A laser gain unit packaging structure

Abstract

This invention relates to a laser gain unit packaging structure. The laser gain unit packaging structure of this invention comprises a first transition layer bonded to a metal surface and a second transition layer bonded to an inorganic non-metallic surface. The thermal expansion coefficient α1 of the first transition layer is between that of the metal structure and the epoxy resin; the thermal expansion coefficient α2 of the second transition layer is between that of the inorganic non-metallic structure and the epoxy resin. This allows for a gradual transition between the volume changes caused by thermal expansion or contraction between the metal and inorganic non-metallic structures, reducing the stress impact caused by the difference in thermal expansion coefficients.

Description

Technical Field

[0001] This invention belongs to the field of precision packaging technology, and particularly relates to a laser gain unit packaging structure. Background Technology

[0002] In engineering fields such as solid-state lasers, microelectronics, and aerospace, it is common to see encapsulation structures that connect metals with inorganic non-metals (glass, ceramics, etc.). The main methods of joining metals and inorganic non-metals include bonding, welding, and mechanical joining. Compared to welding and mechanical joining, bonding offers advantages such as lighter joint weight, more uniform stress distribution, and better sealing, making it a promising option for precision packaging.

[0003] In existing packaging methods, due to the significant difference in thermal expansion coefficients between metals and inorganic non-metals, when the bonded structure operates under wide temperature range conditions, especially with large temperature changes, significant thermal stress is generated at the bonding point, accelerating the aging and failure of the adhesive. When the adhesive layer is thick and has high strength and hardness, it can even lead to the destruction of the bonded object on the weaker side. Especially in the field of solid-state lasers, ensuring the beam quality of the laser operating over a wide temperature range places higher demands on the packaging method of the laser gain unit.

[0004] Therefore, in laser gain units, how to reduce the thermal stress caused by the difference in thermal expansion coefficients between the bonded metal and the inorganic non-metal has become an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a laser gain unit packaging structure.

[0006] The technical solution of this invention is as follows:

[0007] A laser gain unit packaging structure includes, from top to bottom, a metal structure, a first transition layer, a stress relief layer, a second transition layer, and an inorganic non-metallic structure bonded together.

[0008] The first transition layer is bonded to the lower surface of the metal structure; the second transition layer is bonded to the upper surface of the inorganic non-metal.

[0009] The stress relief layer is bonded between the first transition layer and the second transition layer;

[0010] The thermal expansion coefficient α1 of the first transition layer is between that of the metal structure and that of the epoxy resin; the thermal expansion coefficient α2 of the second transition layer is between that of the inorganic non-metal and that of the epoxy resin.

[0011] Preferably, the encapsulation structure includes multiple first transition layers and second transition layers; the coefficient of thermal expansion of the transition layers decreases sequentially from top to bottom.

[0012] Preferably, the thickness ratio of the first transition layer to the stress relief layer and the thickness ratio of the second transition layer to the stress relief layer are both 1:1.5 to 1:3.

[0013] Preferably, the first transition layer is formed by mixing and curing metal powder and epoxy resin liquid, wherein the mass ratio of metal powder to epoxy resin liquid is 1:1.5 to 1:2.

[0014] The second transition layer is formed by mixing and curing surface-modified hollow glass microspheres and epoxy resin liquid, with the mass ratio of surface-modified hollow glass microspheres to epoxy resin liquid being 1:6 to 1:8.

[0015] The stress relief layer is formed by mixing and curing metal powder, surface-modified hollow glass microspheres and epoxy resin liquid, with the mass ratio of metal powder, surface-modified hollow glass microspheres and epoxy resin liquid being 4:1:12 to 4:1:16.

[0016] Further preferably, the hollow structure of the surface-modified hollow glass microspheres is a vacuum structure or filled with inert gas.

[0017] More preferably, the particle size of the metal powder is ≤100um.

[0018] More preferably, the epoxy resin adhesive comprises epoxy resin and additives, wherein the mass ratio of epoxy resin to additives is 1.5:1 to 2:1; the epoxy resin is bisphenol A type epoxy resin; and the additives are one or more of curing agents, diluents, and toughening agents.

[0019] The curing agent accounts for 20% to 30% of the total mass of the epoxy resin adhesive; the diluent accounts for 6% to 8% of the total mass of the epoxy resin adhesive; and the toughening agent accounts for 6% to 8% of the total mass of the epoxy resin adhesive.

