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May 2008

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Subject:
Re: 0402 anti-tombstoning land pattern
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 22 May 2008 16:00:04 -0500
Content-Type:
text/plain
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text/plain (63 lines) 
Thank you all very much for your information. I really appreciate it a
lot. Don't know what I would have done without Technet. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Thursday, May 22, 2008 1:10 PM
To: [log in to unmask]
Subject: Re: [TN] 0402 anti-tombstoning land pattern

Hi Gramsey,
The SJ strength is not an issue-however, the solder joint height is. If
the gap between the soldering pad and the component metallization is
small, that connection fractures relatively shortly in the live of chip
components [depending on the size of the T-cycles, of course] and the
solder connection hangs onto dear life by the fillet-I look at this as a
Band-Aid approach.
It is much better to increase that SJ gap because that dimension, h in
the Engelmaier-Wild creep-fatigue model, is a primary parameter in
increasing reliability. That increase can come from stacking the CC off
the PCB, by gluing it down [the glue thermal expands during the
soldering process creating a sizable gap], by swimming it up [only
possible if you do not have a fillet] creating a solder ball/column.

Werner
Future workshops:
Reliability Issues with Lead-Free Soldering Processes, June 17, London
Interconnect Failures and Design for Reliability for PCB PTHs, June 17,
London Pb-Free Soldering Processes-Survival, Quality, Reliability,
August 18, Orlando Reliability Issues with Lead-Free Soldering
Processes, September 22, Schaumburg Failure Mode and Root Cause Analyses
Reliability (Fatigue, Brittle Fracture, ENIG), September 22, Schaumburg



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