BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electric-component mounting system arranged to mount electric components (including electronic components) on a circuit substrate such as a printed-wiring board, a method of obtaining relative positions of specific sections of the electric-component mounting system which influence the accuracy of mounting of the electric components, and a method and an apparatus of obtaining a positioning error of each electric component as held by a suction nozzle.

[0003] 2. Discussion of Related Art

[0004] Electric-component mounting systems often use a suction nozzle arranged to hold an electric component by suction under a negative pressure. Usually, the actual position of the electric component held by the suction nozzle deviates from the nominal position. In view of this positional deviation of the electric component, it has been practiced to detect an error of positioning of the electric component with respect to the suction nozzle by operating an image-taking device to take an image of the electric component as held by the suction nozzle, and compensate the position of the electric component for the detected positioning error before the electric component is mounted on the circuit substrate. The positioning error includes at least one of an error of positioning of the center position or other reference position of the electric component in a plane perpendicular to an axis of rotation of the suction nozzle, and an error of angular positioning of the electric component about the axis of rotation of the suction nozzle. The circuit substrate on which the electric components are mounted is usually also positioned by a substrate supporting device. However, the actual positions of pads in a circuit pattern formed on the circuit substrate, on which the electric components are to be mounted, more or less deviate from the nominal positions. In view of this deviation, it is practiced to form a fiducial mark on the circuit substrate upon formation of the circuit pattern, detect the positioning error of the circuit substrate by operating an image-taking device to take an image of the fiducial mark, estimate the positional deviation of the pads on the basis of the detected positioning error, and compensate the position of each electric component for the estimated positional deviation before the electric component is mounted on the corresponding pad.

[0005] To obtain the positioning error of the electric component with respect to the suction nozzle and the positioning error of the fiducial mark on the circuit substrate with respect to the substrate supporting device, it is necessary to know the positions of the electric component and the fiducial mark relative to the suction nozzle and the image-taking devices when the images of the electric component and the fiducial mark are taken by the image-taking devices. The positioning errors of the electric component and the fiducial mark may be obtained by detecting those relative positions using exclusively designed detecting devices, when the electric-component mounting system is assembled or inspected for maintenance purpose. In this case, the obtained positioning errors are used on an assumption that the detected relative positions are maintained in operation of the system. To obtain the positioning errors in this manner, the detecting devices are required to be complicated and tend to be expensive. Further, ballscrews used in relative-movement devices provided to move the suction nozzle, substrate supporting device and image-taking devices relative to each other undergo elongation and contraction due to a change in the temperature, and elastic deformation due to loads acting thereon. In addition, the machine frame of the electric-component mounting system, brackets which hold the image-taking devices and other portions of the system are also subject to deformation due to a temperature variation. Accordingly, the actual relative positions of the suction nozzle, substrate supporting device and image-taking devices may vary with respect to the detected relative positions, due to the elongation and contraction and elastic deformation of the ballscrews of the relative-movement devices, and deformation of the machine frame and brackets. The above-indicated elongation and contraction and deformation due to the temperature variation will be collectively referred to as “thermal deformation”.

[0006] It is further noted that the relative positions of the suction nozzle, substrate supporting device and image-taking devices may vary due to chronological changes of the individual elements of the electric-component mounting system, wearing of the elements during use, and displacements of the elements due to loosening of fastening or fixing devices used in the system. To reduce this variation of the relative positions in an electric-component mounting system which is required to assure a high degree of component mounting accuracy, it has been practiced to provide the system with linear encoders to detect the actual relative positions of the suction nozzle, substrate supporting device and image-taking devices, and/or form the brackets for supporting the image-taking devices, of highly rigid materials having a relatively low coefficient of thermal expansion, and/or design the lenses of the image-taking devices such that the lenses are highly resistant to vibrations. However, such measures inevitably result in an increase in the cost of manufacture of the electric-component mounting system, and cannot therefore be said to be completely satisfactory.

