80S-20用户手册 - 第228页
6 Vision functions SIPLA CE 80S-20/F4 User Manual 6.2 PCB vision system Software version S R.407.xx 01/2001 US Edition 228 cials c an var y in str ucture. Y o u can si mplify t he recog nition proced ure if yo u use the …
SIPLACE 80S-20/F4 User Manual 6 Vision functions
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– Thickness (d)
You should ensure, particularly with tin fiducials, that a warpage of more than 1/10 of the struc-
ture width is not exceeded. If this degree of warpage is exceeded, the fiducial may not be
evenly illuminated. This would lead to variations in reflection characteristics and unwanted re-
flections. Recognition of the fiducials will then no longer be assured.
Recommended fiducial dimensions 6
Analysis of the fiducial shapes 6
For tinned and higher dimensional stable structures, (a low degree of etching variation) full circles
or full squares may be regarded as very satisfactory fiducial shapes (the ratio of fiducial thickness
to presoldering thickness will be large!). If dimensional stability falls, the full circle should be pre-
ferred to the square. 6
As far as the fiducial shapes of simple and double cross are concerned, bright copper is advanta-
geous as long as oxidation has not advanced too far. 6
– Surface of the fiducials
Make sure that the surface of the fiducial is as level as possible and with little oxidation. Avoid
wetting the fiducial with solder-stop lacquer as this could result in lowering the contrast with the
background or produce unwanted reflections. Similar effects occur with tinned fiducials as well.
– Contrast of the fiducials
To ensure that fiducial recognition is of a high quality, select a high brightness contrast between
the fiducial and the base material; in other words, bright fiducials on a dark base material and
vice versa. For example, on a copper or tin background apply dark fiducials. In the case of ce-
ramic substrates with a bright surface and unsatisfactory reflective properties, it is often helpful
to precoat with a dark resistance material in order to improve contrast characteristics.
– Number of fiducials
When using ceramic substrates and small boards, tow fiducials will usually be sufficient. How-
ever, with larger boards it is recommended that three fiducials be defined. The individual fidu-
Fiducial type
Simple cross Double cross
Range Ideal Range Ideal
Length (l) 0.9 mm (min) 2.0 mm 1.8 mm (min) 2.75 mm
Width (b) 0.9 mm (min) 2.0 mm 1.8 mm (min) 2.75 mm
Line thickness (s) 0.3 - 1.4 mm 0.5 mm 0.3 - 0.75 mm 0.5 mm
Line spacing (a) ——0.5 mm (min) 0.75 mm
Thickness (d) < 1/10 of the structure width < 1/10 of the structure width
Tab. 6.2 - 1
6 Vision functions SIPLACE 80S-20/F4 User Manual
6.2 PCB vision system Software version SR.407.xx 01/2001 US Edition
228
cials can vary in structure. You can simplify the recognition procedure if you use the same
structure for each fiducial.
– Correction with two fiducials X-position
Y-position
PCB skew
– Correction with three fiducials: ideally, the straight lines which each pass through the cen-
ters of two fiducial will be parallel with the x and y axes
X-position
Y-position
PCB skew
Shear
Warpage of PCB in the X direction
Warpage of PCB in the Y direction
NOTE 6
You should never position 3 fiducials so that they are located on a straight line. 6
– Spacing between the fiducials
You may locate the fiducials at any point on the board. However, it is a good idea to space the
fiducials as far apart as possible on the two axes. The further apart the fiducials are from one
another, the more accurate optical position and angle recognition will be.
SIPLACE 80S-20/F4 User Manual 6 Vision functions
Software version SR.407.xx 01/2001 US Edition 6.3 Component vision systems
229
6.3 Component vision systems
The PCB vision system records the precise position of a component by determining the offset be-
tween the component center and the nozzle’s axis of symmetry, and by calculating the rotational
offset from the relative rotational position of the nozzle. It is also possible to analyze the state of
the lead configuration in the X and Y directions. The component vision system consists of the op-
tical system for recognizing the component position, and the vision analysis unit. 6
6.3.1 Component vision system on the 12-segment Collect&Place head
6.3.1.1 System description
The 12-segment Collect&Place head has its own component position recognition system in star
station 7 (see Fig. 6.1 - 3
, page 214). The vision analysis unit for PCB and component position
recognition is located in the control unit (see Fig. 6.1 - 6
, page 219). 6
The optical component position recognition system consists of a CCD camera with deflector, im-
age lens, and LED illumination system. The usable field of view of the CCD camera (SONY XC75
camera) measures 24 mm x 24 mm. For position recognition, and for the lead test, the component
is evenly illuminated by the rows of LEDs using the front lighting method, and is projected onto the
CCD chip in sharp focus by the lens. The position, rotational angle, and lead condition parameters
are determined using the h
igh-accuracy lead extraction (HALE) method of digital image process-
ing. 6
The vision analysis unit (MVS) was described in section 6.1.4
, page 218, since it performs both
PCB and component evaluation functions. 6
6.3.1.2 Technical data
Camera type: SONY XC75
Number of pixels: 484 x 484
Field of view: 24mm x 24mm
Illumination method: Front lighting (infrared light), 3 LED levels
Image processing: HALE gray scale method
(H
igh Accuracy Lead Extraction)
Screen: RGB monitor (VGA mode), 640 x 484 pixels
Component sizes: 0.5mm x 0.5mm ... 18.7mm x 18.7mm
Range of recognizable components: TSOP, LCC, PLCC, QFP, SO series up to SO28
essentially all components with J and
gull wing leads,
µ
BGAs
Minimum lead pitch: 0.3mm for the camera
0.5mm for the machine
Minimum ball diameter for
µ BGAs
:250µm