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August 2001

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Subject:
From:
Safavi-Bayat Shahed <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 31 Aug 2001 07:34:46 -0400
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text/plain (103 lines)
Justin
Putting vias between the pads!! That's something I never do with 0603 or
most of other
SMT parts. As a matter of fact I make sure that when the parts or shape
created it has via keep out between
the pads.


Shahed Safavi-Bayat, C.I.D.
Cad Designer

1035 Greenwood Blv. Suite 173
Lake Mary Fl 32746
mailto: [log in to unmask]
Tel : (407)829-4440 ext.216
Fax : (407)829-2213



-----Original Message-----
From: Braime, Justin [mailto:[log in to unmask]]
Sent: Friday, August 31, 2001 5:14 AM
To: [log in to unmask]
Subject: [TN] 0603 land pattern debate


Hi all,
I have had some problems with a recent build with 0603 capacitors. The
problem was that they were either very skewed or were soldered to one pad
only (pulled off the other). The land pattern for the 0603 cap on this board
was (I thought) fairly questionable. Using the IPC-SM-782 terminology, the
current design is:
X = 1.27 (0.05")
Y = 0.508 (0.02")
G = 1.016 (0.04")
Our design dept's justification for this design is based on being able to
put a via between the pads, but to my mind the G value is too borderline for
consistent results. Also, I think the X value is a little on the high side -
hence the skewing.
I'm now trying to convince the design guys to adopt the IPC guidelines - at
least the recommended G value anyway.
I'd appreciate anybody else's thoughts on this!
Incidentally, we placed 0402s on the same board with very few problems :)

Thanks


Justin Braime

Senior Production Engineer
Thales Instruments Ltd.
480 Bath Road
Slough
SL1 6BE

Tel:    01628 604455 x 392
Fax:    01628 662017
Email:  [log in to unmask]



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