CN111024235B - Infrared focal plane supporting structure with thermal stress unloading function - Google Patents

Abstract

The invention discloses an infrared focal plane support structure with thermal stress unloading function, comprising: a detector readout circuit, a substrate, a support structure, a cold head, a cold finger and a flexible unloading heat-conducting wire; wherein, the detector reads out The circuit is bonded on the substrate; the substrate is bonded on the support structure; the support structure is mounted on the cold head; the cold finger is connected with the cold head; the flexible unloading thermal wire is arranged on the inside the support structure. The invention solves the problems of efficient heat conduction and thermal stress and thermal deformation of the infrared focal plane assembly.

Description

An infrared focal plane support structure with thermal stress unloading function

technical field

The invention belongs to the technical field of focal plane support structures of space remote sensors, and in particular relates to an infrared focal plane support structure with thermal stress unloading function.

Background technique

In recent years, with the continuous development of space infrared cameras, infrared detectors have developed from single-unit, few-element, multi-element line arrays to multi-element area arrays, long line arrays, and large area arrays, promoting infrared detection technology from point targets to scanning imaging, pushing From scanning imaging to gaze imaging. At present, multi-piece detector splicing technology is widely used to meet the requirements of use, and the size of the focal plane can reach 100-300 mm.

Flip-chip interconnect welding focal method is one of the main methods of detector integration. The mercury cadmium telluride photosensitive element chip is interconnected and coupled with the readout circuit chip to form a focal plane detector. The detector is then bonded to the splice substrate (sapphire, silicon carbide, silicon, etc. can be selected as the base material), and then bonded to the focal plane support structure. The support structure connects the focal plane substrate and the cold head of the refrigerator, and the cold head is generally made of copper, molybdenum copper and other materials. A variety of materials are integrated or assembled together at normal temperature, and thermal deformation and thermal stress are inevitably generated when working at low temperature. The main functions of the support structure are: 1) efficiently transfer the cooling energy of the cold head to the focal plane; 2) reduce the thermal deformation of the focal plane, reduce the thermal stress of the detector, and ensure the flatness of the focal plane.

Infrared detectors need to reduce thermal noise by means of cooling, and usually need to have good imaging performance at low temperatures (55K ~ 120K). Detector components are assembled at room temperature. During the cooling process, thermal stress and deformation will occur due to the difference in thermal expansion coefficient of materials, which may cause the photosensitive surface of the detector to be non-coplanar or even break the detector, which seriously affects the imaging quality and component reliability.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to overcome the deficiencies of the prior art, provide an infrared focal plane support structure with thermal stress unloading function, and solve the problems of efficient heat conduction, thermal stress and thermal deformation of the infrared focal plane assembly.

The object of the present invention is achieved through the following technical solutions: an infrared focal plane support structure with thermal stress unloading function, comprising: a detector readout circuit, a substrate, a support structure, a cold head, a cold finger and a flexible unloading heat conducting wire; wherein, the detector readout circuit is bonded on the substrate; the substrate is bonded on the support structure; the support structure is mounted on the cold head; the cold finger is connected with the cold head; the flexible The unloading thermal wire is arranged in the support structure.

In the above infrared focal plane support structure with thermal stress unloading function, the support structure is a flat plate, wherein the lower surface of the flat plate is provided with an H-type cold finger adhesive surface; the upper surface of the flat plate is provided with a first detector substrate side adhesive surface. a junction surface, a second detector substrate side bonding surface, a third detector substrate side bonding surface, a fourth detector substrate side bonding surface and a flexible heat transfer area; wherein the first detector substrate side bonding surface and The bonding surfaces on the side of the second detector substrate are opposite, and the bonding surfaces on the side of the first detector substrate and the side of the second detector substrate are both located at the outer edge of the upper surface of the flat plate; The adhesive surfaces on the side of the fourth detector substrate are opposite to each other, and the adhesive surfaces on the side of the third detector substrate and the side of the fourth detector substrate are both located at the outer edge of the upper surface of the flat plate; the flexible heat transfer area is located on the upper surface of the flat plate. In the middle position, the flexible unloading thermal wire is arranged in the flexible heat transfer area.

