CN108723595A - A kind of ultrafast laser welder and method - Google Patents

Abstract

The invention provides an ultrafast laser welding device and method, belonging to the technical field of laser welding processing. It solves technical problems such as low welding strength and service durability of welding samples in the existing welding method. The ultrafast laser welding method comprises the following steps: S01, pretreatment: performing optical contact treatment on the sample to be welded, so that the glass sheet and the silicon sheet are closely bonded; S02, adjusting the laser beam: using an ultrafast laser to generate an ultrafast laser beam, and Adjust the wavelength band, output power and repetition frequency of the ultrafast laser beam; S03, processing: the laser beam emitted by the ultrafast laser passes through the optical transmission system and the galvanometer scanning system, and is focused on the space between the glass sheet and the silicon sheet on the workbench. After contacting the surface, adjust the focus position through the workbench, and weld the sample to be welded. The ultra-fast laser welding method can improve the welding strength and durability of the samples to be welded, and avoid the pollution of the samples to be welded by adding solder or adhesive.

Description

An ultrafast laser welding device and method

technical field

The invention belongs to the technical field of laser welding processing, and relates to an ultrafast laser welding device and method.

Background technique

The bonding of glass and silicon wafers can be used to package electronic chips and process biochips, and has a wide range of applications in life sciences, electronic sciences, aerospace and other fields. In traditional bonding techniques, expensive and some toxic adhesives are used, or solder or coatings are added between heated molten materials using a laser welding process.

The adhesive or solder used in the above method has low durability, is easy to age, and will cause pollution to glass and silicon wafers, which cannot meet the cleanliness requirements for chip packaging and use. In particular, the use of biochips should strictly avoid secondary pollution of the liquid to be tested.

Therefore, it is necessary to introduce an ultrafast laser welding device and process capable of achieving high durability and no pollution to glass and silicon wafers.

Contents of the invention

The present invention aims at the above-mentioned problems existing in the existing technology, and provides an ultrafast laser welding device, which can improve the welding strength and durability of the samples to be welded, and avoid the pollution of the samples to be welded by adding solder or adhesive.

The purpose of the present invention can be achieved through the following technical solutions:

An ultrafast laser welding device is characterized in that it includes an ultrafast laser, an optical transmission system, a galvanometer scanning system, a workbench and a welding fixture for fixing samples to be welded, and the optical transmission system is used to The laser beam emitted by the laser is transmitted to the galvanometer scanning system, the worktable is located below the galvanometer scanning system, and the welding fixture is fixed on the worktable.

Its working principle is: the welding fixture is used to fix the samples to be welded (glass sheet and silicon sheet), the optical transmission system is used to transmit the laser beam emitted by the laser into the galvanometer scanning system, and the galvanometer scanning system focuses the laser beam and controls the laser beam. Beam scanning trajectory to form a focused spot between the glass and silicon wafers to be welded, where the laser is used to control the wavelength band, output power and repetition frequency of the laser beam, the optical transmission system is used to control the quality and loss of the laser beam, and the vibration The mirror scanning system controls the processing method and scanning speed, combined with the galvanometer scanning system and the worktable to perform three-axis rotation control, adjusts the x, y, and z axes, and controls the focus position of the laser beam in the sample to be welded. Through the control of the above system, the process parameters such as laser beam band, output power, repetition frequency, processing method, speed and defocus amount can be adjusted to obtain suitable processing parameters and weld the samples to be welded. The invention uses an ultrafast laser to directly weld glass and silicon wafers, avoiding the pollution of the sample to be welded by adding solder or adhesive, avoiding the secondary pollution caused by the use process, and utilizing the nonlinear absorption effect of the ultrafast laser to realize cold processing , There is a very small residual stress and temperature field gradient distribution around the weld to avoid damage to the electronic components to be packaged, to achieve high-precision processing, to improve the welding strength and durability, and to bring a better lap welding effect.

In the above-mentioned ultrafast laser welding device, the welding fixture includes a body, and the body is provided with an accommodating chamber for placing samples to be welded, and a number of bolts are threaded on the top wall of the accommodating chamber, and each bolt All the screws can extend into the accommodating cavity. When in use, the samples to be welded (glass sheet and silicon sheet) are superimposed and placed together in the container, and then each bolt is rotated. When the screw of each bolt is against the glass sheet, the bolts press the two samples to be welded. Tight and make the two close to each other, so that the gap between the two can be reduced as much as possible and the welding strength can be improved.

