An abnormal bonding surface structure of a Dewar cold shield and its encapsulation method

Abstract

The present invention discloses a special-shaped bonding surface structure of a Dewar cold shield and its encapsulation method. The structure includes a Dewar cold shield and a bonding surface for bonding the Dewar cold shield to a loading substrate. The bonding surface is formed by alternately connecting a planar section and a corrugated surface section along the circumference. The corrugated surface section is used for adhesive bonding and fixing with the loading substrate, and the planar section is used for support and installation positioning. By dividing the bonding surface structure of the cold shield according to different functions of enhancing the bonding strength and installation positioning accuracy of the cold shield, the present invention can enable the cold shield to be compatible with the functions of support, positioning, and adhesive bonding and fixing, meet the requirements of the encapsulation accuracy of the cold shield, make the encapsulation inclination angle of the cold shield controllable, and improve the efficiency of the cold shield.

Description

Technical Field

[0001] The present invention belongs to the technical field of infrared detectors, and particularly relates to a special-shaped bonding surface structure of a Dewar cold shield and its encapsulation method. Background Art

[0002] The bonding surface structure design of Dewar cold shields all adopts a planar design (as shown in Figure 1 ). The three functions of support, positioning, and bonding and fixing are simultaneously realized on the cold shield bonding surface. When bonding the cold shield, first, the bonding adhesive is coated on the cold shield bonding surface (as shown in Figure 2 ), the cold shield is placed on the loading substrate, and rough alignment of the cold shield is achieved under a microscope to complete the preliminary bonding of the cold shield; then, the positions of the cold shield in the X and Y directions are adjusted through a tool microscope to achieve fine alignment of the cold shield; finally, the bonding adhesive is cured to attach the cold shield to the Dewar cold head (as shown in Figure 3 ).

[0003] The existing bonding surface of the Dewar cold shield is a planar structure design. The same cold shield bonding surface needs to be compatible with the three functions of support, positioning, and bonding and fixing. Specifically, the support function supports the cold shield to be installed on the loading substrate, the positioning function ensures high-precision positioning of the cold shield in the X, Y, and Z directions, and the bonding and fixing function ensures the reliability of the cold shield installation.

[0004] At this time, the contact surface between the cold shield and the loading substrate is all connected by the bonding adhesive (as shown in Figure 4 ). The bonding adhesive has a certain thickness and fluidity, and the uniformity of the adhesive layer is uncontrollable. The non-uniformity of the adhesive layer after curing will affect the bonding accuracy of the cold shield in the Z-axis direction. Moreover, the thermal expansion coefficients of the cold shield, loading substrate, and bonding adhesive of the refrigerated detector need to be similar to ensure that the detector performance requirements are still met during low-temperature operation. Therefore, it is very difficult to simultaneously achieve the three functions on the cold shield bonding plane, and there is no third method in the industry's cold shield bonding surface structure design that can be compatible with the three functions at the same time.

[0005] In summary, when the cold shield bonding surface structure is planar, the three functions cannot be compatible at the same time. The accuracy in the Z-axis direction cannot be guaranteed, and whether the thermal expansion coefficient of the bonding adhesive is similar to that of the cold shield directly affects the bonding reliability of the cold shield. Summary of the Invention

[0006] Aiming at the problems existing in the above-mentioned infrared detector Dewar cold shield structure design, the present invention proposes a special-shaped cold shield bonding surface structure combining a plane and a corrugation and its encapsulation method. The cold shield bonding surface structure of the present invention can control the bonding accuracy of the cold shield in the Z direction through mechanical processing accuracy, ensure that the bonding inclination angle of the cold shield is controllable, improve the encapsulation accuracy of the cold shield, and thus improve the cold shield efficiency.

[0007] Specifically, the technical solution of the present invention is as follows:

[0008] An abnormal bonding surface structure of a Dewar cold shield, including a Dewar cold shield and a bonding surface for bonding the Dewar cold shield to a loading substrate. The bonding surface is formed by alternately connecting a flat section and a corrugated section along the circumferential direction. The corrugated section is used for adhesive bonding and fixing with the loading substrate, and the flat section is used for supporting and mounting positioning. When it is necessary to improve reliability and enhance the bonding strength of the cold shield, the proportion of the corrugated section can be increased; when it is necessary to improve the installation and positioning accuracy of the cold shield, the proportion of the flat section can be increased.

