| 摘要 |
1,091,641. Printed circuits. SANDERS ASSOCIATES Inc. Nov. 19, 1964 [Nov. 27, 1963], No. 47228/64. Heading H1R. In a method of making a printed circuit comprising etching a copper-clad laminate, the circuit pattern is printed on the surface of the copper in tacky ink, and the printed surface is dusted with a thermoplastic powder, which is then heated to cause it to fuse where caught by the ink and so form an etchant resist and a soldering flux. Alternatively, resin or other flux is combined with the ink and printed on to the metal in a single operation. The ink may be of the " overprint varnish " type, or may be resin-based, and is applied to the copper by offset or letterpress printing; in the former case, the printing plate is preferably of anodized aluminium having the pattern formed thereon by a photographic process. In the case of letterpress printing, the printing-plate is preferably made of a light-sensitive synthetic plastics material. The thermoplastic powder may be a modified grade of gum rosin. In the etching step a hot spray is preferably used, to cause the resist to extrude around the edges of the conductor during etching, so preventing undercutting. |
