A solder distribution control method for metal-glass laser brazing process

Abstract

The application discloses a solder distribution control method for a metal-glass laser brazing process, which comprises the following steps: step one, material preparation: the glass and metal substrate to be welded are cleaned, dried and surface oil stains are removed; step two, a groove array is processed in the processing area on the surface of the metal substrate by a laser to form a regular quadrangular prism microstructure array; step three, paste solder is laid on the surface of the metal substrate, and the glass treated in step one is arranged on the paste solder, so that the paste solder fills the gap between the glass and the metal substrate to be welded; step four, continuous laser irradiation on the paste solder through the glass makes the solder melt and flow to fill the gap between the glass and the metal substrate; when the continuous laser moves away, the molten solder solidifies again to form a compact solder metal layer filled in the gap between the glass and the metal substrate; the application realizes the enhancement of the solder aggregation and the control of the solder distribution, and improves the welding effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ultrafast laser microstructure processing, and particularly relates to a filler metal distribution control method for a metal-glass laser brazing process. BACKGROUND

[0002] Glass is an optical functional material, commonly used as an optical window, or a lens, prism, mirror, etc. that plays a role in imaging. Glass is a typical hard and brittle material, with low ductility, not impact-resistant, difficult to process, and other mechanical performance limitations, so in many cases, glass and metal base need to be connected together to improve the overall mechanical performance, which is widely used in optical, communication, electronic, aerospace, automotive manufacturing, biomedical and other high-tech fields.

[0003] At present, the commonly used methods to realize the connection of glass and metal are mechanical connection and adhesive connection. Among them, mechanical connection requires additional connection interface design and precise manufacturing to ensure assembly accuracy; adhesive is convenient to use, but it is easy to age, creep and leak, and it is difficult to meet the complex working environment. In order to realize the permanent and high-quality connection of glass and metal, ultrafast laser is a very effective means. Ultrafast laser has extremely narrow pulse width and extremely high peak power, which can induce multi-photon ionization and avalanche ionization processes of glass material, realize effective absorption of laser energy by glass, and through the thermal accumulation effect of high repetition rate ultrafast laser, the glass is melted to realize the welding of glass and metal. However, there are still some limitations in the ultrafast laser welding of glass and metal. Because the heating area of ultrafast laser is very small, it requires the glass and metal to be welded to be closely attached without gaps, which reduces the application range of ultrafast laser welding, so a large gap connection technology suitable for various glasses and metals is needed, and brazing can meet this demand. Unlike conventional brazing scenarios, glass and metal brazing often has only tens to hundreds of microns of gap, poor parallelism between the welding surfaces, and the filler metal cannot be effectively combined with the glass. During laser brazing, due to the volume change of the filler metal after melting and the driving effect of laser heating, the distribution of the filler metal after solidification is very random, usually showing dot matrix distribution or strip distribution, and part of the molten filler metal will separate from the welding target area, causing poor filler metal distribution, low welding strength and other problems.

[0004] In order to obtain good filler metal distribution under small gap to improve the welding quality, a simple and effective filler metal distribution control method is needed. SUMMARY

[0005] The application aims to provide a filler distribution control method for a metal-glass laser brazing process.

[0006] The application can be achieved by the following technical solutions.

[0007] A filler distribution control method for a metal-glass laser brazing process, comprising the following steps:

[0008] Step 1: material preparation: clean, dry and remove surface grease from the glass and metal substrates to be welded;

[0009] Step 2: process a groove array in the processing area on the surface of the metal substrate by a laser to form a regular quadrangular prism microstructure array;

[0010] Step 3: spread the paste filler on the surface of the metal substrate, and place the glass treated in step 1 on the paste filler to fill the gap between the glass and the metal substrate to be welded;

[0011] Step 4: continuously irradiate the paste filler with a laser through the glass to melt and flow the filler to fill the gap between the glass and the metal substrate;

[0012] When the continuous laser is removed, the melted filler solidifies to form a compact filler metal layer filling the gap between the glass and the metal substrate.

[0013] As a further scheme of the application, the cleaning method for the glass and the metal substrate in step 1 includes ultrasonic cleaning, alcohol cleaning or acetone solvent cleaning.

[0014] As a further scheme of the application, in step 2, before processing the groove array in the processing area, a superfast laser scanning pattern is designed on the surface of the metal substrate to form a laser scanning area, i.e., the processing area.

[0015] As a further scheme of the application, the superfast laser scanning pattern includes a circular ring and a checkered pattern.

[0016] As a further scheme of the application, the area on the surface of the metal substrate without the superfast laser scanning pattern is the filler distribution area.

[0017] As a further scheme of the application, the paste filler is SnAg0.3Cu0.7 solder paste.