In the above-mentioned infrared focal plane support structure with thermal stress unloading function, the upper surface of the flat plate is provided with a through slot X1, a through slot X2, a through slot X3, a through slot X4, a non-through slot X5, a non-through slot X6, and a non-through slot Y1. and non-penetrating groove Y2; wherein, the penetration groove X1, penetration groove X2, penetration groove X3, penetration groove X4, non penetration groove X5, non penetration groove X6, non penetration groove Y1 and non penetration groove Y2 are located in the H-type cold finger bonding At the boundary position of the surface; the non-penetrating groove X5 is opposite to the non-penetrating groove X6, and the non-penetrating groove X5 and the non-penetrating groove X6 are parallel; the penetration groove X1 is opposite to the penetration groove X2, and the penetration groove X1 and the penetration groove X2 are parallel; The through grooves X4 are opposite, the through grooves X3 and X4 are parallel; the non-through grooves Y1 and the non-through grooves Y2 are opposite, and the non-through grooves Y1 and the non-through grooves Y2 are parallel.

In the above-mentioned infrared focal plane support structure with thermal stress unloading function, the lower surface of the flat plate is provided with a non-penetrating groove X7, a non-penetrating groove X8, a non-penetrating groove Y3, a non-penetrating groove Y4, a non-penetrating groove Y5 and a non-penetrating groove Y6; The non-penetrating groove X7 is located on the inner boundary of the bonding surface 1 on the first detector substrate side, the non-penetrating groove X8 is located on the inner boundary of the bonding surface 2 on the second detector substrate side, and the non-penetrating groove Y3 is located on the third detector substrate. The inner boundary of the side bonding surface 3, the non-penetrating groove Y4 is located at the inner boundary of the bonding surface 4 on the fourth detector substrate side, the non-penetrating groove Y5 is located at the center of the bonding surface 1 on the first detector substrate side, and the non-penetrating groove Y5 is located at the center of the bonding surface 1 on the first detector substrate side. Y6 is located at the center of the bonding surface 2 on the substrate side of the second detector.

In the above infrared focal plane support structure with thermal stress unloading function, the flat plate is provided with a non-penetrating groove Z1, a non-penetrating groove Z2, a non-penetrating groove Z3, and a non-penetrating groove Z4; the non-penetrating groove Z1 is located on the side of the third detector substrate for bonding. The left boundary of the surface 3 is located at 1/3-1/2 along the thickness direction; the non-penetrating groove Z3 is located at the 1/3-1/2 position along the thickness direction of the left boundary of the bonding surface 4 on the substrate side of the fourth detector; the non-penetrating groove Z2 is located at 1/3-1/2 of the right boundary of the bonding surface 3 on the third detector substrate side along the thickness direction; the non-penetrating groove Z4 is located at the right boundary of the bonding surface 4 on the fourth detector substrate side along the thickness direction 1/3 3 to 1/2 position.

In the above infrared focal plane support structure with thermal stress unloading function, the coordinate system takes the intersection of the long side and the short side of the lower surface of the flat plate as the origin, the long side is the X direction, the short side is the Y direction, and the thickness direction is the Z direction.

Compared with the prior art, the present invention has the following beneficial effects:

1) The present invention fully unloads the thermal stress at the infrared focal plane through three unloading grooves in the X, Y, and Z directions to ensure the imaging quality;

2) The present invention fully transmits the cooling capacity of the refrigerator to the detector through the flexible heat transfer area composed of the flexible heat transfer wire, which ensures the uniform transmission of the ambient temperature and temperature imaged by the detector, and at the same time, the flexible structure does not cause stress concentration. .

