RU2537754C1 - Manufacturing method of temperature sensors and heat flow (versions) - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention refers to measurement equipment and can be used in aviation and space technology. Obtaining temperature sensor and heat flow may be implemented directly on model surface of various degree of curvature without cockles and damage of integrity of the model and physical process of flowing on model surface and gas flow. Sensors thermocouples are manufactured from chromel-constantan film by method of cathode sputtering in vacuum. As insulating foil between the model and thermocouple, between thermocouples, chosen is aluminium oxide. Upper surface of thermocouple is protected from oxidation by heat resisting insulating foil with width of 0.80-0.1 mcm. Width of coating with thermocouple outputs is 0.3-0.4 mcm. Coatings with outputs are formed through masks (from metal or polyimide film) and by method of electrography by "pencil" voltage of 6-10 V.

EFFECT: increasing functional capabilities of temperature sensors and heat flow.

2 cl, 3 dwg

Description

The invention relates to measuring equipment, in particular to the field of measuring high levels of temperature and heat flux in aviation and space technology.

A known method of manufacturing a temperature sensor. The temperature sensor is made of two dissimilar metal conductors A and B, interconnected by welding and forming a thermocouple. If the junctions are at different temperatures, then an electromotive force arises in the circuit, causing current. In a first approximation, thermopower is a linear function of the temperature difference. Thermocouples are connected to the external circuit using wires made of metal other than thermocouple materials A and B. Temperature sensitive elements (CE) are made of different metals, for example platinum-platinum rhodium, copper-nickel, nickel-platinum, etc. Both wires are interconnected by contact welding. Before welding, the ends of the thermocouple wires are cleaned by known methods. (Kurt, S. Lyon. Instruments for scientific research. M., Engineering, 1964, 2.1.4. Thermoelectric sensors. Thermocouples, thermocouples. S.154).

The disadvantage of this method of manufacturing the sensor is that when welding two metals it is difficult to obtain a homogeneous connection. Because of this, there is a large variation in sensitivity, even in one batch of sensors.

Closest to the proposed invention, the technical solution is the following method of manufacturing a pressure and temperature sensor [see RF patent №2145064, 7 G01L 9/12, G01K 7/34, 2000, author A.A. Ghazaryan].

The base of the sensor is formed by evaporation in vacuum from alumina. For use, copper and nickel are purified. The surface of the dielectric film in a vacuum is activated by a glow discharge. The sensitive elements of the thermocouple are formed through masks with a continuous layer of copper. Then, the method of electrical engraving form conclusions and plates. Plates are metallized to a thickness of 0.3-0.5 microns. Choose the metallization mode of the polyimide film in vacuum at a pressure of 1 · 10 ^-4 -10 ^-4 mm RT.article 0.18-0.2 min at a current of 230-240 mA. This method of manufacturing a pressure and temperature sensor allows you to create a sensor that simultaneously measures the temperature and pressure on the surface of the model without violating the integrity of the model and the physical flow processes.

The disadvantage of this method is the lack of coating quality of the metallized film, due to which “luminous” dots appear, leading to a low coating density, which reduces electrical conductivity.

The technical result of the invention is to expand the scope of the sensor in the temperature range from -269 ° C to 1000 ° C

The technical result is the deposition of metals and dielectrics on the surface of the test object in a multi-stage method of evaporation of metal (up to 300 ° C) in vacuum and cathodic deposition of metal (up to 1000 ° C). The SE of temperature and heat flux is formed from nickel-copper on the surface of the dielectric film (up to 300 ° C) and on the surface of the test object (model) from chromel-constantan (up to 1000 ° C). As dielectrics, a polyimide film up to 300 ° C and alumina up to 1000 ° C were selected.

