A nonlinear optical crystal package and a welding packaging method thereof

Abstract

The application relates to the field of nonlinear optical crystals, and particularly discloses a nonlinear optical crystal packaging body and a welding packaging method thereof. The welding packaging method comprises the following steps: respectively performing metal plating film processing on welding surfaces of a nonlinear optical crystal and a heat sink; arranging brazing filler between the welding surfaces of the nonlinear optical crystal and the heat sink and enabling the three to be in close contact to form a welding body; and placing the welding body in a controllable atmosphere environment to perform vacuum reflow soldering. The method can effectively improve the heat conduction effect, improve the temperature control precision of the nonlinear crystal, and further improve the stability of the nonlinear crystal during work by welding the nonlinear crystal and the heat sink made of a high-thermal-conductivity material into a whole through the brazing filler and a special vacuum reflow soldering process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nonlinear optical crystal, more particularly, to a nonlinear optical crystal package and a welding packaging method thereof. BACKGROUND

[0002] Nonlinear optical crystal is a device that uses its nonlinear effect under the action of strong laser, strong external field, etc. to expand the wavelength and wavelength range of existing laser, and can perform frequency conversion technology such as frequency doubling, frequency mixing, parametric oscillation and optical parametric amplification. Nonlinear optical crystal is a functional material and has important application value in the field of laser technology. Widely used are BaB2O4 (BBO) crystal, CsH2A5O4 (CDA) crystal, KTP crystal, KDP crystal, LiB3O5 (LBO) crystal, NaNO2 crystal, GaAs crystal, InSb, InAs crystal and ZnS crystal, etc.

[0003] Nonlinear optical crystals are diverse in types and widely used. When nonlinear optical crystals are used for temperature matching and wavelength tuning, temperature adjustment and constant temperature control are required. When nonlinear optical crystals are used for non-temperature matching and wavelength tuning, necessary temperature control of the crystals is also required to obtain the best power conversion efficiency and reduce the thermal stress of the crystals.

[0004] At present, the temperature control of nonlinear optical crystals is mainly achieved by the following methods: the nonlinear optical crystal is coated with indium, or is fixed by being pasted with heat-conducting silicone grease, heat-conducting adhesive and epoxy resin on a heat sink (usually made of heat-conducting material such as red copper), and the heat sink is controlled in temperature by TEC, water cooling or air cooling. The above-mentioned fixing method by indium coating has a large contact thermal resistance, and the fixing method by pasting with heat-conducting silicone grease, heat-conducting adhesive and epoxy resin has a low heat conductivity. The above-mentioned situations restrict the temperature field stability of the nonlinear optical crystal, and further affect the stability thereof in the use of wavelength tuning, etc.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] In order to solve the problems of large contact thermal resistance and low heat conductivity of the packaging method of the nonlinear optical crystal and the heat sink in the prior art, the present application provides a nonlinear optical crystal package and a welding packaging method thereof.

[0007] The present application adopts the following technical solution:

[0008] In a first aspect, the present application provides a welding packaging method of a nonlinear optical crystal and a heat sink, which comprises:

[0009] The welding surface of the nonlinear optical crystal and the welding surface of the heat sink are respectively subjected to a metallization plating process;

[0010] A brazing filler metal is arranged between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink, and the three are tightly contacted to form a welding body;

[0011] The welding body is placed in a controllable atmosphere environment to perform vacuum reflow soldering.

[0012] Further, the vacuum reflow soldering method comprises:

[0013] The vacuumization is performed to make the air pressure in the environment where the welding body is located be 6×10 -3 ~ 1×10 -4 Pa, the heating is performed to the melting point temperature of the brazing filler metal, and after the heat preservation for 3~30 min, the cooling is performed to the room temperature.

