Larry, Need more information. What type of SM are you using LPI or Dry film. Also what hole size are you using and are you trying to tent the holes. In general holes over .020 max dia. cannot be reliably tented. Only Dry film will tent well but people have hole plugging techniques for LPI. If not tenting then the holes are open and may have solder splash from HASL or left over from select solder strip. We occasionally see patches of copper with solder which was not well stripped. Bill Dieffenbacher Lockheed Martin ---------- From: [log in to unmask] Sent: Wednesday, September 24, 1997 2:47 PM To: [log in to unmask] Subject: [DESIGNERCOUNCIL] Solder Mask Problems? I have switched to SMOBC (solder mask over bare copper) and have noticed that some of the via's on the board are well covered while others seem to have only a light coating - I can see the copper hue of the traces - in some via's there is a slight splash of solder from the plating process. I don't require plugs for vac. fixtures etc. My main concern is these boards are subject to harsh conditions (coal mines) and I'm worried about corrosion at these points. Has anyone else noticed this with SMOBC? The board house suggested going to a smaller drill size for via's (015). Don't suggest a new house - these guys are great and have been working on it. What is the IPC spec for min coverage for class 2 boards regarding SMOBC? Should I be concerned? Larry Machak (designer, not cad operator!) Saminco Inc. ############################################################## IPC Designers Council Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DESIGNERCOUNCIL <your full name> To unsubscribe: SIGNOFF DESIGNERCOUNCIL ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ############################################################## ############################################################## IPC Designers Council Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DESIGNERCOUNCIL <your full name> To unsubscribe: SIGNOFF DESIGNERCOUNCIL ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################