CN103358028A - Method and system for scribing brittle ultrathin piece by water jet and laser - Google Patents

Abstract

The present invention is a method and system for water jet laser engraving ultra-thin sheets of brittle materials. In the method, the laser beam passes through the water jet beam and focuses on the surface of the workpiece. The distance from the center of the focal point of the laser beam is equal to or less than 1 to 2.5 times the radius of the focal point of the laser beam on the workpiece surface. The distance between the jet beam generated by the jet nozzle of the system and the intersection point of the laser beam on the surface of the workpiece is equal to or less than 1 to 2.5 times the radius of the focus point of the laser beam. The longitudinal centerline of the jet nozzle may coincide with the centerline of the laser beam. The workbench is a working chamber filled with water, and there is a water layer of 0.5-1.5mm on the surface of the workpiece on the top surface of the boss of the workbench. The overflow port of the working chamber is connected to the pool, and the water pump pumps the water in the pool into the jet nozzle to generate the water jet. Laser etching and scribing, the water jet beam cools and scours the processing area. It achieves the effects of no recast layer, no residual stress, and no microcracks on the machined surface, and improves the machining efficiency.

Description

Method and system for scribing ultra-thin sheets of brittle materials by water jet laser

technical field

The invention relates to the technical field of laser processing, in particular to a method and system for marking ultra-thin sheets of brittle materials with water jet laser.

Background technique

For electronic products, the market trend of "light, thin, short, and small" has changed the packaging of integrated circuits from a single chip to a stacked package of multi-layer chips. 7-8 layers of chips are superimposed in an IC, and the total volume after packaging is reduced to a fraction of the previous single-layer chip IC. Therefore, the thickness of the silicon wafer has also been reduced from 650 μm to 120 μm, and the lowest has reached 25 μm. Before the silicon wafer is diced, the whole wafer is processed, and after dicing, the single chip used in the IC packaging process is obtained. Due to the increase in wafer diameter and thinning in thickness, the tensile and extrusion strength of the wafer is getting weaker and weaker, and it is extremely sensitive to mechanical external force, and the fragmentation rate increases significantly during dicing. At the same time, more and more circuits are integrated on the unit area of the chip, and the scribe line for division is smaller, generally only about 30 μm. Therefore, higher requirements are put forward for the processing range, processing accuracy, reliability and stability of the scribing equipment.

The traditional diamond wheel scribing process has reached its limit. For manufacturers, wafer dicing technology and process equipment have become one of the most difficult and costly processes on the packaging line. In addition, low-k materials, sapphire-based LED wafer dicing, in MEMS, more chips need to be punched, special-shaped holes and local thinning, composite chips, chips covered with diamond layers And chip cutting of complex microstructures, etc., traditional diamond blades are not competent. However, the market demand for these products has grown rapidly, forcing the industry to find a new generation of dicing solutions.

The quality of laser scribing is acceptable in some low-level applications, but it is difficult to be recognized in the processing of integrated circuits due to defects such as excessively large heat-affected zones, large pollution, and severe thermal deformation. In recent years, ultraviolet laser and femtosecond laser scribing technology have significantly improved thermal effects and improved cutting quality.

Among all kinds of laser solutions, the most prominent is the world patent-Swiss Micro Jet Laser Technology (Laser Micro Jet). Total reflection at the gas-liquid interface. Water cools the workpiece during laser processing, which is excellent in eliminating laser thermal effects. Micro water jet laser scribing technology has been widely used in many high-tech fields abroad. However, it is difficult to control the focused laser beam to align with the micro water column in its equipment, and a little carelessness will lead to ablation and damage the nozzle that produces the water column. The aspect ratio of the nozzle is required to reach 20, the aperture is extremely small, and the production materials are not easy to obtain, and the consumable nozzle increases the cost of using this method. In addition, it is difficult to control the conversion of high-pressure and low-speed water flow into a low-pressure, high-speed and stable micro-water column through the water cavity. The optical path of the light beam in the water column is long, and the energy loss of stimulated Raman scattering is large. These technical difficulties lead to the high price of micro-waterjet laser equipment and high equipment maintenance costs, which greatly limit the application of this technology.

