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What you need to know before buying your AOI solution
is important when running in any
manufacturing environment. As your
staff and personnel change, does the AOI
vendor have the resources to support you?
Does the company have direct applications
and hardware support engineers on a
worldwide basis? Are those engineers
located a reasonable distance from your
facility and fully trained? These are
important traits that vary greatly across
many AOI manufacturers, and can affect
your ability to be successful in the longer
term.
When it comes to equipment reliability,
MTBF is key. Look at the system’s
components, the manufacturing practices
used to build the system and the materials
used. Does the system use a start-stop
motion technique or does it use a linear
motion system? A linear motion system will
provide greater reliability over time.
5. resolution and throughput
Another common mistake made in an
AOI evaluation is the focus on camera size.
It is normally presumed that the larger
the number of megapixels, the better the
performance. This is not always true. Other
aspects that need to be evaluated include
camera sensitivity (how fast you can take
an image), resolution at the given field of
view (FOV), which motion system is used
(on a start stop system, extra time is needed
for the stage to stabilize before an image is
captured), and the overall throughput at a
given resolution.
For example, a system using a 1.4
megapixel high-sensitivity camera providing
a resolution of 12 µm could have a
throughput of 7 in
2
/s where a system with
a low-sensitivity 3 megapixel camera only
provides a resolution of 25 µm at 7 in
2
/s.
Design traits that will slow throughput
include vibration from a high-speed move
and stop, low sensitivity cameras, stage
speed and overall FOV.
There are many factors that can affect
throughput, but a defined resolution is
required to detect defects. As a guide, Table
3 defines the typical resolutions required
will allow you to make a more informed reliability, programming and on-going
for inspection of common component sizes.
ERSA_Ad_GLOBAL_SMT_PACKAGING_issue_8.indd 1
AOI decision. program support times all need to
Understanding resolution vs. throughput
16.09.2009 15:53:02
be
judged equally against the overall purchase
conclusion cost of a system.
Table 3. Typical resolution requirements.
Don’t make the common mistake and Defect coverage should always be
Inspection Requirements Resolution
focus your evaluation on a single aspect of the first reason for using any inspection
an AOI system. Megapixels alone are not platform. If you understand your
0402 and above 16 µm
important, programming times in a dem- manufacturing process and focus on the
0201 12 µm
onstration can be deceiving, and don’t lose defects generated in your process, your AOI
focus on your real need for AOI. system will always provide you with the
01005 8 µm
Defect coverage, manufacturing strategy maximum value and ROI while increasing
Microelectronics 3 µm flexibility, the use of measurement data, your overall quality.
throughput, company stability, system
Wire-bond 1 µm
www.globalsmt.net Global SMT & Packaging – October 2009 – 13
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