Hmmm, good question. First thought is that it provides for a good toe/heel fillet which I guess depending on the lead style is where a good portion of the solder joint strength comes from. Maybe something to do with the surface tension of Pb-free solders? Other than that...? Anyone from the (1-13)
Surface Mount Land Patterns Subcommittee listening?
Roger
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brooks,Bill
Sent: Tuesday, November 16, 2004 1:39 PM
To: [log in to unmask]
Subject: Re: [TN] SOD323 problem...
I added your pattern to the web page ... interesting how the PCB libraries
one is so long and skinny... any advantage in that?
I posted it on my website for comments...
http://pcbwizards.com/faq.htm
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
e-mail:[log in to unmask]
http://www.dtwc.com
http://pcbwizards.com
-----Original Message-----
From: Roger Stoops [mailto:[log in to unmask]]
Sent: Tuesday, November 16, 2004 9:56 AM
To: TechNet E-Mail Forum; Brooks,Bill; Steve Gregory
Subject: RE: [TN] SOD323 problem...
Okay, I misread the package type, thought it was a SOD123. But we still
have had no problems (yet) with the 323. Used the latest version of the
PCBLibraries calculator to derive the "latest" land pattern for the SOD-323,
and the calc says 1.4x.5mm lands on 2.2mm center (3.6mm overall length).
Sent a pdf file with what the calculator came up with. For $57US, the
calculator is a pretty good buy, takes a lot of guesswork out and meets
IPC-735x standard. (http://www.pcblibraries.com)
Attachment sent to Bill and Steve, maybe Steve could put it on his website
for comments?
More Regards and some apologies too,
Roger
"Want to see how dumb a dummy can be?
Look no further, just look at me."
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brooks,Bill
Sent: Tuesday, November 16, 2004 11:44 AM
To: [log in to unmask]
Subject: Re: [TN] SOD323 problem...
The part we are using is defined on this spec sheet...
http://www.protekdevices.com/datasheets/gblc.pdf
The recommended pads are 0.8mm square and 3.0mm at the extreme dimension
from outside edge to outside edge of the pads. I don't see any reference to
this package in the IPC-SM-782.
What sort of geometries are you dealing with Steve?
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
e-mail:[log in to unmask]
http://www.dtwc.com
http://pcbwizards.com
-----Original Message-----
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Tuesday, November 16, 2004 6:40 AM
To: [log in to unmask]
Subject: Re: [TN] SOD323 problem...
Hi Bill,
The immediate fix is to make the pads larger. The real problem is a larger
CTE mismatch between the SOD323 and the PCB, and thoise leads do not even
deserve to be called leads--zero compliancy. These 'leads' need to be turned
UNDER
the component body to decrease the DNP.
BUT, neither of these steps assures a solution--it may simply move the
failure mode from ripped-out pads to fractured solder attachments.
The real solution is to turn the component upside-down and provide it with
longer compliant leads; no sacrifice in real estate..
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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