JP7574577B2 - Composition for thick film resistor, paste for thick film resistor, thick film resistor, and method for producing composition for thick film resistor - Google Patents

Description

The present invention relates to a composition for a thick film resistor, a paste for a thick film resistor, a thick film resistor, and a method for producing a composition for a thick film resistor.

Generally, thick film resistors such as chip resistors, hybrid ICs, or resistor networks are formed by printing thick film resistor paste on a ceramic substrate and firing it.

The thick film resistor composition used in the thick film resistor paste generally contains as its main components ruthenium oxide, typically ruthenium oxide, conductive particles such as Ag, Pd, Cu metal particles, or alloy powders containing these, and glass powder, in accordance with the resistance range. In addition, metal oxides may be added as additives to the thick film resistor composition to fine-tune the resistance value and other characteristics.

For example, Patent Document 1 discloses a thick-film resistor composition for forming a printed resistor on an insulating substrate by printing and firing the composition, the thick-film resistor composition having a sheet resistance of 0.1 to 30 Ω/□/10 μm and a TCR of ±50 ppm.

Japanese Patent Application Publication No. 04-206602

For example, in the resistance range of less than 10Ω, suitable materials for the thick-film resistor composition are conductive particles such as silver particles, palladium particles, and alloy particles containing these metals, which have low resistivity, and aluminoborosilicate glass, which has a high softening point of about the firing temperature. In addition, the thick-film resistor composition may further contain metal oxides such as _TiO2 or _Al2O3 as _additives , if necessary.

However, when a thick-film resistor is manufactured on an electrode containing silver using a conventional thick-film resistor composition, there is a problem that voids are generated at the joint surface between the electrode and the thick-film resistor.

In view of the problems of the conventional technology described above, one aspect of the present invention aims to provide a composition for thick-film resistors that can suppress the occurrence of voids between an electrode and a thick-film resistor when the thick-film resistor is fabricated on an electrode.

In order to solve the above problems, the present invention provides:
A composition for a thick film resistor, comprising:
The thick-film resistor composition comprises a conductive powder containing silver particles having an average particle size of 0.5 μm or more and 7.0 μm or less and palladium particles;
aluminoborosilicate glass having a softening point of 750° C. or higher and 900° C. or lower, and containing one or more selected from CaO, MgO, and BaO;
The palladium particles include first particles having an average particle size of 0.05 μm or more and 0.15 μm or less and second particles having an average particle size of 0.25 μm or more and 0.55 μm or less,
The palladium particles contain the first particles in a ratio of 5% by mass to 60% by mass,
The conductive powder provides a composition for a thick-film resistor, which contains the silver particles in a ratio of 44 mass% to 48 mass% when the total content of the silver particles and the palladium particles is taken as 100 mass%.

According to one aspect of the present invention, it is possible to provide a composition for a thick-film resistor that can suppress the occurrence of voids between an electrode and a thick-film resistor when the thick-film resistor is fabricated on an electrode.

1 is an SEM image of a cross section of the thick film resistor of Example 1. 13 is an SEM image of a cross section of the thick film resistor of Example 2. 13 is an SEM image of a cross section of the thick film resistor of Example 3. 13 is an SEM image of a cross section of the thick film resistor of Example 4. 13 is an SEM image of a cross section of the thick film resistor of Comparative Example 1.

Hereinafter, one embodiment of the thick film resistor composition, the method for producing the thick film resistor composition, the thick film resistor paste, and the thick film resistor of the present invention will be described.
[Thick film resistor composition]
Hereinafter, the composition for a thick film resistor according to the present embodiment will be described with reference to the drawings.

The thick-film resistor composition of this embodiment contains a conductive powder and aluminoborosilicate glass. The components contained in the thick-film resistor composition of this embodiment are described below.

(1) Conductive Powder The inventors of the present invention have conducted studies on a composition for a thick film resistor that can suppress the occurrence of voids between an electrode and a thick film resistor when the thick film resistor is formed on an electrode.

As mentioned above, in a thick-film resistor composition intended for thick-film resistors with a resistance value of less than 10 Ω, silver particles and palladium particles, which have low resistivity, can be used as the conductive powder.