[0018] As a further scheme of the present application: in step three, the laser is a picosecond laser, the laser pulse width of the picosecond laser is 8 ps, the wavelength is 1030 nm, the laser output average power is 2.5 W, the scanning speed is 250 mm / s, the scanning line spacing is 50 microns, and the repeated scanning number is 50 times.

[0019] As a further scheme of the present application: in step three, during the positioning of the glass and the metal substrate, the relative pose of the glass and the metal substrate is determined by the clamping positioning mechanism.

[0020] As a further scheme of the present application: in step four, the continuous laser is a pulse laser.

[0021] As a further scheme of the present application: in step four, when the gap between the glass and the metal substrate exceeds 10 microns, the laser changes from a fixed point to a scanning, so that the solder can be heated and melted.

[0022] The beneficial effects of the present application: the present application changes the surface roughness of solid metal by constructing a unique microstructure array on the metal surface with ultrafast laser, so that the true surface area is greater than the apparent surface area, thereby changing the wettability of the material itself;

[0023] On the other hand, air is filled between the rough structure and the droplet, forming a trapped air cushion under the droplet, so that the droplet is placed at the top of the rough structure, reducing the contact area with the material surface. Therefore, the microstructure array surface constructed by using ultrafast laser under certain processing parameters has good liquid-repellent properties. By designing a specified processing pattern, the solder will automatically separate from the liquid-repellent area after melting and gather in the unprocessed area, thereby realizing the control of solder distribution and good filling of the gap between glass and metal, and further improving the overall welding strength and welding quality. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further described below with reference to the accompanying drawings.

[0025] Figure 1 is a structural schematic diagram of the present application square lattice ultrafast laser scanning pattern;

[0026] Figure 2 is a structural schematic diagram of the present application square lattice ultrafast laser scanning pattern;

[0027] Figure 3 is a structural schematic diagram of the present application square lattice ultrafast laser scanning pattern;

[0028] Figure 4 is a structural schematic diagram of the present application square lattice ultrafast laser scanning pattern;

[0029] Figure 5 is a structural schematic diagram of the present application square lattice ultrafast laser scanning pattern. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention relates to a method for controlling the distribution of solder during metal-glass laser brazing, comprising the following steps:

[0032] Step 1: Material preparation: Clean, dry and remove surface oil from the glass and metal substrates to be welded;

[0033] The cleaning methods for glass and metal substrates include ultrasonic cleaning, alcohol cleaning, or acetone solvent cleaning.

[0034] Step 2: Design the specified ultrafast laser scanning pattern according to the requirements. The ultrafast laser scanning pattern area (processing area) has good hydrophobic properties, while the unprocessed area is the area where solder accumulates and is distributed.

[0035] The ultrafast laser scanning pattern can be a circular ring, a grid pattern, or other shapes.

[0036] Step 3: Use a picosecond laser to scan several horizontal and vertical groove arrays in a designated processing area on the surface of the metal substrate to form a regular square prism microstructure array.

[0037] The picosecond laser has a pulse width of 8 ps, a wavelength of 1030 nm, an average laser output power of 2.5 W, a scanning speed of 250 mm / s, a line spacing of 50 μm, and can be repeated 50 times.

[0038] Step 4: Filling and positioning of solder paste: Spread solder paste on the surface of the metal substrate, use a clamping and positioning device to hold the glass on the solder paste, and adjust the glass position to the required position. At this time, the solder paste should fill the gap between the glass and the metal substrate to be soldered.

[0039] Step 5: Continuous laser brazing: Keeping the clamping unchanged, that is, the relative position between the glass and the metal substrate remains unchanged, a continuous laser is used to irradiate the paste-like brazing material through the glass, causing the brazing material to melt, flow, and fill the gap between the glass and the metal substrate. When the continuous laser is removed, the molten brazing material solidifies again, forming a compact brazing metal layer filling the gap between the glass and the metal.

[0040] Among them, the continuous laser can be a pulsed laser, the purpose of which is to provide a local heat source to melt the paste-like brazing filler metal at the laser focus point. The appropriate heating power and time need to be selected according to the different brazing filler metals. When the area of ​​the brazing filler metal filling the gap is relatively large, the laser can be changed from fixed point to scanning to ensure that the brazing filler metal in a large area can be heated and melted.

[0041] In one specific embodiment, the metal substrate includes, but is not limited to, stainless steel.

[0042] In one specific embodiment, the solder paste is SnAg0.3Cu0.7 solder paste, but the type of solder is not limited to this. The solder paste should be selected to effectively connect with the metal to be soldered. Flux can also be used to increase the solderability of the solder on the metal to be soldered.

[0043] Example 1

[0044] The following steps are performed to braze a 1mm thick stainless steel sheet with an 80μm gap to a 10mm thick K9 glass sheet:

[0045] 1. Ultrasonic cleaning of stainless steel sheets and K9 glass for 5 minutes, then drying for later use;

[0046] 2. The ultrafast laser scanning pattern is a grid pattern, such as... Figure 1 As shown, the outer edge of the grid is 12mm, the inner edge is 8mm, and the width of the cross lines is 1mm.

