KR102639865B1 - Powder composition for forming thick film conductor and paste for forming thick film conductor - Google Patents

Abstract

(Problem) 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 to which plating is easy to adhere.
(Solution) A conductive powder, lead-free glass powder, and manganese oxide powder are included, and the content of the 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 manganese oxide A powder composition for forming a thick film conductor, wherein the powder content 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.

Description

Powder composition for forming thick film conductors and paste for forming thick film conductors {POWDER COMPOSITION FOR FORMING THICK FILM CONDUCTOR AND PASTE FOR FORMING THICK FILM CONDUCTOR}

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, it is used to form a thick film conductor on a ceramic substrate, etc. when manufacturing chip resistors, resistance networks, hybrid ICs, etc. It relates to a powder composition for forming a thick film conductor and a paste for forming a thick film conductor, and particularly to a powder composition for forming a lead-free thick film conductor and a paste for forming a thick film conductor.

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

As the conductive powder, powders with a number average particle size of 10 μm or less, such as Au, Ag, Pd, and Pt, which have high electrical conductivity and can be fired in an air atmosphere, are used. Among these, inexpensive Ag powder and Pd powder are mainly used.

As the glass powder, lead borosilicate-based glass powder or alumino-borosilicate-based glass powder, which has an easy softening point control and high chemical durability, is used. However, in recent years, from the viewpoint of preventing environmental pollution, the demand for conductor pastes that do not contain lead is increasing, and therefore, materials to replace these as glass powder are required. And Patent Document 1 discloses a composition for forming a lead-free thick film conductor.

However, thick film conductors formed using such compositions for forming thick film conductors are applied as electrodes of electronic components such as chip resistors, resistance networks, and hybrid ICs used in the electronics industry. For example, as shown in the cross-sectional schematic diagram of FIG. 1, the chip resistor 100 includes an alumina substrate 10, a top electrode 21 formed by a thick film conductor, a side electrode 22, and a back electrode 23. It is provided with an internal electrode 20 made of, a resistance film 30 made of a ruthenium oxide-based thick film, etc., and a protective film 40 of insulating glass that covers the resistance. In addition, in order to improve solderability, the exposed electrode surface of the internal electrode 20 is coated with an intermediate electrode 50 made of Ni plating or the like, and Sn-Pb solder plating or lead-free solder plating of a Sn-based alloy to replace this. External electrodes 60 made of etc. are each additionally formed by electrolytic plating.

Japanese Patent Publication No. 2012-043622

The composition for forming a thick film conductor contains glass powder to ensure adhesion between the thick film conductor and a ceramic substrate such as an alumina substrate. However, if the content of glass powder is high, there is a problem in that plating does not adhere well to the thick film conductor.

In view of these circumstances, the purpose of the present invention is 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 which plating is easy to adhere.

In order to solve the above problems, the powder composition for forming a thick film conductor of the present invention includes conductive powder, lead-free glass powder, and manganese oxide powder, and the content of the glass powder is set to 100 parts by mass of the conductive powder. , 1.5 parts by mass or more and 5 parts by mass or less, and 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 manganese oxide powder may be Mn ₃ O ₄ powder.

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

The glass powder may have a glass transition temperature of 400°C or more and 600°C or less, and a softening point of 500°C or more and 700°C or less.

The glass powder may contain bismuth.

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

In addition, in order to solve the above problems, the paste for forming a thick film conductor of the present invention contains conductive particles, lead-free glass particles, manganese oxide particles, a solvent, and a resin, and the content of the glass particles is the above-mentioned. 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 per 100 parts by mass of the conductive particles. .

Using 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 to which plating is easy to adhere can be obtained.

1 is a cross-sectional schematic diagram of a chip resistor.
Figure 2 is a diagram showing an SEM image of a thick film conductor according to Example 1.
Figure 3 is a diagram showing an SEM image of the thick film conductor according to Comparative Example 1.

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

The composition for forming a thick film conductor of the present invention contains conductive powder, lead-free glass powder, and 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, with respect to 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. As described below, such a composition for forming a thick film conductor can suppress the phenomenon of floating on the surface of the thick film conductor by melting the glass to which plating does not adhere well by firing, thereby forming a thick film with excellent plating adhesion. You can get a conductor.

