CN111595463A - Split type Dewar cold platform with low contact thermal resistance and coupling stress isolation - Google Patents
Split type Dewar cold platform with low contact thermal resistance and coupling stress isolation Download PDFInfo
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- CN111595463A CN111595463A CN202010441675.5A CN202010441675A CN111595463A CN 111595463 A CN111595463 A CN 111595463A CN 202010441675 A CN202010441675 A CN 202010441675A CN 111595463 A CN111595463 A CN 111595463A
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- 230000008878 coupling Effects 0.000 title claims abstract description 65
- 238000010168 coupling process Methods 0.000 title claims abstract description 65
- 238000005859 coupling reaction Methods 0.000 title claims abstract description 65
- 238000002955 isolation Methods 0.000 title claims abstract description 52
- 238000012546 transfer Methods 0.000 claims abstract description 5
- 239000000463 material Substances 0.000 claims description 20
- 238000012545 processing Methods 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 8
- 238000005219 brazing Methods 0.000 claims description 6
- 239000000945 filler Substances 0.000 claims description 2
- 230000006978 adaptation Effects 0.000 abstract 1
- 238000001816 cooling Methods 0.000 abstract 1
- 238000013461 design Methods 0.000 description 10
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- 238000005057 refrigeration Methods 0.000 description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 229910000679 solder Inorganic materials 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000009713 electroplating Methods 0.000 description 4
- 239000004519 grease Substances 0.000 description 4
- 238000009434 installation Methods 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 238000005498 polishing Methods 0.000 description 4
- 238000004506 ultrasonic cleaning Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000003466 welding Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000003754 machining Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000012790 confirmation Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000005489 elastic deformation Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910052738 indium Inorganic materials 0.000 description 2
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 230000003071 parasitic effect Effects 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- NEIHULKJZQTQKJ-UHFFFAOYSA-N [Cu].[Ag] Chemical compound [Cu].[Ag] NEIHULKJZQTQKJ-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/0205—Mechanical elements; Supports for optical elements
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Abstract
The invention discloses a low-contact-thermal-resistance and coupling-stress-isolation split-type Dewar cold platform which is composed of a high-thermal-conductivity cold platform and a low-thermal-conductivity thin-wall cylindrical core column. According to the coupling characteristic of the detector and the cold finger of the refrigerator, the arc-shaped isolation groove with a certain shape is designed and processed on the cold platform, and the physical isolation of the heat conduction link and the coupling stress transfer channel is realized on the premise of ensuring that the heat transfer capacity required by a certain heat load is met. The invention can realize low contact thermal resistance of large cooling capacity transmitted on the split type Dewar cold platform, simultaneously avoid the influence of coupling stress generated by interference coupling on the detector, and simultaneously meet the requirement of the split type Dewar component on the severe space environment adaptation. The invention has the advantages of simple structure, convenient operation, good compatibility and high reliability. Can be applied to various split type Dewar components.
Description
Technical Field
The invention relates to an infrared detector Dewar assembly technology, in particular to a split Dewar cold platform with low contact thermal resistance and coupling stress isolation, which is suitable for split refrigeration type infrared detector Dewar packaging.
Background
The infrared detector Dewar component has wide application in the aerospace infrared field. With the wavelength expansion to long wave and the improvement of detection sensitivity, the infrared detector must work at a deep low temperature. Because the mechanical refrigeration has the advantages of compact structure, small volume, light weight, short refrigeration time, large adjustable range of refrigeration temperature and the like, the detection device of the type at present mostly adopts a mechanical refrigeration mode in application. Therefore, the infrared detector Dewar type refrigeration assembly is formed by adopting Dewar type packaging in most of the application.
