JP2008541489A - Method and apparatus for evaluating part picking motion of an electronic assembly machine - Google Patents

Abstract

  An electronic assembly machine (10, 201) having an improved picking rating is provided. The apparatus (10, 201) includes a mounting head (206) having at least one nozzle (208, 210, 212) for removably picking up and holding the component (304). A robotic system is provided to generate relative motion between the mounting head (206) and the workpiece (203), eg, a circuit board. An image acquisition system (300) is provided to obtain at least one pre-picking image of the component pick-up location (16) and at least one post-picking image of the component pick-up location (16). The pre-picking image includes a plurality of image portions, and the view of the pickup position from different viewpoints is captured in each image portion, while the post-picking image includes a plurality of image portions, and the views of the pickup positions from different viewpoints are Make it catch in the image part.

Description

Copyright Retention Part of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner does not object to the facsimile reproduction of patent documents or patent disclosures by anyone, as stated in the Patent and Trademark Office patent file or record, but without any unauthorized reproduction. Forbid.

BACKGROUND OF THE INVENTION Pick and place machines are commonly used to manufacture electronic circuit boards. Typically, a raw printed circuit board is supplied to a pick and place machine, which then picks an electronic component from a component supply and mounts the component on the substrate. The component is temporarily held on the substrate by the solder paste or adhesive until subsequent steps when the solder paste melts or the adhesive is fully cured.

  The operation of the pick and place machine is interesting. Since the machine speed corresponds to the throughput, the faster the pick and place machine moves, the cheaper the manufactured substrate. In addition, mounting accuracy is extremely important. Many electrical components, such as chip capacitors and chip resistors, are relatively small and must be mounted accurately on a uniformly small mounting location. Other parts, even larger ones, have a substantial number of leads or conductors spaced relatively fine pitch from each other. Such parts must also be correctly installed to ensure that each lead is mounted on the appropriate pad. Thus, not only must the machine operate at very high speeds, but also the parts must be mounted very accurately.

  In order to improve the quality of board manufacture, fully or partially mounted boards are generally inspected both before and after solder reflow after the mounting operation and are missing, improperly installed Identify parts that are either of various errors that can occur. Automated systems that perform such operations are very useful in that they help identify component mounting problems prior to solder reflow, and the rework of defective substrates after reflow to be reworked. Processing or identification can be made substantially easier. An example of such a system is commercially available under the trade name Model KS Flex, available from CyberOptics Corporation, Golden Valley, Minnesota. Using this system, alignment and rotation errors, missing or repelled parts, billboards when parts are improperly placed on long edges, parts are improperly placed on short edges Tombstones in certain cases, such as partial billboards and tombstones when parts are oriented between their vertical orientation and billboard or tombstone orientation, part failure, improper polarity, and wrong parts The problem can be identified. Identifying errors before reflow offers many advantages. Rework becomes easier, facilitates closed-loop manufacturing control, and there is less work in the process between error generation and handling. While such a system provides highly useful testing, it spends programming time, maintenance effort, etc. in addition to plant floor space.

  One relatively recent attempt to provide the advantage of post-installation inspection located within the pick and place machine itself is disclosed in US Pat. No. 6,317,972 to Asai et al. This reference reports a method for mounting electrical components, where an image of the mounting position is obtained before mounting the component, and it is mounted at the component level compared to the image of the mounting position after mounting the component. Check operation. Although Asai et al.'S disclosure reveals one attempt to inspect part installation behavior using part-level inspection inside the machine, part orientation errors also occur during the part pick-up process. there is a possibility. This process leaves challenges and major factors to the overall operational quality of pick and place machines.

  Part pick-up requires a mounting head that is positioned over the pick-up point of the part of interest. Once the nozzle is positioned, it is lowered to a point just above the part and is generally depressurized through the nozzle to suck up the part and temporarily attach it to the tip of the nozzle. Each component is positioned at each picking point by a component supply mechanism. A general supply mechanism includes a tape supply unit, a vibration supply unit, and a tray supply unit. If it is necessary to configure the pick and place machine to assemble a new workpiece, the operator inserts the parts supply at those positions according to the instruction procedure determined by the program of the pick and place machine. In addition, an identification mark, such as a bar code, can be positioned on the supply mechanism to ensure that the appropriate supply is positioned in the proper position and sequence within the pick and place machine. Once a part is picked up by the nozzle, the supply mechanism must move the other part to the picking position.