[0047] 3. Using a picosecond laser, several horizontal and vertical groove arrays are scanned within the lattice-shaped pattern processing area, ultimately forming a regular square prism microstructure array, such as... Figure 2 As shown, the average laser output power is 5W, the scanning speed is 250mm / s, the scanning line spacing is 50μm, and the number of repeated scans is 50.

[0048] 4. Apply a layer of SnAg0.3Cu0.7 solder paste to the center of the area to be soldered. Place 80μm thick pads at both ends of the stainless steel sheet. Place the K9 glass on the pads so that the K9 glass and the stainless steel sheet are 80μm apart. Use long-tail clips to clamp and fix the stainless steel sheet and the K9 glass.

[0049] 5. Use a continuous laser to directly irradiate the brazing filler metal through the glass for 30 seconds to melt the filler metal. Turn off the laser, and the filler metal will re-solidify and reliably bond with the stainless steel sheet. The output power of the continuous laser is 60W and the defocusing amount is 8mm.

[0050] The distribution of brazing filler metal after brazing is as follows: Figure 3 As shown.

[0051] Example 2

[0052] The following steps are performed to braze a 1mm thick stainless steel sheet with an 80μm gap to a 10mm thick K9 glass sheet:

[0053] 1. Ultrasonic cleaning of stainless steel sheets and K9 glass for 5 minutes, followed by drying;

[0054] 2. The ultrafast laser scanning pattern is a multi-ring pattern, such as... Figure 4 As shown, the outer diameter of the ring is 7mm, the inner diameter is 4mm, and the distance between the rings is 5mm;

[0055] 3. Using a picosecond laser, several horizontal and vertical groove arrays are scanned within the multi-ring pattern processing area, ultimately forming a regular square prism microstructure array, such as... Figure 2 As shown, the average laser output power is 5W, the scanning speed is 250mm / s, the scanning line spacing is 50μm, and the number of repeated scans is 50.

[0056] 4. Apply a layer of SnAg0.3Cu0.7 solder paste to the center of the area to be soldered. Place 80μm thick pads at both ends of the stainless steel sheet. Place the K9 glass on the pads so that the K9 glass and the stainless steel sheet are 80μm apart. Use long-tail clips to clamp and fix the stainless steel sheet and the K9 glass.

[0057] 5. Use a continuous laser to directly irradiate the brazing filler metal through the glass for 30 seconds to melt the filler metal. Turn off the laser, and the filler metal will re-solidify and reliably bond with the stainless steel sheet. The output power of the continuous laser is 60W and the defocusing amount is 8mm.

[0058] The distribution of brazing filler metal after brazing is as follows: Figure 5 As shown.

[0059] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for controlling filler metal distribution during metal-glass laser brazing, characterized in that, Includes the following steps: Step 1: Material preparation: Clean, dry and remove surface oil from the glass and metal substrates to be welded; Step 2: A groove array is fabricated in the processing area on the surface of the metal substrate using a laser to form a regular square prism microstructure array; Step 3: Spread the solder paste onto the surface of the metal substrate, and place the glass treated in Step 1 on the solder paste, so that the solder paste fills the gap between the glass and the part of the metal substrate to be soldered. Step 4: Continuous laser light shines through the glass onto the solder paste, causing the solder to melt and flow to fill the gap between the glass and the metal substrate; As the continuous laser is removed, the molten solder re-solidifies, forming a dense solder metal layer that fills the gaps between the glass and metal substrates. In step two, before processing the trench array within the processing area, an ultrafast laser scanning pattern is designed on the surface of the metal substrate to form the laser scanning area, i.e., the processing area; The ultrafast laser scanning pattern includes circular and grid patterns; The area on the surface of the metal substrate without an ultrafast laser scanning pattern is the solder distribution area.

2. The method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, In step one, the cleaning methods for glass and metal substrates include ultrasonic cleaning, alcohol cleaning, or acetone solvent cleaning.

3. The method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, The solder paste is SnAg0.3Cu0.7 solder paste.

4. The method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, In step three, the laser is a picosecond laser with a laser pulse width of 8 ps, a wavelength of 1030 nm, an average laser output power of 2.5 W, a scanning speed of 250 mm / s, a scanning line spacing of 50 μm, and a number of repeated scans of 50.

5. A method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, In step three, during the positioning process of the glass and the metal substrate, the relative pose of the glass and the metal substrate is determined by the clamping and positioning mechanism.

6. The method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, In step four, the continuous laser is a pulsed laser.

7. The method for controlling filler metal distribution during metal-glass laser brazing according to claim 1, characterized in that, In step four, when the gap between the glass and the metal substrate exceeds 10 μm, the laser changes from a fixed point to a scanning motion, so that the solder can be heated and melted.

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