When manufacturing a thick-film resistor using a composition for a thick-film resistor containing conductive particles including silver particles and palladium particles, and glass, the thick-film resistor can be manufactured, for example, by the following procedure. First, a paste containing the composition for a thick-film resistor is applied to an electrode containing silver on an alumina (aluminum oxide) substrate. Then, the paste is dried and fired. When firing, the melting point of silver is lower than that of palladium, so the difference in melting time between silver particles and palladium particles is large. In addition, silver has a higher diffusion rate than palladium. For this reason, in a conventional composition for a thick-film resistor, when the palladium particles are heated until they are completely melted, the silver of the electrode diffuses into the thick-film resistor, and voids are generated in the part of the electrode that contained silver before firing. In addition, as described above, the silver of the electrode diffuses toward the thick-film resistor, causing a phenomenon such as electrode eating, in which the electrode becomes thinner. It is presumed that the voids can be suppressed when the heating time is shortened, but since some of the conductive particles are not sufficiently dissolved during heating, it is thought that problems such as fragility will occur in the obtained thick-film resistor.

Further investigations revealed that by using a mixture of two types of palladium particles with different average particle sizes and controlling the difference in melting time between the silver particles and the palladium particles, it is possible to control the distribution of silver and palladium between the electrodes and resistors during firing when fabricating a thick-film resistor. As a result, it was discovered that it is possible to suppress the occurrence of voids between the electrodes and the thick-film resistor, leading to the completion of the present invention.

The conductive powder contained in the thick-film resistor composition of this embodiment can contain silver particles and palladium particles. Each particle is described below.

(1-1) Palladium particles The palladium particles in the conductive powder can include the first particles and the second particles having different average particle sizes, as described above. The palladium powder can be composed only of the first particles and the second particles, but even in this case, it does not exclude the inclusion of inevitable impurities.

The first particles of the palladium powder can have an average particle size of 0.05 μm or more and 0.15 μm or less. The second particles can have an average particle size of 0.25 μm or more and 0.55 μm or less.

In this way, the palladium particles contain first particles and second particles with different average particle sizes, so that when a thick-film resistor is fabricated on an electrode as described above, the occurrence of voids between the electrode and the thick-film resistor can be suppressed.

In this specification, the average particle size means the volume average particle size. The volume average particle size is the average particle size weighted by the particle volume, and is calculated by multiplying the diameter of each particle by the volume of that particle in a particle collection and dividing the sum by the total volume of the particles. The volume average particle size can be measured, for example, by the laser diffraction scattering method using a laser diffraction particle size distribution analyzer.

The content ratio of the first particles in the palladium particles is not particularly limited, but the palladium particles preferably contain the first particles in a ratio of 5% by mass to 60% by mass, and more preferably 10% by mass to 20% by mass. Note that the content ratio of the first particles in the palladium particles here means the content ratio of the first particles when the palladium particles are taken as 100% by mass.

By containing the first particles in the above range in the palladium particles, when a thick-film resistor is fabricated on an electrode, it is possible to more reliably prevent the occurrence of voids between the electrode and the thick-film resistor and the occurrence of electrode erosion, which causes the electrode to become thinner.

(1-2) Silver Particles The particle size of the silver particles is not particularly limited, but the average particle size is preferably from 0.5 μm to 7.0 μm, and more preferably from 1.0 μm to 3.0 μm.

By setting the average particle size of the silver particles within the above range, when used in combination with the previously described palladium particles, it is possible to particularly suppress the occurrence of voids between the electrode and the thick film resistor when a thick film resistor is produced on an electrode using a thick film resistor composition containing the conductive particles.

(1-3) Mixing ratio The mixing ratio of palladium particles and silver particles contained in the conductive particles is not particularly limited. For example, when the total content of silver particles and palladium particles is 100 mass%, it is preferable that the conductive particles contain silver particles in a ratio of 44 mass% or more and 48 mass% or less.

In this case, the content of palladium particles in the conductive particles can be the remainder, i.e., 52% by mass or more and 56% by mass or less.

This is because by setting the content ratio of silver particles within the above range, the temperature coefficient of resistance of the thick-film resistor produced using the thick-film resistor composition containing the conductive particles can be suppressed.

