Chris and all,
Thanks for the help.
Kinda thought it was OK, and like said there
can be open vias under a PQFP and there would
be no paste applied to the TQFP if the PQFP
were the one installed.
Thanks
Bob Wolfe
----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 06, 2002 12:17 PM
Subject: Re: [DC] Land Pattern within Land Pattern (TQFP)


> 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)
>                       Sent by:
>                       DesignerCouncil
>                       <DesignerCouncil
>                       @IPC.ORG>
>
>
>                         08/06/02 10:40
>                                     AM
>                         Please respond
>                         to "(Designers
>                       Council Forum)";
>                         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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