An ultrafast laser joining method for transparent ceramics and metals

Abstract

A method for ultrafast laser connection of transparent ceramics and metals belongs to the new technical field of ultrafast laser connection. The method comprises the following steps: 1) pretreatment of the surfaces of the transparent ceramics and metals to be connected; 2) fixation and placement of the transparent ceramics and metals to be connected; 3) connection by ultrafast laser system. The present invention solves the problem that transparent ceramics and metals are difficult to connect directly without adding any intermediate layer due to the large difference in physical and chemical properties. The method realizes the high-reliability, low-stress and high-precision integrated preparation and effective regulation of ultrafast laser micro-connection joints of transparent ceramics and metals, and obtains high-precision and high-reliability micro-connection joints with excellent comprehensive mechanical properties. The shear strength of the joint is increased compared with the traditional connection method.

Description

Technical Field

[0001] The invention relates to the technical field of ultrafast laser transparent ceramic and metal connection, and in particular provides a new ultrafast laser connection method for transparent ceramic and metal. Background Art

[0002] At present, the connection between transparent ceramics and metals at home and abroad is mainly achieved by bonding, mechanical connection, diffusion welding and active brazing. Among them, bonding is simple to operate and widely applicable, but it has disadvantages such as easy degassing, bleaching, softening and aging of the adhesive; mechanical connection involves complex processes such as drilling, and the connection structure is complex, which affects the visual range of transparent ceramics to a certain extent; the connection components of active brazing and diffusion welding have the advantages of high strength and good air tightness, but the welding process takes a long time, and usually requires the insertion of an intermediate layer or a brazing material layer to regulate the interface reaction or relieve residual stress, and requires pressure assistance, which undoubtedly brings additional complexity to the connection process and greatly limits the promotion and application of this method. Therefore, although the above-mentioned traditional connection methods can achieve good connection effects, there are still certain restrictions in terms of joint strength, connection accuracy and connection efficiency.

[0003] In recent years, the rapid development of ultrafast lasers has provided a new powerful tool for precise and efficient connection of materials. The nonlinear absorption effect of ultrafast lasers has provided new possibilities for efficient and reliable connection between transparent ceramics and metals.

[0004] At present, patent reports on ultrafast laser connection are only for the connection between glass materials / metal materials and ceramic materials / ceramic materials, such as CN202011605205.4, CN201911220520.2, CN111574238A, etc. No relevant reports on ultrafast laser connection of ceramic materials and metal materials have been found. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrafast laser connection method for transparent ceramics and metals, aiming to improve the joint strength, joint accuracy and connection efficiency, so as to solve some defects in the prior art.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide an ultrafast laser connection method for transparent ceramics and metals, comprising the following steps:

[0007] 1) Surface pretreatment of the transparent ceramic and metal to be connected: the transparent ceramic to be connected is subjected to double-sided mechanical polishing step by step with 1000#~3000# diamond grinding discs, and double-sided polishing is performed on a synthetic leather polymer material black polishing cloth; the metal to be connected is subjected to single-sided mechanical polishing step by step with 280#~2000# sandpaper, and then polished to a mirror surface using a nylon polishing cloth on a polishing machine; the polished transparent ceramic and metal to be connected are ultrasonically cleaned and blown dry;

[0008] 2) Fixing and placing the transparent ceramic and metal to be connected: The pre-treated transparent ceramic and metal stack are fixed and clamped with a clamp, and the transparent ceramic and metal to be connected fixed by the clamp are placed in the laser processing area;

[0009] 3) Ultrafast laser system connection: adjust the focus of the ultrafast laser beam so that it is focused on the interface between the transparent ceramic and the metal to be connected; then, set the output power, pulse width, repetition frequency, scanning path, scanning speed, scanning line spacing, number of scans and other parameters of the ultrafast laser for ultrafast laser welding.

[0010] Preferably, in the step 1), the transparent ceramics used include sapphire (single crystal alumina ceramics), white corundum, magnesium oxide, beryllium oxide, yttrium oxide, yttrium oxide-zirconium dioxide and other oxide series transparent ceramics and gallium arsenide, zinc sulfide, zinc selenide, magnesium fluoride, calcium fluoride, magnesium aluminate and other non-oxide transparent ceramics.

[0011] Preferably, in the step 1), the metal material used is common metal materials such as copper, Ti and Ti alloys, stainless steel, and various Fe-Ni alloys.

[0012] Preferably, in the step 1), the polishing method of the transparent ceramic to be connected is as follows: first, use a diamond polishing agent with a particle size of 0.5 to 2 μm on a synthetic leather polymer material black polishing cloth for 10 to 20 minutes, and then use clean water to polish on the same synthetic leather polymer material black polishing cloth for 5 to 10 minutes.

[0013] Preferably, in the step 2), the clamp is designed to allow the transparent ceramic and the metal to be in close contact without affecting the ultrafast laser connection process, and the gap between the transparent ceramic and the metal is less than 1 micron.

