Metal working – Means to assemble or disassemble – Means to assemble electrical device
Reexamination Certificate
2002-01-10
2004-10-26
Trinh, Minh (Department: 3729)
Metal working
Means to assemble or disassemble
Means to assemble electrical device
C029S743000, C029S739000, C029S721000, C029SDIG004, C029S833000, C414S737000, C901S047000
Reexamination Certificate
active
06807726
ABSTRACT:
This application is based on Japanese Patent Application No. 2001-007274 filed on Jan. 16, 2001, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an electric-component mounting system, and more particularly to techniques for improving accuracy of mounting of electronic components and other electric components.
2. Discussion of Related Art
An electric-component mounting system is constructed and arranged to mount various kinds of electric components on a board or substrate such as printed-wiring boards. The electric components include resistors, electronic components of chip type such as capacitors, electronic components of flat-package type, and various other types of electronic components with or without leads, such as connectors
An electric-component mounting system of such type is generally arranged to hold each electric component by suction, move and position the electric component to and at a predetermined position above a substrate on which the electric components are to be mounted, and mount or place the electric component on the substrate.
Described in detail, the electric-component mounting system of the type described above includes (a) a main body, (b) a movable portion, (c) a drive device, (d) a motion-transmitting member which extends along a straight line and which is operated by the drive device to apply a linear motion along the straight line, to the movable portion, and (e) a controller which is arranged to apply a drive signal to the drive device for controlling the drive device, so as to control the position of the movable portion in the direction of its linear motion. For example, the motion-transmitting member is a ballscrew which is rotated by the drive device such that the ballscrew is not axially movable and such that a rotary motion of the ballscrew is converted into a linear motion of the movable portion. Another example of the motion-transmitting member is a non-rotatable ballscrew which meshes with a ballnut such that a rotary motion of the ballnut is converted into a linear motion of the movable portion. A further example of the motion-transmitting member is a linear stator which slidably engages a slider and whose magnetic force is converted into a linear motion of the slider. The stator and the slider cooperate to constitute a linear motion.
For instance, the electric-component mounting system described above may be arranged such that the movable portion includes a component holder arranged to hold an electric component by suction, and the main body has an image-taking device fixed thereto, to take an image of the electric component as held by the component holder. The controller indicated above is arranged to process the image of the electric component taken by the image-taking device, for detecting an actual hold-position of the electric component as held by the component holder. The controller obtains a positioning error of the electric component, which is an error of the detected actual position of the electric component with respect to a nominal hold-position of the electric component. The controller is further arranged to determine the drive signal to be applied to the drive device, so that the actual mounting position of the electric component is not influenced by the obtained positioning error of the electric component.
The electric-component mounting system described above may be arranged such that the movable portion includes a movable member which is moved relative to the substrate and which carries an another image-taking device fixed thereto, so that this image-taking device is moved with the movable member, to take an image of a fiducial mark provided on the substrate. The controller processes the image of the fiducial mark taken by this image-taking device, to detect an actual position of the substrate, and obtains a positioning error of the substrate, which is an error of the detected actual position with respect to a nominal position of the substrate.
Alternatively, the electric-component mounting system may be arranged to include a plurality of movable portions in the form of a component holder for holding an electric component, and a movable member, and further include a first image-taking device fixed on the main body, and a second image-taking device fixed on the movable member. The first image-taking device is arranged to an image of the electric component as held by the component holder, while the second image-taking device is arranged to taken an image of a fiducial mark provided on the substrate. In this case, the controller indicated above is arranged to process the image of the component taken by the first image-taking device, for detecting the actual hold-position of the electric component as held by the component holder, and obtaining the positioning error of the electric component, which is an error of the detected actual position of the electric component with respect to the nominal hold-position of the electric component. The controller is further arranged to process the image of the fiducial mark taken by the second image-taking device, for detecting the actual position of the substrate, and obtaining the positioning error of the substrate, which is an error of the detected actual position with respect to the nominal position of the substrate. The controller is further arranged to determine the drive signal to be applied to the drive device, so that the actual mounting position of the electric component is not influenced by the obtained two positioning errors, that is, the positioning errors of the electric component and the substrate.
In the electric-component mounting systems which have been described, the drive device usually includes servo-amplifiers, electric motors and other electric devices that generate operating heat, and the movable portion and the motion-transmitting member generate friction heat due to relative movement therebetween. Accordingly, the main body and the motion-transmitting member are inevitably heated and subject to thermal expansion. This thermal expansion causes deterioration of accuracy of mounting of the electric component by the electric-component mounting system.
For reducing the deterioration of the mounting accuracy of the electric component due to the thermal expansion, it has been a conventional practice to perform a warm-up or idling operation of the electric-component mounting system prior to each production run of the system, for positively inducing the thermal expansion of the system. This warm-up operation is desirably continued until the amount of thermal expansion of the system is substantially saturated.
Conventionally, an image of the fiducial mark is taken by the appropriate image-taking device described above, after the warm-up operation, to detect the actual position of the fiducial mark, that is, to obtain the positioning error of the substrate, namely, an error of the actual position of the substrate with respect to the nominal position. In the subsequent production run of the system, the drive signal to be applied to the drive device is compensated for the positioning error obtained on the basis of the image of the fiducial mark immediately after the warm-up operation.
The conventional compensation of the drive signal described above is effective to reduce an influence of the positioning error due to the thermal expansion of the electric-component mounting system, on the actual mounting position of the electric component on the substrate. However, the conventional compensation is not satisfactory to perfectly eliminate the influence of the positioning error due to the thermal expansion. This aspect will be described in detail with respect to the thermal expansion of the ballscrew used as the motion-transmitting member.
Where the positioning error of the fiducial mark is detected on the basis of the image of the mark taken by the image-taking device, as described above, the detected positioning error include an error component due to the thermal expansio
Iisaka Jun
Kondo Toshihiro
Shimizu Koji
Tanizaki Masahiro
Fuji Machine Mfg. Co. Ltd.
Oliff & Berridg,e PLC
Trinh Minh
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