| 摘要 |
A multi-level printed circuit board with at least two levels of circuitry. A substrate has a first level of circuitry, an insulating covering or layer over the entire surface of the substrate and the circuitry except in first predetermined areas, a second level of circuitry is formed over said insulating covering or layer and metallurgically bonded to form electrically conductive joints at the predetermined uncovered areas with the first level of circuitry. The method of making a multi-level printed circuit board comprises the steps of forming at least one level of circuitry on at least one side of a substrate, applying an insulating covering or layer over the entire surface of the substrate and circuitry except in a first number of predetermined areas, forming a thin adherent conductive coating over all exposed surfaces, applying a temporary mask over the conductive coating except in second predetermined areas which define the second level of circuitry on the side of said substrate, forming copper circuitry in said second predetermined areas, and removing the temporary mask and said adherent conductive coating. The formation of the second level of circuitry is repeated for as many levels as is desired, and levels of circuitry may be formed on both sides of the substrate. A final level of circuitry is formed and is covered by a final insulating coating except in final predetermined areas.
|
