DE1193582B - Process for the production of electrical resistance layers - Google Patents

Description

Process for the production of electrical resistance layers The The invention relates to a method for the production of electrical resistance layers, those made of a fused onto an insulating support body, with conductive Metal oxides offset glaze layer exist as an aqueous slurry of conductive particles and glass applied to the support body, dried and fired will.

The electrical resistance layers given above relate to to resistors, which are described below. It must be stated here, that the term "electrical resistance layer" does not refer to so-called precision resistors is limited, the z. B. in radio equipment, wireless telegraphy equipment, electronic or other electrical devices, but it also closes electric heating elements and devices for conducting or transmitting electric Invitations.

It is known to produce resistors in which the resistor mass as a surface layer made of one interspersed with conductor or semiconductor particles Glaze is applied to the insulating substrate. It is stated to be a mixture of Glass enamel and finely divided metal, conductive metal oxide, especially iron oxide or metalloid, such as carbon or carbonaceous particles, as an aqueous solution to be applied to the support body, to be dried and burned in at more than 700 ° C. According to this known method, resistors with a high ohmic value can can be produced, but the disclosed teaching is not suitable to use resistors to produce reproducible and largely stable resistance values.

It is also known an electrical resistor that consists of a body consists of insulating material and provided with an electrically conductive layer containing oxides of tin, antimony or boron. The proportion of antimony, expressed as antimony pentoxide, is more than 100 / "and the proportion of boron, expressed in boron oxide, is more than 2.5 ° / 0. Both percentages relate to the total weight of the electrically conductive layer, this layer being applied in the form of a film has a surface resistance of 1 to 10,000 ohms / cm2. Also is a method for the production of an electrical resistor known, the one Has body made of insulating material and provided with an electrically conductive layer which consists of oxides, the process applying under oxidizing conditions and describes an enamel layer that contains volatile or vaporous tin components, contains an antimony mixture and a boron mixture, and the layer on the resistor body baked in a melting furnace at a melting furnace temperature of 500 to 1000 ° C will. The conductive layer is applied in the form of a film, its surface resistance 1 to 10,000 ohms / cmL.

Another electrical resistor is known which has a body made of glazed material, preferably made of glass, ceramic material or similar insulating materials, and which is provided with an electrically conductive layer made of oxides of tin and boron, the resistance layer as a film. is applied, the surface resistance of which is 1 to 10,000 ohm / cm2. In addition, a method for producing an electrical resistor is known which has a body made of glazed material, preferably made of glass or ceramic material, and which is provided with an electrically conductive layer which consists of oxides. This process includes the application of a liquid top layer under oxidation conditions, which contains a volatile tin and boron mixture on the resistor body and forms a film in a melting furnace, the melting furnace temperature being 600 to 1000 ° C and the mentioned film having a surface resistance of 1 to 10,000 ohms / cm2.

Compared to these known methods, the method according to the invention allows reproducible production of resistance layers which on the one hand have an extremely high ohmic value, 10 'ohm / cm2 and higher up to 1013 ohm / cm2, and which on the other hand have a property that is particularly useful in resistors for Precision instruments are essential, namely that the temperature coefficient of these resistive layers is very low and in the range of about -0.1 to -0.15'C, in some cases even between -0.085 and -0.088'C.

The resistance layers according to the invention are also distinguished characterized by a very high durability. The load change after a 100 hour Operating time was only 0.05 to 20 / ,.

The invention is characterized in that a mixture of tin oxide, Antimony and / or boron oxide is used and the proportion by weight of tin oxide in the Range from 10 to 90 "/, is that the oxidic constituents melted together and the hardened melt is pulverized that the ground particles have a size less than 10 microns that the ground particles mixed with glass particles, melted and ground again after solidification, that the slurry is formed with these latter particles, that the stoving temperature the slurry corresponds to the melting temperature of the glass used at which the conductive particles are bound to the carrier body, and that the duration of the Annealing takes about 1 hour, avoiding sharp jumps in temperature and the annealing is carried out in a neutral or oxidizing atmosphere.