SUMMARY OF THE INVENTION

[0007] The present invention was made in view of the problems encountered in the prior art described above. It is therefore an object of the present invention to make it possible to accurately detect the error of positioning of the electric component with respect to the suction nozzle while minimizing an increase of the cost of manufacture of the electric-component mounting system, to improve the component mounting accuracy of the system, or to obtain the relative positions of those sections of the system which influence the component mounting accuracy.

[0008] The above object may be achieved according to any one of the following modes of the present invention in the form of a method of and an apparatus for detecting the positioning error of an electric component- to be mounted by an electric-component mounting system, a recording medium storing a control program for practicing the method of detecting the positioning error, a method of and an apparatus for obtaining the relative positions of selected sections of the electric-component mounting system, a recording medium storing a control program for practicing the method of obtaining the relative positions, a method of and a system of mounting an electric component on a circuit substrate, and a recording medium storing a control program for practicing the method of mounting the electric component. Each of the following modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.

[0009] (1) A method of detecting a positioning error of an electric component with respect to a suction nozzle by which the electric component is held by suction under a negative pressure, comprising:

[0010] a first image-taking step of concurrently taking an image of the suction nozzle and an image of at least one dog disposed in the vicinity of the suction nozzle:

[0011] a first data processing step of processing image data representative of the images of the suction nozzle and the at least one dog which have been taken in the first image-taking step, and obtaining and storing a relative position between the suction nozzle and the at least one dog;

[0012] a second image-taking step of taking an image of the electric component held by the suction nozzle and an image of the at least one dog; and

[0013] a second data processing step of obtaining the positioning on the basis of image data representative of the images of the electric component and the at least one dog which have been taken in the second image-taking step, and the relative position between the suction nozzle and the at least one dog obtained in the first data processing step.

[0014] The positioning error of the electric component with respect to the suction nozzle includes a center position error of the center position or other reference position of the electric component in a plane perpendicular to a centerline of the suction nozzle, and an angular positioning error of the electric component about the centerline (axis of rotation) of the suction nozzle.

[0015] In the second data processing step, the position of the at least one dog is first obtained, and the position of the suction nozzle is obtained on the basis of the obtained position of the at least one dog, and the relative position between the at least one dog and the suction nozzle obtained in the first data processing step, so that the position (positioning error) of the electric component with respect to the thus obtained position of the suction nozzle is obtained. Alternatively, the relative position between the at least one dog and the electric component is first obtained, and the positioning error of the electric component with respect to the suction nozzle is obtained on the basis of the obtained relative position of the at least one dog and the electric component, and the relative position between the at least one dog and the suction nozzle obtained in the first data processing step.

[0016] An image-taking device used to take images of the suction nozzle, at least one dog and electric component may consist of only a camera such as a CCD camera, or both a camera, and a suitable waveguide device which includes at least one light reflecting surface or a multiplicity of optical fibers, for guiding a light along a suitable path, to be incident upon the camera. In the former case, the camera is oriented so as to be opposed to the end face of the suction nozzle. In the latter case, the waveguide device is arranged such that the light is incident upon the camera.

[0017] In the method according to the above mode (1) of the present invention, the relative position between the at least one dog and the suction nozzle is detected before the electric component is held by the suction nozzle, and then the relative position between the electric component and the at least one dog is obtained, since the image of the electric component held by the suction nozzle cannot be taken in the presence of the suction nozzle hiding the electric component. Thus, the position of the suction nozzle can be accurately estimated on the basis of the detected position of the at least one dog and the detected relative position between the at least one dog and the suction nozzle. The deviation of the electric component with respect to the estimated position of the suction nozzle can be considered to be the actual positioning error of the electric component with respect to the suction nozzle, as long as the relative position between the suction nozzle and the at least one dog remains unchanged. For instance, the at least one dog is supported by a support member holding the suction nozzle, or by a structure which holds the support member such that the support member is rotatable or axially movable relative to the structure. In this instance, it is comparatively easy to substantially prevent a change in the relative position between the suction nozzle and the at least one dog, which would take place due to thermal deformation, elastic deformation, chronological change and wear of those support member or structure. Accordingly, the positioning error of the electric component with respect to the position of the suction nozzle as estimated on the basis of the position of the at least one dog can be considered to be the actual positioning error of the electric component with respect to the actual position of the suction nozzle, so that the actual position of the electric component relative to the suction nozzle is compensated for the thus detected positioning error of the electric component, as well as for an error in the relative position between the suction nozzle and the image-taking device, which error would take place due to the above-indicated reasons such as the thermal and elastic deformation. Therefore, the present method permits mounting of the electric component on a circuit substrate with a high degree of positioning accuracy.

