JPH03274703A - Composition for forming resistor film - Google Patents

Abstract

PURPOSE:To improve tenacity strength by using pyrochlore type conductive particles and glass powder which contains germanium oxide as the thick film resistor. CONSTITUTION:A composition for forming a resistor film contains pyrochlore type conductive particles of high coefficient of thermal expansion as the essential constituent to stabilize resistance value with high resistance. However, the composition for forming a resistor film which is a complex sinter of pyrochlore type conductive particles and glass powder is increased in coefficient of thermal expansion. Therefore, it weakens tenacity strength and cracks by thermal shock applied upon laser trimming so as to unstabilize resistance values. To prevent those, it is necessary in improvement of tenacity strength to make a composition for forming a resistor film and an alumina substrate matchable in coefficient of thermal expansion by decreases in the coefficient of thermal expansion of a glass powder used, and to apply the residual load of compression stress. Germanium oxide that is the glass constituent is suitable to decrease the coefficient of thermal expansion of glass powder because of low coefficient of thermal expansion with the result that addition of 1-10wt.% of germanium oxide can yield resistor films excellent in tenacity strength.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a composition for forming a resistive film.

[Conventional technology]

Thick-film resistors used in electronic components such as hybrid ICs, chip resistors, and resistor networks are processed by laser processing for precise resistance adjustment, but in recent years, the processing speed has increased significantly. As a result, the thermal shock applied to thick film resistors has become larger.

There are various glass powders as inorganic binders for thick film resistance pastes, among which PbO-5i02A 12
z(h-Bz03-based glass compositions are generally used. This PbO-3xOz-A l 2
03-B203 series glass has the excellent feature of being able to obtain any desired softening point over a fairly wide temperature range depending on the content of PbO in its components. pb to obtain a glass with a low

A material with a high content of is used. However, high-content PBO glass has a large coefficient of thermal expansion, and in particular, the difference in coefficient of thermal expansion between glass and ceramic substrate is 5.
When X becomes larger than 10-'/''C, strong tensile residual stress distortion occurs in the thick film resistor using glass fired on a ceramic substrate as an inorganic binder, resulting in a decrease in the toughness and strength of the thick film resistor. It also weakens the toughness of the glass itself.Therefore, when performing resistance value adjustment processing by laser trimming, the thermal shock generated by the laser causes macroscopic damage to the thick film resistor if the toughness is weak. Since cranking tends to occur and the resistance value becomes unstable, thick film resistors with strong toughness and strength are desired.

One way to improve the toughness and strength of thick film resistors is to make the thermal expansion coefficient of the glass closer to or smaller than that of the ceramic substrate to reduce compressive residual stress. It can be solved by multiplying.

This method eliminates the pbo content and reduces B2O3, Sin
.

It would be better to increase the content of T2 precepts in the glass structure of the glass network structure, but if you try to obtain an appropriate coefficient of thermal expansion with B2O3 whose melting point is 577°C, the glass fluidity will decrease at the thick film firing temperature of 850°C. This has the disadvantage that thick films cannot be formed properly due to too large a value, and pyrochlore type conductive particles become unstable.Also, when trying to obtain an appropriate coefficient of thermal expansion with SiO□, which has a melting point of 670"C, it becomes difficult to form a thick film. However, there is a drawback that the glass fluidity is lost and the sintering of the composite of the glass powder and the pyrochlore type conductive particles does not progress, making it impossible to form a good thick film.

To try to eliminate these shortcomings, the special
39082, that method involves adding a refractory filler to a thick film resistor paste to lower the coefficient of thermal expansion of the sintered body and improve its toughness and strength. This method has some difficulty in kneading the large-sized filler to uniformly disperse it, and as a result, the current noise of the resistance characteristics deteriorates. Another method is to add other components to glass to strengthen the toughness and strength of the glass itself. In this method, Y2O3,5c203, La2
PbO-5iOz-A 1
It is clear from this comparative example that no effect can be expected with 2203-tbCh glass.

In this way, thick film resistors made of conventional glass compositions and sintered on ceramic substrates have mismatched coefficients of thermal expansion with the ceramic substrate, or have low toughness and strength. During laser trimming, many macro cranks were generated at the cut end of the thick film resistor, making the resistance value extremely unstable.

[Problem to be solved by the invention]

An object of the present invention is to provide a composition for forming a resistive film that improves the toughness and strength of a thick film resistor using a pyrochlore type conductive powder in order to solve the above-mentioned problems.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized in that it contains pyrochlore type conductive particles and glass powder containing 1 to 10% by weight of germanium oxide.

1 Effect] The composition for forming a resistive film contains 10 to 60% by weight of pyrochlore type conductive particles having a large coefficient of thermal expansion as an essential component in order to provide high resistance and stabilize the resistance value.

