KR20080028278A - Optical Inspection System and Method of Electrical Circuit Devices - Google Patents

Abstract

An optical inspection system of an electric circuit element according to the present invention includes an optical inspection function, an algorithmic inspection function, a display device, and a display controller,

The optical inspection function provides an optical inspection output for one or more regions on the electrical circuit element being inspected,

The algorithmic inspection function provides an algorithmic inspection output of the one or more regions, wherein the algorithmic inspection output indicates the presence of possible defects in the one or more regions,

The display device provides an operator with a visual display of the one or more areas based on the optical inspection output,

The display controller according to the detected operator behavior indicating that the defect has not been identified in the one or more areas, and in accordance with the algorithmic test output indicating the presence of a possible defect in the one or more areas. It provides an indication of a mismatch between the detected operator behavior for the region and the algorithmic test output.

Description

Optical inspection system and method for electric circuit elements {OPTICAL INSPECTION SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical circuit inspection during fabrication of an electrical circuit, and more particularly, to reduce defect misdetection during a printed circuit board inspection.

Automated optical inspection (AOI) systems are well known in the art, and various vendors are known. For example, Orbotech Ltd. in Yavne, Israel. Products are also well known. In general, defect candidates detected by the AOI system are often checked by the person who observes the image of these defect candidates whether they are real defects or not. Applicant has developed an improved process system for automatically identifying defect candidates as genuine defects or false alarms.

The present invention seeks to provide an optical inspection system useful for reducing the number of false detections of defects during a printed circuit board inspection.

According to one embodiment of the present invention, there is provided an optical inspection system of an electrical circuit element, the system comprising an optical inspection function, an algorithmic inspection function, a display device, and a display controller,

The optical inspection function provides an optical inspection output for one or more regions on the electrical circuit element being inspected,

The algorithmic inspection function provides an algorithmic inspection output of the one or more regions, wherein the algorithmic inspection output indicates the presence of possible defects in the one or more regions,

The display device provides an operator with a visual display of the one or more areas based on the optical inspection output,

The display controller according to the detected operator behavior (indicating that no defects have been identified in the one or more regions) and the algorithmic test output (indicative of the presence of possible defects in the one or more regions). Accordingly, an indication of a mismatch between the sensed operator behavior for the one or more regions and the algorithmic test output is provided. The indications of inconsistency include providing the operator with a visual display of the one or more areas once again.

In one embodiment of the invention, the algorithmic inspection function comprises a fluorescence inspection function for triggering fluorescence of the substrate to be inspected. For example, deep violet or ultraviolet (UV) illumination may be used. In addition, the algorithmic inspection function unit may include one or more inspection functions different from the functions used in the optical inspection function unit. The one or more inspection functions may provide one or more of a fluorescence inspection function, a dark field inspection function, a bright field inspection function, an ultraviolet inspection function, and a height inspection function.

In one embodiment of the invention, the optical inspection function may provide a reflection inspection function. The system further includes a defect analyzer, wherein the defect analyzer is operative to receive one or more reference images for the one or more regions and the optical inspection output for the one or more regions, wherein the defect analyzer is inspected and Output indications of the positions of the defect candidates in the electrical circuit element may be provided to one or more of the algorithmic inspection function and the optical inspection function. Preferably, the one or more reference images are derived from one or more computer file references.

According to one embodiment of the invention, the one or more computer file references comprise one or more binary images. The one or more reference images are preferably derived from one or more of a CAD file and a CAM file used in the design or manufacture of the electrical circuit device. Further, the one or more reference images can be obtained from one or more printed circuit boards known to be free of defects.

According to one embodiment of the invention, the visual display comprises one or more reflection images for the one or more regions. The sensed operator behavior preferably includes the behavior by which the operator observes the visual display for less than a designated time. The designated time is less than 5 seconds and may be less than 2 seconds. The detected operator behavior may include a process of receiving an indication when the computer key is pressed (ie, a predetermined sorting operation).

According to one embodiment of the invention there is provided an optical inspection method of an electrical circuit element, the method comprising:

Providing an optical inspection output of at least one region on the electrical circuit element under inspection,

Providing an algorithmic inspection output of said at least one region, wherein said algorithmic inspection output indicates the presence or absence of a possible defect in said at least one region,

Providing an operator with a visual display of said at least one area based on said optical inspection output,

-Depending on the detected operator behavior indicating that a defect has not been identified in the one or more regions, and in accordance with the algorithmic inspection output indicating the presence of a possible defect in the one or more regions, Providing an indication of a mismatch between the algorithmic test output and the sensed operator behavior.

