| 摘要 |
In a method of etching wherein those portions of a metallic surface not protected with a resist are dissolved with an etchant, the etchant is supplied continuously in the form of a foam to those parts of the surface not protected with the resist. The foam may be produced by aeration of the etchant (e.g. using small jets of air or another effectively inert gas) of a bath of etchant to cause a foam to form upon the top of the etchant, the surface to be etched being so positioned that it will not be in the liquid etchant but will be covered by the foam being continuously supplied by aeration. The etchant may be aqueous ferric chloride and may contain a foaming agent (e.g. that sold under the Registered Trade Mark "TEEPOL"). When copper is being etched and the etchant has become fouled with copper it may be regenerated by electrolysis using two graphite anodes and a brass plate disposed between the rods as cathode. The apparatus used in the etching may comprise a narrow tank 1/3 filled with etchant wherein compressed air is forced through holes in the wall of a pipe extending along the bottom of the tank so as to fill the space above the etchant with foam. The top of the tank may be double walled the inner wall being provided with a series of holes, and the outer wall connecting with a fume escape tube. |