In order to reduce the influence of stress generated in the process of coupling a refrigerator and a dewar of a split detector dewar assembly on a detector, an elastic cold chain structure or indium cushion non-compression coupling is adopted in the traditional method. Both of these ways reduce the effect of the cold finger on the detector at low temperatures by controlling the coupling force. When the parasitic thermal load of the split-type Dewar component is small, the coupled contact thermal resistance and temperature gradient are small, but when the split-type Dewar component is coupled, the requirements on the dimensional tolerance and the form and position tolerance of a Dewar cold platform and a cold finger of a refrigerator are high. With the increase of parasitic thermal load of the dewar assembly and the increase of joule heat of the detector (especially for large-area-array CTIA detector application), the thermal contact resistance and the temperature gradient of the dewar assembly, whether the elastic cold chain structure or the indium pad is not in compression coupling, are increased along with the increase of the thermal load, which can cause the increase of the cold power consumption of the refrigerator, thereby affecting the service life of the refrigeration assembly and even affecting the performance and reliability of the detector. In summary, for the dewar assembly of the split-type refrigeration infrared detector, under a large heat load, the effect of coupling contact thermal resistance on the detector is reduced and the effect of coupling stress on the detector is avoided. A new approach must be explored to address this problem.
Disclosure of Invention
The invention aims to provide a split type Dewar cold platform with low contact thermal resistance and coupling stress isolation, which reduces the contact thermal resistance by increasing coupling force on the premise of ensuring the heat flow transmission capacity required by heat load and avoids the influence of the coupling force of interference coupling on the performance of a detector.
The purpose of the invention is realized as follows: the split type Dewar cold platform with low contact thermal resistance and coupling stress isolation is shown in figure 1 and comprises a cold platform 1 and a core column 2, wherein the core column 2 is made of a low thermal conductivity material, has a thermal conductivity not greater than 10W/(m ∙ K), and is a hollow thin-wall part; the cold platform 1 is made of a high-thermal-conductivity material, and the thermal conductivity of the cold platform is required to be more than 100W/(m ∙ K). In order to reduce the influence of coupling stress on the detector under the interference fit, H is designed and processed on the side edge of the cold platform 11The groove shape of the arc isolation groove can be arc-shaped or rectangular. The core column 2 is installed in the groove of the cold platform 1 through the axial positioning hole of the cold platform 1, a filler groove is reserved, and the cold platform 1 and the core column 2 are welded in a high-strength air-tight mode through vacuum brazing.
The design principle of the parameters (see the attached figure 2) of the arc-shaped isolation groove of the split type Dewar cold platform with low contact thermal resistance and coupling stress isolation is as follows:
(1) width H of arc isolation groove1The parameter confirmation method comprises the following steps:
1) calculating the deformation quantity delta L according to the yield strength of the material of the cold platform 1, the thickness of the cold platform 1 and the elastic modulus of the cold platform 1;
the cold platform 1 material yield strength σ; the thickness H of the cold plate 1; modulus of elasticity E of the Cold platform 1t(ii) a The deformation quantity is calculated by an elastic deformation formula as follows:
2) coupling interference, the value of which is 0.05-0.3 mm;
3) width H of arc isolation groove1The coupling interference magnitude and the deformation quantity delta L of the cold platform 1 at low temperature are not less than the sum of the coupling interference magnitude and the deformation quantity delta L of the cold platform 1 at low temperature and are not more than the thickness H/3 of the cold platform 1;
H/3≥H1≥(ΔL+) (formula 2);
(2) radius of curvature R of arc-shaped isolation groove1The parameter confirmation method comprises the following steps:
