A welding method for a new type of crystal plate bar and disc

Abstract

The present invention relates to the technical field of laser manufacturing, and particularly discloses a welding method for a novel crystal slab and disc, comprising the following steps: plating a gold film on the welding surfaces of a heat sink and a laser amplification medium, plating a special film layer on the gold film, assembling an indium solder sheet, the heat sink plated with the special film layer, and the laser amplification medium plated with the special film layer into an assembly, placing the assembly in a welding furnace, and heating and pressurizing for welding, so that an interfacial micro-region eutectic reaction occurs between the special film layer and the surface of the indium solder sheet to fill the weld seam of the welding surface. Compared with the traditional technology, this technical solution effectively avoids the pollution and voids generated by the large-scale melting of the solder. Since the pressure applied during welding is small, it avoids the problem that the stress of the solid laser is too large to retreat easily, solves the defects generated during the laser welding process, ensures the performance and working reliability of the laser, and provides a method for the solid laser to generate a higher power and better beam quality.

Description

Technical Field

[0001] The present invention relates to the technical field of laser manufacturing, and particularly to a welding method for a novel crystal plate and disc. Background Art

[0002] Solid-state lasers have extensive applications and development potential in many fields such as medical treatment, industrial processing, scientific research, and military. Therefore, high power and high beam quality have become important indicators in the research of the laser technology field. However, there is a paradox in the research process, that is, as the output power of the laser increases, the beam quality will gradually deteriorate. The main reason for this paradox is the strong thermal effect generated by the laser gain medium itself during the high-power operation of the solid-state laser. Breaking through the internal thermal effect is the key to obtaining high-power and high-beam-quality lasers.

[0003] At present, the welding and encapsulation of most solid-state lasers are realized with indium solder, mainly adopting two methods: indium evaporation and indium solder sheet. In indium evaporation welding, indium is used as a coating and deposited on the welding surface by evaporation. The thickness of the deposited indium layer is relatively thin, basically about dozens of micrometers. After exceeding a certain thickness, the surface of the evaporated indium layer is uneven, the welding layer is thin and uneven, resulting in a mismatch in the thermal expansion coefficients between the laser gain medium and the heat sink, affecting the beam quality of the laser. At the same time, there are also easily welding defects, which affect the heat conduction inside the crystal, generating large thermal stresses. For example, the patent with the publication number CN109361138A proposes a method for encapsulating a slab laser gain medium. Based on indium evaporation welding, a method of sandwiching a transition piece is selected, which reduces the welding stress between the laser gain medium and the heat sink to a certain extent and reduces the thermal distortion of the welding layer during the operation of the laser gain medium. However, its technical solution selects a temperature range of 170 - 260 °C, while the melting point of indium is 156 °C. In the selected temperature range, indium has melted, which is a typical soldering reaction. There are easily welding voids between the molten indium and the solid gold film and the transition piece, affecting heat dissipation to a certain extent. And for the welding and encapsulation of large-sized slabs, the requirement for flatness is relatively high. During the process of indium evaporation, temperature differences inevitably exist, resulting in inconsistent thickness of the indium coating around the large-sized slab and in the middle, causing a decrease in flatness. This technical solution also does not solve the problem of welding and encapsulation of large-sized slabs; Indium solder sheet welding is a process where the indium solder sheet melts and then solidifies. Under the action of gravity and surface tension, the molten solder is not easy to control and may flow to the welding surface of the lower heat sink, resulting in a serious uneven distribution of the solder in the welding layer. Inevitably, uneven heat dissipation and stress distribution occur, exacerbating the thermal effect of the laser gain medium and seriously affecting the performance of the solid-state laser.

[0004] Therefore, it is necessary to propose a welding method for a novel crystal plate and disc to improve the heat dissipation effect and the performance of the solid-state laser. Summary of the Invention

[0005] The object of the present invention is to solve the problem that the solder distribution of the welding layer of the existing solid-state laser is seriously uneven, resulting in poor heat dissipation effect of the solid-state laser, and a new welding method for crystal slabs and discs is provided.

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

[0007] A new welding method for crystal slabs and discs, comprising the following steps:

[0008] Deposit a gold film on the welding surface of the heat sink and the welding surface of the laser amplification medium, and deposit a special film layer on this gold film;

[0009] Assemble the indium solder sheet, the heat sink with the special film layer deposited thereon, and the laser amplification medium with the special film layer deposited thereon into an assembly;

[0010] Put the assembly into a welding furnace, and perform heating and pressure welding. The heating temperature is between 110 °C and 150 °C, so that an interfacial micro-region eutectic reaction occurs on the surface of the special film layer and the indium solder sheet, and then full diffusion is carried out to complete the welding.