In order to improve the plating adhesion of a thick film conductor, the present inventors conducted extensive research on glass floating on the surface of a thick film conductor, and as a result, by adding manganese oxide powder to the composition for forming a thick film conductor, the thick film conductor obtained by firing was found to have We discovered something that can suppress glass floating on the surface. Additionally, what is surprising is that by adding manganese oxide, fine step stripes are formed on the surface of the thick film conductor. Since a fine step 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, etc. will be improved due to the anchor effect. In other words, the adhesion between the thick film conductor and the plating film becomes better due to suppression of floating of the glass and the anchor effect.

The present invention was completed based on such knowledge. Hereinafter, the present invention will be described in detail in the following order: (1) a powder composition for forming a thick film conductor and (2) a paste for forming a thick film conductor. In addition, (3) the method for producing a thick film conductor using the paste for forming a thick film of the present invention and (4) the thick film conductor are each explained in detail.

[(1) Powder composition for forming thick film conductors]

In the present invention, it is possible to make a lead-free powder composition for forming a thick film conductor, and such a composition may be composed of at least a conductive powder and an oxide powder. Here, lead-free means that it does not contain lead, for example, in the case where lead is mixed in raw material powder such as conductive powder or oxide powder containing lead, or in the manufacturing process, lead is added as an unavoidable impurity. This means that it is allowed to include cases where it contains less than 100 ppm by mass.

(Challenge powder)

The electrically conductive powder used in the present invention may be any material used for forming ordinary thick film conductors, and examples thereof include noble metals such as Au, Ag, Pd, and Pt. Powders of these noble metals can be used singly or in combinations of two or more types. 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 diameter of the electrically 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 deterioration in the applicability of the paste for forming a thick film conductor according to the present invention. If the number average particle diameter exceeds 10 μm, sintering during the temperature increase process may be delayed, which is not preferable. For example, when using a mixed powder of Ag powder and Pd powder, from the viewpoint of deterioration of the applicability of the paste for forming a thick film conductor according to the present invention and from the viewpoint of homogeneous dispersion of the Ag powder and Pd powder, the Ag powder It is desirable to set the number average particle diameter to 0.1 ㎛ or more and 3.0 ㎛ or less, and to set the number average particle diameter of the Pd powder to 0.01 ㎛ to 0.3 ㎛. Here, the number average particle size is the number average particle size determined from a scanning micrograph (SEM image) of the powder. In addition, the shape of the conductive powder includes granular shape, flake shape, etc., but the shape to be used is appropriately selected depending on the intended use.

(lead-free glass powder)

In the present invention, the lead-free glass powder is SiO ₂ -B ₂ O ₃ -alkaline earth oxide-based glass powder, Bi ₂ O ₃ -SiO ₂ -B ₂ O ₃ -based glass powder, or ZnO-SiO ₂ -B ₂ O Glass powder such as ₃ -based glass powder can be used. Considering the firing temperature for forming a thick film conductor, the glass transition point of these glass powders is preferably between 400°C and 600°C, and the softening point is preferably between 500°C and 700°C. The lead-free glass to be used may be crystallized glass or glass that does not crystallize. In addition, lead-free glass powder is glass powder that does not contain lead, or glass powder that contains 100 mass ppm or less of lead as an inevitable impurity. Here, the glass transition point is measured by measuring a rod-shaped sample obtained by remelting glass powder in the air using thermomechanical analysis (TMA), and measuring it as the temperature that represents the inflection point of the thermal expansion curve. In addition, the softening point is measured on glass powder in air using differential thermal analysis (TG-DTA), and is the peak temperature at which the next differential heat curve on the high temperature side decreases compared to the temperature at which the decrease in the differential heat curve on the lowest temperature side occurs. am.

By containing bismuth as the lead-free glass powder, the effect of improving the adhesive strength between an internal electrode formed by a thick film conductor and a ceramic substrate such as an alumina substrate is obtained. For example, the effect of improving adhesive strength can be obtained by setting the bismuth content in the lead-free glass powder to 30% by mass or more and 70% by mass or less as Bi ₂ O ₃ .

The content of lead-free glass powder in the powder composition for forming a thick film conductor is set to be 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, plating properties, solder wettability, etc. Considering, it is more preferable to set it to 1.5 parts by mass or more and 3 parts by mass or less, and even more preferably to set it to 1.5 parts by mass or more and 2.7 parts by mass or less. If the content of lead-free glass powder is less than 1.5 parts by mass, there is a risk that the adhesive strength with the ceramic substrate may decrease. Additionally, if this content is greater than 5 parts by mass, a phenomenon in which glass may float on the surface of the thick film conductor may occur, which may result in deterioration of plating properties, solder wettability, etc. for the thick film conductor.