1) calculating uniformly distributed loads according to the coupling force and the diameter of the cold finger 3 of the refrigerator;
a coupling force F; refrigerator cold finger 3 diameter D1(ii) a The even distribution load that cold platform 1 received in coupling surface department:
2) calculating the inertia moment of the stress model according to the thickness of the cold platform 1 and the diameter of the cold finger 3 of the refrigerator;
the thickness H of the cold plate 1; refrigerator cold finger 3 diameter D1(ii) a (ii) a Moment of inertia of cold plate 1 to Y axis:
3) calculating a maximum corner and a processing corner according to the uniform load, the diameter of the cold finger 3 of the refrigerator, the inertia moment of the cold platform 1 and the elastic modulus of the cold platform 1;
uniformly distributing loads q; diameter D of refrigerator cold finger 31(ii) a Moment of inertia I of cold platform 1, modulus of elasticity E of cold platform 1t(ii) a The stress diagram of the split type Dewar cold platform 1 which has low contact thermal resistance and isolates coupling stress with the refrigerator under interference coupling is shown in figure 3, the stress model is an annular fixed supporting plate shell structure, the stress deformation condition of the split type Dewar cold platform is smaller than the stress condition of a simply supported beam under uniformly distributed load q, the stress condition of the simply supported beam under uniformly distributed load q can be simplified, and the maximum rotation angle is obtained according to the deflection equation of the simply supported beam under uniformly distributed load q:
the actual processing condition and the stress condition are considered, and the processing corner theta is as follows:
4) calculating the width of the arc-shaped isolation groove according to the diameter of the cold finger 3 of the refrigerator;
diameter D of refrigerator cold finger 31(ii) a The length of the arc isolation groove is as follows:
L＝D1+ (4 to 10mm) (equation 7)
5) Calculating the curvature radius according to the width of the arc-shaped isolation groove and the machining corner;
the arc-shaped isolation groove is long L; machining a corner theta; radius of curvature R1：
(3) The heat conducting surface D is the section of the cold energy of the cold finger of the refrigerator to the heat flow in the heat load transfer heat link, and conducts heat
Height H of surface DDThe design method comprises the following steps:
1) calculating the length of the heat conducting surface D according to the diameter of the cold finger 3 of the refrigerator and the width of the arc-shaped isolation groove;
diameter D of refrigerator cold finger 31(ii) a The arc-shaped isolation groove is long L; calculating to obtain:
LD＝L/2-D1(formula 9)
2) Calculating the cross-sectional area of the heat-conducting surface D according to the heat load of the heat-conducting surface D, the average heat conductivity coefficient of the material of the heat-conducting surface D in the delta T temperature, the temperature difference of the heat-conducting surface D and the length of the heat-conducting surface D;
the heat load of the heat conducting surface D is Q; the average thermal conductivity coefficient of the material in the delta T temperature is K; the temperature difference of the heat conducting surface D is delta T; the length of the heat-conducting surface D is LDThe area of the heat conducting surface can be calculated:
3) calculating the width of the heat conducting surface D according to the diameter of the cold finger 3 of the refrigerator;
diameter D of refrigerator cold finger 31(ii) a Considering thermal insulation and workability, the width of the heat-conductive surface D:
D2＝D1+0.7mm (equation 11)
4) Calculating the height H of the heat-conducting surface D according to the cross-sectional area of the heat-conducting surface D and the width of the heat-conducting surface DD。
The cross-sectional area A of the heat conducting surface D; width D of heat-conducting surface D2(ii) a Height of heat-conductive surface D:
the width H of the arc-shaped isolation groove is designed according to the parameters of the arc-shaped isolation groove of the split type Dewar cold platform with low contact thermal resistance and coupling stress isolation1Curvature radius R of arc isolation groove1And height H of heat-conducting surface DDCan be optimized iteratively to achieve the aims of reducing the contact thermal resistance and physically isolating the coupling stress.
