JP2008103372A - Method of adjusting specific resistance of thick-film resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of adjusting a specific resistance of a thick-film resistor obtained by firing a resistor paste containing ITO and glass as inorganic components. <P>SOLUTION: The content of SiO<SB>2</SB>in glass contained in a resistor paste is changed to change the content of In dissolved in the glass after firing, thereby adjusting the specific resistance of the thick-film resistor. The content of In dissolved in the glass is set to be changed in a range of ≤30.3 atom%, and to preferably to be changed in a range of ≤17.2 atom%. The content of SiO<SB>2</SB>in the glass contained in the resistor paste is set to preferably to be changed within a range of 9.9 wt.%. Further, the thick-film resistor after firing preferably contains the glass having a volume ratio of 30-70 vol%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for adjusting the specific resistance of a thick film resistor, and more particularly to a method for adjusting the specific resistance of a thick film resistor obtained by firing a resistor paste containing ITO and glass as inorganic components. .

As a thick film resistance paste that is of interest to the present invention, Japanese Patent Laid-Open No. 3-74005 (Patent Document 1) discloses that the inorganic component is substantially expressed in terms of% by weight of glass powder 20 to 70, ITO 0 to 100, In ₂ O. _{30 to} 99.99, composed of conductive material powder 30 to 80 made of SnO ₂ + SnO ₂ 0 to 20 doped with Sb, and the glass powder is SiO ₂ 12 to 60 and Al ₂ O ₃ 0 to 30 in terms of% by weight. MgO + CaO + SrO + BaO 8-60, MgO 0-40, CaO 0-40, SrO 0-60, BaO 0-60, Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O 0-10, PbO 0-10, ZnO 0-40, ZrO _{2 + TiO 2 0~10, B 2} O 3 4~40, MnO + Fe 2 O 3 + CuO + NiO + MoO 2 + WO 2 + Bi 2 O 3 A resistance paste consisting of + CeO ₂ + CoO + Cr ₂ O ₃ + V ₂ O ₅ + Sb ₂ O ₃ + In ₂ O ₃ + Sn ₂ 0.1-20 is described.

Next, in Japanese Patent Application Laid-Open No. 3-80591 (Patent Document 2), an inorganic component is doped with glass powder 20 to 70, ITO 0 to 100, In ₂ O ₃ 0 to 99.99, and Sb in terms of% by weight. It consists of conductive material powder 30-80 composed of SnO ₂ + SnO ₂ 0-20, and the glass powder is substantially SiO ₂ 15-60, Al ₂ O ₃ 0-30, MgO + CaO + SrO + BaO 10-60, MgO 0 in terms of weight%. _{~40, CaO 0~40, SrO 0~60,} BaO 0~60, Li 2 O + Na 2 O + K 2 O + Cs 2 O 0~10, PbO 0~10, ZnO 0~40, ZrO 2 + TiO 2 0~10, B _A resistance paste consisting of ₂ O ₃ 5-40 is described.

Next, JP-A-2002-343602 (Patent Document 3) contains a non-conductive glass powder (A), a conductive powder (B) and an organic vehicle (C), and the component (A) is: It contains ₂ to 72% by weight of PbO, 5 to 30% by weight of B ₂ O ₃ and _{3 to} 35% by weight of SiO ₂ in terms of oxide, and the component (B) is composed of indium oxide-tin oxide powder. Furthermore, a resistance paste is described in which the component (A) and the component (B) are blended in a proportion of 95 to 65% by weight of the former and 5 to 35% by weight of the latter.

Next, in Japanese Patent Application Laid-Open No. 2004-172250 (Patent Document 4), the non-conductive material contains lath powder (A), conductive powder (B), and organic vehicle (C). 2 to 72% by weight of PbO in terms of oxide, 5 to 30% by weight of B ₂ O ₃ and _{3 to} 35% by weight of SiO _2, and the component (B) is an indium oxide-tin oxide powder and a ruthenium compound. A resistance paste is described which is made of powder and further contains (A) component and (B) component in a proportion of 80 to 95% by weight of the former and 5 to 20% by weight of the latter.

  The resistor paste described in each of Patent Documents 1 to 4 as described above is used to form a thick film resistor, and the resistor paste is applied and fired to form the thick film resistor. The specific resistance of the thick film resistor is generally adjusted by changing the blending ratio of the conductive powder and the non-conductive powder contained in the resistance paste. In addition, in order to make the adjustment of the specific resistance easier and reduce the variation in the adjusted specific resistance, an appropriate inorganic additive may be added, or a conductive powder having a high specific resistance may be used. The above-mentioned patent documents 1 to 4.