[0011] Further, the special film layer is a silver film or a tin film.

[0012] Further, the thickness of the silver film or the tin film is 100 nm - 1000 nm.

[0013] Further, the thickness of the indium solder sheet is 0.1 mm - 0.8 mm.

[0014] Further, the welding furnace is in a vacuum state during the welding of the assembly.

[0015] Further, the pressure applied during the welding of the assembly is 0.1 Mpa - 0.5 Mpa.

[0016] Further, the laser amplification medium is a crystal slab or a disc.

[0017] A novel welding method for a crystal plate bar and a disc of the present invention utilizes the interfacial eutectic reaction between a special film layer and indium solder to obtain a micro-region liquid phase, so as to accelerate the rapid reaction between indium and a gold film to complete the welding of a solid laser while ensuring that the indium solder does not melt. The unmelted indium solder sheet will not have welding voids during welding, ensuring the heat dissipation effect. The present invention mainly relies on the close fitting of the special film layer and indium solder under a certain pressure to better achieve the mutual diffusion of intermetallic atoms, forming a low-melting-point eutectic liquid phase at the welding interface at a temperature lower than the melting point of indium as a connection medium for completing welding; indium rapidly reacts with the gold film through the liquid phase to generate another connection medium for completing welding, and the two connection media depend on each other to form a welding joint with uniform composition. Since a local liquid phase appears at the welding interface, the reaction rate is accelerated and the connection pressure is reduced, so the stress generated at the welding surface is small; in addition, the low-melting-point eutectic liquid phase can fill the voids at the welding interface, thereby improving the heat dissipation effect of the solid laser and further enhancing the power and working reliability of the solid laser. Compared with the traditional technology, the technical solution of the present invention uses a temperature lower than the melting point of the solder to effectively avoid the pollution and voids generated by the large-scale melting of the solder. Since the indium solder sheet does not melt, the thickness of the solder can be controlled, thus solving the problem of the mismatch of the thermal expansion coefficients between the heat sink and the laser amplification medium, and also solving the problem of the mismatch of the thermal expansion coefficients in the welding and encapsulation of laser amplification media of various sizes, especially the welding and encapsulation of large-size plate bars, which can not only ensure the welding effect, but also eliminate the thermal stress, ensuring the light output efficiency and working stability of the laser; in addition, since the pressure applied during the welding process is small, the problem that the stress of the solid laser is too large and not easy to retreat is avoided, the defects generated during the welding process of the laser are solved, and the performance and working reliability of the laser are guaranteed, providing a method for the solid laser to generate higher power and better beam quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the present invention;

[0019] Figure 2 is a schematic structural diagram of the assembly a in Embodiment 2 of the present invention;

[0020] Figure 3 is a schematic structural diagram of the assembly b in Embodiment 3 of the present invention;

[0021] Figure 4 is a flow chart of Embodiment 1 of the present invention.

[0022] Reference numerals: 11, lower heat sink of the plate bar; 12, upper heat sink of the plate bar; 13, heat sink of the disc; 2, gold film; 3, special film layer; 4, indium solder sheet; 5, crystal plate bar; 6, disc. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the technical means, technical features, invention purpose and technical effects achieved by the present invention easy to understand, the present invention will be further described below with reference to specific illustrations.

[0024] Embodiment 1:

[0025] As Figure 4 shown, this embodiment provides a welding method for a new type of crystal plate and disc, including the following steps:

[0026] S01: A special film layer 3 is plated on the gold film 2 on the welding surface of the heat sink and the crystal plate 5 or the disc 6;

[0027] S02: The heat sink, indium solder sheet 4, crystal plate 5 or disc 6 are assembled into an assembly in sequence;

[0028] S03: The assembly is moved into a welding furnace, heated and pressed for welding. Through the eutectic reaction in the interface micro-region between the special film layer 3 and the surface of the indium solder sheet 4, the diffusion is completed sufficiently to finish the welding.

[0029] In S01, to ensure the welding effect and the light output effect of the laser, a special film layer 3 is plated on the gold film 2 on the welding surfaces of the heat sink, the crystal plate 5 and the disc 6. The special film layer 3 and the indium solder sheet 4 need to have a eutectic reaction at the interface junction to generate an interface micro-region liquid phase. Therefore, a silver film or a tin film can be selected.

[0030] Preferably, to ensure the welding effect, there is a gold film 2 on the welding surfaces of the heat sink, the crystal plate 5 and the disc 6. The special film layer 3 plated on the gold film 2 is a silver film or a tin film, and the thickness of the silver film or the tin film is 100nm - 1000nm.