The preparation method of the split type Dewar cold platform with low contact thermal resistance and coupling stress isolation comprises the following steps:
1) as shown in figure 2, the cold platform 1 is processed and formed according to the design requirement and is sent into a hydrogen furnace for high-temperature heating treatment at 900 ℃;
2) and (3) electroplating nickel on the joint of the core column 2 and the cold platform 1, wherein the thickness of a nickel layer is 0.05-0.1 mm, and performing high-temperature hydrogen burning treatment after electroplating. The high-temperature hydrogen burning treatment conditions are the same as those in the step 1;
3) actually measuring the circumferential size of the nickel-plated part of the core column 2 after the step 2 is finished, and repairing the corresponding size of the joint of the core column 2 and the cold platform 1 according to the size to ensure that the gap between the two parts is controlled to be 0.01-0.04 mm after the installation;
4) cleaning the core column 2 with acetone, alcohol and deionized water in an ultrasonic cleaning machine for 5-10 minutes to remove grease and debris remained on the surface of the part in the processing;
5) in the installation position of the special fixture, as shown in figure 2, solder is added into a solder reserve groove at the joint of the core column 2 and the cold platform 1, the solder reserve groove is placed into a vacuum brazing furnace, and the vacuum degree is lower than 1 × 10-3Pa, increasing 10-30 deg.C as welding temperature based on the melting point of solder, and maintaining for 5-20 minPerforming line welding;
6) after brazing, clamping the workpiece on a machine tool by using a special clamp, and grinding the upper surface of the coupling part of the cold platform 1 and the focal plane detector to ensure that the flatness and parallelism of the coupling surface meet the assembly requirements;
7) the method comprises the steps of performing mirror polishing on the outer surface of a core column 2 of a split type Dewar cold platform with low contact thermal resistance and coupling stress isolation and a cold platform 1, cleaning residual grinding paste after polishing, sequentially cleaning for 5-10 minutes in an ultrasonic cleaning machine by using acetone, alcohol and deionized water, and removing grease and debris remained on the surface of a part during processing.
8) Completely immersing the assembled and welded split type Dewar cold platform with low contact thermal resistance and isolated coupling stress into liquid nitrogen, taking out after the immersion time is 1-3 minutes, keeping the room temperature for more than 5 minutes, and repeating for 5-10 times;
9) detecting leakage of a prepared split type Dewar cold platform with low contact thermal resistance and isolated coupling stress by using a special tool, wherein when the leakage rate is less than 3 × 10-11Pa.m3When the leakage is detected in seconds, the leakage is qualified;
10) finally, the vacuum degree is better than 3 × 10 when the temperature is 250 DEG-4Pa continuously vacuum-exhausting for 48 hours for standby.
The split type dewar cold platform assembly with low contact thermal resistance and coupling stress isolation is realized.
The invention has the advantages that:
(1) the invention has simple structure, convenient operation and low cost;
(2) the thin-wall cylindrical core column with low thermal conductivity adopted in the invention has the thermal conductivity not more than 10W/(m ∙ K), has good machinability and mechanical strength, and can meet the strength requirement;
(3) the cold platform is made of a high-thermal-conductivity material, the thermal conductivity of the cold platform is not less than 100W/(m ∙ K), the temperature uniformity is good, and the cold platform has good thermal matching with an infrared detector;
(4) according to the invention, the arc-shaped isolation groove with the corresponding width is designed and processed between the coupling surface of the cold platform supporting structure and the mounting surface of the detector, so that the influence of interference coupling stress of the detector assembly of the split type refrigerator on the detector can be isolated, and the reliability of the detector is improved.
Drawings
FIG. 1 is a diagram of a split dewar cold platform with low contact thermal resistance and isolated coupling stress;
in the figure: 1-a cold platform;
2-core column;
3, refrigerating the cold finger of the refrigerator;
FIG. 2 is a partial enlarged view of a split dewar cold plate with low contact thermal resistance and isolated coupling stress.
FIG. 3 is a force diagram of a split dewar cold platform with low contact thermal resistance and isolated coupling stress.
FIG. 4 is a schematic diagram of the Y-axis moment of inertia of a split dewar cold platform with low contact thermal resistance and isolated coupling stress.
Detailed Description
The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings:
the long-wave 2000 × 3 unit infrared detector split type Dewar component structure for certain space project has the following assembling structure that according to the refrigerating capacity and power consumption requirements, a certain pulse tube type refrigerating machine is selected as the refrigerating machine, the working temperature is 60K, and the diameter D of the cold finger 3 of the refrigerating machine1Is 24.6 mm. As shown in figure 1. The specific embodiment of the invention is as follows:
1. the design result of the invention is as follows:
the core column 2 is made of TC4 material, and the wall thickness is designed to be 0.15mm according to the design standard and the machinability of the cylinder wall thickness of the vacuum pressure container.
