JP2006165349A - Resistor paste, resistor and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a resistor which is Pb-free, excellent in TCR or STOL and has small variation in resistance value. <P>SOLUTION: A resistor paste contains a substantially lead-free conductive material, a glass composite and an additive, wherein these are dispersed in an organic vehicle. As the additive, the resistor paste contains a composite oxide represented by a general formula ATi<SB>x</SB>O<SB>(1+2x)</SB>(where A means an alkali-earth metal element and x>1.0). In this composite oxide, one part of Ti may be substituted by a substituent element M. The alkali-earth metal element A is selected from among Mg, Ca, Sr and Ba, and two or more kinds of the elements may be contained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resistor paste, and further relates to a resistor and an electronic component formed using the resistor paste.

  The resistor paste is generally composed of a glass composition for adjusting the resistance value and imparting bonding properties, a conductive material, and an organic vehicle as main components. After printing this on the substrate, firing is performed. Thus, a thick film resistor having a thickness of about 5 to 20 μm can be formed. In this type of resistor paste (resistor), lead ruthenium oxide or the like is usually used as the conductive material, and lead oxide (PbO) glass or the like is used as the glass composition.

  By the way, in recent years, environmental problems have been actively discussed. For example, in solder materials, it is required to exclude lead. Resistor paste and resistor are no exception. Therefore, in consideration of the environment, it is possible to use lead ruthenium oxide as a conductive material as described above, or to use PbO-based glass as a glass composition. Must be avoided.

Under these circumstances, research on lead-free resistor paste and resistors has been conducted in various fields. For example, in Patent Document 1, it is preferable to contain, for example, CaTiO ₃ in excess of 0 vol%, 13 vol% or less, or NiO in excess of 0 vol% and 12 vol% in addition to CuO, ZnO, MgO, etc. There is a description that it is preferable to add a substance at the same time, which is suitable for obtaining a resistor having a low resistance temperature characteristic (TCR) and withstand voltage characteristic (STOL) while having a high resistance value. It is described that it is possible to provide a lead-free resistor paste.
JP 2003-197405 A

  By the way, in the technique of the said patent document 1, improvement of TCR and STOL is certainly seen, and the sample whose TCR is 100 ppm or less and STOL is almost zero is also disclosed. However, sufficient characteristics can be obtained for both TCR and STOL only in a very limited composition, with most compositions having a value of 1% or more even though the STOL is small.

  As described above, when the composition capable of obtaining sufficiently good characteristics is limited for both TCR and STOL, for example, the degree of freedom regarding other characteristics is restricted, and there is a possibility that the design of the resistor paste may be hindered. Therefore, further improvement is desired.

  Also, conventional resistor pastes and resistors are not necessarily sufficient in terms of reliability. For example, there is a problem that the resistance value fluctuates due to a heat cycle or the resistance value fluctuates due to overglazing, and an improvement is desired.

  Therefore, the present invention has been proposed in view of such a conventional situation, and in the formed resistor, the temperature characteristic (TCR) and the withstand voltage characteristic (STOL) of the resistance value are surely small regardless of the composition. It is an object of the present invention to provide a resistor paste that can be set to a value and that can ensure sufficient reliability, and thereby has low temperature characteristics (TCR) and withstand voltage characteristics (STOL), and a heat cycle. Another object of the present invention is to provide a resistor having a small change in resistance value after overglazing and to provide an electronic component having excellent resistance characteristics.

  In order to achieve the above-mentioned object, the present inventor has intensively studied for a long time. As a result, in order to make the temperature characteristic (TCR) and the withstand voltage characteristic (STOL) small values and suppress the resistance value fluctuation, the Ti site containing the alkaline earth metal element and titanium is excessive with respect to the alkaline earth metal element. The conclusion was reached that the addition of complex oxides was effective.

The present invention has been completed based on such findings. That is, the resistor paste of the present invention is a resistor paste comprising a conductive material substantially free of lead, a glass composition, and an additive, which are dispersed in an organic vehicle, As a product, it contains a composite oxide represented by the general formula ATi _x O _{(1 + 2x)} (where A represents an alkaline earth metal element, and x> 1.0). .

