Hi Peter, You are correct. If you plate the barrel on the thin side and the hole diameter is large, the hole wall will buckle [plastically deform] inwards. On cooling this causes 'resin recession' or 'hole-wall pull-away,' and inner-layer [post] separation on layers near the surface. Most through-holes nowadays are however small-diameter vias, which are more susceptible to barrel cracking. Regards, Werner In a message dated 03/27/2003 19:27:43, [log in to unmask] writes: >I heard stories in my last Company about barrels in holes for PTH >components being "too small" or " too deformed' to permit components to be >fitted. Turned out to be a combination of finished hole diameter not having >sufficient component lead/solder clearance and barrel-crushing through >board expansion/contraction. Maybe wrong choice of PCB materials as well, >I don't know. It was remarked, however, that the effects would have been >greatly mitigated if n.f. pads had been retained. --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------