JP7223368B2 - LASER JOINING METHOD AND LASER JOINING APPARATUS - Google Patents

Description

The present invention relates to a laser bonding method and a laser bonding apparatus, and more particularly to a laser bonding method and a laser bonding apparatus for irradiating two sheets of polymerized thermoplastic resins with a laser beam to bond the two.

Conventionally, Patent Document 1 is known as a technique for joining polymerized thermoplastic resins with a laser beam.
In the apparatus of Patent Document 1, two sheets of polymerized thermoplastic resin are irradiated with a laser beam from above, and the thermoplastic resin at the irradiation position of the laser beam is heated and melted, so that the upper and lower thermoplastic resins are melted. It is designed to weld resin.
Patent Document 2 is also known as a technique for welding by irradiating a laser beam from above onto a polymerized metal plate. In the welding device of Patent Document 2, first, the upper metal plate is irradiated with a laser beam to form a through hole, and then the lower metal plate is irradiated with the laser beam through the through hole. , to weld the upper and lower metal plates.

Japanese Patent No. 4216656 JP-A-58-97489

By the way, the apparatus disclosed in Patent Document 1 has the following problems when bonding resin that does not transmit laser light. That is, when the object to be processed is, for example, a carbon fiber reinforced thermoplastic resin (CFRTP), it is not possible to directly irradiate the laser beam onto the joint surface between the polymerized upper and lower materials. Therefore, by irradiating the upper material with a laser beam, the upper material is heated, and the heat transfer heats and melts the joint surface, thereby welding the upper and lower materials.
However, since the thermal conductivity in the thickness direction (between the fibers) of the thermoplastic carbon fiber reinforced resin is poor, when the thickness of the upper material is, for example, 3 mm, the joint surface of the upper and lower materials is made of matrix resin (nylon In order to raise the temperature to about 240 degrees, which is the melting temperature of PA6), the temperature of laser irradiation to the upper material exceeds 500 degrees. As a result, the matrix resin is sublimated or burnt out, and the carbon fibers are exposed, resulting in a poor joint state after the completion of the joint. When the carbon fibers are exposed at the joints in this manner, there is a problem that the strength of the joints is extremely reduced.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a laser bonding apparatus and a method for efficiently performing laser bonding between thermoplastic resins and providing a high bonding strength after the completion of bonding.

In view of such circumstances, the first aspect of the present invention is a first and second material each made of a thermoplastic resin which are polymerized and irradiated with laser light to the first material. a first laser light irradiation step of forming a through hole penetrating the first material; and a laser light irradiation step toward the second material through the through hole formed by the first laser light irradiation step and a second laser beam irradiation step of melting the superposed portions of the two materials around the through hole to join the two materials,
In the first laser beam irradiation step and the second laser beam irradiation step, a laser beam having a cross-sectional intensity distribution of top hat mode is irradiated,
Further, in the first laser beam irradiation step, the laser beam is irradiated to the first material while the focus of the laser beam is positioned on the surface of the first material,
In the second laser light irradiation step, the focal point of the laser light is positioned at the center of the thickness direction of the first material in the through hole, or the thickness of the first material in the through hole It is characterized by irradiating the second material with a laser beam in a state where it is located closer to the surface side of the first material than the center in the vertical direction.
In a second aspect of the present invention, there is provided a processing stage for holding a workpiece obtained by polymerizing a first material and a second material each made of thermoplastic resin, and a laser beam is applied to the workpiece held by the processing stage. A laser beam irradiation device having a processing head for irradiation, a workpiece moving mechanism for relatively moving the processing stage and the processing head in a direction intersecting the optical axis direction of the laser beam, and a laser beam irradiated from the processing head. A focus moving mechanism for moving the focus of light relative to the work in the optical axis direction of the laser light, and a control device for controlling the operations of the work moving mechanism and the focus moving mechanism,
The control device includes a first laser beam irradiation operation of irradiating the first material with a laser beam to form a through-hole penetrating the first material; A second laser beam irradiation for irradiating a laser beam through the through-hole toward the second material to melt the superposed portions of both the materials around the through-hole and join the two materials together. and run the
The laser beam irradiation device is adapted to irradiate the workpiece with a laser beam having a top-hat mode cross-sectional intensity distribution,
Furthermore, in the first laser light irradiation operation, the laser light is irradiated with the laser light being focused on the surface of the first material,
In the second laser light irradiation operation, the focal point of the laser light is positioned at the center of the thickness direction of the first material in the through hole, or the thickness of the first material in the through hole is It is characterized by irradiating the second material with a laser beam in a state where it is located closer to the surface side of the first material than the center in the vertical direction.

