JPH0545531U - Infrared detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an infrared detector capable of efficiently cooling the infrared detector by reducing the thermal resistance between the infrared detector of the infrared detector and the cap bottom. [Structure] A back cover 10 of aluminum nitride or Invar having a thermal expansion coefficient close to that of the material of the light receiving part 2 of the infrared detecting element 1.
Was directly bonded to the light receiving portion 2 to reduce the thermal resistance between the infrared detecting element 1 and the cap bottom 9.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an infrared detector including a dewar equipped with an element that detects infrared rays and generates a signal, and a cooling device that cools the element.

[0002]

[Prior Art]

 FIG. 2 is a sectional view showing a conventional infrared detecting device. In the figure, 1 is an infrared detection element, 2 is a light receiving section for detecting light in the infrared detection element, 3 is a package for relaying signals from the infrared detection element, and 4 is the infrared detection element 1 mounted thereon. However, in order to provide heat insulation, the inner cylinder of Dewar keeps the inside vacuum, 5 the outer cylinder of Dewar keeps the inside vacuum, 6 the flange connecting the inner cylinder and the outer cylinder, and 7 the inside of the Dewa vacuum. A window that keeps the signal light passing through, 8 a cooler that cools the infrared detection element to a cryogenic temperature, 9 a cap bottom for keeping the inside of the dewar vacuum and transmitting heat from the element to the cooler, 10 a package 3 A back lid that is attached to the cap bottom 9 and also serves as a protection until the infrared detection element 1 is mounted on the dewar, 11 is a cold shield cooled by the cooler 8, and 12 is the infrared detection element 1 and the package. Over di 3, the package 3 and the back cover 10, back cover 10 and the cap bottom 9, and respectively fixed to the package 3 and co over field shield 11, Ru cryogenic adhesive der to conduct heat.

The conventional infrared detection device is configured as described above, and the infrared detection element 1 needs to be cooled to an extremely low temperature because thermal noise adversely affects the sensitivity at normal temperature. For this reason, the infrared detection device has an infrared detection element 1 joined to one end, an open inner cylinder 4 for inserting a cooler 8 at the other end, an outer cylinder 5 closed at one end with a window 7, and the inner cylinder. It has a double-cylinder structure that is sealed by a flange 6 that joins the outer cylinder 4 and the outer cylinder 5. The inside is vacuumed and heat-insulated to reduce the amount of heat penetration from the outside. By inserting the cooler 8 into the inner tube 4 of the infrared detecting device configured as described above and cooling the infrared detecting element 1, the infrared rays passing through the window 7 are detected. The cold shield 11 is cooled to the same extent as the infrared detecting element 1, and the noise light emitted from it is negligibly small. The aperture of the cold shield 11 is an aperture stop for infrared signal light, and has a structure that reduces unnecessary noise light incident from a background at room temperature in addition to the signal light.

[0004]

[Problems to be solved by the device]

 The conventional infrared detection device as described above has the following problems to be solved. That is, in the conventional infrared detection device, heat is cooled by the cooler 8 via the package 3, the back cover 10 and the cap bottom 9 via the cryogenic adhesive 12 to cool the infrared detection element 1. .. At this time, the cross-sectional area of the cryogenic adhesive 12 between the infrared detection element 1 and the package 3 and between the package 3 and the back cover 10 is small, and the thermal conductivity of the cryogenic adhesive 12 is, for example, an epoxy-based adhesive. The adhesive is 0.0002 W / mmK, the thermal conductivity of alumina is 0.16 W / mmK when the package is alumina, and the thermal conductivity of silicon carbide is 0.93 W / m mK when the back cover is silicon carbide. The thermal conductivity of the cryogenic adhesive 12 is much smaller than that.

Therefore, in the conventional infrared detection device, the thermal resistance between the infrared detection element 1 and the cap bottom 9 almost occupies the portion of the cryogenic adhesive 12, and the total thereof is 25 K / W. The amount of heat passing therethrough is the heat generated by the infrared detecting element 1 and the radiant heat that enters the infrared detecting element 1 and the package 3 through the window 7. The heat generating amount of the infrared detecting element 1 is 0.2 W, and the total radiant heat is 0.15 W. It is 0.35W. The temperature difference between the infrared detection element 1 and the cap bottom 9 is the product of the thermal resistance and the amount of heat passing through, and the temperature difference is 25K / W × 0.35W = 8.75K, and the cooler 8 is red. In order to cool the outer line detection element 1 to a predetermined temperature, the cooling temperature of the cooler 8 is a temperature difference between the predetermined cooling temperature of the red line detection element 1 and the infrared detection element 1 and the cap bottom. It had to be cooled down to 75K, which caused a large heat load on the cooler 8.

