Importance

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Abstract

A method for filling a hole in a printed wiring board (PWB) and the resultant PWB. During an intermediate stage in fabrication, a PWB comprises a lamination of dielectric sheets with metalizations on various layers and a plated through hole (PTH). A photoimageable material is formed on a surface of the laminate and covers the PTH. The photoimageable material in a region covering the PTH is partially cured by exposure to light. The remainder of the photoimageable material is developed away. Then, the partially cured photoimageable material in the region of the PTH is pressed into the PTH to form a plug. By application of heat during or after the forcing step, the plug is further cured to a hard condition. For some applications, the plug is mechanically abraded to be flush with one or both surfaces of the laminate. The plug can serve as a solder mask or permit another layer of low viscosity photoimageable material to be formed over the laminate such that the hole, now plugged, will not interfere with the formation of such additional layer.

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First Claim