JPH10216971A - Laser beam machine and machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate unnecessary laser beam machining due to a molten scattering matter resulting from laser beam machining even in machining while irradiating at least two times in a range including a machining position of a work with a laser beam. SOLUTION: When machining by irradiating at least two times with a laser beam, in irradiating a first laser beam, unnecessary laser beam irradiation due to a molten scattering matter is avoided by an action of a gate circuit 242, etc. In the laser beam irradiation after a second and thereafter, by a counter circuit 245, a selection circuit 243 and a delay circuit 244, etc., based on a trigger signal TG obtained at a first scanning time and an encoder pulse from an encoder 210, the position corresponding to the irradiated position of the first laser beam is irradiated with the laser beam after a second time and thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus and a laser processing method capable of processing a desired processing position at a high speed, for example, a laser processing apparatus and a laser processing method suitable for removing a dam bar of a semiconductor device. About.

[0002]

2. Description of the Related Art Processing using pulsed laser light (hereinafter referred to as pulsed laser light) includes cutting, drilling,
Processing methods such as welding are used in manufacturing processes in various fields such as machines, electronics, and semiconductor devices. The configuration of a conventional laser processing apparatus will be described with reference to FIGS.

As shown in FIG. 7, a conventional pulse laser processing apparatus includes a laser head 401, a processing optical system 402, a laser power supply 403, and a workpiece 41 as a workpiece.
XY table 411, laser head 401, and processing optical system 40 on which 0 is mounted and which can be moved in a horizontal plane (XY plane).
Z table 40 for moving 2 vertically (Z-axis direction)
4. A main controller 405 for automatically or manually controlling the movement of the XY table 411 in the horizontal plane, the movement of the Z table 404 in the vertical direction, and the oscillation of the pulse laser beam. The laser head 401 and the laser power supply 403 constitute a laser oscillator 400.

The laser power supply 403 comprises a laser controller (not shown), a stabilized power supply, a capacitor section, a switch section, and the like. According to the voltage value commanded by the laser controller, the supplied alternating current is converted into direct current by the stabilized power supply, supplied to the capacitor unit, and the electric charge accumulated in the capacitor unit is opened and closed by the switch unit via the switch unit at a predetermined opening and closing. The discharge is performed to an excitation lamp (not shown) of the laser head unit based on the timing. The opening and closing of the switch unit is performed in accordance with a trigger signal for instructing a pulse width and a pulse frequency from a laser controller. As described above, pulse laser light is emitted from the laser head 401.

The laser head 401 has a built-in beam shutter (not shown). The beam shutter is opened and closed to control the irradiation of the work 410 with pulsed laser light. That is, the beam shutter is opened when the workpiece 410 is processed, and the beam shutter is closed when the workpiece 410 is not processed. The opening and closing operation time of this beam shutter is about 100 to 300 msec,
The control is performed by the laser controller described above, but it is also possible to perform the control from the main controller 405 via the laser controller.

A case will be described in which, for example, a dam bar of an IC package is removed using the above-described pulse laser processing apparatus. FIG. 8A is a plan view of the IC package, and FIG. 8B is an enlarged view of a portion B in FIG. 8A. FIG.
As shown in (b), the dam bar 2 connects the pins (hereinafter, also referred to as leads) of the lead frame used for the IC, and plays a role of damming the resin at the time of molding the IC and reinforcing the pins of the lead frame. This is the part that is removed at the end of the manufacturing process. A processing procedure for removing the dam bar 2 with a pulsed laser beam is described in FIG.
Removal (cutting) of the point is completed, and then processing (removal) of point L
The following is an example of performing the above operation.

(1) The irradiation position of the pulse laser beam on the work 410 is moved from the point K to the point L (the direction of the X axis) in FIG. 8B by the XY table 411. (2) Positioning is performed at the point L, and the XY table 411 is stopped. (3) Open the beam shutter. (4) Irradiating the pulse laser beam to remove the dam bar at the point L. (5) Close the beam shutter.

By repeating the processing steps (1) to (5), the dam bars 2 on the four sides of the IC package shown in FIG. 8A are sequentially removed. At this time, XY
The movement and stop of the table and the opening and closing of the beam shutter are executed in accordance with a program previously input to the main controller 405. During this time, the pulsed laser light always oscillates in a pulse shape or oscillates in synchronization with the opening of the beam shutter, and these controls are performed by the above-described laser controller.

Conventional techniques relating to a laser processing apparatus or a laser processing method suitable for removing the dam bar as described above are described in, for example, JP-A-56-9090 and JP-A-4-41092. There are things. The former method described in Japanese Patent Application Laid-Open No. 56-9090 discloses a method in which a laser beam is oscillated uniformly in response to a change in a processing speed (moving speed of an XY table), and the latter is disclosed in Japanese Patent Application Laid-Open No. The apparatus described in Japanese Patent Application Laid-Open No. 4-41092 discloses a method of turning on / off a laser beam in accordance with a comparison result between a plurality of pieces of processing position information stored in advance and a movement amount of an XY table.
It controls OFF and irradiation timing.