1. The technical result in the first embodiment in the method of manufacturing temperature and heat flux sensors is achieved by the fact that the surfaces of the dielectric film are metallized in vacuum by nickel and copper, the dielectric is metallized with copper at a pressure of 10 ^-4 mm Hg, and the pressure is the chamber is 10 ^-4 mm Hg, and the upper and lower thermocouples are formed in this way, and on the surfaces of the dielectric film and on the model the plates with leads and side screens are formed by electric engraving, by turning The model, the upper and lower thermocouples are precipitated by insulating dielectric films of aluminum oxide, they form a sensor for low temperatures in the range (-269, 300 ° C), using a multi-stage method of evaporating metal in vacuum on the surface of a dielectric film, for example, a polyimide film, the film is subjected to heat treatment in steps, the number of processing steps is at least three at a temperature of 300, 360, 380 ° C, and accordingly with a time delay of 10, 5, 2 min, in the case of a model having a complex surface shape, on the model surface, deposition for example, polyamide-acid varnish with a thickness of at least 1 μm, imidization regimes of polyamide-acid varnish at a temperature of from 80 to 360 ° C, the number of cycles of at least ten with a duration of exposure of each cycle of 20 to 5; 2 min, then a nickel film 0.3-0.5 microns thick is applied to this film, they provide a stable characteristic of sensitive elements by accelerated aging, keeping them for 15-20 minutes, at a temperature higher than the working temperature of 1.2- 1.3 times, select the following parameters for controlling the evaporation of the metal in vacuum on the surface of the dielectric film:

- the distance from the spraying device to the model (substrate) 45-55 mm;

- spraying in argon at a pressure of 10 ^-3 MPa;

- power supplied to the spraying device - 200 watts.

2. The technical result in the second embodiment of the method of manufacturing a temperature and heat flux sensor is that on the surface of the model, the sensitive elements and conclusions are metallized in vacuum by nickel, nichrome, constantan through masks, the dielectric is metallized with copper at a pressure of 10 ^-4 mm Hg. when nickel plating dielectric withstand pressure in the chamber 10 ^-4 mmHg while formed on the surfaces of the dielectric film the upper and lower thermocouple on the surface model of the upper and lower thermocouple is deposited insulator ionic dielectric films of aluminum oxide, in which the formation of temperature and heat flux sensitive elements with leads for temperatures in the range of (-269, 1000 ° C) are carried out in stages on a model surface by vacuum in a vacuum by cathodic deposition, for which metal is deposited, then by varying the capacities in the range of 150-400 W supplied to the spraying device at a pressure of 0.1-1.0 Pa, the distance between the spraying device and the model is 50 mm; with a diameter of 200 mm; moreover, the formation of thermocouple plates, insulating films is also carried out with a pre-heated model at a temperature of 170-190 ° C, the first sensor plates formed by chromel are smoothed with nichrome metal to a smoothing film thickness of 0.8-1.2 μm, the upper thermocouple plates are protected from oxidation at high temperatures up to 1000 ° C, a protective insulating layer with a thickness of 0.8-1.2 microns, and determine the adhesion strength of each film of nickel, copper, constantan and nichrome by delaminating the soldered wire with the film, while ensuring The soldering from the dielectric film is continuous at a delamination force of 40-50 N / m, and cold junction thermocouples should be at a temperature of 0 ° C with melting ice in distilled water.

Figure 1 and figure 2 shows the design and individual nodes of the temperature sensor and heat flow, and figure 3 is a thermoelectric diagram of thermocouples (devices).

On model 1, in vacuum, an insulating film 2 is applied, side screens 3, 4, a second insulating film 5 and a protective film 6, the upper plates 7, 8 and the lower 9, 10 thermocouples. The plates 7, 9 have, individually, a common conclusion 11 (sec. BB). For each of the plates 8, 10, terminal 12 is formed separately. The terminals are connected in places a to d with an external thick wire outside the field of the physical flow process, i.e. as far as possible, the contact points of two compounds, internal and external, are hidden inside the model from the influence of operating temperature. Films 2, 5 are made of polyimide or aluminum oxide, plates 8, 10 with terminal 12 are made of nickel or chromel, 7, 9 are made with terminal 11 of copper or constantan through two masks. Side screens 3, 4 (section A-A) around the plates 9, 10 and 7, 8 can be formed by electric engraving, using an electric “pencil” of 6-10 V. The upper plates 7 are protected by a protective film 6 from oxidation. Figure 3, the thermoelectric circuit contains thermocouples with cold junction plates 13, 14, an electronic switch 15, potentiometric amplifiers 16, 17, indicator 18. The indicator is connected to thermocouples through potentiometric amplifiers 16, 17 using wires C, D made of metal, different from the material of thermocouples 7, 8, 9, 10, 13, 14. Thermocouples of cold junction 13, 14 are made similarly to thermocouples 7, 8, 9, 10, of the same design, technology, work in different places and conditions. Potentiometric amplifiers and an electronic switch are standard and widely known in the measurement technique.

