...JUST SCRATCHING THE SURFACE... There has been years and years of exposed copper if you factor the edge traces. They are never solder coated. Same is true for any selective strip process. The issue of exposed copper being a bad reliability issue comes from inside the plated through hole. The fear or more appropriately; the worst case analogy is the weakest point of copper plating is the location of least plating. This would be the vertical mid point of the hole. Given a "quasi-uncontrolled" methodology: copper plating (back in the day) and potential large nodule size; copper oxidization would perpetuate lessening of elastic limit and induce work hardening then -walaa- add Z axis rotation and PWB failure. Condense this all down to a simple rule: NO BARE COPPER, and conjecture upon conjecture has bare copper an ominous foe lurking in the shadows. Well, at least that's how I recall the "bare copper" fail safe stories back when suggesting polyimide was seen as witchcraft. Boston Brad --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------