JPH0225241B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resistive material and a resistor made from a resistive material. More particularly, the present invention relates to a vitreous enamel resistive material that provides a resistor with high resistivity and durable or desirable physical properties, and is manufactured from relatively inexpensive materials. The types of electrically resistive materials used commercially are:
A vitreous enamel resistance material consisting of a mixture of glass frit and finely divided particles of electrically conductive material. Vitreous enamel resistance material, electrical insulation material,
It is usually coated onto the surface of a ceramic substrate and baked to soften the glass frit. Upon cooling, a glass film is provided with conductive particles dispersed therein. Since electrical resistors with a wide range of resistance values are desirable, there is a need for vitreous enamel resistive materials with respective properties that allow resistors with a wide range of resistance values to be fabricated. Resistive materials that provide high resistivity generally utilize noble metals as conductive particles and are therefore relatively expensive. However, recently, relatively inexpensive vitreous enamel resistance materials have been provided using tin oxide (SnO ₂ ). Oxides and additives have also been utilized to produce vitreous enamel resistive materials and resistors, and U.S. Pat.
No. 4065743, "Resistance material, resistor produced therefrom, and manufacturing method thereof" uses tantalum oxide (Ta ₂ O ₅ ) and tin oxide (SnO ₂ ) as additives.
A vitreous enamel material utilizing a conductive phase is disclosed. When utilizing a vitreous enamel resistive material with a conductive phase of tin oxide (SnO ₂ ) or a conductive phase of tin oxide and an additive, e.g. tantalum oxide (Ta ₂ O ₅ ), the resistivity of the material is is increased by decreasing the proportion of Glass capacity is 20
% ~ 80%, and the corresponding capacity of conductive material is 80% ~
It is 20%. However, the preferred range of tin oxide content is 40-60% by volume. Conductive phase content is 40% by volume
If the glass content decreases below and the glass content correspondingly increases above 60% by volume, the glaze will expand and become very foamy when the material is baked to produce the resistor. The glaze material in this type of situation has a large thickness, thereby providing a resistive layer that causes distortion and is weakened, easily cut and destroyed. Because of this difficulty, resistors are made with a glass content with an upper limit of 60% by volume, preferably less than 50% by volume. This limits the applications of this type of material and the ability to provide resistors with the large resistivities that would be provided by the use of high glass contents. In the art of making vitreous enamel resistive materials, increasing the temperature at which the vitreous enamel material is baked when making the resistor often imparts or increases desirable electrical properties of the resistor, such as its temperature stability. It has been found that However, increasing the bake temperature usually simultaneously decreases the resistivity of the resistor. It has therefore been found that in order to produce a resistor with the desired resistivity, it is necessary to increase the glass content sufficiently to account for the decrease in resistivity resulting from baking of the resistive material at high temperatures. It was. However, as mentioned above, the glass content of this type of resistor is limited to 60 volume %, preferably 50
It is expressed as capacity %. It is therefore an object of the present invention to provide a new and improved resistance material and a resistor made therefrom. Another object of the present invention is to provide a new and improved vitreous enamel resistive material and resistors made therefrom. Another object of the present invention is to provide a new and improved vitreous enamel resistance material having a tin oxide and tantalum oxide conductive phase and having relatively high resistivity and desirable physical properties. Another object of the present invention is to provide a new and improved vitreous enamel resistance material that produces a resistivity that is relatively insensitive to changes in baking temperature during the manufacturing process. Another object of the present invention is to provide a new and improved vitreous enamel resistance material that allows firing temperatures to be increased to optimal values while providing relatively high resistivity as well as desirable physical properties. Other purposes will become apparent from the description below. These objects consist of a borosilicate alkaline earth metal glass frit, an insulating material containing an oxide of zirconium, and a conductive phase mixture of finely divided particles of tin oxide (SnO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). , the glass and insulating materials are achieved by the resistive material being present in an amount up to about 70% by volume of the total resistive material. The insulating material is selected from the group consisting of zirconia ( _ZrO2 ), calcium zirconate ( _CaZrO3 ), barium zirconate ( _BaZrO3 ), and strontium zirconate ( _SrZrO3 ). Accordingly, the present invention relates to a composition and a resistor having the characteristics, constitution, and component relationships exemplified below. Generally, the vitreous enamel resistance material of the present invention consists of a mixture of a vitreous glass frit, an oxide-containing insulating material of zirconium, and a conductive phase of fine particles of tin oxide (SnO ₂ ). The conductive phase also includes the additive material tantalum oxide (Ta ₂ O ₅ ) taught in US Pat. No. 4,065,743. The glass frit can be present in the mixture in an amount of about 30 to about 60% by volume, preferably about 35 to 40% by volume. The insulating material can be an oxide of zirconium, such as zirconia (ZrO ₂ ), calcium zirconate (CaZrO ₃ ), zirconium, in an amount of up to about 15% by volume of the mixture, more if desired, preferably 10-15% by volume. barium acid (BaZrO ₃ ), and strontium zirconate (SrZrO ₃ ). The total content of glass frit and additives is preferably 50% by volume of the resistive material, although amounts as high as 60% and as much as 70% by volume can be used. The preferred amount of tin oxide (SnO ₂ ) is 40-60% by volume of the mixture, and if tantalum oxide (Ta ₂ O ₅ ) is utilized, the tin oxide (SnO ₂ ) comprises up to 50% by weight of the conductive phase. Add in quantity. The glass frit used may be selected from among the well-known compositions used to prepare glassy enamel resistor compositions having a melting point below the melting point of the conductive phase, particularly borosilicate alkaline earth metal frits, such as borosilicate. Barium acid frits or calcium borosilicate frits have been found to be preferred. The preparation of frits of this type is well known and consists, for example, in melting together the glass components in the form of their oxides and injecting the molten powder into water to form the frit. Of course, the batch ingredients are
Any compound that produces the desired oxide under normal frit manufacturing conditions may be used. For example, boron oxide is obtained from boric acid, silicon dioxide is produced from flint, and barium oxide is produced from barium carbonate. The coarse frit is reduced in particle size with water, preferably in a ball mill, to obtain a substantially uniformly sized frit. The resistive material of the present invention is prepared by thoroughly mixing together appropriate amounts of glass frit, insulating material, tin oxide particles, and tantalum oxide particles. In order to manufacture a resistor using the resistance material of the present invention,
Apply the oxidized material to the desired thickness on the surface of the substrate. Basically, any material that can withstand the baking temperature of the resistance material may be used. The substrate is generally an insulator, such as ceramic, glass, porcelain, cryostone, barium titanate, or alumina. The resistive material can be applied as a layer onto the substrate by brushing, dipping, spraying, or screen-type application. The substrate with the resistive material coating is then baked in a conventional furnace at a temperature below the point at which the glass frit softens but the tin oxide and tantalum oxide melt. The resistive material is preferably placed in an inert or non-oxidizing atmosphere,
For example, baking in argon, helium, or nitrogen. The particular baking temperature used will depend on the softening temperature of the particular glass frit used. As the substrate and resistive material cool, the vitreous enamel layer hardens and bonds the resistive material to the substrate. As shown in FIG. 1, the resistor of the present invention is generally designated as 10. The resistor 10 consists of a ceramic substrate 12 having a layer 14 of the resistive material of the present invention baked over thereon. The layer of resistive material 14 consists of a conductive phase of glass and insulating material 16 and finely divided particles of tin oxide (SnO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). Conductive phase particles 18 are embedded within the glass and insulating material 16 and dispersed throughout. In the following examples, embodiments of the present invention are examples, and other examples are provided for reference. Example A conductive phase consisting of 50% by volume of tin oxide (SnO ₂ ) was mixed with different amounts of glass frit and insulating material. Glass frit is BaO50% by weight,
It had a composition of 20% B ₂ O ₃ and 30% SiQ ₂ .
The insulating material used was zirconia (ZrO ₂ ). Several batches of resistive materials were prepared by mixing together the conductive phase, glass frit, and insulating material in the proportions indicated in the table. Each mixture was milled with butyl carbitol acetate in a ball mill to complete the mixture. The resistor composition was prepared by evaporating the butyl carbitol acetate and blending the mixture with squeegee media from L. Loisier & Company. Resistors were manufactured with each resistor composition by applying the composition in a screen mold onto a ceramic plate to which prefired copper terminals were applied. The resistors were then baked in a tunnel furnace with a nitrogen atmosphere at the peak temperatures indicated in the table for a 30 minute cycle. The resistivity of the obtained resistor is shown in the table and the graph in FIG.