Another object of the present invention is to provide an ultrafast laser welding method.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of ultrafast laser welding method, is characterized in that, comprises the steps:

S01. Pretreatment: Perform optical contact treatment on the sample to be welded, so that the glass sheet and the silicon sheet are closely bonded, and the air on the contact surface between the glass sheet and the silicon sheet is eliminated, so that the contact surface between the glass sheet and the silicon sheet has no interference stripe;

S02. Adjusting the laser beam: using an ultrafast laser to generate a laser beam, and adjusting the wavelength band, output power and repetition rate of the laser beam;

S03. Processing: The laser beam emitted by the ultrafast laser passes through the optical transmission system and the galvanometer scanning system, and is focused on the contact surface between the glass sheet and the silicon wafer on the workbench. The wave band, output power and repetition frequency of the beam are adjusted by the galvanometer scanning system to weld the samples to be welded.

In the above-mentioned ultrafast laser welding method, the samples to be welded are glass sheets and silicon sheets, the glass sheets are soda lime silicate glass sheets, and the thickness of the glass sheets is 0.3mm-1.5mm. The thickness of the silicon wafer is 0.7mm-2.0mm.

As another example, the glass sheet may also be tempered glass doped with rare elements, low-alkali borosilicate glass, or rare earth-doped borosilicate glass.

In the above-mentioned ultra-fast laser welding method, the optical contact treatment includes the following steps: cleaning, drying and squeezing, the cleaning is to use an ultrasonic cleaner to clean the sample to be welded for 5-10 minutes, and the drying In order to directly blow dry with nitrogen, the extrusion is 20-30 minutes for the extrusion of the sample to be welded.

Before the step S02, the pretreatment is an optical contact treatment, and the specific implementation steps are: cleaning, drying and squeezing the glass and silicon wafers to be welded. The cleaning step is specifically to use an ultrasonic cleaner to clean for 5-10 minutes, the blow-drying step is to use nitrogen gas to blow dry directly, and the extrusion step is to extrude the sample to be welded (glass and silicon wafer) for 20-30 minutes, so that the gap between the two If there is no interference fringe when observing the contact surface between the two through the glass sheet, the pretreatment of the sample to be welded meets the welding requirements, and welding fixtures can be used during processing to ensure the tightness between the two. fit.

In the above-mentioned ultrafast laser welding method, the power of the ultrafast laser is 5-50W, the wavelength of the laser beam emitted by the ultrafast laser is 515nm-1064nm, the pulse width is 15ps-300fs, and the repetition frequency is 90kHz- 1MHz.

In the above-mentioned ultrafast laser welding method, the galvanometer scanning system adopts the method of focusing light spots to move slowly in a line array, and the line speed of the galvanometer scanning system is 0.1mm/s-20mm/s.

Compared with prior art, advantage of the present invention is as follows:

1. The present invention uses an ultrafast laser to directly weld glass and silicon wafers, avoiding the pollution of the sample to be welded by adding solder or adhesive, avoiding the secondary pollution caused by the use process, and adopting the method of ultrafast laser welding, which is reasonably controlled The processing parameters of the laser pulse can obtain a deeper molten pool, and at the same time, according to the requirements of different application fields for welding strength and weld width, the appropriate processing parameters can be adjusted to realize the setting of personalized process parameters.

2. Utilize the nonlinear absorption effect of ultrafast laser to realize cold processing, produce extremely small residual stress and temperature field gradient distribution around the weld seam, avoid damage to the electronic components to be packaged, realize high-precision processing, and improve welding strength and The use of durability can bring better stitch welding effect, and at the same time, it does not require expensive adhesives, which improves economic benefits, and does not require the use of polluting cleaning fluids and activation fluids, which simplifies the processing process and improves processing efficiency. Meet environmental protection requirements.

Description of drawings

Figure 1 is a block diagram of the working principle of the ultrafast laser welding device.

Figure 2 is a schematic diagram of a glass sheet stacked on a silicon sheet.

Fig. 3 is a flowchart of the welding method.

Fig. 4 is a structural schematic diagram of a welding fixture.

In the figure, 1. Ultrafast laser; 2. Optical transmission system; 3. Galvanometer scanning system; 4. Welding fixture; 5. Workbench; 6. Bolt; 7. Glass sheet; 8. Silicon sheet; 9. Laser beam .

