JP4974268B2 - Resistance paste and thick film resistor manufacturing method - Google Patents

Description

  The present invention relates to a resistance paste for forming a thick film resistor not containing lead, and a method of manufacturing a thick film resistor using the resistance paste.

Conventionally, as a resistance paste for forming a thick film resistor, a paste containing a conductive material containing lead such as Pb ₂ Ru ₂ O _6.5 has been generally used. However, since lead causes environmental pollution, a resistance paste not containing lead has been proposed (for example, Patent Document 1).
JP-A-8-253342

Regarding resistor paste for thick film resistors, resistors with a low sheet resistance (1 kΩ / □ or less) can be obtained by using RuO ₂ as the conductive material. This can be realized by using a lead-free resistance paste. However, candidates for a suitable lead-free conductive material for obtaining a higher sheet resistance value have not been narrowed down, and a resistance material that satisfies the characteristics as a thick film resistor has not been found. The characteristic as a thick film resistor here is that a required resistance value is obtained and, for example, a resistance temperature coefficient (TCR) is in a range of about ± 100 (10 ⁻⁶ / K).

  The present invention has been made in view of the above-described circumstances, and as a resistance paste for forming a thick film resistor, it does not contain lead, has a high sheet resistance value, and has good characteristics. It aims at providing the resistance paste obtained. It is another object of the present invention to provide a method for manufacturing a lead-free thick film resistor using the above-described resistance paste containing no lead.

In order to solve the above-mentioned problems, the resistive paste of the present invention is characterized by kneading a conductive material made only of Bi ₃ Ru ₃ O _{11, a} glass material not containing lead, and a vehicle.

Further, the method for manufacturing a thick film resistor of the present invention provides a resistance paste prepared by kneading a conductive material composed only of Bi ₃ Ru ₃ O _{11, a} glass material not containing lead, and a vehicle. Is printed in a predetermined pattern on the ceramic substrate, and the ceramic substrate on which the resistance paste is printed is fired at a temperature lower than 850 ° C.

According to the present invention, by using a conductive material made of Bi ₃ Ru ₃ O _11, a high sheet resistance value (1 kΩ / □ or more) equivalent to that of a conventional lead-containing resistance material (Pb ₂ Ru ₂ O _6.5, etc.) ) And good TCR characteristics can be obtained. Therefore, by using the above-mentioned resistance paste, it is possible to manufacture a lead-free thick film resistor having good electrical characteristics.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same function, and the duplicate description is abbreviate | omitted.

FIG. 1 shows a process for producing a resistance paste according to an embodiment of the present invention. A lead-free thick film resistor is required which has a high sheet resistance (1 kΩ / □ or more) and a TCR characteristic close to zero. Therefore, attention was paid to Bi ₃ Ru ₃ O ₁₁ as a resistance material that can obtain a TCR value close to 0 and lead-free and high sheet resistance, and a resistance paste was produced using this.

Bi ₃ Ru ₃ O ₁₁ is used as the conductive material, Bi ₂ O ₃ —SiO ₂ —B ₂ O ₃ glass is used as the glass material, and ethyl cellulose, α-terpineol, and texanol are used as the vehicle. The conductive material is 30 wt% and the glass material is 70 wt%. An appropriate amount of vehicle is added thereto, and kneaded using three rolls to obtain a resistance paste. The ratio between the conductive material and the glass material can be adjusted according to the resistance value of the finished product. Considering characteristics, workability, etc., the conductive material is desirably 10 wt% to 70 wt%.

The glass composition is not particularly limited as long as it is lead-free, based on SiO ₂ -B ₂ O ₃ , Bi ₂ O ₃ , CaO, SrO, BaO, ZnO, Al ₂ O ₃ , TiO ₂ , ZrO, MnO Further, an oxide such as NiO may be added. As the vehicle, ethyl cellulose was used, but any of those usually used for this type of thick film resistance paste can be used.

Note that the resistor pastes, resistance · TCR · thermal expansion _{modifier, CuO, TiO 2, ZnO,} MgO, MnO, V 2 O 5, Al 2 O 3, ZrO, and Fe ₂ O ₃ or the like is added May be.

Bi ₃ Ru ₃ O ₁₁ is used as a catalyst for oxidation of organic substances, and the following method is known as an example of a process for obtaining Bi ₃ Ru ₃ O ₁₁ (“Bismuth Ruthenium”). Oxides, Neutron Diffraction and Photoelectron Spectroscopic Study of Bi ₃ Ru ₂ O ₇ and Bi ₃ Ru ₃ O _11. ”GRFacer, Aust. J. Chem, 1993, 46, 1897-1907).

That is, RuO ₂ and Bi ₂ O ₃ powders are wet-mixed in an air atmosphere,
Firing is performed at 450 ° C. for 48 hours → 650 ° C. for 48 hours → 750 ° C. for 96 hours, and Bi ₃ Ru ₃ O ₁₁ is formed by solid phase reaction. Powdering is performed during each heat treatment.

