In the manufacture of printed circuit cards and boards, a dielectric sheet material is employed as the substrate. A conductive circuit pattern is provided on one or both of the major surfaces of the substrate. In order to provide electrical connection between layers, metal coated through-holes are provided. Notwithstanding the improvements over the years in processing sometimes defective plated through-holes are produced, including insufficient coating or discontinuities in the coating in the through-holes. In order to avoid discarding the entire board or card in the event of a defective plated through-hole, the hole is reworked and refilled in order to prepare the board or card for subsequent rewiring to compensate for the defective hole. Certain epoxy compositions have been used for this purpose. Although epoxy compositions used for this purpose have been adequate, the glass transition temperatures of such compositions are not especially high, such as about 50.degree.-60.degree. C. With the increase in potential operating temperatures to which the boards or cards are likely to experience in the future, the stability of the rework hole fill could be adversely effected in view of the relatively low glass transition of the epoxy composition employed.
USPTO Backgrounds
USPTO Backgrounds