CN113292233A

CN113292233A - Device and method for femtosecond laser welding glass

Info

Publication number: CN113292233A
Application number: CN202110684374.XA
Authority: CN
Inventors: 陈聪; 廖洋; 叶铖润; 刘科; 高文海; 王佳; 谢少明; 冯吉军; 彭宇杰; 冷雨欣; 李儒新
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2021-08-24

Abstract

A device and method for femtosecond laser welding glass, the method comprises the following steps: 1) drop a small amount of liquid on a piece of glass, and then stack another piece of glass, so that the liquid fills the gap of the above-mentioned glass to be welded, and the atmospheric pressure is used to make the glass. The gap is reduced; 2) Focus the femtosecond laser beam with higher single-pulse energy on the contact surface of the two glasses to be welded, and use the scanning galvanometer to scan the laser focus along the closed path at high speed to form a semi-transparent weld at the contact of the two glasses. 3) Finally, use a femtosecond laser beam with a lower single-pulse energy to scan slowly along the above-mentioned translucent welding seam to achieve a final stronger welding. The first high-speed scanning of the present invention can not only reduce the glass gap uniformly, and avoid warping and deformation of the two pieces of glass that are naturally stacked during the welding process; The light absorption during the second scan expands the molten pool volume. The invention can realize the sealing welding of glass with large gap by using femtosecond laser, and has the characteristics of fast welding speed, high welding strength, stable and reliable process, and wide application range.

Description

Device and method for femtosecond laser welding glass

Technical Field

The invention belongs to laser welding, and relates to a device and a method for femtosecond laser welding glass.

Background

The glass material is an indispensable excellent material in production, life and scientific research due to good physicochemical properties such as good light transmission, high transparency, high hardness, corrosion resistance and the like. In the scenes of device packaging, optical device combination and the like, glass materials are often required to be connected, and the strength and the sealing performance of connecting lines are high.

When two or more glass materials are required to be connected in the application process, methods of adding solder for welding, gluing and high-temperature heating for welding are generally used at present. The glass is welded by adding the solder, and the chemical stability is poor due to the difference between the solder and the substrate material. And the glue is easily affected by high temperature and is easy to age and not long in service life when connected in a gluing mode. The high temperature heat welding can cause obvious deformation at the interface, and the performance of the device is influenced. The above methods all have obvious disadvantages and cannot meet the production requirements brought by the technical development, so that a new precise connection processing mode is needed at present.

The ultrafast laser has extremely high peak power density, can generate nonlinear multi-photon absorption in the transparent material, when laser is focused on the interface of two pieces of glass, the material at the focus is melted and permeated, and the two pieces of glass can be welded together after cooling. Meanwhile, the distance between the two pieces of glass is reduced after welding and is smaller than the coherence length of white light, so that obvious white light interference fringes can be observed. The welding seam of the ultrafast laser welding has the advantages of tight connection, good sealing performance, simple processing process, no deformation and the like.

In recent years, ultrafast laser welding technology has received increasing attention from researchers. At present, many researchers adopt a microscope objective to focus and carry out wire welding and spot welding, which has good effects, but the method also has some inevitable defects:

(1) because the adopted microscope objective has a small focus and has high requirements on the precision of focus alignment, the two surfaces are required to be in optical contact, and the microscope objective is usually fixed by a clamp and hardly meets the requirements in actual production;

(2) when the microscope objective is adopted for welding, the displacement platform is adopted for moving, and due to the limitation of the displacement platform, the welding speed is low, the efficiency is low, and the microscope objective is not suitable for production and application;

(3) the focal length of the objective lens is small, the thickness of a welding material is greatly limited, a thicker material cannot be welded, and the application range of laser welding is greatly limited.

In order to solve the above problems, French researchers have solved the problems of alignment accuracy and welding speed by using galvanometers instead of microscope objective welding (Applied Optics 2019,58(32):8858 + 8864). The method adopts a vibrating mirror to replace a microscope objective, and when the repetition frequency is increased to 2MHz, the welding speed of 1000mm/s is achieved, but the gap between the welding glass is only 3 mu m, and the welding strength is only 30 MPa.

Researchers have also implemented welding of naturally stacked large gap glasses (gap about 10 μm) by using galvanometer fast oscillatory scanning (1, Optics Express,2019,27(21): 30297-. The method adopts the scanning galvanometer and the focusing field lens with long focal length to carry out rapid oscillation scanning, greatly improves the welding speed and obtains high welding quality. However, the above method still has the following problems in large area welding: the welding point that the oscillation scanning formed is discontinuous, and in order to reach sealed needs additionally to carry out continuous welding, the whole area that occupies of welding is great, is difficult to accomplish the welding when the weldable area is very limited.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a device and a method for femtosecond laser welding glass, which realize firm welding of glass with larger gaps by a two-step welding mode of primarily welding by utilizing higher single-pulse energy laser, creating a semitransparent welding seam and finally welding by utilizing lower single-pulse energy laser, and have the advantages of simple process, stable and reliable flow and wide applicable range. The welding gap of the method can reach 5-10 mu m usually, the shearing strength is more than 40MPa, the sealing effect can be achieved by only generating one welding line in the whole process, the occupied area is small, and the method is favorable for welding devices with limited welding area.

