About twenty years ago, there were two processes for making copper circuitry - Subtractive where etchant was used to form the circuits by taking away (subtracting) the copper foil, - and Additive where a chemically resistant plating resist was imaged on bare laminate and the copper electrolessly plated up (added) to form the traces. Today, the additive plating resists (solvent developed) are nearly gone, and the full "additive" process used relatively little except for Japan. About tweny years ago, someone thought of using conventional electroless copper on a bare laminate substrate to form a thin conductive skin everywhere. Then, aqueous plating resist could be used and the much faster electroplating process could build up the circuitry. Once plated up, the imaging resist is removed, and the thin electroless copper etched quickly to isolate the circuits. Today, semiadditve processing is used for "deposited dielectrics" - either photosensitive or laser ablated - in forming microvias. Denny Fritz MacDermid, Inc ############################################################## TechNet 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 TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################