The temperature and heat flow sensor operates as follows.

In figure 3, if the points a, b, c, ..., c are at the same temperature Θ _a , then the total thermopower of this circuit is zero. If the point is at a temperature Θ _c = Θ _a -ΔΘ, then a thermoEMF appears in the circuit, which is proportional to the temperature difference ΔΘ. If the temperature at point a is not equal to the temperature at point b, then thermoEMF occurs in the circuit. The current in the thermocouple circuit depends on its resistance, and the measurement will be correct if the circuit resistance does not change. A change in the temperature of the circuit wires affects the change in their resistance, which also leads to a measurement error. Errors caused by the flow of currents are eliminated when measuring the thermocouple EMF by the compensation method:

The temperature Θ _{from the} working junction s can be determined if the temperature Θ _a junction a , b, c ... is constant or changes. If the temperature of the junctions a , b, c .. is closer to the temperature Θ _s , then the task of maintaining the temperature of the junctions a , b, c .. will be difficult. In such cases, the two thermocouple wires are attached two wires a ', in' who go to the place where the comparison temperature Θ _ref junctions A ', B' is constant. Materials for the compensatory effect of the external connecting wires are chosen so that the emf of junctions a , b, c ... is negligible. Such extension compensation wires, made in the form of an insulated two-core cable, are available for all thermocouples that are practically used. For accurate operation, thermocouple junctions 13, 14 must be at 0 ° C with melting ice in distilled water. In some cases, junctions of thermocouples 13, 14 are kept at room temperature or in a thermostat with a temperature of 20-50 0 ° C. All functional tasks: calculation, management are carried out by the indicator according to a pre-compiled program.

, где λ - теплопроводность диэлектрической пленки толщиной d. ТермоЭДС напряжения измеряют между обкладками: верхними 7, 8 и нижними 9, 10 ЧЭ с выводами термопары аг, бг, вг.At the stage of the experiment, sensors formed on the surface of the studied object (model) or manufactured separately on the surface of the polyimide film are subjected to a short-term temperature action. Under the action of the heat flux Φ on the plates 7, 8, 9, 10 of the thermocouple cover on the upper surface of the dielectric film 5, the temperature θ _{1 is} measured, and on the lower film 2 the temperature θ _{2 is} measured (Fig. 1, section A-A), then the heat flux defined as $$F={\lambda }_{\mathrm{one}}\frac{{\theta }_{\mathrm{one}}-{\theta }_2}{d}$$

where λ is the thermal conductivity of a dielectric film of thickness d. Thermoelectric voltage is measured between the plates: the upper 7, 8 and lower 9, 10 CE with the terminals of the thermocouple a g, bg, vg.

The principle of operation of the sensor with the SE of the temperature is based on the use of the thermoelectric effect arising in the connection of two metals of the two compounds nickel-copper (-269, 300 ° C) and chromel-constantan (-269, 1000 ° C). The SEs of temperature and heat flux are formed from plates 7, 8, 9, 10, 13, 14 of dielectric films 2, 5 and terminals 11, 12. In the heat flux F, the surface of the sensors through the protective film 6, thermocouples 7, 8 and 9, 10 s film 5 of thickness d between them are exposed to the action of temperatures θ ₁ and θ ₂ . The heat flux depends on the difference θ ₁ -θ ₂ , the thermal conductivity coefficient λ and the thickness d of the film 5, i.e. Ф = f (θ ₁ , θ ₂ , λ, d).

The need for development is caused by the increasing need for highly sensitive high-temperature sensors, which allow to study the temperature and heat flux fields on streamlined surfaces without the use of drainage, i.e. without violating the integrity of the model structure and the physical flow process. Based on well-known research and measurement techniques, two metals nickel-copper, chromel-constantan and others with the maximum possible thermoelectric effect should be chosen.

To solve the problem, films of metals and dielectrics are applied in vacuum. To increase the sensitivity of film thermocouples with plates 7, 8, 9, 10 and thermocouples 13, 14, the method of their manufacture and the choice of alloy grade are determined.