(2) Glass The composition of the glass is not particularly limited, but the softening point of the glass is preferably 750° C. or higher and 900° C. or lower, and more preferably 800° C. or higher and 860° C. or lower.

As the glass, for example, aluminoborosilicate glass containing one or more selected from CaO, MgO, and BaO can be suitably used.

As the glass, for example, aluminoborosilicate glass containing CaO and MgO, which contains _SiO2 at 55% by mass to 65% by mass, _Al2O3 at 10 _% by mass to 15% by mass, _B2O3 at ₃ % by mass to 7% by mass, MgO at 0.5% by mass to 1.5% by mass, CaO at 15% by mass to 25% by mass, and a softening point at 800° C. to 860° C., can be particularly preferably used. Such glass has a high softening point and contains CaO and MgO, and therefore has particularly excellent electrostatic discharge (ESD) characteristics, and can be preferably used.

The average particle size of the glass used in the thick film resistor composition of this embodiment is not particularly limited, but is preferably 0.8 μm or more and 3.0 μm or less, and more preferably 1.0 μm or more and 1.8 μm or less. By making the average particle size of the glass contained in the thick film resistor composition 3.0 μm or less, it is possible to particularly improve the noise characteristics when it is made into a thick film resistor. On the other hand, if the average particle size of the glass is made too small, the productivity will be low and there is a risk of increasing the inclusion of impurities, etc. For this reason, it is preferable that the average particle size of the glass is 0.1 μm or more. The average particle size of the glass can also be measured and calculated by a laser diffraction scattering method using a laser diffraction type particle size distribution meter.

For example, when _Al2O3 is added as an additive, the resistance value may change significantly before and after the pre-coating process before _laser trimming, in which the resistor is cut while being measured one by one. However, by setting the average particle size of the glass to 1.0 μm or more and 1.8 μm or less, it is possible to increase the contact area between _Al2O3 and the _glass , thereby suppressing the change in the resistance value. Therefore, from this viewpoint, it is preferable that the average particle size of the glass is in the above range.

The thick film resistor composition of the present embodiment may contain any optional components other than the conductive powder and glass, for example, the additives described below.
(Additives)
The thick-film resistor composition of this embodiment may contain additives that are generally used for the purpose of improving and adjusting the resistance value, temperature coefficient of resistance, load characteristics, and trimming properties of resistors. Examples of additives include oxides such as _Al2O3 , _SiO2 , _TiO2 , _Nb2O5 , _Mn3O4 , and CuO. The average particle size of the additive is not particularly limited, _but the average particle size of _the additive is preferably 0.5 μm or less, and more preferably _0.1 μm or less. This is because the additive's effect of addition is particularly easily obtained when the average particle size of the additive is 0.5 μm or less, and particularly when the average particle size is 0.1 μm or less, a small amount of the additive is likely to produce a significant effect.

The type of additive to be added is not particularly limited and can be selected according to the characteristics to be improved, etc. For example, with regard to electrostatic load (ESD), when _Al2O3 and _TiO2 are added as additives _, the change in resistance value before and after the load can be reduced, and in particular, when _Al2O3 and _TiO2 are added in combination, _the change in resistance value can be further reduced.

In addition, any of the oxides such as _Al2O3 , SiO2, _{TiO2 , Nb2O5} , _Mn3O4 , _and CuO has the effect of suppressing voids that _tend to occur in the thick-film resistor after firing. Among them _{, Al2O3} can be particularly preferably used for the purpose, since it can particularly suppress the generation of voids in the thick-film resistor. It is considered that _such an effect is obtained because the addition of the additive suppresses the accumulation of small bubbles that exist between the glass frit and the conductive powder during firing of the thick-film resistor.

The amount of additive added is adjusted depending on the type of additive, the purpose of adding it, etc., but when the total content of the conductive powder and the glass powder is 100 parts by mass, it is preferable that the total amount of additive added is 0 to 20 parts by mass.
[Method of manufacturing thick film resistor composition]
According to the method for producing a composition for a thick film resistor, the composition for a thick film resistor described above can be produced, and therefore some of the matters described for the composition for a thick film resistor will not be described here.