It includes. Providing an indication of inconsistency causes the display device to provide the operator with a visual display of the one or more areas again.

According to one embodiment of the invention, providing the algorithmic test output comprises providing a fluorescence test output. These fluorescence test outputs may appear under deep violet or ultraviolet (UV) light that triggers an appropriate fluorescence reaction. In addition, providing the algorithmic test output includes providing one or more test outputs other than those provided in the optical test output. Providing the one or more test outputs preferably includes providing one or more of a fluorescence test output, a doc field test output, a bright field test output, an ultraviolet test output, and a height test output.

According to one embodiment of the invention, providing an optical inspection output includes providing a reflection inspection output. The method,

Receiving the optical inspection output of the at least one region,

Receiving at least one reference image of the at least one area,

Providing an output indication of the location of the defect candidates of the inspection circuit element under test

It is preferable to further include.

According to one embodiment of the invention, receiving one or more reference images includes deriving one or more reference images from one or more computer file references. Receiving one or more reference images also includes obtaining the one or more reference images from one or more printed circuit boards known to be free of defects.

According to one embodiment of the invention, providing a visual display comprises providing one or more reflected images of the one or more regions. The sensed operator behavior includes a process in which the operator observes the visual display for a time shorter than the specified time. The specified time is less than 5 seconds, and may be less than 2 seconds. The sensed operator behavior involves classifying defects by applying appropriate markers, such as pressing computer keys.

By implementing the present invention, defects in electrical circuit elements can be classified in a more accurate and faster automated manner than in conventional methods.

1 is a simplified partial block diagram of an optical inspection system constructed and operative in accordance with one embodiment of the present invention.

According to one embodiment of the invention, an optical inspection system for electrical circuit elements provides an optical inspection function, which provides an optical inspection output of one or more regions of the electrical circuit element being inspected. The optical inspection system also provides an algorithmic inspection function, which provides an algorithmic inspection output of the one or more regions. This algorithmic test output indicates the presence of a possible defect in the one or more regions. The optical inspection system further includes a display and a display controller. The display provides a human with a visual display of the one or more areas based on optical inspection output. The display controller according to the detected person's behavior (indicating that no defects have been identified in the one or more regions) and algorithmic inspection output (indicating the presence of possible defects in the one or more regions). The inconsistency between the algorithmic test output for the one or more regions and the sensed human behavior is then properly indicated. Properly displaying the inconsistency includes providing a second, visually viable display of the one or more regions. Detected human behavior indicates the presence of actual defects.

As shown in FIG. 1, the optical inspection system 100 includes one or more first inspection stations 110. The first inspection station 110 secures one image that includes one or more reflection images 112 of one or more regions of the first electrical circuit 114 to be inspected. For example, the reflected image 112 can be secured by scanning the first electrical circuit 114. The first inspection station 110 is Orbotech Ltd., Yavne, Israel. It is preferable that it is a Discovery optical inspection system made by the company. However, other suitable inspection stations may be used.

The reflected image 112 is supplied to the defect analysis subsystem 120. The subsystem 120 includes a detection processing function and a confirmation processing function. The detection processing function and the confirmation processing function may be supported by separate CPUs or may use the same CPU. The detection processing function receives the reflection image 112 and also receives a reference image 122 (which may be considered a “reference image”) 122 corresponding to the first electrical circuit 114. Appropriate reference images can be derived from computer file references. Computer file references can be derived from images and CAM files obtained from printed circuit boards that are known to be free of defects. According to one embodiment of the invention, the computer file reference comprises a binary image. In addition, the computer pile reference includes a map of the contour corresponding to the edges between the conductor and the substrate, corresponding to the electrical circuit to be inspected.

