Dec 2006
Effects of Anti-Puddling Pre-Etch on Etch Uniformity for Chemical Machining
Etchant puddling on the top surface of large panels is an
effect that has been known for many years. Because the
etchant is generally sprayed on the surface of a panel
faster than it can run off it tends to build up or puddle on
the center of the panel. The result is a differential etch
rate across the top surface of the panel; the rate being
the slowest in the center of the panel where the puddle is
deepest and gradually increasing towards the edge of the
panel where the etchant pool is thinnest due to runoff.
The difference in feature sizes between the center of the
panel and the edges, whether line widths on a circuit
board or hole diameters in a chemically machined panel,
can be quite dramatic and have a very detrimental affect
on yields.
Don Ball, Process Engineer, Chemcut Corporation, State College, PA, USA