[0018] (2) A method according to the above mode (1), wherein the first image-taking step comprises a step of rotating the suction nozzle at least once and taking images of an end face of the suction nozzle placed in at least two angular positions thereof, and the first data processing step comprises a step of obtaining an axis of rotation of the suction nozzle on the basis of the images of the end face of the suction nozzles in the at least two angular positions.

[0019] For instance, the suction nozzle is rotated by 180°, and the two images of the end face of the suction nozzle are taken before and after the 180° rotation of the suction nozzle. In this case, the coordinate values of the axis of rotation of the suction nozzle are obtained by averaging the coordinate values of the center position of the end face of the suction nozzle as obtained from the two images. Alternatively, the suction nozzle is rotated three times in angular increment of 90°, so that four images of the end face of the suction nozzle placed in the four angular positions of 0°, 90°, 180° and 270° are taken. In this case, the coordinate values of the rotation axis of the suction nozzle are obtained by averaging the coordinate values of the center position of the end face of the suction nozzle as obtained from the four images. Where the images of the end face of the suction nozzle in at least three angular positions are taken, these angular positions need not be equiangularly spaced from each other. The axis of rotation of the suction nozzle is obtained as the center of a circle on which the center positions of the end face of the suction nozzle in the obtained images lie on the circle.

[0020] Where the suction nozzle is not rotatable, the position of the end face of the suction nozzle can be regarded as the position of the suction nozzle when the electric component is mounted on the circuit substrate. Where the suction nozzle is rotatable to permit the mounting of the electric component on the circuit substrate, at any desired angular position of the electric suction nozzle must be used as the position of the suction nozzle when the electric component is mounted on the circuit substrate. Otherwise, the accuracy of the position at which the electric component is mounted on the circuit substrate is deteriorated.

[0021] (3) A method according to the above mode (1) or (2), wherein the at least one dog consists of a plurality of dogs, and images of the plurality of dogs are taken in the first image-taking step, and an inclination of an imaging area in which the images of the dogs are formed is obtained on the basis of a relative position of the plurality of dogs in the first data processing step.

[0022] A dog device consisting of at least one dog may be inclined with respect to the imaging area due to assembling errors and thermal deformation of the image-taking device and a support structure holding the image-taking device. This inclination may be detected where the dog device consists of two or more dogs. For example, the dog device consists of two dogs disposed such that images of the two dogs are formed at two adjacent corners of the imaging area of a first image-taking device, which corners are spaced from each other in a direction exactly parallel to the X-axis or Y-axis direction of the imaging area. In this case, a straight line passing predetermined reference points such as apexes of the two dogs can be used as a reference for detecting the inclination of the first image-taking device (inclination of its imaging area). Alternatively, the angle of inclination of the above-indicated straight line passing the reference points of the two dogs with respect to the X-axis or angle of inclination is used as the reference for detecting the inclination of the first image-taking device. Further, the inclination of the straight line passing the reference points can be detected by utilizing the function of the electric-component mounting system, for example, by utilizing a fiducial chip, the first image-taking device and a second image-taking device, as discussed later in the following DESCRIPTION OF THE PREFERRED EMBODIMENTS. The dog device per se may be inclined due to the assembling error and thermal deformation of a support device holding the dog. The method indicated above permits detection of the inclination of the dog device, by utilizing the straight line passing the reference points of the two dogs as the reference for detecting the inclination of the imaging area of the first image-taking device. Further, the use of the fiducial chip permits detection of the inclination of the second image-taking device with respect to the first image-taking device. Although the use of a single dog having a comparatively large size and a shape suitable for detecting its inclination permits detection of the inclination of the imaging area, the comparatively large dog should not be hidden by the electric component held by the suction nozzle, in order to permit the dog to perform the assigned function. In this respect, it is preferable to use a plurality of comparatively small dogs which are disposed so that the images of the dogs are formed at peripheral portions of the imaging area, desirably, at corner portions of the rectangular imaging area.

