TWI848645B - Laser thermal processing system - Google Patents

Abstract

A laser thermal processing system is disclosed. The laser thermal processing system includes a laser light source, a reflector, an actuator, a control unit, a first telecentric lens, a mask, a second telecentric lens and a third telecentric lens. The present invention uses three telecentric lenses to carry out the relay transmission of the laser beam. After the laser beam passes through the system, the output energy distribution becomes uniform and position accuracy is improved, which solves the problem of Gaussian distribution concentration of energy in the prior art and can average the energy distribution of the laser beam on the working surface, thereby optimizing the laser thermal processing results.

Description

Laser thermal processing system

The present invention relates to a processing system, in particular a laser thermal processing system.

Lasers generate amplified light through stimulated radiation, and have the advantages of small divergence, high power, excellent monochromaticity, and good coherence. Therefore, lasers are widely used in various fields, such as medical surgery, military weapons, distance measurement, skin beauty, etc. In the engineering field, the most well-known application is thermal processing. The energy used by the laser is large enough that it can sinter, heat and ionize on the surface of an object to form a predetermined surface shape or even cut off part of the object. On the other hand, if the energy and emission direction of the laser can be precisely controlled, the laser can be used to target tiny and widely distributed target points. Laser lift-off (LLO) is a technique that separates two or more adhesives through laser processing. It is commonly used in LED manufacturing and ultra-thin silicon wafer manufacturing. For example, laser is applied to the ablative adhesive layer to peel the formed device off the back of the substrate. In recent years, laser lift-off technology has also been applied to the mass transfer process of Micro LED, effectively reducing the production cost of Micro LED displays and bringing a new perspective to mankind. It can be seen that laser processing is no less important than photolithography and is also a major technology to promote technological progress.

加工位置精度問題。 At present, in addition to using a high-energy laser source as the mechanism for generating the laser beam, the commonly used laser thermal processing system also uses a combination of a galvanometer and an f-theta lens to deflect the laser path and focus it within the effective range of the processing surface for laser thermal processing. The laser beam passing through the f-theta lens has a disadvantage: if the processing area is at the edge, the spot shape of the laser beam will change slightly. Therefore, for precision processing requirements, only the processing center area can be used for processing. To solve this problem, some improved technologies use a telecentric scanner to replace the galvanometer and f-theta lens combination. Although the combination of a galvanometer and a telecentric scanner can overcome the slight change in the shape of the laser beam spot when processing the edge of the area, this system combination is still limited by the energy concentration of the Gaussian spot after focusing and the comprehensive hardware resolution, optical adjustment and correction, and the high-speed movement of the galvanometer system.

Processing position accuracy problem.

In order to solve the problem of laser beam energy generating Gaussian distribution concentration in the prior art, and further average the energy distribution of the laser beam on the working surface and the laser processing position accuracy and processing position precision of the processing surface, so as to optimize the laser thermal processing results, the present invention was developed and proposed.

This paragraph extracts and compiles certain features of the invention. Other features will be revealed in subsequent paragraphs. Its purpose is to cover various modifications and similar arrangements within the spirit and scope of the attached patent application.

In order to solve the problem of Gaussian distribution concentration of laser beam energy in the prior art, and to further average the energy distribution of the laser beam on the working surface and the laser processing position accuracy of the processing surface, so as to optimize the laser thermal processing results, the present invention proposes a laser thermal processing system. The system includes: a laser light source, which emits several waves of laser beams in sequence; a reflector, the laser beams are directed to the reflector, and the reflector is controlled to rotate to change the reflection direction of the laser beams; a first telecentric lens, after the reflected laser beams pass through the first telecentric lens, the paths are changed for the first time to be parallel to each other and parallel to the optical axis of the first telecentric lens; a mask, on which a plurality of openings are opened, and the laser beams that change their paths for the first time pass through the corresponding openings vertically in sequence; a second telecentric lens, The first telecentric lens and the first telecentric lens are respectively arranged on both sides of the mask, and the laser beams that change the path for the first time change the path for the second time after passing through the second telecentric lens, and are biased towards the focal direction of the second telecentric lens; and a third telecentric lens is arranged on the same side of the mask but farther away from the second telecentric lens, and the laser beams that change the path for the second time change the path for the third time after passing through the third telecentric lens to be parallel to each other and parallel to the optical axis of the third telecentric lens, and are sequentially imaged vertically on a working plane for thermal processing.

