Using large plane areas of solid copper under soldermask at one time presented a problem because the copper was tin/lead coated before soldermask and when heated during the assembly process might reflow and cause chipping , flaking, bubbling, etc. of the soldermask. Using soldermask over bare copper (SMOBC) prevents this from being an issue and should not present a problem for you to use large solid ground areas on the outer layers if that is what is preferred. Tim Easterling SCI Systems Inc. (205) 882 4426 ################################################################ DesignerCouncil E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################