste was produced by kneading an inorganic component and an organic vehicle with a three-roll mill.

The resistors using the thick film conductors of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Example 1 showed a resistance value of about 100 kΩ, and there was no problem with the resistance value. On the other hand, the resistor using the thick film conductor of Comparative Example 2 showed a resistance value of 85 kΩ. From this result, it was presumed that the thick film conductor containing an excess of CuO deteriorated the electrical characteristics of the resistor.

[Summary]
As is clear from the examples, the powder composition for forming a thick film conductor and the paste for forming a thick film conductor of the present invention have excellent adhesive strength with a substrate while maintaining electrical characteristics such as resistance value, and plating. It is clear that it is possible to provide a thick film conductor that is easy to attach to and can suppress the sulfide of silver.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

10, 11 Alumina substrate 20 Internal electrode 21 Top electrode 22 Side electrode 23 Back electrode 25 Thick film conductor 30, 31 Resistor film 40 Protective film 50 Intermediate electrode 60 External electrode 100 Chip resistor 101 Resistor S interval

Claims (8)

With conductive powder
Lead-free glass powder containing copper and
Contains manganese oxide powder,
The content of the lead-free glass powder is 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive powder.
A powder composition for forming a thick film conductor, wherein the content of the manganese oxide powder is 0.5 parts by mass or more and 3.5 parts by mass or less with respect to 100 parts by mass of the conductive powder. The thick film conductor formation according to claim 1, wherein the copper contained in the lead-free glass powder is contained in an amount of 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the conductive powder in terms of cupric oxide. For powder composition. The powder composition for forming a thick film conductor according to claim 1 or 2, wherein the manganese oxide powder is Mn ₃ O ₄ powder. The powder composition for forming a thick film conductor according to any one of claims 1 to 3, wherein the conductive powder is at least one selected from silver powder, palladium powder and platinum powder. The powder composition for forming a thick film conductor according to any one of claims 1 to 4, wherein the lead-free glass powder has a glass transition temperature of 400 ° C. or higher and 600 ° C. or lower. The powder composition for forming a thick film conductor according to any one of claims 1 to 5, wherein the lead-free glass powder contains bismuth. A paste for forming a thick film conductor, which comprises the powder composition for forming a thick film conductor according to any one of claims 1 to 6, a mixture of a solvent and a resin. With conductive particles
Lead-free glass particles containing copper and
Manganese oxide particles and
With solvent
Contains resin,
The content of the lead-free glass particles is 1.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the conductive particles.
A paste for forming a thick film conductor, wherein the content of the manganese oxide particles is 0.5 parts by mass or more and 3.5 parts by mass or less with respect to 100 parts by mass of the conductive particles.