Further, as a laser processing apparatus and a laser processing method capable of processing a desired processing position at a high speed not only when the processing positions are at equal intervals but also when the processing positions are not at equal intervals, Japanese Patent Laid-Open No. 6-142968 is disclosed. There is a thing of the description. In this prior art, a detecting means for detecting presence or absence of a workpiece near a processing position and generating a corresponding detection signal, a rectangular wave signal generating means for generating a rectangular wave signal based on the detection signal, There is disclosed a laser processing apparatus including control means for controlling oscillation of pulsed laser light so that the pulsed laser light is irradiated at a timing based on a wave signal.

[0011]

The size of the dam bar of the above IC package is about 0.1 to 0.3 mm in width and 0.1 mm in thickness.
Since it is about 15 mm, a single pulse of laser light can sufficiently remove the dam bar. Therefore, the time required for the actual processing corresponds to the time of the pulse width of the pulse laser light, and is about 0.1 to 1 msec. However, in the processing procedures (1) to (5) described above, the opening and closing operation time of the beam shutter is 200 to 600 msec.
The time required for removing one dam bar is about 1 sec depending on the time required to move one table, and the processing time is too long in consideration of the number of cut dam bars and the number of manufactured IC packages.

In general, in the case of an IC package, the pitch of pins (leads) is often the same. However, there is a manufacturing error of a lead frame, a distortion due to a temperature history when molding with a resin, and an external force due to handling. In some cases, the pitch is not always equal when the dam bar is removed. In the dam bar removing method described in the above (1) to (5), the location where the dam bar is to be removed is registered in the main controller in advance as a program, but in this method, the pins are not arranged at the same pitch. In the worst case where the manufacturing error and the deformation are accumulated and the error increases, there is a possibility that the lead frame portion to be left may be damaged.

When the conventional technique described in Japanese Patent Application Laid-Open No. 56-9090 is applied to the removal of dam bars, the pins are not arranged at equal pitches but irregularly arranged in order to uniformly irradiate the laser beam. When this happens, it cannot be handled, and the same problem as described above occurs. Further, when the conventional technique described in Japanese Patent Application Laid-Open No. 4-41092 is applied, only control according to a predetermined shape stored (assumed) in advance can be performed.
Again, it is not possible to cope with the case where the pins are arranged irregularly, and the same problem occurs.

Further, according to the prior art described in Japanese Patent Laid-Open No. 6-142968, a desired processing position can be processed at high speed not only when the processing positions are at equal intervals but also when they are not at equal intervals. Therefore, even if the pins are not arranged at regular pitches but are irregularly arranged, it is possible to cope with the removal of the dam bar to some extent. However, during laser processing, scattered molten matter (spatter) adheres to the lead surface.
When the conventional technology described in Japanese Patent No. 68 is applied to the removal of a dam bar, the reflected light of the detection light is scattered by the molten and scattered matter attached to the lead surface, and the amount of reflected light from the lead portion is reduced, as if the edge portion of the lead portion. Erroneous irradiation of the pulse laser beam for processing may be erroneously recognized as having passed through the slit portion, that is, having entered a slit portion having no lead. That is, when a rectangular wave signal is generated by the rectangular wave signal generating means based on the detection signal corresponding to the reflected light of the detection light, a change in the detection signal caused by the molten and scattered matter attached to the lead surface,
That is, there is no problem when the decrease in the level of the detection signal is larger than the threshold value for generating the rectangular wave signal, but when the decrease is smaller than the predetermined threshold value, the output rectangular wave signal is The pulse laser light is also oscillated (erroneously oscillated) by the erroneously detected rectangular wave signal because the erroneous detection occurs in synchronization with not only the edge portion but also the melted scattered object scattered on the lead surface. Would. Therefore, there is a problem that erroneous irradiation is performed on an erroneous position other than the predetermined laser processing position, and the laser processing is performed.

In response to such a problem, the present applicant has
Among the detection signals based on the reflected light of the detection light, the change in the detection signal due to the presence or absence of the workpiece near the processing position is excluded, while the change in the detection signal due to the melted scattered matter attached near the processing position during laser processing is excluded. Laser processing apparatus and laser processing method provided with erroneous detection prevention means for extracting only the laser beam (Japanese Patent Application No. 7-265401, filed on Oct. 1, 1995)
3) was invented and filed. According to this prior application, not only when the processing positions are at equal intervals but also when the processing positions are not at equal intervals, the desired processing position where the workpiece exists can be processed at a high speed, and the processing position caused by laser processing can be obtained. Unnecessary laser processing based on the melted splatters is eliminated.

However, it has been found that the prior invention has room for further improvement. Hereinafter, this will be described.