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be considered limiting of the invention. Also, the same components are denoted by the same reference numerals throughout the drawings. In the attached image:

1 is a cross-sectional view of an infrared focal plane support structure with thermal stress unloading function provided by an embodiment of the present invention;

2 is an exploded view of an infrared focal plane support structure with thermal stress unloading function provided by an embodiment of the present invention;

3 is a schematic diagram of a support structure provided by an embodiment of the present invention;

4 is another schematic diagram of a support structure provided by an embodiment of the present invention;

5 is another schematic diagram of a support structure provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of a simulation result of a support structure provided by an embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly understood, and will fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

FIG. 1 is a cross-sectional view of an infrared focal plane support structure with thermal stress unloading function provided by an embodiment of the present invention. FIG. 2 is an exploded view of an infrared focal plane support structure with thermal stress unloading function provided by an embodiment of the present invention. As shown in FIG. 1 and FIG. 2 , the infrared focal plane support structure includes a detector readout circuit 100, a substrate 200, a support structure 300, a cold head 400, a cold finger 500 and a flexible unloading thermal wire 600; wherein,

The detector readout circuit 100 is bonded to the substrate 200; the substrate 200 is bonded to the support structure 300; the support structure 300 is mounted on the cold head 400; The heads 400 are connected; the flexible unloading thermal wire 600 is arranged in the support structure 300 .

FIG. 3 is a schematic diagram of a support structure provided by an embodiment of the present invention. As shown in FIG. 3 , the support structure 300 is a flat plate, wherein the lower surface of the flat plate is provided with an H-type cold finger bonding surface; the upper surface of the flat plate is provided with a first detector substrate side bonding surface 1 and a second detector substrate Side bonding surface 2, third detector substrate side bonding surface 3, fourth detector substrate side bonding surface 4 and flexible heat transfer area; wherein, the first detector substrate side bonding surface 1 and the second detector The substrate-side adhesive surfaces 2 are opposite to each other, and the first detector substrate-side adhesive surfaces 1 and the second detector substrate-side adhesive surfaces 2 are both located at the outer edge of the upper surface of the flat plate; the third detector substrate-side adhesive surfaces 3 and The fourth detector substrate side bonding surface 4 is opposite to each other, the third detector substrate side bonding surface 3 and the fourth detector substrate side bonding surface 4 are both located at the outer edge of the upper surface of the flat plate; the flexible heat transfer area is located on the outer edge of the flat plate. In the middle position of the upper surface, the flexible unloading thermal wire 600 is arranged in the flexible heat transfer area.

As shown in FIG. 3 , the upper surface of the flat plate is provided with through grooves X1, through grooves X2, through grooves X3, through grooves X4, non-through grooves X5, non-through grooves X6, non-through grooves Y1 and non-through grooves Y2; wherein, Through groove X1, through groove X2, through groove X3, through groove X4, non-through groove X5, non-through groove X6, non-through groove Y1 and non-through groove Y2 are located at the boundary position of the H-type cold finger bonding surface; The groove X5 is opposite to the non-penetrating groove X6, the non-penetrating groove X5 is parallel to the non-penetrating groove X6; the penetration groove X1 is opposite to the penetration groove X2, the penetration groove X1 is parallel to the penetration groove X2; the penetration groove X3 is opposite to the penetration groove X4, and the penetration groove X3 It is parallel to the through groove X4; the non-penetrating groove Y1 and the non-penetrating groove Y2 are opposite, and the non-penetrating groove Y1 and the non-penetrating groove Y2 are parallel. The penetrating groove X1, the penetrating groove X2, the penetrating groove X3, the penetrating groove X4, the non-penetrating groove X5, the non-penetrating groove X6, the non-penetrating groove Y1 and the non-penetrating groove Y2 are used to relieve the thermal stress in the X and Y directions.

As shown in FIG. 5 , a non-penetrating groove X7, a non-penetrating groove X8, a non-penetrating groove Y3, a non-penetrating groove Y4, a non-penetrating groove Y5 and a non-penetrating groove Y6 are formed on the lower surface of the flat plate; A non-penetrating groove X8 is located at the inner boundary of the bonding surface 1 on the substrate side of the detector, and the non-penetrating groove Y3 is located at the inner boundary of the bonding surface 3 on the substrate side of the third detector. , the non-penetrating groove Y4 is located at the inner boundary of the bonding surface 4 on the fourth detector substrate side, the non-penetrating groove Y5 is located at the center of the bonding surface 1 on the first detector substrate side, and the non-penetrating groove Y6 is located on the second detector substrate side The center position of the bonding surface 2. The non-penetrating groove X7, the non-penetrating groove X8, the non-penetrating groove Y3, the non-penetrating groove Y4, the non-penetrating groove Y5 and the non-penetrating groove Y6 are used to relieve the thermal stress in the X and Y directions.