[Table] Curve A in Figure 2 is the insulating material zirconia (ZrO ₂ ).
curves B and C represent the resistors of the present invention containing 10% and 15% by volume of zirconia (ZrO ₂ ). In curve A, the resistor baked at 950℃ has a high value of 345kΩ/square, and at the baking temperature of 1000℃
Reduced resistivity of 135kΩ/square and 77k when bake temperature increases to 1025°C
Indicates low resistivity of Ω/square. On the other hand, curve B is for a resistor baked at 950℃.
It shows a high resistivity of 1100 kΩ/square, and the resistivity increases to 1600 kΩ/square and 1700 kΩ/square for baking temperatures of 1000° C. and 1025° C., respectively. Curve C for a resistor with a large amount of zirconia has a higher resistivity,
That is, in the case of baking temperatures of 950° C. and 1000° C., the resistivities are 2600 kΩ/square, 3000 kΩ/square, and 2000 kΩ/square, respectively. The final resistivity is slightly higher than the resistivity of 1700 kΩ/square obtained at the given temperature for the resistor of curve B. In this way, the table and Figure 2 show that zirconia
When added to glaze compositions at 10-15% by volume,
It is shown that the resistivity of the resulting resistor is significantly increased compared to conventional tin oxide resistance materials without zirconia. The graph also shows that when adding an insulating material, increasing the baking temperature only changes the resistivity slightly, without reducing it as significantly as in the secondary material of curve A. . Thus, the addition of insulating material increased the resistivity of the resulting resistor and decreased its sensitivity to changes in baking temperature. In addition to relatively high resistivities, the resistors obtained in the examples did not swell, did not bubble, resisted cutting and breaking, and exhibited desirable physical properties. EXAMPLES Three batches of resistive compositions were prepared in the manner described in the Examples, but the insulating material was calcium zirconate (CaZrO ₃ ). Resistors were prepared from the resistor compositions in the manner described in the examples and resistors baked at the following peak temperatures gave the resistivities shown in the table. Resistors containing insulating materials provided increased resistivity, were relatively insensitive to increased bake temperatures, and had desirable physical properties.

