Try using the online land pattern calculator at http://www.ipc.org/html/fsresources.htm . But from your data, it seems the land width is sufficient for your needs.

You should also make sure that the land is of the proper length so that you have a sufficient heel fillet.  There was some discussion last year or so on TencNet about the most critical portion of an SMD solder joint for IC packages, and the consensus was (according to my un-trustworthy memory) the heel fillet was the most important.

HIH.

Roger M. Stoops, CID 
Trimble Navigation Ltd., Dayton, OH, USA
Ph: 937.233.8921  or  937.233.4574  ext 288 
Fax: 937.233.7511 



-----Original Message-----
From: Eric Christison [mailto:[log in to unmask]]
Sent: Monday, February 24, 2003 11:56 AM
To: [log in to unmask]
Subject: [TN] Pad Pitch to width ratios


Perhaps someone can give me an opinion on this one.

I've been asked to approve the design of a surface mount device which has QFP
type legs, 0.75mm wide on a 1.4mm pitch.

The vendor is recommending a PCB pad layout for the device where the pads are
1.05 wide on (obviously) a 1.40mm pitch. The part would be used in high volume
consumer electronics.

Would anyone out there anticipate any soldering problems with this geometry? I
had a look through IPC-SM-782 but didn't find it much help.

Thanks,

--
Eric Christison
Mechanical Engineer
STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF

tel:    +44 (0)131 336 6165
fax:    +44 (0)131 336 6001

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