JP2016155319A - Laser resin deposition method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a processing state or processing quality of resin deposition, in a non-contact and non-destructive manner.SOLUTION: A laser resin deposition device comprises: a laser oscillation part 10 for oscillation outputting laser beam LB whose wavelength is 0.4-1.1 μm; a laser optical system 14 for collecting and radiating the laser beam LB to a workpiece (processed object) W mounted on a processing stage 12; a control part 16 for controlling respective parts in the device; and a monitor part 18 for monitoring the processing state or processing quality of the resin deposition in a non-contact and a non-destructive manner. A radiation thermometer 26 on the monitor part 18 receives a near infrared radiation NR whose wavelength is 1.8-2.5 μm radiated from a deposited part Wof the workpiece W during radiation of the laser beam LB on an optical axis of a condenser lens 22 on the laser optical system 14, and measures temperature of the deposited part Won the basis of light intensity of the near infrared radiation NR.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser resin welding method and apparatus for welding a light-transmitting resin and a light-absorbing resin with a laser.

  In recent years, a laser resin welding method using a laser as a heat source for welding has attracted attention as a method for bonding a light-transmitting resin and a light-absorbing resin without using an adhesive.

  In the laser resin welding method, a light-transmitting resin and a light-absorbing resin are overlapped, and a laser beam is focused and irradiated from the light-transmitting resin side to the vicinity of the contact interface between the two resins. If it does so, the laser beam which permeate | transmitted the light transmissive resin will be absorbed by the light absorptive resin, the light absorptive resin will generate | occur | produce and fuse | melt, the heat | fever will be transmitted to the light transmissive resin, and a light transmissive resin will also fuse | melt. Thus, a molten pool is formed in the vicinity of the contact interface between the two resins, and when irradiation with the laser beam stops, the molten pool solidifies and the two resins are welded.

  Generally, the light absorbing resin is a colored resin. There are two types of coloring materials: pigment-based absorbing dyes and dye-based absorbing dyes. For example, carbon black is used as a black pigment-based absorbing dye.

JP 2005-246692 A JP 2005-281522 A JP 2014-177051 A

  The laser resin welding method does not require an adhesive, and even compared to the vibration welding method and ultrasonic welding method, there is no generation of burrs, noise and dust, and local rapid heating and cooling causes heat to the surrounding area. It has advantages such as little impact.

  However, in the conventional laser resin welding method, the appearance of the product is beautiful, but since the welded part is hidden inside the product (resin boundary surface), quality control of the resin welding process is performed using a destructive inspection. . The technology to monitor the processing status or processing quality of non-contact and non-destructive resin welding has not been established.

  The present invention has been made in view of the problems of the prior art, and provides a laser resin welding method and a laser resin welding apparatus that can monitor the processing state or processing quality of resin welding in a non-contact / non-destructive manner. To do.

  In the laser resin welding method of the present invention, a first resin that transmits a laser beam having a wavelength in the range of 0.4 to 1.1 μm and a second resin that absorbs the laser beam are overlapped. And a second step of condensing and irradiating the laser beam from the first resin side via a condenser lens to a welded portion set at a contact interface between the first resin and the second resin. And receiving near-infrared rays having a wavelength in the range of 1.8 to 2.5 μm radiated from the welded portion on the optical axis of the condenser lens, and from the near-infrared light intensity, And a third step of measuring the temperature of the welded portion.

  In the laser resin welding apparatus of the present invention, a first resin that transmits a laser beam having a wavelength in the range of 0.4 to 1.1 μm and a second resin that absorbs the laser beam are overlapped and welded. A laser resin welding apparatus for oscillating and outputting the laser beam, and disposed on an optical path of the laser beam so as to face the first resin, and the laser beam from the laser oscillation unit Is disposed on the welded portion set at the contact interface between the first resin and the second resin, and is disposed on the optical axis of the condensing lens, and radiates from the welded portion. A radiation thermometer that receives near-infrared light having a wavelength in the range of 1.8 to 2.5 μm and measures the temperature of the welded part from the light intensity of the near-infrared light.

