FR2505036A1 - MICROMINIATURE REFRIGERATION DEVICE AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

THE MULTI-LAYER MINIATURE REFRIGERATOR FOR LOW TEMPERATURES ACCORDING TO THE PRESENT INVENTION INCLUDES A COOLING CHAMBER 24 FOR A DEVICE TO BE COOLED CONTINUOUSLY, THIS CHAMBER BEING CONNECTED TO AN INPUT 20 AND AN OUTPUT 18 THROUGH DIMENSIONS OR CHANNELS THE ORDER OF THE MICROMETER AND WHICH ARE FORMED IN THE INTERFACES OF A LAMINATE OF GLASS PLATES OR OTHER SIMILAR MATERIAL, THESE CHANNELS FORMING A COUNTERCURRENT HEAT EXCHANGE SECTION 22 AND A CAPILLARY SECTION 26. APPLICATION: COOLING OF INTEGRATED CIRCUITS , ULTRA-SENSITIVE MEASURING INSTRUMENTS SUCH AS MONOMETERS, MICROSCOPE BOARDS, LOW NOISE AMPLIFIERS, ETC.

Description

Microminiature refrigeration device and method of manufacture

  The present invention relates generally to refrigeration and relates more particularly to

  microminiature refrigerators and their manufacturing process.

  Certain materials, called superconductors, have the

  ability to pass the electric current without resistance.

  Because superconductivity is only observed at

  eratures close to absolute zero, one of the main obstacles

  the large scale use of superconducting devices

  the need for reliable and continuous refrigeration.

  Superconducting devices, such as magnetometers, voltmeters, ammeters, voltage calibrators, current comparators, etc., are ultra-sensitive

  require a cryogenic environment to function

  traditionally holds this environment by a helium bath

  Helium is liquefied elsewhere and trans-

  carried to the Dewar vase and transferred to this vase.

  and the complication of such an operation seriously limited

  the use of these devices Most of the devices

  superconducting devices mentioned above only dissipate a few microvatts during their operation while the

  cryogenic systems available have the capacity to refrigerate

  several watts, so that there is a mismatch between these devices and these systems with respect to

relates to refrigeration.

  In addition, many devices such as turntables

  optical microscopes, the sample holders for diffraction

  X-ray equipment, devices for cryosurgery

  brain, for ECG measurements (electrocardiogram), MCG (magnetic

  tocardiogram) and EKG (electrocardiogram), as well as

  low noise amplifiers require operating temperatures

  below ambient temperature or are

benefited by these temperatures.

  In addition, there are many devices with high power and speed, such as transmitters and VLSI chips (integration on a very large scale) whose dimensions are small, of the order of one square centimeter, and which dissipate large quantities of heat, of the order of 10 to 50 watts. Conventional cooling devices, such as fans for convection cooling, can not

  not dissipate this amount of heat without increasing the

  the temperature above the ambient temperature.

  Miniature closed-cycle refrigerators, such as those based on the Gifford-McMahon, Vuilleumier, Stirling cycle, etc. have been developed. These refrigerators, whose capacities are of the order of 0.5-10 watts, are convenient and

  compact but, because of their moving parts, they introduce

  a large amount of vibration and magnetic noise.

  that interfere with the operation of the devices.

  Joule-Thomson miniature refrigeration systems have been developed which typically have a cooling capacity of between 0.5 and 10 watts. The design configurations of these compact systems are generally tubes with helicoidal fins and who are rolled up

  around a mandrel, the high pressure gas flowing to

  tubes and the low pressure gas flowing to the

  These heat exchangers, which have a helical fin and are wound around a mandrel by means of welding or brazing, are manufactured.

  laborious individual components Because of their

  complicated, we could not find until now in

  the practice of microminiature refrigerators with

  In the order of milliwatt, what is needed for many devices is a micro-miniature refrigerator with a size of about 12.7 mm to 101.6 mm with millivolt cooling capacity. It also requires processes for manufacturing microminiature refrigerators that avoid conventional laborious welding or soldering techniques and allow the formation of very small gas ducts to operate the heat exchangers in a laminar flow regime while, however, an effective exchange of heat The resulting absence of turbulence in the gas stream eliminates vibrations and noise, two points

  important for the applications of superconducting devices

  Very small size allows the incorporation of a complete set of "cryogenic superconducting detector system" as a hybrid component in an electronic circuit The refrigeration capacity of such microminiature devices

  allows the adaptation of the refrigeration system to the load.

  There is also a need for microminiature refrigerators of the same general dimensions as those mentioned above and capable of dissipating the large amounts of heat, at 50 watts, generated by certain small devices while maintaining ambient or below ambient operating temperatures. room temperature Such refrigerators should be easily manufactured and have configurations that are compatible with

  ordinary packaging or electronic boxes.

  As explained in more detail below, the microminiature refrigerator of the present invention comprises, in a single form and scale, a plurality of plate-shaped members sealingly joined together and forming a cooling chamber therebetween. capillary heat exchange passages and fluid passages for conveying high pressure incoming gas successively through the heat exchanger, the capillary section and into the cooling chamber Return or exit passages convey the cooling chamber fluid through the countercurrent heat exchanger with the incoming gas

  then to the outside of the device.

  Such a refrigerator mierominiature asks to reduce

  a conventional refrigerator by a factor of about a thousand.

  The design parameters for a micromine refrigerator

  ture having the same performance as a conventional refrigerator using a turbulent flow are described in the article "Scaling of Miniature Cryocoolers to Size Blicrominiature Size", V A Little, published in the special issue of April 1978,

  which is cited here for reference.

  In summary, the diameter d of the tube of the heat exchanger, the length 1 of this exchanger and the time of

  cooling t depend on the capacity that is proportion-

  to the mass flow m as follows: 0.5 0.6 0.6 A microminiature turbulent flow refrigerator with a capacity of a few millivatts should have a

  diameter d of 25 pm and a length 1 of a few centimeters.

  As the device becomes smaller, the mass flow ultimately becomes too small to allow turbulent fluid flow. Laminar flow operation then becomes possible without loss of fluid.

  refrigeration efficiency and gives better performance.

  The theoretical basis for the microminiature refrigerator design using laminar flow heat exchangers was discussed in the presentation "Design Considerations for Microminiature Refrigerators Using Laminar Blur Heat Exchangers", by WA Little at the Refrigeration Conference for Refrigerators. cryogenic detectors and electronic systems, Boulder, Colorado, EU Ao, b and 7 October 1980,

  which is cited here for reference.

  For microminiature heat exchangers

  in the laminar flow region with the same pressure regime and the same yield, the length

  the exchanger (1) must be proportional to the square of the di-

  meter (d) of the exchanger manifold. For example, a sample of

  Joule-Thomson generator operating with N 2 at 120 bar, with a capillary passage formed by a channel or groove 5 cm long, 110 pu wide and 6 pm deep must provide cooling of about 25 millivatts. different refrigeration by changing the width of the channel without changing the performance can therefore achieve operation under aerodynamic conditions free of vibration and turbulence noise, which is an advantage, particularly for superconducting devices that

  require an environment with very low noise.

  In a Joule-Thomson refrigerator of this type, it is normally convenient to use a channel or capillary groove to brake the compressed gas; however, it is commonly known that a porous structure such as a porous metal, a ceramic, can also be used with such success.

sintered, etc. to brake the gas.

  In order to increase the efficiency of the refrigerator for certain applications, one embodiment of the invention comprises two capillary sections arranged in series or in parallel and passages for conveying a substantial portion of the gas directly to the outlet passage of the invention. heat exchanger after passing through only one of the capillary sections.

  In order to build micro-refrigerators

  miniatures, new manufacturing techniques are needed.