To this end, in recent years, Dr. Richerzhagen and others have studied the combined processing of water-guided laser micromachining and diamond cutting, and explored a method to combine the processing performance advantages of the two processes, but it is difficult to apply it in practice because the equipment is more complicated.

Contents of the invention

The purpose of the present invention is to design a method for water jet laser engraving ultra-thin sheets of brittle materials. The laser beam is focused on the workpiece surface, and the distance between the center of the injection point of the water jet beam on the workpiece surface and the focus point center of the laser beam on the workpiece surface It is equal to or less than 1 to 2.5 times the radius of the focus point of the laser beam on the workpiece surface. The water jet beam cools the laser processing area, and scours and reduces the recasting layer, so that the processing surface has no recasting layer, no residual stress, and no microcracks. The "three-no" processing effect.

Another object of the present invention is to design a water jet laser marking system for brittle material ultra-thin sheets, including a laser control unit, a pulse laser, a focusing lens and a workbench, and a water jet nozzle, the laser beam passing through the water jet beam , the water jet beam cools the laser beam processing area, and completes the scribing of ultra-thin sheets of brittle materials with high quality, high efficiency and no surface defects.

The method for marking ultra-thin sheets of brittle materials with water jet laser designed in the present invention, the laser beam is focused on the surface of the workpiece for processing, the laser beam of the present invention passes through the water jet beam and focuses on the surface of the workpiece, and the spraying of the water jet beam on the surface of the workpiece The distance between the point center and the focus point center of the laser beam on the surface of the workpiece is equal to or less than 1 to 2.5 times the radius of the focus point of the laser beam on the surface of the workpiece.

The laser beam passes through the water jet beam and focuses on the workpiece surface for processing. Because the intersection point of the water jet beam and the workpiece surface, that is, the injection point of the water jet beam is close to or coincides with the focus point of the laser beam on the workpiece surface, the high-speed water jet The cooling and scouring effect on the laser processing area reduces the recast layer in the laser processing area, so that the processed surface of the workpiece has no recast layer, no residual stress, and no microcracks. After the laser beam passes through the water jet beam, it is focused on the surface of the workpiece, and the laser beam will not damage the jet nozzle.

According to the above-mentioned method for marking ultra-thin sheets of brittle materials by water jet laser, the system for marking ultra-thin sheets of brittle materials by water jet laser designed in the present invention includes a laser control unit, a pulse laser and a focusing lens, and the laser control unit is connected to control the pulse Laser, the laser beam emitted by the pulse laser is focused by the focusing lens, and the workpiece is fixed on the worktable. The workbench is equipped with a workbench X-axis drive mechanism and a workbench Y-axis drive mechanism. The laser beam is focused on the workpiece surface through the focusing lens. It also includes a jet nozzle, the distance between the center of the injection point of the water jet beam on the surface of the workpiece and the center of the focal point of the laser beam on the surface of the workpiece is equal to or less than 1 to 2.5 times the radius of the focal point of the laser beam on the surface of the workpiece.

The diameter of the orifice of the jet nozzle is on the order of mm.

The longitudinal centerline of the water jet coincides with the centerline of the laser beam, the laser beam passes through the focusing lens, passes through the nozzle hole of the jet nozzle, passes through the water jet, and focuses on the surface of the workpiece. The jet stream coincides with the center of the injection point on the workpiece surface.

The water of the water jet is ultrapure water, and the ultrapure water is deionized water or distilled water.

There is a working chamber filled with water above the worktable, and the boss on the top of the worktable is located in the working chamber. The surface of the workpiece on the top surface of the boss of the worktable is 0.5-1.5mm lower than the water surface in the working chamber, that is, there is a gap of 0.5-1.5mm on the surface of the workpiece. water layer.

The working cavity has an overflow port, and the lowest point of the overflow port is 0.5-1.5 mm higher than the surface of the workpiece on the workbench to maintain the depth of the water layer on the surface of the workpiece.

The overflow port of the working chamber is connected to the pool through the overflow pipe, and the water that produces the jet is stored in the pool. The inlet of the water pump is connected to the pool through the filter to absorb the water in the pool. The outlet of the water pump is connected to the jet nozzle. A water jet is generated through the jet nozzle.

The outlet of the water pump is connected to the jet nozzle through the ball valve, and the ball valve is equivalent to a liquid flow switch. When the ball valve is opened, the water pump can pressurize and send water to the jet nozzle.