[0014] Further, after the vacuumization is performed to make the air pressure in the environment where the welding body is located be 6×10 -3 ~ 1×10 -4 Pa, the method further comprises the following steps:

[0015] After the mixed gas containing formic acid, hydrogen or nitrogen is filled to the air pressure in the environment where the welding body is located be 1×10 3 Pa~1.5×10 5 Pa, the heating is performed.

[0016] Further, after the heating and the heat preservation are performed to the welding body, the method further comprises:

[0017] The environment where the welding body is located is vacuumized or nitrogen is filled to perform atmosphere protection, and then the cooling is performed at the cooling rate of 300~500℃ / h.

[0018] Further, the method of arranging the brazing filler metal between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink comprises:

[0019] The brazing filler metal is deposited to the welding surface of the heat sink to form a solder layer;

[0020] Or, the brazing filler metal is processed into a solder sheet similar to the shape of the welding surface, and then the solder sheet is placed between the nonlinear optical crystal and the heat sink.

[0021] Further, the thickness of the solder layer or the solder sheet is 5um~200um.

[0022] Further, the thermal conductivity of the material of the heat sink is 100~400W / (m·K).

[0023] Further, the method of the metallization plating process comprises:

[0024] The metal material is used to form at least one layer of metal film with a thickness of 5-1000 nm on the welding surface of the nonlinear optical crystal or the heat sink by using the evaporation method or the magnetron sputtering method.

[0025] Further, the metal film formed on the welding surface of the nonlinear optical crystal has at least two layers, and the outermost layer is gold, and the typical scheme is as follows from inside to outside:

[0026] a titanium film with a thickness of 5-100 nm, a chromium film with a thickness of 5-100 nm, and a gold film with a thickness of 50-1000 nm;

[0027] or, a titanium film with a thickness of 5-100 nm, a platinum film with a thickness of 10-100 nm, and a gold film with a thickness of 10-1000 nm.

[0028] In the second aspect, the application provides a nonlinear optical crystal packaging body packaged by the welding packaging method.

[0029] In summary, the application has the following beneficial effects:

[0030] 1. The welding packaging method of the nonlinear optical crystal and the heat sink provided by the application first carries out metal plating film processing on the welding surfaces of the nonlinear optical crystal and the heat sink, can form multiple layers of metal films with different thicknesses and different materials on the welding surfaces of the nonlinear optical crystal and the heat sink, forms a transition layer on the surface of the nonlinear optical crystal, can enhance the wettability of the brazing material on the welding surface in the process of welding with metal, avoids the generation of cavities in the welding process, reduces the thermal conductivity of the welding layer, and can adjust the difference in the thermal expansion coefficient between the welding layer and the crystal and the heat sink through certain design, reduces the stress, and improves the firmness of welding. Finally, the stress on the nonlinear crystal can be reduced, the thermal conductivity between the nonlinear crystal and the heat sink can be improved, the waste heat in the nonlinear crystal can be timely conducted out, and the temperature control precision and stability can be improved.

[0031] 2. The welding packaging method of the nonlinear optical crystal and the heat sink provided by the application uses the vacuum reflow soldering process to weld and package the nonlinear optical crystal and the heat sink into a whole by the brazing material, does not need to extrude the nonlinear optical crystal in the welding process, does not generate additional stress on the nonlinear optical crystal, does not affect the phase matching angle, is beneficial to maintaining the integrity of the nonlinear optical crystal and maintaining the frequency conversion performance of the nonlinear optical crystal itself; at the same time, the vacuum reflow soldering process is used to carry out welding in a controllable atmosphere environment, is helpful to forming specific intermetallic compounds, and is helpful to timely discharging small bubbles in the packaging body, avoiding the generation of cavities and causing the reduction of thermal conductivity.

[0032] 3. Compared with the process of using indium coating or thermal conductive silicone paste to paste and fix the nonlinear optical crystal to the heat sink in the prior art, the nonlinear optical crystal is integrally welded and packaged with the heat sink in the application, the heat conduction effect of the nonlinear optical crystal is effectively improved, the temperature control precision of the nonlinear optical crystal is improved, and the stability of the nonlinear optical crystal during operation is improved.