The split type Dewar cold platform 1 which is in interference coupling with the cold finger of the refrigerator, has low contact thermal resistance and isolates coupling stress selects Mo material (brand high-temperature molybdenum or TZM) and high-heat-conductivity material, and H is designed and processed on the side edge of the cold platform 11The groove shape of the arc isolation groove is arc-shaped.
The design result of the parameters (see the attached figure 2) of the arc-shaped isolation groove of the split type dewar cold platform with low contact thermal resistance and coupling stress isolation is as follows:
(1) in order to reduce the influence of coupling stress on the detector under the interference fit, H is designed and processed on the side edge of the cold platform 11Width of groove, arc-shaped isolation groove width H1The design is as follows:
1) calculating the deformation quantity delta L according to the yield strength of the material, the thickness of the cold platform 1 and the elastic modulus of the cold platform 1;
the yield strength sigma of the material is 400 MPa; the thickness H of the cold platform 1 is 5 mm; modulus of elasticity E of the Cold platform 1t330 GPa; the deformation quantity is calculated by an elastic deformation formula as follows:
2) coupling interference magnitude is 0.05 mm;
3) width H of arc isolation groove1Should not be less than the sum of the coupling interference magnitude and the deformation quantity delta L of the cold platform 1 at low temperature, and less than the thickness H/3 of the cold platform 1, 1.67 is more than or equal to H1Not less than 0.056 (formula 2), and the value is 0.4 mm;
(2) radius of curvature R of arc-shaped isolation groove1The design is as follows:
1) calculating uniformly distributed loads according to the coupling force and the diameter of the cold finger 3 of the refrigerator;
coupling force F ═ 7N; the diameter D1 of the cold finger of the refrigerator is 24.6 mm; uniform load on the cold platform 1 at the coupling surface
2) Calculating the inertia moment of the stress model according to the thickness of the cold platform 1 and the diameter of the cold finger 3 of the refrigerator;
the thickness H of the cold platform 1 is 5 mm; refrigerator cold finger 3 diameter D124.6 mm; moment of inertia of cold plate 1 to Y axis:
3) calculating a maximum corner and a processing corner according to the uniform load, the diameter of the cold finger 3 of the refrigerator, the inertia moment of the cold platform 1 and the elastic modulus of the cold platform 1;
uniform load q is 1.47 × 104Pa, diameter D1 of cold finger 3 of refrigerator is 24.6mm, and inertia moment I of cold platform 1 is 2.56 × 10-10m4Modulus of elasticity E of Cold platform 1t330 GPa; the stress diagram of the split type Dewar cold platform 1 which has low contact thermal resistance and isolates coupling stress with the refrigerator under interference coupling is shown in figure 3, the stress model is an annular fixed supporting plate shell structure, the stress deformation condition of the split type Dewar cold platform is smaller than that of a simple supporting beam under uniformly distributed load q, the stress condition of the simple supporting beam under uniformly distributed load q can be simplified, and the maximum corner is the deflection equation of the simple supporting beam under uniformly distributed load q
Wherein the actual processing condition and the stress condition are considered,
theta takes a value of 20 degrees;
4) calculating the length of the arc-shaped isolation groove according to the diameter of the cold finger 3 of the refrigerator;
the diameter D1 of the refrigerator cold finger 3 is 24.6 mm; the length of the arc isolation groove is as follows:
l (D1 + (4-10 mm) ═ 29.6mm (equation 7)
5) Calculating the curvature radius according to the width and the maximum corner of the arc-shaped isolation groove;
the length L of the arc isolation groove is 29.6 mm; machining the angle theta is 20 degrees; radius of curvature R1：
(3) The heat conducting surface D is the heat flow section of the cold quantity of the cold finger of the refrigerator to the heat load transfer heat link, and the height H of the heat conducting surface DDThe design method comprises the following steps:
1) calculating the length of the heat conducting surface D according to the diameter of the cold finger 3 of the refrigerator and the width of the arc-shaped isolation groove;