The method for producing the thick film resistor composition of this embodiment is not particularly limited, and the composition can be produced by mixing the components contained in the thick film resistor composition described above. Therefore, the method for producing the thick film resistor composition of this embodiment can have, for example, the following mixing step.

A conductive powder containing silver particles having an average particle size of 0.5 μm or more and 7.0 μm or less and palladium particles;
aluminoborosilicate glass having a softening point of 750° C. or higher and 900° C. or lower and containing one or more selected from CaO, MgO, and BaO;

The palladium particles may include first particles having an average particle size of 0.05 μm or more and 0.15 μm or less, and second particles having an average particle size of 0.25 μm or more and 0.55 μm or less.

The conductive powder may contain silver particles in a ratio of 44% by mass to 48% by mass, assuming that the content of silver particles and palladium particles is 100% by mass.

For example, the first particles and second particles contained in the palladium particles may be mixed in advance and then mixed with other components, or the first particles and second particles may be added to the mixing process and the first particles and second particles may be mixed in the mixing process. Similarly, for the conductive particles, silver particles and palladium particles may be mixed in advance and then mixed with other components, or the silver particles and palladium particles may be added to the mixing process and the silver particles and palladium particles may be mixed in the mixing process.

In the mixing step for producing the thick film resistor composition, an organic vehicle used in the thick film resistor paste described later can also be added, and the thick film resistor composition can also be produced at the same time as producing the thick film resistor paste.
[Thick film resistor paste]
An example of the composition of the paste for thick-film resistors according to this embodiment will be described.

The thick-film resistor paste of this embodiment can contain the thick-film resistor composition described above and an organic vehicle. The thick-film resistor composition of this embodiment can have a configuration in which the thick-film resistor composition described above is dispersed in an organic vehicle.

There are no particular limitations on the organic vehicle, and a solution in which a resin is dissolved in a solvent can be used. Examples of the solvent include one or more types selected from terpineol, butyl carbitol, butyl carbitol acetate, etc. Examples of the resin include one or more types selected from ethyl cellulose, acrylic acid esters, methacrylic acid esters, rosin, maleic acid esters, etc.

Dispersants and plasticizers can also be added to the thick film resistor paste as needed.

The method for dispersing the thick film resistor composition and additives in the organic vehicle is not particularly limited, but one or more methods selected from a three-roll mill, a bead mill, a planetary mill, etc., which disperse fine particles, can be used. The blending ratio of the organic vehicle is appropriately adjusted depending on the printing method or coating method, but it is preferable to knead and prepare the organic vehicle so that it is 20 parts by mass or more and 200 parts by mass or less when the thick film resistor composition is 100 parts by mass.

It is particularly preferable for the paste for thick film resistors to satisfy the following composition:

The thick-film resistor paste preferably contains 5% by mass to 30% by mass of organic vehicle, 3% by mass to 30% by mass of aluminoborosilicate glass, 20% by mass to 45% by mass of palladium particles, and 15% by mass to 35% by mass of silver particles. The thick-film resistor paste preferably contains _TiO2 and _Al2O3 as _additives , for example, 1% by mass to 10% by mass of _TiO2 and 0.1% by mass to 5% by mass of _{Al2O3 .}

In addition, the paste for thick film resistors preferably contains, relative to the total amount of the conductive powder and the aluminoborosilicate _glass , an additive such as _Al2O3 in an amount of 0.01% by mass or more and 10% by mass or less, and an additive such as _TiO2 in an amount of 0.01% by mass or more and 10% by mass or less.

As described above, the palladium particles can contain first particles and second particles, and preferably contain the first particles in a proportion of 5% by mass or more and 60% by mass or less, and more preferably contain the first particles in a proportion of 10% by mass or more and 20% by mass or less.

Furthermore, when the total content of silver particles and palladium particles is 100% by mass, it is preferable that the silver particles are contained in a proportion of 44% by mass or more and 48% by mass or less. In this case, it is preferable that the palladium particles are contained in the remainder, that is, in a proportion of 52% by mass or more and 56% by mass or less.

