March 2000
Visiting Photochemical Machining
The photochemical machining or chemical
milling industry is worth studying since it has
advanced teclmologics which it shares with PWB
filbrieation. This “niche technology,” as the
German title ofReference 1 implies, deals with
very demanding precision requirements and fine
geometries. During a recent visit to
photochemical machining shops I have seen more
2-3 mil (50-75 microo) feature work than in any
”high tech” PWB shop.
Photochemical machining has steadily expanded
into electronic packaging. Examples are lead
&ames (Ref. 2), EM! shielding, and flexible
circuits that require etching or plating ofcircuits
as well as etching of KaptonlJ) polyimide layers.
This industry is using materials familiar to PWB
fabricators, such as photoresists, developers,
etchants, and strippers. Process equipment may
be identical to PWB fabrication. but you might
find morc tank processing than conveyorized
spraying. and there arc industry-specifiG-process
alterations, such as “barrel” plating.
Karl Dietz, DuPont Printed Circuit Materials
