When we made the switch to LPI, Dry film was too thick for the
surface mount components to reach the pads.  Although I'm
sure that is not the case any more, I'll stick with what is already
working.  One advantage of LPI over dry film is rework.
Occasionally we will need to cut and jump circuitry.  You just
can't cut through dry film mask, it's too tough.  That's a good
thing, but it's a trade off.  By the way, we do specify our vias to be
filled with LPI before the regular solder mask is applied.

Larry Campbell
Supervisor, PWB
BFGoodrich, Avionics Systems

>>> <[log in to unmask]> 11/11/97 05:41pm >>>
Among the ways of sealing vias on LPI solder masked boards
are a)  filling
the vias with LPI, and b) tenting the vias with dry film solder
mask.

We are on the brink of converting from dry film to LPI on all our
PCB's.  I
would appreciate any comments on the relative merits/demerits
of boards
produced by these two processes.  Our supplier recommends
the dry film
option.

Our boards are sometimes in relatively harsh environments and
are designed
to operate from -40 C to +70 C.


Thanks to those of you who responded to my inquiry on how to
repair
urethane conformally coated boards which have been
contaminated with
silicone prior to conformal coating.

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