The thick-film resistor paste can be produced by kneading the above-mentioned thick-film resistor composition with an organic vehicle. Note that the above-mentioned raw materials for the thick-film resistor composition can also be mixed and kneaded together with the organic vehicle to produce the thick-film resistor paste together with the thick-film resistor composition.
[Thick film resistor]
The thick film resistor of this embodiment can contain the above-mentioned composition for a thick film resistor.

The method for manufacturing the thick-film resistor of this embodiment is not particularly limited, but for example, the thick-film resistor composition described above can be placed on a ceramic substrate and fired to form the resistor. Alternatively, the thick-film resistor paste described above can be applied to a ceramic substrate and then fired to form the resistor.

The thick film resistor of this embodiment can be manufactured using the thick film resistor composition or thick film resistor paste described above. Therefore, the thick film resistor of this embodiment can contain the thick film resistor composition described above, and can contain the conductive powder and aluminoborosilicate glass described above.

The characteristics of the thick film resistor of this embodiment are not particularly limited, but it is preferable that the sheet resistance value is 0.1 Ω/□ or more and 10 Ω/□ or less.

The thick film resistor of this embodiment preferably has a temperature coefficient of resistance of 100 ppm/°C or less in absolute value. As will be explained in the examples below, there are COLD-TCR and HOT-TCR temperature coefficients of resistance, and it is preferable that both of them satisfy the above range.

The present invention will be described below with reference to specific examples and comparative examples, but it should be understood that the present invention is not limited to these examples.
(Evaluation Method)
The evaluation methods for the thick film resistors produced in the following Examples and Comparative Examples will be described.
(1) Resistance Measurement The film thickness was measured for five thick-film resistors produced under the same conditions in each Example and Comparative Example using a stylus thickness roughness meter (Tokyo Seimitsu Co., Ltd., model number: Surfcom 480B), and the measured values were averaged to calculate the film thickness.

The resistance values of the five manufactured thick-film resistors were measured using a digital multimeter (manufactured by Keithley, No. 2001), and the obtained resistance values were converted into values for a thickness of the thick-film resistor of 7 μm. The average of the converted resistance values of the five thick-film resistors was taken as the resistance value of the thick-film resistor.
(2) Temperature Coefficient of Resistance The temperature coefficient of resistance was calculated by the following procedure.

In each of the following Examples and Comparative Examples, five thick-film resistors with 1 mm width and 50 mm wiring were fabricated under the same conditions, and the resistance value of each thick-film resistor was measured after holding it at -55°C, 25°C, and 125°C for 15 minutes. The resistance values of each thick-film resistor at each temperature are R _-55 , R ₂₅ , and R _125. For example, R _-55 means the resistance value at -55°C.

Next, the low-temperature side temperature coefficient of resistance COLD-TCR and the high-temperature side temperature coefficient of resistance HOT-TCR were calculated for each thick-film resistor using the following formulas (A) and (B). The average of the five thick-film resistors was taken as the temperature coefficient of resistance (COLD-TCR, HOT-TCR) of the thick-film resistors of each Example and Comparative Example.
COLD-TCR (ppm/°C)=(R _-55 - _R25 )/ _R25 /(-80)× ¹⁰⁶ ...(A)
HOT-TCR (ppm/°C) = (R ₁₂₅ - R ₂₅ )/R ₂₅ / (100) x 10 ⁶ ... (B)
It is desirable for the temperature coefficient of resistance to be close to 0, and it is considered that an excellent resistor has a temperature coefficient of resistance of -100 ppm/°C.≦temperature coefficient of resistance≦100 ppm/°C.
(3) Electrostatic Load Test (ESD)
The electrostatic load test was carried out on five thick-film resistors prepared in the same manner in each Example and Comparative Example, by discharging five times for one second at 2 kV using a 200 pF capacitor, and calculating the difference in resistance value of the resistor before and after the load, and averaging the five resistors.
(4) Regarding the occurrence of gaps between the electrodes and the thick-film resistors, and the presence or absence of electrode erosion For the thick-film resistors formed on the alumina substrates and electrodes in the following examples and comparative examples, cross-sectional images were taken by SEM near the contact interfaces between the adjacent components, that is, the alumina substrate, the thick-film resistors, and the electrodes.