The glass composition in the lead-free glass powder can be one that can achieve the glass transition point and softening point described above. In the glass powder, the SiO ₂ content is preferably 15 mass% or more and 60 mass% or less. If the SiO ₂ content is less than 15% by mass, there is a risk that the chemical resistance of the glass may decrease, or the weather resistance, water resistance, and chemical resistance of the glass in the thick film conductor may decrease, and as a result, Ni plating, etc., may be applied to the thick film conductor. There is a risk that problems such as plating defects may occur during implementation. On the other hand, if the SiO ₂ content exceeds 60% by mass, the softening temperature of the glass becomes too high, and the adhesion between the thick film conductor and the ceramic substrate may be impaired.

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

(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 this content is less than 0.5 parts by mass, there is a risk that the effect of suppressing the lifting of the glass to the surface of the thick film conductor may not be expected, and plating properties may not be improved. On the other hand, if this content is 3.5 parts by mass, the effect of improving plating properties is sufficiently obtained, and even if the content is higher than this, the effect of improving plating properties is not improved.

The plating properties of thick film conductors are studied. If the glass floats on the surface of the thick film conductor, the adhesion of plating such as Ni plating to the surface of the thick film conductor deteriorates. If the adhesion of Ni plating or Sn alloy-based plating to the surface of the thick film conductor is poor, and if there are pinholes or other holes in these plating surfaces, the Ag in the thick film conductor will be sulfurized by the sulfur component in the atmosphere, which will lead to poor connection of electronic components. There are concerns.

However, if we examine the meltability of lead-free glass and glass that contains lead as a component rather than inevitably, in the process of raising the temperature, it is found that even if both have the same softening point, the lead-free glass melts. The temperature is on the high temperature side. In the firing process to obtain a thick film conductor, the glass is bonded to a ceramic substrate such as an alumina substrate for a limited period of time during which the molten state of the glass is obtained during heating and maintaining the peak temperature for a certain period of time, thereby ensuring the adhesion of the thick film conductor. We are securing it. Since lead-free glass does not melt easily, it is necessary to increase the content of glass powder in the powder composition for forming a thick film conductor using lead-free glass for adhesion to the substrate. However, if the content of glass powder exceeds 1.5 parts by mass with respect to 100 parts by mass of the conductive powder, floating of the glass may occur on the surface of the thick film conductor. Even if the glass content per 100 parts by mass of the conductive powder exceeds 1.5 parts by mass, when the glass content is close to 1.5 parts by mass, the lifting of the glass is localized, but as the glass content increases, the thickness of the thick film conductor The area over which the glass floats on the surface increases. Therefore, by setting the content of manganese oxide powder to 0.5 parts by mass and 3.5 parts by mass with respect to 100 parts by mass of the conductive powder, the plating properties of the thick film conductor are improved, the sulfuration of Ag in the plated thick film conductor is prevented, etc. As a result, connection defects in electronic components can be improved.

Additionally, when a thick film conductor is formed using a powder composition for forming a thick film conductor using lead-free glass, when the content of manganese oxide per 100 parts by mass of the conductive powder is less than 0.5 parts by mass, the adhesion to the ceramic substrate is improved. However, there is a risk that the plating properties may not be improved. On the other hand, if the content of manganese oxide per 100 parts by mass of the conductive powder exceeds 3.5 parts by mass, the adhesion to the ceramic substrate may decrease. From this point of view, the content of manganese oxide relative to 100 parts by mass of the electrically conductive powder is preferably 0.5 parts by mass or more and 3 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.5 parts by mass or less.

Additionally, the number average particle diameter of the manganese oxide powder is preferably 0.8 μm or less, and more preferably 0.2 μm or more and 0.8 μm or less from the viewpoint of suppressing the phenomenon of glass lifting on the surface of the thick film conductor. If the number average particle diameter is larger than 0.8 μm, homogeneous dispersion with the conductive powder or lead-free glass powder is not possible, and there is a risk that the manganese oxide powder may become unevenly distributed. In addition, powders with a number average particle diameter of less than 0.2 μm can be used, but powders with a number average particle diameter of 0.2 μm or more are generally readily available. Here, the number average particle size is the number average particle size determined from a scanning micrograph (SEM image) of the powder.

