SU809407A1 - Low-resistance precision fixed wire resistor - Google Patents

Description

(54) LOW-POWER PRECISON CONSTANT WIRE RESISTOR

The invention relates to electrical engineering and can be used in radio equipment.

Low-resistance precision constant wire resistors are known, whose resistance is adjusted to a predetermined nominal value by moving the string resistor element out of.

The disadvantages of this resistor are the low stability of the parameters and poor processability.

The closest in technical essence to the present invention is a low-resistance precision constant wire resistor, the contents of the dielectric substrate with filamentous reznostivnya and elements, on the ends of KOToj x are made of current leads C2D.

The disadvantage of this resistor is the low stability of the parameters due to increased sensitivity to humidity, as well as due to the insufficient accuracy of the fit carried out by varying the number of filaments in the beam.

The purpose of the invention is to increase the stability of the resistor parameters.

The goal is achieved by the fact that a low-impedance precision constant wire resistor containing a dielectric substrate with filamentous resistive elements, is fitted with current leads at the ends of the KOTOiKix, equipped with a conductive element in the form of a track at an angle to the filamentary parallel resistive elements and connecting a non-woven track. 5 resistive elements, the filamentary parallel resistive elements being made in the form of a cast microwire in glass insulation, and a dielectric substrate made of filament single parallel resistive elements impregnated with glass enamel and fastened with a plate made of a material with high thermal conductivity.

The drawing shows a low impedance precision constant wire resistor.

Nyeco-ohm precision constant wire resistor contains resistive threadlike elements 1. Consisting of 2 micron microwires in glass insulation, impregnated with a glass enamel 3 from parachute segments 2, made of glass microwire, contact nodes 5 are connected to the upper faces of the ends of 4 resistive elements . The glass enamel layer 3 fixes the resistive elements 1 on the plate 6 of a material with high thermal conductivity. At an angle to filamentary parallel resistive

Accuracy of fit,%

Nominal value, ohm

0.1-1.0 0.1-1.0 1.2-10.0 1.2-10.0 11.0-100.0 11.0-100.0

The manufactured resistors were subjected to three one-hour cycles in the temperature range from –B to –100 ° C, and then placed under load for 100 h at 70 ° C.

The care of the parameters of the resistors at the same time did not exceed 0.01%, and there were no failures.

Resistors were made of the same size: length 12 mm, width 8 mm thickness (with platform) -2.0-2.5 mm.

As resistive elements, cast microwires were used in glass insulation with a core of copper-based metal alloys (linear resistance 1–9 kΩ / m) and nickel-based (4–150 kΩ / m). The number of elements laid on the plate varied by row: 50 segments, 100 segments, 200 segments, 400 segments. It is impractical to lay more than 400 pieces, since when etching the insulation, the quality of etching decreases and the processing time increases, and when it is impregnated with enamel and subsequent heat treatment, bubbles appear (swell). The width of the lead element 7 in the form of a track was 1.5-2 mm, it was formed at a distance of 3-5 mm from one of the contact nodes at an angle of approximately 30 to the direction of the segments 2 and a length of 3 mm.

The technology of manufacturing low-resistance precision permanent wire resistors includes the following process sequence, which is optimal.

A cast microwire is wound onto a glass frame (made of glass with a TKR 4110) with a diameter of 80 mm in glass insulation (TCR with) Winding a series of 100 turns in a section (7 sections in total). The choice of frame for TCR is associated with the fact that under the influence of heat in the frame-winding system, considerable stresses occur, and the greater the difference in TCR,

the elements are placed conductive element 7 in the form of a track connecting at least 1/5 of the resistive elements.

Example. To determine the reliability and stability of a low-resistance precision constant wire resistor, 220 resistors were fabricated, the characteristics of which are listed in the table.

Pieces

43 72 36 20 22 27

the more these tensions are. The most dangerous for winding and insulating the wire are tensile stresses, since the strength of the glass insulation of a microwire (as well as glass in general) when stretched is 10-15 times lower than the compressive strength.