  In the laser resin welding method or apparatus of the present invention, when the laser beam is focused and irradiated on the welded portion of the workpiece (the first and second resins superimposed), the heat generated from the welded portion inside the workpiece. Infrared rays having light intensity corresponding to temperature are emitted in all directions. This infrared ray includes a near infrared ray having a measurement wavelength in the range of 1.8 to 2.5 μm. A part of the near infrared ray having a measurement wavelength radiated from the welded portion inside the workpiece is transmitted through the light-transmitting resin and enters the light receiving portion of the radiation thermometer through the condenser lens. The radiation thermometer measures the temperature of the welded part from the near-infrared light intensity of the measurement wavelength. Personnel involved in the field estimate or evaluate the welding condition (processing condition) of the welded part from the measured temperature of the welded part obtained from the radiation thermometer, and as a result, the welding strength after the weld pool solidifies (working quality) Can be estimated or evaluated.

  In a preferred embodiment of the present invention, BK7 is used for the glass material of the condenser lens. Further, the output of the laser beam is controlled by an on / off control method so that the measured temperature of the welded portion matches or approximates a predetermined reference temperature. Further, the radiation thermometer is arranged on the optical axis of the condenser lens so that the light receiving portion is located on the central axis of the condenser lens.

  According to the laser resin welding method or laser resin welding apparatus of the present invention, it is possible to monitor the processing status or processing quality of resin welding in a contact / non-destructive manner by the configuration and operation as described above. The quality and reliability of the welding process can be improved.

It is a figure which shows the whole structure of the laser resin welding apparatus in one Embodiment of this invention. It is a figure which shows the wavelength dependence of the absorption coefficient in typical resin. It is a figure which shows the correlation (characteristic curve) of the temperature of the heat generating body in the low temperature area | region when using the wavelength of infrared rays as a parameter, and the light intensity of the infrared rays radiated | emitted from this heat generating body. It is a figure which shows the correlation (characteristic curve) of the temperature of the heat generating body in the high temperature area | region when using the wavelength of infrared rays as a parameter, and the light intensity of the infrared rays radiated | emitted from this heat generating body. It is a figure which shows the wavelength dependence of the transmittance | permeability in BK7 and synthetic quartz. It is a figure which shows the principal part of the one modification in embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Apparatus Configuration in the Embodiment]

  In FIG. 1, the whole structure of the laser resin welding apparatus in one Embodiment of this invention is shown.

  As shown in FIG. 1, the laser resin welding apparatus includes a laser oscillation unit 10 that oscillates and outputs a laser beam LB having a wavelength suitable for resin welding, and a laser beam LB that is oscillated and output from the laser oscillation unit 10. The laser optical system 14 for irradiating the workpiece (workpiece) W on the machine 12, the control unit 16 for controlling each part in the apparatus, and the non-contact / non-destructive monitoring of the processing status or quality of the resin welding And a monitor unit 18 for doing so.

  The laser oscillation unit 10 includes a laser oscillation element or an oscillator that generates a laser beam LB having a wavelength within a range of 0.4 to 1.1 μm (400 to 1100 nm), and power for excitation to the laser oscillation element or the oscillator. And a laser power supply circuit to be supplied. As the laser oscillation element or oscillator, for example, a blue light emitting diode with an oscillation wavelength of 400 nm, a semiconductor laser with an oscillation wavelength of 900 to 980 nm, a YAG laser with an oscillation wavelength of 1064 nm, a fiber laser with an oscillation wavelength of 1030 to 1070 nm, or the like can be used.

  The laser optical system 14 includes a vent mirror 20 for turning the laser beam LB from the laser oscillation unit 10 toward the workpiece W on the processing stage 12 at a predetermined angle, and a laser between the vent mirror 20 and the workpiece W. And a condenser lens 22 disposed on the optical path. The bent mirror 20 is, for example, a dichroic mirror, and has a high reflectivity with respect to a wavelength within a range of 0.4 to 1.1 μm and a high transmittance with respect to a wavelength within a range of 1.8 to 2.5 μm. It is coated with a film showing the property.

