Methods for alleviating stress release during ceramic packaging

Abstract

The present invention provides a method for relieving stress release in a ceramic packaging process, which belongs to the field of ceramic packaging technology, and includes a chassis, a ceramic body arranged on the chassis, and a wall arranged on the chassis, wherein the ceramic body is placed at one end of the chassis, and one end of the wall is provided with an opening for arranging the ceramic body, and one end of the wall connected to the ceramic body and the chassis is provided with a stress relief groove extending along the joint, and the stress relief groove is arranged on the inner wall surface of the wall, and the stress relief groove is close to the inner wall of the ceramic body and the chassis and coincides with the contact surface of the ceramic body and the chassis, and the groove bottom of the stress relief groove is lower than the inner wall surface of the wall. The method for relieving stress release in a ceramic packaging process provided by the present invention adds a stress relief groove at a sensitive position where the wall is welded to the ceramic part and the chassis, and absorbs part of the residual stress by accumulating solder, so that the ceramic stress point is away from the structural weak point, thereby alleviating the failure caused by the mismatch of thermal expansion coefficients during the packaging process of ceramic and metal parts.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic packaging, and more specifically, relates to a method for alleviating stress release in a ceramic packaging process. Background Art

[0002] With the advent of the 5G era, ceramic metal shells are challenging the field of optical communications with higher performance, higher integration, more difficult structures, and more difficult processing. Due to the mismatch between the thermal expansion coefficients of ceramics and metals, residual stress is formed during welding, which reduces the connection strength. Therefore, the calculation, measurement, and relief of residual stress generated by the connection between ceramics and metals is one of the key issues that must be solved in the application of engineering ceramics. And the relief of residual stress has become a top priority. At present, the main methods for relieving residual stress are to add stress relief layers, design reasonable connection structures, and adopt reasonable connection processes. However, due to the use of the shell, when structural changes and process changes cannot be made, other means need to be sought to release or relieve the existing residual stress. Summary of the invention

[0003] The object of the present invention is to provide a method for alleviating stress release in a ceramic packaging process, so as to solve the technical problem of the influence of residual stress on shell strength existing in the prior art.

[0004] To achieve the above object, the technical solution adopted by the present invention is: to provide a method for relieving stress release in a ceramic packaging process,

[0005] The method comprises:

[0006] A stress relief groove is provided along the welding seam at one end of the wall body connected with the ceramic body and the chassis, and the size of the stress relief groove is calculated by finite element method according to the yield strength of the ceramic body and the deformation requirements of the chassis;

[0007] Calculate the amount of solder;

[0008] Assembly welding of wall, ceramic body and chassis;

[0009] Residual stress comparison test.

[0010] Furthermore, the distance between the bottom of the stress relief groove and the outer wall surface of the wall is greater than or equal to 0.1 mm.

[0011] Furthermore, the width of the stress relief groove is less than or equal to 0.2 mm.

[0012] Furthermore, the chassis is made of tungsten copper.

[0013] Furthermore, the wall is made of Kovar alloy.

[0014] Furthermore, the outer wall surface of the wall is flush with the outer side surfaces of the chassis.

[0015] Furthermore, the ceramic body has three continuous outer side surfaces exposed outside the wall body, wherein an outer side surface located in the middle of the three protrudes from the bottom plate, and two outer side surfaces parallel to each other are flush with the outer side surface of the bottom plate.

[0016] Furthermore, the outer side surface of the ceramic body protruding from the chassis is provided with a platform which is perpendicular to the outer side surface and extends outward.

[0017] Furthermore, the width of the contact surface between the ceramic body and the wall body is greater than the thickness of the wall body.

[0018] The beneficial effect of the method for alleviating stress release during ceramic packaging provided by the present invention is that: compared with the prior art, the method for alleviating stress release during ceramic packaging provided by the present invention adds stress relief grooves at sensitive positions where the wall is welded to the ceramic part and the chassis without changing the outer structure of the shell. During the welding process, the solder flows inside the stress relief groove to form a wrap angle, and part of the residual stress is absorbed by accumulating the solder. At the same time, the welding area is also reduced, so that the stress point of the ceramic is away from the weak point of the structure, thereby alleviating the failure caused by the mismatch of thermal expansion coefficients during the packaging process of ceramics and metal parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic cross-sectional view of a method for alleviating stress release in a ceramic packaging process provided by an embodiment of the present invention;

[0021] Figure 2 for Figure 1 Schematic diagram of the three-dimensional structure of the method for relieving stress release in the ceramic packaging process Figure 1 ;

[0022] Figure 3 for Figure 1 Schematic diagram of the three-dimensional structure of the method for relieving stress release in the ceramic packaging process Figure 2 ;

[0023] Figure 4 for Figure 1 Schematic diagram of the three-dimensional structure of the method for relieving stress release in the ceramic packaging process Figure 3 ;

[0024] Figure 5 for Figure 1 A schematic diagram of the three-dimensional structure of the wall shown in FIG.