As a result of studies, the present inventors have found a more preferable method for producing Bi ₃ Ru ₃ O ₁₁ . FIG. 2 shows an example of a process for obtaining Bi ₃ Ru ₃ O ₁₁ found by the present inventors.
First, as a pretreatment, RuO ₂ powder is heat-treated at 1000 ± 5 ° C. for 2 hours.
Next, the pretreated RuO ₂ powder and Bi ₂ O ₃ powder are wet-mixed at a ratio of 2: 1. And in the atmosphere,
450 ± 5 ° C for 48 hours → Cool to room temperature → 750 ± 5 ° C for 48 hours → Cool to room temperature, powdered
Perform the following process. Thereby, Bi ₃ Ru ₃ O ₁₁ powder is obtained. The temperature increase / decrease was performed at a rate of 5 ° C./min.

According to the method for producing Bi ₃ Ru ₃ O ₁₁ found by the present inventors, the firing step at 650 ° C. in the conventional method can be omitted. Therefore, since the baking process as a whole is shortened, the manufacturing cost is excellent.

As a side note when making Bi ₃ Ru ₃ O _11, in the process of producing a Bi ₃ Ru ₃ O _11, it is that the Bi ₂ Ru ₂ O ₇ are produced. In the method of the present inventors have found, in advance RuO ₂ by heat treatment at 1000 ° C., since the particle size of the RuO ₂ becomes larger every grain growth, reaction in the mixing process is slow, Bi ₂ It is considered that Bi ₃ Ru ₃ O ₁₁ is easily produced instead of Ru ₂ O ₇ .

Next, samples were prepared using the above-described resistance paste, and the characteristics of each sample when used as a fixed resistor were evaluated. The prepared sample was formed by forming a resistor pattern of 0.5 mm x 0.5 mm square and 5 to 10 µm thick on a ceramic substrate by screen printing, and firing at a temperature in the range of 650 to 850 ° C. is there. Table 1 shows the sheet resistance value, TCR, and firing temperature of the prepared sample. In addition, all baking time is 10 minutes.

Sample 1 has a sheet resistance value of 1364.3 Ω / □ and a relatively high sheet resistance value. However, since TCR is as high as 335.6 (10 ⁻⁶ / K), a favorable characteristic as a fixed resistor is obtained. I couldn't.

Samples 2 to 5 have a relatively high sheet resistance value of 1 kΩ / □ or more, and TCR values within the range of ± 150 (10 ^-6 / K), which can be used as fixed resistors. was gotten. Although the TCR slightly exceeds the range of ± 100 (10 ⁻⁶ / K), it can be adjusted by adding a TCR adjuster.

  Samples 6 and 7 obtained a high sheet resistance value, but obtained a large negative value in TCR, which is not preferable as a fixed resistor. From the above, samples 2 to 5 were usable as fixed resistors in view of the resistor characteristics.

Next, in order to confirm the state of the resistor component, each sample was analyzed by powder X-ray analysis (XRD), and the results were as follows.
For samples 1 and 2, Bi ₃ Ru ₃ O ₁₁ was not detected, but RuO ₂ was detected. Since the firing temperature of the resistor was high, it can be assumed that Bi ₃ Ru ₃ O ₁₁ was decomposed and RuO ₂ was generated.

In Samples 3 and 4, it was confirmed that RuO ₂ was produced. However, since the firing temperature was relatively low, Bi ₃ Ru ₃ O ₁₁ also remained, and it is considered that decomposition into RuO ₂ was suppressed. .
In sample 5, the production of RuO ₂ was slightly confirmed, but most of Bi ₃ Ru ₃ O ₁₁ remains, and it is considered that decomposition into RuO ₂ is substantially suppressed.
In Samples 6 and 7, decomposition into RuO ₂ was suppressed, and the presence of almost only Bi ₃ Ru ₃ O ₁₁ phase could be confirmed. However, since the resistor firing temperature is low, it is considered that the film formation of the glass and the resistance material is insufficient, and the characteristics of the glass alone appear greatly in the TCR.

From the analysis result by the above powder X-ray analysis (XRD), it can be seen that the firing conditions of the resistor greatly affect the decomposition of Bi ₃ Ru ₃ O ₁₁ . In other words, in order to sufficiently suppress the decomposition to RuO ₂ , firing at a temperature not exceeding 850 ° C. can provide a relatively high sheet resistance value and a fixed resistor having good TCR characteristics can be produced. is there.

  Therefore, it is necessary to perform the firing of the resistor in a temperature range lower than 850 ° C., and to produce the resistor without applying a temperature exceeding this in the subsequent steps. Further, at a low firing temperature, the conductive material and the glass material are not sufficiently wetted and do not function as a resistor. For this reason, it is desirable to bake the resistor at a temperature higher than 700 ° C.