  However, if a method capable of adjusting the specific resistance of the thick film resistor obtained by firing the resistance paste is proposed by a simpler method without using the above method, it is beneficial for the technical field. Needless to say.

Further, regarding the resistance pastes described in Patent Documents 1 and 2, the glass softening point is increased because of containing a relatively large amount of SiO _2, and thus a high temperature is required for firing to obtain a thick film resistor. . As a result, the use of the resistance paste is limited. For example, when it is intended to provide a CR composite component in which at least a part of the external electrode of the multilayer ceramic capacitor is formed of a thick film resistor, and thereby the resistance element is connected in series to the capacitor element, at least one of the external electrodes In the firing step for forming the thick film resistor constituting the part, a very high temperature cannot be applied. This is because a metal having a relatively low melting point, such as silver or copper, is often used as the internal electrode material of the multilayer ceramic capacitor, and in the firing process for obtaining a thick film resistor, the melting point of such a metal is exceeded. It is because the temperature of this cannot be provided.
Japanese Patent Laid-Open No. 3-74005 JP-A-3-80591 JP 2002-343602 A JP 2004-172250 A

  Accordingly, an object of the present invention is to provide a method capable of easily adjusting the specific resistance of a thick film resistor obtained by firing a resistance paste.

  Another object of the present invention is to provide a resistance paste that can be fired at a relatively low temperature in order to obtain a thick film resistor whose specific resistance is adjusted as described above.

  The present invention is directed to a method for adjusting the specific resistance of a thick film resistor obtained by firing a resistor paste containing ITO and glass as inorganic components, and the amount of dissolved In in the glass after firing. It is characterized by comprising a step of adjusting the specific resistance of the thick film resistor by changing it within a range of 30.3 atomic% or less.

  In the step of adjusting the specific resistance of the thick film resistor described above, the amount of dissolved In in the glass after firing is more preferably changed within a range of 17.2 atomic% or less.

In order to change the amount of dissolved In in the glass after firing, it is preferable to change the amount of SiO _{2 in} the glass. In this case, the amount of SiO ₂ in the glass is preferably changed within a range of 9.9% by weight or less.

  In the thick film resistor after firing whose specific resistance is adjusted according to the present invention, the volume ratio of the glass is preferably 30 to 70% by volume.

  According to this invention, the specific resistance of the thick film resistor can be easily adjusted by changing the amount of In dissolved in the glass after firing. In this case, it is possible to prevent the thick film resistor from being substantially an insulator by setting the amount of dissolved In to 30.3 atomic% or less in the glass.

  The variation in specific resistance can be reduced by setting the amount of In dissolved in the glass after firing described above to 17.2 atomic% or less.

In dissolution amount into the glass, because it has a relatively good correlation between the amount of SiO ₂ in the glass, by changing the amount of SiO ₂ of glass contained in the resistive paste, In dissolution in glass By changing the amount, the specific resistance of the thick film resistor can be adjusted easily and reliably.

If the amount of SiO ₂ in the glass is changed within the range of 9.9% by weight or less, the resistance paste for obtaining the thick film resistor can be fired at a relatively low temperature. .

  In the thick film resistor after firing, the thermal shock resistance of the thick film resistor can be increased when the volume ratio of the glass is 30 to 70% by volume.

  FIG. 1 is a plan view showing a resistance component as an example of an electronic component including a thick film resistor to which a specific resistance adjusting method according to the present invention is applied.

  As shown in FIG. 1, the resistance component 1 includes a ceramic substrate 2 made of alumina, for example. Two electrodes 3 and 4 are formed on the ceramic substrate 2 at a predetermined interval. The electrodes 3 and 4 are made of, for example, an Ag—Pt alloy. A thick film resistor 5 is formed on the ceramic substrate 2 with a predetermined width so as to straddle the electrodes 3 and 4.

  In such a resistance component 1, a resistance element having a predetermined resistance value provided by the thick film resistor 5 is realized between the electrodes 3 and 4.

  The thick film resistor 5 described above is formed by applying a resistance paste containing ITO and glass as inorganic components to the ceramic substrate 2 by screen printing or the like and firing in a neutral or reducing atmosphere. More specifically, the resistance paste is obtained by kneading ITO powder, glass frit, and an organic vehicle containing an organic binder.