Additionally, as the manganese oxide, MnO ₂ (manganese dioxide) or Mn ₃ O ₄ (trimanganese tetroxide) can be used. For example, by using Mn ₃ O ₄ (trimanganese tetroxide), fine steps are formed on the surface of the thick film conductor. Stripes are formed, which can exert an anchor effect.

(Oxide Powder)

The powder composition for forming a thick film conductor may contain, in addition to the lead-free glass powder and manganese oxide powder described above, oxide powders other than these as long as they do not impair the effect of the present invention. For example, for the purpose of improving the adhesive strength, acid resistance, solder wettability, etc. of thick film conductors, at least one type of oxide powder such as Bi ₂ O ₃ , SiO ₂ , CuO, ZnO, TiO ₂ , ZrO ₂ , MnO _{2 ,} etc. It can be added. However, from the viewpoint of suppressing the increase in resistance value, the content of oxide powders other than lead-free glass powder and manganese oxide powder is limited to a range of about 0 to 10 parts by mass in total with respect to 100 parts by mass of the conductive powder. It is desirable.

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

[(2) Paste for forming thick film conductors]

An example of the paste for forming a thick film conductor of the present invention is a paste containing a mixture of the powder composition for forming a thick film conductor described above, a solvent, and a resin.

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

The content of the paste for forming a thick film conductor 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 so high that application becomes practically impossible, and if the content exceeds 250 parts by mass, the density of the film of the thick film conductor after sintering or the sedimentation of particles is greatly reduced. There is a risk that problems may arise. Considering printability, ease of application, sedimentation of particles as a paste, and film density of a thick film conductor, this content is preferably set to 20 parts by mass or more and 100 parts by mass or less.

The paste for forming a thick film conductor of the present invention can be produced by kneading a powder composition for forming a thick film conductor and an organic vehicle. The kneading method is not particularly limited, but kneading can be done using, for example, known techniques such as a wet kneading mill, roll mill, or tapered roll mill. Additionally, the viscosity of the resulting conductor paste is appropriately selected depending on the film thickness of the target thick-film conductor, the type of ceramic substrate, etc.

In addition, other examples of the paste for forming a thick film conductor 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 set to the amount 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 per 100 parts by mass of the conductive particles. there is.

The content of conductive particles, lead-free glass particles, manganese oxide particles, lead-free glass particles, and content of manganese oxide particles are the same as described in the section on powder composition for forming thick film conductors above, and the description here is omitted. . In addition, since the solvent and resin are the same as those described in the example of the paste for forming a thick film conductor, description thereof will be omitted.

The paste for forming a thick film conductor 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 this mixture. The kneading method is not particularly limited, but kneading can be done using, for example, known techniques such as a wet kneading mill, roll mill, or tapered roll mill. Additionally, the viscosity of the resulting conductor paste is appropriately selected depending on the film thickness of the target thick-film conductor, the type of ceramic substrate, etc.

In addition, the paste for forming a thick film conductor described above can contain, in addition to the lead-free glass powder and manganese oxide powder, oxide powders other than these as long as they do not impair the effect of the present invention. For example, for the purpose of improving the adhesive strength, acid resistance, solder wettability, etc. of thick film conductors, at least one type of oxide powder such as Bi ₂ O ₃ , SiO ₂ , CuO, ZnO, TiO ₂ , ZrO ₂ , MnO _{2 ,} etc. It can be added. However, from the viewpoint of suppressing the increase in resistance value, the content of oxide powders other than lead-free glass powder and manganese oxide powder is limited to a range of about 0 to 10 parts by mass in total with respect to 100 parts by mass of the conductive powder. It is desirable.

[(3) Manufacturing method of thick film conductor]

The method for producing a thick film conductor includes, for example, an application process of applying the paste for forming a thick film conductor of the present invention to a ceramic substrate, a drying process of drying the substrate to which the paste has been applied, and then a temperature of 500°C or more and less than 900°C. It may include a firing process of firing at a high temperature.

(Application process)

In addition, the application method is not particularly limited, and known techniques such as screen printing, relief printing, or gravure printing, and other drawing methods using a dispenser can be used, but mass production with an appropriate film thickness is possible. From the viewpoint of implementation, it is preferable to apply by screen printing. As a ceramic substrate, a 96% alumina substrate, forsterite, etc. are used depending on the purpose of the electronic component, but the paste for forming a thick film conductor of the present invention can be applied to any substrate.