[0020] The curing agent is an amine-based curing agent; the diluent is any one of anhydrous ethanol, acetone, ethylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether; the toughening agent is any one of polyurethane thermoelastic elastomer, polyolefin thermoelastic elastomer, and styrene thermoelastic elastomer.

[0021] More preferably, the preparation process of the surface-modified hollow glass microspheres includes the following steps:

[0022] 1) Add n-butanol to hollow glass microspheres and stir at 500 rpm for half an hour to disperse the hollow glass microspheres. Then add silane coupling agent dropwise.

[0023] 2) After adding the silane coupling agent, stir at 500 rpm for 20 minutes, and place in an oven at 80-100℃ to maintain the temperature for 4-6 hours to obtain the initial mixture;

[0024] 3) Wash the surface of the initial mixture with anhydrous ethanol to remove the n-butanol and silane coupling agent, and dry the washed solid at 70-80°C to obtain surface-modified hollow glass microspheres.

[0025] In a further preferred embodiment, the amount of surface-modified hollow glass microspheres is 10-12 parts by mass, the amount of n-butanol is 200-240 parts by mass, the amount of silane coupling agent is 0.3-0.4 parts by mass, and the diameter of the surface-modified hollow glass microspheres is 20-100 μm.

[0026] Preferably, the surface-modified hollow glass microspheres can be replaced by silica powder; the silica powder has a diameter of 100 nm to 100 μm.

[0027] The beneficial effects of this invention are:

[0028] 1. The laser gain unit packaging structure of the present invention has a first transition layer bonded to a metal surface and a second transition layer bonded to an inorganic non-metal surface. The thermal expansion coefficient α1 of the first transition layer is between that of the metal structure and the epoxy resin; the thermal expansion coefficient α2 of the second transition layer is between that of the inorganic non-metal and the epoxy resin, so that the volume change caused by thermal expansion or contraction between the metal surface and the inorganic non-metal surface gradually transitions, reducing the stress effect caused by the difference in thermal expansion coefficient.

[0029] 2. The stress relief layer of the laser gain unit packaging structure of the present invention is used to absorb the stress generated by the metal surface and the inorganic non-metal surface, and can also absorb the stress generated by the first transition layer and the second transition layer; the packaging structure is suitable for the connection between metal (such as heat sink) and inorganic non-metal (such as crystal, quartz pad) in a wide temperature range. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the laser gain unit packaging structure described in this invention. Detailed Implementation

[0031] Example 1

[0032] like Figure 1 As shown.

[0033] A laser gain unit packaging structure includes, from top to bottom, a metal structure, a first transition layer, a stress relief layer, a second transition layer, and an inorganic non-metallic structure bonded together; the first transition layer is bonded to the lower surface of the metal structure; the second transition layer is bonded to the upper surface of the inorganic non-metallic structure; the stress relief layer is bonded between the first and second transition layers; the coefficient of thermal expansion of the first transition layer is α. 1 The coefficient of thermal expansion of the second transition layer is between that of the metal structure and that of the epoxy resin; the coefficient of thermal expansion of the second transition layer α2 is between that of the inorganic non-metal and that of the epoxy resin.

[0034] In this embodiment, the metal structure is stainless steel and the inorganic non-metallic structure is quartz.

[0035] Example 2

[0036] As described in Example 1, the laser gain unit packaging structure further includes two first transition layers and two second transition layers; the coefficient of thermal expansion of the transition layers decreases sequentially from top to bottom. This multi-transition-layer design is suitable for joining materials with excessively different coefficients of thermal expansion, further preventing breakage at the joint due to excessive differences in the coefficients of thermal expansion of the bonded materials.

[0037] This invention selects a suitable thermal expansion coefficient transition layer based on the thermal expansion coefficient and surface roughness of the materials being joined, satisfying the following two principles: First, the thermal expansion coefficient of the transition layer (including the first transition layer and the second transition layer) is between that of the materials being joined and the epoxy resin; second, the filler diameter is selected according to the surface roughness of the joined surfaces, so that the adhesive (the first transition layer, the second transition layer, and the stress relief layer in their pre-cured form) can penetrate deep into the surface micro-gaps. The smaller the roughness, the smaller the diameter selected.

[0038] Example 3

[0039] As described in Example 1, the thickness ratio of the first transition layer to the stress relief layer and the thickness ratio of the second transition layer to the stress relief layer are both 1:2.