When the dam bar of the IC package is cut and removed, the dimension (length) of the dam bar is about 0.1 to 0.3 mm and the thickness is about 0.15 mm. Usually, the laser beam irradiation can sufficiently remove the laser beam. However, when the length of the dam bar is long, or when the thickness of the dam bar is large, it is necessary to irradiate the laser beam twice or more. For example, when the dam bar is long, the laser light is irradiated to two places, and when the dam bar is thick, the same position is irradiated with the laser light twice or more. In such a case, when applying laser light to two locations of the dam bar by applying the invention of the prior application, scanning is performed while detecting the presence or absence (arrangement state) of leads near the dam bar with detection light. The first laser light irradiation is performed based on the detected signal, and the second laser light irradiation is performed based on the same detection signal as above while changing the delay time during signal processing while scanning the same locus again. Just do it. At this time, the melted and scattered matter adheres to the lead portion by the first laser light irradiation, but at the time of the first scan, the laser processing based on the melted and scattered matter is avoided unnecessarily by the configuration of the above-mentioned prior application. However, during the second and subsequent scans, there is a possibility of erroneous detection due to the melted and scattered matter adhered in the first laser processing, and the erroneous detection causes erroneous irradiation to an incorrect position other than the predetermined laser processing position. There is a problem that the laser processing is performed.

An object of the present invention is to enable a high-speed processing of a desired processing position where a workpiece exists, not only when the processing positions are at equal intervals but also when the processing positions are not at equal intervals, and to apply laser light to the desired processing position. Laser processing in which laser processing is not performed unnecessarily based on the melted scattered matter generated by laser processing even when processing is performed by irradiating the area including the processing position of the workpiece twice or more. It is to provide an apparatus and a laser processing method.

[0019]

According to the present invention, there is provided a laser oscillator for oscillating a pulsed laser beam, and a processing optical system for guiding the laser beam to a processing position of a workpiece. And a transfer means for moving the workpiece and determining a processing position thereof, wherein the laser processing apparatus performs processing by irradiating laser light at least twice to a range including the processing position on the workpiece. A detection light source that generates detection light for detecting the presence or absence of a workpiece at the processing position; and a detection that detects reflected light of the detection light from the workpiece and generates a detection signal corresponding to the reflected light. Means for detecting, based on the presence or absence of a workpiece in the vicinity of the processing position, a change in the detection signal due to a melted splatter attached to the vicinity of the processing position during the laser processing among the detection signals. Erroneous detection prevention means for extracting only the signal change, and control of the oscillation of the laser light so that the processing position of the workpiece is irradiated with the first laser light based on a change in the detection signal extracted by the erroneous detection prevention means. Control means for measuring the first laser light irradiation position based on the detection signal, and storage means for measuring and storing the first laser light irradiation position based on the detection signal; and second and subsequent laser lights at a position corresponding to the stored first laser light irradiation position. And control means for controlling the oscillation of the laser light so that the laser beam is irradiated.

Further, according to the present invention, a processing position is determined by moving a workpiece, a pulsed laser beam is generated from a laser oscillator, and the laser beam is irradiated at least twice to a range including the processing position. In the laser processing method of processing the workpiece by performing the process, the detection light for detecting the presence or absence of the workpiece in the vicinity of the processing position is irradiated to the vicinity of the processing position, and the reflected light of the detection light from the vicinity of the processing position Of the laser processing, except for the change in light due to the melted scattered matter attached to the vicinity of the processing position, and detect only the change in the reflected light of the detection light based on the presence or absence of the workpiece in the vicinity of the processing position to respond A laser signal oscillation is controlled so that the processing position of the workpiece is irradiated with the first laser light based on a change in the detection signal. Measuring and storing the first laser light irradiation position, and further controlling the oscillation of the laser light so that the position corresponding to the stored first laser light irradiation position is irradiated with the second or later laser light. Is provided.

In the present invention configured as described above, at the time of scanning for the first laser light irradiation, detection light for detecting the presence or absence of a workpiece near the processing position is generated from the detection light source. Detecting means detects light from the workpiece and generates a detection signal corresponding to the light. At this time,
The detection signal generated by the detection means, in addition to the change according to the presence or absence of the workpiece, also includes a change caused by a molten scattered object (spatter) scattered from the processing portion during laser processing and attached near the processing position. become. Therefore, the erroneous detection preventing means excludes only the detection signal based on the presence / absence of the workpiece in the vicinity of the processing position, excluding the change of the detection signal due to the melted scattered matter attached near the processing position during the laser processing. By taking it out and inputting it to the control means, the control means controls the first oscillation of the laser beam based only on the detection signal based on the presence or absence of the work, and obtains a desired laser light according to information on the surface of the work. The processing is performed by reliably irradiating the processing position with the first laser light.

The following processing is performed for the second and subsequent laser beam irradiations. First, based on a detection signal obtained at the time of scanning for the first laser light irradiation, the first laser light irradiation position is measured and stored by the storage means. For example, when removing the dam bar of the IC package, an encoder or the like is attached to the transport means, and the number of pulses corresponding to the movement amount output from the encoder is counted.
The count number (representing the arrangement state of the leads near the dam bar) corresponding to the aforementioned detection signal is accurately recorded. And
The transport unit is moved again along the same locus as the first scan to perform the second scan, and the second laser beam irradiation is performed based on the laser beam irradiation position stored in the storage unit. At this time, the oscillation of the laser light is controlled so that the position corresponding to the first laser light irradiation position is irradiated with the second and subsequent laser beams. Further, in the case of performing the third and subsequent scans and laser beam irradiation, it is possible to perform the scan in the same manner as in the second scan. Thereby, based on the accurate position information acquired and stored at the time of the first scan, the second and subsequent laser light irradiations can be performed at an accurate position corresponding to the first laser light irradiation position.