The resistive layer according to the present method includes a Dispersion of semiconducting tin oxide particles in a glass bed. This mass is not homogeneous, which is due to the nature of the raw materials from which it is made this mass is produced. The raw materials are the oxides of tin, antimony and / or boron. The tin oxide is highly refractory. However, it was found that it is heated in a crucible in the presence of antimony and / or boron oxides and then can be brought into a semiconducting state. The properties can be predetermined become after it has been brought into the semiconducting state, and dependent From these properties the material can be melted with the glass or with oxides so that a conductive mass is thereby formed. This mass is marked by the fact that the tin particles are dispersed in a glass bed and are essentially unchanged by the process of glass melting. The surface the particle is wetted with glass and as a result of this effect can be a certain degree can be accepted by solution, however, the tin oxide essentially by the Glass melting process is not attacked. The main difference of the procedure according to the known methods mentioned above, there is a deposit in those takes place in the gas phase, d. That is, the tin oxide results from the decomposition of Tin chloride in the form of a gas. The semiconducting layer of tin oxide is created from the effect that the antimony and / or boron oxide simultaneously from a gas phase be deposited. In this way the semiconducting properties of tin oxide become obtained at the moment the tin oxide is produced. That fact is the basic difference compared to the method according to the present invention, in which the tin oxide is converted into the semiconducting state by a process, that is completely different, d. that is, the process is carried out by diffusion into a solid material.

The product obtained by the method according to the invention, d. H. the resistive layer also differs in its shape in that im In the case of the known method, a homogeneous film of tin oxide with antimony and / or Boron oxide is obtained, which is uniformly dispersed in this. According to the present In the invention, grains of tin oxide containing antimony and / or boron oxide are obtained, which are dispersed in a glass bedding. The known method is films with a thickness of a few hundred to 10,000 angstroms, while according to According to the present invention, the layer is a few microns thick, that is 50,000 up to 500,000 angstroms.

Finally, it can also be stated that the temperature coefficient of the films of the two processes also deviates greatly from one another. The temperature coefficient of the film according to the known method has a size from zero to a few 100-10 -e either positive or negative, while the temperature coefficient of the resistive layer according to the present invention is purely negative in the range from 1000 to 2000-10-e.

It should be mentioned that the slurry with which the resistor body is covered, in addition, as a further component, one or more of the following oxides may contain: titanium oxide, aluminum oxide, beryllium oxide, magnesium oxide, silicon oxide, Zinc oxide, manganese oxide and cobalt oxide.

The flux, e.g. B. frosted glass, may be present in the slurry in an amount greater than 50 percent by weight, the percentages by weight being based on the total oxides present. The lower limit of the ratio of glass is that which is sufficient to cement the tin oxide and the other oxides firmly onto the surface of the substrate. This minimum amount depends, among other things, on the nature of the glass, the baking temperature and the degree of comminution. Under the most favorable conditions, an amount of approximately 100 % of the weight may be sufficient.

The nature of the glass used as the flux in the slurry is not particularly critical. Commercially available lead glass was found to be just as effective as a specially prepared borosilicate glass.

Glasses and similar materials that have been used are as follows: a commercial glass containing 56 parts by weight of silicon, 30 parts by weight Lead oxide, 5 parts by weight of soda, 7 parts by weight of potash and small amounts of Aluminum and magnesium. Another suitable commercial one Glass has the following composition: 54.25 parts by weight silicon, 22 parts by weight aluminum, 7.5 parts by weight of boric oxide, 13.25 parts by weight of calcium oxide, 3 parts by weight of barium oxide (all percentages by weight).

Another glass that was used was 88 parts by weight Silicon and 12 parts by weight of boron oxide.

Generally speaking, a refractory glass, e.g. B. a borosilicate glass, can be used when the resistance is at very high temperatures should be used while a lead glass is used with such resistors, which do not have to meet high temperature requirements.

The resistance body is composed of glazed or sintered inorganic material, which is preferably glass or a ceramic product.

The liquid in which the glass and the oxides are slurried is z. B. an aqueous or alcoholic agent that is a slurrying agent contains, e.g. B. if water is used, 0.5 weight percent can be used as the slurry Ammonium alginate can be used while using an industrial alcohol 5 percent by weight of rosin resin makes a suitable slurry.

The oxidic components of the resistive film become common melted, then the hardened melt is pulverized and the resulting Slurried mass.

The fineness to which the material to be slurried is ground is of some importance since it is necessary that the ground material remain in the slurry during its application to the resistor body, e.g. On the order of 1 to 10 microns. As a result, it is necessary that the milled particles pass through a sieve of 6400 to 14,400 mesh / cm2, but preferably through a sieve of 19,600 mesh / cm2. Advantageously, the pulverized oxide mixture should be sufficiently finely divided to pass through a mesh sieve of 19,600 meshes / cm- with a maximum of 10 % residue.

In the further development of the process, if necessary, electrical Apply contacts to the burned-in resistor. The electrical contacts can consist of sprayed-on material or electrolytically deposited material. The electrical contacts can also be attached to the resistor body by applying a suitable liquid slurry of silver oxide or another metallic oxide and heating this body to an appropriately high level Temperature.