  As another example, a wavelength selective filter having the same function can be used for the bent mirror 20 instead of the dichroic mirror. Further, as the bent mirror 20, a mirror is used which is coated with a film showing high reflectivity only for wavelengths within the range of 0.4 to 1.1 μm and a film that transmits all wavelengths outside the range. In addition, an optical filter that selectively transmits only a wavelength within a range of 1.8 to 2.5 μm is also possible between the mirror and a monitor unit 18 (radiation thermometer 26) described later.

Condensing lens 22, parallel to faces the working stages 12, above the stage 12 side bent mirror 20 (vertically downwards) to the folded laser beam LB to the workpiece W moderate so that is focused on the welded portion W _TS Arranged at the height position.

  In this embodiment, BK7 is used for the base material or glass material of the vent mirror 20 and the condenser lens 22. BK7 is not only inexpensive as a glass material, but also has a more stable transmittance in the wavelength region of 1.8 to 2.5 μm than synthetic quartz as will be described later.

  The control unit 16 is preferably configured to include a microcomputer, and stores control programs, condition set values, conversion tables, tables, and the like necessary for carrying out the laser resin welding method in this embodiment in an internal or external memory (FIG. (Not shown).

The workpiece W is composed of a light-transmitting resin TP that is transmissive to the wavelength of the laser beam LB (within a range of 0.4 to 1.1 μm) and an absorptive light-absorbing resin AP. Form. As illustrated, the workpiece W is disposed on the stage 12 with the light-transmitting resin TP superimposed on the light-absorbing resin AP (with the light-transmitting resin TP facing the condenser lens 22). The welded portion W _TS of the workpiece W is set at an arbitrary position in the plate surface direction, a thickness direction both resins TP, is set on the contact surface and its vicinity of the AP. Preferably, a pressurizing device (not shown) that applies a pressing force in the thickness direction to both resins TP and AP during irradiation with the laser beam LB is used.

  In general, the light-transmitting resin TP is uncolored and the light-absorbing resin AP is colored. However, the light absorbing resin AP may be colored or the light absorbing resin TP may not be colored depending on the coloring material or filler.

The monitor unit 18 has a radiation thermometer 26 as a tool for monitoring the processing status or quality of laser resin welding in a non-contact / non-destructive manner. The radiation thermometer 26, by receiving the near infrared NIR having a wavelength in the range of 1.8~2.5μm emitted from the welded portion W _TS of the workpiece W during the irradiation of the laser beam LB, the proximal It is configured to measure the temperature of the welded portion W _TS from the light intensity of the infrared NIR.

More specifically, the radiation thermometer 26 is based on a photoelectric conversion element or a near-infrared sensor (photodiode) having sensitivity to a wavelength in the range of 1.8 to 2.5 μm and an output signal of the photoelectric conversion element. has a measured that operation circuit or a table or the like determining the temperature of the welded portion W _TS, is disposed on the optical axis of the condenser lens 22 so that it can be accurately and stably to receive near infrared NIR from the workpiece W The

In the configuration example of FIG. 1, the radiation thermometer 26 is disposed directly above the condenser lens 22 such that the light receiving portion 26 a is located on the central axis of the condenser lens 22. Inside or in front of the light receiving portion 26a, radiated light (especially near-infrared NIR having a wavelength in the range of 1.8 to 2.5 μm) from the workpiece W passing through the condenser lens 22 and the vent mirror 20 is converted into a photoelectric conversion element. A condensing (incident) lens 28 for condensing and entering the light is placed on the glass material, and preferably BK7 is also used for the glass material of the condensing (incident) lens 28.

[Operation in Embodiment]

In the laser resin welding apparatus having the above-described configuration, when the laser resin welding process is performed on the workpiece W on the stage 12, the welding portion W _TS of the workpiece W is placed on the condenser lens 22 in the horizontal direction (XY direction). positioned on the optical axis, after performing the focus of the condensing lens 22 is focusing to be located in the vicinity of the welded portion W _TS of the workpiece W (the height adjustment) in the vertical direction (Z-direction), the control unit 16 Under the control, the laser oscillation unit 10 performs a laser oscillation operation.