According to such a configuration, as can be understood from comparison data after processing, which will be described later, it is possible to efficiently perform laser bonding between thermoplastic resins, and laser bonding with high strength at the joint after completion of bonding. A method and laser bonding apparatus can be provided.

The front view which shows one Example of this invention. It is a figure which shows the processing process by the laser bonding apparatus of FIG. 1, Fig.2 (a) shows the 1st laser beam irradiation process, and FIG.2(b) has shown the 2nd laser beam irradiation process. FIG. 4 is a diagram comparing cross-sectional intensity distributions of a Gaussian mode laser beam and a tophat mode laser beam; The figure which shows the photograph which image|photographed the joint location which welded with the laser beam of the top hat mode from upper direction. FIG. 4 is a view showing a photograph taken from above of a joint jointed with a Gaussian mode laser beam. The figure which compared the result after processing in a Gaussian mode and a top hat mode. The figure which compared the result after processing in a Gaussian mode and a top hat mode.

Hereinafter, the present invention will be described with reference to the illustrated embodiments. In FIGS. 1 and 2, 1 is a laser bonding apparatus. are irradiated to join them by laser.
Both the upper material 2 and the lower material 3 are strip-shaped thermoplastic resins having the same thickness and width. Therefore, in the present embodiment, in a state in which the upper material 2 and the lower material 3 are superimposed, a laser beam L is irradiated from above to a plurality of locations in the superimposed portion to join the two materials 2 and 3 together. It has become.

The laser bonding apparatus 1 of this embodiment includes a processing stage 7 for horizontally holding a workpiece W (an upper material 2 and a lower material 3) by an upper jig 5 and a lower jig 6, an X-direction table 9 and a Y-direction table. 10, a moving mechanism 12 for moving the processing stage 7 in the horizontal X direction and the Y direction; , an elevating mechanism 16 for elevating the processing head 13 to move the focal position of a condenser lens 15 incorporated therein, and a control device 17 for controlling the operation of these components.
The upper jig 5 is horizontally fixed to the processing stage 7 by a plurality of holding members 18, while the lower jig 6 maintains a horizontal state and can move up and down along the holding members 18. is always urged upward by a spring 19 of .
By sandwiching the upper material 2 and the lower material 3 in a partially overlapped state with the upper jig 5 and the lower jig 6 from above and below, the work W as a whole is horizontally held. there is The workpiece W can be reliably held between the upper jig 5 and the lower jig 6 by inserting a spacer having an appropriate thickness as required. In this embodiment, an upper material 2 as a first material is overlapped with a lower material 3 as a second material from above, and the upper material 2 and the lower material 3 constitute the work W. be.

The moving mechanism 12 is composed of an X-direction table 9 that moves in the X-direction on the horizontal plane and a Y-direction table 10 that moves in the Y-direction on the horizontal plane perpendicular to the X-direction. Mounted and horizontally supported. A controller 17 controls the operation of the driving sources (motors) of the X-direction table 9 and the Y-direction table 10 . The control device 17 controls the operation of the driving sources of the X-direction table 9 and the Y-direction table 10, so that the processing stage 7 can move in the horizontal X direction and in the Y direction orthogonal thereto. As a result, the workpiece W and the laser beam L are moved relative to each other in the horizontal plane, and the irradiation position of the laser beam L with respect to the workpiece W can be changed.