The detection processing function of the defect analyzer subsystem 120 operates to optically and automatically inspect the reflected image 112 to compare the reflected image 112 with the reference image 122 and to detect defects on the first electrical circuit 114. The display items of the candidate 126 are output. Upon completion of the optical inspection, each electrical circuit is passed to the confirmation station 130. An example of a verification station is Orbotech's VeriSmart defect identification system in Yavne, Israel. Defect check or correction is performed here. In FIG. 1, a first electrical circuit 114 that performs optical inspection is disposed in the first inspection station 110, and the first inspected electrical circuit 132 is located in the verification station 130. Although confirmation station 130 is shown as being a standalone confirmation station, it does not have to be.

The electrical circuit 132 examined earlier has already been automatically optically inspected at the first inspection station 110 and one or more defect candidates have been identified by the defect handling function of the defect analyzer subsystem 120. The position of the defect candidates on the electrical circuit 132 is different from the position found in other electrical circuits of the same kind. However, for some defect candidates, the positions may be similar, or may be repeated at the same position in the case of the same kind.

The indications of the defect candidates 126, corresponding to the defect candidates identified on the electrical circuit 132 examined previously, are passed to the confirmation controller. The confirmation controller 130 is in signal communication with the confirmation station 130.

The first inspection station 110 and the confirmation station 130 may be separate units as shown in FIG. 1. One example of standalone verification station 130 is Orbotech Ltd. VeriSmart's defect identification system. An example of a standalone optical inspection system is Orbotech Ltd. For example, Discovery's optical inspection system. Some configurations of the Discovery optical inspection system are additionally provided with a video image acquisition system to operate to obtain selected video images of suspected defects. These images can be used to manually filter out suspected defects before calibration is done at the appropriate downstream calibration station. Alternatively, the first inspection station 110 and the confirmation station 130 may be integrally formed. One such example is Orbotech Ltd. An example is Sprion optical inspection system.

The confirmation station 130 preferably includes a camera 140 and a camera positioner 142. The camera positioner 142 sequentially positions the cameras 140 so that the positions of the defect candidates 146 may be sequentially observed according to the output of the confirmation controller. The output of the confirmation controller indicates the position of the defect candidates identified by the detection processing function of the defect analyzer subsystem 120, and the camera positioner 142 moves the camera 140 to the indicated position. In the embodiment shown in FIG. 1, the camera positioner 142 operates to independently control the X-Y positioning of the camera 140. However, it is not necessary to have such a configuration. For example, the camera positioner 142 may control the positioning of the camera 140 in the polar coordinate system.

According to one embodiment of the invention, at each defect candidate location 146 sequentially observed on the electrical circuit 132, this location 146 is illuminated with light suitable for providing an optical inspection output. This optical inspection output is preferably displayed to the operator in the form of a visually recognizable image of the defect candidate location 146. In addition, defect candidate positions may be examined in different irradiation configurations. For example, it can be irradiated with light of one or more wavelengths or different angles of incidence to provide an image suitable for algorithmic analysis.

In one embodiment of the invention, camera 140 reflects image 150 of defect candidate location 146 for light of an appropriate wavelength, such as an image showing response to deep violet or ultraviolet (UV) radiation. And a fluorescence image of the fluorescence reaction is obtained. The camera 140 may add, in addition to or without the fluorescence image 152, a dark field image, a bright field image, an ultraviolet image, an infrared image, different spectra of different spectra. Images, and images obtained using height sensors can be acquired. Fluorescence image 152 and reflection image 150 are typically acquired for a substantially simultaneous time period.

In the embodiment of FIG. 1, when acquiring confirmation images 150, 512 at the first detection location 146, the confirmation processing function of the defect analyzer subsystem 120 is algorithmic (eg, in the background) of the fluorescence image. Perform the evaluation. The camera 140 is relocated to the next defect candidate position, which is provided by the output of the confirmation controller. While one or more confirmation images are acquired at the next location, the operator will evaluate the appropriate image at location 146, such as reflective image 150. In one embodiment of the invention, the acquisition of the confirmation images 150, 152 proceeds at a given image acquisition rate, which proceeds at a slower rate independently of the evaluation by a typical operator. This confirmation image 150 is obtained at each location, stored in memory, and provided to the operator on request. Fluorescence identification images 152 are obtained at selected locations and examined algorithmically in the background. At this time, the algorithmic test result is used to receive the defect check by the operator again.