ITO is usually synthesized by dissolving about 1 to 20% by weight of SnO ₂ in In ₂ O ₃ . Here, if the ratio of SnO ₂ is below the above range, the conductivity of ITO is reduced. On the other hand, if it exceeds the above range, the heat treatment necessary for dissolving SnO ₂ becomes high temperature and long time, Grain growth progresses and long pulverization is required for use as a powder. When a paste containing In ₂ O ₃ powder and SnO ₂ is used instead of the ITO powder synthesized in advance as described above, the firing temperature of the resistance paste (usually 600 to 1200 ° C.) The solid solution of both hardly progresses and sufficient conductivity cannot be obtained. Therefore, as ITO, a material that has been heat-treated at a high temperature in advance and sufficiently dissolved is used.

  The particle size of the ITO powder contained in the resistance paste is desirably about 0.3 to 10 μm in average particle size. If the particle size of the ITO powder is less than the above range, pasting becomes difficult. On the other hand, if the particle size exceeds the above range, the number of ITO particles arranged in the thick film resistor 5 decreases, and the variation in resistance value increases. It is.

  The particle size of the glass frit contained in the resistance paste is desirably about 0.3 to 10 μm as an average particle size. This is because if the particle size of the glass frit is less than the above range, it becomes difficult to make a paste, while if it exceeds the above range, the thick film resistor 5 after firing becomes insufficiently densified. Note that the glass frit preferably does not contain lead in consideration of environmental load.

  The specific resistance of the thick film resistor 5 is adjusted by changing the amount of In dissolved in the glass after firing. This is because it has been found that the specific resistance of the thick film resistor 5 has a good correlation with the amount of dissolved In in glass. This will be described in detail below.

  In a resistance paste containing ITO and glass as inorganic components, the specific resistance of the thick film resistor 5 is minimized in a firing temperature range where the viscosity (log η) of the glass contained therein is 2 to 4. Further, when the specific resistance is minimized as described above, the variation in specific resistance is minimized, and therefore an optimum firing temperature exists in the above temperature range. On the other hand, as shown in FIG. 2, the minimum value of the specific resistance changes greatly by changing the type of glass.

  FIG. 2 shows the relationship between the firing temperature and the specific resistance for three types of glasses A, B and C having different glass softening points. The specific resistance is minimized at the firing temperature according to the glass softening point, but the minimal value varies greatly between the glasses A, B and C.

  Therefore, as a result of investigating the cause of the change in the minimum value of the specific resistance depending on the type of glass, it was found that the minimum value of the specific resistance has a correlation with the amount of dissolved In in the glass as shown in FIG. FIG. 3 shows the relationship between the amount of dissolved In in glass and the specific resistance, found in an experimental example to be described later.

  In addition, when In is dissolved with an excessive amount of dissolution exceeding 30.3 atomic% in the glass, the specific resistance is extremely increased and cannot be put into practical use, as supported by an experimental example described later. I know that In addition, it is known from the experimental examples described later that the variation in specific resistance increases when the amount of dissolved In exceeds 17.2 atomic%.

  Therefore, in adjusting the specific resistance of the thick film resistor 5 by changing the amount of In dissolved in the glass, it is necessary to change the amount of dissolved In within a range of 30.3 atomic% or less. Yes, preferably within a range of 17.2 atomic percent or less.

In addition, as shown in FIG. 4, the amount of dissolved In shows a relatively good correlation with the amount of SiO ₂ in the glass. By changing the SiO ₂ ratio, the amount of dissolved In can be changed. It was found that the resistivity can be adjusted. FIG. 4 shows the relationship between the SiO ₂ ratio in glass and the amount of dissolved In, which was found in an experimental example to be described later.

Moreover, in the glass of the same composition system, as shown in FIG. 5, there was a tendency that the glass softening point was increased and the optimum firing temperature was increased as the amount of SiO ₂ increased. FIG. 5 shows the relationship between the SiO ₂ ratio in the glass and the optimum firing temperature found in an experimental example described later. From the above, it can be seen that a resistance paste that can be fired at a low temperature can be realized by controlling the amount of SiO ₂ . More specifically, as supported by an experimental example described later, by setting the amount of SiO ₂ in the glass to 9.9% by weight or less, it becomes possible to perform firing at a temperature of less than 800 ° C.

  In addition, in the thick film resistor 5 after firing, it is preferable to select the composition of the resistance paste so that the glass volume ratio is 30 to 70% by volume. Thereby, the thermal shock resistance of the thick film resistor 5 can be improved, and the absolute value of the resistance change rate by the thermal shock test can be made less than 1%.