[0025] Figure 6 A schematic diagram of the overall three-dimensional structure of a wall of the method for alleviating stress release in a ceramic packaging process provided by an embodiment of the present invention;

[0026] Figure 7 This is the solder flow state diagram when there is no stress relief groove;

[0027] Figure 8 This is a diagram of the solder flow state when there is a stress relief groove.

[0028] Among them, the reference numerals in the figure are:

[0029] 1- wall; 2- stress relief groove; 3- chassis; 4- ceramic body; 5- platform; 6- solder wrap angle; 7- failure reaction length; 8- welding length. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Please also read Figures 1 to 6 The method for relieving stress release in a ceramic packaging process provided by the present invention is now described. The method for relieving stress release in a ceramic packaging process comprises the following steps:

[0032] Step 1: A stress relief groove is set along the welding seam at one end of the wall body connected to the ceramic body and the chassis. According to the yield strength of the ceramic body and the deformation requirements of the chassis, the size of the stress relief groove is calculated by finite element method. The size of the stress relief groove meets the ceramic yield strength and the deformation requirements of the tungsten copper chassis. The brazing cooling process of the shell and tube is simulated and calculated by ANSYS software. The cooling condition is 25℃-810℃-25℃. When the process meets the following two conditions, the groove size is judged to be suitable:

[0033] The maximum tensile stress of ceramics is ≤400Mpa

[0034] The vertical deformation of the chassis is ≤0.05mm.

[0035] Step 2: Calculate the solder quantity. The solder thickness of the welding surface must meet the requirements, the solder flow state and the solder wrap angle must be full. The initial solder quantity is 80% of the welding area between the ceramic and the wall. At the same time, the following two appearance conditions must be considered:

[0036] (1) The solder flow angle is a rounded 45° angle;

[0037] (2) The solder flows smoothly without accumulation;

[0038] Therefore, after the preliminary calculation of solder material, the final solder amount needs to be adjusted through experiments.

[0039] Step three, assemble and weld the wall, ceramic body and chassis; put all parts such as ceramics, solder, wall, etc. into a graphite mold for positioning and assembly, and use a welding temperature of 25℃-810℃-25℃; put the assembled tube shell into a high-temperature brazing furnace and cool it into shape after 1 hour.

[0040] Step 4: Residual stress comparison test; use the drilling method to compare the residual stress at the weak position of the ceramic; use the limit pressure destruction to compare the failure pressure values ​​of the two structures (two structures with and without stress relief grooves). Through comparison, it is found that when there is no stress relief groove, the solder is scattered on the outside of the wall, the failure reflection length from the edge of the solder to the edge of the ceramic is short, and the starting stress point is close to the edge of the ceramic, which is easy to form cracks; when there is a stress relief groove, the solder is scattered on the inside of the groove to form a wrap angle, which absorbs the distributed stress, and the failure reflection length from the edge of the solder on the welding surface to the edge of the ceramic increases, and the starting stress point is far away from the edge of the ceramic, which relieves the residual stress.

[0041] The drilling method was used to compare the two structures with and without stress relief grooves, and the residual stress values ​​of the ceramics after high-temperature brazing were compared. The ceramic sidewalls at the weak position of the ceramics were tested, and the test results are as follows: the residual stress of the ceramics without stress relief grooves was 80% between 100-150Mpa, and the residual stress of the ceramics with stress relief grooves was 50% between 100-150Mpa. It can be seen that adding stress relief grooves can reduce the high stress area of ​​the ceramics and reduce the risk of failure.

[0042] Compared with the prior art, the method for relieving stress release in the ceramic packaging process provided by the present invention processes a stress relief groove 2 at the position where the wall 1 is welded with the ceramic body 4 and the chassis 3 without changing the external structure of the shell. Since there is no stress relief groove 2, the solder is dispersed on the outside of the wall 1, the failure reflection length from the solder edge to the ceramic edge is short, and the initial stress point is close to the ceramic edge, which is easy to form cracks; while when there is a stress relief groove 2, the solder is dispersed on the inside of the stress relief groove 2 to form a wrap angle, absorbing the distributed stress, and the failure reflection length from the solder edge of the welding surface to the ceramic edge increases, and the initial stress point is far away from the ceramic edge, which relieves residual stress and avoids cracks in the ceramic part.