(drying process)

After applying the paste for forming a thick film conductor, it is preferable to dry the applied film on the ceramic substrate under temperature conditions of 80°C or more and 200°C or less for 2 minutes or more and 15 minutes or less. In this way, by forming a drying process between the application process and the firing process, it is possible to prevent volatilization and combustion of solvents, etc. due to the remaining volatile components such as solvents even during firing, when a firing furnace is used in the firing process. For example, the effect of preventing contamination of the kiln can be obtained. In this step, the drying method is not particularly limited, and known means such as an oven or a belt-type drying furnace can be used. However, from the viewpoint of mass production, drying using a belt-type drying furnace is preferable. Additionally, if the drying temperature is lower than 80°C, it may not be preferable because the time required for drying becomes longer and productivity deteriorates. Additionally, if the drying temperature exceeds 200°C, it is not preferable because the resin may be oxidized and the film after drying may become brittle.

(firing process)

In the firing process after the drying process, the dried film is heated as a ceramic substrate and the film is fired. As a firing method, it is preferable to use a belt furnace. In this case, the peak temperature during firing is 500°C or more and less than 900°C, and is preferably 700°C or more and less than 900°C. If the peak temperature is less than 500°C, the glass powder is not sufficiently melted, which may lead to problems of poor adhesion to the ceramic substrate. On the other hand, if the peak temperature exceeds 900°C, there is a risk of under-condensation of the film, and especially when a paste for forming a thick film conductor containing Ag, which has a low melting point as the main component, is used, conductive particles and glass particles, etc. are separated, forming a thick film conductor. There is a risk that a problem may occur in that the electrode film is formed into islands and a uniform electrode film is not formed.

At the above peak temperature, it is necessary to maintain it for not less than 5 minutes but not more than 20 minutes, preferably not less than 7 minutes but not more than 13 minutes. If the peak temperature holding time exceeds 20 minutes, the thick conductor film may be under-sintered, and if this holding time is less than 5 minutes, there is a risk of insufficient sintering. In addition, the total time of the firing process, which includes raising the temperature to the peak temperature, maintaining the peak temperature, and cooling from the peak temperature, must be 20 minutes or more and 90 minutes or less, and 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 of cracking in the thick film conductor due to sudden temperature changes. Additionally, if the total time exceeds 90 minutes, there is a risk that productivity will deteriorate.

In order to bake at the above-mentioned peak temperature and firing time, the temperature increase rate to the peak temperature is 20 ℃/min or more and 150 ℃/min or less, and the cooling rate from the peak temperature is 20 ℃/min or more to 200 ℃/min or less. It is desirable to do so. If the temperature increase rate is less than 20°C/min or the cooling rate is less than 20°C/min, it is not preferable because productivity may deteriorate. Additionally, if the temperature increase rate exceeds 150°C/min or the cooling rate exceeds 200°C/min, it is not preferable because there is a possibility that cracks may occur in the thick film conductor due to the rapid temperature change.

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

[(4) Thick film conductor]

The thick film conductor obtained from the paste for forming a thick film conductor of the present invention by the above manufacturing method contains a conductive component, a glass component obtained by melting glass powder, and manganese oxide. Manganese oxide means a state in which it is dissolved or dissolved in glass.

And because the thick film conductor contains manganese oxide, the glass is less likely to float on the surface and fine step-like stripes are generated on the surface.

The preferable film thickness of the thick film conductor is 5.0 μm or more and 10.0 μm or less. If the film thickness is within this range, the adhesion of the thick film conductor to the ceramic substrate can be satisfied while the lifting of the glass to the surface of the thick film conductor can be suppressed.

Accordingly, the thick film conductor manufactured using the paste for forming a thick film conductor of the present invention has very excellent properties, such as good adhesive strength to the ceramic substrate and satisfactory plating adhesion. Good plating adhesion can be evaluated based on the film thickness of Ni electroplating. When Ni electroplating is performed at the same current density, a thick film conductor with glass lifting even locally on the surface has a thinner plating film thickness than a thick film conductor with manganese oxide added to suppress glass lifting on the surface. Losing is confirmed.

Example

Hereinafter, the present invention will be further explained based on examples, but the scope of the present invention is not limited by these examples.

