Visiting Photochemical Machining

March 2000 Visiting Photochemical Machining The photochemical machining or chemical milling industry is worth studying since it has advanced technologies which it shares with PWB fabrication. This “niche technology,” as the German title of Reference 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 micro) 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 of circuits 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