Detailed ways

The following are specific embodiments of the present invention and in conjunction with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

As shown in Figure 1, the ultrafast laser welding device includes an ultrafast laser 1, an optical transmission system 2, a galvanometer scanning system 3, a workbench 5 and a welding fixture 4 for fixing samples to be welded, and the optical transmission system 2 is used The laser beam 9 emitted by the ultrafast laser 1 is transmitted to the galvanometer scanning system 3 , the worktable 5 is located below the galvanometer scanning system 3 , and the welding fixture 4 is fixed on the worktable 5 . The ultrafast laser 1 is located on one side of the optical transmission system 2 , the galvanometer scanning system 3 is located behind the optical transmission system 2 , and the welding fixture 4 is arranged on the workbench 5 and below the galvanometer scanning system 3 . The optical transmission system 2 is used to transmit the laser beam 9, and can optimize the beam quality. The optical transmission system 2 includes a reflector, a perspective mirror and a beam expander; The size of the focused spot can be adjusted by exchanging lenses with different focal lengths, and the position of the laser beam 9 in the z-axis direction can be controlled by controlling the position of the galvanometer scanning system 3 in the vertical direction.

As shown in Figure 2, the glass sheet 7 and the silicon sheet 8 to be welded in the present invention are welded by lap welding, the glass sheet 7 is on top, the bright surface of the silicon sheet 8 is in contact with the glass, and the silicon sheet 8 is below, and the two are stacked. Place in the welding fixture 4 after putting extrusion.

First, the laser beam 9 is emitted by the ultrafast laser 1, and the emitted laser beam 9 is incident on the galvanometer scanning system 3 after passing through the optical transmission system 2, and the laser beam 9 is focused through the galvanometer scanning system 3, so that the laser beam 9 is A focused light spot is formed at the interface of the sample to be welded fixed on the fixture 4, and the sample to be welded is welded by using the focused light spot.

During the laser welding process, the laser beam 9 with high energy density is focused on the interface of the sample to be welded. Since the Raman spectrum peak of silicon is 520nm, it has a strong absorption rate for the ultrafast laser, and the ultrafast The laser has a very high peak power. Different from the laser in the nanometer band, the ultrafast laser can easily reach the absorption threshold of the material when it acts on the material, and then generate a nonlinear absorption effect to produce photoionization and avalanche ionization. A teardrop-shaped melting zone appears inside the material, realizing the welding of the glass and the silicon wafer 8 . However, since the semiconductor material silicon has a large refractive index, the amplitude of the wave in the semiconductor material decreases with the depth of penetration, that is, there is light absorption. Due to the existence of free electrons in the conductive medium, the light wave excites the conduction current in the medium during the propagation process, and part of the energy of the light wave is converted into the Joule heat of the current. Therefore, observe the microscopic morphology of glass and silicon wafer 8 welding seams by confocal microscope, and find that the complete teardrop-shaped structure that can be presented inside the glass (the morphology of the focused light spot inside the reaction material), is in the glass and The soldered area of the silicon wafer 8 only presents the upper half of the teardrop-shaped structure inside the glass.

By adjusting the galvanometer scanning system 3 to adjust the welding process parameters, the optimal welding effect can be achieved. The process parameters include the frequency of the laser beam 9, the power of the laser beam 9, the line speed of the galvanometer scanning system 3, and the switching optical delay. time and focus position, etc.

As shown in Figure 4, the welding fixture 4 includes a body, which is provided with an accommodation chamber for placing samples to be welded, and a number of bolts 6 are threaded on the top wall of the accommodation chamber, and the screw rods of each bolt 6 can extend into the accommodation chamber . During use, the samples to be welded (glass sheet 7 and silicon sheet 8) are stacked together and put into the container together, and then each bolt 6 is rotated. Compress the sample to be welded and make the two close to each other, so that the gap between the two can be reduced as much as possible and the welding strength can be improved.

As shown in Figure 3, the ultrafast laser welding method includes the following steps:

S01, pretreatment: carry out optical contact treatment on the sample to be welded, make the glass sheet 7 and the silicon sheet 8 fit closely, eliminate the air on the contact surface between the glass sheet 7 and the silicon sheet 8, and make the contact surface between the glass sheet 7 and the silicon sheet 8 There is no interference fringe on the contact surface between them;

S02. Adjusting the laser beam: using the ultrafast laser 1 to generate the laser beam 9, and adjusting the wavelength band, output power and repetition frequency of the laser beam 9;

S03, processing: the laser beam 9 emitted by the ultrafast laser 1 passes through the optical transmission system 2 and the galvanometer scanning system 3, and after focusing on the contact surface between the glass sheet 7 and the silicon sheet 8 on the workbench 5, passes through the working The stage 5 adjusts the focus position, combines the wavelength band, output power and repetition frequency of the laser beam 9, adjusts the scanning speed through the galvanometer scanning system 3, and performs welding on the sample to be welded.