diameter D of refrigerator cold finger 3124.6 mm; the arc-shaped isolation groove is long L; calculating to obtain:
LD＝L/2-D1not equal to 5mm (formula 9)
2) Calculating the cross-sectional area of the heat-conducting surface D according to the heat load of the heat-conducting surface D, the average heat conductivity coefficient of the heat-conducting surface material in the delta T temperature, the temperature difference of the heat-conducting surface D and the length of the heat-conducting surface D;
the heat load of the heat conducting surface D is Q equal to 5 mw; the average thermal conductivity coefficient of the material within the delta T temperature is:
K267W/(m · K); the temperature difference of the heat conducting surface D is delta T0.01K; the length of the heat-conducting surface D is LD5mm, the area of the heat conducting surface D can be calculated:
3) calculating the width of the heat conducting surface D according to the diameter of the cold finger 3 of the refrigerator;
diameter D of refrigerator cold finger 3124.6 mm; considering thermal insulation and workability, the width of the heat-conductive surface D: d2＝D1+0.7mm ═ 25.3mm (equation 11)
4) Calculating the height H of the heat-conducting surface D according to the cross-sectional area of the heat-conducting surface D and the width of the heat-conducting surface DDThe cross-sectional area a of the heat-conducting surface D is 9.4 × 10-6m2(ii) a The width D2 of the heat-conducting surface D is 25.3 mm; height of heat-conductive surface D:
the width H of the arc-shaped isolation groove is designed according to the parameters of the arc-shaped isolation groove of the split type Dewar cold platform with low contact thermal resistance and coupling stress isolation1Curvature radius R of arc isolation groove1And height H of heat-conducting surface DDCan be optimized iteratively to achieve the aims of reducing the contact thermal resistance and physically isolating the coupling stress.
2. Assembling and connecting steps
1) As shown in the attached figure 2, a cold platform 1 of the split type Dewar cold platform which is coupled with a cold finger of the refrigerator in an interference manner is processed and formed according to the design requirement and is sent into a hydrogen furnace for high-temperature heating treatment at 900 ℃;
2) and (3) electroplating nickel on the joint of the core column 2 and the cold platform 1, wherein the thickness of a nickel layer is 0.05-0.1 mm, and performing high-temperature hydrogen burning treatment after electroplating. The high-temperature hydrogen burning treatment conditions are the same as those in the step 1;
3) actually measuring the circumferential size of the nickel-plated part of the core column 2 after the step 2 is finished, and repairing the corresponding size of the joint of the core column 2 and the cold platform 1 according to the size to ensure that the gap between the two parts is controlled to be 0.01-0.04 mm after the installation;
4) cleaning the core column 2 with acetone, alcohol and deionized water in an ultrasonic cleaning machine for 5-10 minutes to remove grease and debris remained on the surface of the part in the processing;
5) in the installation position of the special fixture, which is ensured as shown in figure 2, silver-copper material (brand Ag72Cu28Ti) is added into a solder preformed groove at the joint of the core column 2 and the cold platform 1, and the mixture is put into a vacuum brazing furnace, wherein the vacuum degree is lower than 1 × 10-3Pa, increasing 10-30 ℃ as a welding temperature on the basis of the melting point of the solder, and keeping for 5-20 minutes for welding;
6) after brazing, clamping the workpiece on a machine tool by using a special clamp, and grinding the upper surface of the coupling part of the cold platform 1 and the focal plane detector to ensure that the flatness and parallelism of the coupling surface meet the assembly requirements;
7) and (3) performing mirror polishing on the outer surface of the core column 2 and the cold platform 1, cleaning the residual grinding paste after polishing, and then sequentially cleaning the residual grinding paste for 5-10 minutes in an ultrasonic cleaning machine by using acetone, alcohol and deionized water to remove grease and chips remained on the surface of the part during processing.