Reflected image 150 of defect candidate location 146 is preferably displayed to an operator located adjacent to defect analyzer subsystem 120. In general, the operator examines the reflected image 150 to determine if the image contains real defects. If so, it is common for the operator to repair a fault in the electrical circuit 132. If the defect cannot be repaired, the electrical circuit 132 will be marked as "not repairable." If image 150 shows false detection corresponding to "no defects" (ie, it does not contain actual defects), the operator immediately observes the current defect candidate position (typically within 1 to 2 seconds). Inspect the image of the next defect candidate location 146, within at least 5 seconds). However, the system may be configured to provide longer or shorter time intervals for human observation of defect candidate locations. In one embodiment of the invention, upon confirming that the suspected first defective location was a misdetection, the operator can press a computer key to instruct to display images of the next suspected defective location. Thereby, n can be functionally indicated that the suspected first defect location was a misdetection.

Simultaneously with or prior to analysis of the reflected image 150 by the operator, a fluorescence image 152 of defect candidate locations is provided to the validation processing function of the defect analyzer subsystem 120. The subsystem performs an automatic algorithmic analysis of each fluorescence image 152 to algorithmically determine whether the included defect candidates are real defects or are incorrectly detected in the absence of defects. Algorithmic inspection is performed at a given defect location prior to or at the same time as manual defect check performed by the operation, and is used when the check by the operator is completed to confirm the accuracy of the operator check. Suitable automatic identification algorithms include Orbotech Ltd. There is a Sprion system. Other suitable algorithmic identification systems and methods are described in US patent applications 10 / 793,224 and 11 / 254,756.

According to one embodiment of the invention, the defect analyzer subsystem 120 includes a display controller, which displays a defect, depending on the detected operator behavior, such as examining an image of the actual defect for less than two seconds. It indicates that the actual defect was not identified at the candidate position, and according to the algorithmic test output, it indicates the presence or absence of the defect at the defect candidate position 146. If the check marks corresponding to the operator's behavior and the algorithmic results do not coincide with each other, these inconsistencies are displayed and displayed. In one embodiment of the invention, if there is a mismatch between the algorithmic and operator results, the reflected image of the candidate detection position 146 is displayed second to the operator. When displaying the image a second time, it may or may not indicate that the defect location has been observed by the operator earlier.

As shown in Fig. 1, the defect candidate position A is displayed to the operator. The operator simply checks this. If the operator indicates that position A does not contain the actual defect, then the next defect candidate position, that is, defect candidate position B, is displayed within a few seconds. At defect candidate position B, if it is determined that an actual defect exists, the operator corrects it.

If the operator has completed the inspection and correction of the actual defect at the defect candidate position B (which is shown as requiring 40 seconds after the display of the defect code position B), it may take a different time to correct or repair the defect. . The next defect candidate position C is displayed. After observing C, if not marked as defective, the next image is displayed within a few seconds. In this case, the next image corresponds to defect candidate A, which is displayed second.

In one embodiment of the invention, at the same time the operator checks the defect candidate positions, the display controller receives the output of the algorithmic analysis of the defect candidate positions A, B, C, which algorithmic analysis is performed in the background, Whether the candidate position is a real defect is indicated according to the inspection algorithm. In the embodiment of FIG. 1, algorithmic analysis indicates that location A is defective. This was not initially detected by the operator. Position B indicates that it is an actual defect such as the detection result of the operator. Position C indicates that it corresponds to a false detection as determined by the operator. In one embodiment of the invention, if the algorithmic result and the operator's result do not match, the reference image of the defect candidate position A is displayed to the operator. Instead of displaying the reflection image for the position corresponding to the mismatch between the operator result and the algorithmic result again, a method of indicating the mismatch between the operator result and the algorithmic result may be used. For example, inconsistencies can be represented by generating an inconsistency report to return the selected defect locations and give the operator an opportunity to reanalyze. Similarly, the detected operator's behavior corresponds to a detected time interval for evaluating a location as a defective location, or by pressing a computer key to classify a particular location as including a defect or a false detection, etc. It may correspond to other sensed behavior.

2 presents a simplified flowchart of an optical inspection method using the optical inspection system of FIG. 1.

According to one embodiment of the invention, a reflection image of the electrical circuit under inspection is obtained. For example, it is obtained at the inspection station 110 of FIG. The reflected image is automatically optically inspected and analyzed in the defect analyzer subsystem 120 or the like to identify defect candidates of the electrical circuit being inspected. In this step, various defect candidates are identified, and it should be checked whether the defect candidates are real defects or misdetected that there are no defects.

