I suggest you work closely with your dry film vendor. If he says he needs roughness, then his formulation probably does not contain an adhesion promoter specific for copper. In the past, this was a common practice, as adhesion promoters tend to be close chemical relatives to OSP final finishes and copper tarnish preventatives. It is easier for some dry film manufacturing processes to incorporate additives. There are now dry films on the market that are not coated from solvent solutions and these formulations are more similar to "hot melt adhesives". Therefore, these dry films depend on surface roughness and mechanical adhesion as they have no chemical adhesion promoter. Rudy is correct in saying that photochemical machining uses dry film on very smooth surfaces. However, I suspect that the PCM industry still uses some combination of conversion coatings, acid dips, adhesion promotion dry films, etc to achieve optimum results. For instance, films for "gold plating" probably are formulated for adhesion, while "inner layer etching" films are formulated for accurate trace width and less for adhesion. Denny Fritz --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------