The technical result is achieved in two ways:

In the first embodiment, a sensor is formed for low and moderate temperatures (-269, 300 ° C) in a multi-stage way by evaporation of metals in vacuum on the surface of a dielectric, for example, a polyimide film, by conducting the following process cycles:

Stage 1. To obtain the basis of non-shrink sensors, films of polyimide 2, 5 with a thickness of d are subjected to stepwise heat treatment, the number of steps is at least three at temperatures of 300, 360, 380 ° C and, accordingly, with a time delay of 10, 5, 2 minutes.

2 stage. In the case of using model 1, having a complex profile surface, where it is difficult to stick a dielectric film on a curved surface without wrinkles, it is proposed to form (deposit) a polyimide 2, 5 dielectric film on the surface of model 1, for example, from a polyamide-acid varnish with a thickness of at least 1 μm. The imidization modes of polyamic acid varnish at a temperature of 80 to 360 ° C with a duration of soaking of the temperature of each cycle from 20 to 2 minutes, the number of cycles at least 10.

3 stage. Preparation of raw materials. In this step, the surface of the polyimide film is cleaned with ethyl alcohol. Also subjected to purification of copper, nickel, nichrome, chromel, constantan, intended for metallization of a polyimide film or other dielectric films.

4th stage. To increase the adhesion strength between the metal and the dielectric film, for example, a polyimide film, the surface of the dielectric is activated by a glow discharge in vacuum. Create a vacuum of 5 · 10 ^-1 -8 · 10 ^-1 mm RT.article with a duration of 0.25-0.3 min with a current strength of 550-600 mA.

5 stage. To form a SE of a temperature sensor on the surface of a polyimide film 5 of thickness d with plates 7, 8 of nickel-copper in a vacuum, a chromium film 0.1 μm thick is first applied. Then a nickel film, i.e. plates 8, 9 with a thickness of 0.3-0.5 microns. Nickel film through masks is applied to the surface of a dielectric film (polyimide film), preheated to 175-185 ° C. When metallizing films with nickel, they withstand pressure in the chamber · 10 ^-4 mm Hg, with a current strength of 230-240 mA lasting 0.45-0.5 minutes Or, a polyimide film is metallized completely and a SE is formed with plates 7, 8, 9, 10 by electrical engraving. Copper films, i.e. plates 7, 10 with a thickness of 0.3-0.5 microns are applied second. Modes of copper metallization under vacuum of 10 ^-4 mm Hg are selected. with a duration of 0.18-0.2 min with a current strength of 230-240 mA. Moreover, to obtain a dense metal coating, a polyimide film (15–20 μm thick) is metallized in a tense state so that it becomes a membrane. The results of the experiment showed that the deposition of the first layer of a nickel film on the surface of the dielectric film is associated with the fragility of the nickel film, which can crack at the junction (transition) of the plates and copper and nickel leads.

6 stage. In order to increase the sensitivity and reliability of temperature and heat flux sensors, increase the thickness of nickel and copper films to 2 μm when measuring temperature in a wide range from - 269 to 300 ° C. In this mode, it is recommended to deposit nickel and copper on the surface of a dielectric, for example, polyimide, by cathodic deposition in a vacuum.

7th stage. Provide a stable characteristic of the formed SE by accelerated aging with a stepwise change in temperature, with a temperature higher than the working temperature by 1.2-1.3 times, lasting 15-20 minutes. Accelerated aging can provide stable stable characteristics of metal films, close to the characteristics of wires of large cross-section.

Select the parameters of cathodic deposition in vacuum on the surface of a dielectric, for example, a polyimide film:

- the distance from the deposition device (target) to the substrate (model) 45-55 mm;

- spraying in argon at a pressure of 10 ^-3 MPa;

- power supplied to the spraying device (target) 200 W, i.e. density 0.5 W / cm ² ;

- input power of a high frequency of 0.6 W / cm ² .

The duration of the spraying is adjusted in such a way as to provide the required thickness of the metal film from 0.1 to 2 μm depending on the thickness of the metal, from the distance to the axis of the target, with a target diameter of 200 mm.

