Hi, Unfortunately, a correction is needed. >1. In fact if the via hole is plugged the >mask will cushion the effect of z-axis expansion. This is not correct--where the plug helps is in the x,y-expansion trying to compress the barrel. This is important for inner-layer [post] separation. The solder mask plug actually has a worsening effect as far as z-axis differential expansion is concerned because its CTE is larger than that of copper; however, because it is soft (it is likelt to be incompressible, however), this effect is not significant. Regards, Werner Engelmaier --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------