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 Chris Mahanna <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 06/22/2011 03:50 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Chris Mahanna <[log in to unmask]> To <[log in to unmask]> cc Subject 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]>> Sent by: TechNet <[log in to unmask]<mailto:[log in to unmask]>> 06/22/2011 03:20 PM Please respond to TechNet E-Mail Forum <[log in to unmask]<mailto:[log in to unmask]>>; Please respond to Chris Mahanna <[log in to unmask]<mailto:[log in to unmask]>> To <[log in to unmask]<mailto:[log in to unmask]>> cc Subject [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. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask]< mailto:[log in to unmask]> ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 To unsubscribe, send a message to [log in to unmask]<mailto:[log in to unmask] > with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]<mailto:[log in to unmask]>: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives For additional information, or contact Keach Sasamori at [log in to unmask]< mailto:[log in to unmask]> or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------