[0040] Example 4

[0041] As described in Example 1, the laser gain unit packaging structure further includes a first transition layer formed by mixing and curing metal powder and epoxy resin liquid, wherein the mass ratio of metal powder to epoxy resin liquid is 1:1.7.

[0042] The second transition layer is formed by mixing and curing surface-modified hollow glass microspheres and epoxy resin liquid, with a mass ratio of surface-modified hollow glass microspheres to epoxy resin liquid of 1:7.

[0043] The stress relief layer is formed by mixing and curing metal powder, surface-modified hollow glass microspheres and epoxy resin liquid, with the mass ratio of metal powder, surface-modified hollow glass microspheres and epoxy resin liquid being 4:1:14.

[0044] In this embodiment, the metal powder for the stress relief layer is selected from metals with good ductility. The surface-modified hollow glass microspheres have a thermal expansion coefficient close to that of the inorganic non-metallic surface; both the ductile metal powder and the surface-modified hollow glass microspheres undergo a certain degree of micro-deformation, which can adapt to the difference in thermal expansion coefficients of the bonded materials and the volume changes caused by stress; thus, the two bonded materials (metal and inorganic non-metal) can achieve stress relief through the micro-deformation generated by themselves during large temperature changes, achieving the purpose of stress absorption and enhancing the reliability of the encapsulation structure under temperature variation conditions in a wide temperature range.

[0045] Experiments have shown that the content of surface-modified hollow glass microspheres and metal powder affects the coefficient of thermal expansion and bond strength of the adhesive layers (first transition layer, second transition layer, and stress-relief layer), thus impacting adhesive performance. Both excessively high and low proportions of surface-modified hollow glass microspheres and metal powder in the adhesive layer reduce adhesive performance: too high a proportion results in insufficient bond strength between the adhesive layer and the surface of the bonded material, while too low a proportion results in an excessive difference in the coefficient of thermal expansion between the adhesive layer and the bonded material itself. In practical applications, the mass ratio of metal powder or surface-modified hollow glass microspheres to epoxy resin is adjusted based on the coefficient of thermal expansion of the metals and inorganic non-metals, the bonding area, etc.

[0046] Example 5

[0047] As described in Example 4, the laser gain unit packaging structure further includes a vacuum structure for the surface-modified hollow glass microspheres. The vacuum hollow structure forms a poor conductor of heat, reducing heat transfer from one side of the bonded material to the other, and further minimizing the impact of differences in thermal expansion coefficients on the overall packaging structure.

[0048] Example 6

[0049] The laser gain unit packaging structure described in Example 5 differs in that the hollow structure of the surface-modified hollow glass microspheres is filled with an inert gas. The hollow structure filled with inert gas forms a poor conductor of heat, which can also reduce heat transfer from one side of the bonded material to the other side, further reducing the impact of the difference in thermal expansion coefficients on the overall packaging structure.

[0050] Example 7

[0051] As described in Example 4, the laser gain unit packaging structure further includes a metal powder particle size ≤ 100 μm. The metal powder is indium powder or silver-indium powder; in this example, indium powder is used.

[0052] Example 8

[0053] As described in Example 4, the laser gain unit encapsulation structure further includes an epoxy resin adhesive comprising epoxy resin and additives, wherein the mass ratio of epoxy resin to additives is 1.7:1; the epoxy resin is a bisphenol A type epoxy resin; and the additives are one or more of a curing agent, a diluent, and a toughening agent.

[0054] The curing agent accounts for 25% of the total mass of the epoxy resin adhesive; the diluent accounts for 7% of the total mass of the epoxy resin adhesive; and the toughening agent accounts for 7% of the total mass of the epoxy resin adhesive.

[0055] The curing agent is an amine-based curing agent; the diluent is any one of anhydrous ethanol, acetone, ethylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether; the toughening agent is any one of polyurethane thermally extensible elastomer, polyolefin thermally extensible elastomer, and styrene thermally extensible elastomer (this embodiment uses polyurethane thermally extensible elastomer).

[0056] Example 9

[0057] As described in Example 4, the laser gain unit packaging structure further includes the following steps in the preparation process of the surface-modified hollow glass microspheres:

[0058] 1) Add n-butanol to hollow glass microspheres and stir at 500 rpm for half an hour using a magnetic stirrer to disperse the hollow glass microspheres. Then, add silane coupling agent dropwise. The silane coupling agent used in this example is γ-aminopropyltriethoxysilane (KH550).

