sorry to but in on this one, but with the work i have done with several
customers in the past few weeks - opens and shorts - and a few other problems
diriving from dry film processing - is not an open and shut case.

i have found that both in processing dryfilm and LPI - board manufacturers
are not adhereing to actual breakpoint specs - recommended by their resist
and LPI suppliers. exposure step - actual developing solution concentration -
pH inflection points - correlating to the type of dry film and LPI being used
- rinse temperatures - 
pressure - all play a big part in actual developing of the polymer.

either one or the other, or all  of the above were out of sink when a
customer has had problems with dryfilm or LPI. though not as noticeable with
LPI - it makes a difference when your next step after LPI developing is an
electroless finish. 

i have seen panels exiting developers with positive foot on component side
and negative foot on solder side - shorts on one but not the other. for some
strange reason - board manufacturers are more concerned about solution
contact time - either long or short ( usually depending on what they think is
wrong ) rather than the actual overall parameter of how the film is actually
to be processed. customers switching from a 1.5 film to a 2.0 mil film run
into tremendous problems for the first few days. but then, we only look at
the tech data sheet when all else goes wrong.

i would be very interested in knowing how actual parameters for processing
dryfil are implemented by board manufacturers. i sure hope it isn't - coppers
exposed - tape test shows only minor lifting - not much shadows - ok!!! let's
run it.

Rick Fudalewski

Atotech Canada Ltd

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