Metal working – Means to assemble or disassemble – With signal – scale – illuminator – or optical viewer
Reexamination Certificate
2000-07-14
2003-10-21
Eley, Timothy V. (Department: 3724)
Metal working
Means to assemble or disassemble
With signal, scale, illuminator, or optical viewer
C029S740000, C029S743000
Reexamination Certificate
active
06634091
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a part mounter and a method for mounting parts, and more particularly, to a part mounter and a method for mounting parts by which the required time and the distance equipment must move for mounting parts is minimized and the position of the parts is precisely recognized.
2. Description of the Related Art
In general, electronic parts such as semiconductor packages are mounted on a printed circuit board by using a part mounter. The part mounter picks up electronic parts supplied by a part supply portion such as a tray feeder or a tape feeder using vacuum suction and mounts the electronic parts at predetermined positions on the printed circuit board. Here, a head unit moves the electronic part to an image sensor to obtain information on the posture of the part held by a suction nozzle. As the image sensor, a vision camera (a line CCD or an area CCD) is used. The image sensor detects state of the part held by the part suction portion so that information on the posture of the part is obtained. The part suction portion corrects the posture of the held part according to the image information and then mounts the part on the printed circuit board.
FIG. 1
is a perspective view showing the structure of a typical part mounter. Referring to the drawing, the part mounter includes a first Y-axis
12
and a second Y-axis
13
, an X-axis
11
moving along the first and second Y-axes
12
and
13
, and a head unit
14
installed to be capable of moving along the X-axis
11
. A suction nozzle
15
is installed at the head unit
14
to be capable of rotating and moving up and down. A printed circuit board (PCB)
25
is transferred by a conveyer
19
to the position of a part to be mounted. The head unit
14
moves between part feeders
18
a
,
18
b
,
18
c
,
18
d
and
18
e
, and the PCB
25
. The suction nozzle
15
moves up and down and/or rotates to hold a part and mounts it on the PCB
25
. At least one among the part feeders
18
a
,
18
b
,
18
c
,
18
d
and
18
e
may be a tape feeder or a tray. During a mounting process, the head unit
14
passes above an image sensor
16
. The image sensor
16
is fixed at one side of the part mounter and detects the part held by the suction nozzle
15
so that it corrects a positional error generated when a part is held by the suction nozzle
15
. The image sensor
16
, for example, may have an image detecting device such as a vision camera (a line CCD or an area CCD).
FIG. 2
is a view schematically showing the path along which the head unit
14
shown in
FIG. 1
moves. Referring to the drawing, the suction nozzle
15
of the head unit
14
picks up a part from the part feeders
18
a
,
18
b
,
18
c
,
18
d
and
18
e
and then moves to the position directly above the image sensor
16
. The image sensor
16
senses the part held by the suction nozzle
15
. Through a detecting process performed by the image sensor
16
, an error generated when the part is held by the suction nozzle
15
can be recognized. Next, the head unit moves above a mounting position P on the PCB
25
. The suction nozzle
15
of the head unit
14
descends and mounts the part at the mounting position P of the PCB
25
. Here, to correct an error recognized through the sensing process, the head unit
14
changes its position in the coordinate system or the suction nozzle
15
rotates and then the part is mounted.
In the part mounter having the above structure, since the head unit
14
must travel from the part feeders
18
a
,
18
b
,
18
c
,
18
d
and
18
e
to the part mounting position P on the PCB
25
through the image sensor
16
, the path of movement is long and complicated. That is, since the image sensor
16
is fixed at a particular position, the head unit
14
must move to the position directly above the image sensor
16
so as to sense the state of the held part.
FIG. 3
is a view showing an image of a state in which a part is held by the suction nozzle
15
, which is taken by an image sensing apparatus. Referring to the drawing, the center of the suction nozzle
15
matches the central point A of an image
121
. That is, when the suction nozzle
15
picks up a part
111
and moves just above the image sensor
16
, the center of the suction nozzle
15
is designed to match the center of the image sensor
16
. Thus, when a sensing process is performed by the image sensor
16
, the center point A of the image
121
substantially matches the center of the suction nozzle
15
. This is because a typical image recognition apparatus is fixed at one side of a part supply portion of a part mounter and the head unit
14
moves to a particular position after moving along a set path, that is, the center of the suction nozzle
15
matches the center of the image
121
.
When the image sensing is performed after the suction nozzle
15
has picked up a part, the positional information of the central point O of a part is recognized with information on the size and shape of the part. Next, information on the tilt of the part is recognized by the information on the shape of the part. As shown in
FIG. 3
, recognizing the distance separated in the X direction and Y direction between the central point A of the image
121
and the central point O of the part
111
, and a rotational degree &thgr; is recognized and the separated distance and the rotational degree are compensated for.
However, to correct the error generated when the part is held, the image sensor
16
must be maintained in a fixed state. This is because the central point of the suction nozzle
14
must match the central point A of the monitor
121
to recognize the error when suctioning the part. Thus, if the central point of the suction nozzle
14
does not match the central point of the image
121
during the sensing process, performing correction an error is not possible. The positional information with respect to the nozzle is indirectly obtained and it is assumed that the above preconditions are met. Also, at least one of the image sensor
16
and the head unit
14
must be fixed.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a part mounter and a method for mounting parts so that part mounting work is performed quickly while correcting an error generated.
Accordingly, to achieve the above objects, there is provided a part mounter comprising a plurality of part feeders for storing and supplying a plurality of parts, a conveyer for transferring a printed circuit board, a head unit capable of moving and having a suction nozzle for picking up a part from the part feeders and mounting the part on the printed circuit board on the conveyer, and an image sensor installed to move along a path crossing a movement path of the head unit, for detecting an image of the part held by the suction nozzle.
It is preferred in the present invention that at least one reference portion, which is detected if not covered by the part when the image sensor detects an image of the part held by the suction nozzle, is provided at the head unit.
Also, it is preferred in the present invention that the image sensor moves close to the part feeder where a part is picked up.
Also, it is preferred in the present invention that the image sensor moves to a position where a path along which the head unit moves, between a position where a part is picked up from the part feeder and a position where the part is mounted on the printed circuit board, and a path along which the image sensor moves cross.
Also, it is preferred in the present invention that the image sensor is moved by a motor for providing a driving force, a ball screw rotated by the motor, and a bushing and a linear guide member installed at one side of the image sensor and coupled to the ball screw.
Also, it is preferred in the present invention that the image sensor is capable of moving by a linear motor.
Also, it is preferred in the present invention that the head unit is installed to be capable of moving along an X-axis which is installed to be capabl
Cho Tae-yeon
Hwang Young-soo
Shin Jhin-woo
Eley Timothy V.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Samsung Techwin Co. Ltd.
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