In one embodiment of the invention, an output indicative of each of the defect candidates on the electrical circuit being inspected is processed to filter out repeated defect candidates. This includes, for example, geometric defect candidates that appear repeatedly in a series of similar electrical circuits. Repetitive defect candidates that appear from panel to panel at the same location can be eliminated if they are considered not to contain actual defects, despite repeated geometrical errors. In this regard, reference may be made to the contents disclosed in the US patent application Ser. No. 11 / 072,235.

An output indicative of each of the defect candidates requiring confirmation is provided to a confirmation station, such as confirmation station 130. For each defect candidate location, a reflection image is obtained and provided to the operator of the verification station for inspection.

A second image of the defect candidate location, generally a fluorescence image, is also obtained at the confirmation station 130. The second image is preferably obtained immediately before or after obtaining the reflection image, or at the same time as obtaining the reflection image. Preferably, the fluorescence image includes a defect candidate and a portion of the area surrounding the defect candidates. Corresponding portions of a reference map, such as a reference map derived from a CAM file, are also identified. The fluorescence image is algorithmically computed in the background to determine whether the defect candidate contained therein is a real defect or a false detection of no defect. Suitable automated analysis algorithms are disclosed in US patent applications 10 / 793,224 and 11 / 254,756, the contents of which are incorporated herein by reference. Preferably, the output of the automatic analysis algorithm indicating whether the defect candidate is an actual defect or a false detection of no defect is provided to the confirmation display control unit. This control preferably forms part of the defect analyzer subsystem 120.

If the defect candidate is identified as the actual defect by the algorithm analysis, the display control unit which is the quotation price confirms whether the operator also identified the defect candidate as the actual defect. This process is implemented by confirming that the operator has positively identified the defect. For example, the above verification process can be implemented by pressing a designated computer key, or by checking a time period during which an operator observes or inspects an image of a defect candidate. If this time interval is relatively short, for example, less than 5 seconds and typically less than 2 seconds, the confirmation display control section determines that the operator did not identify the defect candidate as the actual defect. If the algorithmic result and the operator's confirmation result are different from each other, an appropriate indication is provided. The appropriate indication may be a process of displaying the reflection image of the defect candidate back to the operator so that the operator can further inspect the defect. Displaying the reflected image again may be seamless for the operator (ie, a natural way that is not felt by any separate procedure). In addition, a warning may be provided informing of such a mismatch, and this warning may be additionally recorded for quality control or the like.

Following this process, verification is completed for each of the defect candidates in the desired set. After the verification is completed, the electrical circuits are passed on to further processing. For example, if all the defects are misdetected, the electrical circuit will go into an additional electrical circuit fabrication process such as micro-machining (ie, precision machining).

If some of the defect candidates are identified as actual defects, or if the automatic identification results do not match, the electrical circuit will have to undergo additional defect identification or repair processes.

1 is a simplified partial block diagram of an optical inspection system constructed and operative in accordance with one embodiment of the present invention.

2 is a simplified flowchart of an optical inspection method using the optical inspection system of FIG.

Claims (35)

