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Pr oduc t Ch ang e Ov er User Re f eren ce Manu al 4022 591 960 82 6-84 FCM M ult ifle x 02.02 FI GURE 6-34 Sk ew angl e d etecti on 7. Ch eck the distance betw een th e middl e o f th e firs t side (North) t o the mid d…
4022 591 96082 User Reference Manual
02.02 FCM Multiflex 6-83
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The QFP algorithm
▼ How does it work
1. Find the first lead with a defined search area and last lead with a fine search
area of the South side.
2. Find the first lead and the last lead for the other sides (North, East, and West).
3. Depending on the component lead pitch, measure all the lead sides (edges) or
lead ends. If the pitch < 0.50 mm, then search for lead ends, otherwise search for
lead edges.
FIGURE 6-33 Measuring lead ends or lead edges, depending on the actual lead pitch
4. Check the pitch between the leads (if there is more than one lead a side).
5. Calculate the centre and angle of the component origin with the information of
the lead sides or lead ends (depending on the lead pitch, see Step3.) for all four
sides.
6. If the skew angle is required, measure the skew angle of the 4-sided component.
Fine lead search (looking for
lead ends)
Fine-rule
r
Ruler-offset
X = Lead end
Lead pitch < 0.50mm
Regular lead search (looking
for edges)
Ruler
Ruler-offset
X =
Edge
Lead pitch >= 0.50mm
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User Reference Manual 4022 591 96082
6-84 FCM Multiflex 02.02
FIGURE 6-34 Skew angle detection
7. Check the distance between the middle of the first side (North) to the middle of
the second side (South) and between the third side (East) and the fourth side
(West).
8. Calculate the component origin, based on the found vision origin and gravity
offsets.
FIGURE 6-35 The QFP algorithm measuring aspects
Skew-angle detection:
This an optional parameter
and can only be used for
the QFP, PLCC and SPECIAL
algorithm and for components
with at least 3 sides with leads.
The purpose is to detect an
inconsistency in orientations
determined from 2 pairs of
lead sides; caused by global
skewness of one or more lead sides.
Global skewed lead side
NORTH
SOUTH
EAST
WEST
Ruler
Ruler
Ruler offset
Ruler offset
Search area
Fine-search area
Fine-Search area
Fine-search area
NORTH
SOUTH
EASTWEST
4022 591 96082 User Reference Manual
02.02 FCM Multiflex 6-85
Product Change Over
FIGURE 6-36 Calculation of the component’s origin
▼
For which components do you use this algorithm
For components that have leads on all four sides, and that have the leads projecting
outside the body (perpheral leads), and that have only one lead group a side, like:
• QFP components;
• FQFP components.
▼
General important information
• Ruler offsets are adjustable in the SMD info file; normally the value 3 is used
for most components (5 or 7 is also possible if you have components with a
bigger lead width). Ruler offset is in pixels; one pixel = 75x 75 µm. Always
use odd ruler widths in order to get valid mean calculation results.
• The body length and width in the SMD info file must be correct, because they
determine the positions of the leads together with the number of leads and
the lead pitch.
• For the ruler threshold, the value is normally between 20 and 30, but it
depends on the specific component type and the amount of light used.
• The search area as indicated in the drawings matches the reject level in the
SMD info file.
Component origin = vision origin
Component outline
NORTH
SOUTH
EAST
WEST
Body length
Body width