The laser irradiation device 14 includes a fiber laser oscillator 21 that oscillates a laser beam L having an oscillation wavelength of 1070 to 1080 nm, an optical fiber 22 that guides the laser beam L oscillated from the fiber laser oscillator 21 to the processing head 13, and an optical fiber A processing head 13 for irradiating a workpiece W with a laser beam L guided by 22 through a collimator lens 23 and a condenser lens 15 is provided.
The operation of the fiber laser oscillator 21 is controlled by the controller 17, and when the controller 17 operates the fiber laser oscillator 21, the laser light L is guided to the processing head 13 via the optical fiber 22. It's like
The processing head 13 is attached to the tip of a lifting arm 16A of the lifting mechanism 16 so as to face vertically downward. is designed to be raised and lowered. As a result, the position of the focal point f of the condenser lens 15 with respect to the work W can be adjusted to the optimum position when the work W is laser-bonded.
An end portion 22A of the optical fiber 22 is attached to the center of the upper surface of the casing of the processing head 13 so as to face vertically downward. placed at a distance.
As a result, the laser light L guided through the optical fiber 22 is irradiated downward from the end 22A, first adjusted into parallel light by the collimator lens 23, and then condensed by the condensing lens 15. After that, the work W on the lower side is irradiated.

Thus, this embodiment is characterized in that the two materials 2 and 3 are joined by irradiating the work W with the top hat mode laser beam L, and for this reason, the optical fiber 22 has a rectangular cross section. of optical fiber.
As a result, the cross-sectional shape of the irradiation spot of the laser beam L irradiated onto the workpiece W through the condenser lens 15 is square instead of circular. Also, the beam waist diameter of the laser light L is set to 150 to 170 μm. Thus, in this embodiment, the spot shape of the laser light L at the focal point f of the condenser lens 15 is a square top hat mode, and its cross-sectional intensity distribution is as shown in FIG. 3(b).
As the laser light L, a Gaussian mode is known in which the output gradually increases from the outer peripheral side to the center of the optical axis (see FIG. 3A).
However, in this embodiment, instead of the Gaussian mode laser beam L, the top hat mode laser beam L having substantially the same output from the center of the optical axis to the vicinity of the outer periphery is used for laser bonding.
FIG. 3 compares the Gaussian mode and the top hat mode in laser bonding (second laser beam irradiation step S2, second laser beam irradiation operation, which will be described later). FIG. FIG. 3(b) shows the top hat mode cross-sectional strength distribution. As described above, in this embodiment, the top-hat mode with a square cross section is used. is shown.
In the top hat mode shown in FIG. 3B, the beam intensity is uniform over substantially the entire irradiation area of the laser beam L, so that the vaporization threshold value P1 and the melting threshold value P2 are obtained over substantially the entire irradiation area. The workpiece W can be heated with a beam intensity between . Therefore, in the top hat mode, it is possible to melt substantially the entire irradiated area.
On the other hand, in the case of the Gaussian mode shown in FIG. As a result, the resin/fiber in the corresponding portion of the workpiece W disappears. Therefore, only the region indicated by the black ring becomes the melting range and becomes the joining point. As a result, the strength of the joined portion after the completion of the joining of the workpieces W (the upper material 2 and the lower material 3) is reduced. In this Gauss mode, if the center side area is set to the melting range, the annular outer peripheral portion will deviate from the melting range. will do.
On the other hand, as shown in FIG. 3(b), joining the work W in the top hat mode can widen the melting range for forming a suitable melting state (portion indicated by a black circle). Therefore, it is possible to increase the strength of the joint after the completion of the joining. In addition, since the laser beam L can be irradiated to the work W with a beam intensity higher than that of the Gaussian mode while the beam intensity is uniform, the necessary energy can be supplied in a short time, and the joining process can be performed in a short time. can be done. For this reason, in this embodiment, the top hat mode laser beam L shown in FIG. I am trying to do it.