[0023] (4) A method of obtaining relative positions of a plurality of sections of an electric-component mounting system wherein an electric component is held by suction by a suction nozzle under a negative pressure and is mounted on a circuit substrate, the plurality of sections influencing an accuracy of mounting of the electric component on the circuit substrate, comprising:

[0024] a first image-taking step of operating a first image-taking device to concurrently take an image of said suction nozzle and an image of at least one dog disposed in the vicinity of said suction nozzle;

[0025] a first data processing step of processing image data representative of the images of the suction nozzle and the at least one dog which have been taken in the first image-taking step, and obtaining and storing a relative position between the suction nozzle and the at least one dog;

[0026] a second image-taking step of operating the second image-taking device to concurrently take an image of a fiducial chip as held by the suction nozzle and an image of the at least one dog;

[0027] a second data processing step of obtaining a positioning error of the fiducial chip with respect to the suction nozzle, on the basis of image data representative of the images of the fiducial chip and the at least one dog, and the relative position between the suction nozzle and the at least one dog obtained in the first data processing step;

[0028] a chip-mounting step of moving the suction nozzle and a circuit-substrate support device supporting the circuit substrate, relative to each other, and placing the fiducial chip on a mounting surface which is disposed immovably relative to the circuit-substrate support device;

[0029] a third image-taking step of operating a second image-taking device to take an image of the fiducial chip placed on the mounting surface; and

[0030] a third data processing step of obtaining relative positions among the suction nozzle and the first and second image-taking devices, on the basis of image data representative of the image of the fiducial chip taken in the third image-taking step,

[0031] and wherein the fiducial chip is placed on the mounting surface in the chip-mounting step after a relative position between the suction nozzle and the circuit-substrate support device is compensated for the positioning error of the fiducial chip with respect to the suction nozzle which has been obtained in the second data processing step, or the relative positions among the suction nozzle, and the first and second image-taking devices are obtained in the third data processing step, on the basis of the positioning error of the fiducial chip obtained in the second data processing step, as well as the image data representative of the image of the fiducial chip taken in the third image-taking step.

[0032] In the electric-component mounting system provided with the first image-taking device and the second image-taking device, the positioning error of the electric component with respect to the suction nozzle is generally detected on the basis of positioning error of the circuit substrate with respect to the circuit-substrate support device is generally detected on the basis of image data obtained by the second image-taking device, so that the relative position between the suction nozzle and the circuit-substrate support device is compensated for the positioning errors of the electric component and the circuit substrate when the electric component is mounted on the circuit substrate according to a component mounting control program. In the presence of errors between the suction nozzle and the first and second image-taking devices, the accuracy of mounting of the electric component on the circuit substrate is deteriorated. According to the present method, the relative positions among the suction nozzle and the first and second image-taking devices, for instance, positioning errors of two of those three elements relative to the other one element are detected are detected, and the relative position between the suction nozzle and the circuit substrate is compensated for the detected positioning errors as well as the positioning errors of the electric component and the circuit-substrate support device, before the electric component is mounted on the circuit substrate, whereby the accuracy of mounting of the electric component on the circuit substrate is improved.

