Spray etching characteristics of 42 Alloy with a fine-slit resist pattern were investigated by changing the width of photo-resist aperture, etchant temperatures (similar to 90 degrees C) and spraying pressures (similar to 6 atm). Both the etch rate and factor decreased with decreasing the width of photo-resist aperture. High etchant temperatures gave high etch rates. However, high etchant temperatures were not always effective in etch factor. Activation energies were 28.4 kJ/mol and 31.2 kJ/mol when slit patterns were parallel to and perpendicular to the rolling direction of 42 Alloy, respectively. High spraying pressures improved both the etch rate and factor by the strong blow of etchant droplets. By increasing both the etchant concentration and the spraying pressure, high accuracy and high efficiency were achieved even for the high temperature etching processes.