JPH05113394A - Analysis of distribution state of conductive substance in glass region of thick film resistor - Google Patents

Abstract

PURPOSE:To obtain a key elucidating the relation between the kind or amount and resistance value or CTR of the conductive powder compounded with resistance paste forming a thick film resistor. CONSTITUTION:In the analysis of the distribution state of the conductive substance in the glass region of a thick film resistor, a mixture of glass frit containing 2-25wt.% of a conductive powder with a particle size of 0.2mum or more and org. vehicle is printed on a ceramic substrate and baked to form the thick film resistor on the ceramic substrate. A sample having the thick film resistor is formed from the obtained substrate and the part only of the thick film resistor with a thickness of 100mum or less is formed from the sample to be observed by a transmission type electron microscope. Energy dispersion type X-ray spectra at a plurality of different distances from a predetermined position are calculated along the line traversing the glass region of the thick film resistor and the same component quantities in the respective spectra are plotted in the order of distances to form a graph.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analysis method for estimating a distribution state of a conductive substance in a glass region of a chip resistor or a thick film resistor used as a resistance element of a hybrid IC.

[0002]

2. Description of the Related Art A resistance paste material used as a resistance element of an electric circuit is a paste formed by kneading a conductive powder and an insulating glass powder with an organic vehicle. This paste material is screen-printed on the substrate material, then heated and baked to remove the organic vehicle and melt the glass component, and a thick film resistor containing conductive powder in the glass matrix is fixedly formed on the substrate. Let

By the way, as the conductive powder used for the resistance paste, ruthenium oxide (RuO ₂ ) or pyrochlore type Ru oxide is usually used. For high resistance, SnO ₂ is used in a nitrogen atmosphere. LaB ₆ or TaN is also used for firing. When a resistance paste using such a conductive powder is fired, an extremely small amount of the conductive substance that constitutes the conductive powder is dissolved and diffused in the glass, and this mediates electrons to conduct the entire resistor. It is said to play an important part of the path.

The case where a Ru compound is used as a conductor will be explained as an example. During the firing, the Ru compound is partially reduced to Ru during firing, and is further oxidized again to R.
It becomes uO ₂ , RuO ₃ , RuO _4, etc., and part of it dissolves in the glass. The amount of Ru dissolved in glass is extremely small, from several ppm to several hundred ppm, and its form is still unknown. Then, a small amount of Ru dissolved in the glass mediates electric conduction. Therefore, it is said that the electrical characteristics of the thick film resistor are closely related to the conductive substance dissolved in the glass. And various studies have been made to clarify this relationship. One of them is the measurement of the amount of Ru in glass.

As a means for measuring the amount of Ru dissolved in glass, there are methods 1) and 2) of Best et al. 1) A. Prabhu, GLFuller and RWVest, “Solubility
of RuO ₂ in a lead−bor-osilicate glass ", J.Am.Cera
m.Soc., Vol.57, pp.408-409 (1974) 2) P.Palanisamy, DHR Sarma and RWVest, “Solu
bility of ruthenium di-oxide in lead borosilicate
glasses ", J.Am.Ceram.Soc., Vol.72, pp.1755-6 (1989)

These methods are wet analysis methods, in which a mixed fired product of glass and a Ru compound is dissolved with hydrochloric acid or hydrofluoric acid,
The insoluble matter is removed, and the Ru amount in the obtained solution is determined by an atomic absorption method or plasma spectroscopy. However, this method is based on the assumption that the form of Ru in glass is acid-soluble, and that the conductive substances such as RuO ₂ and Pb ₂ Ru ₂ O _7-x are insoluble in the hydrochloric acid and hydrofluoric acid used. However, it is doubtful whether the obtained value is truly the amount of Ru dissolved in glass. Moreover, even if this assumption is correct, it is clear that the obtained value is only an average value.

What is needed to improve the electrical characteristics of the thick film resistor is not only the average amount of Ru dissolved in the glass, but also the elucidation of the distribution and diffusion state of Ru in the glass region. It is considered to be one of the clues to clarify the mechanism. However, a means for clarifying such distribution and diffusion state has not been disclosed yet.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a clue for clarifying the relationship between the resistance value and CTR, and the kind and amount of conductive powder blended in a resistance paste for making a thick film resistor.

[0009]

According to the method of the present invention for solving the above-mentioned problems, a conductive powder having a particle diameter of 0.2 μm or more is added to 2 to 2 particles.
A mixture of glass frit containing 5% by weight and an organic vehicle is printed on a ceramic substrate and fired to form a thick film resistor on the ceramic substrate, and a sample having a thick film resistor is prepared from the obtained substrate. The thickness of the sample is 100 nm
The following thick film resistor only portion is formed to obtain the thickness 100
The portion of the thick film resistor having a thickness of nm or less is observed with a transmission electron microscope to obtain energy dispersive X-ray spectra at a plurality of different distances from a predetermined position along a line crossing the glass region in the thick film resistor. This is to plot the same component amount in the spectrum in the order of increasing and decreasing distances and obtain the distribution state of the conductive material in the glass region of the thick film resistor as a graph.

[0010]

In the present invention, the particle size of the conductive powder is 0.2 μm.
If the particle size is smaller than m, the particle size approaches the size of the X-ray excitation region and the conductive powder makes it difficult to set the position of the measurement point in the glass region. This is because the conductive powder is finely dispersed in the glass and it becomes difficult to find the glass region in which the conductive powder does not exist in the X-ray excitation region.

