Ian,
as for your comments below, I will vouch for your comments 100%.
Typically almost 2/3rds of the solder in on a gull wing device is
reflowed to the heel area. Thus where is the strongest portion of the joint?
Typically the toe supplies a place to probe or apply heat from your hand
soldering iron during re-work/touch-up.
SMT Plus' land pattern designs are designed for a standard paste
application of 6 - 8 mils where the paste mask aperture matches the pad
aperture. They are also significantly smaller then the former IPC land
patterns.
Sincerely,
Brad Velander.
Lead PCB Designer
Norsat International Inc.
Microwave Products
Tel (604) 292-9089 (direct line)
Fax (604) 292-9010
email: [EMAIL PROTECTED]
http://www.norsat.com
-----Original Message-----
From: Ian Wilson [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 12, 2002 4:38 PM
To: Protel EDA Forum
Subject: Re: [PEDA] IPC Footprint Standards
<SNIP>
I have read somewhere (maybe "Printed Circuits Handbook" (Clyde, 4th
Edition), possibly in some notes from elsewhere, that the heel rather than
the toe is the most critical part of the join (from a strength
perspective). Reflow footprints can theoretically have no toe and still be
reliable at least according to the data I read some year ago. The obvious
problem with this is the difficulty of inspection for QA - but these days
we have that with BGA footprints don't we. I would not suggest that anyone
reduces their small device pads this far on my recommendation - I have
never gone that far.
<SNIP>
I gather the SMC-plus (is that right?) footprint libraries may have
soldering technology specific footprints - at least someone once told me
they did.
Ian Wilson
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