Printed circuit board

DETAILED DESCRIPTION What is claimed is: 1.
A printed circuit board comprising a non-conductive substrate and at least one conductive line printed on said substrate, said line comprising a U.
V.
cured ink comprising a cycloaliphatic epoxy resin containing 25-67 volume percent of silver-coated magnetite particles, said line having been subjected to a magnetic field sufficient to move the magnetite particles to a position at or near the upper level of said line so as to increase the conductivity of said line to the desired level and cured by exposure to U.
V.
radiation in the presence of a cationic photoinitiator.
2.
The printed circuit board of claim 1 wherein said U.
V.
curable ink is cured also in the presence of a plasticizing amount of a polyether polyol.
3.
The printed circuit board of claim 1 wherein said non-conductive substrate is a polyolefin, a polycarbonate, a polyvinyl halide or a polyester.




Description:
BACKGROUND OF THE INVENTION In the past few years there has been a tremendous amount of activity in the area of replacing "subtractive" printed circuit boards with "additive" printed circuit boards.
There are major environmental, economic, and marketing reasons for the interest expressed in this technology.
Two of the more important reasons are the growth of the electronic industry and the environmental problems associated with traditional copper "subtractive" circuit boards which consume resources, such as the copper foil itself, as well as the process itself which generates hazardous waste.
In an effort to overcome or minimize the disadvantages associated with the production of "subtractive" printed circuit boards, membrane switch circuit boards were developed in the late seventies and early eighties.
These circuit boards were generally silver loaded resin inks printed on polyester films.
However, they exhibited rather low voltage and current carrying capabilities and were employed principally in the field of simple switches and not as true printed circuit boards.
It is also important to distinguish additive technologies, such as CC-4 boards which rely on electrodeless copper plating to achieve an additive circuit board from the present invention