Steve, The problem that you describe sounds vaguely familiar. Whilst at CSL, we examined a problem with open circuits in high aspect ration vias, under BGAs, on about the thickness of board you describe. The client had solder mask that plugged the vias on the wave solder side of the board. The mask went on before gold plating. Consequently, the sulfuric acid from the gold plating remained in the vias and cause circumferential cracking in the barrels of the holes. The client had not had a problem with the vias until they dropped under 13 mil diameter. With vias larger than 13 mil, there was enough opening for water rinsing to get down in the vias. With vias smaller than 13 mils, the surface tension of the water prevented it from getting down into the via. Imagine trying to clean out a capillary tube and you get the general idea. I wrote about this in Circuits Assembly magazine. The articles were in the Process Rx columns titled "It Cracks Me Up" and "Sulfates in Vias: The Rest Of The Story". I can furnish them if you desire, or you can probably get them from the CSL web site www.residues.com. I would say that you have to microsection to find out what is really going on with the vias. Doug Pauls Rockwell Collins --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------