FIG. 4 is another schematic diagram of a support structure provided by an embodiment of the present invention. As shown in FIG. 4 , the flat plate is provided with a non-penetrating groove Z1, a non-penetrating groove Z2, a non-penetrating groove Z3 and a non-penetrating groove Z4; the non-penetrating groove Z1 is located on the left boundary of the bonding surface 3 on the substrate side of the third detector along the thickness direction 1/3~1/2 position; non-penetrating groove Z3 is located at 1/3~1/2 position along the thickness direction of the left boundary of the bonding surface 4 on the fourth detector substrate side; non-penetrating groove Z2 is located on the third detector substrate side The right boundary of the bonding surface 3 is located at 1/3-1/2 position along the thickness direction; the non-penetrating groove Z4 is located at 1/3-1/2 position along the thickness direction of the right boundary of the bonding surface 4 on the fourth detector substrate side. The non-penetrating groove Z1, the non-penetrating groove Z2, the non-penetrating groove Z3, and the non-penetrating groove Z4 are used to relieve the thermal stress in the Z direction.

The coordinate system takes the intersection of the long side and the short side of the lower surface of the plate (the side of the cold head bonding surface) as the origin, the long side is the X direction, the short side is the Y direction, and the thickness direction is the Z direction

The working principle of the infrared focal plane support structure is as follows: in the process of cooling, the cold head and the support structure are made of the same material (molybdenum copper, copper and other materials), and the thermal expansion coefficient is larger than that of the substrate, which will cause convex deformation. The upward convex stress is decomposed into forces in three directions of X, Y, and Z. A stress relief groove is set for each direction of force, and a stress relief fillet is designed in the stress concentration area at the root of the groove. By passing through the support structure, the thermal stress in the middle is unloaded at the middle groove; the thermal stress on the concave part around it is unloaded by the annular unloading groove. The substrate itself has high hardness, which can also improve the deformation of the bonding surface of the silicon wafer.

In addition, in the process of cooling the cold finger, on the one hand, mechanical vibration or pressure gas fluctuation will be generated, and the vibration will be transmitted to the focal plane of the detector along with the cold finger, which will affect the imaging quality of the focal plane in severe cases. The support structure in the present invention prolongs the transmission path of the vibration, thereby reducing the vibration at the detector; on the other hand, the small contact area between the support structure and the substrate is not conducive to the transmission of cooling energy. A filament structure with good damping characteristics and high thermal conductivity (copper foil, copper wire, indium wire and other materials can be selected) is bonded to the central groove of the support structure, which effectively reduces the thermal resistance and ensures sufficient contact area to transfer cooling.

The support structure is simulated and analyzed by Patran software, and the results are shown in Figure 6. The stress concentration area is in the unconstrained area at the four corners (cold finger side), the stress of the coupling substrate is small, and the stress distribution is uniform, and there is no large stress concentration. Among them, the central area is the bonding position of the detector chip. It can be seen from the simulation results that the stress in the direction of the center gradually decreases, and the force directly acting on the device is small, which achieves the purpose of stress unloading.

The present invention fully unloads the thermal stress on the infrared focal plane through three unloading grooves of X, Y and Z directions to ensure imaging quality; The cooling energy of the machine is fully transmitted to the detector, which ensures the uniform transmission of the ambient temperature and temperature imaged by the detector, and the flexible structure will not cause stress concentration.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can use the methods and technical contents disclosed above to improve the present invention without departing from the spirit and scope of the present invention. The technical solutions are subject to possible changes and modifications. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention belong to the technical solutions of the present invention. protected range.