8) Completely immersing the assembled and welded split type Dewar cold platform with low contact thermal resistance and isolated coupling stress into liquid nitrogen, taking out after the immersion time is 1-3 minutes, keeping the room temperature for more than 5 minutes, and repeating for 5-10 times;
9) detecting leakage of a prepared split type Dewar cold platform with low contact thermal resistance and isolated coupling stress by using a special tool, wherein when the leakage rate is less than 3 × 10-11Pa.m3When the leakage is detected in seconds, the leakage is qualified;
10) finally, the vacuum degree is better than 3 × 10 when the temperature is 250 DEG-4Pa continuously vacuum-exhausting for 48 hours for standby.
The split type dewar cold platform assembly with low contact thermal resistance and coupling stress isolation of the split type dewar assembly of the long-wave 2000 multiplied by 3 element infrared detector is realized.
Claims (2)
1. The utility model provides a low thermal contact resistance and keep apart set formula dewar cold platform of coupling stress, includes cold platform (1) and stem (2), its characterized in that:
the cold platform (1) is made of a high-thermal-conductivity material, and the thermal conductivity of the material is not less than 100W ∙ M-1∙K-1(ii) a An arc-shaped isolation groove is formed in the side edge of the cold platform (1), and the groove shape of the arc-shaped isolation groove is arc-shaped or rectangular;
the core column (2) is made of low-thermal-conductivity material and is a hollow thin-wall part, and the thermal conductivity of the core column is not more than 10W ∙ M-1∙K-1；
The core column (2) is installed in the groove of the cold platform (1) through the axial positioning hole of the cold platform (1), a filler groove is reserved, and the cold platform (1) and the hollow core column (2) are welded in a vacuum brazing mode to achieve high-strength air tightness.
2. The split dewar cold platform as claimed in claim 1, wherein the platform is a low thermal contact resistance and coupling stress isolation system, comprising: the geometric parameter determination method of the side arc-shaped isolation groove of the cold platform (1) is as follows:
width H of arc isolation groove1Is determined by the following formula:
in the formula: h is the thickness of the cold platform (1), and sigma is the material yield strength of the cold platform (1); etIs the modulus of elasticity of the cold platform (1); the coupling interference is 0.05 mm-0.3 mm;
curvature radius R of arc isolation groove1Is determined by the following formula:
in the formula: l is the length of the arc-shaped isolation groove; theta is a processing corner; f is coupling force;
the heat conducting surface D is the heat flow section of the cold quantity of the cold finger (3) of the refrigerator to the heat load transfer heat link, and the height H of the heat conducting surface DDIs determined by the following formula:
in the formula: q is the heat load of the heat-conducting surface D, D1The diameter of the cold finger (3) of the refrigerator; k is the average thermal conductivity coefficient of the material of the heat-conducting surface D in the temperature delta T, and delta T is the temperature difference of the heat-conducting surface D.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010441675.5A CN111595463B (en) | 2020-05-22 | 2020-05-22 | Split type Dewar cold platform with low contact thermal resistance and coupling stress isolation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010441675.5A CN111595463B (en) | 2020-05-22 | 2020-05-22 | Split type Dewar cold platform with low contact thermal resistance and coupling stress isolation |
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| CN112504475A (en) * | 2020-10-23 | 2021-03-16 | 中国电子科技集团公司第十一研究所 | Infrared detector |
| CN113351951A (en) * | 2021-06-18 | 2021-09-07 | 中国科学院上海技术物理研究所 | Packaging structure of integrated ceramic cold platform and implementation method |
| CN114551641A (en) * | 2022-02-10 | 2022-05-27 | 中国科学院上海技术物理研究所 | Focal plane detector thermal layer structure for physically isolating coupling stress |
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