[0033] The fiducial chip is a chip designed exclusively for obtaining the relative positions of the suction nozzle and the first and second image-taking devices. Alternatively, one of electric components to be mounted on the circuit substrate is utilized as the fiducial chip. In the former case, the fiducial chip is manufactured so as to have high degrees of geometrical and dimensional accuracy and optical properties suitable for the detection, so that the accuracy of detection of the above-indicated relative positions can be easily improved.

[0034] The mounting surface may be provided permanently on a selected component or element of the mounting system, for instance, may be temporarily provided on the circuit substrate on which the electric component is to be mounted. All that is required for the mounting surface is that the mounting surface is immovable or fixed in position relative to the circuit-substrate support device in the chip-mounting step and the third image-taking step.

[0035] The method of obtaining the relative positions according to the above mode (4) of the invention may be practiced upon assembling or maintenance inspection of the electronic-component mounting system, or at a suitable point of time during the component mounting operation. In the former case, the component mounting control program is adjusted or changed on the basis of the obtained relative positions, so as to improve the component mounting accuracy of the electric-component mounting system. In the latter case, changes in the relative positions among the appropriate sections of the mounting system due to thermal deformation are obtained, and the relative position between the suction nozzle and the circuit-substrate support device is compensated on the basis of the detected changes, for thereby further improving the component mounting accuracy of the system. The present method assures a sufficiently high degree of component mounting accuracy even where the component mounting operation is initiated before the operating temperatures of the individual sections of the system have become stable.

[0036] (5) A method of mounting an electric component on a circuit substrate, comprising:

[0037] a method of obtaining relative positions of a plurality of sections of an electric-component mounting system, according to the above mode (4) of this invention;

[0038] a fourth image-taking step of operating the second image-taking device to take an image of a fiducial mark provided on the circuit substrate supported by the circuit-substrate support device;

[0039] a fourth data processing step of obtaining a positioning error of the circuit substrate on the basis of image data representative of the image of the fiducial mark taken in the fourth image-taking step;

[0040] a fifth image-taking step of operating the suction nozzle to hold the electric component, and operating the first image-taking device to take an image of the electric component held by the suction nozzle: and

[0041] a component-mounting step of compensating the relative position between the circuit-substrate support device and the suction nozzle, on the basis of image data representative of the image of the electric component obtained in the fifth image-taking step, the relative positions among the suction nozzle and the first and second image-taking devices, and the positioning error of the circuit substrate obtained in the fourth data processing step, so that the electric component is mounted at a predetermined position on the circuit substrate.

[0042] The positioning error of the circuit substrate (positioning error of the fiducial mark) obtained in the fourth data processing step indicated above may be an error of positioning of the circuit substrate within the imaging area of the second image-taking device (positioning error of the circuit substrate with respect to the second image-taking device), or a deviation of the actual position of the circuit substrate with respect to a nominal position of the circuit substrate. In the former case, the positioning error of the circuit substrate with respect to its nominal position may be represented, for example, by a sum of a positioning error of the circuit substrate with respect to the second image-taking device, and a positioning error of the second image-taking device with respect to the first image-taking device, provided the position of the first image-taking device represents the reference position of the electric-component mounting system as a whole.

[0043] (6) A recording medium storing a control program for practicing the method according to any one of the above modes (1)-(3), such that the control program is readable by a computer.

[0044] (7) A recording medium storing a control program for practicing the method according to the above mode (4), such that the control program is readable by a computer.

[0045] (8) A recording medium storing a control program for practicing the method according to the above mode (5), such that the control program is readable by a computer.

[0046] (9) An apparatus for detecting a positioning error of an electric component with respect to a suction nozzle by which the electric component is held by suction under a negative pressure, comprising:

[0047] an image-taking device operable to take an image of the suction nozzle in a direction of extension of a centerline of the suction nozzle;

[0048] at least one dog each disposed at a position at which an image of the at least one dog can be taken together with an image of the suction nozzle by the image-taking device;

[0049] an image-taking control device operable to operate the image-taking device to concurrently take the images of the suction nozzle and the at least one dog, and to concurrently take an image of the electric component as held by the suction nozzle and the image of the at least one dog; and

[0050] a data processing device operable to obtain a relative position between the suction nozzle and the at least one dog, on the basis of the images of the suction nozzle and the at least one dog which have been concurrently taken, and obtaining the positioning error of the electric component with respect to the suction nozzle, on the basis of the images of the electric component and the at least one dog which have been concurrently taken, and the relative position between the suction nozzle and the at least one dog.