  Next, the manufacturing method of the thick film fixed resistor using the resistance paste of this invention is demonstrated with reference to FIG. First, a ceramic substrate such as alumina is prepared. A large number of ceramic substrates can be obtained, and primary division grooves and secondary division grooves are formed in advance.

  Next, a bottom electrode is formed. That is, the lower surface electrode is printed on the ceramic substrate by screen printing. As the electrode material, an Ag-based or Ag-Pd-based paste is used. Bake at 850 ° C. for 10 minutes after printing. Next, the upper surface electrode is printed on the ceramic substrate by screen printing. As the electrode material, an Ag-based or Ag-Pd-based paste is used, and after printing, baked at 850 ° C. for 10 minutes to form a top electrode.

Next, a resistor is formed. A resistor paste containing Bi ₃ Ru ₃ O ₁₁ is printed according to a predetermined pattern by screen printing so as to connect the upper surface electrodes between the upper surface electrodes of the ceramic substrate. Printing characteristics remain the same because conventional vehicles are used. After the resistor is printed, it is fired at a temperature having an upper limit of less than 850 ° C. When the calcination temperature is higher than 850 ° C., decomposition of Bi ₃ Ru ₃ O ₁₁ proceeds and the RuO ₂ component increases, which is not preferable. Further, if the firing temperature is 700 ° C. or lower, the bonding state between the conductive material and the glass material is not sufficient, and a large negative TCR is not preferable.

  Next, the resistance value is adjusted by trimming. This is adjusted by forming a notch in the resistor with a laser beam to obtain a desired resistance value. Then, a protective film is formed so as to cover the resistor. For example, an epoxy resin is used for the protective film. After forming the protective film by screen printing, coating or the like, it is heated to about 200 ° C. and cured. When glass is used as the protective film, it is necessary to raise the temperature for firing the glass, and there is a possibility of promoting the transformation of the resistor. For this reason, it is preferable to use an epoxy resin as the protective film.

  Next, the ceramic substrate is divided along the primary dividing groove to obtain a strip-shaped substrate. And a metal film is formed in the end surface exposed by dividing | segmenting a ceramic substrate in strip shape, and an upper surface electrode and a lower surface electrode are connected. For example, a sputtering method is used as a film forming method, and a Ni—Cr-based metal material is deposited on the end face. Further, the strip-shaped substrate on which the end face electrodes are formed is divided along the secondary dividing grooves to obtain a single chip. Then, plating layers are formed on the surfaces of the upper surface electrode, the lower surface electrode, and the end surface electrode. As the material, it is desirable to use a lead-free Sn-based solder material.

According to the method for manufacturing a thick film resistor described above, since a thick film resistor is formed using a resistor paste containing Bi ₃ Ru ₃ O ₁₁ , a relatively high sheet resistance value of 1 kΩ / □ or more is obtained. The TCR also has a value in the range of ± 150 (10 ⁻⁶ / K), and a characteristic that can be used as a fixed resistor is obtained. And since the resistance paste containing Bi ₃ Ru ₃ O ₁₁ is lead-free, there is no environmental problem. Thereby, even a thick film resistor having a relatively high sheet resistance value can obtain desired electrical characteristics without using a paste containing lead.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

It is a figure which shows the resistance paste of one Embodiment of this invention. The example process of obtaining a Bi ₃ Ru ₃ O ₁₁ of the present invention is a flow diagram showing. It is a flowchart which shows the manufacturing method of the thick film fixed resistor using the resistance paste of this invention.

Claims (4)

A conductive material consisting only of Bi ₃ Ru ₃ O ₁₁ ;
Lead-free glass material,
With the vehicle,
A resistance paste characterized by kneading. Conductive material made of the Bi ₃ Ru ₃ O ₁₁ has a RuO ₂ powder were pretreated 2 hours heating at a pre-1000 ± 5 ° C., the Bi ₂ O ₃ powder 2: wet mixed in a ratio of 1, and the mixed RuO The mixed powder of ₂ and Bi ₂ O ₃ is cooled to room temperature after firing at 450 ± 5 ° C. for 48 hours in air, and further cooled to room temperature after firing at 750 ° C. ± 5 ° C. for 48 hours. The resistance paste according to claim 1, wherein Prepare a resistance paste kneaded with conductive material consisting only of Bi ₃ Ru ₃ O _11, glass material not containing lead, and vehicle,
Printing the resistance paste in a predetermined pattern on a ceramic substrate;
A method of manufacturing a thick film resistor, comprising firing the ceramic substrate on which the resistance paste is printed at a temperature of less than 850 ° C. as an upper limit. The method for manufacturing a thick film resistor according to claim 3 , wherein the firing temperature exceeds 700 ° C.

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