[0009] Furthermore, the arc length ratio of the flat section and the corrugated section projected on the loading substrate is greater than or equal to 1:1.

[0010] The cold shield encapsulation method of an abnormal cold shield bonding surface structure of the present invention includes:

[0011] (1) When encapsulating the cold shield, first apply an adhesive on the inner bonding surface of the cold shield side wall. This adhesive is used for bonding and fixing the inner bonding surface of the cold shield to the ceramic ring of the loading substrate to improve the bonding reliability of the cold shield;

[0012] (2) The cold shield is a machined part. When the parallelism of the cold shield support plane ≤ 0.02 and the parallelism of the matching surface of the loading substrate ≤ 0.03, the cold shield is fixed on the loading substrate, and no adhesive is applied on the support plane. Only mechanical errors need to be considered. When the parallelism of the cold shield support plane ≤ 0.05, the inclination angle of the cold shield in the Z direction is controllable at this time. This installation method where the cold shield support plane is in direct contact with the loading substrate improves the encapsulation accuracy of the cold shield. After confirming the encapsulation accuracy of the cold shield in the Z direction, first perform rough centering on the X and Y directions of the cold shield. The rough centering is used to complete the centering of the assembly direction and assembly position of the cold shield; then, perform fine centering on the X and Y directions of the cold shield under the microscope. The fine centering is used to complete the installation accuracy control of the cold shield in the X and Y directions.

[0013] (3) Fill the voids in the corrugated section with adhesive to bond and fix the cold shield. After the adhesive cures, additional adhesive can be applied for reinforcement at the outer edge of the cold shield. The cold shield bonding surface structure with a mixture of the flat section and the corrugated section 7 can control the bonding accuracy of the cold shield in the X, Y, and Z directions while ensuring the bonding strength of the cold shield, improve the encapsulation accuracy of the cold shield, and thus improve the cold shield efficiency.

[0014] Advantages of the present invention:

[0015] By dividing the cold shield bonding surface structure according to different functions of enhancing the bonding strength and installation and positioning accuracy of the cold shield, the present invention can enable the cold shield to be compatible with the functions of support, positioning, and bonding and fixing, meet the requirements of cold shield encapsulation accuracy, make the encapsulation inclination angle of the cold shield controllable, and improve the cold shield efficiency. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the planar structure of the existing cold shield bonding surface.

[0017] Figure 2 is the position of the bonding surface between the current cold shield and the substrate.

[0018] Figure 3 is a schematic diagram of the cold shield mounted on the Dewar cold head.

[0019] Figure 4 is a schematic diagram of the position of the encapsulation bonding adhesive for the current cold shield.

[0020] Figure 5 is a schematic diagram of the bonding surface structure of the special-shaped cold shield.

[0021] Figure 6 is the position of the cold shield reinforcement adhesive; among them: (a) inner wall reinforcement of the cold shield, (b) outer edge reinforcement of the cold shield.

[0022] Figure 7 is the flow chart of the cold shield bonding alignment.

[0023] In the figure: 1 - planar structure of the bonding surface, 2 - bonding surface, 3 - cold shield, 4 - loading substrate, 5 - adhesive layer, 6 - planar section, 7 - corrugated surface section, 8 - bonding adhesive, 9 - inner bonding surface of the cold shield, 10 - ceramic ring of the loading substrate, 11 - edge of the cold shield. Specific embodiments

[0024] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the present invention will be described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0025] As Figure 5 shown, a structure of the bonding surface of a special-shaped cold shield is formed by alternately connecting a planar section 6 and a corrugated surface section 7 to form a complete mounting surface of the cold shield, and the distribution ratio of the planar section 6 and the corrugated surface section 7 can be adjusted; the planar section 6 plays a role in support and positioning, and the corrugated surface section 7 plays a role in adhesive bonding and fixing; in the case of needing to improve reliability and enhance the bonding strength of the cold shield, the ratio of the corrugated surface section 7 can be increased; in the case of needing to improve the mounting and positioning accuracy of the cold shield, the ratio of the planar section 6 can be increased.

[0026] By dividing the bonding surface structure of the cold shield according to different functions of enhancing the bonding strength and mounting and positioning accuracy of the cold shield, the present invention can make the cold shield compatible with the functions of support, positioning, and adhesive bonding and fixing, meet the requirements of the cold shield encapsulation accuracy, and improve the cold shield efficiency.