  If the part picking operation fails, a defective workpiece is produced. Workpiece defects known to be caused by incorrect picking operations are tombstoned parts, missing parts, wrong parts, wrong part polarity, and misplaced parts. An incorrect picking condition can be caused by an operator loading the supply into an incorrect position, leaving the supply out of parts, or a defective or broken supply, parts tape and nozzle, Properly programmed nozzle picking heights, which can be caused by discrepancies in the normal picking process, resulting in parts being picked into the nozzle, tombstone orientation, billboard orientation, or parts It is held in the corner direction that contacts the nozzle at one corner. Either of these leads to incorrect placement of the parts.

SUMMARY OF THE INVENTION An electronic assembly machine with improved picking evaluation is provided. The machine includes a mounting head having at least one nozzle for removably picking up and holding the part. A robotic system is provided to generate relative motion between the mounting head and a workpiece, such as a circuit board. An image acquisition system is provided to obtain at least one pre-picking image of the component pick-up location and at least one post-picking image of the component pick-up location. The pre-picking image includes a plurality of image portions, and the view of the pickup position from different viewpoints is captured in each image portion, while the post-picking image includes a plurality of image portions, and the views of the pickup positions from different viewpoints are Make it catch in the image part.

DETAILED DESCRIPTION FIG. 1 is a diagram of a representative Cartesian pick and place machine 201 to which embodiments of the present invention are applicable. The pick and place machine 201 receives a workpiece, such as a circuit board 203, via a transfer system or conveyor 202. Thereafter, the mounting head 206 obtains from the component supply (not shown) one or more electrical components to be mounted on the workpiece 203 and moves in the x, y, and z directions for proper placement on the workpiece 203. Install the parts in the correct position in the correct orientation. The mounting head 206 includes a plurality of nozzles 208, 210, 212 and can pick a plurality of parts. Some pick and place machines can use a mounting head that moves over a fixed camera to image the part to verify the part position and orientation on each nozzle. The mounting head 206 can also include a downward-facing camera 209, which is typically used to position a reference mark on the workpiece 203 and to easily calculate the relative position of the mounting head 206 relative to the workpiece 203. Have been able to.

  FIG. 2 is a diagram of a representative rotary tale topic and place machine 10 to which embodiments of the present invention are further applicable. Machine 10 includes several parts that are similar to machine 201, and like parts are similarly numbered. In the tallet topic and place machine 10, a workpiece 203 is loaded on an xy stage (not shown) via a conveyor. The nozzles 210 are attached to the main turret 20 and are arranged around the rotating turret at regular angular intervals. During each pick and place cycle, the turret 20 determines an angular spacing equal to the angular spacing between adjacent mounting nozzles 210. After the turret 20 is rotated into position and the workpiece 203 is positioned by the xy stage, the mounting nozzle 210 obtains a part 304 (shown in FIG. 3) from the part supply 14 at a defined pick point 16. . During this same interval, another nozzle 210 mounts the part 304 on the workpiece 203 at the programmed mounting position 106. In addition, while the turret 20 interrupts the pick and place operation, the upward facing camera 30 acquires an image of another part 304, thereby providing alignment information for that part. Using this alignment information, the pick and place machine 10 positions the workpiece 203 when the mounting nozzle 210 is positioned to mount the part 104 after several steps. After completion of the pick and place cycle, the turret 20 determines the next angular position and the workpiece 203 is repositioned in the xy direction to move the mounting position to a position corresponding to the mounting position 106.