In the second option, in the manufacture of temperature and heat flux sensors for low and high temperatures (-269, 1000 ° C), the sensor is formed on the model’s surface in stages in a vacuum, for which metal is deposited by cathodic deposition and the following technological cycles are observed:

Stage 1. Preparation of raw materials for assembly. In this process, the surface of Model 1 is cleaned with ethyl alcohol. Chromel and constantan are also purified, which are used to form thermocouple plates 7, 8, 9, 10 and 13, 14.

2 stage. In vacuum, insulating films 2, 5 of aluminum oxide are formed on the surface of model 1, then plates 7, 8 of chromel - constantan (Fig. 1, section A-A). In this case, the cathodic deposition device in vacuum is selected consisting of a radio frequency diode. The spraying modes of insulating films are selected by varying different powers of 150-400 W supplied to the spraying device (target) in the pressure range 0.1-1.0 Pa, the distance between the spraying device (target) and the model or substrate is 50 mm; diameter of the target (sputtering device) 200 m.

3 stage. The first plates of the thermocouple 8, 9 are formed through two masks (or by electrical engraving at a voltage of 6-10 V) from metal or from a polyimide film. Using a mask, chromel 0.2-0.3 microns thick is deposited in vacuum on the surfaces of insulating films 2, 5 in a vacuum. Choose spraying modes that match the modes in the second stage.

4th stage. The first (lower) plates of the thermocouple 8, 9, 14 with leads 12, deposited on the surface of the insulating films 2, 5, may contain defects "luminous dots". This defect is eliminated on the surface of the first plates 8, 9 with leads 12 by smoothing, for which they are deposited with nichrome with a thickness of 0.08-0.1 μm on the surface of the dielectric by cathodic deposition in vacuum using ion bombardment.

5 stage. The second (upper) plates of the thermocouple 7, 10, 13 are formed with terminal 11 on the surfaces of the first constantan plate 0.2 to 0.3 μm thick. At this stage, the selected modes for the formation of the second plates coincide with the mode of the fourth stage.

6 stage. To protect the upper lining of the thermocouple 7 from oxidation at high temperatures (during operation of the sensors at a temperature of 1000 ° C), the lining is covered with an insulating film 6 of a material that includes nickel, chromium, aluminum, etc. 0.08-0.1 microns thick.

7th stage. In order to improve the quality of two compounds made of a metal film of chromel-constantan, before forming thermocouple plates 7, 8, 9, 10, insulating films 2, 5 and model 1 are preheated to a temperature of 170-190 ° C.

8. Regardless of the temperature measurement range, the adhesion strength of insulation and metal films individually and between each other is determined using adhesive tape. Their separation from the insulating films on the model, from the surface of metal films of chromel and constantan and others according to MRTU No. 6-05-111-6-68. At the same time, an assessment was adopted: very poor adhesion - the coating is easily detached at the slightest deformation; very good - the coating does not separate from the substrate even after significant deformations. In addition, the adhesion of the metallized coating is determined by delamination of the soldered wire of normal soldering to the film of chromel, constantan, etc. The place of rations should be solid and not come off with a delamination force of 40-50 N / m. The wires used for the manufacture of thermocouples must be annealed at a temperature higher than the temperature that is measured. It is necessary that the wire be homogeneous, otherwise, if a temperature difference occurs along the wire, then spurious thermoEMF may appear.

The sensitivity of the thermocouple is increased by increasing the thickness of the plates and their formation by the method of cathodic deposition in vacuum. The temperature range extends to 1000 ° C through the use of temperature-resistant metals and insulating coatings in the construction of thermocouples. It is highly preferable that the sensor design is formed directly on the surfaces of thin profiles and models having surfaces of complex curvature.

To this end, TsAGI applied insulation films on surfaces of normal and complex curvature of polyimide 15–20 μm thick. The sensor plates were applied in vacuum through masks made of duralumin 0.8 mm thick or polyimide 120-130 microns thick.