In Examples 1 to 7 and Comparative Examples 1 to 3, a powder composition for forming a thick film conductor was prepared using the electrically conductive powder and manganese oxide powder shown below and any of the spherical lead-free glass powders 1 and 2 shown in Table 1; A paste for forming a thick film conductor was produced, and a thick film conductor was also manufactured. For the obtained thick film conductor, the baked film thickness was measured, the surface condition was observed, the resistance value was measured, and the adhesive strength with the substrate was evaluated. In addition, the total amount of alkali metal oxides in Table 1 is mainly the total amount of metal oxides of Li, K, and Na.

[Table 1]

(Challenge powder)

As the conductive powder, silver powder or alloy powder of silver and palladium was used. Silver powder A is a powder with a number average particle diameter of 2.0 μm, and silver powder B is a powder with a number average particle diameter of 5.0 μm. Additionally, the palladium powder has a number average particle diameter of 0.2 μm.

(Manganese oxide powder)

As the manganese oxide powder, Mn ₃ O ₄ (number average particle diameter 0.5 μm) was used.

[Production of powder composition for forming thick film conductor]

The electrically conductive powder, lead-free glass powder, and manganese oxide powder were mixed to have the composition shown in Table 2, and stirred with a ball mill to produce a powder composition for forming a thick film conductor.

[Production of paste for forming thick film conductors]

A paste for forming a thick film conductor was produced by mixing 72.5% by mass of the powder composition for forming a thick film conductor prepared above with 27.5% by mass of an organic vehicle, and then kneading the mixture with a three-roll mill. Additionally, the organic vehicle was produced by mixing 7% by mass of ethylcellulose with 93% by mass of terpineol solution as a solvent and heating to dissolve the ethylcellulose.

[Manufacture of thick film conductor]

The paste for forming a thick film conductor prepared above was screen printed on a 96% alumina substrate (25.4 mm × 25.4 mm × 1 mm) using a screen printer (coating process), and dried at 150°C for 5 days using a belt-type drying furnace. It was dried for a minute (drying process). 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 process), to form a thick film conductor with a predetermined pattern.

[Evaluation of physical properties of thick film conductors]

For the thick film conductor manufactured above, the baked film thickness was measured, the surface state was observed, the resistance value was measured, the adhesive strength with the alumina substrate, and the plating film thickness of nickel plating were evaluated by the methods shown below. . The evaluation results are shown in Table 2.

(Measurement of fired film thickness)

The film thickness of the thick film conductor after firing was measured at n = 5 using a contact surface roughness meter.

(Plating film thickness)

In a sample in which Ni electroplating was performed on a fired thick film conductor, the thickness from the alumina substrate to the Ni electroplated surface was measured at n = 5 using a contact surface roughness meter, and the film thickness of the thick film conductor was subtracted from the obtained results to obtain the plating film. The thickness was calculated.

(Observation of surface condition)

The surface condition of the thick film conductor was observed using a SEM (scanning electron microscope) to confirm the presence or absence of step-like stripes and the presence or absence of lifting of the glass. In addition, 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.

(resistance value measurement)

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

(Evaluation of adhesive strength)

A Ni plating solution was prepared to contain 280 g/l nickel sulfate, 60 g/l nickel chloride, and 40 g/l boric acid on a thick film conductor manufactured in a 2.0 mm Using the plating solution, Ni electroplating was performed for 2 minutes at a current density of 5 × 10 ^-3 A/mm2 (5 × 10 ^-9 A/m2) to prepare a sample. To the sample on which this plating was performed, a Sn-plated copper wire with a diameter of 0.65 mm was soldered using a lead-free solder with a composition of 96.5 mass% Sn-3 mass% Ag-0.5 mass% Cu, and this 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 vertical direction of the alumina substrate using a tensile tester, peeling the thick conductor film from the alumina substrate, measuring the tensile force at the time of peeling, and measuring the maximum value, minimum value, and The average value was calculated and evaluated. In addition, the thermal deterioration adhesive strength was evaluated by applying a heat load at 150°C for 24 hours to the same test piece as above to deteriorate it, then performing a tensile test in the same manner and calculating the maximum, minimum, and average values. A test piece with both initial adhesive strength and thermal deterioration adhesive strength of 15 was evaluated.