[0051] The apparatus according to the above mode 9 ) of the invention is suitable for practicing the method according to the above mode (1) of detecting the positioning error of the electric component with respect to the suction nozzle.

[0052] (10) An apparatus according to the above mode (9), wherein the image-taking control device comprises a plural-imaging control portion operable to rotate the suction nozzle at least once and take images of an end face of the suction nozzle placed in at least two angular positions thereof, and a rotation-axis obtaining portion operable to obtain an axis of rotation of the suction nozzle on the basis of the images of the end face of the suction nozzle in the at least two angular positions.

[0053] (11) An apparatus according to the above mode (9) or (10), wherein the at least one dog consists of a plurality of dogs which are located such that images of the plurality of dogs are formed at respective peripheral portions of an imaging area of the image-taking device, when the images of the dogs are taken by the image-taking device, concurrently with the image of the suction nozzle.

[0054] (12) An apparatus according to any one of the above modes (9)-(11), wherein the data processing device obtains an inclination of the imaging area of the image-taking device on the basis of the images of the plurality of dogs.

[0055] (13) An apparatus according to any one of the above modes (9)-(12), wherein each of the at least one dog has a generally rectangular shape, and includes a sensed portion having an apex which is defined by adjacent two sides of a rectangle of the generally rectangular shape.

[0056] The apex defined by the adjacent two sides of the rectangle of the generally rectangular shape of the sensed portion of each dog can be accurately detected, as the reference position of the dog.

[0057] (14) An apparatus according to the above mode (13), wherein the sensed portion has two chamfered surfaces formed along the adjacent two sides, so as to provide two sharp edges of an acute angle which intersect each other at right angles at the apex.

[0058] Where the a portion of the dog defining the adjacent two sides of the sensed portion have a relatively large thickness, sharp images of the two sides cannot be obtained by the image-taking device. In this respect, the apex is ideally defined by a point of intersection of two sharp edges of an actuate angle which are provided by the two chamfered surfaces so that the thickness at the apex is substantially zero, for accurate detection of the dog. From the standpoint of ease of manufacture, durability and safety of the dog, however, the portion defining the adjacent two sides of the sensed portion may have an extremely small thickness value.

[0059] (15) An apparatus for obtaining relative positions of a suction nozzle, a first image-taking device and a second image-taking device, in an electric-component mounting system wherein an electric component is held by suction by the suction nozzle and is mounted on a circuit substrate supported by a circuit-substrate support device, the first image-taking device being operable to take an image of the suction nozzle in a direction of extension of a centerline of the suction nozzle, and the second image-taking device being operable to take an image of a fiducial mark provided on the circuit substrate, the electric-component mounting system further including (a) a component supply device for supplying the suction nozzle with the electric component, (b) a relative-movement device for moving the component supply device, the suction nozzle and the circuit-substrate support device relative to each other, (c) a component-mounting control device for controlling the relative-movement device and the suction nozzle such that the electric component received by the suction nozzle from the component supply device is mounted at a predetermined position on the circuit substrate supported by the circuit-substrate support device, and (d) a data processing device for processing image data representative of the images taken by the first and second image-taking device, the apparatus comprising:

[0060] at least one dog located such that an image of each of the at least one dog can be taken by the first image-taking device, together with the image of the suction nozzle;

[0061] image-taking control means for controlling the first image-taking device to concurrently take the images of the suction nozzle and the at least one dog, and to concurrently take an image of a fiducial chip held by the suction nozzle and the image of the each dog;

