You know you're in trouble, when there's no relief in sight.
Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thomas, Ian (Ian) %
Sent: Wednesday, September 12, 2007 3:39 AM
To: [log in to unmask]
Subject: [TN] Thermal issue's with unleaded solder paste.

Hi, Need some useful advice regarding a current design.
I have a 12 layer FR4-370HR PCB, using stacked uvia's in pad which
connect to planes on layers 2 & 3 which are flooded with no thermal
relief.

We have seen no issue's with leaded assembly, but on transferring over
to un-lead, we are seeing solder issue's with the BGA's (0.5mm pitch) on
assembly
and also rework issuse's with 90% of the other components (including
0402's) in getting them off the board.

Our first thoughts are to thermally relieve all the micro via's, but
there are issue's because this may leave you with only one spoke on a
pin in some areas.

Has any seen these issue's before?

Thank's in advance.

Ian
LSI Technology (Mobility)


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