  The conventional manufacturing techniques are not suitable for microminiaturization, because it is necessary to precisely form channels or grooves of the same size as conventional refrigerators and expansion nozzles which are 100 to 1000 times smaller than those of conventional refrigerators. the order of 5 to 500 nm and it is necessary that the device is sealed to withstand high pressures of the order of 10.5 to 210 kg / cm 2 for a good cooling performance * C is why, the main purpose of this

  invention is to realize a new micro-refrigerator

  miniature, especially for cryogenic cooling

  gene, and a new mode of assembly.

  Another object of the present invention is to provide a new microminiature refrigerator having a cooling capacity of the order of several millivatt%

up to 50 watts or more.

  Another object of the present invention is a new

  multilayer micreminiature refrigerator.

  Another object of the present invention is a

  single-stage cryogenic microminiature refrigerator.

  Another object of the present invention is a new

  multi-stage cryogenic microminiature refrigerator.

  Another object of the present invention is a new

  method of manufacturing a microminiature refrigerator.

  Still another object of the present invention is a novel process for producing microminiature refrigerators

  using etching and photo-etching techniques

  lithography. Yet another object of the present invention is a novel method of manufacturing a microminiature refrigerator

  using a sanding technique with fine particles.

  Another object of the present invention is to provide a novel small refrigerator comprising two or more plates made of a material of low thermal conductivity, such as presen sealed waterproof glass and containing at least one or more interfaces. of plates, a gas supply of micron size and return passages to a chamber which is adapted to continuously cool a superconductor or the like. In accordance with this object, the pressures of gas input can be of the order of 10.5 210 kg / cm 2 and the passages can have a width of the order of 5-500 pm and

a depth of 5-60 μm.

  According to the aforementioned object, the passages and the cooling chamber can be formed by recessing areas in the surface of the plate or by forming raised walls

  grooves or channels at the interface or inter-

faces of the plates.

  Yet another object of the present invention is a novel method of manufacturing a microminiature refrigerator

  by forming raised walls of grooves or channels.

  Another object of the present invention is to provide a new refrigeration unit comprising two or more multilayer refrigerators for cooling in

  cascade so as to reach low temperatures

gene.

  Another object of the present invention is to provide a new microminiature refrigerator composed of three or more similar glass or equivalent material plates assembled in the form of a battery and having high pressure inlet and low pressure outlet passages. for

  flow of a fluid and a size of the order of the micro-

  meter, these passages being connected to a cooling chamber

  and placed in separate layers at the interfaces

between the adjacent plates.

  Further, with respect to this object, it is contemplated in a laminate composed of three plates to form in series in a plate surface adhered to an intermediate plate a high pressure inlet, a heat exchange section and a section. capillary expansion passage, a surface of said intermediate plate forming one side of the passages and a low pressure return means formed by a recess being formed in the surface of the other plate which is glued

to said intermediate plate.

  Another object of the present invention is to provide a new refrigeration assembly comprising a special assembly and a support defining a passage for the gas at one of its ends, for example to mount the refrigerator so that it extends door on the inside of a

pregnant evacuated.

  The present invention therefore makes it possible to

  microminiature refrigerator and a method for making it.

  It should be noted that we can increase the scale of the

  microminiature refrigerator, both in terms of its size and

  that its capacity for certain applications is refrigerated.

  is new, whatever its size; however, it is the miniaturization of the refrigerator that is difficult and that is why it is described in detail in this paper The microminiature refrigerator turbulent or laminar flow comprises one or more plates on which some are formed channels or grooves for gas, of a size of the order of a micrometer and completed by

  one or more bonded plates resistant to high pressures.

  This microminiature refrigerator can be used for cryogenic refrigeration, but is not limited to this

use.

  Other objects of the present invention will appear

  in the description given below with reference to the drawings

annexed, in which:

  FIG. 1 is an exploded view showing refrigeration

  microminiature controller according to one of the embodiments of the invention; Fig. 2 is an overall plan view showing a portion of the microminiature refrigerator having a configuration of fluid passages according to another embodiment; Figure 3 is an overall perspective view showing a microminiature refrigerator part according to another variant; Fig. 4 is a plan view showing an embodiment of a multiple elementary module of a microminiature refrigerator; Fig. 5 is a sectional view showing another embodiment of a microminiature refrigerator; Figure 6 is a sectional view showing another embodiment of a microminiature refrigerator with multiple elementary modules; Figs. 7A-7E are sectional views showing

  phases of a process for manufacturing a micro-refrigerator

  miniature; Figures 8A-8D are sectional views showing phases of another method of manufacturing a microminiature refrigerator; Figs. 9A-9C are sectional views showing

  phases of a process for the manufacture of a refrigerator

  miniature having raised walls for forming grooves or channels; Figs. 1 OA-1 OD are sectional views showing phases of another method of manufacturing a miniaturized refrigerator;

  FIG. 11 is a sectional view showing the manufacture

  cation of an embodiment k multiple elementary module

  Fig. 12 is a plan view showing a use of

  and a refrigerator environment of the invention; Fig. 13 is a schematic view showing the fluid delivery circuit in the refrigerator of the invention; Fig. 14 is an illustrative section showing the stratified nature of the refrigerator and the multilayer fluid flow paths, details of which are shown in the subsequent figures;

  FIG. 15 is a partially broken plan view.

  showing a refrigerator support; Figure 16 is a section 16-16 of the figure; Figures 17, 18 and 19 are top plan views of the three elements (upper, middle and lower) which

  sandwich laminate or sandwich structure

  the invention according to a preferred embodiment particularly illustrating the various fluid flow passages and the various chambers; Figures 20 and 21 are sections along 20-20 and 21-21 of Figure 17; Fig. 22 is a section along 22-22 of Fig. 18; Figures 23 and 24 are sections along 23-23 and 24-24 of Figure 19; Fig. 25 is an exploded view showing an embodiment in which the flow passages are placed

In a different way -

  Fig. 26 is an exploded view showing an embodiment in which two low pressure flow paths are formed; Fig. 27 is a partial view showing a block or pack of increased thermal conductivity on the cold end of the refrigerator;

  Fig. 28 is an exploded view showing refrigeration

  In another embodiment, FIG. 29 is a plan view showing the plate of FIG. 28 in which the means constituting the low pressure passages for the gas are formed; FIG. 30 is a planar view of the plate of FIG. 28 in which means have been made forming high pressure passages; FIG. 31 is an illustrative view showing the laminate nature of two multilayer refrigerators combined to form only a single device or unit for cascading cooling; Figure 32 is a section 32-32 of Figure 31; Fig. 33 is an exploded view of another embodiment of the invention; and Fig. 34 is a plan view of another mode of

embodiment of the invention.

  Referring now to the drawings, it will be seen that FIG. 1 is an exploded perspective view of one embodiment of a microminiature refrigerator made in accordance with FIG.

  the present invention and comprising a body 12 in contact with

  The body 12 is made of a crystalline material (for example silicon), an amorphous material (for example glass), or a metallic material (for example copper or stainless steel); and the substrate 10 is made of a material such as "Pyrex", sodium glass or "Kovar" having a coefficient of thermal expansion which is compatible with the thermal expansion coefficient of the body 12

  preferably, the body 12 and the substrate 10 are thin pl

glass of mime extended.

  The body 12 and the substrate 10 must be sufficiently thick and / or mechanically resistant to withstand the pressure of the incoming gas, which pressure is typically of the order of 10.5-210 kg / cm 2 For example, a silicon body may have a thickness of about 300 μm, a glass body

  may have a thickness of about 254 μm to 508 μm, and a

  glass stratum has a thickness of about 254 μm to 508 μm.

  grooves or parallel channels 14 and 16 in the form of waveforms

  gulairel, having the width of 5-300 pm and separated by

  Sounds 150-500, m are formed or etched by corrosive etching into the surface of the body 12 which is mounted on the substrate. The grooves 14 and 16 mutually connect an outlet port 18 (the low-pressure return) and an orifice. inlet 20 (high pressure inlet) respectively to a tank or cooling chamber 24 The dimensions of the tank 24 are determined by the desired reserve capacity required for fluctuating demands The aforementioned grooves and tank are formed in the lower surface of the body 12 which is stuck directly on the upper flat surface 17, which closes the interface formed by the surfaces 13

  and 17 is a pressure-tight seal.