[0033] 4. The nonlinear optical crystal package obtained by the packaging method is more stable in output laser wavelength and power during laser nonlinear frequency conversion, such as frequency doubling and difference frequency process. The nonlinear optical crystal package has great application prospect in heat dissipation of an optical parametric oscillator (OPO) and an optical parametric amplifier (OPA) under high power. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flow chart of the method provided by the embodiment of the application. DETAILED DESCRIPTION

[0035] The embodiments of the application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only used to illustrate the application and should not be regarded as limiting the scope of the application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer, the reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased on the market.

[0036] The technical scheme of the application is:

[0037] The nonlinear optical crystal is a functional material which can be frequency converted in a specific environment and has important application value in the field of laser technology. In the application process, the nonlinear optical crystal often needs to be temperature regulated and constant temperature controlled. At present, the method for temperature control of the nonlinear optical crystal is to fix the nonlinear optical crystal and the heat sink together by indium coating or heat-conducting adhesive. Although this method can regulate the temperature to a certain extent, the inventors found in the use process that the two methods either have a large contact thermal resistance due to air gap or have a low thermal conductivity. These will restrict the temperature field stability of the nonlinear optical crystal, and then affect its stability in the use of wavelength tuning and the like. At the same time, the inventors also found through a large amount of research that, since the nonlinear optical crystal itself has great brittleness and anisotropy, additional stress needs to be applied in the packaging process by the above-mentioned indium coating or adhesive fixing method. First, the stress is too large, which is easy to crush the nonlinear optical crystal. Second, since the nonlinear effect of the nonlinear optical crystal seriously depends on the anisotropy of the crystal and the specific phase matching angle, when the stress applied in the packaging process is uneven, it is easy to affect the phase matching angle. The commonly used temperature phase matching method seriously depends on the temperature (the refractive index of some crystals is a temperature sensitive function), and the temperature rise caused by the low thermal conductivity which cannot timely lead the waste heat into the nonlinear crystal and the additional stress caused by the external clamping will cause the phase mismatch, so that the frequency is unstable, and even cannot work normally, which is difficult to frequency conversion.

[0038] Based on the above finding, the inventors have carried out a large amount of research and experiments on the connection between the nonlinear optical crystal and the heat sink in order to find a packaging method which can stably connect the nonlinear optical crystal and the heat sink and has high thermal conductivity without extruding the nonlinear optical crystal. Under the guidance of this concept, the inventors tried to weld the nonlinear optical crystal and the heat sink together. However, since the nonlinear optical crystal is non-metallic, it is difficult to be welded with the heat sink by ordinary welding method, and the welding firmness is always not good, which is difficult to meet the use requirements. Therefore, the inventors continue to improve the welding method, apply a metal film on the surface of the nonlinear optical crystal and the heat sink for transition, improve the welding firmness and wettability, and adopt a special vacuum reflow welding process to weld the nonlinear optical crystal and the heat sink made of high thermal conductivity materials such as oxygen-free copper, diamond and silicon carbide into a whole, which successfully solves the above technical problems, effectively improves the heat conduction effect, and improves the temperature control precision of the nonlinear optical crystal, thereby improving the stability of the nonlinear optical crystal in operation.

[0039] Based on the above invention concept, the embodiment provides a nonlinear optical crystal packaging body and a welding packaging method thereof, and the flowchart of the welding packaging method is as shown in Figure 1 The method comprises the following steps:

[0040] Step S1: Metallization plating treatment is performed on the welding surfaces of the nonlinear optical crystal and the heat sink.