  FIG. 3 is a diagram of a mounting head according to an embodiment of the present invention. FIG. 3 illustrates an image acquisition system 300 arranged to acquire an image of the component 304 at the pick-up position 16 before and after the component 304 is picked up from the position 16 of the supply 14 by the nozzle 210. . The device 300 obtains an image of the pickup position 16 on the supply unit 14 before and immediately after the component 304 is picked up. By comparing these images before and after, it becomes easy to inspect and verify the pickup at the component level. In addition, an area surrounded by the component pickup position 16 is further imaged. In general, since the image of the pickup position 16 is acquired when the nozzle 210 is positioned on the pickup position 16, the pickup position 16 is imaged at the same time from the part 304 itself or the part of the mounting nozzle 210. It is important to be able to minimize or reduce the interference. Thus, it is preferred that system 300 uses an optical axis that is visible at an angle θ with respect to the axis of nozzle 210. A further advantage of tilting the system 300 at an angle θ is to detect the vertical movement of the parts 304, the supply, and the part holding tape / tray by determining their translational movement during image acquisition. It can be measured. Strictly measure the time between image acquisitions so that the pick-up position 16 and mounting head 210 are aligned relative to each other so that the part 304 is in the supply 14 and can be viewed from the camera angle. Is even more effective. After the part 304 is picked up, the second image is preferably timed to be a preselected time during the pick-up cycle. A method for precisely timing the acquisition of these two images is described in co-pending application No. 10 / 970,355.

  Embodiments of the present invention generally provide two or more consecutive image sets (i.e., before and after pickup) of target pickup positions. Since pick-up takes place relatively quickly and the reduction in machine throughput is highly undesirable, sometimes two consecutive images are taken because the relative movement between the mounting head and the pick-up position is momentary. Need to get very quickly. For example, it may be necessary to acquire two images within approximately 10 milliseconds.

  FIG. 4 is a diagram of an image acquisition system 300 arranged to acquire one or more images associated with a picking operation according to an embodiment of the present invention. Preferably, the image acquisition system 300 includes an electronic camera (CCD, CMOS, etc.) arranged to capture the part 304 when the part 304 is held by the nozzle 210. Preferably, the image acquisition system 300 is arranged with an optical axis to capture the component 304 from a non-zero angle with respect to the horizontal. System 300 also preferably includes an illuminator 310 that generates illumination 312, which is redirected by illumination optics 314. The redirected illumination 316 passes through an area proximate to the part 304 when the part 304 is maintained on the nozzle 210. The imaging optical system 318 is arranged to focus on the image acquisition system 300 by changing the direction of illumination. By using the illumination optical system 314 and the imaging optical system 318, even if the component 304 is maintained at an angle different from the imaging optical axis of the image acquisition system 300, the image acquisition system 300 is in front of the backlight side of the component 304. A figure can be obtained. Preferably, the image acquisition system 300 obtains an image of the nozzle 210 before the nozzle 210 picks the component 304 from the component supply unit 14. Then, after the component 304 is picked by the nozzle 210, the image acquisition system 300 obtains a second post-picking image. Comparing the images before and after picking provides important information related to the effectiveness of the picking operation.

  FIG. 5 is a front plan view of the system illustrated in FIG. 4 with the nozzle 210 removed for ease of illustration. FIG. 5 illustrates an image acquisition system 300 generating a pair of illumination beams 312A, 312B, which impinge on illumination optics 314A, 314B, respectively. The illumination optics 314A, 314B change the direction of illumination, and the imaging optics 318A, 318B provide a backlight view of the component 304 from two different viewpoints. The angle interval between the viewpoints is preferably 90 degrees. However, it is expressly contemplated that any suitable angular spacing can be used in accordance with embodiments of the present invention and more than one viewpoint can be used. Preferably, the image acquisition system 300 acquires a single image having multiple viewpoints in a single imaging operation of the system 300. In addition, the configuration of optical systems 314A, 314B, and / or 318A, 318B can include elements with or without optical power and elements used for transmission or reflection. Preferably, these optics adjust the direction of illumination emanating from one or more illumination sources of system 300. However, embodiments of the present invention also include illumination sources that may not be disposed on or within the system 300.