  In the present invention, it is important to use, as an additive, a special complex oxide that contains the alkaline earth metal element A and titanium, and the Ti site is excessive with respect to the alkaline earth metal element. By adding to the resistor paste, the TCR of the resistor formed is significantly flattened to ± 100 ppm or less. Moreover, about STOL, the value close | similar to zero (0.1% or less) is achieved in a wide composition range. Furthermore, the addition of the composite oxide is effective in improving the reliability, and the resistance value fluctuation can be suppressed even after the heat cycle.

  According to the present invention, it is possible to form a thick film resistor having a high resistance value, and in the obtained resistor, the temperature characteristic (TCR) and the withstand voltage characteristic (STOL) of the resistance value can be ensured regardless of the composition. It is possible to make it a small value. Furthermore, the present invention has an effect that resistance value fluctuation after heat cycle and overglazing can be suppressed, and reliability can be improved.

  Hereinafter, embodiments of a resistor paste, a resistor, and an electronic component to which the present invention is applied will be described in detail.

  The resistor paste of the present invention includes a conductive material substantially free of lead, a glass composition, and an additive, and a resistor composition comprising these components is mixed with an organic vehicle. .

Here, the conductive material has a role of imparting conductivity to the resistor, which is a structure, by being dispersed in the glass composition that is an insulator. As the conductive material, a conductive material that does not substantially contain lead is used. For example, a conductive material containing Ru is used. Examples of the conductive material containing Ru include RuO ₂ and Ru composite oxide. As the Ru composite oxide, one or more selected from CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , and Bi ₂ Ru ₂ O ₇ are preferable.

  The composition of the glass composition is not particularly limited, but in the present invention, it is preferable to use a lead-free glass composition that does not substantially contain lead for environmental protection. In the present invention, “substantially free of lead” means not containing lead exceeding the impurity level, and the amount of impurity level (for example, the content in the glass composition is 0.05 mass). % Or less), it may be contained. Lead may be contained in a trace amount as an inevitable impurity.

  When the glass composition is a resistor, it has a role of binding the conductive material and the additive to the substrate in the resistor. As the glass composition, it is possible to use a material obtained by mixing a raw material modified oxide component, a network-forming oxide component, etc., and vitrifying it. In particular, as a main modified oxide component, an alkaline earth metal oxide is used. Specifically, so-called CaO-based glass using one or more selected from CaO, SrO, and BaO is preferable.

But with the other ingredients in the glass composition, as a network-forming oxide component may include a B ₂ O ₃ and SiO _2. In addition to the main modified oxide component, any other metal oxide can be used as another modified oxide component. Specific examples of the metal oxide include ZrO ₂ , Al ₂ O ₃ , ZnO, CuO, NiO, CoO, MnO, Cr ₂ O ₃ , V ₂ O ₅ , MgO, Li ₂ O, Na ₂ O, and K _2. O, TiO ₂ , SnO ₂ , Y ₂ O ₃ , Fe ₂ O _3, Ta ₂ O ₅ , Nb ₂ O _{5 and the} like can be used, and one or more selected from these may be used. Among them, ZrO ₂ , Ta ₂ O ₅ , and Nb ₂ O ₅ are suitable oxides as components of a glass composition for resistor paste having high resistance, and these are added within a range of 20 mol% or less. It is preferable to do.

  The resistor paste of the present invention includes the conductive material and the glass composition as a basic composition in the resistor composition, and a composite oxide containing an alkaline earth metal element and titanium, in particular, the Ti site is an alkaline earth metal element. In contrast, it is a major feature that an excessive composite oxide is included as an additive.

The complex oxide is a compound represented by the general formula ATi _x O _{(1 + 2x)} (where A represents an alkaline earth metal element), and is greatly characterized by x> 1.0. The value of x is preferably 1.0 <x ≦ 4.0, and more preferably 1.003 ≦ x ≦ 3.0. When x = 1.0, heat cycle and ΔO. Dissatisfaction remains in that sufficient characteristics cannot be obtained in G, and when x> 4.0, there is an inconvenience that reliability is lowered due to an increase in crystal precipitates from the glass component due to an excess of the TiO ₂ component. there is a possibility. Such a composite oxide can be produced, for example, by mixing an oxide of alkaline earth metal element A (or carbonate or the like) and an oxide of titanium at a ratio corresponding to the above general formula and firing.

  In the compound, a part of the Ti site may be substituted with the substitution element M. In this case, the substitution element M is at least one of Zr and Hf. In this case, if the Ti ratio is low, the reactivity with the glass composition during resistor firing changes, and the withstand voltage and reliability may deteriorate, so the element ratio Ti / substituent element Ti / M is preferably 1.0 or more.