  The grooves 14 and 16 form cooling ducts

  respective low pressure and high pressure drains which extend juxtaposed over an initial length and thus constitute a heat exchange section shown generally at 22 A formed filter section 21

  fine grooves are provided between the intake and the

  In addition to the heat exchange section 22, the inlet groove 16 independently takes a sinuous and narrower shape at the location 26 of the substrate, allowing the fluid By way of example, the groove section 22 has a width of about 250 μm and a depth of 50 μm while the groove 26 has a width of about 125 μm. 10 p depth The end of the expansion duct 26 is connected directly to the tank 24 and the outlet groove 14 extends from the tank 24 rearward through the heat exchanger to the outlet port 18 Tank 24 has,

  preferably, a depth of about 20-50 μm.

  On the other surface or lower surface of the substrate

  an interface device 30 made of a metal alloy is

  It is suitable for use as ovaru, which is an alloy of iron, nickel and cobalt having a coefficient of expansion approximately the same as that of the material of the substrate 10, this interface device 30 having holes 32. and 34 who

  cross and communicate via the

  In the interface device 30 are glued two miniature tubes 36 and 38 through which a fluid reaches the refrigerator and comes back from the latter. The tubes 36 and 38 can be aligned with the holes 10 and 20 of the body 12. be made of stainless steel such as that used in hypodermic needles or Teflon tubing The interface device 30 is pressure-tightly attached to the substrate 10 by an agent

  suitable waterproof such as epoxy.

  On the upper surface of the body 12 in direct contact with the wall of the reservoir 24 is suitably mounted a device 40 to be cooled. The device 40 may be constituted by any number of operating devices.

  at a low temperature (for example, magneto-

  meters, gradiometers, bolometers and other ultrasensitive analog devices which are based on the Josephson effect or other devices which are well known in the art) or by devices intended to operate on

  higher temperatures (eg infrared detectors)

  semiconductor lasers or samples whose physical properties need to be determined) The complete assembly can be placed in a Dewar vessel or in a vacuum vessel to reduce heat transfer to

the constituent parts.

  The illustrated microminiature refrigerator is a Joule-Thomson type open-cycle refrigeration system in which a tube 38 is connected via a control valve 39 to a refrigerated gas container 37 under high pressure.

  pressure, such as nitrogen, hydrogen or helium.

  The high pressure gas enters at an inlet pressure of about 10 X 5-210 kg / cm 2 and has a flow rate of about -50 milliliters / second (STP) through port 20 and passes through the heat exchanger. heat 22 o the gas is cooled by the ultrafroid gas and under lower pressure leaving the device through the channel 14 p the orifice 18 and the tube 36 The high pressure gas leaves the heat exchanger 22 and passes through the capillary device 26 expansion or expansion o the pressure drop decreases the temperature of the gas entering the

  tank 24 in the form of an ultrafroid or cryogenic fluid

  The low temperature reservoir 24 itself cools the device 40 mounted on the reservoir 24 and the heat absorbed causes the vaporization of the fluid flowing through the channel 14 to the outlet port 180. An example of a microminiature refrigerator whose glass body 12 has a thickness of 0.5 mm, a width of 12.7 mm and a length of 76.2 mm has a refrigeration capacity of 100 millivatts at 122 OK, the dimensions of the grooves or channels are the order of 100 um and the flow

  about 30 milliliters / second of nitrogen (PBS) under a

  inlet pressure of 112 kg / cm 2 The substrate 10 is a plate of

glass having the same dimensions.

  Another example of microminiature refrigerator whose body is silicon measures 75 x 12 x 2 millimeters, has a heat exchange section of 30 centimeters in length and operates from room temperature up to

o K using C 02.

  A microminiature refrigerator may have a length of about 12.7 mm b 101.6 mm, a width of 12.7 mm, a thickness of 1.02 / 1.5 mm, with typical dimensions of grooves or channels between 5 and 500 pun and bulkheads

  150-500 pm wide, may have cooling capacity

  between 1.0-50.000 milliwattas at temperatures between 2 and 3000 K, and can withstand inlet pressures of 105-210 kg / cm 2 However, it should be noted that the microminiature refrigerator as described could have higher or lower dimensions both in

  as regards its size than its capacity for certain applications

cations.

  In addition to the open cycle described above, it will be understood that the refrigerator could be a closed cycle system using a compressor to recompress the gas. In addition, the manufacturing method described herein could be used to construct refrigerator parts using other cycles such as the Servel system, the Gifford-McMahon system, the pulsed tube system and the

Vuilleumier system.

  In some of the laminar flow devices, the design of the grooves or channels can be changed to a rectilinear shape as shown in FIG. 2 and not a "sinuous" shape. FIG. 2 shows the bottom surface of such a body. this embodiment, the gas

  under high pressure enters through the orifice 42, flows through

  to the parallel channels or channels 43 for heat exchange to section 44 of sinuous capillary channels and thence to the reservoir or cooling chamber 45, through the low pressure return 46 to the orifice An advantage of this design is that the low pressure return 46 as shown completely surrounds the high pressure conduits so that any minor leakage of gas from the high pressure conduit is captured by the low pressure return and does not occur. not escape into the surrounding emptiness that

  isolates the refrigerator from the environment

  Possible eventuality of this design is the long path that the heat must travel through the glass at the location of the heat exchange section between incoming conduits 43 and

  the outgoing channel 46 This difficulty can be avoided by combining

  the glass body with a glass substrate 48 shown in FIG. 3, which comprises printed or glued metal strips or wires 49. These strips or wires may

  be glued to the surface of the glass substrate that forms the

  terface with the body 41 The transverse conductive

  the 49 constitute a highly conductive path of heat laterally across the refrigerator while maintaining the

  thermal conductivity in the direction of the length of the

  operator at a low value determined by the glass.

  The cryogenic microminiature device and the refrigeration

  Also, a plurality of refrigerators, each using a different refrigerant, provides cascading cooling of one gas by another.

  gas and, as a result, provide refrigeration at

  Extremely low ports Additional ports may be included in the device, with channels interconnecting these

  additional ports and additional tanks

  For further cooling of a cryogenic device, FIG. 4 shows in perspective a module 51 of a multi-device body made of glass which includes a mini-refrigerator according to this embodiment of the invention.

the present invention.

  Two tanks or coolant chambers 52 and 53 are provided. The chamber 52 has an inlet duct 54 extending from the inlet port 55 through a sinuous heat exchange section 56 and a thin capillary section 57 to the bottom. 1 to the chamber, and an outlet duct 58 having a mux-extending sinuous section 59 of heat exchange that the section 56 terminating at the outlet port 60. The chamber 53 includes an inlet duct 61 which extending from an inlet 62 through a serpentine 63 heat exchange section and a capillary section 64 to the chamber, and an outlet conduit 65 having a serpentine heat exchange section 66 of the same extent as section 63 terminating at outlet port 67 A high pressure nitrogen source is connected to port 55, and a source

  of hydrogen under high pressure is connected to the orifice b 2.