When a thick-film resistor is formed on an alumina substrate with electrodes formed on it, the electrodes and the thick-film resistor overlap, resulting in areas that are thicker than the electrode areas. This shows that the areas where the thickness changes are near the interface.

Specifically, for example, in Figures 1 to 5, a straight line L1 is drawn along a portion of the upper surface of the electrode 12 and thick film resistor 13 formed on the substrate 11 that is nearly flat and lower than other portions. Also, a straight line L2 is drawn along a portion of the upper surface of the electrode 12 and thick film resistor 13 where the thickness of the electrode 12 and thick film resistor 13 changes significantly. In this case, the intersection of the straight line L1 and the straight line L2 is the portion where the thickness changes, which is near the interface between the electrode 12 and thick film resistor 13.

When voids exist across the entire interface between the thick film resistor 13 and the electrode 12, the number of voids is very large and the result is rated as "many." In other cases, the number of voids is almost zero and the result is rated as "few."

In addition, from the cross-sectional images taken by the SEM, if the electrodes had become thinner and smaller after the formation of the thick-film resistor compared to before the formation of the thick-film resistor, electrode erosion was evaluated as "present," and if there was almost no change, it was evaluated as "absent."
[Example 1]
20% by mass of an organic vehicle in which ethyl cellulose was dissolved in terpineol, 4% by mass of aluminoborosilicate glass, 34.2% by mass of silver particles, 2.09% by mass of first particles, and 39.71% by mass of second particles were mixed (mixing process) and made into a paste using a three-roll mill.

The aluminoborosilicate glass used had a composition of SiO ₂ : 57.0 mass %, Al ₂ O ₃ : 14.5 mass %, B ₂ O ₃ : 6.0 mass %, CaO: 22.0 mass %, MgO: 0.5 mass %, an average particle size of 1.5 μm, and a softening point of 850° C. The silver particles had an average particle size of 3 μm.

The first and second particles were palladium particles, the first particles had an average particle size of 0.1 μm, and the second particles had an average particle size of 0.3 μm. The palladium particles contained the first particles and the second particles in a mass ratio of first particles:second particles = 5:95, and the content of the first particles in the palladium particles was 5 mass%.

As mentioned above, the average particle size is the volume average particle size, and was calculated from the measurement results using a laser light diffraction scattering type particle size analyzer (Microtrac MT3300EXII, manufactured by Microtrac Bell Co., Ltd.).

This paste was printed on an alumina substrate on which electrodes containing silver were formed, dried, and fired to obtain a resistor, and the resistance value, temperature coefficient of resistance, and ESD characteristics were evaluated as described above. The contact interface between the thick-film resistor and the electrodes was cross-sectionally processed to obtain an SEM image. The results are shown in Table 1 and Figure 1.
[Examples 2 to 4]
A thick-film resistor paste and a thick-film resistor were prepared and evaluated in the same manner as in Example 1, except that the mixing ratio of the first particles and the second particles was changed.

In Example 2, the first particles and the second particles are mixed in a mass ratio of 10:90, and the content of the first particles in the palladium particles is 10 mass%. The entire thick film resistor paste contains 4.18 mass% of the first particles and 37.62 mass% of the second particles.

In Example 3, the first particles and the second particles are mixed in a mass ratio of 30:70, and the content of the first particles in the palladium particles is 30 mass%. The entire thick film resistor paste contains 12.54 mass% of the first particles and 29.26 mass% of the second particles.

In Example 4, the first particles and the second particles are mixed in a mass ratio of 60:40, and the content of the first particles in the palladium particles is 60 mass%. The thick film resistor paste as a whole contains 25.08 mass% of the first particles and 16.72 mass% of the second particles.

The evaluation results are shown in Table 1 and Figures 2 to 4. Figures 2 to 4 are SEM cross-sectional images of the vicinity of the contact interface between the thick film resistor and the electrode of Examples 2 to 4, respectively.
[Comparative Example 1]
A thick-film resistor paste and a thick-film resistor were prepared and evaluated in the same manner as in Example 1, except that the mixing ratio of the first particles and the second particles was changed.

In Comparative Example 1, the palladium particles were composed only of the second particles, without the addition of the first particles. Therefore, the content of the first particles in the palladium particles was 0. The thick film resistor paste as a whole contained 0 first particles and 41.8 mass% of the second particles.