In order to achieve the above object, the technical solution of the present invention is as follows:

an apparatus for femtosecond laser welding glass, comprising: the laser device comprises a laser used for emitting ultrafast laser pulses, a beam expanding collimating lens used for expanding and collimating laser beams, a first reflecting mirror and a second reflecting mirror used for finely adjusting the laser beams so that the laser beams vertically enter a field lens, a vibrating mirror used for controlling a scanning path and focusing the laser beams, and a displacement platform used for adjusting the position of glass so that the laser focus is positioned in a glass gap.

The reflector is not limited to the first reflector and the second reflector, and the reflector can be added or the angle of the reflector can be adjusted according to the requirement, so that the optical path can be adjusted, and the practical application is facilitated.

And the output port of the galvanometer is provided with a focusing field lens.

The method for welding the glass by using the device for welding the glass by the femtosecond laser comprises the following steps:

1) dripping a small amount of liquid on one piece of glass, then stacking the other piece of glass to fill the liquid in the gap between the two pieces of glass to be welded, compressing the two pieces of glass to discharge air, and reducing the gap between the two pieces of glass by utilizing the action of atmospheric pressure, thereby reducing the welding difficulty;

2) focusing a laser beam on the contact surface of two pieces of glass to be welded, selecting high single pulse energy and utilizing a scanning galvanometer to scan the laser focus at a high speed along a closed path, wherein the scanning speed is higher than 100 mm/s;

3) repeating the path in the step 2) by using lower single pulse energy and scanning at low speed, wherein the scanning speed is lower than 50mm/s, the semi-transparent welding seam is used for enhancing laser absorption, the volume of a molten pool is enlarged, and the molten material is cooled to form a welding seam with larger scale, so that the sealing welding of the large-gap glass is realized.

The two glass materials can be the same or different, and specific parameters can be adjusted after the glass materials are changed, but the welding method is not changed.

The gap between the two glass materials is larger than 3 μm, and is usually 5-10 μm.

The liquid is ethanol or water.

The shape of the closed path adopted for achieving the sealing requirement is not unique, and can be a regular closed shape or an irregular closed shape of a circle, a rectangle or a polygon.

The number and the width of the sealing welding seams can be adjusted according to the requirement of welding strength; the method specifically comprises the following steps: (1) the more the number of welding lines is, the greater the total welding strength is; (2) the wider the overall weld, the greater the overall weld strength.

Compared with the prior art, the invention mainly has the following advantages:

1. the galvanometer is adopted to replace a microscope objective to weld two pieces of glass, the scanning speed of the galvanometer is far higher than that of a displacement platform when the microscope objective is adopted, and the welding speed is greatly accelerated.

2. The requirements of the galvanometer welding focusing point positioning precision and the glass surface are greatly reduced, the glass surface is only required to be cleaned, a liquid adding method is adopted, the atmospheric pressure is utilized, the gap between two pieces of glass before welding is reduced, the glass can be welded without clamping of a clamp, and the machining efficiency is greatly improved again.

3. The semitransparent welding seam formed by the first welding can form initial welding, fix the relative positions of two pieces of glass and create a high-absorption area for final welding.

4. The speed is faster when higher single pulse energy high speed scanning, and the glass clearance is evenly reduced gradually, can guarantee that glass does not warp.

5. Subsequent scans with lower single pulse energies may reduce the generation of microcracks.

6. And the galvanometer scanning welding is adopted, so that the welding speed is high, the requirement on the surface of the glass is low, the efficiency is improved, and the cost is reduced.

7. The invention adopts continuous welding, does not need to stay for a long time in a local area, reduces the generation of microcracks and shortens the processing time.

8. Only one welding line is generated, the occupied area is small, and the welding of a small-area device is facilitated.

For example, the total welding area in the embodiment of the invention is 35mm²During welding, the time required by two-step welding is only a few minutes, and the femtosecond laser with higher power and repetition frequency can be further adopted to greatly shorten the welding time in practical application.

Drawings

FIG. 1 is a welding apparatus used in an embodiment of the present invention

FIGS. 2 and 3 are paths taken by embodiments of the present invention

In the figure: 1. a laser; 2. a laser beam; 3. a beam expanding collimating lens; 4. a second laser beam; 5. a first reflector; 6. a second reflector; 7. a galvanometer; 8. a field lens; 9. focusing the laser beam; 10. an upper layer of glass; 11. a lower layer of glass; 12. a welding path; 13. displacement platform

Detailed Description

When the welding device works, a laser beam 2 emitted by a laser 1 is expanded and collimated by an expanding collimator lens 3, then is reflected to a vibrating mirror 7 by a first reflecting mirror 5 and a second reflecting mirror 6, and then is focused to the contact surface of two glass materials to be welded by a field lens 8 to be welded according to a path 12. In addition, the lifting of the materials to be welded is realized through the displacement platform 13, so that the laser is focused on the contact surface of the two pieces of glass. The beam expanding collimating lens 3 is used for expanding and collimating the laser beam 2 output by the laser 1, and the first reflecting mirror 5 and the second reflecting mirror 6 are used for guiding the expanded and collimated second laser beam 4 into the vibrating mirror 7 and then focusing the second laser beam through the field lens 8 to form a focused laser beam 9.