[0059] 2) After adding the silane coupling agent, stir at 500 rpm for 20 minutes, place in an 80℃ oven and maintain the temperature for 6 hours to obtain the initial mixture;

[0060] 3) The n-butanol and silane coupling agent on the surface of the initial mixture were washed with anhydrous ethanol, and the washed solids were dried at 70°C to obtain surface-modified hollow glass microspheres. Surface modification of the hollow glass microspheres improved their hydrophobicity, making them easier to disperse in epoxy resin solutions and facilitating the bonding between the modified hollow glass microspheres and the epoxy resin.

[0061] Example 10

[0062] As described in Example 9, the laser gain unit packaging structure further includes 12 parts by mass of surface-modified hollow glass microspheres, 240 parts by mass of n-butanol, 0.4 parts by mass of silane coupling agent, and a diameter of 40 μm for the surface-modified hollow glass microspheres.

[0063] Example 11

[0064] The laser gain unit packaging structure described in Example 4 differs in that, considering the surface roughness of the bonded material, the surface-modified hollow glass microspheres can be replaced by silica powder. The silica powder has a diameter of 5 μm.

[0065] Comparative Example 1:

[0066] Compared with Example 1, no filler (metal powder or surface-modified hollow glass microspheres) is added to the first transition layer, the second transition layer and the stress relief layer, that is, only epoxy resin liquid is used for structural encapsulation.

[0067] Comparative Example 2:

[0068] Compared to Example 1, the first and second transition layers are not coated; only the stress relief layer is coated for structural encapsulation.

[0069] Comparative Example 3:

[0070] Compared to Example 1, no stress relief layer is coated; only the first transition layer and the second transition layer are coated for structural encapsulation.

[0071] Comparative Example 4:

[0072] Consistent with Example 1, high and low temperature impacts were not performed in subsequent tensile testing experiments.

[0073] Tensile test experiment:

[0074] The samples prepared in the above examples were subjected to high and low temperature shocks respectively: the samples were placed in liquid pentafluoropropane and cooled for 15 minutes, and then immediately immersed in 90°C hot water for 15 minutes. This cycle was repeated 20 times.

[0075] Tensile tests were conducted on the specimens after 20 rounds of high and low temperature impact using a DN-W20KN tensile testing machine manufactured by Zhejiang Dyna Automation Technology Co., Ltd. The test results are shown in Table 1.

[0076] Table 1. Examples and Comparative Examples of this Application

[0077]

[0078] Based on Table 1, the following analysis is performed:

[0079] As can be seen from Examples 8, 9, and 11, the encapsulation structure proposed in this invention can be used to encapsulate and connect metals and non-metals with large differences in thermal expansion coefficients. The structure still exhibits good connection strength after being subjected to 20 rounds of high-temperature impact.

[0080] A comparison of Example 8 and Comparative Example 1 leads to the conclusion that the addition of surface-modified hollow glass microspheres and metal powder improves the bonding strength of the encapsulation structure under wide temperature variations, exceeding that of ordinary epoxy resin adhesive by 23%. This is because the addition of fillers improves the thermal and mechanical properties of the epoxy resin colloid. The first and second transition layers, acting as thermal expansion coefficient transition layers, reduce the impact of the difference in thermal expansion coefficients between the bonded material and the epoxy resin colloid, thereby reducing the thermal stress generated by the mismatch in thermal expansion coefficients during large temperature changes. The addition of highly ductile metal powder in the stress relief layer allows for some micro-deformation of the epoxy resin colloid, releasing some stress in the encapsulation structure through deformation, achieving stress absorption and thus reaching the desired bonding strength.

[0081] A comparison of Example 8 with Comparative Examples 2 and 3 shows that the first transition layer, the second transition layer, and the stress relief layer are all indispensable for this encapsulation method.

[0082] In Comparative Example 2, since the stress relief layer contains metal powder and surface-modified hollow glass microspheres, its coefficient of thermal expansion is also between that of the connected parts and the epoxy resin colloid, which can play a role in the thermal expansion transition to a certain extent. Therefore, it has higher strength than Comparative Example 3, but is still 7.6% lower than Example 8.