  Further, in the above-described composite oxide, even if two or more kinds selected from Mg, Ca, Sr, and Ba are included as the alkaline earth metal element A, both temperature characteristics, voltage resistance, and reliability can be achieved. In the above general formula, each alkaline earth metal element is preferably contained in an element ratio of 1% or more of the entire alkaline earth metal element. Therefore, it is preferable that 0 <y ≦ 0.01. For example, when two types of alkaline earth metal elements are included, if the ratio of one alkaline earth metal element is less than 1%, the effect of including the two types of alkaline earth metal elements may be insufficient. Of two or more types of alkaline earth metal elements, when S is the ratio of the alkaline earth metal element having the smallest ionic radius and R is the ratio of the alkaline earth metal element having the largest ionic radius, R ≧ S It is preferable that This is because in the case of R <S, the reactivity with the glass composition during resistor firing is changed, and there is a risk of deterioration of characteristics.

  As an additive, it is also effective to add a metal material in combination with the composite oxide. In this case, as the metal material, fine particles of any conductive metal can be used, but from the viewpoint of combination with the composite oxide, in addition to simple metals such as Ag and Pd, Ag-Pd, etc. An alloy of Ag or Pd is suitable.

It is preferable to optimize the composition of the resistor component including the aforementioned components. Specifically, the composition of the resistor composition is:
Conductive material: 5-55% by mass
Glass composition: 35 to 65% by mass
Composite oxide: 0 to 30% by mass (however, 0 is not included)
Metal material: 0 to 20% by mass
Other additives: 1 to 20% by mass
It is preferable that

  The composition of the resistor composition is determined from the viewpoint of TCR and STOL in addition to the resistance value, and by setting the above range, the TCR and STOL can be surely made small in each resistance value.

  The resistor composition described above is made into a resistor paste by being dispersed in an organic vehicle. However, any organic vehicle for resistor paste can be used for this type of resistor paste. Yes, for example, a binder resin such as ethyl cellulose, polyvinyl butyral, methacrylic resin, butyl methacrylate, and a solvent such as terpineol, butyl carbitol, butyl carbitol acetate, acetate, toluene, various alcohols, xylene may be used. it can. At this time, various dispersants, activators, plasticizers, and the like can be appropriately used in accordance with the application.

  Although it is the compounding ratio of the said organic vehicle, the ratio (W2 / W1) of the mass (W1) of a resistor composition and the mass (W2) of an organic vehicle is 0.25-4 (W2: W1 = 1: 0). .25 to 1: 4). More preferably, the ratio (W2 / W1) is 0.5-2. If the ratio is outside the above range, a resistor paste having a viscosity suitable for forming a resistor on, for example, a substrate may not be obtained.

  In the resistor paste of the present invention, the addition of the composite oxide can sufficiently improve TCR and STOL without using other additives, but other additives are included as necessary. It may be. Examples of other additives include arbitrary metal oxides, and STOL can be further improved by using CuO in combination. Also for CuO, the optimum range varies depending on the resistance value, and in the resistor composition for resistor paste for producing a resistor of 10 kΩ / □ to 10 MΩ / □, it is preferably 0 to 8% by mass. In the resistor composition for resistor paste for producing a resistor of 1 kΩ / □ to 500 kΩ / □, the content is preferably 0 to 10% by mass.

In order to form the resistor, the resistor paste containing the above-described components may be printed (applied) on the substrate by a method such as screen printing and fired at a temperature of about 850 ° C. As the substrate, a dielectric substrate such as an Al ₂ O ₃ substrate or a BaTiO ₃ substrate, a low-temperature fired ceramic substrate, an AlN substrate, or the like can be used. The substrate form may be any of a single layer substrate, a composite substrate, and a multilayer substrate. In the case of a multilayer substrate, the resistor may be formed on the surface or inside. In the formed resistor, the composition of the resistor composition contained in the thick film resistor paste is maintained almost as it is.

  In forming the resistor, a conductive pattern to be an electrode is usually formed on the substrate, and this conductive pattern is printed by, for example, a conductive paste containing an Ag-based highly conductive material containing Ag, Pt, Pd, or the like. Can be formed. Further, a protective film (overglaze) such as a glass film may be formed on the surface of the formed resistor.