In the optical inspection system of the electrical circuit element, The system includes an optical inspection function, an algorithmic inspection function, a display device, and a display controller, The optical inspection function provides an optical inspection output for one or more regions on the electrical circuit element being inspected, The algorithmic inspection function provides an algorithmic inspection output of the one or more regions, wherein the algorithmic inspection output indicates the presence of possible defects in the one or more regions, The display device provides an operator with a visual display of the one or more areas based on the optical inspection output, The display controller according to the detected operator behavior indicating that the defect has not been identified in the one or more areas, and in accordance with the algorithmic test output indicating the presence of a possible defect in the one or more areas. Providing an indication of a mismatch between the sensed operator behavior for the abnormal region and the algorithmic test output. The optical inspection system of claim 1, wherein the display controller operates the display device to once again provide the operator with a visual display of the one or more regions. The optical inspection system of claim 1, wherein the algorithmic inspection function comprises a fluorescence inspection function. 4. The optical inspection system of claim 3, wherein the fluorescence inspection function comprises a deep violet inspection function. 4. The optical inspection system of claim 3, wherein the fluorescence inspection function portion comprises an ultraviolet (UV) inspection function portion. The optical inspection system of claim 1, wherein the algorithmic inspection function unit comprises one or more inspection function units different from the functions used in the optical inspection function unit. 7. The method of claim 6, wherein the one or more inspection functions provide one or more of fluorescence, dark field, bright field, ultraviolet, and height inspection. Optical inspection system of the electric circuit element. The optical inspection system of claim 1, wherein the optical inspection function provides a reflection inspection function. The system of claim 1, wherein the system further comprises a defect analyzer, The defect analyzer is operative to receive one or more reference images for the one or more regions and the optical inspection output for the one or more regions, The defect analyzer provides an output indication of positions of defect candidates in the electrical circuit element being inspected to one or more of the algorithmic inspection function and the optical inspection function. . 10. The optical inspection system of claim 9, wherein the one or more reference images are derived from one or more computer file references. 10. The system of claim 9, wherein the one or more reference images are derived from one or more of a CAD file and a CAM file. The optical inspection system of claim 10, wherein the one or more computer file references comprise one or more binary images. 10. The optical inspection system of claim 9, wherein the at least one reference image is obtained from at least one printed circuit board known to be free of defects. The optical inspection system of claim 1, wherein the visual display includes one or more reflected images of the one or more regions. The optical inspection system of claim 1, wherein the sensed operator behavior comprises a behavior in which the operator observes the visual display for a time less than a specified time. 16. The system of claim 15, wherein said specified time is less than 5 seconds. 16. The optical inspection system according to claim 15, wherein the specified time is less than 2 seconds. 2. The optical inspection system of claim 1, wherein the detected operator behavior comprises receiving an indication when a computer key is pressed. In the optical inspection method of the electric circuit element, the method, Providing an optical inspection output of at least one region on the electrical circuit element under inspection, Providing an algorithmic inspection output of said at least one region, wherein said algorithmic inspection output indicates the presence or absence of a possible defect in said at least one region, Providing an operator with a visual display of said at least one area based on said optical inspection output, -Depending on the detected operator behavior indicating that a defect has not been identified in the one or more regions, and in accordance with the algorithmic inspection output indicating the presence of a possible defect in the one or more regions, Providing an indication of a mismatch between the algorithmic test output and the sensed operator behavior. Optical inspection method of an electric circuit element comprising a. 20. The method of claim 19, wherein providing an indication of inconsistency causes a display device to provide the operator with a visual display of the one or more regions again. 20. The method of claim 19, wherein providing an algorithmic test output comprises providing a fluorescence test output. 22. The method of claim 21, wherein providing a fluorescence test output comprises providing a deep violet test output. 22. The method of claim 21, wherein providing a fluorescence test output comprises providing an ultraviolet (UV) test output. 20. The method of claim 19, wherein providing an algorithmic test output includes providing one or more test outputs other than those provided in the optical test output. 25. The method of claim 24, wherein providing the one or more inspection outputs comprises providing one or more of fluorescence inspection output, doc field inspection output, bright field inspection output, ultraviolet inspection output, and height inspection output. Optical inspection method of the electric circuit element. 20. The method of claim 19, wherein providing an optical inspection output comprises providing a reflection inspection output. The method of claim 19, Receiving the optical inspection output of the at least one region, Receiving at least one reference image of the at least one area, Providing an output indication of the location of the defect candidates of the inspection circuit element under test Optical inspection method of an electrical circuit element, characterized in that it further comprises. 28. The method of claim 27, wherein receiving one or more reference images comprises deriving one or more reference images from one or more computer file references. 29. The method of claim 28, wherein receiving at least one reference image comprises deriving the at least one reference image from at least one of a CAD file and a CAM file. 28. The method of claim 27, wherein receiving at least one reference image comprises obtaining the at least one reference image from at least one printed circuit board known to be free of defects. 20. The method of claim 19, wherein providing a visual display comprises providing one or more reflected images of the one or more regions. 20. The method of claim 19, wherein the sensed operator behavior includes a step in which the operator observes the visual display for a time shorter than a specified time. 33. The method of claim 32, wherein the specified time is less than 5 seconds. 34. The method of claim 33, wherein the specified time is less than 2 seconds. 20. The method of claim 19, wherein the detected operator behavior comprises receiving an indication when a computer key is pressed.

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