Claims (4)

1. An infrared focal plane support structure with thermal stress unloading function, characterized by comprising: a detector readout circuit (100), a substrate (200), a support structure (300), a cold head (400), a cold finger ( 500) and a flexible unloading thermal wire (600); wherein, The detector readout circuit (100) is bonded on the substrate (200); the substrate (200) is bonded on the support structure (300); the support structure (300) is mounted on the cold head (400); The cold finger (500) is connected with the cold head (400); The flexible unloading heat conducting wire (600) is arranged in the support structure (300); The support structure (300) is a flat plate, wherein the lower surface of the flat plate is provided with an H-type cold finger bonding surface; the upper surface of the flat plate is provided with a first detector substrate side bonding surface (1), a second detector substrate a side bonding surface (2), a third detector substrate side bonding surface (3), a fourth detector substrate side bonding surface (4) and a flexible heat transfer area; wherein, the first detector substrate side bonding surface (1) Opposite to the second detector substrate side bonding surface (2), the first detector substrate side bonding surface (1) and the second detector substrate side bonding surface (2) are both located on the upper surface of the flat plate Outer edge; the third detector substrate side bonding surface (3) is opposite to the fourth detector substrate side bonding surface (4), the third detector substrate side bonding surface (3) and the fourth detector substrate side bonding surface The junction surfaces (4) are all located at the outer edge of the upper surface of the flat plate; the flexible heat transfer area is located in the middle of the upper surface of the flat plate, and the flexible unloading heat conduction wire (600) is arranged in the flexible heat transfer area; The upper surface of the flat plate is provided with through grooves X1, through grooves X2, through grooves X3, through grooves X4, non-through grooves X5, non-through grooves X6, non-through grooves Y1 and non-through grooves Y2; wherein, through grooves X1, through grooves X2, penetrating groove X3, penetrating groove X4, non-penetrating groove X5, non-penetrating groove X6, non-penetrating groove Y1 and non-penetrating groove Y2 are located at the boundary position of the H-type cold finger bonding surface; non-penetrating groove X5 and non-penetrating groove X6 is opposite, non-penetrating groove X5 and non-penetrating groove X6 are parallel; penetration groove X1 is opposite to penetration groove X2, penetration groove X1 and penetration groove X2 are parallel; penetration groove X3 is opposite to penetration groove X4, penetration groove X3 and penetration groove X4 are parallel; The non-penetrating groove Y1 and the non-penetrating groove Y2 are opposed to each other, and the non-penetrating groove Y1 and the non-penetrating groove Y2 are parallel. 2. The infrared focal plane support structure with thermal stress unloading function according to claim 1, wherein the lower surface of the flat plate is provided with a non-penetrating groove X7, a non-penetrating groove X8, a non-penetrating groove Y3, and a non-penetrating groove Y4 , non-penetrating groove Y5 and non-penetrating groove Y6; among them, The non-penetrating groove X7 is located on the inner boundary of the bonding surface (1) on the first detector substrate side, the non-penetrating groove X8 is located on the inner boundary of the bonding surface (2) on the second detector substrate side, and the non-penetrating groove Y3 is located on the third detector substrate side. The inner boundary of the bonding surface (3) on the side of the detector substrate, the non-penetrating groove Y4 is located on the inner boundary of the bonding surface (4) on the side of the fourth detector substrate, and the non-penetrating groove Y5 is located on the bonding surface (1) on the side of the first detector substrate. ), and the non-penetrating groove Y6 is located at the center of the bonding surface (2) on the substrate side of the second detector. 3. The infrared focal plane support structure with thermal stress unloading function according to claim 2, wherein the flat plate is provided with a non-penetrating groove Z1, a non-penetrating groove Z2, a non-penetrating groove Z3, and a non-penetrating groove Z4; The groove Z1 is located at the position of 1/3 to 1/2 along the thickness direction of the left boundary of the adhesive surface (3) on the substrate side of the third detector; the non-penetrating groove Z3 is located on the left boundary of the adhesive surface (4) on the substrate side of the fourth detector 1/3-1/2 along the thickness direction; the non-penetrating groove Z2 is located at the right boundary of the bonding surface (3) on the substrate side of the third detector along the thickness direction 1/3-1/2 position; the non-penetrating groove Z4 is located in the The right boundary of the bonding surface (4) on the substrate side of the four-detector is along the position of 1/3 to 1/2 in the thickness direction. 4. The infrared focal plane support structure with thermal stress unloading function according to claim 3, wherein the coordinate system takes the intersection of the long side and the short side of the lower surface of the flat plate as the origin, the long side is the X direction, and the short side is Y direction, thickness direction is Z direction.

Images