  The two circuits therefore have a partial interaction thanks to which the fluid arriving in the chamber 53 is pre-cooled further before being subjected to an expansion. One of the circuits uses the Joule-Thomson nitrogen expansion to cool the hydrogen up to 50.degree. 'to 770 K at the place

  of the chamber 52 The other circuit uses the trigger Joule-

  Thomson of the previously cooled hydrogen to reach 210 K at the location of the chamber 53 The complete refrigerator as shown includes two heat exchangers, two expansion sections, two cold liquid tanks, and the inlet and outlet ports. output The size of the device is about 51 mm to 127 mm In a similar way, a system with

  three stages using nitrogen, hydrogen and

  lium would provide cooling at 4.51 K, Figure 5 is a sectional view of another mode of

  realization showing a multi-miniature microminiature refrigerator

  wherein the arrangements 73 and 74 of incoming and outgoing channels or grooves are formed on one and / or the other side of a glass body 75 on one and / or the other side of which two substrates or glass cover plates 76 and 77 are glued together. The high-pressure fluid flows along the channels 73 and returns through the channels 74. The channels 73 and 74 may be formed by etching or made of any other way in the surfaces of the body 75 as shown

  in solid lines or well formed by acid etching or

  in any other way in the surfaces of one and / or

  the other glass cover plates 76 and 77 which are

  to the body as shown in 73 'and 74' in phantom

  The channels 73 and 74 can also be formed using raised walls on the body 75 or on the substrates 76

  and 77 Arrangements 73 and 74 of channels or grooves constitute

  in each case, kill inlet sections, heat exchange sections, capillary sections and cooling chambers which can be arranged and associated as in FIGS. 1-4. The difference between FIG. 5 and FIG. 1 is that in Fig. 1 the inbound and outbound channels may be described as being formed in a single layer, i.e., they are made in the same or adjacent planar surface, while than

  in Figure 5 they are formed in a non-surface

  It is envisaged, in Figure 1, that the incoming and outgoing channels can be formed in the surfaces

opposite 13 and 17.

  FIG. 6 is a sectional view showing another embodiment of a microminiature refrigerator with a multiple elementary module. The channels or grooves 80, 81, 82 and 83 are formed in surfaces facing thin bodies 84, 85, 86, 87 and 88 glass by etching, by blowing a jet of particles or by the formation of raised walls For example, the nitrogen under high pressure enters through the channel 80

  and returns through the low pressure channel 81, while the hydra-

  gene under high pressure enters through channel 82 and is

  previously cooled by nitrogen in channel 81.

  Hydrogen at low pressure exits through the channel 83 Inlets, heat exchange sections, air ducts

  relaxation and the reservoirs are included in the channels

  as in previous embodiments.

  FIGS. 7A-7E illustrate one of the manufacturing methods

  cation of the refrigerator in which the channels or grooves

  are formed in glass or silicon

  than the acid The techniques that will be described are, in

  to a certain extent, well known in the manufacture of

  semiconductor positives, such as integrated circuits, and may include conventional photoresist masking and corrosion techniques. In one case, using a silicon wafer having an orientation

  surface crystalline on the plane (1,0,0), we can have

  During the course of anisotropic corrosion to form Y-shaped grooves in the surface of the silicon wafer. Alternatively, vertical walls can be obtained by using a silicon wafer having a surface orientation of the plane (1,1,0 In Fig. 7, a portion of a silicon plate 90 is shown in cross-section and a diaper

  91 of silicon oxide is provided on one of the main surfaces.

  The plate 90 has a thickness of the order of 300 μm and the oxide layer 91 has a thickness of about 9000 A. The oxide layer can be formed by heating the silicon wafer in an atmosphere of Wet oxygen The photoresist 92 is applied to the surface of the silicon layer 91 and exposed under a photomask having the desired configuration of channels or grooves. The photoresist is removed and

  corrosion attack the exposed oxide leaving the configuration

  The silicon oxide then acts as a mask and the exposed silicon is etched by the use of an anisotropic corrosive agent, such as ethylenediamine, by which the grooves 94 are obtained. Figure 7 C. After the formation of the Y-profile grooves, the remaining oxide layer 93 is removed from the silicon wafer and the plate is cleaned. An optically flat plate 95 is then glued. Pyrex or equivalent glass on the etched surface of the silicon wafer 90, as shown in FIG. 7 D The adhesion of the glass to the silicon surface is obtained by means of anodic or field-assisted bonding techniques. Then, as shown in FIG. 7 E, the back of the silicon plate 90 is etched or otherwise sized to reduce the thickness of the assembly and, therefore, the thermal conductance of the

* laminated refrigerator structure.

  The inlet and outlet ducts are then drilled or corrosively etched in the back of the glass substrate 95, and the gas pipes are then glued to the back of the plate by means of an epoxy resin. photolithography and corrosion by etching, one

  can form in a single phase the complete refrigerator comprising

  the heat exchanger, the expansion duct and the

  grooves or channels forming liquid tanks Plasma attack corrosion may be used, electrolytic corrosion may be used in lithography, or electron beams or X-rays, and etching corrosion may be used. The above method using a photoresist resin can be used when the body and the substrate are both glass plates, using

  classical materials and techniques.

  Figures 8 - 8 D illustrate another method of forming

  grooves or channels hollowed out in a hard, amorphous and isotropic material such as glass or a crystalline material such as silicon This method allows a good dimensional control, a better resolution compared to corrosion by etching, avoids "scouring This method is not limited to the manufacture of the microminiature refrigerator. In FIG. 8, a portion of a glass plate 100 with a thickness of about 508 μm is shown in cross-section and a layer of "resist" 101 is deposited on one of the faces or main surface of this plate The role of this resist layer "is to protect the underlying surface and form a pattern for the tracing of the grooves * This" resist " may be a photosensitive or non-photosensitive resist but must be sufficiently elastic or tenacious to withstand "sanding" of fine particles as will be described hereinafter The resist N may cover the surface of the complete plate 100 or be printed with a screen on the plate 100 so as to

  form-a drawing If letlresistw is a photoresist, one ltex-

  pose through a classic photomask to an ultra-light

  violet to form a drawing A new photoresist that meets the requirements of being able to withstand a "sanding" of fine particles consists of: 7 grams of gelatin (eg Knox) and 1 gram of ammonia dichromate dissolved in 50 cc of hot water The resist forms a thick spongy layer having a thickness equal to about 2030 times the thickness of the conventional "resists". The unexposed parts

  "resist" can be removed with hot water or by using

  of the protease enzyme, which digests the non-

  exposed and gives the structure shown in Figure 8 B The "resistance" 102 remaining is tenacious and resistant, capable of withstanding the abrasive action of "sanding" by fine particles

  while allowing the abrasion elimination of the expo-

  from the surface of the glass plate A device for abra-

  miniature pneumatic pressure (eg the device

  Model K; S S White), which results in a stream of fine particles

  alumina at a pressure of 5,600 kg / cm 2 acts as a device for "sanding" by fine particles The device "sanding" sweeps at a constant rate transversely the surface of the plate supporting the "resistance" surface that is 8B, and a stream of an abrasive powder having particle sizes of 17 μm can be used to remove about 2 μm of material each passes larger particles of powder (e.g. and 50 Sm) dig faster but can give a lower definition They can be used to make larger devices with adequate accuracy. The grooves 103 formed by this particle projection method and shown in FIG. 8C have a precisely set depth (2-300 μm)

  vertical and a definition of edges having a roughness of

  After the formation of the hollow grooves, the remaining photoresist is removed and the plate 100 is cleaned. The complete system of passages and cooling chamber of the refrigerator can thus be formed in a single phase. As can be seen in FIG. a substrate 104, such as a lid

  made of sodium glass, is stuck to the attacked surface of the

  It is the same mode of adhesion used in all embodiments to fix two or more than two

  plates to each other so as to form a set of

  permanent bleed tightness Such adhesion can be achieved with an epoxy glue or ultraviolet curable adhesive (eg optical adhesive: Norland's

  Optical Adhesive) It is possible to seal a thick

  of the order of the micrometer suction, using a capillary action of an adhesive diluted in the space between the plate 100 and the substrate 104 The refrigerator is

  then subjected to illumination by ultraviolet radiations

  intense violets until the adhesive cures and

forms a connection.

  In a variant, the cover plate or the substrate may be fused with the hollowed plate of the body,

  this with the help of a thin film of an impregnated welding glass

  screened on one or both plates using conventional methods for the manufacture of liquid crystal display devices. The inlet and outlet ducts are formed by drilling or by etching. outlet in the back of the substrate 104 glass and then glue the gas delivery pipes formed by Teflon tubes or hypodermic stainless steel tubes on the back of the plate 104 of glass with an epoxy resin using the fine particle sanding technique, an amorphous and hard isotropic material such as

  glass for the plate 100 forming the body of the refrigerator.