[0027] As Figure 6 shown, the cold shield encapsulation method includes:

[0028] (1) When encapsulating the cold shield 3, first apply the bonding adhesive 8 to the inner bonding surface 9 of the side wall of the cold shield. This bonding adhesive 8 is used for bonding and fixing the inner bonding surface 9 of the cold shield and the ceramic ring 10 of the loading substrate, so as to improve the bonding reliability of the cold shield 3;

[0029] (2) The cold shield is a machined part. When the parallelism of the support plane of the cold shield is ≤ 0.02 and the parallelism of the mating surface of the loading substrate 4 is ≤ 0.03, the cold shield is fixed on the loading substrate 4, and no adhesive is applied to the support plane. Only mechanical errors need to be considered. When the parallelism of the support plane of the cold shield is ≤ 0.05, the inclination angle of the cold shield in the Z direction is controllable at this time. This installation method where the support plane of the cold shield is in direct contact with the loading substrate 4 improves the packaging accuracy of the cold shield. After the packaging accuracy of the cold shield in the Z direction is confirmed, first perform rough alignment in the X and Y directions of the cold shield. The rough alignment is used to complete the alignment of the assembly direction and assembly position of the cold shield. Then, complete the fine alignment in the X and Y directions of the cold shield under the microscope. The fine alignment is used to complete the control of the installation accuracy of the cold shield in the X and Y directions.

[0030] (3) Fill the voids in the corrugated surface section 7 with the adhesive 8 to bond and fix the cold shield. After the adhesive 8 cures, additional adhesive can be applied to reinforce the outer edge 11 of the cold shield. The cold shield bonding surface structure that combines the flat section 6 and the corrugated surface section 7 can control the bonding accuracy of the cold shield in the X, Y, and Z directions while ensuring the bonding strength of the cold shield, improving the packaging accuracy of the cold shield, and thus enhancing the cold shield efficiency.

Claims

1. A cold shield encapsulation method for a special-shaped bonding surface structure of a Dewar cold shield, characterized in that, The special-shaped bonding surface structure of the Dewar cold shield includes the Dewar cold shield (3) and a bonding surface (2) for bonding the Dewar cold shield (3) to the loading substrate (4). The bonding surface (2) is formed by alternately connecting a flat section (6) and a corrugated section (7) along the circumferential direction. The corrugated section (7) is used for adhesive bonding and fixing with the loading substrate (4), and the flat section (6) is used for support and installation positioning. When it is necessary to improve reliability and enhance the bonding strength of the Dewar cold shield (3), the proportion of the corrugated section (7) is increased. When it is necessary to improve the installation and positioning accuracy of the Dewar cold shield (3), the proportion of the flat section (6) is increased. The cold shield encapsulation method includes the following steps: Step 1, when encapsulating the Dewar cold shield (3), first apply an adhesive (8) on the inner bonding surface (9) of the cold shield. This adhesive (8) is used to bond and fix the inner bonding surface (9) of the cold shield to the loading substrate ceramic ring (10) to improve the bonding reliability of the Dewar cold shield (3). Step 2, when the parallelism of the cold shield support plane ≤ 0.05, at this time the inclination angle of the cold shield in the Z direction is controllable, and the cold shield support plane and the loading substrate (4) adopt a direct contact installation method to improve the encapsulation accuracy of the cold shield. Step 3, after confirming the Z-direction encapsulation accuracy of the Dewar cold shield (3), first perform rough centering on the Dewar cold shield (3) in the X and Y directions. The rough centering is used to complete the centering of the assembly direction and assembly position of the Dewar cold shield (3). Then, under the microscope, complete the fine centering of the Dewar cold shield (3) in the X and Y directions. The fine centering is used to complete the control of the installation accuracy of the Dewar cold shield (3) in the X and Y directions. Step 4, fill the voids in the corrugated section (7) with the adhesive (8) to bond and fix the Dewar cold shield (3).

2. The cold shield encapsulation method according to claim 1, wherein: The arc length ratio of the projection of the flat section (6) and the corrugated section (7) on the loading substrate (4) is greater than or equal to 1:

1.

3. The cold shield encapsulation method according to claim 2, wherein: The arc length ratio of the projection of the flat section (6) and the corrugated section (7) on the loading substrate (4) is 1:

1.

4. The cold screen encapsulation method according to claim 1, characterized in that, It further includes: Step 5, after the adhesive (8) is cured, apply additional glue for reinforcement at the outer edge (11) of the cold shield.

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