According to the present invention, the energy density distribution of the laser beam passing through any opening plane is more uneven than the energy density distribution of the same laser beam irradiated on the working plane.

According to the present invention, the optical axes of the first telecentric lens, the second telecentric lens and the third telecentric lens substantially coincide.

According to the present invention, the distance between the opposite sides of the second telecentric lens and the third telecentric lens is the sum of their working distances.

According to the present invention, the second telecentric lens and the third telecentric lens have different magnifications, thereby magnifying or reducing the ratio of the image of each laser beam on the working plane after passing through the corresponding opening to the area of the opening.

According to the present invention, the first telecentric lens is placed opposite to the second telecentric lens, and the second telecentric lens is placed opposite to the third telecentric lens.

According to the present invention, the reflector is connected to an actuator and is controlled by the actuator to rotate.

The laser thermal processing system further includes a control unit connected to the laser light source and the actuator, controlling the laser light source to emit a laser beam, and rotating the angle of the reflective mirror through the actuator when the laser light source stops emitting a laser beam.

According to the present invention, the integrated hardware resolution, optical adjustment and correction and high-speed movement of the galvanometer system can achieve a laser irradiation position accuracy of less than 3μm on the working plane.

The present invention uses three telecentric lenses to relay the laser beam and makes the laser energy distribution uniform through mask imaging, solving the problem of energy generation Gaussian distribution concentration in the existing technology. It can average the energy distribution of the laser beam on the working surface, thereby optimizing the laser thermal processing results.

1: Laser thermal processing system

2: Objects

10: Laser light source

20: Reflector

25: Actuator

30: Control unit

40: First telecentric lens

50:Mask

60: Second telecentric lens

70: Third telecentric lens

D2: Second working distance

D3: The third working distance

F1: First straight distance

F2: Second straight distance

F3: The third straight distance

L: Distance

O: Opening

O1: First opening

O2: Second opening

O3: The third opening

O4: The fourth opening

O5: The fifth opening

P1: First position

P2: Second position

P9: Last position

FIG1 is a schematic diagram of components of a laser thermal processing system according to an embodiment of the present invention, wherein the laser thermal processing system performs thermal processing on a first position of an object on a working plane.

FIG2 shows the laser thermal processing system performing thermal processing on a second position of the object on the work plane.

FIG3 shows the laser thermal processing system performing thermal processing on the object in the final position on the work plane.

Figure 4 shows the opening positions and shapes of the mask used in the experimental example.

Figures 5 to 9 compare the energy distribution images of the same laser beam when it passes through a reference plane and the working plane.

In order to make the description of the disclosed content more detailed and complete, the following is an illustrative description of the implementation and specific embodiments of the present invention.

Please see FIG. 1 for a schematic diagram of components of a laser thermal processing system 1 according to an embodiment of the present invention. The laser thermal processing system 1 performs thermal processing on a first position P1 of an object 2 on a working plane. The laser thermal processing system 1 includes a laser light source 10, a reflector 20, an actuator 25, a control unit 30, a first telecentric lens 40, a mask 50, a second telecentric lens 60 and a third telecentric lens 70. The types, functions, and mutual actuation modes of the aforementioned technical components, as well as the operation of the entire system, will be described in detail as follows in conjunction with the relevant diagrams.

The laser light source 10 is a device for providing heat treatment laser, which can emit several waves of laser beams in sequence. The present invention does not limit the wavelength and pulse width of the laser beam emitted by the laser light source 10, which can range from infrared to ultraviolet. In addition, the laser beam can be in the form of a pulse, and a wave of laser beams formed contains multiple pulse light waves; the laser beam can also be in the form of a continuous form, and energy is continuously provided in a wave of laser beams formed. The laser light source 10 is switched on and off to generate waves of laser beams, and the energy and emission time of each wave of laser beams can be controlled by the laser light source 10 to meet the operational requirements of the object to be heat treated.