[0062] positioning-error obtaining means for obtaining-a relative position between the suction nozzle and the at least one dog, on the basis of the images of the suction nozzle and the at least one dog which have been concurrently taken under the control of the image-taking control means, the positioning-error obtaining means obtaining a positioning error of the fiducial chip with respect to the suction nozzle, on the basis of the images of the fiducial chip and the at least one dog which have been concurrently taken, and the relative position between the suction nozzle and the at least one dog;

[0063] fiducial-chip mounting control means for moving the suction nozzle and the circuit-substrate support device, and placing the fiducial chip on a mounting surface which is disposed immovably relative to the circuit-substrate support device;

[0064] fiducial-chip imaging control means for operating the second image-taking device to take the image of the fiducial chip placed on the mounting surface; and

[0065] relative-position obtaining means for obtaining relative positions among the suction nozzle and the first and second image-taking devices, on the basis of image data representative of the image of said fiducial chip,

[0066] and wherein the fiducial-chip mounting control means is operable to compensate a relative position between the suction nozzle and the circuit-substrate support device for the positioning error of the fiducial chip with respect to the suction nozzle before the fiducial chip is placed on the mounting surface, or the relative-position obtaining means is operable to obtain the relative positions among the suction nozzle and the first and second image-taking devices on the basis of the positioning error of the fiducial chip, as well as the image data representative of the image of the fiducial chip taken under the control of the fiducial-chip imaging control means.

[0067] The apparatus constructed according to the above mode (15) is suitable for practicing the method of obtaining the relative position according to the above mode (4).

[0068] (16) An electric-component mounting system including (a) a component supply device for supplying an electric component, (b) a suction nozzle for holding the electric component by suction, (c) a circuit-substrate support device for supporting a circuit substrate, (d) a relative-movement device for moving the component supply device, the suction nozzle and the circuit-substrate support device, relative to each other, (e) a component-mounting control device for controlling the relative-movement device and the suction nozzle such that the electric component received by the suction nozzle from the component supply device is mounted at a predetermined position on the circuit substrate supported by the circuit-substrate support device, (f) a first image-taking device operable to take an image of the suction nozzle in a direction of extension of a centerline of the suction nozzle, (g) a second image-taking device operable to take an image of a fiducial mark provided on the circuit substrate supported by the circuit-substrate support device, and (h) a data processing device for processing image data representative of the images taken by the first and second image-taking devices, the electric-component mounting system comprising:

[0069] at least one dog located such that an image of each of the at least one dog can be taken by the first image-taking device, together with the image of the suction nozzle;

[0070] image-taking control means for controlling the first image-taking device to concurrently take the images of the suction nozzle and the at least one dog, and to concurrently take an image of a fiducial chip held by the suction nozzle and the image of the each dog;

[0071] positioning-error obtaining means for obtaining a relative position between the suction nozzle and the at least one dog, on the basis of the images of the suction nozzle and the at least one dog which have been concurrently taken under the control of the image-taking control means, the positioning-error obtaining a positioning error of the fiducial chip with respect to the suction nozzle, on the basis of the images of the fiducial chip and the at least one dog which have been concurrently taken, and the relative position between the suction nozzle and the at least one dog;

[0072] fiducial-chip mounting control means for moving the suction nozzle and the circuit-substrate support device, and placing the fiducial chip on a mounting surface which is disposed immovably relative to the circuit-substrate support device;

[0073] fiducial-chip imaging control means for operating the second image-taking device to take the image of the fiducial chip placed on the mounting surface;

[0074] relative-position obtaining means for obtaining relative positions among the suction nozzle and the first and second image-taking devices, on the basis of image data representative of the image of the fiducial chip;

[0075] the fiducial-chip mounting control means being operable to compensate a relative position between the suction nozzle and the circuit-substrate support device for the positioning error of the fiducial chip with respect to the suction nozzle before the fiducial chip is placed on the mounting surface, or the relative-position obtaining means being operable to obtain the relative positions among the suction nozzle and the first and second image-taking devices on the basis of the positioning error of the fiducial chip, as well as the image data representative of the image of the fiducial chip taken under the control of the fiducial-chip imaging control means;

