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SIPLACE 80S/F/G User’s Manual 7 Vision Systems Edition 07/97 from S oftware Version SR.010.xx 7. 3 Compo nent Vision System Line engi neer 7 - 21 7.3 Component Vision System The co mponent vi sion system records the prec…
7 Vision Systems SIPLACE 80S/F/G User’s Manual
7.2 PCB Vision System Edition 07/97 from Software Version SR.010.xx
7 - 20 Line engineer
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Number of fiducials
When ceramic substrates and small PCBs are used it is usually adequate to apply two fiducials. It is how-
ever recommended with larger boards to define three fiducials. The individual fiducials may exhibit different
structures. They do however simplify recognition methods when the same structure is used for each fidu-
cial.
–
Correction with two fiducials x position
y position
twisting of the board
–
Correction with three fiducials: Ideally the straight lines drawn through each two fiducial centers
lie parallel to the x and y axes
x position
y position
twisting of the board
shear
warping of the PCB in x direction
warping of the PCB in y direction
NOTE
Under no circumstances should you position 3 fiducials so that they lie on one straight line.
●
Spacing between the fiducials
The fiducials can be distributed over the board at random. It is however a good idea for the spacing
between the fiducials to be as large as possible on both axes. The further apart the fiducials are, the more
precisely the position and angle can be determined optically.
SIPLACE 80S/F/G User’s Manual 7 Vision Systems
Edition 07/97 from Software Version SR.010.xx 7.3 Component Vision System
Line engineer 7 - 21
7.3 Component Vision System
The component vision system records the precise position of a component by determining on the one hand
the offset of the component center relative to the axis of symmetry of the nozzle, and on the other hand the
rotation angle offset to the relative rotational position of the nozzle. The condition analysis of the lead configu-
ration in both x and y direction is also possible.
7.3.1 Component Vision System of the SIPLACE 80S Placement Sys-
tem
7.3.1.1 System Description
The component vision system consists of:
●
the optical system for recognizing the position of components
Each revolver head has its own component position recognition system in star station 8 (see Fig. 7.1.2).
●
the vision evaluation unit
For each gantry two evaluation units are accommodated in the control unit, one for PCB and one for com-
ponent position recognition (see Fig. 7.1.3).
A CCD camera with deflection mirror, imaging lens and LED lighting system constitutes the optical position
recognition system. The usable field of view of the CCD camera (SONY camera XC75) amounts to 14 mm x
18 mm. For position recognition or for the lead tests, the component is evenly illuminated by the LED rows
using the incident-light illumination method, and using the lens sharply imaged on the CCD chip. Using digital
image processing, the correlation principle, and the HALE process (High Accuracy Lead Extraction) it is pos-
sible to determine the parameters for position, angle of rotation and lead condition.
The vision evaluation unit (MVS) has already been described above in Section 7.2.1, as it handles both func-
tions of PCB and component evaluation.
7.3.1.2 Technical Data
Camera type: SONY XC75
Number of pixels: camera 768 (H) x 494 (V)
image 640 (H) x 484 (V)
Field of view: 19 mm x 25 mm
Lighting method: incident-light illumination (red light)
Image processing: correlation principle, HALE - grey-scale procedure
(High Accuracy Lead Extraction)
Evaluation time with lead test: ca. 230 msec (PLCC18)
ca. 140 msec with small components
7 Vision Systems SIPLACE 80S/F/G User’s Manual
7.3 Component Vision System Edition 07/97 from Software Version SR.010.xx
7 - 22 Line engineer
Screen: RGB monitor (VGA mode) 640 x 484 pixels
Component sizes: 1 mm x 0.5 mm ... 18 mm x 14 mm
Range of recognizable components: TSOP, LCC, PLCC, QFP, SO series and so on
basically all components with J and gullwing leads
Minimum lead spacing: 0.5 mm
Number of package forms:
≤
2047
7.3.1.3 Description of Function
One segment of the placement head picks up a component at star station 1. As the revolving star advances,
further components are picked up. Star station 8 accommodates the optical unit of the component vision sys-
tem. On its arrival the component is evenly illuminated with red light by staggered rows of LED's. The lens cre-
ates sharp imaging of components up to a height of 5 mm on the CCD chip of the camera.
The digital imaging of the component created by the component camera is transmitted to the vision evaluation
unit. Using digital image processing (HALE procedure) the evaluation unit compares the component image
with an artificial model previously created with the GF editor (GF= package form). The parameters obtained
from this provide information on positional deviations, rotational angle, lead condition, and component reiden-
tification. The HALE procedure has proved to be highly resistant to interference factors such as interference
reflections, the differing reflection characteristics of lead, incidental light influences, and so on. Once mea-
surement has been successfully completed the segment rotates the component in star station 9 in the correct
placement direction. In star station 1 the component is then placed correctly oriented onto the circuit board.
7.3.2 Component Vision System in the SIPLACE 80 F Placement
Systems
7.3.2.1 System Description
The component vision system consists of
●
the optical system for recognizing the position of components.
The revolver head is equipped with a component position recognition system in star station 8
(see Fig. 7.1.2).
Up to two component vision systems can be used for the IC placement head. These are mounted perma-
nently on the machine base (see Fig. 7.1.5). One (vision system) is used for the optical centering of con-
ventional components with leads. The other - with a FC sensor - optically centers flip chips (see Section
7.6.3.4 Option “Measure component”).
●
the vision evaluation unit
The vision evaluation unit for both PCB and component position recognition is accommodated in the con-
trol unit (see Fig. 7.1.6).