[0043] See also Figure 2The structure of the ceramic shell prepared by the method provided by the present invention includes a chassis 3, a ceramic body 4 arranged on the chassis 3 and a wall 1 arranged on the chassis 3. The ceramic body 4 is placed at one end of the chassis 3, and one end of the wall 1 is provided with an opening for setting the ceramic body 4. The end of the wall 1 connected with the ceramic body 4 and the chassis 3 is provided with a stress relief groove 2 extending along the joint. The stress relief groove 2 is arranged on the inner wall surface of the wall 1. The inner wall of the stress relief groove 2 close to the ceramic body 4 and the chassis 3 coincides with the contact surface of the ceramic body 4 and the chassis 3, and the bottom of the stress relief groove 2 is lower than the inner wall surface of the wall 1. When there is a stress relief groove, the solder flows inside the groove to form a wrap angle, absorbs the distributed stress, and the failure reflection length from the edge of the solder on the welding surface to the edge of the ceramic increases ( Figure 4 ), the initial stress point is far away from the edge of the ceramic to relieve the residual stress.

[0044] See also Figure 2 As a specific implementation of the method for relieving stress release in the ceramic packaging process provided by the present invention, the distance between the bottom of the stress relief groove 2 and the outer wall surface of the wall 1 is greater than or equal to 0.1 mm. The size of the stress relief groove 2 should not be too small to ensure that there is enough accumulation area for the solder. The conventional wall 1 has a wall thickness of 0.5 mm, and the size of the stress relief groove 2 should not be less than 0.1 mm.

[0045] See also Figures 1 to 5 As a specific implementation of the method for relieving stress release in the ceramic packaging process provided by the present invention, the width of the stress relief groove 2 is less than or equal to 0.2 mm. The conventional welding surface width is 0.5 mm. After adding the stress relief groove 2, the minimum welding surface width should not be less than 0.2 mm.

[0046] Among them, see Figure 7 When there is no stress relief groove, the solder forms a 45° angle at the junction of the wall and the ceramic. At this time, the failure reaction length L1 from the edge of the solder angle 6 to the edge of the ceramic is 0.2mm. The starting stress point is close to the edge of the ceramic, the failure reaction length is short, and cracks are easily formed.

[0047] See also Figure 8 When there is a stress relief groove, the solder forms a solder wrap angle 6 on the inner upper surface of the groove and the ceramic interface, transferring part of the stress on the ceramic. The failure reaction length L2 from the edge of the solder wrap angle 6 to the edge of the ceramic is 0.4 mm. The initial stress point is far away from the edge of the ceramic. Figure 7 By comparison, the failure reaction length increases and the residual stress is relieved. Figure 7 The welding length L3 with stress relief groove is shortened to L4.

[0048] As a specific implementation of the method for alleviating stress release in a ceramic packaging process provided by the present invention, the chassis 3 is made of tungsten copper.

[0049] See also Figure 6 As a specific embodiment of the method for relieving stress release in the ceramic packaging process provided by the present invention, the material of the wall 1 is Kovar alloy. Also known as iron-cobalt-nickel alloy, the alloy has a dense oxide film, is easy to weld and fuse, has good plasticity, can be cut and processed, and is widely used in the production of electric vacuum components, transmitting tubes, kinescopes, switch tubes, transistors, sealed plugs and relay housings. Kovar alloy contains cobalt components, so the product is relatively wear-resistant.

[0050] Due to the different thermal expansion coefficients of kovar, ceramics and tungsten copper, residual stress is easily formed during welding, which reduces the connection strength. At the same time, the three have different deformation trends, which can easily cause cracks in the ceramic and cause failure.

[0051] See also Figure 4 As a specific implementation of the method for alleviating stress release during ceramic packaging provided by the present invention, the outer wall surface of the wall 1 is flush with the outer side surfaces of the chassis 3.

[0052] See also Figure 3 and Figure 4 As a specific implementation of the method for alleviating stress release during ceramic packaging provided by the present invention, the ceramic body 4 has three continuous outer sides exposed outside the wall 1, wherein an outer side surface located in the middle of the three protrudes from the chassis 3, and two outer side surfaces parallel to each other are flush with the outer side surfaces of the chassis 3.

