6.2 Automatic placement inspection
Inspection of the PWB after component placement is the next possibility. With this method
possible placement failures can be detected and some defective paste printing phenomena as
well. If there is a sign or mark on the component, it can be read and identified with the help
of modern image processing algorithms even if it has more than one different-looking label
type. APIs (Table III) are able to measure most parameters of components objectively e.g. X-Y
shift, rotation, polarity, labels, size etc. [83]-[90]. Four manufacturers have this special appli‐
ance in stock. [91]-[94].
Manufacturer BeamWorks Landrex Omron Viscom
Model
Inspector cpv Optima II 7301 Express VT-RNS-Z S3054QV
12 x 9 mm @ 15 µm; 48 x 36
mm @ 73 µm
10 x 10 mm; 15 x 15 mm n.a. 1280 x 1024 pixel
Pixel size [µm]
15; 73 n.a. 10; 15; 20 10; 22
Depth of field (max. component
height for inspection) [mm]
Number of cameras
1 1 vertical, 4 angled 1 1
Lighting method
oblique ring, white LED light n.a. ring-shaped RGB LED n.a.
Board size max. @ single board
operation [mm x mm]
508 x 406 609 x 558 510 x 460 443 x 406
Board size max. @ dual board
operation [mm x mm]
Board size min. [mm]
40 x 28 51 x 76 50 x 50 n.a.
Board thickness [mm]
0.8 - 3.2 n.a. n.a. n.a.
Conveyor height [mm]
n.a. n.a. n.a. 850 - 960
Board edge clearance [mm]
4 n.a. n.a. 3
Board edge clearance top [mm]
25; 37 63 20 35
Board edge clearance bottom
[mm]
Inspection speed [sq. cm/sec]
2 @ 12 x 9 mm field of view n.a.
250 ms/screen @ 10 sq. mm
field of view
missing component, wrong
component, polarity check,
offset, skew
missing components, misoriented
components, extra components,
component placement, tombstoned and
bill boarded components, lifted leads,
insufficient solder and excess solder,
wrong part, through hole pins
presence of solder, component
shifting, polarity error, missing
components, wrong
components, solder balls,
skewing, bridging, foreign
objects
Table 4. Comparison of Automatic Placement Inspection (API) machines
6.3 Post soldering inspection
Most manufacturers agree from a strategic point of view, that optical inspection after soldering
has been completed should not be missed out. At the very least, the defective products must
be eliminated because many failures are generated during soldering: “Forty-nine percent of
the true faults were detectable only after soldering. These consisted of component and
soldering faults. Forty-eight percent of the optically recognizable faults could not be recog‐
nized electrically.” [54].
Automatic Optical Inspection of Soldering
http://dx.doi.org/10.5772/51699
395
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