  The electronic component to which the resistor of the present invention can be applied is not particularly limited. For example, a single-layer or multi-layer circuit board, a resistor such as a chip resistor, an isolator element, a CR composite element, a module element, and a laminated layer Capacitors such as chip capacitors, inductors and the like can be mentioned, and the present invention can also be applied to electrode portions such as capacitors and inductors.

  Hereinafter, specific examples of the present invention will be described based on experimental results.

<Preparation of glass composition>
A predetermined amount of B ₂ O ₃ , SiO ₂ , CaCO ₃ , SrCO ₃ , BaCO ₃ , ZrO ₂ , Ta ₂ O _5, etc. was weighed, mixed in a ball mill and dried. The obtained powder was heated to 1300 ° C. at a rate of 5 ° C./min, kept at that temperature for 1 hour, and then rapidly cooled by dropping into water to be vitrified. The obtained vitrified product was pulverized with a ball mill to obtain glass powder. Four types of glass compositions were prepared by changing the ratio of each component. Table 1 shows the composition of the obtained glass powder (glass composition).

<Preparation of organic vehicle>
Using ethyl cellulose as the binder and terpineol as the organic solvent, the organic solvent was prepared by dissolving the binder while heating and stirring the organic solvent.

<Preparation of resistor paste>
Conductive material (conductive material 1 and conductive material 2), glass composition powder, additive (additive 1 and additive 2) and organic vehicle are weighed to each composition and kneaded with a three-roll mill. A resistor paste was obtained. The ratio of the total mass of the conductive material, the glass composition powder and the additive to the mass of the organic vehicle is 1: 0. In mass ratio so that the obtained resistor paste has a viscosity suitable for screen printing. A resistor paste was prepared by blending in the range of 25 to 1: 4.

<Fabrication of resistor>
An Ag—Pt conductor paste was screen-printed in a predetermined shape on an alumina substrate having a purity of 96% and dried. The Ag ratio in the Ag-Pt conductor paste was 95% by mass, and the Pt ratio was 5% by mass. This alumina substrate was placed in a belt furnace and baked in a pattern of 1 hour from charging to discharging. The baking temperature at this time was 850 ° C., and the holding time at that temperature was 10 minutes.

  On the alumina substrate on which the conductor was formed in this manner, the resistor paste prepared previously was applied in a pattern of a predetermined shape (1 mm × 1 mm square shape) by screen printing and dried. Thereafter, the resistor paste was baked under the same conditions as the conductor baking to obtain a resistor.

<Evaluation of resistor characteristics>
(1) Resistance value
Measured with Agilent Technologies product number 34401A. The average value of 24 samples was determined.

(2) TCR
The resistance value change rate when the temperature was changed to −55 ° C. and 125 ° C. was obtained based on the room temperature of 25 ° C. The average value of 10 samples. TCR (ppm / ° C) = [(R-55-R25) / R25 / 80] x when resistance values of -55 ° C, 25 ° C, and 125 ° C are R-55, R25, and R125 (Ω / □). 1000000, or TCR (ppm / ° C.) = [(R125−R25) / R25 / 100] × 1000000. The larger value was taken as the TCR value.

(3) STOL (short-time overload)
A test voltage was applied to the thick film resistor for 5 seconds, and the change rate of the resistance value before and after that was determined. The average value of 10 samples. Test voltage = 2.5 × rated voltage, rated voltage = √ (R / 4), and R is a resistance value (Ω / □). For a resistor having a resistance value with a calculated test voltage exceeding 400V, the test voltage was 400V.

(4) Heat cycle test This is one of the reliability tests of resistors. Exposure of the resistor to −55 ° C. and 125 ° C. for 30 minutes was defined as one cycle, and the resistance value variation rate ΔR (%) was determined when the total of 1000 cycles was repeated. It is preferable that the heat cycle ≦ ± 1.0%.

(5) ΔO. G
A glass glaze was applied so as to cover the resistor, and after drying, a resistance value fluctuation rate was obtained when heat treatment was performed in air at 560 ° C. for 10 minutes.

<Sample 1 to Sample 8>
An example in which a composite oxide with x = 1.0 in the general formula is used as additive 1 (corresponding to a comparative example), or an example in which a composite oxide with x = 3.0 is used as additive 1 (implementation) It corresponds to an example.)

<Sample 9 to Sample 12>
This is an example in which a composite oxide in which the value of x in the general formula is changed is used as the additive 1.