  The use of such materials avoids the problems associated with the high thermal conductivity of silicon and therefore lower temperatures can be obtained at the end.

  from the cold room of the refrigerator.

  FIGS. 9A-9C illustrate a manufacturing process

  of a microminiature refrigerator by formation of walls

  high, which constitute channels or grooves on a surface contrary to the formation by grooving the channels or channels in a surface, the plate 110 may be a crystalline material, amorphous or metallic, preferably glass,

  on the flat surface 111 o must be formed the grooves.

  The material 112, such as, for example, a glass frit powder, an epoxy resin, a welding glass, an ultraviolet curable glue, etc., is printed using a screen in the form of a drawing on the surface 111, as shown in FIG. 9 B When firing, the glass frit powder melts and forms the walls of the grooves Similarly, when the epoxy resin is vulcanized, when the welding glass is cured or when exposing the curable glue to

  ultraviolet radiation forms the walls of the grooves.

  Using this technique, spacings of 5-300 μm are accurately obtained. FIG. 9C shows a plate 113 forming a glass substrate whose adhesion is achieved by any of the attachment methods mentioned in FIG. previously to seal the exchanger ducts

  As before, one pierces or forms by corro-

  the inlet and outlet ducts in the back of the plate 113, and the gas lines are then

back of plate 113.

  FIGS. 10 -1 OD show a process for the manufacture of the refrigerator such as that of FIG. 5 in which the grooves are formed by corrosion on one or both flat cities of a glass plate 120 on which it is necessary to make adhere the two glass plates 121 and 122

  (Figure 10 D) Especially for flow design

  laminar process, this process simplifies the design of

multi-stage systems.

  In order to manufacture the device, a thin continuous layer of glass frit is printed on the plate 120 on the plate, or each side of this plate is coated with a weld glass 123 (the same operation can be done on a single surface). 8 té), then these layers are melted, as in the process phase shown in Figure 10 Then, or

  prints a "resistance 124 on the upper and lower surfaces

  or a photoresist is used which is exposed and developed on each side at 124 (FIG. 1 OB), so that each side of the plate 120 carries the desired pattern or grating, this is achieved by using one of the methods described above. The plate 120 is then abraded and the resist is removed leaving the plate 120 shown in FIG. 1 OC. that the networks 125 and 126 of grooves respectively appear in separate layers and that the glass surfaces between these networks are covered by a frit 123

having melted on its surfaces.

  The glass cover plates 121 and 122 are then adhered to the top and bottom surfaces using a program which may include a first

  heating the complete assembly to a softening temperature

  This also seals the inlet and the outlet to seal the refrigerator (Figure 1 OD). the end of the cold room or cooling chamber connect the tank, which is connected via the capillary passages or high pressure channels 125, to the low pressure channels 126 The high pressure gas passes through the channels 125 to to the cooling chamber and then back through the channels 126 The channel layers can be formed in one and / or both plates 121 and 122 instead of being

  formed entirely in the plate 120 constituting the body.

  Figure 11 illustrates a method of manufacturing a

  multi-stacked refrigerator 130, such as refrigerator

  Figure 6 Using this method, it is possible to realize

  Conveniently use multi-stage devices in which different gases pass into spaced apart layers through passages formed in a glued stack of plates

as shown in Figure 11.

  This refrigerator comprises in the form of a stack five glued glass plates having, preferably, the mimes

  In this case, the three

  In the surface of plates 131 and 132, grooves 134 and 135, respectively, are formed by means of the methods of FIGS. 7A-7E, FIGS. 8A-8D or 9-9C, and forming on the surface of the plate 133 grooves 136 and 137, respectively, for example by the method of FIGS. In each case, the particle blowing mode is preferred, the open ends of each groove being spaced apart by

  layers of frit melted on the glass surface.

  In the illustrated two-stage device, the high pressure nitrogen can enter through the channel 134 and return

  by the low-pressure channel 135, hydrogen under high pressure

  can enter through channel 136 and is preheated by

  heat exchange with the nitrogen present in the channel 135.

  Hydrogen at low pressure returns to the outlet through channels 137 The complete set is

  assembled using a welding glass as described above.

  In this two-stage refrigeration unit, it is possible to use plate variants having elevated walls forming grooves instead of grooves obtained by digging. The communication orifices between the various layers are suitably formed.

  Although in the embodiments described above

  the refrigerator has a crystalline or amorphous body, in some cases this refrigerator may be formed by corrosive etching with photographic processing of a copper film deposited on the surface of a circuit board or a thin foil. Although the described refrigerator is of the open cycle type, as indicated above, closed cycle refrigerators can be manufactured using the techniques of the present invention. It will be appreciated that the grooves or channels may also be formed as described herein. above a capillary tube, the tube being in contact with the inner confinement surface of a

  another tube to form a cylindrical refrigerator with

  heat can be sealed on this tube

  the inner tube using a retractable tubing material

  hot table, such as the Alliaget I Betalloy * t (Raychem

Corp) for the outer tube.

  The dimensions of the grooves, the techniques for the adherence or bonding of the surfaces, the formation of the grooves and other characteristics of the refrigerator can be those described below with regard to the embodiments of the figures.

12-32,

  Referring to Figure 12 which illustrates a typical installation, we see that the refrigerator 211 is mounted at one end of a support 212 inside which it is fixed in such a way that the refrigerator and the support

  usually constitute a monobloc assembly referenced 213.

  In the set shown, the refrigerator contains

  flow passages which are connected via the

  diary of the support to fluid inlet and outlet means.

  FIG. 12 shows the assembly mounted in a housing 214 formed by the interior of a typical shaped enclosure 215.

  boot with a suitable cover 216 airtight.

  In the enclosure, the support 212 is set appropriately

  at the bottom of the housing and the refrigerator extends in k-holder

  through this housing Preferably the housing is subjected to a pressure lower than the atmospheric pressure

  through conduit 217 leading to a vacuum source 218.

  The device 219 must be continuously cooled

  and who can Sire a small semiconductor chip or a dis-

  similar positive is suitably mounted within the housing 214, preferably in contact with the

  colder of the refrigerator, as shown in

  broken on the drawings and any c Ablage (not shown) extends

  From this chip or device passes through sealed openings in the enclosure. In the illustrated embodiment, this device is preferably mounted in direct contact with the glass surface of the refrigerator, which serves as a cover for the chamber 2249. Referring to FIG. 13, it can be seen that at least a schematic representation of the fluid path is shown. The refrigerator 211 has a bore 221 serving as an inlet for the admission of a gas under high pressure. flows through a passage having a heat exchange section referenced 222 and a capillary section 223 of a

  smaller diameter to reach a cooling chamber

  The device 219 to be cooled is placed as close as possible to the chamber 224, which is the coldest part of the refrigerator, as will appear, and the fluid leaving the chamber 224 returns along a passage 225 which extending contiguously to the inlet passage section 222 in a mutual heat exchange arrangement and terminating at an outlet port 226 These passages have a micron section for very low temperature refrigeration capacity of the order

  millivat, as will appear.

  In the invention, the inlet port 221 and the orifice

  226 are connected to bores 227 and 228, respectively

  Actually, the support is mounted so that in the chamber it connects the bores 227 and 228 to the fluid inlet conduit 229 and the fluid outlet conduit 231 which protrude from the fluid. When the system is an open cycle refrigerator, the conduit 229 is connected to a source of pressurized refrigerant gas and the conduit 231 is connected to a suitable exhaust In a closed cycle system, the conduits 229 and 231 are connected by a loop containing a set of pressurization and

condenser.

