Hi Bob-
As long as you're not applying solderpaste to the lands I don't see it
being much different than vias w/open mask. Have done a bunch of boards
with open vias under QFP where the bottom side is wave soldered... no
problems even 10 years later in automotive enviornment.
-Chris




                      "Robert M.
                      Wolfe"                   To:      [log in to unmask]
                      <[log in to unmask]         cc:
                      ET>                      Subject: [DC] Land Pattern within Land Pattern (TQFP)
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                        08/06/02 10:40
                                    AM
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                        Please respond
                         to "Robert M.
                                Wolfe"






Hello All,
I have a situation where there is a need to provide a dual
footprint pattern for an alternate package. They are a
PQFP and a TQFP. The smaller pattern with easily
fit within the larger and I believe I can make all connections
with both on board.

Question is whether or not there will be any assembly
issues with lands under a QFP which of course will
not have solder mask over them but solder, I would
expect a stencil to be made for both versions or
at least mask off part no tbeing installed. But during
reflow would the solder already on the lands cause
a problem under there, ie shorts. Or would using an
OSP coating solve the problem, but I guess that coating
once gone would leave exposed copper under that part.
Any suggestions would be appreciated
TIA
Bob Wolfe
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