Positive Dry Film Photoresist for Fine Line Circuitry
The printed circuit (rigid and flexible), hybrid microcircuits,
and photochemical machining industries in the past few years
have been pushed harder and harder for fine line and space
geometries. The means of achieving these have been limited to
liquid negative or positive resists or negative dry films.
Liquid resists can be applied by means of spin coating, roller
coating, dip coating, or spray coating. Loss of material or solvent
loss can make this an expensive, as well as a difficult, process to
control. Also required for this process is some form of a dryer to
remove solvents and cure the resist prior to exposure.
Leo Croucher, 3M Company