[0041] By performing metallization plating treatment on the welding surfaces of the nonlinear optical crystal and the heat sink before welding, a plurality of metal films with different thicknesses and materials can be formed on the welding surfaces of the nonlinear optical crystal and the heat sink, thereby forming a transition layer on the surface of the nonlinear optical crystal. In the process of welding with metal, the welding firmness is enhanced, the wettability of the welding metal is improved, and voids are avoided in the welding process, thereby reducing the heat dissipation performance of the nonlinear optical crystal, affecting the temperature control accuracy of the nonlinear crystal, and reducing the use performance.

[0042] The metallization plating treatment refers to depositing metal materials such as titanium, chromium, nickel, platinum, gold, etc. on the welding surfaces of the nonlinear optical crystal and the heat sink in a certain order, thickness, and combination by using evaporation or magnetron sputtering.

[0043] Further, the method of metallization plating treatment includes:

[0044] The metal material is used to form at least one metal film with a thickness of 5-1000 nm on the welding surface of the nonlinear optical crystal or the heat sink by using evaporation or magnetron sputtering.

[0045] The metal material includes but is not limited to titanium, chromium, nickel, platinum, gold, etc. In the process of metallization treatment, depositing a metal film with a thickness of 5-1000 nm can also achieve the purpose of the present application, i.e., welding the nonlinear optical crystal and the heat sink. In order to further improve the firmness and wettability in the subsequent welding process, different metal materials can be selected to be evaporated or magnetron sputtered in a certain order, thickness, and combination to set the metal film structure of different metal materials.

[0046] The inventors have found that the metal film formed on the welding surface of the nonlinear optical crystal has at least two layers, and the outermost layer is a gold layer, which has better welding performance. In addition, the following two metal film structures have the best welding performance:

[0047] (1) The metal film has, from the inside to the outside, a titanium film with a thickness of 5-100 nm, a chromium film with a thickness of 5-100 nm, and a gold film with a thickness of 50-1000 nm;

[0048] (2) The metal film has, from the inside to the outside, a titanium film with a thickness of 5-100 nm, a platinum film with a thickness of 10-100 nm, and a gold film with a thickness of 10-100 nm.

[0049] At the same time, depositing a gold film with a thickness of 10-100 nm on the surface of the heat sink can also have good welding performance.

[0050] Further, the thermal conductivity of the material of the heat sink is 100-400 W / (m·K). The heat sink made of the material with high thermal conductivity can improve the heat conduction rate of the nonlinear optical crystal, and help to improve the temperature field stability of the nonlinear optical crystal. Preferably, the material of the heat sink is oxygen-free copper, copper-tungsten alloy, diamond, silicon carbide, or silicon nitride.

[0051] In some preferred embodiments of the present application, before step S1, the method further comprises a step of surface treatment of the welding surface of the nonlinear optical crystal and the heat sink. After the surface treatment, the welding surface meets the following requirements: cleanliness ≤0.1 mg / cm 2 , flatness ≤0.5λ, λ=632.8 nm, and smoothness ≤40 / 20. When the welding surface of the nonlinear optical crystal and the heat sink meets the above requirements, the metal film formed during the metallization process is more firm, more flat and uniform, which helps to improve the subsequent welding quality.

[0052] Step S2: placing the brazing filler metal between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink, and making the three in close contact to form a welded body;

[0053] Further, the method of placing the brazing filler metal between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink includes the following two methods: (1) depositing the brazing filler metal on the welding surface of the heat sink by evaporation or magnetron sputtering to form a brazing filler metal layer. This method can accurately control the thickness of the brazing filler metal, and the brazing filler metal is flat and uniform, and the brazing filler metal is also free of pollution. However, the process is complex and the cost is high.

[0054] (2) processing the brazing filler metal into a welding sheet similar in shape to the welding surface, and then placing the welding sheet between the nonlinear optical crystal and the heat sink. This method is simple to operate, but the thickness of the brazing filler metal is not easy to control, and the brazing filler metal sheet is not easy to be flat and uniform on the welding surface, and impurities may exist in the heat sink, the brazing filler metal, and the nonlinear crystal, which affects the welding quality.