[0031] Specifically, the heat sink is divided into the upper heat sink 12 of the plate and the lower heat sink 11 of the plate in the solid-state laser composed of the crystal plate 5, and the heat sink is the disc heat sink 13 in the solid-state laser composed of the disc.

[0032] To ensure the welding effect, in S02, the thickness of the indium solder sheet 4 is 0.1mm - 0.8mm.

[0033] To ensure the effect of the welding assembly and the light output quality of the laser, the welding furnace during the welding of the assembly a or b in S03 is in a vacuum state to prevent the generation of an oxide film / oxidation substance from affecting the welding quality.

[0034] To ensure sufficient diffusion between atoms and complete the welding, the pressure applied during the welding of the assembly is 0.1MPa - 0.5MPa.

[0035] To ensure the local liquefaction in the interface micro-region between the indium solder sheet 4 and the special film layer 3, and to make the atoms between the indium solder sheet 4 and the gold film 2 diffuse sufficiently to complete the reaction, achieving an excellent welding effect, the temperature range during the welding process is 110°C - 150°C.

[0036] Example 2:

[0037] The same parts as in Example 1 will not be described again. The differences are as follows: As Figure 2 shown, a welding method for a new type of crystal plate bar and disc includes the following steps: (1) Select an Nd:YAG crystal plate bar 5 with dimensions of 200mm * 60mm * 10mm. Gold films 2 are plated on the upper and lower welding surfaces of the crystal plate bar 5. Then, silver, which undergoes a eutectic reaction with indium at the interface to generate a liquid phase medium, is selected as the special film layer 3. The thickness of the plated gold film 2 is 400nm, and the thickness of the silver film is 200nm. Similarly, gold films 2 are plated on the lower heat sink 11 and upper heat sink 12 of the plate bar with reserved cooling channels, and silver films are plated on the gold films 2. The coating thickness is the same as that of the crystal plate bar 5.

[0038] (2) Assemble them into an assembly a in the order of the lower heat sink 11 of the plate bar - indium solder sheet 4 - crystal plate bar 5 - indium solder sheet 4 - upper heat sink 12 of the plate bar, where the thickness of the indium solder sheet is 0.4mm.

[0039] (3) Move the assembly a into a vacuum welding furnace. Evacuate the welding furnace cavity to a vacuum state according to the procedure, apply a pressure of 0.3MPa and start the heating program to raise the temperature. When it is heated to 146°C, a liquid phase is generated in the interface micro-region and kept warm for 5 minutes. Then, cool down to 120°C and keep warm for 30 minutes. Turn off the heating and let it cool naturally to room temperature. Take out the assembly a to complete the welding.

[0040] Example 3:

[0041] The same parts as in Example 1 will not be described again. The differences are as follows: As Figure 3 shown, a welding method for a new type of crystal plate bar and disc includes the following steps: (1) Select an Nd:YAG disc 6 with dimensions of φ80mm * 5mm. On the gold film 2 on its lower welding surface, silver, which undergoes a eutectic reaction with indium at the interface to generate a liquid phase medium, is selected as the special film layer 3. The thickness of the plated gold film 2 is 400nm, and the thickness of the silver film is 100nm. Similarly, silver films are plated on the gold films 2 on the welding surface of the disc heat sink 13. The coating thickness is the same as that of the disc crystal.

[0042] (2) Assemble them into an assembly b in the order of the disc heat sink 13 - indium solder sheet 4 - disc 6, where the thickness of the indium solder sheet 4 is 0.1mm.

[0043] (3) Move the assembly b into a vacuum welding furnace. Evacuate the welding furnace to a vacuum state according to the procedure, apply a pressure of 0.1MPa. Apply pressure and heat up at the same time. When it is heated to 150°C, a liquid phase is generated in the interface micro-region and kept warm for 5 minutes. Then, cool down to 120°C and keep warm for 30 minutes. Turn off the heating and let it cool naturally to room temperature. Take out the assembly b to complete the welding.

[0044] In Examples 2 and 3, the special film layer is a silver film. During the welding process, it is first heated to a certain temperature, and the metal atoms between the indium solder and the silver film diffuse with each other to produce a eutectic reaction, resulting in the formation of a liquid alloy at the welding interface, which serves as a connection medium for completing the welding. To ensure that the liquid metal alloy fills the capillary gap, it is necessary to briefly hold the temperature at this temperature first to form a uniform liquid film at the connection interface. Indium reacts rapidly with the gold film 2 through the liquid phase, thereby generating another connection medium for completing the welding. Subsequently, the connection temperature is reduced to a certain temperature for heat preservation to homogenize the solid-phase components of the two connection interfaces. The two connection media depend on each other to form a welding joint with uniform composition. Since a local liquid phase appears at the welding interface, the reaction rate is accelerated and the connection pressure is reduced. The welding thickness is uniform, the heat dissipation effect is excellent, and the stress caused by welding is also small and easy to retreat, improving the beam quality of the laser.