In the above configuration, the workpiece W is laser-bonded in the following manner.
First, an operator clamps the workpiece W (the upper material 2 and the lower material 3) between the upper jig 5 and the lower jig 6 to hold the upper material 2 and the lower material 3 on the processing stage 7. .
After that, the control device 17 controls the operation of the moving mechanism 12, the lifting mechanism 16, and the laser irradiation device 14, and the joining process of the upper material 2 and the lower material 3 as the work W is performed as follows. .
That is, after this, the X-direction table 9 and the Y-direction table 10 of the moving mechanism 12 are horizontally moved by a required amount and then stopped, so that the laser beam L is first irradiated to the superimposed portion of the two materials 2 and 3. The point where the light is drawn stops below the axial center of the condensing lens 15 (see FIG. 1). After that, the machining head 13 is moved up and down by the required amount via the lifting arm 16A and then stopped. As a result, the height position of the focal point f of the condenser lens 15 matches the height of the upper surface (surface) 2A of the upper material 2 (see FIG. 2(a)).
After that, a laser beam L is oscillated from the fiber laser oscillator 21. The laser beam L is guided to the processing head 13 via the optical fiber 22, and then transmitted through the collimator lens 23 from the end portion 22A. After being adjusted to light, the light is condensed by the condensing lens 15 and irradiated onto the upper material 2 .
The processing conditions at this time are, for example, the plate thickness of both materials 2 and 3 is 2 mm, the number of shots is 1, the oscillation output is 1800 W, and the pulse width is 1.5 to 2.0 msec (0.0015 to 0.002 sec). and Here, as described above, the laser beam L is a top-hat mode laser beam L having a rectangular cross section. Since P1 is exceeded, the through holes 2B are formed in the upper material 2 in a short period of time. In this way, first, through-holes 2B in the vertical direction are bored in the upper material 2 (see FIG. 2(a)).
Since the lower end 2Ba of the through hole 2B is closed by the upper surface 3A of the lower material 3, the through hole 2B is a blind hole. The through hole 2B has a tapered shape with a narrower lower end 2Ba. Specifically, if the beam waist diameter at the focal point f is between 150 and 170 microns, the diameter of the upper opening of the through hole 2B is about 200 microns, and the diameter of the lower opening is about 100 microns.
In the present embodiment, the step of irradiating the upper material 2 with the top hat mode laser beam L and drilling the through hole 2B in it is the first laser beam irradiation step S1 and the first laser beam irradiation. It is working.

After that, the working head 13 is lowered by a predetermined amount by the lifting arm 16A and stopped there. Specifically, the height of the focal point f of the condensing lens 15 is positioned at the height of substantially the center of the through hole 2B in the vertical direction, or at a height above the center. That is, the focal point f is positioned at the center in the thickness direction of the upper material 2 in the through hole 2B, or at a height position shifted to the surface 2A side (upper side) therefrom. Positioning the focal point f at the center in the thickness direction also includes the case where the focal point f deviates vertically along the optical axis of the laser beam L from the perfect center position by about 0.1 mm. In the following description, the term "substantially center" is used to include this deviation. Further, the focal point f may be positioned further upward (on the condenser lens 15 side) so as to be positioned outside of the through hole 2B instead of inside.
After that, the laser beam L is again irradiated from above toward the lower material 3 through the through hole 2B (see FIG. 2(b)). As a result, the lower end 2Ba of the through hole 2B, the lower surface 2C of the upper material 2 and the upper surface 3A of the lower material 3, which are the periphery thereof, are melted to form a joint. The irradiation of the laser beam L to the workpiece W for the second time is the second laser beam irradiation step S2 and the second laser beam irradiation operation.
In the second laser light irradiation step S2, the focal point f of the condensing lens 15 is positioned substantially in the vertical center of the through-hole 2B or above it for the following reasons. In other words, if the position of the focal point f is brought closer to the lower material 3 than this, the skirt of the laser beam L will be absorbed by the upper material 2, so the formation of the through hole 2B as a pilot hole is meaningless. . On the contrary, if the position of the focal point f is too far from the lower material 3, the irradiation spot area on the lower surface 2C and the upper surface 3A, which are the surfaces to be bonded, is reduced, and the energy density is lowered, resulting in a decrease in the suitable bonding area. melting will not occur.
Therefore, in this embodiment, the focus f is positioned at or above the height of the center of the through hole 2B in the vertical direction, and the laser light L is again irradiated toward the upper material 2 and the lower material 3. (see FIG. 2(b)). The processing conditions at this time are as follows: the number of shots is 1, the oscillation output is 100 W, and the pulse width is 0.15 sec.
As a result, the lower end 2Ba of the through-hole 2B and the lower surface 2C of the upper material 2 and the upper surface 3A of the lower material 3 around the lower end 2Ba are melted and joined to form a joint.
As described above, in this embodiment, the second laser irradiation step S2 is performed after the first laser irradiation step S1 for the first joint portion to join the first joint portion.
After that, by moving the processing stage 7 in the horizontal direction by the moving mechanism 12 and lifting the processing head 13 by the lifting arm 16A, dozens of overlapping portions of the materials 2 and 3 are to be joined, and the above-mentioned first A laser beam irradiation step S1 and a second laser beam irradiation step S2 are performed to bond these dozens of locations. As a result, the overlapping portions of the upper material 2 and the lower material 3 are laser-bonded.

