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
-----------------------------------------------------