[0055] Further, the thickness of the brazing filler metal layer or the welding sheet is 5-200 μm, preferably 10-150 μm. Further, the brazing filler metal is an intermetallic compound or a metal alloy containing at least one of tin, lead, zinc, indium, silver, gold, cadmium, bismuth, copper, and antimony. More preferably, the brazing filler metal includes PbSn 40 , SnZn9In5, AuSn 90 , SnAg 3.5 , SnCu1, Sn, Bi, AuSn 20 , PbSn5Ag 2.5 , SnSb8, PbIn5Ag 2.5 , Pb, SnAu5, InBi 22 , PbSn40 Bi 20 , PbBi 40 Sn 20 , InAg2, InSn 48 , InPb 15 Ag2, SnPb 29 In 17.5 Zn 0.5 , In, Sn 70 Pb 18 In 12 , PbSn 36 Ag2, PbIn 50 and SnPb 40 .

[0056] Step S3: placing the soldering body in a controllable atmosphere environment for vacuum reflow soldering.

[0057] The vacuum reflow soldering is performed by placing the soldering body obtained in step S2 in a vacuum, controllable atmosphere eutectic furnace, vacuumizing, and then heating.

[0058] Further, the method of vacuum reflow soldering comprises: vacuumizing the environment where the soldering body is located to a pressure of 6x10 -3 ~ 1x10 -4 , heating to a temperature above the melting point of the soldering material (usually 100~600℃), holding for 3~30min, and then cooling to room temperature.

[0059] wherein the heating rate is 800~1200℃ / h, preferably 1000℃ / h; the holding time is 3~30min, and the holding time is affected by the nonlinear crystal and the material and size of the heat sink, and needs to be determined by experimental results.

[0060] Further, the method of vacuum reflow soldering comprises: vacuumizing the environment where the soldering body is located to a pressure of 6x10 -3 ~ 1x10 -4 , filling a mixed gas containing hydrogen or nitrogen to a pressure of 1x10 3 Pa~1.5x10 5 Pa in the environment where the soldering body is located, holding for 3~30min, and then cooling to room temperature.

[0061] wherein the filled gas can be: hydrogen, hydrogen and nitrogen, formic acid and nitrogen, formic acid, hydrogen and nitrogen.

[0062] Further, the method of vacuum reflow soldering comprises: vacuumizing the environment where the soldering body is located to a pressure of 6x10 -3 ~ 1x10 -4, the pressure of the mixed gas containing hydrogen or nitrogen filled into the environment where the welding body is located is 1 x 10 3 Pa~1.5 x 10 5 Pa, and the welding body is kept for 3~30 min, then the environment where the welding body is located is vacuumized or filled with nitrogen for atmosphere protection, and the temperature is decreased to room temperature.

[0063] More preferably, the cooling rate is 300~500℃ / h, preferably 350~450℃ / h. The rapid cooling with the cooling rate in this range is helpful to form specific intermetallic compounds.

[0064] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely used for illustration and explanation of the present application, and are not used for limiting the present application.

[0065] Embodiment

[0066] Embodiment 1

[0067] The present embodiment provides a nonlinear optical crystal package, which is prepared by the following packaging method:

[0068] (1) The surface of the nonlinear optical crystal BBO (β-phase barium metaborate) to be welded is treated to achieve: cleanliness≤0.1 mg / cm 2 , flatness≤0.5λ, λ=632.8 nm, and smoothness≤40 / 20.

[0069] (2) The surfaces to be welded of the nonlinear optical crystal BBO are sequentially deposited with titanium, platinum-gold, and gold metal by using the magnetron sputtering method to form a metal film, wherein the thickness of the titanium film is 100 nm, the thickness of the platinum-gold film is 280 nm, and the thickness of the outermost gold film is 1000 nm.

[0070] (3) The surface of the heat sink made of oxygen-free copper is deposited with a gold layer by using the magnetron sputtering method, and the thickness of the gold layer is 100 nm.

