Conformal coating process control and inspection
Figure 1. A test card from Nordson is shown with and without UV light illumination on spray patterns.
developed for coating defects. touch up of the coating must be recorded to include in PowerPoint training modules
When coated boards are cured in a for future review. Inspection should be or for onsite work instructions is an ideal
convection or IR oven, the temperature based on documented inspection criteria resource for process and quality engineers
profile must be established based on the or customer specification. Where new tasked with training sessions. This type of
material supplier’s recommendations. The defects or PCB design specific issues are reference material is available online.
profile must also be considered in relation seen they should be photographed and
to the coating thickness. Temperature added to inspection criteria or training
profiling procedures should follow the updates or included with customer specific Bob Willis is a process engineer working in the
techniques used for reflow soldering with instructions
electronics industry, providing training, consul-
the correct attachment of thermocouples.
tancy and product failure analysis. He will be
Attempts to speed up the curing cycle are
running a Conformal Coating Workshop at
common causes of failure
SMT/HYBRID/PACKAGING in Nuremberg,
Inspect sample boards under UV
Germany. Bob also offers workshops on conven-
lighting for complete coating coverage.
tional and lead-free on site for customers. He
Check areas of the board after removal of
sets up and optimises production lines for users
any masking for contamination or lifting
and suppliers at exhibitions and also provides
of the coating at the masking interface.
conferences and workshops worldwide. For
The coating should be compared with any
further information on counterfeit avoidance
work instructions, alternatively a golden
coated board assembly should be available
procedures, lead-free training workshops at ITRI
for reference. Obviously in high volume is
in Europe, training materials, lead-free and
where AOI systems will have an impact in
process support visit
www.ASKbobwillis.com.
the future Having images of common process
During sample inspection of boards, defects and examples of satisfactory coating
2009
Do you have a process or technology or a really strong case
call
study that you want to share with Global SMT & Packaging’s
readers? Global SMT & Packaging is currently seeking technical
articles and case studies for publication in its print magazines
for
and website. We are specifically looking for papers that offer a
‘real’ manufacturing solution and that have not been previously
published in another magazine or journal. For editorial
papers
guidelines, contact
editor@globalsmt.net.
www.globalsmt.net Global SMT & Packaging – March 2009 – 5
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