[0014] Preferably, in the step 3), the ultrafast laser is a femtosecond laser or a picosecond laser.

[0015] Preferably, in the step 3), the ultrafast laser beam type is a common Gaussian beam.

[0016] Preferably, in the step 3), the laser scanning path is a special pattern, including: parallel lines, crosses, concentric rectangles, concentric circles, spiral lines, etc.

[0017] Preferably, in the step 3), due to the high spatial selectivity of ultrafast laser, the ultrafast laser connection of transparent ceramic / metal joints is various in form, including overlapping and butting, etc.; when transparent ceramic / metal is overlapped, the transparent ceramic is located on the metal, and the laser first acts on the transparent ceramic and passes through the transparent ceramic to directly act on the transparent ceramic / metal overlapping interface; if the transparent ceramic / metal is butted, the transparent ceramic / metal is butted on the same plane, and the laser acts directly on the butt joint.

[0018] Preferably, in the step 3), the parameters for ultrafast laser welding are as follows: pulse width between 250fs and 10ps, laser repetition frequency between 1KHz and 2MHz, laser power between 4 and 40W, laser spot diameter between 20 and 60μm, laser scanning speed between 10 and 1000mm / s, scanning line spacing between 20μm and 1mm, and scanning times between 1 and 10 times.

[0019] The present invention proposes a new transparent ceramic and metal connection technology, which is a new method never involved in previous patents and solves some shortcomings of the traditional transparent ceramic and metal connection method.

[0020] The present invention utilizes the characteristics of ultrafast pulse lasers that can achieve nonlinear absorption in transparent materials, so that transparent ceramics and metal materials can achieve strong bonding between materials in a very small range near the focal area, effectively avoiding excessive heat accumulation in the material, thereby not causing overheating and expansion of transparent ceramics to produce cracks, and helping to improve the welding accuracy and quality of transparent ceramics and metals. Compared with traditional transparent ceramic and metal connection methods, the present invention solves the problems of large joint residual stress, low efficiency, cumbersome process, and low precision in transparent ceramic and metal connections. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a parallel linear scanning path according to an embodiment of the present invention (not to actual scale);

[0022] Figure 2 It is a displacement-test force curve diagram of the shear force test of the welded joint according to an embodiment of the present invention (the horizontal axis unit is mm, the vertical axis unit is KN);

[0023] Figure 3 This is a SEM microstructure diagram of the transparent ceramic (sapphire) / metal (4J36 Invar alloy) connection interface of an embodiment of the present invention;

[0024] Figure 4 Connecting systems for ultrafast laser systems. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] An ultrafast laser joining method for transparent ceramics and metals is carried out in the following steps:

[0028] 1) Surface pretreatment of the transparent ceramic and metal to be connected: The transparent ceramic material to be connected in this embodiment is sapphire (thickness is 3 mm); the metal material to be connected in this embodiment is 4J36 Invar alloy; the transparent ceramic (sapphire) to be connected is subjected to double-sided mechanical grinding step by step using 1000#, 1500#, 2000#, and 3000# diamond grinding discs, respectively, and double-sided polishing is performed on a synthetic leather polymer material black polishing cloth. The specific polishing method is: use a diamond polishing agent with a particle size of 1 μm on a synthetic leather polymer material black polishing cloth for 10 to 20 minutes, and then use clean water on the same synthetic leather polymer material black polishing cloth for 5 to 10 minutes ... The metal (4J36 Invar alloy) is mechanically polished on one side step by step with 280#, 600#, 1000#, and 2000# sandpapers, and then the polished metal (4J36 Invar alloy) is polished on a polishing machine using a nylon polishing cloth. The specific polishing method is: use 2.5μm, 1μm, and 0.5μm diamond grinding pastes on nylon polishing cloths to polish to a mirror surface step by step; then the polished transparent ceramic (sapphire) and metal (4J36 Invar alloy) are placed in anhydrous ethanol, and ultrasonically cleaned for about 10 minutes at a frequency of 80Hz, and then the cleaned transparent ceramic (sapphire) and metal (4J36 Invar alloy) are taken out with tweezers and blown dry. The sapphire to be connected can also be a commercial double-sided polished sapphire of the same thickness (3mm);

[0029] 2) Fixing and placing the transparent ceramic and metal to be connected: Place the pre-treated transparent ceramic (sapphire) on the metal (4J36 Invar alloy) and stack them in the fixture. The fixture is designed to allow the transparent ceramic (sapphire) and metal (4J36 Invar alloy) to be in close contact without affecting the ultrafast laser welding process. In addition, the gap between the transparent ceramic (sapphire) and the metal (4J36 Invar alloy) can be adjusted by adjusting the clamping force of the fixture. To ensure the accuracy and strength of ultrafast laser welding of transparent ceramic (sapphire) and metal (4J36 Invar alloy), adjust the clamping force of the fixture so that Newton rings appear when the transparent ceramic (sapphire) and metal (4J36 Invar alloy) are stacked. At this time, the gap between the transparent ceramic (sapphire) and the metal (4J36 Invar alloy) is less than 1 micron.

