| 摘要 |
<p>1276535 Printed circuits GYLLING & CO AB 11 July 1969 [12 July 1968] 35094/69 Addition to 1240007 Heading H1R [Also in Division C7] A process for preparing a circuit board for the subsequent formation of a conductive through hole by electroless deposition of a metal comprising the steps of providing a circuit board having a substantially smooth surface with a roughness less than a predetermined value, forming a through hole through said circuit board, having walls whose surface roughness is greater than said predetermined value, treating the circuit board with a preparation containing salts of tin and palladium to form a lyophobic colloidal layer of a complex palladium : tin chloride colloid thereon, and immersing the thus treated board in a stripping agent for the complex colloid for a sufficient time to remove substantially all of the colloidal layer from said smooth surface, but insufficient to remove all the colloidal layer from the surface of the hole. The circuit board may also be provided with further surfaces, the roughness of which is greater than the predetermined value and which subsequently have a metal electrolessly deposited thereon in the manner described above. Said preparation contains stannous chloride, palladium chloride and hydrochloric acid, and may further contain sodium stannate. Said stripping agent may comprise an aqueous solution of ferric chloride, an aqueous solution of aluminium sulphate, or a solution of an organic stripping agent such as oxalic acid, diacetyldioxime, anthranilic acid or 8-hydroxyquinoline. The substantially smooth surface may be provided by the application of a protective varnish. The thus treated circuit board may then be treated with a neutralizing agent, and finally treated in an electroless plating bath to deposit a conductive metal, e.g. copper, on the remaining colloidal layer on the circuitboard.</p> |