The reflector 20 can be adjusted in direction in coordination with the laser light source 10. When the laser beams are directed toward the reflector 20, the reflector is controlled to rotate to change the reflection direction of the laser beams. Since the heat-processed area is a plane, the reflector 20 cannot rotate only in a single direction of the plane, but needs to be able to rotate in two directions in the spatial plane. Therefore, the reflector 20 can also be a combination of two independently rotating sub-reflectors, one of which rotates on the X axis and the other rotates on the Y axis. The material of the reflector 20 is not limited, as long as it can effectively reflect the laser beam and reduce energy loss. Although the reflector 20 itself can rotate within a limited range, it is not a device with rotational power. Therefore, the actuator 25 is a device used to actually control the rotation and positioning of the reflector 20. The reflector 20 is connected to the actuator 25 and rotates in a direction controlled by the actuator 25. The actuator 25 can use two motors for X-axis rotation and Y-axis rotation as drivers to determine the position of a point at a time, and the position of the points at different times can be controlled by the scanning frequency to achieve the change of the entire scan pattern.

The control unit 30 is a device used by the operator of the system to control the laser light source 10 and the actuator 25. The control unit 30 is connected to the laser light source 10 and the actuator 25 (including the connection of power and control signals), controls the laser light source 10 to emit a laser beam, and rotates the angle of the reflector 20 through the actuator 25 when the laser light source 10 stops emitting a laser beam. Since the motor of the actuator 25 is a stepper motor, the control unit 30 can accurately control the reflector 20 to stop moving temporarily after rotating, and use this time to drive the laser light source 10 to emit a laser beam. Therefore, each wave of laser beam can ensure that the direction of emission will not deviate and provide sufficient energy to the object that needs thermal processing. Please refer to Figures 1 and 2 at the same time. Figure 2 shows that the laser thermal processing system 1 performs thermal processing on the second position P2 of the object 2 on the working plane. Since the object 2 needs to be heat-processed at two different positions, it can be seen that the angle of the reflector 20 in Figures 1 and 2 has changed, and the laser beam (represented by a dotted bottom line) emitted by the laser light source 10 has also changed its reflection angle after passing through the reflector 20. In practice, some commercially available laser oscillators include a combination of the laser light source 10, the reflector 20 and the actuator 25 that are consistent with the above, but need to be able to accept the operation control of the control unit 30. According to the present invention, the control unit 30 can be any independent controller or a multi-purpose industrial computer. In this embodiment, an industrial computer is used as an example for explanation.

The use and installation design of the first telecentric lens 40, the second telecentric lens 60 and the third telecentric lens 70 of the present invention are features that are different from existing laser thermal processing technologies. For general laser thermal processing, after the laser light passes through a telecentric lens, a parallel laser beam is formed, and then the object to be heated can be thermally processed. However, this approach results in an uneven Gaussian distribution of energy distribution, which may cause the object to be heated to fail to achieve the intended results due to uneven heating energy, such as being burned through or the heat weld failing to fully join. The function of the first telecentric lens 40 is that after the aforementioned reflected laser beams pass through the first telecentric lens 40, the paths are changed for the first time to be parallel to each other and to the optical axis of the first telecentric lens 40. According to the present invention, the optical axes of the first telecentric lens 40, the second telecentric lens 60 and the third telecentric lens 70 substantially coincide. Therefore, in Figures 1 and 2 (and Figure 3), the three coincident optical axes are represented by a virtual straight line. It can be seen from Figures 1 and 2 that after the laser beam is emitted from the first telecentric lens 40, the direction is perpendicular to the direction of the mask 50.

The mask 50 is located on a reference plane below the first telecentric lens 40, and is provided with a plurality of openings O (nine openings O are used as an example in this embodiment, but the number is not limited in practice). The laser beams that change their paths for the first time through the first telecentric lens 40 pass through the corresponding openings O in sequence and vertically. Comparing FIG1 with FIG2 , the laser beam that changes its path for the first time in FIG1 passes through the opening O at the lower left, and the laser beam that changes its path for the first time in FIG2 then passes through the opening O at the lower middle, and then the laser beam that changes its path for the first time in the next wave passes through the opening O at the lower right. Finally, the last wave of laser beams that change their path for the first time will pass through the opening O in the upper right corner, as shown in FIG3 (the figure shows that the laser thermal processing system 1 performs thermal processing on the object at the last position P9 on the work plane).