  As can best be seen in FIG. 14, the refrigerator 211 comprises a three-element sandwich.

  essentially divided by three flat glass plates or other plates of the same low thermal conductivity, 232, 233 and 234 glued, exactly similar, which have approximately the same length and the same width and a thickness preferably of the order of 508 μm. median may be thinner than other plates to increase heat exchange between inlet and outlet channels

  may have, overall, a width of about 12.7 mm, a length

  57.2 mm and a total thickness of about 1.5 mm.

  this representing an embodiment capable of operating successfully and the effects of which have given good results Another embodiment capable of operating successfully has a width of 5.1 mm, a length of 25.4 mm and a thickness

of 1 5 mm.

  The refrigerator has a layered gas structure

  In other words, passages 222 and 223 of food

  fluidization and the chamber 224 are formed to form a fluid flow passage layer within a sandwich substantially in a plane while the return passage is formed to form a separate layer of fluid flow passage inside

  sandwich substantially in a spaced plane As it appears

  these layers are in flow communication from

  fluid through an opening in the wall of the chamber.

  FIGS. 17-24 show a detail of another embodiment The thin flat glass plates 232, 233 and 234 have the same dimensions The intermediate glass plate 233 is uniform with flat and opposite smooth surfaces

  235 and 236 (Figure 22) The top plate 232 as it-

  As shown in FIG. 17, the plate 232 has in its bottom surface 237 recessed regions, that is to say wanures or channels, forming the inlet orifice 221, the section 222. heat exchange passageway 223, the capillary passage section 223 and the series connected chamber 224 and constituting a continuous flow path for the fluid from the inlet port 221 to the chamber 224. is in the form of a well

closed bottom.

  The intermediate plate 233 closes one of the sides of the passages of the plate 232 and has at one of its ends a through hole 238 aligned with the orifice 221 of the plate 232 of the assembly. The plate 233 comprises at its other end

  a through hole 239 aligned with the chamber 224 of the assembly.

  The lower plate 234 has on its upper surface 240 a low-pressure fluid return path which includes a generally rectangular, wide-area rectangular recess 241. A series of spaced ribs 242 and several rows of projections 243 are provided on the bottom. of the recess so as to be in bearing contact with the lower surface 236 of the intermediate plate of the assembly while not substantially impeding the flow of the fluid The plate 234 has a through hole 243 which is aligned with holes or holes 238 and 241 of the assembly of FIG. 160 A second hole 244 formed in the plate 234 opens into the recess 241 The fluid leaving the chamber

  224 of the assembly passes through the orifice 239 and enters the

  241 and then out through the hole 244.

  During assembly, the glass plates 232, 233 and 234 are adhered in the form of a pressure-tight stack at their interfaces. The laminate is placed in the

  support 212 o one of the ends is glued to the metal support-

  using adhesive layers 249 and 250, holes 243

  and 244 being aligned with the holes 227 and 228, respectively.

  This ensures the support of the refrigerator so the watertight inlet and outlet connections for the flow passages

refrigerator.

  The dimensions of the passages are chosen for

cooling capabilities.

  The passages 222, 223, 225 have a size of the order of one micrometer The passages 222 and 223 particularly have a size of the order of a micrometer, their dimensions being of the order of 5-500 pm In a typical refrigerator, these The passages can have a depth as small as 5-10 μm and a width as small as 150-200 μm. In passage 222, the gas passes in the form of a laminar flow, which has the effect of reducing vibrations, noise and noise. and eliminate any other problem resulting from a turbulent flow The recess

  241 has, typically, a depth of about 20-

240 pim.

  In an alternative embodiment of the above embodiment, the means forming the inlet and outlet passages may be hollowed or otherwise formed in opposite surfaces of the intermediate plate 233, or one of these means may be formed in plate 233 while the other

  is formed in one of the other two plates.

  In order to operate the embodiments of FIGS. 12-24, a compressed gas, such as, for example, nitrogen or ammonia, is introduced at room temperature (15.60 ° C.-32.30 ° C.) through the duct. 229 and the orifice, 221 The pressures of

  these gases are, in this region, 10.5-210 kg / cm 2.

  The gas flows through the heat exchange section 222 of the passages whose size is of the order of one micron and then through the capillary section 223 whose cross section is smaller and where the gas relaxes and decreases. The fluid in the chamber 224 can be a gas, a liquid or a mixture in the supercooled state and, in any case, it constitutes the

the coldest of the refrigerator.

  The fluid leaving the chamber 224 through the orifice 239 flows at a reduced pressure across the passageway.

  return 225 in a state of heat exchange with the passage of

  tream 222 and then reaches the outlet orifice 226 and the conduit 231. It will be noted that this heat exchange takes place from

  substantially straightforward way through the thin uni-

  shape of the intermediate glass plate 233 and that it is

  effectively and accurately kills the low-pressure cold exit gas previously cooling the incoming gas

High pressure.

  In the present invention, the heat exchange between the heat exchange sections of the high pressure gas passages and the low pressure return passages takes place through walls having the thickness dimension of the respective plates, thanks to which a precise relative location is possible, the heat exchange being regulated

by the thickness of the plate.

  One of the main advantages of obtaining a low pressure backflow with laminar flow in a separate layer is that the refrigerator can operate at a lower temperature than the refrigerators designed for turbulent flow in the return passage.

  because of the fact that the channels in which the

  The laminar flow generates lower counterpressures and, consequently, lower operating temperatures. Experience has shown that multilayer refrigerators of the above-mentioned type can be manufactured using a smaller volume of material than one-third of a single-layer refrigerator (a single layer is the case in which 'input and return are formed in a single interface) having the same cooling capacity

  and therefore operating more efficiently.

  The plates 232, 233 and 234 are preferably made of soda-lime glass, Pyrex or any other similar material.

  low thermal conductivity These plates must be

  have a low thermal conductivity and be susceptible to

  machining tips for forming passages and chambers

  excavated in the surface as described above - this is

  particularly desirable when cooling down

  -500 C or below this temperature is necessary Any-

  time, when the required temperature is not so low, it is better to use a top plate made of

  good conductivity but having about the same coeffi-

  thermal expansion that beryllium oxide, silicon

  or a crystalline aluminum oxide to obtain a

efficient heat exchange.

  In some embodiments, the high-pressure inlet system and the pressure-transfer system may be formed by corrosive etching or otherwise excavated in the opposite sides of the intermediate plate, while the other two the pile are planed so as to be flat to close the sides of the recesses. It is also envisaged in the context of the present

  invention of forming a layer (high and low passages

  sions) in the intermediate plate and the other layer in

  one of the upper or lower plates.

  Fig. 25 depicts an embodiment in which three similar plates 251, 252 and 253 of a thickness of about 508 μm provide the micrometer-sized passages. The plates are glued in the form of a stack. in practice, but they have been represented here by an exploded view to better show in detail the

  components of the refrigerator.

  The high pressure gas is introduced through the inlet 254 of the plate 251 which is a flat glass plate having flat surfaces, and it continues through the hole 255 of the plate 252 to a cell or well. 256 closed bottom in the upper surface of the bottom plate

  253 which may be identical to the plate 232 of Figures 12-24.

  The high pressure circuit is extended in plate 253 under

  the shape of a heat exchange section 257 and a

  capillary expansion 258 relaxation opening in the recess 259

forming a cooling chamber.

  The intermediate plate 252, which may be identical to the plate 234 of FIGS. 12-24, is flat and flat on its lower surface so as to complete the passages of the plate 253, and its upper surface is hollowed out at 261 to form the return low pressure A through hole 262 formed in the bottom of the recess 251 connects the low recess

  pressure 261 to an external circuit.

  Figure 26 shows a similar embodiment

  in Figure 25 but having two low pressure returns.

  Four plates of similar size are glued here in the form of a stack and are shown in exploded form in FIG. 26 for reasons of clarity. The plates 251, 252 and 253 are as in FIG. 25, and a fourth plate 264 is added to form a second low-pressure return The plate 264 may be a copy of the plate 252

  with the low-pressure return recess formed in its

  However, a through-hole 265 in the plate 253 at the bottom of the chamber 259 connects the chamber to the low-pressure recesses 266 formed in the upper surface of the plate 264. Further, no hole corresponding to the hole 262 is formed in the chamber. recess 266, but the low pressure gas from the recess 266 flows through a through hole 267 formed in the plate 253 and through a through hole 268 formed in the plate 252 to join the escaping gas. the recess 261 through the orifice of

Exit 263.