As described above, even when processing is performed by irradiating the laser beam twice or more to the range including the processing position of the workpiece, the processing is not performed based on the molten and scattered material generated by the laser processing. The need for laser processing is eliminated. In addition, since the laser beam is applied to a position separated by a certain distance from the position where the information on the presence or absence of the workpiece is detected,
Not only when the processing positions are at equal intervals but also when the processing positions are not at equal intervals, a desired position to be cut is processed reliably and at high speed in accordance with the information on the presence or absence of the workpiece.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a laser processing apparatus and a laser processing method according to the present invention will be described with reference to FIGS. However, in the following, a case will be described in which a dam bar portion of an IC package having pins at regular intervals is removed. However, here, for each dam bar,
It is assumed that two laser light irradiations are performed, and that each laser light is applied to a position separated by a certain distance in the length direction of the dam bar.

As shown in FIG. 1, a laser processing apparatus according to the present embodiment includes a laser oscillator 10 including a laser head 11 and a laser power supply 13, a processing head 12, and a workpiece (an IC package). 1. An XY table 21 as a transporting means for mounting and moving the laser head 11 in a horizontal plane (XY plane), a Z table 22 for vertically moving the laser head 11 and the processing head 12 (Z-axis direction), a main controller 23, and a trigger unit A control unit 25 having a control unit 24 is provided. The main controller 23 controls the movement of the XY table 21 in the horizontal plane, the movement of the Z table 22 in the vertical direction, and the laser oscillator 1.
The oscillation operation of 0 is automatically controlled. Further, the XY table 21 is provided with an encoder 210 for detecting a moving amount of the XY table 21.

The laser power supply 13 includes a stabilized power supply 130,
It has a capacitor section 131, a switch section 132, and a laser controller 26. In the laser power supply 13, first, the AC current supplied from the AC power supply unit 133 is supplied to the stabilizing power supply unit 130, changed to DC according to the voltage value commanded by the laser controller 26, and supplied to the capacitor unit 131. . The electric charge supplied to the capacitor unit 131 at the above-described voltage value causes the laser head 1 to open and close according to a predetermined pulse width according to a trigger signal FP (described later) from the laser controller 26.
1 is supplied to the excitation lamp 110 provided in the first embodiment. The excitation lamp 110 emits light by the pulse-like charges, thereby exciting the laser medium and emitting pulse-like laser light.

The laser head 11 shown in FIG. 1 has a built-in beam shutter 111. This beam shutter 1
Numeral 11 controls ON / OFF of the pulsed laser light emitted from the laser oscillator 10 by opening and closing, and controls the irradiation of the work 1 with the laser light. That is, when processing the work 1, the beam shutter 111 is opened, and when not processing, the beam shutter 111 is closed. The opening and closing operation time of the beam shutter 111 is 100 to 300 msec.
It is about. The opening / closing operation of the beam shutter 111 is controlled by the laser controller 26, but can be controlled by the main controller 23 via the laser controller 26.

Further, as shown in FIG.
A dichroic mirror 120 and a condenser lens 121 having high reflectance characteristics with respect to the wavelength of the laser light are provided therein, and these configurations are the same as those of a conventional laser processing apparatus. In the present embodiment, the detection light source 122 that generates laser light as detection light, the collimator lens 1
23, half mirror 124, rotary wedge substrate device 3
A detection optical system 127 including an imaging lens 125 and a photodetector 126 is added. The above detection light source 1
A laser light source such as a laser diode (semiconductor laser) is used as 22. The detection optical system 127 is basically similar in configuration to the optical system of an optical pickup unit that reads a disk signal of a CD player. It goes without saying that the laser light used as the detection light is different from the laser light for performing the laser processing.

The rotary wedge substrate device 300 includes a single wedge substrate 301, a frame 302 supporting the wedge substrate 301, a pinion 303 attached to the outer periphery of the frame 302, a pinion 304 meshing with the pinion 303, and a pinion 304. It has a motor 305 that is driven to rotate. The frame 302, and thus the wedge substrate 301,
Is transmitted through the pinion 304 and the pinion 303, and rotates around the axis R of the wedge substrate 301 parallel to the original optical axis of the detection laser beam 200.
Any rotation angle can be set. Further, detection laser beam 200 incident on the wedge substrate 301 proceeds inclined by a predetermined angle phi ₁ to its original optical axis. The angle φ ₁ depends on the inclination angle θ ₁ of the slope of the wedge substrate 301.

As shown in FIG. 3, the trigger unit 24 includes a comparator 241, a gate circuit 242, a selection circuit 243, a delay circuit 244, a counter circuit 245,
A storage device 246 is provided. In this trigger unit 24, the detection signal from the photodetector 126 is binarized by the threshold V _th in the comparator 241 is a comparator signal S _c is produced, the gate circuit 242
Is input to In the gate circuit 242, a gate signal (gate width W _G) is generated in synchronization with the rising of the trigger signal FP input from the trigger circuit 262 of the laser controller 26, the output of the trigger signal TG ₁ in response to the gate signal Do. That is, when the gate signal is OFF (Low) in the gate circuit 242, the gate circuit 24
The trigger signal TG ₁ in synchronization with the rising edge of the comparator signal S _c inputted to 2 are output, whereas the trigger signal TG ₁ in synchronization with the rising edge of the comparator signal S _c when the gate signal is ON (High) is not output (See FIG. 5). The trigger signal TG ₁ is input to the selection circuit 243, and thereafter, is used for the first laser irradiation, and the trigger signal TG ₁ is also input to the counter circuit 245.