The outlet of the water pump is connected to one end of the overflow pressure regulating valve through a tee, the other end of the overflow pressure regulating valve is connected to the jet nozzle, and the third end is connected back to the pool through the overflow pressure regulating pipe. Adjusting the overflow pressure regulating valve can adjust the water pressure delivered by the water pump to the jet nozzle, thereby adjusting the water jet injection speed of the jet nozzle. The water jet spray speed is adjusted according to the thickness of the material being processed.

The X-axis servo motor and the Y-axis servo motor are respectively connected to the X-axis drive mechanism of the workbench and the Y-axis drive mechanism of the workbench, and both the X-axis servo motor and the Y-axis servo motor are connected to the computer.

When the water jet laser engraving ultra-thin sheet of brittle material is used, the workpiece is fixed on the top surface of the boss of the worktable, in the focus area of the laser beam, and the height of the overflow port of the working chamber is adjusted so that the water depth on the surface of the workpiece is 0.5~ 1.5mm;

Confirm that the pipeline is unblocked, open the ball valve, turn on the water pump, adjust the overflow pressure regulating valve, so that the water passes through the jet nozzle to produce a high-speed and stable water jet beam, and make the water jet beam on the center of the injection point on the workpiece surface and the laser beam on the workpiece surface. The distance from the center of the focus point is equal to or less than 1 to 2.5 times the radius of the focus point of the laser beam;

Adjust the laser control unit, control the pulse laser to generate the laser beam, adjust the focusing lens, the laser beam is focused on the surface of the workpiece, the X-axis servo motor and the Y-axis servo motor respectively drive the X-axis drive mechanism of the worktable and the Y-axis drive mechanism of the worktable to drive the work The table moves on the X-axis and Y-axis, and the focused laser beam etches and scribes the surface of the workpiece on the table according to the set path. At the same time, the water jet beam cools and washes the laser processing area on the surface of the workpiece 6. To avoid the recasting layer, the water layer on the surface of the workpiece is further cooled, reducing the temperature difference on the thin sliced workpiece, and achieving the "three nos" processing effect of no recasting layer, no residual stress, and no microcracks on the diced processing surface.

The pressure of the water pumped into the jet nozzle is 0.3Mpa-1Mpa.

Compared with the prior art, the advantages of the method and system for water jet laser scribing ultra-thin sheets of brittle materials of the present invention are: 1. The stable sprayed water jet beam cools the laser processing scribing area, and the cooling effect of water can be eliminated. Thermal impact can eliminate residual stress and micro-cracks; and high-speed scouring can also take away molten droplets, which can effectively prevent the formation of recast layer and improve the scribing yield rate of brittle materials; 2. Ensure the jet beam injection point and laser beam focus The scribing position of the point on the surface of the workpiece is completely coincident or nearly coincident, and the combined processing effect of the laser scribing of the water jet not only optimizes the quality of the scribing surface, but also improves the processing efficiency; it is especially suitable for ultra-thin silicon in the electronics industry. 3. The laser beam is focused only after passing through the water jet beam, which will not ablate and damage the jet nozzle, and the optical path of the laser beam in water is short, the absorption of light by water is extremely small, and the loss of laser energy is small; 4 , The system structure is simple, easy to install, repair, easy to operate, suitable for popularization and application.

Description of drawings

Fig. 1 is the structural schematic diagram of the method and system embodiment 1 of the water jet laser engraving brittle material ultra-thin sheet;

FIG. 2 is a schematic structural diagram of Embodiment 2 of the method and system for scribing ultra-thin sheets of brittle materials by water jet laser.

The labels in the figure are:

1. Laser control unit, 2. Pulse laser, 3. Mirror, 4. Focusing lens, 5. Jet nozzle, 6. Workpiece, 7. Working chamber, 8. Workbench, 9. Pool, 10. Filter, 11 , Overflow pressure regulating valve, 12, water pump, 13, ball valve.