【table】

Table: Examples Three batches of resistive compositions were prepared as described in the examples, but the insulating material was barium zirconate (BaZrO ₃ ). Resistors were prepared from the resistor compositions in the manner described in the examples and resistors baked at the following peak temperatures gave the resistivities shown in the table. Resistors containing insulating materials provided increased resistivity, were relatively insensitive to increased bake temperatures, and had desirable physical properties.

TABLE EXAMPLES Three batches of resistive compositions were prepared as described in the examples, but the insulating material was strontium zirconate (SrZrO ₃ ). Resistors were prepared from the resistor compositions in the manner described in the examples and resistors baked at the following peak temperatures gave the resistivities shown in the table. Resistors containing insulating materials provided increased resistivity, were relatively insensitive to increased bake temperatures, and had desirable physical properties.

[Table] Example Oxidation by mixing the oxides together in given volumes to give a batch of 90% tin oxide and 10% tantalum oxide and a batch of 75% tin oxide and 25% tantalum oxide. Two conductive phases were prepared: tin (SnO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). conductive phase
Batches of resistive compositions were prepared by mixing 50% by volume with glass frit and 50% by volume of insulating material in the proportions shown in the table. Resistors were manufactured in the manner described in the examples and resistors fired at the following peak temperatures gave the resistivities shown in the table. Resistors containing insulating materials were less sensitive to increased bake temperatures and had desirable physical properties.

