I can not help you with the history of the changes allowing solder in the upper bend on gull wing leads in J-STD-001B (paragraph 9.2.6.1, Figure 9-4, Note 1) and MIL-STD-2000A (paragraph 4.23.7.5). However, technically this change makes sense. Gullwing leads, particularly in fine pitch, have ample lead compliancy to accommodate the small thermal expansion mismatches between a PLCC and FR-4 substrate. Thus, the small loss of lead compliancy due to the solder (solder has a low modulus of elasticity that is even lower at elevated temperatures) in the shoulder bend has for no practical consequence. However, to my knowledge nobody has ever experimentally verified this--this test would be very time consuming. The above would not be true, if the component is a CLCC. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 Phone & Fax: 201-543-2747 E-mail: [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. * ***************************************************************************