Bob, Here at NASA/JPL, we have done an extensive evaluation of different surface mount components' solder joint failures including LCCs. For LCCs, an attempt was made to correlate quality of solder joints to reliability. Single LCCs of 20, 28, and 68 terminations with .050" on FR4 were used for thermal cycling evaluation. Our thermal cycle was between -55 and +100 for 4.2 hour duration. Your results when adjusted for the maximum temperature differences should come close to what we found. Please refer to few of my publication in this area: 1) "SMT Solder Joint Reliability/Workmanship Environmental Test Results Correlation for LCC Assemblies" The 20th Annual Electronics Manufacturing Seminar Proceeding., supported by Naval Air Warfare Center, Feb. 21-23, 1996, Ridgecrest, CA.. 2) "The Interplay of Surface Mount Solder Joint Quality and Reliability of Low Volume SMAs", NEPCON WEST Proceeding, Feb. 25-29, 1996, Anaheim, CA. 3) "Solder-Joint Quality with Low-Volume PCB Processintg," SMT Magazine, July 1996 Reza Ghaffarian, Ph.D. JPL 4800 Oak Grove Drive Ms 125-161 ______________________________ Reply Separator _________________________________ Subject: ASSY:FAB:Des: Joint Cracking LCCCC Author: [log in to unmask] at Internet Date: 9/10/96 12:05 PM I have been looking at some 20 pin Leadless Ceramic Chip Carriers which have exhibited cracks. They are mounted on standard FR4 and thermal cycled between -55 +80 for 1000 hours. Cracking is a problem with this device as we know but not at these low lead counts. Many uses in their design rules make 28 pin devices the limit and then incorporate the use of matched substrate to reduce differential expansion. I would appreciate any feed back on failure that people have seen on testing of low lead count devices or even feed back on where people see the limit on pin count and the need for special substrates. Bob Willis Process Engineering Consultant Electronic Presentation Services 2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England. Tel: (44) 01245 351502 Fax: (44) 01245 496123 Home Page: http://ourworld.compuserve.com/homepages/Bwillis Email: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************