IPC9850_Surface Mount Equipment Characterization.pdf - 第45页
IPC-9850 Official Proposal May 2001 45 the component are calculated with the different methods above. The mean and standard deviation of the center location using the different methods is given in the tables below. Using…
IPC-9850
Official Proposal
May 2001
44
The different methods to measure the angle of the component are described below.
D-2.2.1 Using 2 diagonal fiducials
Take the angle of the line through the 2 diagonal fiducials and subtract the nominal angle (in this case the
component is square so the nominal angle is 45 degrees).
D-2.2.2 Using 4 fiducials
Method 1
Take the average of the angle of the two diagonal lines through the fiducials
Method 2
Take the angle of the line through the vertical midpoints minus 90 degrees:
Method 3
Take the angle of the line through the horizontal midpoints:
Method 4
Take the average angle of all “sides” of the component:
Method 5: Take the average of the angles of method 2 and 3
D-2.3 Simulation
By simulating measurement errors on the X- and Y-locations of the fiducials, the sensitivity of the methods above is
determined.
The measurement errors on the fiducials are assumed to be distributed with a standard deviation of 0.0005 mm.
Then 1000 measurements are simulated (using MS Excel). With those measurements, the x, y, and theta locations of
IPC-9850
Official Proposal
May 2001
45
the component are calculated with the different methods above. The mean and standard deviation of the center
location using the different methods is given in the tables below.
Using 2 fiducials
Table D-1 Mean and stdev using 2 fiducials (nominal means are: x=0, y=0, theta=0)
x
(mm)
y
(mm)
theta
(mm)
Mean 0.000 0.000 0.000
Stdev 62.10
-5
61.10
-5
243.10
-5
Using 4 fiducials
Table D-2 Mean and stdev per method using 4 fiducials (nominal means are: x=0, y=0, theta=0)
Method 1 Method 2 Method 1 Method 2 Method 3 Method 4 Method 5
x
(mm)
y
(mm)
x
(mm)
y
(mm)
theta
(mm)
theta
(mm)
theta
(mm)
theta
(mm)
theta
(mm)
Mean 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Stdev 42.10
-5
44.10
-5
62.10
-5
60.10
-5
174.10
-5
228.10
-5
230.10
-5
167.10
-5
166.10
-5
D-2.4 Conclusion
From the results above can be concluded that using 4 fiducials to estimate the center location of the component is
more reliable. From table 2 is concluded that the best methods to calculate x,y and theta are method 1 for x,y and
method 5 for theta.
So the glass QFP and BGA are recommended to be measured as follows:
Measure the X- and Y-location of the 4 (black) fiducials. Construct with these results 4 (white) midpoints at each
side of the component. The theta of the component is constructed by taking the average angle of the 2 lines. Taking
the average x and y of the measured fiducials determine the X- and Y-location of the component. Beware that this is
NOT the same as taking the intersection point of the 2 lines through the midpoints.
2
A
3
4 C
D B
1
IPC-9850
Official Proposal
May 2001
46
In formulas:
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2
tantan
2
90
4
4
4321
4321
4132
4132
11
21
4321
4321
yyyy
xxxx
xxxx
yyyy
lineline
component
component
component
thetatheta
theta
yyyy
y
xxxx
x
−−+
−−+
−
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+
=
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+++
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D-3 1608C component
The methods to measure the 1608C component are almost the same as is described for the slugs.
First all four sides of the component are measured (black lines). With these lines, the intersection points are
constructed (black points). Now the same methods as described for the 4 fiducials of the slugs can be applied.
Therefore also for the 1608C component it is recommended to use method 1 and 5 for the component- x, y and theta
respectively.
D-4 SOIC16 component
Method 1
The leads of the SOIC-16 component are measured as follows. The right, left and bottom sides of the lead are
measured. Two intersection points are constructed from these measurements. The average x and y of intersection
points are the coordinates of the lead.
This can be done for all leads, but also for only a few leads. In the section below, measurements are simulated to
determine the influence of the number of measured leads on the center-estimate of the component. Notice that
always the most outer leads are measured to get a correct and reliable calculation of the x,y and angle (e.g. Using 8
leads, at both sides the two outer leads are measured).
The position of the center of the component is the average x and y of all measured leads.
The theta of the component is
1, Average the location for both X
T
and Y
T
on the top side leads of the component
2, Average the location for both X
B
and Y
B
on the bottom side leads of the component
3. Use the points (X
T
,Y
T
) and (X
B
,Y
B
) to determine a line
4, Then measure the angle of this line minus 90 degrees to determine the angle of the component.
3
7 11 15
16
12 8
4
1
5
9
13 14 10
6 2
B
T