[0045] Example 4:

[0046] The same parts of this example as those of Example 1 will not be described in detail. The differences are as follows: As Figure 1 shown, a welding method for a new type of crystal plate and disc includes the following steps: plating a gold film on the welding surfaces of the heat sink and the Nd:YAG plate crystal of 210mm * 80mm * 12mm, plating a special film layer on the gold film, assembling the heat sink, indium solder, and the plate crystal plated with the special film layer into an assembly, placing the assembly in a welding furnace, and heating and pressurizing for welding to cause an interfacial micro-region eutectic reaction on the surfaces of the special film layer and the indium solder, so that the indium solder and the gold film are rapidly and fully diffusion-connected through the liquid phase generated by the eutectic reaction to complete the welding.

[0047] Preferably, the special film layer is a tin film. Preferably, the thickness of the tin film is 1000 nm. Preferably, the thickness of the indium solder is 0.8 mm. Preferably, the welding furnace is in a vacuum state during the welding of the assembly. Preferably, the pressure applied during the welding of the assembly is 0.5 Mpa. Preferably, the temperature during the welding of the assembly is 120 °C. After the liquid phase is generated in the interfacial micro-region, it is held for 5 min, and then the temperature is reduced to 110 °C and held for 30 min. Then, the heating is turned off and it is naturally cooled to room temperature, and the assembly is taken out to complete the welding.

[0048] Example 5:

[0049] The same parts of this example as those of Example 1 will not be described in detail. The differences are as follows: As Figure 1As shown in the figure, a welding method for a new type of crystal plate and disc includes the following steps: gold plating films are applied on the welding surfaces of the heat sink and the Nd:YAG plate crystal with a size of 180mm * 70mm * 8mm, a special film layer is plated on the gold plating films, the heat sink, the indium solder sheet and the plate crystal plated with the special film layer are assembled into an assembly, the assembly is placed in a welding furnace, and heated and pressurized for welding, so that an interfacial micro-region eutectic reaction occurs on the surface of the special film layer and the indium solder sheet, thereby enabling the indium solder sheet and the gold plating film to be quickly and fully diffusion-connected through the liquid phase generated by the eutectic reaction to complete the welding.

[0050] Preferably, the special film layer is a tin film. Preferably, the thickness of the tin film is 500 nm. Preferably, the thickness of the indium solder sheet is 0.6 mm. Preferably, the welding furnace is in a vacuum state during the welding of the assembly. Preferably, the pressure applied during the welding of the assembly is 0.4 Mpa. Preferably, the temperature during the welding of the assembly is 130 °C. After the liquid phase is generated in the interfacial micro-region, it is kept warm for 5 minutes, cooled to 110 °C, kept warm for 30 minutes, then the heating is turned off and it is naturally cooled to room temperature, and the assembly is taken out to complete the welding.

[0051] In summary, the above are only the preferred embodiments of the present invention and are not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made to the content within the scope of the patent application of the present invention shall fall within the technical scope of the present invention.

Claims

1. A welding method for a new type of crystal plate and disc, characterized in that, It includes the following steps: Gold films (2) are plated on the welding surfaces of the heat sink and the laser amplification medium, and special film layers (3) are plated on the gold films (2); The indium solder sheet (4), the heat sink plated with the special film layer (3), and the laser amplification medium plated with the special film layer (3) are assembled into an assembly; The assembly is placed in a welding furnace and welded by heating and pressurizing. The heating temperature is between 110°C and 150°C, so that an interfacial microzone eutectic reaction occurs on the surface of the special film layer (3) and the indium solder sheet (4), and then the welding is completed by diffusion.

2. The welding method of the novel crystal plate strip and disc according to claim 1, characterized in that: The special film layer (3) is a silver film or a tin film.

3. The welding method of the novel crystal plate strip and disc according to claim 2, characterized in that: The thickness of the silver film or the tin film is 100 nm - 1000 nm.

4. The welding method of the novel crystal plate strip and disc according to claim 1, characterized in that: The thickness of the indium solder sheet (4) is 0.1 mm - 0.8 mm.

5. The welding method of the novel crystal plate bar and disc according to claim 1, characterized in that: The welding furnace is in a vacuum state during the welding of the assembly.

6. The welding method of the novel crystal plate strip and disc according to claim 1, characterized in that: The pressure applied during the welding of the assembly is 0.1 Mpa - 0.5 Mpa.

7. The welding method of the novel crystal plate and disc according to claim 1, characterized in that: The laser amplification medium is a crystal plate (5) or a disk (6).

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