Detailed ways

Embodiment 1 of the method and system for scribing ultra-thin sheets of brittle materials by water jet laser

The structure of Embodiment 1 of the system embodiment 1 of the water jet laser engraving brittle material ultra-thin sheet is shown in Figure 1, including a laser control unit, a pulse laser, a focusing lens, and a jet nozzle. The laser control unit 1 is connected to and controls the pulse laser 2, and the pulse laser The laser beam emitted by 2 is changed in direction by the mirror 3, and then focused on the surface of the workpiece 6 by the focusing lens 4. There is a working chamber 7 equipped with water above the workbench 8. The workbench 8 has a boss located in the workchamber 7. The workpiece 6 is fixed on the boss of the workbench 8. The surface of the workpiece 6 on the boss of the workbench 8 is lower than the work chamber. 7. The surface of the inner water is 0.5-1.5mm, that is, there is a water layer of 0.5-1.5mm on the surface of the workpiece 6. The working cavity 7 has an overflow port, and the lowest point of the overflow port is 0.5-1.5 mm higher than the surface of the workpiece 6 on the workbench 8 . The workbench 8 is equipped with a workbench X-axis drive mechanism and a workbench Y-axis drive mechanism, and the X-axis servo motor and the Y-axis servo motor are respectively connected to the workbench X-axis drive mechanism and the workbench Y-axis drive mechanism. Both the X-axis servo motor and the Y-axis servo motor are connected with the computer.

The water in this example is deionized water.

The overflow port of the working chamber 7 is connected to the pool 9 through the overflow pipe, and the deionized water that produces jet flow is stored in the pool 9, and the inlet of the water pump 12 is connected to the pool 9 through the filter 10 to absorb the deionized water in the pool 9. 12 The outlet is connected to the jet nozzle 5 through the ball valve 13, and the jet nozzle 5 produces a water jet stream. The jet nozzle 5 orifice diameter of this example is 3mm.

The outlet of the water pump 12 is also connected to one end of the overflow pressure regulating valve 11 through a tee, and the other end of the overflow pressure regulating valve 11 is connected back to the pool 12 through an overflow pressure regulating pipe.

The method of the water jet laser engraving ultra-thin sheet of brittle material in this example is as follows: the laser beam is focused on the surface of the workpiece 6, and the radius of the focus point is 25 μm; The distance between the center of the focus point is 20 μm, which is smaller than the radius of the focus point of the laser beam on the workpiece surface. It can be seen from Figure 1 that the laser passes through the lateral incident water jet beam to reach the surface of the workpiece without damaging the jet nozzle. In this example, the centerline of the laser beam and the centerline of the water jet beam form an angle of 60 degrees, but the intersection between the two and the workpiece interface is only 20μm. The water jet beam fully cools and scours the laser processing area to ensure the quality of the laser processing surface.

The working parameters of the pulse laser 2 in this example are: laser power 50W, laser repetition frequency 100Hz. The workpiece 6 is an ultra-thin silicon wafer with a thickness of less than 150 μm, a scribing line width of ≤50 μm, and a maximum scribing speed of 150 mm/s. Use a high-power optical microscope and a computer image acquisition system to analyze the surface morphology of the scribed ultra-thin silicon wafers, and use a surface profile tester to measure the etching depth for inspection. The scribed products have no recast layer, no residual stress, and no The ratio of fine products of ultra-thin silicon wafers with microcracks is as high as 85%.

Embodiment 2 of the method and system for scribing ultra-thin sheets of brittle materials by water jet laser

The structure of Embodiment 2 of the system embodiment 2 of the water jet laser marking brittle material ultra-thin sheet is shown in Figure 2. In this example, the longitudinal centerline of the jet nozzle 5 coincides with the centerline of the laser beam, and the laser beam passes through the focusing lens 4 and passes through the jet nozzle. The spray hole of 5 passes through the water jet and focuses on the surface of the workpiece 6, and the center of the focus point of the laser beam on the surface of the workpiece 6 coincides with the center of the injection point of the water jet beam on the surface of the workpiece 6. Cooling and flushing are better accomplished with water jets.

The jet nozzle 5 orifice diameter of this example is 3mm.

The water of this example water jet is distilled water.

The water jet laser engraving method for brittle material ultra-thin sheets in this example is that the center line of the water jet beam coincides with the center line of the laser beam, and the center of the injection point of the water jet beam on the surface of the workpiece and the center of the focal point of the laser beam on the surface of the workpiece coincide.