[0076] fiducial-mark imaging control means for operating the second image-taking device to take an image of the fiducial mark provided on the circuit substrate supported by the circuit-substrate support device;

[0077] substrate-positioning-error obtaining means for obtaining a positioning error of the circuit substrate on the basis of image data representative of the image of the fiducial mark taken under the control of the fiducial-mark imaging control means;

[0078] electric-component imaging control means for operating the suction nozzle to hold the electric component, and operating the first image-taking device to take an image of the electric component held by the suction nozzle; and

[0079] mounting control means for compensating the relative position between the circuit-substrate support device and the suction nozzle, on the basis of image data representative of the image of the electric component, the relative positions among the suction nozzle and the first and second image-taking devices, and the positioning error of the circuit substrate obtained by the substrate-positioning-error obtaining means, so that the electric component is mounted at the predetermined position on the circuit substrate.

[0080] The electric-component mounting system constructed according to the above mode (16) is suitable for practicing the method according to the above mode (5).

[0081] (17) An electric-component mounting system according to the above mode (16), wherein the relative-movement device includes an X-axis slide movable in an X-axis direction in a plane parallel to a surface of the circuit substrate supported by the circuit substrate support device, and a Y-axis slide which is supported by the X-axis slide movably in the plane in a Y-axis direction perpendicular to the X-axis direction and which holds the suction nozzle, and the first image-taking device is fixedly disposed on the X-axis slide.

[0082] (18) An electric-component mounting system according to the above mode (16), wherein the relative-movement device includes an X-axis slide movable in an X-axis direction in a plane parallel to a surface of the circuit substrate supported by the circuit substrate support device, and a Y-axis slide which is supported by the X-axis slide movably in the plane in a Y-axis direction perpendicular to the X-axis direction and which holds the suction nozzle, and the first image-taking device is fixed to a stationary member which supports the X-axis slide.

[0083] (19) An electric-component mounting system according to any one of the above modes (16)-(18), wherein the relative-movement device includes an X-axis slide movable in an X-axis direction in a plane parallel to a surface of the circuit substrate supported by the circuit substrate support device, and a Y-axis slide which is supported by the X-axis slide movably in the plane in a Y-axis direction perpendicular to the X-axis direction and which holds the suction nozzle, and the second image-taking device is fixedly disposed on the Y-axis slide.

[0084] (20) An electric-component mounting system according to any one of the above modes (17)-(19), wherein the mounting surface includes a first mounting surface located at a first position near zero points of the X-axis slide and the Y-axis slide, and a second mounting surface located at a second position remote from the zero points of the X-axis slide and the Y-axis slide, and the fiducial-chip mounting control means is operable to place the fiducial chip on both of the first and second mounting surfaces.

[0085] (21) An electric-component mounting system according to the above mode (16), wherein the relative-movement device includes an angular positioning device operable to turn the suction nozzle about a turning axis such that the suction nozzle is stopped at a plurality of working stations arranged along a path of turning of the suction nozzle, and an XY positioning device operable to move the circuit-substrate support device in mutually perpendicular X-axis and Y-axis directions in a plane parallel to a surface of the circuit substrate supported by the circuit-substrate support device, and the first image-taking device is fixedly disposed so as to be opposed to an end face of the suction nozzle stopped at one of the plurality working stations, while the second image-taking device is fixedly disposed so as to be opposed to the circuit substrate supported on the circuit-substrate support device.

[0086] (22) An electric-component mounting system according to the above mode (21), wherein the XY positioning device includes an X-axis slide movable in the X-axis direction, and a Y-axis slide movable in the Y-axis direction, and the mounting surface includes a first mounting surface located at a first position near zero points of the X-axis slide and the Y-axis slide, and a second mounting surface located at a second position remote from the zero points of the X-axis slide and the Y-axis slide, and the fiducial-chip mounting control means is operable to place the fiducial chip on both of the first and second mounting surfaces.