The coiled winding is impregnated in glass enamel 29 (TU-DKS No. 2-67). is a mixture of low-melting, boric-lead silicate with chromium and cobalt oxides, with a drop-forming temperature of 550 +.

After heat treatment, no disturbances were found in the insulation of the microwire (the temperature of the beginning of the insulation softening was 700–720 s) and the enamel flow (the full spreading temperature of the enamel was 715 + 15 s).

The winding is cut along the generatrix is removed from the frame (spontaneous delamination in the form of a bracelet, 30-60 µm thick) and placed on a plate from a covar (1.2-2 mg thick d notches, Kovar is selected from considerations of the high mechanical strength of its junctions with glass , the ability to adhere well to hard and soft springs, its good TCR matching with glass and cast microwire in glass insulation. The plate is preliminarily coated with glass-glass slurry No. 29 and winding is laid on its layer (wet).

The plate with the winding is heated (briefly for 1.5-2 minutes) to 600 ° C, cooled to room temperature and applied to the surface of the winding with a cap-varnish A protective coating against hydrofluoric acid is applied (35% solution of hydrofluoric acid, GOST 2567-54 ). The areas of future contact nodes (2-3 mm wide) and a conductive element in the form of a track (1.5-2 mm wide which are then etched in hydrofluoric acid for 5-7 minutes) remain uncovered.

After washing, strained parts are treated with PSR-45 solder (complete melting temperature 625 s), current leads are connected to the obtained contact nodes, and a microwire is broken off over the slots of the plate. Breaking the microwire over the slot is straightforward and does not lead to marriage, and the ends are easily cleaned.

For convenience, the cutting of the plate along the cutting line is carried out after adjusting the resistance of each resistive element to the nominal value with a given accuracy. The fit is performed by scalding with the help of a scalpel microwire. The presence of a conductive element in the form of a track made it possible to make the fit almost to within the limit limited by the accuracy of the measuring equipment, since it is possible to exclude microwire segments from the resistor circuit equal to the entire length of the resistive element and up to 1/5 of its length.

After fitting, the resistor is again covered with a thin layer of glass-enamel 29 and kept in an oven for 15–20 s. At the same time, no irreversible drag treatments and disturbances in the contact nodes were observed.

The proposed device improves the accuracy of the nominal values of resistances of non-coaxial precision permanent wire resistors, expanding the range of their nominal values at lower limits.

Formula and gain

A low impedance precision constant resistor, containing a dielectric substrate with filamentary resistive elements, at the ends of which current conductors are made, characterized by

5 that, in order to increase the stability of the parameters of the resistor, it is provided with a conducting element in the form of a track located at an angle to the filamentary parallel resistive elements.

0 and connecting at least 1/5 of the resistive elements, the filamentary parallel resistive elements being made in the form of a cast microwire in glass insulation, and the dielectric substrate is made of 5 visible parallel resistive elements impregnated with glass enamel and fastened with a plate of high thermal conductivity material.

Information sources,

0 taken into account in the examination

1. USSR author's certificate

No. 448484. Cl. H 01 G 4/40, 01.19.72.

2. The US patent is 3973234. cl. 338, 1963 (prototype).

Claims (2)

Claim A low-impedance precision constant * ^{and a} wire resistor containing a dielectric substrate with filamentary resistive elements, at the ends of which current leads are made, characterized in that 15, in order to increase the stability of the resistor parameters, it is equipped with a conductive element in the form of a track located at an angle to the filamentary parallel resistive elements 20 and connecting at least 1/5 of the resistive elements, and the filamentary parallel resistive elements are made in the form of a cast microwire in glass insulation, and the dielectric substrate is made of filamentary parallel resistive elements impregnated with glass enamel and fastened by a plate of a material with high thermal conductivity. __ Sources of information, ³⁰ taken into account during the examination 1. Copyright certificate of the USSR "448484, cl. H 01 G 4/40, 01/19/72. 2. US Patent L ”3973234, cl. 338, 1963 (prototype). 4 3.