The evaluation results are shown in Table 1 and Figure 5. Figure 5 is a SEM cross-sectional image of the area near the contact interface between the thick film resistor and the electrode.

表１に示したように、実施例１～実施例４で作製した厚膜抵抗体用ペーストは、比較例１で作製した厚膜抵抗体用ペーストと比較して、電極上に厚膜抵抗体を作製した場合に、電極と厚膜抵抗体との間の空隙の発生を抑制できることを確認できた。

As shown in Table 1, it was confirmed that the thick film resistor pastes prepared in Examples 1 to 4 were able to suppress the occurrence of voids between the electrodes and the thick film resistor when a thick film resistor was prepared on an electrode, compared to the thick film resistor paste prepared in Comparative Example 1.

This can be confirmed from the cross-sectional SEM images near the electrodes shown in Figures 1 to 5. In each case, an electrode 12 is provided on an alumina substrate 11. A thick-film resistor 13 is formed on the electrode 12. Region A indicated by the dotted line is the periphery of the interface between the electrode 12 and the thick-film resistor 13, i.e., the region between the electrode and the thick-film resistor. In the case of Comparative Example 1 shown in Figure 5, it can be confirmed that many voids 14 have been formed in the region around the interface between the electrode 12 and the thick-film resistor 13. Furthermore, in Comparative Example 1, the occurrence of voids was also confirmed in region B indicated by the dotted line between the electrode 12 or thick-film resistor 13 and the alumina substrate 11.

Incidentally, in Examples 1 to 4 shown in Figures 1 to 4, the occurrence of voids was confirmed in the region B indicated by the dotted lines between the electrode 12 or thick film resistor 13 and the alumina substrate 11. However, in Examples 1 to 4, it was confirmed that the occurrence of voids 14 was suppressed around the interface between the electrode 12 and the thick film resistor 13, as described above.

It was also confirmed that the thick film resistors produced in Examples 1 to 5 had absolute temperature coefficients of resistance of 100 ppm/°C or less for both COLD-TCR and HOT-TCR. Furthermore, it was confirmed that the thick film resistors produced in Examples 1 to 5 had better ESD characteristics and smaller changes in resistance value before and after load compared to the thick film resistor produced in Comparative Example 1.

11 Substrate 12 Electrode 13 Thick film resistor 14 Gap A Region

Claims (5)

A composition for a thick film resistor, comprising:
The thick-film resistor composition comprises a conductive powder containing silver particles having an average particle size of 0.5 μm or more and 7.0 μm or less and palladium particles;
aluminoborosilicate glass having a softening point of 750° C. or higher and 900° C. or lower, and containing one or more selected from CaO, MgO, and BaO;
The palladium particles include first particles having an average particle size of 0.05 μm or more and 0.15 μm or less and second particles having an average particle size of 0.25 μm or more and 0.55 μm or less,
The palladium particles contain the first particles in a ratio of 5% by mass to 60% by mass,
The conductive powder contains the silver particles in a ratio of 44% by mass or more and 48% by mass or less, when the total content of the silver particles and the palladium particles is 100% by mass. The thick-film resistor composition according to claim 1, wherein the palladium particles contain the first particles in a proportion of 10% by mass or more and 20% by mass or less. A paste for a thick film resistor comprising the composition for a thick film resistor according to claim 1 or 2 and an organic vehicle. A thick film resistor comprising the composition for a thick film resistor according to claim 1 or 2 . A conductive powder containing silver particles having an average particle size of 0.5 μm or more and 7.0 μm or less and palladium particles;
aluminoborosilicate glass having a softening point of 750° C. or more and 900° C. or less and containing one or more selected from CaO, MgO, and BaO;
The palladium particles include first particles having an average particle size of 0.05 μm or more and 0.15 μm or less and second particles having an average particle size of 0.25 μm or more and 0.55 μm or less,
The palladium particles contain the first particles in a ratio of 5% by mass to 60% by mass,
The conductive powder contains the silver particles in a ratio of 44 mass% or more and 48 mass% or less, when the total content of the silver particles and the palladium particles is 100 mass%.