The thermal expansion coefficient of these pyrochlore type conductive particles such as PbJu206 and BizRu20 is 95 to 120X10"
'/'C, which increases the coefficient of thermal expansion of the composition for forming a resistive film, which is a composite sintered body of pyrochlore type conductive particles and glass powder. The coefficient is 70X10'/"C, and since the difference in thermal expansion coefficient between these three is extremely large, tensile stress remains in the composition for forming a resistive film, weakening the toughness and strength, and making laser treatment difficult. It is thought that the crank will be damaged due to thermal shock during processing, making the resistance value unstable.

To prevent these problems, either reduce the coefficient of thermal expansion of the glass powder used to make the thermal expansion coefficient of the composition for forming a resistive film consistent with that of the alumina substrate, or In order to improve toughness and strength, it is necessary to make the expansion coefficient smaller than that of the alumina substrate and apply residual compressive stress. Therefore, in the present invention, the germanium oxide Ge0z used in the glass composition has a small coefficient of thermal expansion,
Suitable for reducing the thermal expansion coefficient of glass powder,
It also has a melting point of 1086 to 1115°C, which is intermediate between B2O3 and 5i02, and can form a thick film at a thick film firing temperature of 850"C without deteriorating glass fluidity, and has a glass network with toughness and strength. It is a structural oxide.The amount of germanium oxide added is preferably 1-10% by weight.If the amount added is less than 1% by weight, no improvement in toughness and strength is observed;
If the amount exceeds % by weight, the sinterability is poor and a good thick film cannot be formed.

[Example] Examples of the present invention will be described below.

(1) Preparation of glass powder Examples N [11 to N017 and
For Comparative Examples Nos. 1 to 016, oxides of each composition were precisely weighed using a digital balance, and used as each raw material.

First, the raw materials are mixed in a Raikai machine for 1.5 to 2 hours, and after mixing, the raw material powder is placed in a platinum crucible, and heated to 1350 in an electric furnace.
Melt at ~1450°C for 1-2 hours. Stir the molten glass several times with a platinum rod during the process to improve the homogeneity of the glass, and when the glass is sufficiently clarified, pour the glass onto a carbon plate.
While the glass is still reddish, it is held at 700°C and then placed in an electric furnace to slowly cool it.

To measure the coefficient of thermal expansion of glass, this slowly cooled bubble-free glass is cut out and used.

Coarsely grind the glass cooled to room temperature in an agate mortar, add an appropriate amount of ethyl alcohol or an organic solvent such as isopropanol in a zirconia ball mill, and grind at 100 rpm.
pn, wet milling for 72 hours.

The slurry-like suspension after mixing is transferred to a container, and the organic solvent is evaporated in a drying oven at a temperature of 60 to 120''C to obtain a dried glass powder.

(2) Creation of paste and creation of evaluation samples Pyrochlore-type conductive particles with an average particle size of 0.05 μm and average particle size 2
Glass powder of various compositions with a weight ratio of 25 near 5
Each was weighed accurately, 30% by weight of ethyl cellulose was added as an organic vehicle, and thoroughly kneaded in a three-roll mill to obtain a resistance paste.

This prepared resistor paste is used as a screen pattern lX1.
It was coated on a 96% alumina substrate using a screen printing method using a screen with several mrr holes, dried in an electric furnace at a maximum temperature of 150°C, and then heated to a peak temperature of 8 in an air atmosphere belt furnace.
Baking was performed at 50°C for a peak time of 9 minutes to obtain a fired thick film.
It was used as an evaluation sample.

Note that the average thickness of the fired thick film was 8 to 10 μm. In addition, high-precision x-ray diffraction analysis has confirmed that the pyrochlore-type conductive particles as composite oxides of all the glasses tested are not decomposed by the high-temperature glass flow during firing.

(3) Evaluation method of WJ strength The following evaluation method was selected to evaluate the toughness of a thick film resistor fired on an alumina substrate using an indenter of a Pinkers hardness tester.

A Vickers indenter with a load of 500 g was gently applied to the surface of the thick film resistor and held for 15 seconds to form a square pyramidal indentation, and the presence or absence of crack damage was observed from the concave ridges of the square surface.

Incidentally, the toughness strength ratio was expressed as shown in Equation 1, and the crank occurrence rate (χ) was evaluated using this.

Toughness strength ratio - (number of samples with crack damage) / (total number of measured samples)
If this crack occurrence rate is within 10 to 20%, it can be said from experience that it is effective in improving the laser resistance of the fired product.

The above results are shown in Table 1.

〔Effect of the invention〕

As described in detail above, according to the present invention, a composition for forming a resistive film having excellent toughness and strength can be obtained as shown in the Examples.

Claims (1)

[Claims] A composition for forming a resistive film containing pyrochlore type conductive particles and glass powder containing 1 to 10% by weight of germanium oxide.