  In this embodiment there are therefore two

  heat exchange jets providing pre-cooling

  faster and more advanced gas entering under high pressure.

  In the embodiment of FIG. 27, the

  The cold unit of the refrigerator 211 is modified inasmuch as the cooling chamber, instead of being a recess as in 224 in FIG. 14, is a through opening 270 formed in the glass cover plate 251 and, on this opening, a thin flat block 271 of a material having a very high thermal conductivity is bonded in a pressure-tight manner. The device 219 which has to be cooled

  is mounted directly on block 271 * The fluid, at its temperature

  lowest level, is therefore in contact with the surface of

below block 217.

  The preferred materials for block 271 are silicon, beryllium and sapphire. All these materials have

  high thermal conductivities which increase considerably

  at a very low temperature and can be combined with a suitable plastic material with about the same coefficient of thermal expansion. The preferred material is beryllium oxide. This material combines high hardness with a coefficient of thermal expansion close to the material.

  preferred plate, that is to say glass.

  Figures 28-30 illustrate another embodiment of a multilayer refrigerator operating on the

same principle.

  As can be seen in FIG. 28, the laminate forming the refrigerator comprises three thin flat plates 280, 281 and 282 of a material which can be etched, i.e. hollowed out, by corrosions. 280 and 281 are glass plates and the plate 282 may be glass for many applications but for applications other than these it may be in a vitreous material having a higher thermal conductivity, such as for example crystalline aluminum

  (sapphire), beryllium or silicon.

  On the upper surface 283 of the plate 280, a high pressure gas inlet passage is formed by corrosion or equivalent, essentially consisting essentially of

  a recess 284 of capillary dimension of the order of the micro-

  meter extending from inlet port 285 as a labyrinth to a cooling chamber

  central 286 formed by a recess.

  The plate 281 has a planar continuous bottom surface 287 sealingly pressed against the pressure on the plate 280 to complete the chamber and the inlet passage and, in the upper surface 288 of this plate, is formed a large recess 289 of low-pressure gas return, which is connected to the chamber 286 through an orifice 290 A series of raised radial ribs 291 present in the recess 289 bear, so as to withstand it, against the chamber 288

  to increase the mechanical strength of the assembly.

  The gas leaving at a reduced pressure flows into

  the recess 289 to an outlet port 292 which is

  run through one of the plates 280 or 282 until a

  external system as in the previous embodiment.

  As shown in Fig. 28, the plate 282 is pressure-tightly adhered to the plate 281 so as to complete the return passage 289 of a

  depth of the order of a micrometer.

  On the upper surface 293 of the plate 282, the semiconductor chip 294 is directly attached to be cooled, and a printed circuit or the like circuit 295 associated with this chip extends on the plate 282 to appropriate external electrical connections. is thus exposed to the cooled fluid substantially at the location of the coldest region of the refrigerator This method of fixing the device to be cooled can be used in all

  embodiments described in this disclosure.

  In the foregoing description, the capillary passage

  The arrangement is in heat exchange relation with the fluid in the outlet recess 289. This arrangement may be preferable for further temperature refrigeration.

  o Cooling to cryogenic temperatures

  For example, ammonia can be used as a refrigerant to achieve temperatures of 300 C and refrigeration capacities up to

  vatts As the requirements come closer to a re-

  cryogenic cooling, the length of the

  heat exchange region with a view to pre-cooling the

  For example, the refrigerant can be "preon" introduced under high pressure and which is subjected to a pressure drop, relaxes and cools in the capillary section 284 while being in contact with it.

  of heat exchange with the return gas present in the

  289, for the purpose of further cooling

  that the gas is nitrogen for cryogenic cooling

  As in the embodiment of Figures 12-24, the length of the heat exchange region is increased.

  intended for pre-cooling.

  The above-mentioned refrigerator may be of particular interest in cooling larger computer chips such as those known as VLSI (Very Large Scale Integration) chips which are presently designed for higher circuit densities and for a larger scale. increased power capacity resulting in dissipation of large amounts of heat, ie -50 watts Refrigeration allows these chips to operate at lower temperatures, improves their efficiency, their

  speed and reliability, and increases their useful life.

  Figures 31 and 32 illustrate a set of refrigeration

  two multilayer refrigerators

  between five plates forming a laminate This configuration for cascade cooling allows the pre-cooling of a

  fluid by another fluid to obtain either a cooling

  For example, ammonia could be used in the first stage of the cascade layers 294 to pre-cool nitrogen in the layers 295 of the second stage. This decreases the time for cooling the water. nitrogen by a factor of three or more as another example, one could use

  nitrogen in the layers 294 of shorter stage to re-

  Pre-cool the hydrogen, which is then cooled down to 200 K Low-boiling fluids such as hydrogen and helium do not cool in the

  Joule-Thomson cycle unless they are cold

  in this way until the appropriate temperature

  can achieve in a similar way refrigerators com-

* carrying three or more floors.

  The refrigerator may have other characteristics

  ticks and dimensions of grooves or channels such as those

  described in the embodiments of FIGS. 1-11.

  The formation of the grooves or channels and the adhesion of the plates are carried out here using groove forming techniques and bonding or bonding material

  described with respect to said embodiments.

  According to another aspect of the present invention, it has been discovered that there is a relationship between the efficiency of the heat exchanger and the minimum temperature which can be

  reached in the cooling section of the refrigerator.

  The minimum temperature is determined by the pressure of the gas k

  the place where the gas leaves the cooling chamber.

  The lower the pressure at this point, the lower the temperature. On the other hand, the efficiency of the heat exchanger

  is a function of the pressure drop along the discharge channel

  This increases the pressure drop resulting in more efficient heat exchange. For efficient heat exchange that leads to a shorter cooling time and / or lower gas consumption rates, it is necessary that the gas pressure, when it leaves

  the cooling chamber is relatively high Inver-

  In order to obtain a maximum temperature drop in the cooling chamber, it is necessary that the pressure of the gas

  at the same point is relatively weak.

  The embodiments of FIGS. 33 and 34 represent

  In each of these embodiments, two capillary sections are formed and a portion of the incoming gas is diverted directly to the

  outlet passage of the heat exchanger after working

  poured one of the capillary sections thus bypassing the

cooling chamber.

  The embodiment of Fig. 33 comprises a stack of four plates 300, 302, 304 and 306 which may be formed of the same material and which are glued to each other in the same manner as in the embodiments.

  described in this embodiment, two sec-

  The capillary portions 308 and 310 are formed in series with one another. Between the two capillary sections a small orifice 312 is formed leading to the upstream outlet end 314 of the heat exchanger. and which is formed in the plate 300 The downstream end of the second

  capillary section 310 is connected to the cooling chamber

  316 which is itself connected by an orifice 318 to a second outlet passage 320 formed by the recessed face of the plate 304 ribs 322 are formed in the plate 304 to impart rigidity to the assembly and to ensure

  uniform spacing between plates 304 and 306.

  During operation, the gas under high pressure

  flows through the inlet section of the heat exchanger

  324 then relaxes and decreases pressure as it then flows through the first capillary section 308 to the orifice 312 At this point, the flow of gas is divided so that a substantial portion of the gas continues its course through port 312 directly to

  outlet passage 314 of the heat exchanger.

  Port 312 and outlet passage 314 are sized

  in such a way that relatively high pressure is

  maintained at the location of this port 312, typically

  A pressure drop of 10 to 30 bars is therefore produced in the outlet section 314 of the heat exchanger.

heat exchange function.

  The remaining gas flows through the second

  capillary 310 to the cooling chamber 316.

