Abstract: Shielding means for electromagnetic radiation, particularly that of radio frequency, comprises a enclosure fabricated from non-conductive material and having on at least one of the interior or exterior walls a layer of copper metal. The latter has been applied by coating the surface of the wall with a suspension of particles of cuprous oxide (or like non-conductive metal derivatives capable of being reduced to conductive free metal) in a curable resinous material, at least partially curing the coating, reducing to free metal the cuprous oxide or like particles in the surface of the coating and then electrolessly plating the coating with copper.

Abstract: Printed circuit boards having solder coated pads and through-holes and bare copper traces protected by a directly applied solder mask or by a coating of non-reflowable metal and a solder mask thereover, are manufactured by a process which avoids the need for tin-lead stripping and the need for separate application and leveling of molten solder. In the preferred process, liquid resists are applied to circuit boards having tin-lead over copper plated holes and pads so as to define and etch-protect bare copper traces of desired pattern circuitry (as well as other desired configurations). Copper areas other than those protected by the etch-resist and tin-lead plating are etched away, the etch-resist removed and solder mask applied over the bare copper traces or other desired bare copper areas or, alternatively, to bare copper first coated with a non-reflowable metal. The tin-lead plating is then preferably reflowed and solidified to provide the pads and through-holes with solder coating.

Abstract: Multilayer printed circuit boards are fabricated by preparing a first layer in conventional manner by forming a resist image on a copper clad substrate, etching away unwanted copper, removing the resist from the circuit pattern and optionally applying a dielectric mask such as conventional solder mask to selected portions of the circuit pattern. A second layer, and optionally one or more subsequent layers, are fabricated by providing an image of a second circuit pattern in a predetermined location on said first layer, the image being formed using a suspension of cuprous oxide in a curable resin material. The image is cured at least partially and subjected to chemical reduction to convert at least a portion of the cuprous oxide to metallic copper such that the unreduced cuprous oxide in resin serves as a dielectric layer.