As described above, in the present embodiment, the first laser beam irradiation step S1 and the second laser beam irradiation step S2 are performed with the top hat mode laser beam L having a rectangular cross section to perform the work W (both materials 2, 3) is laser-bonded.
FIGS. 4 and 5 are photographs taken with a camera of the state of the joint after the completion of joining in the case where the work W is joined by the present embodiment and the case where the work W is joined in the Gaussian mode. In both modes, the machining conditions are an oscillation output of 100 W and a pulse width of 0.15 sec in the top hat mode, and an oscillation output of 25 W and a pulse width of 0.6 sec in the Gauss mode. In both cases, the plate thickness is 2 mm and the number of shots is 1.
When processing with a Gaussian mode laser beam was performed under the same processing conditions as processing with a top hat mode laser beam, the resin/fibers in the workpiece W were remarkably evaporated, and the bonding range was narrow, making bonding itself impossible. Therefore, the total energy is set to 15 J in both modes (0.15 sec x 100 W x = 15 J (W s) in top hat mode, 0.6 sec x 25 W = 15 J (W s) in Gauss mode). By matching the processing conditions, the comparison was made in a state in which resin/fiber evaporation was suppressed even in Gaussian mode bonding.
In both FIGS. 4 and 5, the upper material 2 and the lower material 3 after bonding are peeled off, and the bonded portion (upper surface 3A) of the lower material 3 is photographed from above with a camera.
FIG. 4 shows the case of this embodiment using top hat mode laser light, and FIG. 5 shows the case of joining the upper material and the lower material with Gauss mode laser light.
As is clear from the photographs of FIGS. 4 and 5, in the Gaussian mode processing shown in FIG. 5, carbonization progresses to the vicinity of the position corresponding to the through hole 2B of the upper material 2, and the material is blackened. This carbonized portion is a portion that is not joined, and since the fibers are also broken, the strength of the joined portion is reduced accordingly.
On the other hand, in the top hat mode processing (this embodiment) shown in FIG. 4, the portion corresponding to the through hole 2B of the upper material 2 is not carbonized and is white. In other words, they are melted without being carbonized, and are reliably joined there.
As is clear from the photographs of FIGS. 4 and 5, the strength of the joint is higher in the top hat mode processing (this example) shown in FIG. 4 than in the Gauss mode processing shown in FIG. It can be understood.

Further, FIGS. 6 and 7 show the results of comparison of the tensile shear strength, the total laser irradiation time, etc., in the joining processes in each of the above modes. The processing conditions are those for the most suitable joining processing in each mode, which are shown in FIG. Since the melted area per through-hole is larger in the top-hat mode (this embodiment), the number of through-holes is smaller than in the Gauss mode. In other words, the number of irradiation points (joint points) of the laser light L is significantly smaller in the case of the top hat mode (this embodiment) than in the case of the Gauss mode. As a result, in the top hat mode (this example), the tensile shear strength was increased by 18% and the processing time was shortened to 1/4 as compared to the case of the Gauss mode.
Further, FIG. 7 shows a comparison of the processing results in the Gauss mode and the top hat mode under the condition that the same tensile shear strength is obtained after the completion of joining. Even in this case, the top hat mode (this example) has a 278% higher tensile shear strength per joint and an 82% shorter processing time than the Gaussian mode.

As can be understood from the comparison data after processing in both modes shown in FIGS. 3 can be efficiently performed, and the effect of increasing the strength of the joint after the completion of the joining can be obtained.