Among them, S01 pretreatment: optical contact treatment, the specific implementation process is: take ordinary soda-lime silicate glass and ordinary single crystal silicon wafer 8, clean them with an ultrasonic cleaner for 10 minutes, dry them with nitrogen gas, and then squeeze them tightly. Weld the sample for 20-30 minutes, and observe the contact surface of the glass sheet 7 and the silicon sheet 8 through the glass sheet 7. If there is no interference fringe on the contact surface between the two, the welding requirements are met, and the sample can be loaded into the welding fixture 4 for preparation. welding.

This embodiment is also applicable to other types or thicknesses to be welded, for example, the glass sheet 7 is low-alkali borosilicate glass, rare earth doped borosilicate glass, and the like.

S02 Adjusting the beam: the maximum average power of the ultrafast laser 1 is 50W, the output wavelength range is 515-1064nm, the pulse width is 15ps-300fs, and the repetition frequency is 90kHz-1000kHz.

By adjusting the distance between the focusing lens of the galvanometer scanning system 3 and the processing platform, laser focusing can be achieved at the junction of the samples to be welded, and the focus position can be flexibly changed. Because the upper layer of the sample is transparent glass, it is ideal to focus the smallest light spot at the junction of the two.

S03 processing: use the laser beam 9 emitted by the ultrafast laser 1 to pass through the galvanometer scanning system 3, and adopt a slow-tracking processing method for welding, and the scanning speed can be adjusted.

In this embodiment, welding can be realized at a wire speed of the focused spot in the range of 0.1 mm/s-20 mm/s.

The relevant analysis and conclusions obtained after the glass sheet 7 and the silicon sheet 8 welding process of the present embodiment are as follows:

1) Through analysis, it is found that the absorption peak of the Raman spectrum of the silicon material is 520nm, and the laser in this band acts on the silicon wafer 8 to generate a strong temperature field, which makes the silicon material appear in a molten state more easily, and can produce less Dust and slag, while the glass material will undergo nonlinear absorption effect under the action of ultrafast laser, resulting in photoionization, melting and solidification. And considering that in the use of finished products, in order to avoid the introduction of secondary pollutants, more dust and slag should be avoided during the laser welding process, and the base metal around the weld seam should be affected by the heat effect produced by the laser. The range is as small as possible. The laser beam 9 emitted by the ultrafast laser 1 is used in the welding process of glass and silicon wafers 8, all of which can meet these requirements, and the processing process is simple, high in precision, high in efficiency, and pollution-free. It will not cause damage and has great application value.

After a series of tests, it was found that: 515nm-1064nm band, 5w-50w power, 15ps-300fs pulse width laser has a better welding effect on glass and silicon wafer 8, and the best welding effect can be obtained by adjusting the process parameters.

2) In the laser welding process, within the effective processing speed range, the processing speed is inversely proportional to the temperature inside the material, and the depth of the molten pool is proportional to the temperature inside the material, so the processing speed and the weld pool of the material Depth is inversely proportional. The processing speed has a certain influence on the width of the weld and the distribution density of the molten material, which indirectly affects the mechanical properties of the weld. Therefore, according to the different requirements of different processing application fields for the width of the weld and the mechanical properties, the appropriate processing speed can be selected, and the wave band, power, repetition frequency and defocus of the laser beam 9 can be adjusted at the same time to realize the individualization of processing parameters. custom made.

In order to obtain a better welding effect, the processing method of the galvanometer scanning system 3 and the slow line array are adopted, and the high repetition frequency and peak power of the ultra-fast laser 1 are fully utilized to achieve a better welding effect and better welding strength and tightness. Through testing, it is found that when the line speed of the galvanometer scanning system 3 is 0.1mm/s-20mm/s, the welding effect is the best.