[0053] See also Figures 1 to 4 As a specific implementation of the method for alleviating stress release in the ceramic packaging process provided by the present invention, the ceramic body 4 protrudes from the outer side surface of the chassis 3 and is provided with a platform 5 that is perpendicular to the outer side surface and extends outward, and the platform 5 is used for welding welding pins.

[0054] See also Figures 1 to 4 As a specific implementation of the method for alleviating stress release in the ceramic packaging process provided by the present invention, the width of the contact surface between the ceramic body 4 and the wall 1 is greater than the thickness of the wall 1.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for relieving stress release in a ceramic packaging process, characterized in that: The method comprises: A stress relief groove is set along the welding seam at one end of the wall body connected to the ceramic body and the chassis. The size of the stress relief groove is calculated by finite element method according to the yield strength of the ceramic body and the deformation requirements of the chassis. The brazing cooling process of the shell and tube is simulated and calculated by ANSYS software. The cooling condition is 25℃-810℃-25℃. When the process meets the following two conditions, the groove size is judged to be suitable: The maximum tensile stress of ceramics is ≤400Mpa; The vertical deformation of the chassis is ≤0.05mm; Calculate the solder quantity; the preliminary solder quantity is 80% of the welding area between the ceramic and the wall, and the following two appearance conditions must also be considered: (1) The solder flow angle is a rounded 45° angle; (2) The solder flows smoothly without accumulation; Therefore, after the initial calculation of solder material, the final solder amount needs to be adjusted through experiments; The wall, ceramic body and chassis are assembled and welded; the ceramic, solder and all the wall parts are placed in the graphite mold for positioning and assembly, and the welding temperature is 25℃-810℃-25℃; the assembled shell and tube are put into the high-temperature brazing furnace and cooled and formed in 1 hour; Residual stress comparison test; the drilling method is used to compare the residual stress at the weak position of the ceramic; the ultimate pressure destruction is used to compare the failure pressure values ​​of the two structures; through comparison, when there is no stress relief groove, the solder is scattered on the outside of the wall, the failure reflection length from the solder edge to the ceramic edge is short, and the initial stress point is close to the ceramic edge, which is easy to form cracks; when there is a stress relief groove, the solder is scattered on the inside of the groove to form a wrap angle, which absorbs the distributed stress, and the failure reflection length from the solder edge of the welding surface to the ceramic edge increases, and the initial stress point is far away from the ceramic edge, which relieves the residual stress; The ceramic body is placed at one end of the chassis, an opening for setting the ceramic body is provided at one end of the wall, a stress relief groove extending along the joint is provided at one end of the wall where the ceramic body and the chassis are connected, the stress relief groove is arranged on the inner wall surface of the wall, the stress relief groove is close to the inner wall of the ceramic body and the chassis and coincides with the contact surface of the ceramic body and the chassis, and the bottom of the stress relief groove is lower than the inner wall surface of the wall.

2. The method for relieving stress release in a ceramic packaging process according to claim 1, characterized in that: The distance between the bottom of the stress relief groove and the outer wall surface of the wall is greater than or equal to 0.1 mm.

3. The method for relieving stress release in a ceramic packaging process according to claim 1, characterized in that: The width of the stress relief groove is less than or equal to 0.2 mm.

4. The method for alleviating stress release in a ceramic packaging process according to claim 1, characterized in that: The chassis is made of tungsten copper.

5. The method for relieving stress release in a ceramic packaging process according to claim 1, characterized in that: The material of the wall is Kovar alloy.

6. The method for relieving stress release in a ceramic packaging process according to claim 1, characterized in that: The outer wall surface of the wall body is flush with the outer side surfaces of the chassis.

7. The method for relieving stress release in a ceramic packaging process according to claim 6, characterized in that: The ceramic body has three continuous outer side surfaces exposed outside the wall body, wherein an outer side surface located in the middle of the three protrudes from the bottom plate, and two outer side surfaces parallel to each other are flush with the outer side surface of the bottom plate.

8. The method for relieving stress release in a ceramic packaging process according to claim 7, characterized in that: The ceramic body is protruding from the outer side of the bottom plate and is provided with a platform which is perpendicular to the outer side and extends outward.

9. The method for relieving stress release in a ceramic packaging process according to claim 1, characterized in that: The width of the contact surface between the ceramic body and the wall body is greater than the thickness of the wall body.

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