Hi,
For the fine pitch packages, soldermask bridge is hard to realize for the PCB manufacturer, especially for the 0.4mm pitch SOPs/QFPs or less. I don't think soldermask will do an important role in the soldering process for the 0.5mm pitch packages, so with or without soldermask bridge will be all ok.
For the 0.5mm pitch QFP, a 11.8mil pad width is a bit larger, if you can't change the pads for the gullwing tolerance, perhaps a 10mil or 9.7mil stencil window will helps reducing solder bridgings.
LiYi
----- Original Message -----
From: "Kane, Amol (349)" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, October 17, 2009 1:54 AM
Subject: [TN] No Soldermask between Fine pitch QFN and QFP
I am looking at a 19.7 mil pitch QFN device with a center pad and peripheral pads at 9.8x27.5 mils, and a 176 pin fine pitch QFP with 11.8x63 mil pads with HASL finish and without any soldermask in between the peripheral pads!...has anybody seen this type of a board design before? Any stencil design suggestions?
I have a couple of pictures I have requested Steve to post for me regarding the parts ( I am awaiting Steve's reply)
Thanks,
Amol
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