  As described above, the resistance component 1 as shown in FIG. 1 has been described as the electronic component including the thick film resistor to which the specific resistance adjusting method according to the present invention is applied. The present invention can also be applied to a multilayer ceramic capacitor that constitutes a CR composite component that includes a body and has a resistance element connected in series to a capacitor element.

  Next, experimental examples carried out to determine the scope and preferred range of the present invention will be described.

(Experimental example 1)
First, ITO powder contained in the resistor paste as SnO ₂ powder is 5% by weight relative to the total amount of _In 2 _{O 3} powder and SnO ₂ powder, a SnO ₂ mixed with _In 2 _{O 3} powder Then, calcination was performed in the air at a temperature of 1400 ° C. for 5 hours to sufficiently dissolve SnO _2, and then subjected to pulverization treatment until the average particle size became about 1 μm.

  On the other hand, as the glass frit contained in the resistance paste, as shown in Table 1, a plurality of types having different compositions and softening points were prepared. Here, the particle diameter of the glass frit which concerns on each prepared sample was 1.0-1.5 micrometers in average particle diameter.

  Next, the ITO powder and glass frit prepared as described above were mixed with an organic vehicle containing 20% by weight of acrylic resin, and a resistance paste was prepared by roll dispersion treatment. In this resistance paste, the volume ratio of (ITO powder) :( glass frit) :( organic vehicle) was 10:10:80.

  Next, similarly to the resistance component 1 shown in FIG. 1, a screen is formed so that two electrodes made of an Ag—Pt alloy straddle between the two electrodes on an alumina substrate previously formed with an interval of 5 mm. A film made of the above-described resistance paste was formed by printing with a width of 3 mm. Next, after drying this resistance paste film at a temperature of 150 ° C. for 10 minutes, the temperature at which the glass softening point (log η) becomes 3.5 in a nitrogen atmosphere (oxygen concentration: less than 5 ppm), that is, shown in Table 1 is shown. The film was fired at the optimum firing temperature for 15 minutes to obtain a thick film resistor. The printing conditions were controlled as described above so that the thickness of the thick film resistor after firing was 5 to 10 μm.

  About the thick film resistor according to each sample thus obtained, the resistance value and the film thickness between the electrodes were measured, and the specific resistance was calculated. The specific resistance shown in Table 1 is an average value for five samples. Further, as shown in Table 1, 3CV, which is an index of variation in specific resistance, was obtained for 5 samples.

  Further, observation with a transmission electron microscope and point analysis by WDX were performed, and the amount of dissolved In in the glass of the thick film resistor according to each sample was measured. The amount of In dissolved in the glass shown in Table 1 is an average value for 5 samples.

  The relationship between the amount of dissolved In and the specific resistance shown in Table 1 is graphed in FIG. As can be seen from FIG. 3, it was confirmed that the specific resistance increased exponentially as the amount of dissolved In increased. Moreover, the tendency for the dispersion | variation in specific resistance to increase was recognized, so that there was much In melt | dissolution amount and specific resistance was high. In this regard, as in samples 1 to 10 and 15 of Table 1, the amount of dissolved In is preferably 17.2 atomic% or less, and thereby, the variation in specific resistance is 20.5% or less at 3 CV. be able to.

  Moreover, in the samples 14 and 16 in which the amount of In dissolved in the glass exceeded 30.3 atomic%, the resistance value between the electrodes could not be measured because the upper limit (1 GΩ) of the resistance measuring instrument was exceeded. These thick film resistors according to Samples 14 and 16 were substantially insulators and could not be put to practical use as resistors in the accurate sense. It can be assumed that this is because the thickness of the glass layer between the ITO particles increases as the amount of dissolved ITO in the glass increases. That is, when the glass layer is thin, electrons can move due to the tunnel conduction effect or the hopping conduction effect, and it behaves as a resistor, but it becomes impossible to move electrons with a certain glass layer thickness as a threshold, It can be inferred that this is because it becomes an insulator.

The relationship between the amount of SiO ₂ (SiO ₂ ratio) in the glass shown in Table 1 and the amount of dissolved In in the glass is graphed in Table 4 described above. Since there is an influence of other components, it is difficult to show a correlation with the dissolved amount of In only by the SiO ₂ ratio in general. However, when compared in the same composition system, the increase in the SiO ₂ ratio can be seen from Table 4. Along with this, there was a tendency for the amount of dissolved In to increase.