[0071] (4) The surface of the gold layer in step (3) is deposited with a brazing filler (indium filler is selected) by using the magnetron sputtering method to form a brazing filler layer with a thickness of 100 μm.

[0072] (5) The nonlinear optical crystal BBO and the welding surface of the heat sink plated with the indium brazing filler are tightly contacted by using a tooling fixture to form a welding body, and the welding body is placed into a vacuum eutectic furnace as a whole.

[0073] (6) First, the vacuum eutectic furnace is vacuumized to 6 x 10 -3 Pa, and the mixed gas of nitrogen and hydrogen (5% hydrogen + 95% nitrogen) is filled to a pressure of 1 x 10 5Pa, and then heated to 180°C at a heating rate of 1000°C / h, and then kept for 10 min, and then the vacuum eutectic furnace was vacuumed to 6x10 -3 Pa, and then the solder body was cooled to room temperature at a cooling rate of 500°C / h.

[0074] Example 2

[0075] The present example provides a nonlinear optical crystal package, which is prepared by the following packaging method:

[0076] (1) The surface of the nonlinear optical crystal BBO (β-phase barium metaborate) to be soldered is treated to achieve: cleanliness ≤0.1 mg / cm 2 , flatness ≤0.5λ, λ=632.8 nm, and smoothness ≤40 / 20.

[0077] (2) A titanium, platinum-gold, and gold metal are sequentially deposited on the soldering surface of the nonlinear optical crystal BBO by using a magnetron sputtering method to form a metal film, wherein the thickness of the titanium film is 100 nm, the thickness of the platinum-gold film is 280 nm, and the thickness of the outermost gold film is 1000 nm.

[0078] (3) A gold layer is deposited on the surface of a heat sink made of oxygen-free copper by using a magnetron sputtering method, and the thickness of the gold layer is 100 nm.

[0079] (4) The gold-tin solder sheet (AuSn 20 ) is cut into the same size as the soldering area, and the gold-tin solder sheet is laid on the soldering surface of the heat sink. The thickness of the gold-tin solder sheet used is 100 μm.

[0080] (5) The LBO is tightly contacted with the soldering surface of the heat sink on which the gold-tin solder sheet is laid by using a tooling fixture to form a solder body, and the solder body is placed in a vacuum eutectic furnace as a whole.

[0081] (6) First, the vacuum eutectic furnace is vacuumed to 6x10 -3 Pa, and then heated to 300°C at a heating rate of 1000°C / h, and then kept for 5 min, and then the solder body 1 is cooled to room temperature at a cooling rate of 500°C / h.

[0082] Example 3

[0083] The present example provides a nonlinear optical crystal package, which is prepared by the following packaging method:

[0084] (1) The surface of the lithium niobate crystal (LiNbO3) to be soldered is treated to achieve: cleanliness ≤0.1 mg / cm 2 , flatness ≤0.5λ, λ=632.8 nm, and smoothness ≤40 / 20.

[0085] (2) Using magnetron sputtering method, depositing titanium, platinum and gold on the welding surface of lithium niobate crystal in sequence to form a metal film, wherein the thickness of titanium film is 100 nm, the thickness of platinum film is 280 nm, and the thickness of the outermost gold film is 1000 nm.

[0086] (3) Using magnetron sputtering method, depositing gold layer on the surface of heat sink made of silicon carbide, and the thickness of gold layer is 100 nm.

[0087] (4) Using magnetron sputtering method, sputtering lead indium solder (PbIn50) onto the surface of gold layer of silicon carbide heat sink, and the thickness of deposited solder is 120 μm.

[0088] (5) Using tooling fixture, tightly contacting lithium niobate crystal with the welding surface of heat sink plated with lead indium solder layer to form a welding body, and putting the welding body into vacuum eutectic furnace as a whole.

