Dear TechNetters ... Ah, I can now rest. I found the reference I was looking for. It is in IPC-4104, and so the scope is more narrow. For HDI materials there is a stated preference of TMA. See: IPC-4104 Specification for High Density Interconnect (HDI) and Microvia Materials page 14, section: 3.9.15 Glass Transition Temperature: "The preferred method for determining Tg is TMA extension (see IPC-TMA-650 Method 2.4.24.5, method A or B)." And 3.9.1.6 CTE above and Below Tg: "The preferred method for determining CTE is IPC-TM-650, Method 2.4.24.5 method A or B." Method 2.4.24.5 is: "Glass Transition Temperature and Thermal Expansion of Materials Used in High Density Interconnection (HDI) and Microvias - TMA Method." So, what do they mean by "HDI"? Reading the document, in boils down to the thinner surface layers, equal to or less than .006" thick, used in conjunction with microvias, "these vias are the central characteristic of HDI". I thought I would send this along to close the loop, in case anyone else wants some independent industry "body of experts" to reference, in addition to the many good and thorough papers on this topic. Rgds, Valerie --------------------------------------------------- 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 -----------------------------------------------------