Hi David, I wrote the following in my White Paper Report: 'Recommendations for PCB FAB Notes and Specifications in Printed Circuit Board Drawings for SnPb and Lead-Free Soldering Assemblies, the Qualification of PCB Shops and Activities to Assure Continued Quality,: "Also, in order to reduce the z-axis thermal expansion, various fillers are added. This has in some cases reduced the cohesive strength of the material and has led to cohesive delamination failures. Unlike an adhesive failure resulting from a delamination at the copper-to-resin interface, cohesive delamination is totally within the dielectric material, as shown in Figure 1. Specifically, IS410 [STII=225]has been variously implicated as being prone to delamination at high soldering temperatures, particularly at power and ground planes, even though it meets the properties for ‘Advanced Lead-Free Compatible Laminates’ in Table I. The indication is that there may be an incompatibility with the phenolic material and the oxide coatings. Improving some properties individually can easily be achieved but may be at the expense of other properties; thus, it is imperative that a proper balance of properties meeting the needs of the product be achieved. It is easy to understand, that these needs will vary significantly with (1) the end use, such as high-end servers, telecommunications, high-end servers, avionics, military, medical or automotive, (2) PCB design and construction, such as thin PCBs with few layers vs. thick complex many-layered PCBs, and (3) the type and number of lead-free soldering steps, such as HASL, wave, reflow, vapor phase, repair and rework. Therefore, PCBs of new constructions and new materials and destined for lead-free solder assembly need not only be properly selected according to their data sheet information, but need to have coupons tested in the product configuration." I am also receiving reports on Nelco 4000-13 [STII=247] with similar problems. For best results it seems that non-dicy/non-phenolic materials wouls be best; they yield STII values in excess of 250, whereas dicy-dured seem to top out at 210-220 and phenolic-cured at about 230-245. While the STII-value is a useful pre-selection indicator, the quoted last paragraph needs to be heeded. Regards, Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------