[Table 2]

(About film thickness and resistance value of thick film conductor)

The film thickness of the thick film conductor was within the range of 5.0 μm or more and 10.0 μm or less in both Examples 1 to 7 and Comparative Examples 1 to 3, and no abnormalities were observed in the film thickness. Also, with respect to the resistance value, differences were recognized depending on whether silver or silver and palladium were used as the electrically conductive powder, but there was no abnormality in these values, and any of Examples 1 to 7 and Comparative Examples 1 to 3 It was a value without any problems.

(Evaluation of adhesive strength)

From the results of Examples 1 to 7, there was no problem with the adhesive strength in either the initial evaluation or the evaluation after thermal deterioration. Additionally, the effect of increasing the adhesive strength both initially and after thermal deterioration was confirmed by using glass powder containing bismuth (Examples 5 and 6).

Moreover, from the results of Examples 1 to 3 and Comparative Example 1, the effect of increasing the adhesive strength by containing manganese was confirmed both at the initial stage and after thermal deterioration. This effect was significantly confirmed when silver and palladium were used together as conductive powders (Example 4, Comparative Example 2), and resulted in a significant effect on the adhesive strength, especially after thermal deterioration.

In addition, it was confirmed that the effect of manganese content on adhesive strength is exerted when it is contained at 0.3 parts by mass per 100 parts by mass of the conductive powder (Comparative Example 3).

(Observation results of surface condition)

In Examples 1 to 7, step-like stripes due to the inclusion of manganese were confirmed, showing that the surface was in a state in which improvement in plating adhesion due to the anchor effect could be expected. In Comparative Examples 1 and 2, manganese was not contained and no stripes were observed. Additionally, in Comparative Example 3, some stripes due to the inclusion of manganese were observed, but the shape was not so stepped that an anchor effect could be expected.

In addition, regarding the presence or absence of lifting of the glass, in Examples 1 to 7, lifting of the glass was not confirmed by containing manganese, and it was found that yellowing of silver can be suppressed. Additionally, in Comparative Example 3, it was confirmed that the manganese content was insufficient because the glass was observed to float. In addition, in Comparative Examples 1 and 2, the glass was confirmed to float due to the absence of manganese, and the results suggested that there was a risk of silver sulfuration occurring even if Ni plating etc. were performed.

(Plating film thickness)

Comparing the Ni electroplating film thicknesses of Examples 2 and 7 and Comparative Example 1, it can be seen that Examples 2 and 7, which contain manganese oxide, are thicker than Comparative Example 1, which does not contain manganese oxide. It is also clear that the plating adhesion of a thick film conductor obtained from a powder composition for forming a thick film conductor to which manganese oxide is added is superior to that of a thick film conductor that does not contain manganese oxide.

[organize]

As is clear from the examples, according to the powder composition for forming a thick film conductor and the method for producing a paste for forming a thick film conductor of the present invention, it is possible to provide a thick film conductor to which plating is easy to adhere and to which sulfurization of silver can be suppressed. Obvious.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these examples. It is clear to those of ordinary skill in the technical field to which the present invention belongs that various changes or modifications can be made within the scope of the technical idea described in the patent claims, and of course, It is understood that it will fall within the technical scope of the present invention.

10: Alumina substrate
20: internal electrode
21: top electrode
22: side electrode
23: back electrode
30: Resistance film
40: Shield
50: middle electrode
60: external electrode
100: chip resistor

Claims (7)

challenge powder,
lead-free glass powder,
Contains manganese oxide powder,
The content of the glass powder is 1.5 parts by mass or more and 3 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. According to claim 1,
A powder composition for forming a thick film conductor, wherein the manganese oxide powder is Mn ₃ O ₄ powder. According to claim 1,
A powder composition for forming a thick film conductor, wherein the conductive powder is at least one selected from silver powder, palladium powder, and platinum powder. According to claim 1,
A powder composition for forming a thick film conductor, wherein the glass powder has a glass transition temperature of 400°C or more and 600°C or less and a softening point of 500°C or more and 700°C or less. According to claim 1,
A powder composition for forming a thick film conductor, wherein the glass powder contains bismuth. The powder composition for forming a thick film conductor according to any one of claims 1 to 5,
With solvent,
A paste for forming thick film conductors comprising a mixture of resins. Conductive particles,
lead-free glass particles,
Manganese oxide particles,
With solvent,
Contains resin,
The content of the glass particles is 1.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the conductive particles,
A 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.

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