The relationship between the amount of SiO _{2 in} the glass shown in Table 1 (SiO ₂ ratio) and the optimum firing temperature (temperature at which the glass viscosity log η becomes 3.5) is graphed in Table 5 described above. As can be seen from Table 5, the optimum firing temperature tended to be lower as the SiO ₂ ratio in the glass was lower. In general, when the firing temperature is too high, there is a problem that characteristics deteriorate due to warpage of the substrate, diffusion of wiring and / or electrode materials, and the like. In view of productivity, energy consumption, etc., the firing temperature is preferably less than 800 ° C. From such a viewpoint, it is desirable that the amount of SiO ₂ in the glass is 9.9% by weight or less as in samples 1 to 4.

(Experimental example 2)
In Experimental Example 2, the optimum range was determined for the volume ratio of the glass in the thick film resistor after firing.

  Using the same glass frit as in the case of Sample 3 in Experimental Example 1, the volume ratio of (ITO powder) :( glass frit) :( organic vehicle) was 4-16: 16-4: 80, and the glass ratios in Table 2 As shown in the column, the components remaining after firing were the same as those in Experimental Example 1 except that ITO was changed in each range of 20 to 80% by volume and glass was changed to 80 to 20% by volume. Through the process, a thick film resistor according to each sample was obtained.

  And about the thick film resistor which concerns on each sample, the resistance value and the film thickness were measured by the method similar to the case of Experimental example 1, the specific resistance was calculated, and this was made into the initial specific resistance. In addition, a thermal shock test was performed for 200 cycles on the thick film resistor formed on the alumina substrate by holding a temperature of −50 ° C. for 30 minutes and then holding a temperature of 150 ° C. for 30 minutes. The specific resistance after the impact test was determined. And the resistance change rate was calculated | required from the formula of resistance change rate = (specific resistance after a test-initial specific resistance) / initial specific resistance. These results are shown in Table 2.

  As shown in Table 2, in Samples 21 and 22 having a glass ratio of 20 to 25% by volume, a significant increase in specific resistance was observed after the thermal shock test. This is thought to be because fine cracks were generated between the ITO particles due to the difference in the coefficient of linear expansion from the substrate during thermal shock because the glass serving as a binder between the ITO particles was insufficient.

  On the other hand, in the samples 23 to 31 having a glass ratio of 30 to 70% by volume, almost no change was observed in the specific resistance before and after the thermal shock test.

  In the samples 32 and 33 having a glass ratio of 75 to 80% by volume, the resistance value exceeded the upper limit of measurement and measurement was impossible. This is considered to be because the glass ratio as an insulator increased and the thickness of the glass layer between ITO particles increased too much.

It is a top view which shows the resistance component 1 as an example of an electronic component provided with the thick film resistor to which the specific resistance adjustment method concerning this invention is applied. It is a figure which shows the relationship between the calcination temperature about 3 types of glass A, B, and C, and a specific resistance. It is a figure which shows the relationship between In dissolution amount and specific resistance about a thick film resistor. It is a diagram showing the relationship between SiO ₂ ratio and the In amount dissolved in the glass for the thick film resistor. It is a diagram showing the relationship between SiO ₂ ratio and the optimum firing temperature in the glass for the thick film resistor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resistance component 2 Ceramic substrate 3, 4 Electrode 5 Thick film resistor

Claims (5)

A method for adjusting the specific resistance of a thick film resistor obtained by firing a resistor paste containing ITO and glass as inorganic components,
A method for adjusting the specific resistance of a thick film resistor, comprising a step of adjusting the specific resistance of the thick film resistor by changing the amount of In dissolved in the glass after firing within a range of 30.3 atomic% or less.   2. The thick film according to claim 1, wherein in the step of adjusting the specific resistance of the thick film resistor, the amount of dissolved In in the glass after firing is changed within a range of 17.2 atomic% or less. Method for adjusting the specific resistance of the resistor. The method for adjusting the specific resistance of the thick film resistor according to claim 1, further comprising a step of changing the amount of SiO ₂ in the glass in order to change the amount of dissolved In in the glass after firing. In the step of varying the amount of SiO ₂ in said glass, the SiO ₂ content of the glass be varied in the range 9.9 wt% or less is performed, the specific resistance adjusting thick film resistor according to claim 3 Method.   The method for adjusting the specific resistance of the thick film resistor according to any one of claims 1 to 4, wherein the glass has a volume ratio of 30 to 70% by volume in the thick film resistor after firing.

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