Furthermore, the counter circuit 245 is input encoder pulses from the encoder 210, the number of pulses of the encoder pulses according to the input timing of the trigger signal TG ₁ is counted, X based on the count number
The moving distance of the Y table 21 is measured, and the measured value is stored in the storage device 246. At the time of the second laser light irradiation, the XY table 21 stored in the storage device 246 is used.
The trigger signal TG ₂ is input to the selection circuit 243 from the counter circuit 245 based on the moving distance data of

The selection circuit 243 selects the type of signal to be output to the delay circuit 244 according to a command from the main controller 23 (whether the first laser beam irradiation or the second laser beam irradiation). In other words, the trigger signal TG ₁ is selected if the instruction from the main controller 23 is related to the first laser light irradiation, when it relates to a laser beam irradiation for the second time, a selection trigger signal TG ₂ is inputted to the delay circuit 244 as a trigger signal TG _3. In the delay circuit 244, the main controller 2
3 is given a delay time T _D1 or T _D2 ,
Is output as the trigger signal TG ₄ to trigger circuit 262 of the laser controller 26. Here, the delay time T _D1 is used for the first laser light irradiation, and the delay time T _D2 is used for the second laser light irradiation. Note that the gate circuit 242 is erroneous detection prevention means.

As shown in FIG. 4, the laser controller 26 includes an input / output unit 260, a central processing unit 261, and a trigger circuit 262. Trigger circuit 262
Generates a trigger signal FP having a pulse width designated by the main controller 23 to the central processing unit 261 in synchronization with the rise of the trigger signal TG ₄ from the trigger unit 24, and this trigger signal FP is input to the switch unit 132. You. The voltage value of the electric charge supplied to the capacitor unit 131 is input from the input / output unit 260 to the central processing unit 261, and is instructed from the central processing unit 261 to the stabilized power supply unit 130. Thereafter, the laser light oscillates according to the above-described process. On the other hand, the trigger signal FP from the trigger circuit 262 is transmitted to the gate circuit 242 of the trigger unit 24 (FIG. 3).
See also).

Returning to FIG. 2, the functions of the processing head 12 and the detection optical system 127 will be described. First, the pulse laser beam 100 oscillated from the laser head 11 is applied to the dichroic mirror 12
At 0, the direction is changed, and the light is condensed by the condenser lens 121 and irradiated onto the work 1. The detection light 200 emitted from the detection light source 122 is converted into parallel light by the collimator lens 123, passes through the half mirror 124, the wedge substrate 301, and the dichroic mirror 120, and forms a minute spot on the work 1 by the condenser lens 121. Form an image.

Here, since the inclination angle of the slope of the wedge substrate 301 is constant at θ ₁ , the detection laser beam 200 emitted from the wedge substrate 301 is inclined at a constant angle φ _{1 with} respect to the original optical axis R. And proceed, the pulsed laser light 100
Reaches a position separated from the irradiation position by a certain distance r ₀ . The relationship between r ₀ and θ ₁ is as follows: When the focal length of the condenser lens 121 is F and the refractive index of the wedge substrate 301 with respect to the detection laser beam 200 is n, r ₀ = F · (n−1) · θ ₁ ... (1) Further, by rotating the wedge substrate 301 around its axis R, the detection laser beam 200
Can be formed at an arbitrary position on the circumference of a radius r ₀ centered on the condensing position (spot position) of the pulsed laser beam 100. The focusing position of the detection laser beam 200 based on the focusing position of the pulse laser beam 100 is represented by a vector [δ].
r], [δr] = (δr _x , δr _Y ) = (r ₀ cos ω, r ₀ sin ω) (2) Here, ω is the rotation angle of the wedge substrate 301 around the axis R.

The detection light 200 reflected on the surface of the work 1 is
After passing through the condenser lens 121, the dichroic mirror 120, the wedge substrate 301, and the half mirror 124, the imaging lens 12
5, the light is collected by the photodetector 126, and information on the surface of the work 1 is detected as an electric signal. In the present embodiment, since a laser light source is used as the detection light source 122, the laser light is used for the collimator lens 123 and the condenser lens 1.
21 makes it possible to reduce the aperture very small, and when detecting information on the surface of the work 1 (such as the presence or absence of a lead), the rise (response) of a signal becomes faster and detection can be performed with high resolution.