The laser beam LB oscillated and output from the laser oscillating unit 10 with a desired laser output is incident on the workpiece W on the stage 12 through the vent mirror 20 and the condenser lens 22 of the laser optical system 14. In the workpiece W, the laser beam LB passes through the upper light-transmitting resin TP, enters the lower light-absorbing resin AP, and is absorbed. The light absorbing resin AP generates heat and melts by absorbing the laser beam LB. Then, the heat generated by the light absorbing resin AP is transmitted to the light transmitting resin TP, and the light transmitting resin TP is also melted. Thus, both resins TP, the molten pool is formed in the vicinity of the contact interface of the AP that is the welded portion W _TS. When the oscillation output or irradiation of the laser beam LB stops after a certain time has elapsed, the molten pool is solidified. Thus, the workpiece W both resin TP, AP is welded by the welded portion W _TS.

When the laser beam LB onto the welded portion W _TS of the workpiece W as described above is condensed and irradiated is infrared having a light intensity corresponding to the heating temperature from the welded portion W _TS is radiated in all directions. The infrared spectrum covers a wide range of approximately 1 to 10 μm, and a near infrared NIR having a measurement wavelength in the range of 1.8 to 2.5 μm is included therein. Then, the near infrared NIR measurement wavelength emitted from the welded portion W _TS internal workpiece W vertically upward (1.8~2.5μm) is transmitted through the light transmitting resin TP, a condenser lens 22, the vent The light enters the light receiving portion 26 a of the radiation thermometer 26 through the mirror 20 and the condenser lens 28.

When the radiation thermometer 26 receives near-infrared NIR having a measurement wavelength, it calculates a light intensity measurement value representing the light intensity of the near-infrared NIR by calculation based on a photoelectric conversion signal obtained from the photoelectric conversion element. Further, the light intensity measurements of the near infrared NIR, temperature tables or predetermined conversion of the welded portion W _TS of the workpiece W which is emitting source in the near infrared NIR (operation) determined by the processing. Temperature measurements of the welded portion W _TS obtained from the radiation thermometer 26 is received by the control unit 16, it is displayed on the display unit 24 as a monitor value representing the machining status or processing quality of the laser resin welding.

Field workers such official, from the work measuring temperatures is provided as monitoring information, to estimate or assess the penetration degree of the welded portion W _TS (machining status), and thus the welding strength after the molten pool has solidified (machining Quality) can be estimated or evaluated. Control unit 16, in addition to the display of the measured temperature of the welded portion W _TS, performs quality determination of the resin fusion bonded by comparing the measured temperature with a predetermined monitoring value or window, displays the result of the quality determination It can also be displayed on the part 24.

  Furthermore, the control unit 16 outputs the laser beam LB through the laser oscillation unit 10 so that the temperature measurement value obtained from the radiation thermometer 26 matches or approximates a preset reference value during the laser resin welding process. Can be controlled by an on / off control method. In general, a PID (proportional integral derivative) control system is used for this type of temperature control. However, in the PID control method, it is necessary to adjust the control amount or the operation amount according to the type and characteristics (particularly, heat capacity and laser light absorption characteristics) of the workpiece W. In that respect, the on / off control method does not require any adjustment even if the type and characteristics of the workpiece W change. In this embodiment, the quality and reliability of the laser resin welding process can be improved.

As described above, in this embodiment, in order to monitor the processing state or quality of laser resin welding in a non-contact / non-destructive manner, the radiation thermometer 26 is provided on the optical axis of the condenser lens 22, and the workpiece W temperature measured light intensity of the near infrared NIR, representative of the temperature of the light intensity measurements from the welded portion W _TS having a wavelength in the range of 1.8~2.5μm emitted from the welded portion W _TS of The measured value is obtained as a monitor value.

  Here, in this embodiment, the measurement wavelength is limited to the range of 1.8 to 2.5 μm based on the following reason.