In the above embodiment, the upper material 2 and the lower material 3 constituting the workpiece W are assumed to be thermoplastic resin, but carbon fiber reinforced thermoplastic resin (CFRTP) can also be processed by the laser bonding apparatus 1. Of course.
As a combination of the upper material 2 (first material) and the lower material 3 (second material) to be processed by the laser bonding apparatus 1, the following combinations (1) to (4) may be used. .
(1) Upper material: laser-impermeable (colored) thermoplastic resin Lower material: laser-impermeable (colored) thermoplastic resin (2) Upper material: fiber-reinforced thermoplastic resin Lower material: laser-impermeable (colored) ) thermoplastic resin (3) upper material: laser-impermeable (colored) thermoplastic resin lower material: fiber reinforced thermoplastic resin (4) upper material: fiber reinforced thermoplastic resin lower material: fiber reinforced thermoplastic resin In the above embodiment, the position of the focal point f of the condensing lens 15 is changed by elevating the processing head 13 by the elevating mechanism 16, but the processing head 13 itself is fixed and the condensing lens incorporated therein 15 may be moved up and down to change the position of the focal point f.
In the above-described embodiment, the optical fiber 22 having a square cross section is used to form the top hat mode laser beam. A shaper may be used to form the top-hat mode laser light L. FIG.
Furthermore, in the above embodiment, the upper material 2 and the lower material 3 are superimposed one on the other, and the laser beam is irradiated from above. It is also possible to employ a configuration in which the laser beam L is irradiated to the work W from the lateral direction in a state in which the overlapping surfaces of the two are in the vertical direction.

DESCRIPTION OF SYMBOLS 1... Laser joining apparatus W... Work 2... Upper side material (1st material) 2B... Through-hole 3... Lower side material (2nd material) 12... Movement mechanism (work movement mechanism)
13.. Processing head 14.. Laser irradiation device 15.. Condensing lens 16.. Elevating mechanism (focus moving mechanism)
17.. Control device L.. Laser beam S1.. First laser beam irradiation step S2.. Second laser beam irradiation step

Claims (2)

In a state in which a first material and a second material each made of a thermoplastic resin are polymerized, the first material is irradiated with a laser beam to form a through hole penetrating the first material. A laser beam irradiation step, and a laser beam is irradiated toward the second material through the through hole formed in the first laser beam irradiation step to polymerize both the materials forming the periphery of the through hole. A second laser beam irradiation step of melting the part and joining both materials,
In the first laser beam irradiation step and the second laser beam irradiation step, a laser beam having a cross-sectional intensity distribution of top hat mode is irradiated,
Further, in the first laser beam irradiation step, the laser beam is irradiated to the first material while the focus of the laser beam is positioned on the surface of the first material,
In the second laser light irradiation step, the focal point of the laser light is positioned at the center of the thickness direction of the first material in the through hole, or the thickness of the first material in the through hole A laser bonding method, comprising irradiating a laser beam toward the second material while the second material is positioned closer to the surface of the first material than the center in the longitudinal direction. Laser light irradiation having a processing stage for holding a workpiece obtained by polymerizing a first material and a second material each made of a thermoplastic resin, and a processing head for irradiating a laser beam to the workpiece held by the processing stage a workpiece moving mechanism for relatively moving the apparatus, the machining stage and the machining head in a direction intersecting the optical axis direction of the laser beam; and a focus of the laser beam emitted from the machining head to the workpiece. Equipped with a focus movement mechanism that relatively moves in the optical axis direction of the laser beam, and a control device that controls the operation of the work movement mechanism and the focus movement mechanism,
The control device includes a first laser beam irradiation operation of irradiating the first material with a laser beam to form a through-hole penetrating the first material; A second laser beam irradiation for irradiating a laser beam through the through-hole toward the second material to melt the superposed portions of both the materials around the through-hole and join the two materials together. and run the
The laser beam irradiation device is adapted to irradiate the workpiece with a laser beam having a top-hat mode cross-sectional intensity distribution,
Furthermore, in the first laser light irradiation operation, the laser light is irradiated with the laser light being focused on the surface of the first material,
In the second laser light irradiation operation, the focal point of the laser light is positioned at the center of the thickness direction of the first material in the through hole, or the thickness of the first material in the through hole is A laser bonding apparatus that irradiates a laser beam toward the second material while the second material is positioned closer to the surface side of the first material than the center in the longitudinal direction.

Images