First, this will ease manufacturing process during PCB fabrication, as
the mask will break easily between the pads if the mask width is small.
Second, as your EMS requested the modification, this showed that they
are confident in meeting you targeted yield, so no problem.
Third, as mentioned by you, better side fillets solder joints, why not.


 -----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Lothar Thole
Sent: Monday, May 21, 2007 3:47 PM
To: [log in to unmask]
Subject: [LF] No soldermask between SQFP leads ok?

Thanks again to the responses to my question on asymmetric microBGA
joints. 

Another question on land patterns if I may:

Our new leadfree assembler has requested us to modify our current SQFP
Land Patterns by making the pads wider to allow for Side Fillets, thus
improving the reliability of the solder joint. This will result in a
situation where the 0.4mm (0.016in) pitch devices have a Pad-Pad spacing
of 0.125mm (0.005in) with no dividing Soldermask. Our concern now is the
possibility of Solder Bridging. Will the benefits of the side fillets
outweigh the risks of bridging? Thanks in advance.

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