The operation of the laser processing apparatus having the above configuration will be described. FIG. 5 is a diagram showing the vicinity of the dam bar when the dam bar 2 on one side of the IC package is removed, and a time chart corresponding thereto. Work 1 (IC
Package) by the XY table 21 as shown in FIG.
Is moved at a constant speed v in the positive direction of the X-axis, the detection light 200 focused on the minute spot moves on the workpiece 1 at the reference position O.
Move along the locus 5 from. Thereby, the photodetector 1
The change in the detection signal detected at 26 becomes a high output at the web portion (lead portion) 4 and a low output at the slit portion 3. At this time, if the web portion 4 and the slit portion 3 of the work 1 are arranged at equal pitches, the detection signal when the XY table moves at a constant speed is detected as a waveform having a constant period.
On the other hand, when the web portion 4 and the slit portion 3 of the work 1 are not arranged at the same pitch, the detection signal is detected as a waveform having a time change proportional to the change in the pitch.

However, as described above, the pulse laser beam 100
The focusing position of the detection laser beam 200 with reference to the focusing position of δr _X = r ₀ cosω in the _X -axis direction and δr _Y =
Although it is shifted by r ₀ sin ω, when it is moved in the positive direction of the X-axis, −90 ° <ω <0 ° (3), and the focus position of the detection light 200 is relative to the focus position of the pulse laser 100. Δr _X = r ₀ co in the moving direction (X-axis positive direction)
It precedes by sω. This way,
In the case where the focus position of the detection light 200 does not precede the focus position of the pulse laser 100 (δr _x = 0), the waveform has a waveform preceding by T _AD = δr _x / v.

When ω satisfies the above equation (3), the focus position of the detection light 200 is shifted in the negative Y-axis direction with respect to the focus position of the pulse laser 100 as shown in FIG. A certain δr _Y = r ₀ sin ω is a shift amount of the condensing position (detection position) of the detection laser beam 200 from the center line of the dam bar 2 in the longitudinal direction of the lead. However, δr is set so that the converging position of the detection light 200 crosses the parallel portion of the web portion 4 and scans.
Set _Y. In the present embodiment, the rotary wedge substrate device 300 is used. However, the condensing position of the detection light 200 is changed by other means, for example, by changing the angle of the half mirror 124.
It may be shifted with respect to the zero focusing position.

In this embodiment, as will be described later, the dam bar 2
The laser beam is irradiated to the central portion of the workpiece to remove the laser beam. When the workpiece is processed by irradiating the laser beam in this way, a molten scattered substance (hereinafter, referred to as sputtering) 9 is generated from the processing position. When the sputter 9 adheres to the web part 4, the detection light 200 is scattered by the sputter 9,
This affects the waveform of the detection signal detected by the photodetector 126, and the portion corresponding to the sputter 9 has a low output as indicated by the arrow 9a in FIG.

Next, this detection signal is transmitted to the trigger unit 24.
And binarized by the process shown in the time chart of FIG. However, since the horizontal axis (time axis) in FIG. 5 is displayed based on the spot position of the processing laser 100, the waveform of the condensing position of the detection light 200 is only the amount preceding the condensing position of the pulse laser 100. It is out of alignment.

The detection signal input to the trigger unit 24 includes a comparator signal S _c next is binarized based on the threshold voltage V _th in the comparator 241 is input to the gate circuit 242. At this time, the level (intensity of light) of the detection signal of the detection light 200 scattered by the sputtering 9
Although but no problem is greater than the threshold value V _th, when smaller than V _TH as shown in FIG. 5, the comparator signal S _c is output also to the detection signal drops output level by the sputtering 9 Will be done. Although the rectangular wave signal S _c is input to the gate circuit 242, a gate signal in synchronization with the rising of the trigger signal FP from the trigger circuit 262 (gate width W _G) is generated, the gate signal is OFF (Low) In this case, the comparator signal S _c
Trigger signal TG ₁ synchronized with the rising edge of
The trigger signal TG ₁ in synchronization with the rising edge of the comparator signal S _c when the gate signal is ON (High) is not output. This comparator signal S _c based on the sputter 9 is removed by the presence or absence of the web portion 4 (arrangement state)
Only the trigger signal TG ₁ based on is input to both of the selection circuit 243 and the counter circuit 245.

At the time of the first laser irradiation (XY table 21
The scanning time) of the detection position and a processing position by the counter circuit 245 is an encoder for each input of the trigger signal TG ₁ 2
The encoder pulse from 10 is counted, and the moving distance of the XY table 21 is measured based on the counted number,
The moving distance is stored in the storage device 246. For example, k
Th of the total number of pulses of the trigger signal TG ₁ at input A N ⁱ _k, when the measured value of the moving distance of the XY table 21 corresponding to the N ⁱ _k is an L ⁱ _k, the value of L ⁱ _k Is storage device 2
It is output to 46. Here, assuming that the number of web portions 4 on one side of the IC package is p, k is an integer of 1 to p, i is the number of the side of the IC package, and i is i.
Is an integer of 1 to 4.

The selection circuit 243 selects the trigger signal TG ₁ when the command from the main controller 23 is for the first laser beam irradiation as described above, and inputs it to the delay circuit 244 as the trigger signal TG _3. delay circuit 244 provides a delay time T _D1 for the first time of the laser beam irradiated to the trigger signal TG _3, and output as the trigger signal TG ₄ to the laser controller 26.