  FIG. 6 is a diagram of an image before picking of representative three viewpoints acquired in the embodiment of the present invention. The image 350 includes a left image portion 352, a center image portion 354, and a right image portion 356. Each image portion 352, 354, and 356 shows the nozzle 210 from a different angle. In addition, FIG. 6 illustrates the central image portion 354 and has a larger magnification than the left and right image portions 352 and 356.

  FIG. 7 is a diagram of a representative example of the three-view embodiment illustrated in FIG. 6, but after the picking operation of part 304. FIG. As shown in FIG. 7, the left image portion 352 shows a component 304 in one direction, while the right image portion 356 shows a component 304 from different viewpoints. Furthermore, the central image portion 354 shows the part 354 from a middle viewpoint that is distant. By comparing and / or contrasting various images obtained from different viewpoints, important part picking information can be determined. In addition, each picked image part can be compared and / or contrasted with each picked image part to form a different image so that the image of the part can be easily separated while removing irrelevant features. Is done. Then, by comparing or contrasting three different images, a relatively simple technique is provided for issuing picking effectiveness information.

  FIG. 8 is a flow diagram of a method 400 for obtaining a plurality of image sets for a picking operation of an electronic assembly machine. Method 400 begins at step 402 where a pre-picking trigger is generated or received. The pre-picking trigger can be provided in any suitable manner by any suitable technique or device that can reliably signal at the exact time before each picking operation. The trigger can be generated by monitoring X, Y coordinates 404 provided by one or more encoders of the electronic assembly machine. Alternatively or additionally, a pre-picking trigger can be generated by a particular Z motion 406 of the mounting head or nozzle 210. Still further, the pre-picking trigger can be generated based at least in part on the timing function 408. As shown in block 410 by a pre-picking trigger from step 402 by communicating the position of the nozzle 210 and component 304 from the mounting or electronic assembly device via a decoder signal or other suitable signal, as shown in block 410. The image acquisition system 300 is made to acquire at least one pre-picking image having a plurality of image portions indicating nozzles from different viewpoints. As described above, the pre-pick image is preferably obtained during a single imaging operation of the image acquisition system 300. A plurality of pre-picking image portions are arranged, preferably 90 degrees apart, to indicate nozzles from different viewpoints. Next, at block 412, the assembly machine picks the part 304 from the part supplier 160. At block 414, a post-pick trigger is generated or obtained. A post-pick trigger can be generated in response to a Z motion, eg, an upward nozzle motion of 416 a predetermined distance, or the post-pick trigger can be associated with timing 418. For example, the post-pick trigger can be set to produce a precise time after the part 304 is picked. Once the post-pick trigger is generated, the image acquisition system 300 acquires a post-pick image having multiple image portions showing nozzles from different viewpoints, as shown in block 420. The image portion after picking has substantially the same viewpoint as the image portion before picking. Further, the picked image portion is obtained through the same imaging optical system as the picked image and by the same image acquisition system. Therefore, in the generation of different images between a predetermined pre-picking image part and each post-picking image part, the parts picked at the selected viewpoint are easily separated. At block 422, various images, preferably different images, are compared and compared. Image analysis is performed at block 422 and, as a result, picking instructions are provided at block 424. Examples of suitable picking instructions include no errors or defects, that the picked part is completely tombstone, that the picked part is partially tombstone, and that the picked part is building It can be an indication that it is in the board state, that the part is picked at one corner, or that no part has been picked.

  Embodiments of the present invention provide many advantages over the prior art. In particular, imaging is performed from at least two different viewpoints, preferably 90 degrees apart, and the inconvenient orientation of the parts can be analyzed more effectively. In addition, data is acquired immediately after each picking operation, and the analyzed results are available well before the need to install picked parts. Still further, as described above, the same camera and illumination system can be used for picking evaluation and mounting evaluation.

  Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

1 is a diagram of a Cartesian pick and place machine in which embodiments of the present invention can be implemented. 1 is a plan view of a Tale topic and place machine in which embodiments of the present invention may be implemented. FIG. 2 is a simplified diagram of an image acquisition system aligned with a pick-up point of a component mounting machine. FIG. 3 is a diagram of an image acquisition system arranged to acquire one or more images related to a picking operation of an embodiment of the present invention. FIG. 5 is a front plan view of the system illustrated in FIG. 4 with the nozzles removed to simplify the illustration. FIG. 4 is a representative three-viewpoint diagram of a pre-picking image acquired according to an embodiment of the present invention. FIG. 7 is a representative diagram of the three-viewpoint embodiment illustrated in FIG. 6 obtained after a picking operation. FIG. 6 is a flow diagram of a method for acquiring a plurality of image sets relating to a picking operation of an electronic assembly machine.

Claims (20)

A pick and place machine for assembling a workpiece,
A mounting head having at least one nozzle for removably picking up and holding the component;
A robot system for generating relative movement between the mounting head and the workpiece;
An image acquisition system arranged to obtain at least one pre-picking image of the component pick-up location and at least one post-picking image of the component pick-up location;
The pre-picking image includes a plurality of image portions, and the pickup positions from different viewpoints are captured in each image portion.
A pick-and-place machine in which an image after picking includes a plurality of image portions and each image portion captures a pickup position from a different viewpoint.   The pick and place machine according to claim 1, wherein the pre-picking image is obtained with a single imaging operation of the image acquisition system.   The first image portion of the pre-picking image has a first viewpoint of the pickup position, the second image portion of the pre-picking image has a second viewpoint of the pickup position, and the first and second viewpoints are The pick and place machine of claim 1, which is different.   The pick and place machine of claim 3, wherein the first and second viewpoints are approximately 90 degrees apart.   The pick and place machine of claim 1, wherein the picked image is obtained in a single imaging operation of the image acquisition system.   The first image portion of the picked image has a first viewpoint of the pickup position, the second image portion of the picked image has a second viewpoint of the pickup position, and the first and second viewpoints are The pick and place machine of claim 1, which is different.   The pick and place machine of claim 6, wherein the first and second viewpoints are approximately 90 degrees apart.   The pick and place machine of claim 1, further comprising an illuminator arranged to illuminate the part from behind with respect to the image acquisition system.   9. The pick and place machine of claim 8, further comprising illumination optics arranged to receive illumination from the illuminator and to change the direction of illumination to the position of the component.   10. The pick and place machine of claim 9, further comprising imaging optics arranged to focus the backlight image of the part on the image acquisition system.   The pick and place machine of claim 1, further comprising imaging optics arranged to focus a backlit image of the part on the image acquisition system.   The pick and place machine of claim 1, wherein the machine is configured to provide a picking instruction based at least in part on an analysis of a plurality of post-picking image portions.   The pick and place machine of claim 12, wherein the machine is configured to provide a picking instruction based at least in part on an analysis of the plurality of pre-picking image portions.   The machine is configured to provide a picking instruction selected from the group consisting of partial tombstone, full tombstone, partial billboard, complete billboard, corners, and none. Pick and place machine as described.   The pick and place machine of claim 1, wherein the image acquisition system is further arranged to acquire a part mounting image and verify the mounting of the part on the workpiece. A method for evaluating a component picking operation of an electronic assembly machine, comprising:
Obtaining a pre-picking image of a nozzle, wherein the pre-picking image includes a plurality of image portions each corresponding to a different viewpoint of the nozzle;
Obtaining a post-picking image of the nozzle, wherein the post-picking image includes a plurality of image portions each corresponding to a different viewpoint of the nozzle;
Each image part of the image after picking has a viewpoint that matches the viewpoint of the image part of the image before picking,
A method in which image portion analysis provides picking instructions.   The machine is configured to provide a picking instruction selected from the group consisting of partial tombstone, full tombstone, partial billboard, full billboard, corners, and none. The method described.   The method of claim 16, wherein the plurality of image portions includes at least three image portions, and the at least one image portion has a different size than the other image portions.   The method of claim 16, wherein each of the plurality of image portions of the post-picking image represents a nozzle from a different viewpoint, and at least two viewpoints are approximately 90 degrees apart. A mounting head for mounting the part on the workpiece;
A robot system for generating relative movement between the mounting head and the workpiece;
A method for evaluating the picking motion of the machine;
Including an electronic assembly machine.

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