The following examples illustrate the present invention without, however, limiting it. Example 1 An intimate mixture in the ratio of 94 g of pure tin oxide and 6 g of pure antimony tricoxide was formed by wet grinding these substances in a ball mill for 24 hours. The liquid that was used was industrial spirit, but water can and has been used, and any other suitable liquid may serve this purpose. The mixture was then dried at a suitable temperature to remove the industrial spirit. The powder was poured into a fire-resistant crucible provided with a lid and the whole was placed in an electrically heated melting furnace and heated at a peak temperature of 1300 ° C. for a period of 2 hours. The furnace atmosphere was oxidizing during this time. It was found that prior to this treatment the tin oxide and antimony trioxide and the mixture formed from them were white and essentially a non-conductor to electricity. After this treatment, the resulting powder was blue and a good electrical conductor. The powder thus prepared was re-ground in a ball mill for a period of 24 hours and dried after it was found to have been ground so finely that it met the condition that it passed through a sieve of about 19,600 mesh / cm 2. 100 g of this powder was added to 100 g of pulverized glass, and the state of crushing this glass was such that it passed through a sieve of about 19,600 mesh / cm 2. The mixture was then milled again for a period of 24 hours. This mixture was placed in a crucible and heated in an electric furnace to a temperature higher than 850 ° C. but not over 900 ° C. for a period of one hour. The enamel; The furnace atmosphere was oxidizing during this time. The mixture was then crushed in a mortar and ground until it passed through a 64 mesh / cm 'sieve. The resulting coarse powder was then placed in a mixing mill and 400 cc industrial spirit containing 5% of its weight of rosin resin was added and mixed for 24 hours until a very fine slurry or casting compound was formed.

This casting compound was applied to porcelain rods with a dimension of 6.3 - 50 mm applied by placing one end of the porcelain rod in a jig held and the rod was rotated axially at a few revolutions per second. While the rod was rotated, the casting compound with a spray gun attached to a compressed air line connected to a pressure of approximately 1.4 atmospheres was sprayed on. The thickness of the film applied to the rod was about 0.3mm. The film was dried, and after a few seconds after application it was firm enough for further treatment. The bars were in at their ends a gauge made of a nickel-chromium alloy clamped and in an electrical one heated melting furnace with a peak temperature of 300 ° C for the duration of one Heated hour, during which time the furnace atmosphere was oxidizing. In order to test the electrical properties of the resistor, a contact material was used of sprayed zinc applied to the ends of the rod and an electric Contact made by sliding on brass caps with soldered leads. The surface resistance of the film was 108 ohms / cm2 and varied only very little between the individual samples (3 - 10 'to 4 - 108 Ohm / cm2). the Temperature coefficients were -0.13 to -0.21'C (the load change was approximately 20 /, after 100 hours of operation with direct current with a voltage of about 500 volts). example 2 The preparation of the conductive tin oxide and antimony oxide powder except for the grinding, that it could pass a sieve with 19600 meshes / cm2 was carried out as in the example 1.

To 150 g of this powder, 50 g of powdered glass was added, and the fineness of the crushing of the glass was such that the powder passed through a sieve of 19,600 mesh / cm2 passed. The mixture was then placed in a ball mill ground for a period of 24 hours. The resulting mixture was placed in a crucible introduced and placed in an electric furnace at a temperature 'greater than 650 ° C, but not exceeding 700 ° C, heated for a period of one hour. The furnace atmosphere during this time was oxidizing. The mixture was then in broken up a mortar and crushed until it passed through a sieve with 64 meshes / cm " went through. The resulting coarse powder was placed in a mixer and with 400 cm3 of industrial spirit with an addition of 5 percent by weight added rosin and mixed for 24 hours to form a slurry or Produce casting compound. This casting compound was made on porcelain rods of the dimensions 6.3 - 50mm is applied by placing the rods at one end in a jig was held and rotated axially at a few revolutions per second. During this Rotation, the casting compound was sprayed on by a spray gun with an air pressure of about 1.4 kg / cm "; the thickness of the film coated on the bars was about 0.3mm. The film dried within a few seconds after application and was then firm enough for further treatment. The bars were then in the Clamped near their ends in a gauge made of a chrome-nickel alloy and in an electrically heated oven up to a peak temperature of 900 ° C for burned in for an hour. The furnace atmosphere during this process was an oxidizing one. To check the electrical properties of the resistor, A zinc sprayed contact material was applied to the ends of the rods and the electrical contact by sliding on brass caps with soldered on Lines made. The surface resistance of the film was 108 ohms / cm2 and showed only slight deviations in the individual samples (8-10b to 2-108 Ohm / cm $). The temperature coefficient was -0.12 to -0.15 ° C.