The second telecentric lens 60 and the first telecentric lens 40 are respectively disposed on both sides of the mask 50. After the laser beams that change the path for the first time travel the second straight distance F2, they change the path for the second time after passing through the second telecentric lens 60, and deviate to the focal direction of the second telecentric lens 60. The second straight distance F2 is the distance between the second telecentric lens 60 and the mask 50, and its length only needs to meet the convenience of work, and the present invention is not limited. In order to achieve the purpose of the second change of path, the present invention arranges the first telecentric lens 40 and the second telecentric lens 60 in opposite directions, and the image lens ends of the two face each other. As shown in Figures 1 and 3, the laser beam that changes its path for the second time is emitted toward the focal direction of the second telecentric lens 60 in the direction of the optical axis. In Figure 2, the laser beam that changes its path for the second time continues to be emitted toward the focal point of the second telecentric lens 60 along the direction of the optical axis.

The third telecentric lens 70 and the second telecentric lens 60 are disposed on the same side of the mask 50 but farther away. After passing through the third telecentric lens 70, the laser beams that change the paths for the second time change the paths for the third time to be parallel to each other and to the optical axis of the third telecentric lens 70, and are sequentially imaged vertically on the working plane for thermal processing. In order to achieve the purpose of changing the paths for the third time to be parallel to each other, the second telecentric lens 60 and the third telecentric lens 70 are placed in opposite directions in the present invention. In addition, in order to allow the laser beams that change the path for the second time to effectively pass through the third telecentric lens 70 to change the path, the interval between the second telecentric lens 60 and the third telecentric lens 70 needs to be specific: the distance between the opposite sides of the second telecentric lens 60 and the third telecentric lens 70 is the sum of the working distances of the two. Since the telecentric lens is a combination of multiple lenses, the working distance is the distance from the front surface of the object side lens to the object being photographed. The working distance of the second telecentric lens 60 is the second working distance D2, the working distance of the third telecentric lens 70 is the third working distance D3, and the distance between the second telecentric lens 60 and the third telecentric lens 70 is the second working distance D2 plus the third working distance D3. As shown in Figures 1 to 3, after the laser beam with the third telecentric lens 70 changes its path for the third time, it passes through a third straight distance F3 and vertically heat-processes the object 2 on the working plane, and performs 9 times in sequence from the first position P1 to the last position P9.

In this embodiment, the first telecentric lens 40, the second telecentric lens 60 and the third telecentric lens 70 are telecentric lenses of the same specifications, and the second working distance D2 is the same as the third working distance D3. In practice, all three can be different, or two of them can be the same and different from the other. It should be noted that the magnification of the second telecentric lens 60 and the third telecentric lens 70 can be different, thereby magnifying or reducing the ratio of the image of each laser beam on the working plane after passing through the corresponding opening O to the area of the opening. For example, the magnification of the third telecentric lens 70 is higher than that of the second telecentric lens 60, and the ratio of each image of the laser beam on the working plane to the area of the corresponding opening O will be greater than 1.

According to the present invention, due to optical imaging through the mask, the energy density distribution of the laser beam (on the same cross section) will be more uniform, and there will be no Gaussian energy concentration phenomenon. In comparison, the energy density distribution of the laser beam passing through any opening O plane will be more uneven than the energy density distribution of the same laser beam irradiated on the working plane. In order to better explain this, an experimental example and a comparative example are used below to illustrate.

The experimental example and the comparative example are all conducted using the equipment architecture in FIG1 . The laser light source 10 , the reflector 20 and the actuator 30 are integrated in a laser oscillator of model intelliSCAN, produced by SCANLAB. The three telecentric lenses used are telecentric lenses of model 4401-509-000-21, produced by LINOS. The mask 50 is a metal-coated quartz mask. See FIG4 , which shows the position and shape of the openings of the mask 50 used. The mask 50 is provided with five openings: a first opening O1, a second opening O2, a third opening O3, a fourth opening O4 and a fifth opening O5. The first opening O1 is located in the center, and the second opening O2, the third opening O3, the fourth opening O4 and the fifth opening O5 are equidistantly located at the upper right, upper left, lower left and lower right of the first opening O1. The distance L in Figure 5 is 2.5mm. The width of each opening is 20μm±0.5μm, and the height is 35μm±0.5μm. Through optical imaging, the accuracy of the laser irradiation position on the working plane can be less than 3μm. The experimental example captures the energy distribution image of each passing laser beam on the working plane, and the comparative example captures the energy distribution image of each passing laser beam at each opening (reference plane). The image of the comparative example is captured first, and the image of the experimental example is captured later.