【table】

Table 1 The above examples demonstrate the effect on the resistivity of the resistor of the present invention provided by adding an insulating material to a conventional resistor composition. in this way,
The example shows the addition of 10% by volume and 15% by volume of zirconia (ZrO ₂ ) to the composition of tin oxide glaze material, while the table shows the addition of 10% by volume and 15% by volume of zirconia (ZrO 2 ), while the table shows the addition of tin oxide resistance with tantalum oxide (Ta ₂ O ₅ ) as an additive. 2 shows the effect of insulating materials on the composition. Similarly, Tables, Tables and Tables show insulating materials, namely calcium zirconate (CaZrO ₃ ), barium zirconate (BaZrO ₃ ),
and strontium zirconate ( _SrZrO3 )
The effect on resistivity when each is added to a conventional tin oxide glaze composition is shown. Approximately 200kΩ/
Resistivity varying from sq to 1.3 MΩ/sq was obtained, and the glaze composition was heated to 950°C to
The effect of baking at a different temperature of 1025° C. is particularly evident in FIG. 2 when compared with the conventional tin oxide glaze material. Thus, the present invention produces tin oxide glaze-type resistors with high resistivities previously achieved only by increasing the glass content, which results in physical distortion and weakening of the resistor. Gives resistance material for. Also, an example is about 10-15% by volume of the mixture
demonstrate the effectiveness of adding zirconium oxide-containing insulating materials such as zirconia (ZrO ₂ ), calcium zirconate (CaZrO ₃ ), barium zirconate (BaZrO ₃ ), and strontium zirconate (SrZrO ₃ ) in amounts of .
In addition to providing higher resistivity to the tin oxide type glaze resistor, the additive stabilizes the resistivity achieved at the high baking temperatures used during the manufacture of the resistor. Since the influence of temperature changes during manufacturing is small, the resistivity of the resulting resistor can be better controlled. The maintenance of relatively high resistivity over a wide range of firing temperatures provided by the present invention makes it possible to maintain a relatively high resistivity over a wide range of firing temperatures. Allows selection of baking temperature. Additionally, the resistor of the present invention is made from relatively inexpensive materials. The foregoing is intended to be illustrative and non-limiting, as it is clear that the object has been efficiently achieved and certain modifications may be made without departing from the scope of the invention. It's not a thing.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a portion of a resistor manufactured using the resistive material of the present invention, and FIG. 2 shows the resistivity and baking temperature of the example resistor and resistors manufactured from conventional resistive materials. It is a graph showing the relationship between. DESCRIPTION OF SYMBOLS 10...Resistor, 12...Substrate, 14...Resistance material layer, 16...Glass and insulating material, 18
...Conductive phase particles.

Claims (1)

[Scope of Claims] 1 Consisting of a mixture of a borosilicate alkaline earth metal glass frit, an insulating material containing an oxide of zirconium, and a conductive phase of fine particles of tin oxide and tartaric oxide, wherein the glass and the insulating material have a resistance. Approx. of material
A vitreous enamel resistive material suitable for application to a substrate and baking to form an electrical resistor having relatively high resistivity and robust physical properties, characterized in that it is present in an amount of up to 70% by volume. 2. The vitreous enamel resistance material of claim 1, wherein the insulating material is selected from the group consisting of zirconia, calcium zirconate, barium zirconate, and strontium zirconate. 3. A vitreous enamel resistive material according to any one of claims 1 to 2, wherein the insulating material is present in an amount up to about 15% by volume of the mixture. 4. A vitreous enamel resistance material according to any one of claims 1 to 2, wherein the glass frit is present in an amount up to about 50% by volume of the mixture. 5 The glass frit and the insulating material are approximately
A vitreous enamel resistive material according to any of claims 1 to 2, wherein the vitreous enamel resistive material is present in an amount of 50% by volume and the insulating material is present in an amount up to about 15% by volume of the mixture. 6 consisting of an insulating substrate and a layer of resistive material on the surface of the substrate, the resistive material being embedded in and dispersed throughout a borosilicate alkaline earth metal glass containing an oxide-containing insulating material of zirconium; The glass and insulating material contains a conductive phase of tin oxide and tantalum oxide particles, characterized by a relatively high resistivity and robust physical properties characterized by the presence of up to about 70% by volume of the resistive material. Electrical resistor with. 7. The electrical resistor of claim 6, wherein the insulating material is selected from the group consisting of zirconia, calcium zirconate, barium zirconate, and strontium zirconate. 8. An electrical resistor according to any of claims 6 to 7, wherein the insulating material is present in an amount up to about 15% by volume of the mixture. 9. The electrical resistor of any of claims 6 to 7, wherein the conductive phase is present in an amount up to about 50% by volume of the mixture. 10. The glass frit and the insulating material are present in an amount of about 50% by volume of the mixture, and the insulating material is present in an amount up to about 15% by volume of the mixture. electrical resistor.