<Sample 13 to Sample 17>
In this example, a composite oxide containing two or more (two types) alkaline earth metal elements is used as additive 1.

<Sample 18 to Sample 23>
This is an example in which the type of the conductive material 1 is changed. Differences in characteristics due to differences in the conductive material 1 for each of the case where a complex oxide where x = 1.0 in the general formula is added and the case where a complex oxide where x = 3.0 is added in the general formula I investigated.

<Sample 24 to Sample 29>
It is the example which changed the kind of used glass composition. The glass compositions 2 to 4 shown in Table 1 for each of the case where the composite oxide having x = 1.0 in the general formula and the case where the composite oxide having x = 3.0 in the general formula are added. The difference in characteristics due to the difference in glass composition was investigated.

<Samples 30, 31>
The difference in characteristics depending on whether or not the conductive material 2 (= Ag) was added and whether or not the additive 2 (= CuO) was added was examined.

<Sample 32 to Sample 34>
In this example, a composite oxide in which a part of Ti is substituted with Zr or Hf is used as the additive 1.

  Table 2 shows the composition of the resistor composition and the characteristics (resistance value, TCR, STOL, heat cycle test, ΔO.G) evaluation results of these samples. In Table 2, samples marked with * are equivalent to comparative examples.

As is apparent from this table, when a complex oxide of an alkaline earth metal element and titanium is added as an additive, TCR ± 100 ppm or less and STOL 0.1% or less are realized. However, when a complex oxide having x = 1.0 in the general formula is added as the additive 1, a heat cycle test or ΔO. In G, it can be seen that the resistance value variation is large. On the other hand, in the case of the complex oxide with x> 1.0, the heat cycle test, ΔO. In any of G, the resistance value fluctuation is ± 1.0% or less, which satisfies the standard. In addition, the said tendency does not change also with the presence or absence of addition of the electroconductive material 2 or the additive 2 with the kind of the electroconductive material 1, the kind of glass composition.

Claims (18)

A resistor paste comprising a conductive material substantially free of lead, a glass composition and an additive, which are dispersed in an organic vehicle,
As the additive, the general formula _{ATi x O (1 + 2x)} ( provided that, A represents an alkaline earth metal element. In addition, x> 1.0.), Characterized by containing a complex oxide represented by A resistor paste.   The resistor paste according to claim 1, wherein 1.0 <x ≦ 4.0 in the general formula.   3. The resistor paste according to claim 1, wherein a part of Ti is substituted by a substitution element M in the general formula.   4. The resistor paste according to claim 3, wherein the substitution element M is at least one of Zr and Hf. The resistor paste according to claim 3 or 4, wherein an element ratio Ti / M of Ti and the substitution element M is 1.0 or more.   6. The resistor paste according to claim 1, wherein, in the general formula, the alkaline earth metal element A is two or more selected from Mg, Ca, Sr, and Ba.   The resistor paste according to claim 6, wherein Ba is included as one of the two or more types of alkaline earth metal elements.   Of the two or more types of alkaline earth metal elements, where S is the ratio of the alkaline earth metal element having the smallest ionic radius and R is the ratio of the alkaline earth metal element having the largest ionic radius, R ≧ S. The resistor paste according to claim 6, wherein the resistor paste is present.   The content of the composite oxide is 0 to 30% by mass (however, zero is not included) when the total of the conductive material, the glass composition, and the additive is 100% by mass. The resistor paste according to any one of claims 1 to 8.   The resistor paste according to claim 1, comprising a metal material.   The resistor paste according to claim 10, wherein the metal material is Ag, Pd, or an alloy thereof.   The resistor paste according to any one of claims 1 to 11, wherein CuO is contained as an additive in a proportion of 10% by mass or less.   The resistor paste according to any one of claims 1 to 12, wherein the glass composition is a glass composition mainly composed of one or more selected from CaO, SrO, and BaO. The glass composition contains B ₂ O ₃ and SiO ₂ as additives, and at least one selected from ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , NiO, ZnO, MnO ₂ , Mn ₂ O ₃ The resistor paste according to claim 13, comprising:   The resistor paste according to claim 1, wherein the conductive material includes a Ru composite oxide. The resistor paste according to claim 15, wherein the Ru composite oxide is one or more selected from CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , and Bi ₂ Ru ₂ O ₇ .   A resistor formed using the resistor paste according to any one of claims 1 to 16.   An electronic component comprising the resistor according to claim 17.