The present invention realizes the direct welding of the glass sheet 7 and the silicon sheet 8 without adding solder through the ultrafast pulse laser, compared with the traditional bonding process of the glass and the silicon sheet 8, the cost saving is realized, and the coating and solder are avoided. The pollution of the material avoids the secondary pollution of the solder or adhesive during the use of the finished product. In the pretreatment process, only optical contact treatment is required. Compared with the existing silicon/glass laser partial bonding method, the entire processing process is simplified, the processing efficiency is improved, and no polluting cleaning solution and activation solution are used. Avoid pollution and damage to the electronic components to be packaged, and meet the requirements of environmental protection.

Using the processing method of galvanometer scanning system 3 slow line array, controlling the pulse delay time, so that the area of the material affected by the laser can obtain local high temperature, obtain a deeper molten pool, and strengthen the welding strength of the material, so as to achieve better glass Overlap welding effect with silicon wafer 8, and ultra-fast laser can realize cold processing, produce small residual stress and temperature field gradient distribution around the weld seam, and avoid damage to electronic components to be packaged. Different welding strengths and weld widths can be obtained by adjusting process parameters such as laser band, output power, repetition frequency, scanning speed, and focus position, and realize personalized process parameter design for different application requirements in different application fields.

The pretreatment steps adopted in the embodiment of the present invention include washing, drying and pressing, and the air between the glass and the silicon can be eliminated as much as possible through the washing, drying and pressing.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (7)

1. an ultrafast laser welding device, is characterized in that, comprises ultrafast laser (1), optical transmission system (2), vibrating mirror scanning system (3), workbench (5) and is used for fixing sample to be welded The welding fixture (4), the optical transmission system (2) is used to transmit the laser beam (9) emitted by the laser to the galvanometer scanning system (3), and the worktable (5) is located on the Below the vibrating mirror scanning system (3), the welding fixture (4) is fixed on the workbench (5). 2. A kind of ultrafast laser welding device according to claim 1, characterized in that, the welding fixture (4) comprises a body, and the body is provided with an accommodating cavity for placing samples to be welded, and the accommodating cavity A number of bolts (6) are threaded on the top wall of the top wall, and the screw rods of each bolt (6) can extend into the accommodating cavity. 3. an ultrafast laser welding method adopting the ultrafast laser welding device described in any one of claims 1-2, is characterized in that, comprises the steps: S01, pretreatment: optical contact treatment is carried out for the sample to be welded, so that the glass sheet (7) and the silicon sheet (8) are closely bonded, and the air on the contact surface between the glass sheet (7) and the silicon sheet (8) is eliminated, so that the There are no interference fringes on the contact surface between the glass sheet (7) and the silicon sheet (8); S02. Adjusting the laser beam (9): using an ultrafast laser (1) to generate an ultrafast laser beam (9), and adjusting the band, output power and repetition rate of the ultrafast laser beam (9); S03, processing: the laser beam (9) emitted by the ultrafast laser (1) passes through the optical transmission system (2), the galvanometer scanning system (3), and focuses on the glass sheet (7) and silicon on the workbench (5). After the contact surface between the sheets (8), the focus position is adjusted through the workbench (5), and the scanning speed is adjusted through the galvanometer scanning system (3) in combination with the wavelength band, output power and repetition frequency of the laser beam (9). welding samples. 4. ultrafast laser welding method according to claim 3, is characterized in that, described sample to be welded is glass sheet (7) and silicon sheet (8), and described glass sheet (7) is soda calcium silicate A glass sheet (7), the thickness of the glass sheet (7) is 0.3mm-1.5mm, and the thickness of the silicon sheet (8) is 0.7mm-2.0mm. 5. The ultrafast laser welding method according to claim 3, wherein the optical contact process comprises the steps of: cleaning, drying and extruding, and the cleaning is to use an ultrasonic cleaner to clean the sample to be welded for 5- 10 minutes, the blow-drying is direct blow-drying with nitrogen, and the extrusion is 20-30 minutes for the extruded product to be welded. 6. ultrafast laser welding method according to claim 3, is characterized in that, the power of described ultrafast laser (1) is 5-50W, and the wavelength of the laser beam (9) that ultrafast laser (1) emits is 515nm-1064nm, pulse width 15ps-300fs, repetition frequency 90kHz-1MHz. 7. The ultra-fast laser welding method according to claim 3, characterized in that, the galvanometer scanning system (3) processes in the manner of focusing light spots in a slow alignment array, and the alignment of the galvanometer scanning system (3) The speed is 0.1mm/s-20mm/s.