First, as described above, during the laser beam irradiation, infrared spectrum from the welded portion W _TS inside the workpiece W is distributed in a wide range of about 1~10μm is emitted. However, the light intensity of the infrared rays emitted from the welded portion W _TS laser beam upon considerably lower compared to LB, is attenuated until most spectrum is absorbed by the light transmitting resin TP of unmeasurable levels. However, as shown in FIG. 2, many resins such as PS (polystyrene), PA (polyamide), PE (polyethylene), ABS resin, PP (polypropylene) are in the range of 1.8 to 2.5 μm (1800 to 2500 nm). It shows a low absorption coefficient for the inner wavelengths. Although omitted in FIG. 2, organic substances such as resins generally exhibit high absorptivity for wavelengths of 2.5 μm (2500 nm) or more. Note that the spectrum of FIG. 2 is normalized at 1300 nm.

Accordingly, the infrared rays measured by limiting the wavelength in the range of 1.8～2.5Myuemu, the infrared rays emitted from the welded portion W _TS internal work W out of the light transmitting resin TP intensity was measured with high sensitivity, it is possible to turn measures the temperature of the welded portion W _TS of the workpiece W with high accuracy.

Second, the radiation thermometer converts the intensity of received infrared light into the temperature of the radiation source based on a certain correlation. However, in the laser resin welding process of this kind, since the target welding portion W _TS of the workpiece W is melted in some unspecified profile, infrared light intensity or light quantity tends to vary emitted in a specific direction (vertically upward).

  On the other hand, as shown in FIG. 3, the correlation between the temperature of the heating element and the intensity of the infrared light emitted from the heating element varies depending on the wavelength of the infrared ray, and is 300 ° C., which is a processing temperature for general laser resin welding. In the following relatively low temperature range, the longer the wavelength is 1 μm, 2 μm, 3 μm, and 6 μm, the greater the change in temperature (the slope of the characteristic curve) with respect to the change in light intensity. In FIG. 3, the horizontal axis indicates the temperature of the heating element, and the vertical axis indicates the intensity of infrared light emitted from the heating element.

That is, the influence of variations in the infrared light intensity emitted from the welded portion W _TS of the workpiece W (the error of temperature measurements derived from correlation), the shorter wavelengths small and becomes larger as a longer wavelength. However, if the infrared wavelength for measurement is selected to be 1 μm or close to it, not only may there be a conflict (interference) with the wavelength of the laser beam LB for processing, but the absolute amount of light intensity (light quantity) will be significantly reduced. Therefore, in this embodiment, the measurement wavelength is set in the range of 1.8 to 2.5 μm.

  As shown in FIG. 4, in the high temperature region, particularly at about 650 ° C. or higher, the correlation between the infrared light intensity and the temperature is not so different depending on the wavelength. Also in FIG. 4, the horizontal axis indicates the temperature of the heating element, and the vertical axis indicates the intensity of infrared light emitted from the heating element.

  In this embodiment, the near-infrared NIR of the measurement wavelength emitted from the workpiece W as described above is used for the glass materials of the condenser lens 22, the vent mirror 20, and the condenser lens 28 that pass along the propagation to the radiation thermometer 26. It is also important to use BK7. That is, as shown in FIG. 5, in the wavelength region of 1.8 to 2.5 μm, the transmittance of synthetic quartz drops sharply around 2.2 μm, whereas the transmittance of BK7 only decreases monotonously. BK7 is more stable than synthetic quartz as a glass material that transmits near-infrared NIR of the measurement wavelength. Of course, BK7 is more advantageous than synthetic quartz in terms of cost.

However, in the wavelength region of 1.8 to 2.5 μm, as the wavelength increases, the transmittance of BK7 decreases monotonously as described above. Therefore, it is also preferable to lower the upper limit of the measurement wavelength, and for example, it may be in the range of 1.8 to 2.3 μm.