[0030] 3) Ultrafast laser connection, see Figure 4 : Place the transparent ceramic (sapphire) and metal (4J36 Invar alloy) clamped by the fixture on the laser processing platform, adjust the fixture placement through the laser indicator to ensure the preset scanning position of the ultrafast laser; adjust the focus position of the ultrafast laser beam to pass through the transparent ceramic (sapphire) and focus on the interface to be connected between the transparent ceramic (sapphire) and the metal (4J36 Invar alloy); then, set the parameters of the ultrafast laser on the laser operating system, including: output power, pulse width, repetition frequency, scanning path, scanning speed, scanning line spacing, scanning times, etc. After confirming that the information is correct, control the laser to emit laser for welding.

[0031] As an optimization solution of the embodiment of the present invention, the ultrafast laser used is a femtosecond laser; the specific laser parameters are: pulse width of 800fs, repetition frequency of 200KHz, power of 8W, spot diameter of 36μm, scanning speed of 100mm / s, scanning number of 1 times, and scanning area of ​​20mm 2 The scanning path is parallel linear, such as Figure 1 As shown, the line spacing L of the parallel linear paths is 72 μm, and the scanning area is filled according to this standard; the joint form of the ultrafast laser connecting transparent ceramic (sapphire) / metal (4J36 Invar alloy) is overlap.

[0032] As an optimization solution of the embodiment of the present invention, the laser scanning path has other special patterns besides parallel linear patterns, including: cross-shaped, concentric rectangular, concentric circular, spiral line, etc.

[0033] As an optimization scheme of the embodiment of the present invention, due to the high spatial selectivity of ultrafast laser, ultrafast laser connection of transparent ceramic / metal joints has various forms, including butt joint and other forms besides overlap.

[0034] Experimental test: After the connection is completed, the shear strength of the welded joint is tested. Figure 2It can be seen that when the test force reaches 2236N, the weld joint breaks. From the shear strength formula P=F / S, it can be seen that F is the maximum shear force when the weld joint breaks, and S can be approximated as the scanning area, so the tensile shear strength of the transparent ceramic (sapphire) / metal (4J36 Invar alloy) lap joint can be calculated, which is about 112MPa. The connected transparent ceramic (sapphire) and metal (4J36 Invar alloy) workpieces are cut along the vertical aspect of the connection interface, and the transparent ceramic (sapphire) / metal (4J36 Invar alloy) connection interface is ground, polished, and gold-sprayed. Then, the microstructure of the transparent ceramic (sapphire) / metal (4J36 Invar alloy) connection interface is observed under SEM. It is found that the transparent ceramic (sapphire) / metal (4J36 Invar alloy) connection interface is staggered, and relatively more metal (4J36 Invar alloy) particles enter the transparent ceramic (sapphire) side. The joint width does not exceed 1 micron, with submicron connection accuracy, such as Figure 3 shown.

Claims

1. An ultrafast laser connection method for transparent ceramics and metals, characterized in that: The following steps are involved: 1) Surface pretreatment of the transparent ceramic and metal to be connected: the transparent ceramic to be connected is subjected to double-sided mechanical polishing step by step with 1000#~3000# diamond grinding discs, and double-sided polishing is performed on a synthetic leather polymer material black polishing cloth; the metal to be connected is subjected to single-sided mechanical polishing step by step with 280#~2000# sandpaper, and then polished to a mirror surface using a nylon polishing cloth on a polishing machine; the polished transparent ceramic and metal to be connected are ultrasonically cleaned and blown dry; 2) Fixing and placing the transparent ceramic and metal to be connected: The pre-treated transparent ceramic and metal stack are fixed and clamped with a clamp, and the transparent ceramic and metal to be connected fixed by the clamp are placed in the laser processing area; 3) Ultrafast laser system connection: adjust the focus of the ultrafast laser beam to focus on the interface between the transparent ceramic and the metal to be connected; then, set the output power, pulse width, repetition frequency, scanning path, scanning speed, scanning line spacing, and scanning times of the ultrafast laser to perform ultrafast laser welding; The transparent ceramic material to be connected is sapphire with a thickness of 3 mm, and the metal material to be connected is 4J36 Invar alloy; The ultrafast laser used is a femtosecond laser; the specific laser parameters are: pulse width 800fs, repetition frequency 200KHz, power 8W, spot diameter 36μm, scanning speed 100mm / s, scanning number 1, scanning area 20mm 2 The scanning path is a parallel linear path, where the line spacing L of the parallel linear path is 72μm, and the scanning area is filled according to this standard; the ultrafast laser connection of transparent ceramic / metal joints is overlapped, and the gap between transparent ceramic and metal is less than 1 micron; the tensile shear strength of the transparent ceramic / metal overlap joint is 112MPa; the transparent ceramic / metal connection interface is staggered, and relatively more metal particles enter the transparent ceramic side, the joint width does not exceed 1 micron, and has submicron connection accuracy.

Images