при комнатной температуре. Например, при температуре 170-200°C температурный коэффициент металлизированной никелем полиимидной пленкиThe sensor plates are formed of nickel, copper 0.3-0.4 microns thick. Samples were kept at a temperature of 320 ° C for a short time and 200-250 ° C in continuous operation. After such a training, no external defects were found. It was found that the nickel-coated polyimide film has light-transmitting points much smaller than 0.1 nm in size. This is one of the reasons that, for given identical sizes, metal films have different ohmic (active) resistances. Other difficulties are the observance of obtaining the same film thickness from any metal. Based on these considerations, it is proposed that the first thermocouple plates be deposited with nichrome with a thickness of no more than ~ 0.1 μm. The obtained temperature coefficient of the metallized film of polyimide nickel is close to well-known $$N{i}_{l\mathrm{and}t}\alpha =6.7\cdot {10}^{-3}\frac{\mathrm{one}}{{}^{o}C}$$

at room temperature. For example, at a temperature of 170-200 ° C, the temperature coefficient of the nickel-metallized polyimide film

. $${\alpha }_{Ni170-{200}^{o}C}=2,3\cdot {10}^{-3}\frac{\mathrm{one}}{{}^{o}C}$$

.

It is known that a polyimide film retains flexibility at the temperature of liquid helium (4 Kelvin) and after exposure to liquid nitrogen. Under these conditions, it can be wound on a rod with a diameter of 6 mm, and the film does not break and does not crack.

Claims (2)

1. A method of manufacturing temperature and heat flux sensors, based on the fact that the surfaces of the dielectric film are metallized in vacuum by nickel and copper, the dielectric is metallized with copper at a pressure of 10 ^-4 mm Hg, and when the dielectric is metallized, the pressure is kept in the chamber 10 ^-4 mmHg. and form upper and lower thermocouples in this way, on the surfaces of the dielectric film and on the model, plates with leads and side screens are formed by electric engraving, and on the surfaces of the model, upper and lower thermocouples, insulating dielectric films of aluminum oxide are deposited, characterized in that they form a sensor for low temperatures in the range - 269 ÷ 300 ° C in a multi-stage method of evaporation of metals in vacuum on the surface of a dielectric film, for example, a polyimide film, this film is subjected to temperatures stepwise processing, the number of processing steps at least three at a temperature of 300, 360, 380 ° C and, accordingly, with a time delay of 10, 5, 2 min, in the case of a model having a complex surface shape, for example, polyamide-acid varnish is deposited with a thickness of not less than 1 micron, imidization modes of polyamide-acid varnish are carried out at a temperature of from 80 to 360 ° C, the number of cycles is not less than ten with a duration of soaking of each cycle from 20 to 5; 2 min, then a nickel film 0.3-0.5 microns thick is applied to this film, they provide a stable characteristic of sensitive elements by accelerated aging, keeping them for 15-20 minutes at a temperature higher than the working temperature of 1.2-1.3 times, select the following parameters for controlling the evaporation of the metal in vacuum on the surface of the dielectric film:
- the distance from the spraying device to the surface of the model is 45-55 mm;
- spraying in argon at a pressure of 10 ^-3 MPa;
- power supplied to the spraying device - 200 watts. 2. A method of manufacturing a temperature and heat flux sensor, which consists in the fact that on the surface of the model, sensitive elements and conclusions are metallized in vacuum, nickel, chromel, constantan through masks, a dielectric is metallized with copper at a pressure of 10 ^-4 mm Hg, with metallization nickel dielectric withstand pressure in the chamber 10 ^-4 mmHg while formed on the surfaces of the dielectric film the upper and lower thermocouple model surfaces, the upper and lower thermocouple deposited dielectric insulating film of oxides aluminum, characterized in that the formation of temperature and heat flux sensitive elements with leads for temperatures in the range of -269, 1000 ° C is carried out in stages in vacuum on a model surface by cathodic deposition, for which metal is deposited by varying the powers in the range of 150-400 W, supplied to the spraying device at a pressure of 0.1-1.0 Pa, with a distance between the spraying device and the model of 50 mm; moreover, the formation of thermocouple plates, insulating films is also carried out with a pre-heated model at a temperature of 170-190 ° C, the first sensor plates formed by chromel are smoothed with nichrome metal to a smoothing film thickness of 0.8-1.2 μm, the upper thermocouple plates are protected from oxidation at high temperatures up to 1000 ° C, a protective insulating layer with a thickness of 0.8-1.2 μm, then the adhesion strength of each film of nickel, copper, constantan and nichrome is determined by delamination of the soldered wire with the film, while ensuring The soldering point is separated from the dielectric film at a delamination force of 40–50 N / m, and the cold junction thermocouples are kept at 0 ° C with melting ice in distilled water.

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