[0083] As can be seen from the comparison between Example 8 and Comparative Example 4, the packaging structure can still achieve 97.5% of its strength before the high and low temperature impact after 20 rounds of high and low temperature shocks, which proves the reliability of the present invention for metal and inorganic non-metal packaging in a wide temperature range working environment.

Claims

1. A laser gain cell package structure, characterized by, The packaging structure comprises a metal structure, a first transition layer, a stress release layer, a second transition layer and an inorganic non-metal structure which are sequentially bonded from top to bottom; the first transition layer is bonded to the lower surface of the metal structure; the second transition layer is bonded to the upper surface of the inorganic non-metal structure; the stress release layer is bonded between the first transition layer and the second transition layer; the thermal expansion coefficient α1 of the first transition layer is between the thermal expansion coefficient of the metal structure and the thermal expansion coefficient of the epoxy resin; the thermal expansion coefficient α2 of the second transition layer is between the thermal expansion coefficient of the inorganic non-metal structure and the thermal expansion coefficient of the epoxy resin; The first transition layer is formed by mixing and curing metal powder and epoxy resin glue solution, and the mass ratio of the metal powder to the epoxy resin glue solution is 1:1.5-1:2; The second transition layer is formed by mixing and curing surface-modified hollow glass microspheres and epoxy resin glue solution, and the mass ratio of the surface-modified hollow glass microspheres to the epoxy resin glue solution is 1:6-1:8; The stress release layer is formed by mixing and curing metal powder, surface-modified hollow glass microspheres and epoxy resin glue solution, and the mass ratio of the metal powder, the surface-modified hollow glass microspheres and the epoxy resin glue solution is 4:1:12-4:1:

16.

2. The laser gain cell package structure of claim 1, wherein, The packaging structure comprises a plurality of first transition layers and second transition layers; the thermal expansion coefficients of the transition layers decrease from top to bottom.

3. The laser gain cell package structure of claim 1, wherein, The thickness ratio of the first transition layer to the stress release layer and the thickness ratio of the second transition layer to the stress release layer are both 1:1.5-1:

3.

4. The laser gain cell package structure of claim 1, wherein, The hollow structure of the surface-modified hollow glass microspheres is a vacuum structure or a structure filled with inert gas.

5. The laser gain cell package structure of claim 1, wherein, The particle size of the metal powder is ≤100 um.

6. The laser gain cell package structure of claim 1, wherein, The epoxy resin glue solution comprises epoxy resin and an additive, and the mass ratio of the epoxy resin to the additive is 1.5:1-2:1; the epoxy resin is bisphenol A type epoxy resin; the additive is one or more of a curing agent, a diluent and a toughening agent; The curing agent accounts for 20%-30% of the total mass of the epoxy resin glue solution; the diluent accounts for 6%-8% of the total mass of the epoxy resin glue solution; and the toughening agent accounts for 6%-8% of the total mass of the epoxy resin glue solution. The curing agent is an amine curing agent; the diluent is any one of anhydrous ethanol, acetone, ethylene glycol diglycidyl ether and 1,4-butanediol diglycidyl ether; and the toughening agent is any one of polyurethane hot ductile elastomer, polyolefin hot ductile elastomer and styrene hot ductile elastomer.

7. The laser gain cell package structure of claim 1, wherein, The preparation process of the surface-modified hollow glass microspheres comprises the following steps: 1) adding n-butanol to the hollow glass microspheres, stirring for half an hour at a speed of 500 rpm to disperse the hollow glass microspheres, and then adding the silane coupling agent drop by drop; 2) stirring for 20 minutes at a speed of 500 rpm after adding the silane coupling agent, and then placing in an oven at a temperature of 80-100 ℃ for 4-6 h to obtain an initial mixture; 3) washing the n-butanol and the silane coupling agent on the surface of the initial mixture with anhydrous ethanol, and drying the washed solid at a temperature of 70-80 ℃ to obtain the surface-modified hollow glass microspheres.

8. The laser gain cell package structure of claim 7, wherein, The surface modified hollow glass microsphere is used in an amount of 10-12 parts by mass, the n-butanol is used in an amount of 200-240 parts by mass, the silane coupling agent is used in an amount of 0.3-0.4 parts by mass, and the surface modified hollow glass microsphere has a diameter of 20-100 um.

9. The laser gain cell package structure of claim 1, wherein, The surface modified hollow glass microsphere can be replaced by silica powder, and the silica powder has a diameter of 100 nm-100 um.

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