  Here the gas absorbs heat from the device that is subjected to h. cooling then flows through the orifice 318 to the outside of the device through the second outlet passage 320 at a relatively low pressure, typically

  a pressure of 2 to 3 bars This low pressure ensures the

  the desired low pressure in the cooling chamber.

ment.

  It has been found that both efficiency of the heat exchanger and cooling can be achieved.

  by allowing the flow of 50% to 95% of the gas through

  towards the orifice 112 and through the outlet passage 314 of

the heat exchanger.

  Fig. 34 shows a plate 324 which can replace the plate 302 of the embodiment of Fig. 33 to give similar results. In this embodiment of the invention, the two capillary sections, indicated at 326 and 328, are arranged in parallel and not in series as in the embodiment of Figure 33 The incoming gas passes through the inlet section of the heat exchanger 324, to

  through the first capillary section 326 and through the ori-

  fice 312 to reach the outlet passage 314 of the heat exchanger The remainder of the gas passes through the second capillary section 328, enters the cooling section

  316 and thence into the replacement outlet passage 320.

  As in the previously described embodiment,

  can get good results by diverting through ltori-

  fice 312 from 50 to 95% of the incoming gas.

  The refrigerator may have other characteristics

  ticks and dimensions of grooves or channels as previously described Formation of grooves or channels and adhesion

  or bonding the plates in the present embodiment can

  can also be performed by groove or channel formation techniques and by using bonding materials or

  adhesion previously described.

  Refrigerators as described above are suitable

  are perfectly fine for a wide range of applications

  laboratory and other similar applications.

  conveniently carry out an economic operation in

  very low temperature as an alternative to cryovials

  volatile liquid genes These refrigerators have small dimensions and low weight, which allows them to be used

  directly on instruments such as microphones

  These small dimensions give the possibility of

  use to cool very small devices that allow

  Optical tools or instruments can directly observe or work on the device without interference Low gas consumption

  days of continuous use from an ordinary cylinder

  compressed gas The temperature setting is simple.

  Refrigerators have a simple structure and can be

  made and controlled in a relatively simple and safe way.

Claims (12)

  1 Microminiature Cryogenic Refrigerator for   to cool superconducting and other devices   like elements, characterized in that it comprises at least two elements of glass or other similar material of low thermal conductivity having substantially the same   coefficient of thermal expansion, a means of adhering   these elements in leaktight contact with each other   pressure on an interface area in such a way as to   storing a rigid laminate and means forming in said laminate a low temperature chamber connected to a   fluid inlet port through a feed fluid passage   micron size along said interface zone, said feed passage comprising a   first section to deliver a highly   a second capillary section of smaller diameter, connected in series and opening into said chamber, whereby the gas under high pressure can relax and decrease   temperature before entering the chamber, and a step   return line having a section extending through the laminate substantially on the same extent and in relation   countercurrent heat exchange with said first   said feed passage, and means whereby said chamber can be in heat exchange contact with a device to be cooled.   Refrigerator according to Claim 1, characterized in that the said passages are grooves or channels formed by recess in surfaces of one or several of said elements.   Refrigerator according to Claim 1, characterized in that the said passages are grooves or channels consisting of raised walls formed on the   surfaces of one or more of said elements.   4 Refrigerator assembly 3 multiple cooling characterized in that it comprises: a.) A plurality of elements in sealing surface contact; means positioned at the interfaces between said elements for forming an even number of fluid flow t-fillers, portions of which are arranged for heat exchange; c) means for passing refrigerants   different to counterflow from uz inlet to h.   an outlet orifice of the iraje-ts 7 epodes h. ensure a cooling and cazerade * m 1 t, E as reria g & t t r e d u c e, nseba l t t h e w ith th e 5   fuiuhel entrance and the   meter decks a strrtt 5 f; At the end of this section, go to the first section and go to the end of the first section.   caplliaa 2 C sri r hamr: cool-   The second time was a second time to meet the following requirements: - This was done by a 4-hour pass through a two-second second pass. secti, -c -irce cool neither of them in -r so: s leasse pres-   C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C   led it d e r% u, ii -i 1 Wc C pici J l-adi te S e Ond e c ham-   being in fact: d: Jialcur z: ec lesdies three-   second and second sections of heat exchange.   A process for producing a refrigerator in which a thin glass plate adheres by its surface and in a pressure-tight manner to another plate having about the same coefficient of thermal expansion, this process being characterized by the it comprises the steps of: a) forming on said glass plate a layer of a material resisting sandblasting by fine particles; b) forming a flow path pattern in said resist material by lithographic masking and selective corrosion so as to thereby strip the underlying surface of said glass plate in said drawing; c) to be performed at a pneumatic abrasive device miniature scanning a movement transversely to said glass plate so as to form to the required depth grooves or channels recessed in said surface by blowing fine particles; then d) adhering said other plate to the recessed surface of said glass plate * 7 Process according to claim 6, characterized in that said sandblasting-resistant material of fine particles comprises: gelatin, ammonia dichromate and hot water in roughly proportional quantities h   7 grams, 1 gram and 50 cc respectively.   Microminiature multilayer refrigerator, characterized in that it comprises a laminate formed by at least three thin plates surfaced to be flat and   adhesively sealed to the pressure   at the interfaces between the adjacent plates, means forming in one of the interfaces between two adjacent plates a first continuous flow arrangement extending from an inlet to a cooling chamber, means for connecting said inlet to a gas source. refrigerant under high pressure, means forming in another interface between two adjacent plates another continuous flow arrangement terminating at an outlet, and a passage mutually connecting said chamber and said other passage arrangement whereby a fluid under a reduced pressure in from said cooling chamber may pass through said further passage arrangement to said outlet in heat exchange and counterflow relation to the fluid in said first passage arrangement for a   regenerative pre-cooling, each of those agencies   passages having a size of the order of one micrometer   so that a laminar flow is favored.   Refrigerator according to Claim 6, characterized in that the said plates are thin glass plates of uniform thickness. The refrigerator according to Claim 8, characterized in that the said arrangements of passages   each have a width of about 250   approximately 10 μm, said passage arrangement   a width of about 200 μm and a depth of   10 and the arrangement of output passages at a   width about 15,000 Sm and a depth of about 25 pm.   Refrigerator according to Claim 8, characterized in that the said plates are made of glass and the said chamber is a through opening made in   one of said plates and a block is glued to said opening   thereby ensuring contact with a device to be cooled, said block being of a material which has a higher thermal conductivity than that of the plate   wherein said opening is formed.   12 multilayer refrigerator according to claim   8, characterized by the fact that said cooling chamber   is located substantially centrally in the said stratum   and means provided by which an electrical device to be cooled can be attached directly to an outer plate in substantially direct alignment with said cooling chamber, a circuit arrangement   electrical device for the above-mentioned device being formed on the   adjacent face of said outer plate.   Microminiature cryogenic refrigerator for cooling superconductors or other similar devices, characterized in that it comprises a plurality of elements having substantially the same coefficient of thermal expansion, a means of adhering said elements to one another on   areas of parallel interfaces so as to form a strat-   a means forming a low temperature chamber in said laminate, means forming a fluid supply passage connecting the outside of said refrigerator to said chamber, said passage comprising in series a heat exchange section and a capillary section, a return passage arrangement for conveying fluid from said cooling chamber in heat exchange relation with the fluid   entering into said heat exchange section and an agency   additional passage to carry part of   fluid entering by diverting it from said cooling chamber   and to move said fluid part to the outside.   said refrigerator in heat exchange relation with the incoming fluid present in said heat exchange section. heat.   Refrigerator according to Claim 13, characterized in that the said capillary section comprises two capillary passages in series and the said additional passage arrangement is connected to the said capillary section.   at a point between said capillary passages.   Refrigerator according to Claim 13, characterized in that the said capillary section comprises two capillary passages arranged in parallel and the said additional passage arrangement is connected to the downstream end of one of the said capillary passages.