The distilled water pressure that water pump 12 sends into jet nozzle 5 is 1.5Mpa. The working parameters of the pulsed laser 2 are: laser power 50W, laser repetition frequency 200Hz. The workpiece 6 is an ultra-thin silicon wafer with a thickness of less than 150 μm, a scribing line width of ≤50 μm, and a maximum scribing speed of 150 mm/s. The result of this example is that the yield rate of ultra-thin silicon wafers is as high as 85%.

The above-mentioned embodiments are only specific examples for further specifying the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the disclosed scope of the present invention are included in the protection scope of the present invention.

Claims (10)

1. The method of water jet laser engraving ultra-thin sheets of brittle materials, the laser beam is focused on the surface of the workpiece for processing, which is characterized in that: The laser beam passes through the water jet beam and focuses on the surface of the workpiece. The distance between the center of the injection point of the water jet beam on the surface of the workpiece and the center of the focus point of the laser beam on the surface of the workpiece is equal to or less than 1 of the radius of the focus point of the laser beam on the surface of the workpiece. ~2.5 times. 2. According to claim 1, the water jet laser scribes the system of the brittle material ultrathin sheet according to the method design of the water jet laser scribe brittle material ultrathin sheet, comprises a laser control unit, a pulse laser and a focusing lens, and the laser control unit is connected, controlled Pulse laser, the laser beam emitted by the pulse laser is focused by the focusing lens, the workpiece is fixed on the worktable, and the workbench is equipped with a workbench X-axis drive mechanism and a workbench Y-axis drive mechanism; it is characterized in that: The laser beam is focused on the surface of the workpiece (6) through the focusing lens (4); it also includes a jet nozzle (5), which generates a water jet beam at the center of the injection point on the surface of the workpiece (6) and the laser beam on the workpiece (6) The distance between the center of the focus point on the surface is equal to or less than 1 to 2.5 times the radius of the focus point of the laser beam on the surface of the workpiece (6). 3. The system for marking the ultra-thin sheet of brittle material by water jet laser according to claim 2, characterized in that: The longitudinal centerline of the water jet coincides with the centerline of the laser beam. The laser beam passes through the focusing lens (4), passes through the nozzle hole of the jet nozzle (5), passes through the water jet, and focuses on the surface of the workpiece (6). The center of the focus point on the surface of the workpiece (6) coincides with the center of the injection point of the water jet beam on the surface of the workpiece (6). 4. The water jet laser marking system for ultra-thin sheets of brittle materials according to claim 2 or 3, characterized in that: The nozzle hole diameter of the jet nozzle (5) is on the order of mm. 5. The water jet laser marking system for ultra-thin sheets of brittle materials according to claim 2 or 3, characterized in that: The water of the water jet is ultrapure water, and the ultrapure water is deionized water or distilled water. 6. The system for marking ultra-thin sheets of brittle materials by water jet laser according to claim 2 or 3, characterized in that: There is a working chamber (7) filled with water above the workbench (8), the boss on the top of the workbench (8) is located in the work chamber (7), and the workpiece (6) on the top surface of the boss of the workbench (8) The surface is 0.5mm-1.5mm lower than the water surface in the working chamber (7). 7. The system for marking ultra-thin sheets of brittle materials by water jet laser according to claim 6, characterized in that: The working cavity (7) has an overflow port, and the lowest point of the overflow port is 0.5 mm to 1.5 mm higher than the surface of the workpiece (6) on the workbench (8). 8. The system for marking ultra-thin sheets of brittle materials by water jet laser according to claim 7, characterized in that: The overflow port of the working chamber (7) is connected to the pool (9) through the overflow pipe, and the water pool (9) stores jet-generating water, and the inlet of the water pump (12) is connected to the pool (9) through the filter (10). Inside, the outlet of the water pump (12) is connected to the jet nozzle (5). 9. The system for marking ultra-thin sheets of brittle materials by water jet laser according to claim 8, characterized in that: The outlet of the water pump (12) is connected to the jet nozzle (5) through the ball valve (13). 10. The system for marking ultra-thin sheets of brittle materials by water jet laser according to claim 9, characterized in that: The outlet of the water pump (12) is connected to one end of the overflow pressure regulating valve (11) through a tee, and the other end of the overflow pressure regulating valve (11) is connected back to the pool (9) through an overflow pressure regulating pipe.

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