Hi Chris - sorry for the slow response. Part of the answer for the 
difference in solder joint heel fillet requirements is the lead geometry. 
An "L" shape has less compliancy than the "J" shape so having additional 
solder provides some additional solder joint integrity life. In many 
product use environments, we would be hard pressed to demonstrate a 
statistical difference in solder joint integrity for the two 
configurations and in many cases, even if there was a statistical 
difference, the practical difference may be zero. However, the JSTD-001 
committee has used past/present solder joint integrity data to establish 
the current solder joint fillet requirements for the whole of the 
industry. The requirements can be revised if new data/test results are 
submitted to the committee supporting a change in the requirements. You 
can use the IPC SM 785 specification to calculate a first order difference 
estimate. Hope this helps.

Dave



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Re: [TN] Min fillet height gull/J vs. L






Yes.  Although I suppose 7.5.9 vs. 7.5.13 is a better example in that both 
are inward formed.
Chris

From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Wednesday, June 22, 2011 4:28 PM
To: TechNet E-Mail Forum; Chris Mahanna
Cc: [log in to unmask]
Subject: Re: [TN] Min fillet height gull/J vs. L


Hi Chris - for clarity reasons, which figures in IPC JSTD 001 are you 
comparing? Section 7.5.7 vs 7.5.13?

Dave Hillman
Rockwell Collins
[log in to unmask]<mailto:[log in to unmask]>

Chris Mahanna <[log in to unmask]<mailto:[log in to unmask]>>
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[TN] Min fillet height gull/J vs. L







Hello all, can someone tell me-
What is it that necessitates the ~25% H additional height to a L-lead 
fillet when compared to J or gull?
My guess would be diff. CTE and J, Gull have some relief, but I need more 
than a guesstimate.

Thanks in advance,
Chris


Chris Mahanna
Robisan Laboratory Inc.


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