The following are examples of the present invention:

example 1

And welding two pieces of quartz glass dropwise added with absolute ethyl alcohol and stacked and having the thickness of 0.5-3mm by using a femtosecond laser with the output wavelength of 1030nm, the pulse width of 450fs, the output maximum power of 10W and the repetition frequency of 100-300KHz, wherein the gap between the two pieces of quartz glass is 5-10 mu m. Focusing femtosecond laser on the contact surface between two pieces of glass, setting the laser power of the target surface to 4-6W, the pulse repetition frequency to 100-200KHz, and scanning concentric circle path with the scanning distance of 0.01-0.05mm at the speed of 100-300mm/s as shown in FIG. 2; then the laser power of the target surface is changed to 6-8W, the pulse repetition frequency is 200-300KHz, and the target surface is scanned along the same path at the speed of 7-30 mm/s. The welding results show that: the glass is uniformly melted at the welding seam, the waterproof sealing performance is good, the shearing strength is greater than 40MPa, and no trace is damaged on the surface of the glass.

Example 2

On the basis of the above example 1, further, water was dropped in the glass gap instead of absolute ethyl alcohol, and the welding result showed that: the glass is uniformly melted at the welding seam, the waterproof sealing performance is good, and no trace is damaged on the surface of the glass.

Example 3

On the basis of the above embodiment 1, further, by adopting the concentric round rectangular path of fig. 3 instead of the concentric circular path of fig. 2, the welding result shows that: the glass is uniformly melted at the welding seam, the waterproof sealing performance is good, and no trace is damaged on the surface of the glass.

It should be noted that the above embodiments are intended to facilitate understanding of the technical solutions of the present invention, and are not intended to limit the same; any modifications, equivalents, improvements and the like of the present invention are within the scope of the present invention.

Claims

1. a device for femtosecond laser welding glass, is characterized in that, comprises: the laser that is used for transmitting ultrafast laser pulse, is used for the beam expanding collimator that laser beam is carried out beam expanding collimation, is used for fine-tuning laser beam The first and second mirrors that make the laser beam enter the field mirror vertically, the galvanometer used to control the scanning path and focus the laser beam, and the displacement platform used to adjust the glass position so that the laser focus is in the glass gap.

2. The device for welding glass by femtosecond laser according to claim 1, wherein the reflecting mirror is not limited to the first reflecting mirror and the second reflecting mirror, the reflecting mirror can be added or the angle of the reflecting mirror can be adjusted as required, Adjust the optical path for practical application.

3 . The femtosecond laser welding glass device according to claim 1 , wherein the output port of the galvanometer mirror is provided with a focusing field lens. 4 .

4. the glass welding method of utilizing the femtosecond laser welding glass device of claim 1, is characterized in that, comprises the steps:

1) Drop a small amount of liquid on one piece of glass, and then stack another piece of glass, so that the liquid fills the gap between the two pieces of glass to be welded, press the two pieces of glass to discharge the air, and use the action of atmospheric pressure to reduce the glass gap. Reduce welding difficulty;

2) Focus the laser beam on the contact surface of the two pieces of glass to be welded, select a higher single-pulse energy and use a scanning galvanometer to scan the laser focus along a closed path at high speed, and the scanning speed is higher than 100mm/s;

3) Repeat the path in step 2) with a lower single-pulse energy and scan at a low speed, the scanning speed is lower than 50mm/s, use the translucent weld to enhance the laser absorption, expand the molten pool volume, and the molten material cools to form a larger Large-scale welding seam to achieve sealing welding of large gap glass.

5 . The method for welding glass by femtosecond laser according to claim 4 , wherein the two glass materials can be the same or different, and the specific parameters also need to be adjusted after changing the glass materials, but the welding method remains unchanged. 6 .

6 . The method for welding glass by femtosecond laser according to claim 4 , wherein the gap between the two glass materials is greater than 3 μm, usually 5-10 μm. 7 .

7 . The method for welding glass by femtosecond laser according to claim 1 , wherein the liquid is ethanol or water. 8 .

8 . The method for welding glass by femtosecond laser according to claim 4 , wherein the shape of the closed path adopted to meet the sealing requirements is not unique, and can be a regular closed shape of a circle, a rectangle, a polygon, or an irregular shape. 9 . closed shape.

9 . The method for welding glass by femtosecond laser according to claim 4 , wherein the number and width of the sealing seam can be adjusted according to the requirements of welding strength; specifically, the method includes: (1) the more the number of welding seams , the greater the total welding strength; (2) the wider the overall weld, the greater the total welding strength.