[0089] (6) First, vacuuming the vacuum eutectic furnace to 6x10 -3 Pa, then heating to 250℃ at a heating rate of 1000℃ / h, then keeping the temperature for 3 min, and then cooling the welding body to room temperature at a cooling rate of 500℃ / h.

[0090] Example 4

[0091] The embodiment provides a nonlinear optical crystal packaging body, which is prepared by using the following packaging method.

[0092] (1) Surface treating the welding surface of LBO (lithium triborate crystal) to reach: cleanliness ≤0.1 mg / cm 2 , flatness ≤0.5λ, λ=632.8 nm, and smoothness ≤40 / 20.

[0093] (2) Using magnetron sputtering method, depositing titanium, platinum and gold on the welding surface of lithium niobate crystal in sequence to form a metal film, wherein the thickness of titanium film is 100 nm, the thickness of platinum film is 280 nm, and the thickness of the outermost gold film is 1000 nm.

[0094] (3) Using magnetron sputtering method, depositing gold layer on the surface of heat sink made of oxygen-free copper, and the thickness of gold layer is 100 nm.

[0095] (4) Using magnetron sputtering method, sputtering indium solder onto the surface of gold layer of heat sink, and the thickness of deposited solder is 120 μm.

[0096] (5) Using tooling fixture, tightly contacting lithium niobate crystal with the welding surface of heat sink plated with indium solder to form a welding body, and putting the welding body into vacuum eutectic furnace as a whole.

[0097] (6) First, vacuuming the vacuum eutectic furnace to 6x10 -3Pa, and the mixed gas of nitrogen and hydrogen (5% hydrogen + 95% nitrogen) was filled to a pressure of 1 x 10 5 Pa, and heated to 180°C at a heating rate of 1000°C / h, then kept for 10 min, and then the vacuum eutectic furnace was vacuumed to 6 x 10 -3 Pa, and the solder body was cooled to room temperature at a cooling rate of 500°C / h.

[0098] Comparative Example

[0099] Comparative Example 1

[0100] This comparative example provides a packaging method of a nonlinear optical crystal, steps (1)-(3) of which are consistent with those of Example 4, except that the method does not perform soldering, specifically:

[0101] The surface of LBO that needs to be cooled is covered with an indium foil (purity ≥ 99.999%) with a thickness of 100 μm. Then the LBO crystal surface covered with the indium foil is tightly contacted with the heat sink through a fixture.

[0102] Comparative Example 2

[0103] This comparative example provides a packaging method of a nonlinear optical crystal, steps (1)-(3) of which are consistent with those of Example 4, except that the method does not perform soldering, specifically:

[0104] The surface of LBO that needs to be cooled is covered with a heat-conducting silica gel pad (thermal conductivity 10 W / m.k) with a thickness of 100 μm. Then the LBO crystal surface covered with the heat-conducting silica gel pad is tightly contacted with the heat sink through a fixture.

[0105] Comparative Example 3

[0106] This comparative example provides a packaging method of a nonlinear optical crystal, steps (1)-(4) of which are consistent with those of Example 3, except that the vacuum reflow soldering is not used for soldering, but the soldering is performed by heating to the melting point of the solder in an atmospheric environment, specifically:

[0107] The lithium niobate crystal is tightly contacted with the solder surface of the heat sink plated with a lead-indium solder layer through a fixture to form a solder body, and the solder body is placed on a heating platform or a container with a heating function, then heated to 250°C at a heating rate of 1000°C / h, then kept for 3 min, and then cooled to room temperature at a cooling rate of 500°C / h.

[0108] Comparative Example 4

[0109] The comparative example 1 provides a packaging method of a nonlinear optical crystal, which is basically the same as that of the example 1, except that the step of metallizing the welding surfaces of the nonlinear optical crystal and the heat sink is not performed. As a result, the BBO crystal is not effectively connected with the heat sink, and is separated by a slight touch.

[0110] Performance detection test

[0111] The nonlinear optical crystal packaging bodies obtained in the examples 1-4 and the comparative examples 1-4 are subjected to performance detection, so as to illustrate the beneficial effects of the present application.

