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What you need to know before buying your AOI solution
fell by over 50%.
Table 1. Structural DPMO rates. Table 2. Defect-based DPMO rates.
Ensuring low false
Package Technology Pitch Structural Defect Type DPMOJ Rate
call rates can be a key
Type inches/mm DPMOJ
aspect of a successful
Short 60
AOI implementation,
Leaded (gullwing) > 0.05/1.27 200
Complete Solder Open 26 increasing overall quality
Leaded (gullwing) 0.05/1.27 500
Marginal/Insufficient/Other Solder 46
while reducing costs.
Leaded (gullwing) 0.025/0.64 700
Cosmetic/Visual 81
Defect coverage—how
Leaded (gullwing) 0.02/0.5 1000
Missing 193
do you get an accurate
Leaded (gullwing) 0.016/0.4 10000
inspection coverage
Wrong 18
report?
Leaded (gullwing) < 0.016/0.4 15000
Bad/Other Electrical 44
Whereas many electrical
Jlead 300
test platforms such as
capabilities for microelectronics
ICT and flying probers
Eutectic BGA 0.05/1.27 100
and semiconductor inspection.
provide accurate reports on defect cover-
Eutectic BGA < 0.05/1.27 150
If you are looking at maximizing
age, most AOI platforms do not have the
NonEutectic BGA 0.05/1.27 150
the ROI (return on investment)
ability to provide this required feature.
of your AOI purchase, process
When you have an inspection routine in
CSP 100
position flexibility and inspection
place, how do you know it is actually find-
Column Grid 100 capabilities of the system are key
ing defects? A few experienced vendors can
to the success of your investment.
provide this information, with the most
1206 SMT 400
As an example, an experienced
capable AOI vendors providing validated
0805 SMT 150
AOI supplier can provide
defect coverage for all defects detected by
extensive capabilities, as shown
the AOI system.
0402 SMT 150
in Figure 2, that allow for many
This is an important point that should
0201 SMT 200
different inspection scenarios
not be ignored. There may be items on
01005 SMT 300
beyond basic SMT inspection.
your product that may not be inspectable.
Knowing this will allow you to better plan
1206 Wave 400
False call rates and how these
your overall test and inspection strategy.
0805 Wave 150 affect defect coverage
For fault coverage, one of the
2. improving your process and pro-
0402 Wave 150
key items that affects the overall
viding process feedback
SMT Connector 2000
efficiency of defect detection
Beyond catching defects, what other
is the false fail rate of a system.
aspects of an inspection system are impor-
Res/Cap Pack 100
Simply put, the more false fails
tant to manufacturing processes? Do you
PTH/Wave 4 2000
you pass on to a repair opera-
monitor how is your process changing?
tor for validation, the more real
Can you predicatively highlight issues that
easily visible by inspecting the changing
defects get missed. A major study
will cause defects? If you are focused on
reflow profile. As you see in the example,
by Solectron presented at IPC showed that
improving your manufacturing processes,
the failing joint shows up red from the red
when false fails increased excessively, i.e.
you will need variable data (measurements)
45 degree lighting versus the high green
above 3000 ppmJ, an inexperienced opera-
versus attribute data (pass/fail). If you are
lighting, which shows good joints.
tor could make <5% correct calls, while an
only looking at end-of-line defect data, the
experienced operators correct call rate still
attribute data produced by template/com
Detection Toolbox, what tools/algorithms
are available to detect defects
As technology changes are a constant in
our industry, it is important to understand
the flexibility of the inspection tools and
future capabilities of the AOI system. Is the
system always going to be post-reflow? Will
you ever look to put the system in a new
position in the line? What technologies are
you building today, and what is your future
roadmap for manufacturing?
Some AOI systems are purely focused
at a single task, i.e. paste, pre-reflow, post-
reflow or post-wave. More experienced
AOI suppliers will provide solutions that
cover all aspects of the manufacturing
line in the same system, providing
integrated 2D/3D technologies as well as
Figure 2. Inspection techniques.
www.globalsmt.net Global SMT & Packaging – October 2009 – 11
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