Patent ID: 8323798

Claim:
An entry sheet for drilling circuit boards with a drilling tool, the drilling tool entering the entry sheet from the top of the entry sheet in a predetermined drilling area, the entry sheet comprising: a planar, sheeted substrate layer having a thickness of about 6 mils or less and configured to be positioned over at least one printed circuit board which is to be drilled, the substrate layer having a bottom surface and a top surface, the bottom surface having no adhesive properties and adjacent the top surface of the at least one printed circuit board to be drilled; and an entry sheet component provided over the top surface of the substrate layer, wherein the entry sheet component has a thickness of about 6 mils or less; wherein the substrate layer comprises at least one layer of aluminum; wherein the entry sheet component comprises, in a single layer, a coating coated on the top surface of the substrate layer, such that the drilling tool first passes through the coating during drilling of the circuit board, the entry sheet component comprising a fully cured, completely hardened, fully thermoset epoxy resin adhesive composition, the composition comprising: bisphenol a/epichlorohydrin-based epoxy with no thermoplastic resins, a curing agent, and a salt, comprising between about 25% and about 45% by weight of the entry sheet component, based on the total weight of the entry sheet component, whereby the entry sheet component is configured to degrade to dust upon drilling; wherein the entry sheet component is in a fully cured, completely hardened state when the substrate layer is positioned over the at least one printed circuit board.