I have found the best surface prep for innerlayers is a combination of a pre-dip microetch followed by an aluminum oxide scrub. The microetch (we use an SP) provides a roughened surface conducive to adhesion of the resist without the potential scrub lines associated with mechanical scrubbing. The aluminum oxide provide a polish an leave the surface virtually free of oxidation without smoothing out the topography created by the microetch. We have also found a final DI rinse slightly acidic provides better adhesion.  

Hope this helps,

Ed Cosper
Director, Quality Assurance and Engineering
Graphic Electronics Inc.

----------
From:  peer fisker[SMTP:[log in to unmask]]
Sent:  Monday, March 03, 1997 9:19 AM
To:  [log in to unmask]
Subject:  fab

subject: pretreatment of innerlayers

to improve yields in innerlayers production, we are considering the use 
of chemical cleanning instead of pumicebrush prior to lamination of 
photoresist.
there is a new trend towards using chemical cleaning only to remove 
passivation (e.g. chromate) and impurities like organics, oxides etc.
this should be achieved by a hot alkaline spray cleaner followed by a 
ordinary acidic spray cleaner.
we are using FR4-copperclad, thickness 0,10 to 0,70 mm, copperfoil; 12 
to 70 µm. the thickness of the passivationlayer is 7,0 nm (0,007 µm).

If you have had used/or are using this new principle of pretreatment of 
innerlayers, we would like to hear what was/ is your experience with the 
process. 

best regards 
peer fisker

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