[0112] Detection method / test method

[0113] The same size specifications are used for the crystals of the examples and the comparative examples, and the same size specifications are used for the heat sinks. The same Ophir laser power meter is used to measure the power of the required signal light, and the M2 instrument produced by Ophir-Spiricon is used to measure the laser beam quality of the signal light; the required pulling force when the crystal and the heat sink are disconnected is measured by the method of hanging a weight.

[0114] The detection results are shown in Table 1:

[0115] Table 1. Performance test results of nonlinear optical crystal packaging bodies

[0116]

[0117]

[0118] From the above measurement results in Table 1, it can be seen that, relative to the comparative examples 1-4, the packaging bodies provided in the examples 1-4 of the present application are more excellent and have more advantages in intensity, generated laser power stability and laser beam quality. At the same time, as known from the comparative example 3, the packaging body obtained by not using vacuum reflow soldering and using heating to the melting point of the solder in an atmospheric environment requires only a small pulling force (87 N) to separate the nonlinear crystal from the heat sink, which indicates that the firmness of the welding in the comparative example 3 is poor relative to the vacuum reflow soldering of the present application. For the comparative example 4, under the premise that the welding surfaces of the nonlinear optical crystal and the heat sink are not subjected to the metallization plating treatment, the nonlinear crystal and the heat sink cannot form an effective connection, which indicates that the metallization plating treatment of the welding surfaces in the present application helps to form a more firm connection between the nonlinear crystal and the heat sink.

[0119] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contributions after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method of soldering a nonlinear optical crystal to a heat sink, comprising: It comprises: The welding surface of the nonlinear optical crystal and the heat sink are respectively subjected to metallization plating treatment, the method of the metallization plating treatment comprises: using a metal material to form a metal film on the welding surface of the nonlinear optical crystal by using an evaporation method or a magnetron sputtering method, the metal film has three layers, and the outermost layer is gold, and the layers from inside to outside are: a titanium film with a thickness of 5-100 nm, a platinum-gold film with a thickness of 10-100 nm, and a gold film with a thickness of 50-1000 nm; a gold film with a thickness of 10-100 nm is deposited on the welding surface of the heat sink; A brazing filler metal is arranged between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink, and the three are in close contact to form a welding body; The welding body is placed in a controllable atmosphere environment to perform vacuum reflow soldering, and the method of the vacuum reflow soldering comprises: The pressure in the environment where the soldering body is located is 6 x 10 -3 ~ 1 x 10 -4 Pa, the mixed gas containing formic acid, hydrogen or nitrogen is filled to the pressure in the environment where the soldering body is located is 1 x 10 3 Pa ~ 1.5 x 10 5 Pa, then heated to the melting point temperature of the soldering material, and kept for 3 ~ 30 min, then the environment where the soldering body is located is vacuumized or filled with nitrogen for atmosphere protection, and then cooled to room temperature at a cooling rate of 300 ~ 500 ℃ / h.

2. The method of claim 1, wherein the non-linear optical crystal is a lithium borate crystal. The method of arranging the brazing filler metal between the welding surface of the nonlinear optical crystal and the welding surface of the heat sink comprises: The brazing filler metal is deposited on the welding surface of the heat sink to form a solder layer; Or, the brazing filler metal is processed into a solder sheet similar in shape to the welding surface, and then the solder sheet is placed between the nonlinear optical crystal and the heat sink.

3. The method of claim 2, wherein the non-linear optical crystal is a lithium triborate (LBO) crystal. The thickness of the solder layer or the solder sheet is 5-200 um.

4. The method of claim 1, wherein the non-linear optical crystal is a lithium borate crystal. The thermal conductivity of the material of the heat sink is 100-400 W / (m·K).

5. A nonlinear optical crystal package, comprising: It is prepared by the welding packaging method according to any one of claims 1-4.

Images