Data processing: measuring – calibrating – or testing – Calibration or correction system – Position measurement
Reexamination Certificate
1998-04-08
2001-03-13
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Position measurement
C700S254000, C702S152000
Reexamination Certificate
active
06202031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the automatic placement of components onto circuit boards. More particularly, the invention relates to a method and apparatus for calibrating an automated placement machine which retrieves parts from a parts tray and places them onto desired locations of an assembly such as a printed circuit board (PCB).
2. Description of the Related Art
In the electronics industry, high speed automated placement machines are often used to place electronic parts or components onto bare PCBs. These automated placement machines typically include a robotic arm which has a vacuum nozzle for lifting an electronic component, carrying the component to a designated location, and placing the component onto a PCB at a designated location on the PCB. With the use of some automated placement machines, after the part is picked up by the robotic arm, the part is placed onto a part shuttle which transports the part within the vicinity of a second robotic arm of the automated placement machine. The second robotic arm also includes a vacuum nozzle that picks up the part from the parts shuttle and places the part at a designated location on the PCB. In order to expedite this process, components are typically extracted directly out of the packaging medium in which they are shipped by a manufacturer, or distributor, of the components.
One commonly used packaging medium is known as a parts tray. Typically, parts trays contain a number of cavities, each capable of containing a component therein. The physical dimensions of each cavity within a particular parts tray are typically the same for each cavity and the cavities are usually arranged in a uniform matrix pattern. Therefore, by knowing the dimensions of each cavity and also taking into account the particular matrix configuration of the cavities for a particular parts tray, it is possible to calculate the relative spatial coordinates (i.e., positions) of each of the components contained within these cavities with respect to a common point of reference. After the coordinate positions of each of the components have been determined, the robotic arm may be programmed to successively move to each coordinate position corresponding to the location of the components in order to retrieve each of the components from it's respective cavity.
In one prior art method, multiple parts trays may be accessed by an automated placement machine by providing a multi-tray unit, as it is commonly known in the industry. The multi-tray unit includes multiple drawers, each capable of holding one or more parts trays therein. The multiple drawers are typically stacked one on top of another. When a robotic arm is programmed to access a parts tray in one of the drawers, the multi-tray unit will move select drawers in the stack so as to create a space above the designated drawer containing the desired parts tray. The robotic arm can then move in this space above the designated drawer in order to retrieve components from the designated parts tray.
Referring to
FIG. 1
, a typical multi-tray unit
100
is illustrated. The multi-tray unit
100
includes a base
101
and a tray tower
103
attached to and extending upwardly from the base
101
.
Multiple drawers
105
are coupled to the tray tower
103
. Each drawer
105
is typically movably attached to the tray tower
103
by means of a lead screw assembly
107
, driven by a lead screw assembly motor
108
, which can move a select group of the drawers
105
. Each drawer
105
includes a cavity
106
for receiving and holding a parts tray (not shown) therein. The multi-tray unit
100
of
FIG. 1
, as well as various other types of multi-tray units, which perform similar functions to those described above, are well-known in the art. In one embodiment, the multi-tray unit
100
is a Fuji Multi-tray unit manufactured by Fuji, Inc. which is available with the Fuji-IP2 or IP3 automated placement machines.
When an automated placement machine (not shown) is programmed to retrieve a particular component from a designated parts tray, a robotic arm
109
of the automated placement machine will move to a particular spatial coordinate which has been programmed into a database of the automated placement machine. As shown in
FIG. 1
, the robotic arm
109
has a vacuum nozzle
111
attached thereto for picking up components from a parts tray. A designated parts tray is made accessible to the vacuum nozzle
111
of the robotic arm
109
by the tray tower
103
which moves selected drawers
105
such that a space is provided above a designated drawer
105
a
containing the designated parts tray. The robotic arm
109
can then move in this space above the designated drawer
105
a
in order to pick up selected components with its vacuum nozzle
111
.
One method of providing a space above the designated drawer
105
a
is to move all the drawers
105
above the designated drawer
105
a
upwardly and away from the designated drawer
105
a.
Another method of making the designated drawer
105
a
accessible is to move the designated drawer
105
a
and all the drawers
105
beneath it, downwardly and away from the drawers
105
above the designed drawer
105
a.
In order to move the trays in this fashion, the lead screw assembly motor
108
rotates either clockwise or counter-clockwise, depending on which way the trays are to be moved, and drives the lead screw assembly
107
housed within the tray tower
103
. The lead screw assembly
107
includes a threaded shaft (not shown) which has relatively large threads in the center portion of the shaft when compared to the threads at the upper and lower portions of the shaft. The larger, more coarse, threads at the center portion of the shaft causes the trays to move more quickly through the center portion of the shaft while the smaller, finer, threads at the upper and lower portions of the shaft cause the trays to move much slower so that they do not crash into the upper or lower ends of the tower assembly
103
. By moving the robotic arm
109
near the area of the center portion of the shaft, the robotic arm
109
may be positioned in the space between two trays so as to be underneath one tray and above another. In this position, the robotic arm
109
can retrieve components from the parts tray immediately below the robotic arm
109
.
FIG. 2
is a side elevational view of the multi-tray unit
100
of FIG.
1
. As shown in
FIG. 2
, the robotic arm
109
is positioned above the designated drawer
105
a
such that the vacuum nozzle
111
may pick up a component (not shown) contained within a parts tray (not shown) which is in turn contained within the designated drawer
105
a.
FIG. 3
is a perspective view of a typical parts tray
200
having multiple cavities, or pockets
201
, arranged in a 3×4 matrix. Within each cavity
201
is a component
203
. The parts tray
200
is a common packaging medium in which components, particularly integrated circuits (ICs), are shipped. In order to secure each of the components
203
in their respective cavities
201
, the top of the parts tray
200
is typically covered with an electrostatically safe film or cover sheet (not shown). When the components
203
are ready to be assembled onto a PCB, the cover sheet on the parts tray
200
is removed and the parts tray
200
is typically inserted into a drawer
105
of a multi-tray unit
100
(FIGS.
1
and
2
). As discussed above, with reference to
FIG. 1
, the components
203
may then by extracted from the parts tray
200
by a robotic arm
109
(
FIG. 1
) of an automated placement machine.
FIG. 4
is a top plan view of the parts tray
200
of
FIG. 3
contained within a drawer
105
having a cavity
106
for holding the parts tray
200
therein. The parts tray
200
includes twelve cavities
201
arranged in a 3×4 matrix, each cavity
201
containing a component
203
therein. As shown in
FIG. 4
, a reference point
300
is selected at a point where an inside corner of the cavity
106
is located, for example. With respect to the reference po
Campbell Scott
Huelsenbeck Robert
Assouad Patrick
Knobbe Martens Olsen & Bear
MCMS Inc.
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