The mixing ratio of the conductive powder to the glass frit is set to 2 to 25% by weight (hereinafter referred to as "%") because the content of the conductive substance dissolved in the glass region is less than 2%. This is because the amount becomes extremely small and falls within the error of the count number of the energy dispersive X-ray spectroscopic spectrum, and it becomes difficult to know the content. When it exceeds 25%, the conductive powder becomes too much and it is difficult to find a sufficiently wide glass region. Because it will be. The thickness of the portion to be inspected is set to 100 nm or less because otherwise the electron beam does not pass through the sample.

The substrate to be used is not particularly limited, but it is preferable that the substrate components do not diffuse into the glass, and it is preferable to use a beryllia substrate or a platinum foil in addition to the alumina substrate. The present invention will be further described below with reference to examples.

[0013]

EXAMPLE High-purity PbO 59.8 parts by weight, SiO ₂ 2
5.2 parts by weight, 9.7 parts by weight of B ₂ O _{3 and} 5.3 parts by weight of Al ₂ O ₃ were mixed using a rye crusher, charged into a platinum crucible and heated to 1200 ° C. in an electric furnace. Melted, held at that temperature for 30 minutes, then poured into a graphite mold, quenched, ground with a stamp mill and then ground with a ball mill to make 50 g of a glass frit with an average particle size of 2.54 μm.

RuO ₂ having a particle size of 1.0 μm or more was mixed as a conductive powder at a ratio of 10%, and terpineol and an organic vehicle containing ethyl cellulose as a main component were added and kneaded to obtain a resistor paste. It was This paste was printed on an alumina substrate to form a 15 mm × 15 mm paste applied portion. Put this substrate in an electric furnace and
The mixture was heated for 1 hour at 90 ° C. under aeration and then calcined at 900 ° C. for 1 hour.

After allowing the substrate to cool, a disc-shaped sample having a diameter of 3 mm was cut out using an ultrasonic disc cutter (Model 601 manufactured by Gatan Co., Ltd.), and the alumina substrate portion was polished and removed until the thickness of the alumina substrate became 10 to 100 μm. Then, the alumina substrate side was polished into a concave shape by a concave surface polishing machine (Model D500 manufactured by VCR), and the thickness of the thinnest recessed portion centering only the resistor portion was set to 10 μm. Then, using an ion polisher (JIT-100 manufactured by JEOL Ltd.), Ar ions accelerated at 4 kv were tilted at 15 ° with respect to the center line of the recess to irradiate the sample to make a small hole, and 100 nm was formed around the hole. A resistor portion having the following thickness was created.

The above sample was observed using a transmission electron microscope (JEM-2000EX, manufactured by JEOL Ltd.) equipped with an energy dispersive X-ray spectrometer (TN-2000-5, manufactured by Traykernozan Co., Ltd.), and RuO ₂ was observed in the visual field. The particles and the glass region in the vicinity thereof are put in, and the boundary between the RuO ₂ particles and the glass region is used as a starting point,
Energy dispersive X-ray (EDX) spectra were measured at each position along the straight line crossing the boundary using electron beams with a beam width of 8 mm at several different distances from the origin.

FIG. 2 shows an energy dispersive X-ray (EDX) spectrum diagram at a position moved 2288Å into the RuO ₂ particle from the boundary between the RuO ₂ particle and the glass region. In addition, from the boundary between the RuO ₂ particles and the glass region, 2
Figure 3 shows the EDX spectrum at the position where 065Å moved.
Similarly, FIG. 4 shows an EDX spectrum diagram at the same position moved by 5548Å. FIG. 1 is a graph obtained by plotting the content of each component according to the distance from the EDX spectrum diagram at a large number of positions thus obtained and connecting the plot points with a line.

From FIG. 1, the concentration of Ru changes more than the statistical error of the X-ray count number and the error caused by the change of thickness, and therefore, the concentration of Ru does not simply diffuse.
It suggests that they may exist like clusters of metal particles. By creating such a graph, it is possible to know not only what is present in the glass region as a metal, but also the distribution of conductive oxides in the glass region. It can be used as a clue to clarify the relationship between the kind and amount of the conductive powder and the resistance value or CTR.

[0019]

According to the method of the present invention, it is possible to estimate the distribution and the distribution form of the conductive substance in the glass region, which could not be known in the past.
It can be used as a clue to elucidate the relationship between the resistance value and CTR and the type and amount of the conductive powder compounded in the resistance paste.

[Brief description of drawings]

FIG. 1 is a graph in which the content of each component is plotted according to the distance from an energy dispersive X-ray spectrum diagram at a number of positions, and the plot points are connected by lines.

[2] from the boundary of the RuO ₂ particles and the glass area, RuO ₂
The energy dispersive X-ray spectrum diagram in the position which moved 2288Å in the particle is shown.

FIG. 3 is an energy dispersive X at a position moved 2065Å from the boundary between the RuO ₂ particles and the glass region to the glass region.
A line spectrum diagram is shown.

FIG. 4 is an energy dispersive X at a position moved from the boundary between the RuO ₂ particle and the glass region to the glass region by 5548Å.
A line spectrum diagram is shown.

Claims (1)

[Claims] 1. A conductive powder having a particle size of 0.2 μm or more
A mixture of glass frit containing 25% by weight and an organic vehicle is printed on a ceramic substrate and baked to form a thick film resistor on the ceramic substrate, and a sample having a thick film resistor is prepared from the obtained substrate. The thickness of the sample is 100 n
A thick film resistor only having a thickness of 10 m or less is formed to have a thickness of 10
The thick film resistor portion of 0 nm or less is observed with a transmission electron microscope, and energy dispersive X-ray spectra are obtained at a plurality of different distances from a predetermined position along a line crossing the glass region in the thick film resistor. A method for analyzing the distribution state of a conductive substance in the glass region of a thick film resistor by plotting the same component amounts in the spectrum in order of increasing and decreasing distances.