Therefore, in order to reduce the heat load of the cooler 8 and improve the cooling efficiency, the thermal resistance between the infrared detection element 1 and the cap bottom 9 should be reduced from 1/2 to 1/3 or less of the conventional one to reduce the temperature difference. Must be small. When trying to reduce the thermal resistance, the thermal resistance is determined by the thermal conductivity of the material and the cross-sectional area and thickness of the portion through which heat passes. To reduce the heat resistance, use a material with high thermal conductivity, increase the cross-sectional area of the part through which heat passes, or reduce the thickness. Until now, when trying to reduce the thermal resistance of the cryogenic adhesive, the adhesives that can be used at cryogenic temperatures are limited, so the material cannot be changed and the thickness and adhesive strength must be ensured. It could not be made thin, and it was thought that the cross-sectional area would be increased. In order to increase the cross-sectional area, the infrared detection element 1, the package 3, and the back cover 10 must be enlarged. To make them larger means that the part that must be cooled by the cooler 8 becomes larger, and the heat capacity of the part to be cooled becomes larger, so that the infrared detection element 1 reaches a predetermined cooling temperature from room temperature. The problem that the time becomes long occurs. In addition, as the package 3 and the like become larger, radiant heat also increases, which has an adverse effect on the cooler 8.

The present invention has been made in order to solve such a problem, and by changing the conventional mounting method of the infrared ray detecting element, the thermal resistance between the infrared ray detecting element and the cap bottom is reduced as much as possible, The purpose is to reduce the heat load on the cooler and obtain an infrared detector with good cooling efficiency.

[0008]

[Means for Solving the Problems]

 In the infrared detecting device according to the present invention, the back cover is directly bonded to the light receiving portion of the infrared detecting element to reduce the thermal resistance between the infrared detecting element and the cap bottom, thereby reducing the heat load of the cooler and cooling efficiency. It is intended to improve.

[0009]

[Action]

 In this invention, by bonding the back cover directly to the light receiving part of the infrared detecting element, the cross-sectional area of the back cover is large, and there have been three bonding parts through which heat passes up to now, and there are two rollers. The thermal resistance between the sensing element and the cap bottom can be significantly reduced, and the heat load of the cooler can be reduced and the cooling efficiency can be improved. As a result, an infrared detection device with good cooling efficiency can be obtained.

[0010]

【Example】

Example 1. FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, 1 is an infrared detecting element, 3 is a package, 4 is an inner cylinder, 5 is an outer cylinder, 6 is a flange, 7 is a window, 8 is a cooler, 9 is a cap bottom, and 11 is a cold shield. It is the same as the device. In addition to the package 3, the back cover 10 is bonded to the light receiving section 2 with a cryogenic adhesive 12. At this time, it should be noted that the light receiving part 2 and the back cover 10 are cooled from room temperature to extremely low temperature, so that the thermal expansion coefficient of each member should be selected to reduce the thermal stress generated. It should be made as small as possible so that the light receiving part 2 is not cracked or electrically affected. For example, when platinum silicon is used for the light receiving part, its thermal expansion coefficient is 11 × 10 ⁷ / ° C., and the back lid 10 has aluminum thermal expansion coefficient of 13 × 10 ⁷ / ° C. or 18 × 10 ⁷ / ° C. Use Inver. As a result, the cross-sectional area through which heat passes increases by 2.4 times as compared with the conventional method, and since there are two bonding parts through which heat passes, there are two bonding parts, so that there is a gap between the infrared sensing element 1 and the cap bottom 9. The thermal resistance is 25K / W ÷ 2.4 ÷ 1.5 = 7K / W, and the amount of heat passing therethrough is 0.35W, which is the same as the conventional one, so the temperature difference between the infrared detection element 1 and the cap bottom 9 Is 7K / W × 0.35W = 2.45K, which is 1/3 or less of the conventional 8.75K, and the heat load of the cooler can be reduced.

In the infrared detecting device configured as described above, the heat of the infrared detecting element 1 is transferred from the light receiving portion 2 through the cryogenic adhesive 12 to the cooler 8 via the back lid 10 and the cap bottom 9. To be cooled. The bonding area between the light receiving portion 2 and the back cover 10 is larger than that of the conventional device, and the heat resistance is small because there are two bonding portions through which heat passes. Therefore, the heat load on the cooler 8 is reduced, and an infrared detection device with good cooling efficiency can be obtained.

[0012]

[Effect of the device]

 According to this invention, by bonding the back cover directly to the light receiving part of the infrared detection element, the thermal resistance between the infrared detection element and the cap bottom becomes small, and the temperature difference between the infrared detection element and the cooler becomes small, so that the heat of the cooler is reduced. Since the load is reduced, it is possible to obtain an infrared detection device with good cooling efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional infrared detection device.

[Explanation of symbols]

 1 Infrared Detector 2 Light Receiver 3 Package 4 Inner Tube 5 Outer Tube 6 Flange 7 Window 8 Cooler 9 Cap Bottom 10 Back Cover 11 Cold Shield 12 Cryogenic Adhesive

Claims (1)

[Scope of utility model registration request] 1. A dewar having a window for transmitting signal light to be detected and having a vacuum inside, an infrared detecting element, a cold shield and a cap bottom installed in the dewar, and a package for mounting the infrared detecting element. A back lid for attaching this package to the cap bottom, and an infrared detection device including a cooler for cooling the infrared detection element, the back lid is directly bonded to the light receiving portion of the infrared detection element. Infrared detector featuring.