The experimental results are shown in Figures 5 to 9, which respectively compare the energy distribution images of the same laser beam passing through the reference plane and the working plane. Take Figure 5 as an example. The energy distribution image of the first opening O1 on the reference plane is a pattern of multiple concentric circles, with the energy of the innermost red circle being the largest, and decreasing in sequence to the outer yellow ring, green ring, blue ring, and gray ring. It can be seen that the cross-sections in both directions form a Gaussian distribution. However, the energy distribution image of the laser beam passing through the first opening O1 on the working plane is not a Gaussian distribution. The cross-sections in both directions form a platform area in the central part, and the energy distribution of the platform area is not completely consistent, but the distribution is more average than the Gaussian distribution. Therefore, the energy density distribution of the laser beam passing through any opening plane will be more uneven than the energy density distribution of the same laser beam irradiated on the working plane. The same is true for Figures 6 to 9. When applied to actual thermal processing operations, the energy per unit area can be uniformed to improve the process yield.

Although the present invention has been disclosed in the form of implementation as above, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of the patent application attached hereto.

1: Laser thermal processing system

2: Objects

10: Laser light source

20: Reflector

25: Actuator

30: Control unit

40: First telecentric lens

50:Mask

60: Second telecentric lens

70: Third telecentric lens

D2: Second working distance

D3: The third working distance

F1: First straight distance

F2: Second straight distance

F3: The third straight distance

O: Opening

P1: First position

Claims (7)

A laser heat processing system comprises: a laser light source, which emits several waves of laser beams in sequence; a reflector, towards which the laser beams are directed, and which is controlled to rotate to change the reflection direction of the laser beams; a first telecentric lens, after the reflected laser beams pass through the first telecentric lens, the paths of which are changed for the first time to be parallel to each other and parallel to the optical axis of the first telecentric lens; a mask, on which a plurality of openings are provided, and the laser beams that change their paths for the first time pass through the corresponding openings in sequence and vertically; a second telecentric lens, which is respectively arranged on both sides of the mask with the first telecentric lens, and the laser beams that change their paths for the first time pass through the second telecentric lens. The path is changed for the second time after the telecentric lens, and it is biased towards the focal direction of the second telecentric lens; and a third telecentric lens is arranged on the same side of the mask as the second telecentric lens but farther away. The laser beams that change the path for the second time change the path for the third time after passing through the third telecentric lens to be parallel to each other and parallel to the optical axis of the third telecentric lens, and are sequentially imaged vertically on a working plane for thermal processing, wherein the optical axes of the first telecentric lens, the second telecentric lens and the third telecentric lens substantially overlap, and the energy density distribution of the laser beam passing through any opening plane is more uneven than the energy density distribution of the same laser beam irradiated on the working plane. A laser thermal processing system as described in claim 1, wherein the distance between the opposite sides of the second telecentric lens and the third telecentric lens is the sum of the working distances of the two. A laser thermal processing system as described in claim 1, wherein the second telecentric lens and the third telecentric lens have different magnifications, thereby magnifying or reducing the ratio of the image of each laser beam on the working plane after passing through the corresponding opening to the area of the opening. The laser thermal processing system as described in claim 1, wherein the first telecentric lens and the second telecentric lens are arranged opposite to each other, and the second telecentric lens and the third telecentric lens are arranged opposite to each other. The laser thermal processing system as described in claim 1, wherein the reflective mirror is connected to an actuator and is controlled by the actuator to rotate in a certain direction. The laser thermal processing system as described in claim 5 further comprises a control unit connected to the laser light source and the actuator, controlling the laser light source to emit a laser beam, and rotating the angle of the reflective mirror through the actuator when the laser light source stops emitting a laser beam. A laser thermal processing system as described in claim 1, wherein the laser irradiation position accuracy on the working plane is less than 3μm.