In the laser controller 26, the trigger signal TG ₄ is input to the trigger circuit 262,
From 2 trigger signal FP in synchronization with the rising of the trigger signal TG ₄ is output. The pulse width of the trigger signal FP is specified by the main controller 23 via the central processing unit 261 as described above. Further, the trigger signal FP is input to the switch unit 132, and the switch unit 132 is turned on in synchronization with the rise of the trigger signal FP, and the electric charge from the capacitor unit 131 is supplied to the excitation lamp 110. Synchronously, the switch unit 132 is turned off, and supply of electric charge to the excitation lamp 110 stops. As described above, the trigger signal F
A pulsed laser beam synchronized with P oscillates. Although having a trigger signal TG ₁ ~FP and laser light pulse waveform having a actually in width in FIG. 5, for very pulse width is shorter than the other signal, the linear shape is in Fig. Is shown. Further, from the trigger signal FP to the oscillation of the laser light there are slight delay time [delta] _t.

Further, the trigger signal FP is supplied to the gate circuit 24.
It is also fed back to 2. In the gate circuit 242,
By generating a gate signal such as they occur diagram of a trigger signal FP for a laser beam oscillator, sets the gate width W _G of the gate signal to the appropriate length, the web portion 4
Signal S caused by the melted scattered matter 9 attached to the
_c gating signal at the rising edge of the is turned ON (High), it is possible to output only the trigger signal TG ₁ in synchronization with the rising edge of the comparator signal S _c which corresponds to the edge of the web portion 4.

The above is the operation at the time of the first laser irradiation. The operation at the time of the second laser irradiation (when the detection position and the processing position are scanned by the XY table 21) is as follows. First, the number of pulses to which the encoder pulse is input from the encoder 210 is counted by the counter circuit 245, and a trigger signal TG ₂ for laser light irradiation is counted based on the measurement value already stored in the storage device 246. The signal is output from the circuit 245 to the selection circuit 243. For example, the count value of the pulse number, when it reaches the number of pulses N ⁱ _k corresponding to the k-th measured value L ⁱ _k of dam bar 2, the trigger signal TG ₂ is output to the selection circuit 243. However, also in this case, the same trajectory 5 as the first time is scanned from the reference position O in FIG.

The selection circuit 243 includes the main controller 2
A command indicating the third and second laser beam irradiation is input, a trigger signal TG ₂ is selected according to the command, and input to the delay circuit 244 as the trigger signal TG ₃ , and the delay circuit 244 issues a command from the main controller 23. The delay time T _D2 for the second laser light irradiation is given and output to the trigger circuit 262 of the laser controller 26 as a trigger signal TG ₄ . However, the relationship between the delay times T _D2 and T _D1 may be set in accordance with the size (length) of the dam bar 2. In the case where the same position is irradiated with laser light the first time and the second time, T _{D1 is used.} And T _D2 may be set to the same value. Thereafter, a predetermined position of the dam bar 2 is accurately irradiated with laser light in the same manner as in the first laser light irradiation.

In the above description, the case where the dam bar 2 on the side of the IC package shown in FIG. 5 is cut and removed has been mainly described, but subsequently, the dam bar 2 on each of the remaining three sides of the IC package is sequentially cut and removed. The case of removal will be described with reference to FIG. However, in FIG. 6, the irradiation position of the detection light 200 is represented by 200A. When the cutting of the dam bar on the side shown in FIG. 5 is completed, the wedge substrate 301 is rotated by 90 ° counterclockwise about the axis R by the motor 305. Then, the processing position is moved by the XY table 21 in the positive direction of the Y axis at a constant speed v, and the pulse laser is used as described above based on the detection signal (along the trajectory 6) based on the reflected light of the detection light 200. Dam bar 2 by light 100
Is cut and removed. Next, after further rotating the wedge substrate 301 counterclockwise by 90 °, the processing position is moved by the XY table 21 in the negative direction of the X axis at a constant speed v, and based on the reflected light of the detection light 200 (trajectory 7). Based on the detection signal, the dam bar 2 is cut and removed by the pulse laser beam 100 as described above. Next, after further rotating the wedge substrate 301 counterclockwise by 90 °, the processing position is moved by the XY table 21 in the negative direction of the Y-axis at a constant speed v, and the processing position is determined based on the reflected light of the detection light 200 (trajectory 8). Cutting the dam bar 2 by the pulse laser beam 100 based on the detection signal as described above,
Perform removal. Thus, the cutting and removal of the dam bar 2 on all four sides of the IC package are completed.

In the case of irradiating laser light three or more times, the same procedure as in the second time may be performed.
In that case, the delay time given by the delay circuit 244 may be set appropriately.

According to the present embodiment as described above, when processing is performed by irradiating the laser beam 100 at least twice,
In addition to avoiding unnecessary laser processing based on the melted scattered matter 9 during the first irradiation of the laser light 100, the second and subsequent irradiations of the laser light 100 were obtained during the first scanning. Trigger signal TG ₁ and encoder 210
Counter circuit 24 based on the encoder pulse from
5. In the selection circuit 243 and the delay circuit 244, control is performed such that the second and subsequent laser beams are applied to a position corresponding to the irradiation position of the first laser beam 100, so that the second and subsequent laser beam irradiations are also accurate. Position can be applied.