[Other Embodiments or Modifications]

In the above embodiment, the laser beam LB passes through the optical axis of the condensing lens 22, the welded portion W _TS of the workpiece W is set on the optical axis of the condensing lens 22. However, a configuration in which a galvano scanner or a three-dimensional scanner is mounted on the laser optical system 14 is also possible. The condensing lens 22 may be an fθ lens.

  Further, in the monitor unit 18, the radiation thermometer 26 only needs to receive the near-infrared NIR of the measurement wavelength on the optical axis of the condenser lens 28, and is not necessarily spatially coaxial with the condenser lens 22. For example, as shown in FIG. 6, a radiation thermometer 26 is arranged so that a folding mirror 30 is disposed right above the condenser lens 22 and near infrared NIR of a measurement wavelength folded in the horizontal direction by the folding mirror 30 is received. May be arranged sideways.

  As another example of the bent mirror 20, a wavelength selection filter having a similar function can be used instead of the dichroic mirror. Further, as the bent mirror 20, a mirror is used which is coated with a film showing high reflectivity only for wavelengths within the range of 0.4 to 1.1 μm and a film that transmits all wavelengths outside the range. May be. In this case, a wavelength within the range of 1.8 to 2.5 μm is selectively transmitted on the optical path between the vent mirror 20 and the radiation thermometer 26 of the monitor unit 18 or in the radiation thermometer 26. An optical filter may be provided.

  In the above embodiment, BK7 is used as the glass material of the optical parts 20, 22, and 28 that pass the near-infrared NIR of the measurement wavelength as described above, but it is also possible to use synthetic quartz for some or all of them. Further, anhydrous synthetic quartz may be used although the manufacturing cost increases.

  The form of laser resin welding in the present invention is not limited to sbot welding, and seam welding or the like is also possible.

DESCRIPTION OF SYMBOLS 10 Laser oscillation part 14 Laser optical system 16 Control part 18 Monitor part 20 Vent mirror (dichroic mirror)
22 Condensing lens 26 Radiation thermometer 28 Condensing (incident) lens W Workpiece (workpiece)
TP light-transmitting resin AP light-absorbing resin

Claims (7)

A first step of superimposing a first resin that transmits a laser beam having a wavelength in the range of 0.4 to 1.1 μm and a second resin that absorbs the laser beam;
A second step of condensing and irradiating the laser beam from the first resin side to the welded portion set at the contact interface between the first resin and the second resin via a condenser lens;
Near infrared rays having a wavelength in the range of 1.8 to 2.5 μm radiated from the welded portion are received on the optical axis of the condenser lens, and from the near infrared light intensity, A laser resin welding method comprising: a third step of measuring temperature.   The laser resin welding method according to claim 1, wherein the near infrared measurement wavelength in the third step is in a range of 1.8 to 2.3 μm.   The laser resin welding method according to claim 1 or 2, wherein a glass material of the condensing lens is BK7.   4. The method according to claim 1, further comprising a fourth step of controlling the output of the laser beam by an on / off control method so that a measured temperature of the welded portion matches or approximates a predetermined reference temperature. The laser resin welding method according to one item. A laser resin welding apparatus for laminating and welding a first resin that transmits a laser beam having a wavelength in the range of 0.4 to 1.1 μm and a second resin that absorbs the laser beam. ,
A laser oscillation unit for oscillating and outputting the laser beam;
The welding is arranged on the optical path of the laser beam so as to face the first resin, and the laser beam from the laser oscillation unit is set at a contact interface between the first resin and the second resin. A condensing lens for condensing the light,
A near infrared ray disposed on the optical axis of the condenser lens and having a wavelength in the range of 1.8 to 2.5 μm emitted from the welded portion is received, and the near infrared light intensity is received from the near infrared light intensity. A laser resin welding apparatus comprising: a radiation thermometer for measuring a temperature of a welded portion.   6. The laser resin according to claim 5, further comprising a control unit that controls the output of the laser beam by an on / off control method so that a measurement temperature obtained by the radiation thermometer matches or approximates a predetermined reference temperature. Welding equipment.   The laser resin welding apparatus according to claim 5 or 6, wherein the light receiving portion of the radiation thermometer is located on a central axis of the condenser lens.