re: copper contamination I believe one of the most looked-over design opportunities to reduce copper introduction into solder pots is to cover via pads with solder mask. The most numerous feature on most PWB designs (and still abundant on all-SMT designs) is the PTH via. By covering the via pads in solder mask you reduce the amount of copper exposed to the solder pot by a significant percentage without the cost associated with via plugging. Simply modify the solder mask layers to remove solder mask pads from the vias locations. For PWB vendors that use screen-applied solder mask, a small dot pattern might be desirable to limit the amount of mask introduced into the vias, and is something that can be created by the vendors themselves. Vendors using curtain coat or spray-applied solder mask apparatus can run without any modification. An additional "plus" is that every via covered in solder mask is also an eliminated short opportunity, either as a solder short (bridging out of wavesolder) or as a component contact short (e.g., XTALs and other metallic casings). The CON to covering vias with solder mask is Test Point applications: If you are using vias as test points for ICT or subsequent diagnostics you'll have to ensure that the test point vias are exposed. Cheers! Bob Lazzara Circuit Connect - Atlanta www.CircuitConnectInc.com --------------------------------------------------------------------------------- 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------