Therefore, even during the second and subsequent irradiations of the laser beam 100, laser processing is not performed unnecessarily on the basis of the scattered and scattered materials 9 generated by the laser processing.
In addition, regardless of whether it is the first laser light irradiation or the second or later laser light irradiation, a position separated by a certain distance from the position where the information on the presence or absence of the workpiece (array of the web section 4) is detected. Is irradiated with the laser beam 100, the desired position to be cut can be processed reliably and at high speed not only when the processing positions (dam bars 2) are at equal intervals but also when they are not at equal intervals.

[0053]

According to the present invention, when processing is performed by irradiating a laser beam at least twice to a range including a processing position of a workpiece to be processed, the laser beam is irradiated based on the melted scattered material at the first laser beam irradiation. In addition to avoiding unnecessary laser processing, the second and subsequent laser light irradiations are performed based on the detection signal obtained during the scanning for the first laser light irradiation. Since the oscillation of the laser light is controlled so that the second or later laser light is applied to a position corresponding to the laser light irradiation position, the second and subsequent laser light irradiation can also be performed at an accurate position.

Therefore, during the second and subsequent laser beam irradiations, unnecessary laser processing is not performed based on the melted and scattered substances generated by the laser processing. Irrespective of the second or later laser light irradiation, the laser light is applied to a position separated by a certain distance from the position where the information on the presence or absence of the workpiece is detected, so the processing positions are at equal intervals In addition, even when the intervals are not equal, a desired position to be cut can be processed reliably and at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a configuration of a laser processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a configuration of a processing head and a detection optical system of FIG. 1;

FIG. 3 is a diagram illustrating a configuration of a trigger unit in FIG. 1;

FIG. 4 is a diagram illustrating a configuration of a laser controller of FIG. 1;

FIG. 5 is a time chart from the output of a detection signal from a photodetector to the first and second oscillations of laser light.

FIG. 6 is a diagram showing a situation in which dam bars on four sides of an IC package are sequentially cut and removed.

FIG. 7 is a schematic diagram of a configuration of a conventional laser processing apparatus.

8A is a diagram showing an IC package having a dam bar, and FIG. 8B is an enlarged view of a portion B of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work 2 Dam bar 3 Slit part 4 Web part (lead part) 9 Melted and scattered material 10 Laser oscillator 11 Laser head 12 Processing head 13 Laser power supply 21 XY table 22 Z table 23 Main controller 24 Trigger unit 25 Control unit 26 Laser controller 100 pulse Laser light 110 excitation lamp 111 beam shutter 120 dichroic mirror 121 condenser lens 122 detection light source 123 collimator lens 124 half mirror 125 imaging lens 126 photodetector 130 stabilizing power supply unit 131 capacitor unit 132 switch unit 133 AC power supply unit 200 detection light 241 Comparator 242 Gate circuit 243 Selection circuit 244 Delay circuit 245 Counter circuit 246 Storage device 260 Input / output unit 261 Central function Part 262 trigger circuit

Claims (2)

[Claims] 1. A laser oscillator that oscillates pulsed laser light, a processing optical system that guides the laser light to a processing position of a workpiece, and a transport unit that moves the workpiece and determines the processing position. A laser processing apparatus that performs processing by irradiating laser light at least twice to a range including the processing position on the workpiece, a detection light for detecting the presence or absence of the workpiece at the processing position. A detection light source that generates reflected light, a detection unit that detects reflected light of the detection light from the workpiece, and generates a detection signal corresponding to the reflected light, of the detection signals, near the processing position during laser processing. An erroneous detection preventing unit that removes a change in a detection signal caused by the adhered molten and scattered material and extracts only a change in a detection signal based on the presence or absence of a workpiece near the processing position; Control means for controlling the oscillation of the laser light so that the processing position of the workpiece is irradiated with the first laser light based on a change in the detection signal taken out by the output prevention means; and Storage means for measuring and storing the first laser light irradiation position; and control for controlling the oscillation of the laser light so that the position corresponding to the stored first laser light irradiation position is irradiated with the second or later laser light. And a laser processing device. 2. A processing position is determined by moving a workpiece.
In a laser processing method for generating a pulsed laser beam from a laser oscillator and irradiating the laser beam at least twice to a range including the processing position to process the workpiece, the workpiece in the vicinity of the processing position Irradiating a detection light for detecting the presence or absence of the vicinity of the processing position, of the reflected light of the detection light from the vicinity of the processing position, a light caused by a molten scattered substance attached to the vicinity of the processing position during laser processing. And detecting only a change in the reflected light of the detection light based on the presence or absence of the workpiece in the vicinity of the processing position and generating a corresponding detection signal, and performing the processing based on the change in the detection signal. Controlling the oscillation of the laser light so that the processing position of the object is irradiated with the first laser light; measuring and storing the first laser light irradiation position based on the detection signal; Laser processing method characterized in that second or subsequent laser beam with a position corresponding to the laser beam irradiation position of the first controls the oscillation of the laser beam to be irradiated.