Example 3 The solid component of the casting compound layer was as prepared as follows: A mixture of 61.7 g of tin oxide, 21.3 g of antimony trioxide, 66 g a precipitated silica and 17 g of boric acid were placed in a mechanical mortar mixed for a period of 2 hours. The mixture was then placed in a crucible, which was provided with a lid, and the whole thing in one electric heated melting furnace and used up to a peak temperature of 1300 ° C for heated for a period of 2 hours. The furnace atmosphere was during this time oxidizing.

The resulting glazed material was removed from the crucible, broken into a mortar, and crushed until it passed through a 64 mesh / cm2 sieve. This coarse powder was then placed in a mixer mill and mixed with 300 cc of industrial spirit containing 5 % of its weight with rosin resin for a period of 24 hours until a slurry or casting compound was obtained.

This casting compound was placed on porcelain sticks measuring 6.3 - 50mm applied by placing the ends of the porcelain chopsticks in a jig clamped and rotated axially at a few revolutions per second. While The casting compound was sprayed onto the rotation of the rods with the aid of a spray gun, which worked at a pressure of 1.4 kg / cm2. The thickness of the applied layer was about 0.3 mm. The layer was dried within a few seconds application and was then firm enough for further treatment. The wands were clamped near their ends in a gauge made of a chromium-nickel alloy and in an electrically heated oven up to a peak temperature of 1100 ° C Burned in for a period of 10 minutes. The furnace atmosphere was during this An oxidizing time.

A contact material made of sprayed-on zinc was applied to the ends of the rods and contact was established by sliding on brass caps with soldered leads. The surface resistance was 8-108 ohm / cm2. The range of temperature coefficients was from -0.085 to -0.088'C. (The load change was 0.05 % after 100 hours of AC load at 2 watts.)

Claims (12)

Claims: 1. A process for the production of electrical resistance layers, which consist of a glaze layer melted onto an insulating carrier body, mixed with conductive metal oxides, which is applied as an aqueous suspension of conductive particles and glass to the carrier body, dried and fired, characterized by , if a mixture of tin oxide, antimony and / or boron oxide is used and the proportion by weight of tin oxide is in the range from 10 to 900 / , that the oxidic constituents are melted together and the hardened melt is pulverized so that the ground particles have one size which is smaller than 10 microns, that the ground particles and glass particles are mixed, melted and, after solidification, ground again, that the slurry is formed with these latter particles, that the baking temperature of the slurry corresponds to the melting temperature of the glass used at which the direct The particles are bound to the support body, and that the annealing takes about 1 hour, avoiding sharp jumps in temperature, and the annealing is carried out in a neutral or oxidizing atmosphere. 2. Process according to claim 1, characterized in that the metal oxide mixture is still also titanium oxide, aluminum oxide, beryllium oxide, magnesium oxide, silicon oxide, zinc oxide, Contains manganese oxide or cobalt oxide or a mixture of these oxides. 3. Procedure according to claim 1 or 2, characterized in that the flux is frosted glass. 4. The method according to claim 3, characterized in that the glass is a borosilicon or lead glass. 5. The method according to any one of claims 1 to 4, characterized in that that the insulating support body is composed of glass or a ceramic material is. 6. The method according to any one of claims 1 to 4, characterized in that the metal oxide mixture preferably contains 50 to 600 /, tin oxide. 7. Procedure according to any one of claims 1 to 6, characterized in that the pulverized Oxide mixture is sieved through a sieve of 19600 mesh / cm2, so that the constituents of the oxide mixture are on the order of 1 micron or less. B. procedure according to one of claims 1 to 7, characterized in that as a further stage electrical contacts are applied to the fired resistor. 9. Procedure according to claim 8, characterized in that the electrical contacts are made of sprayed-on or an electrolytically applied metal layer. 10. Method according to claim 8, characterized in that the electrical contacts are applied by a suitable slurry of silver oxide or oxide on the resistor body another metal is applied and the body at a suitably high temperature is heated. 11. The method according to any one of claims 1 to 10, characterized in, that the liquid that is neutral to the flux and the pulverized Oxide mixture is an aqueous or alcoholic agent that is a slurry agent contains. 12. VerfahrennachAnspruch2, characterized in that the pulverized Oxide mixture contains tin oxide, antimony oxide, boron trioxide and silicon oxide. Into consideration drawn publications German patent application St 2420 VIIId / 21e (announced on April 26, 1951); Austrian patent specification No. 137 832.