Drill back-up material for small bore drilling of circuit boards

摘要

Disclosed is an improved back-up sheet for backing a workpiece during a small bore drilling process. The sheet also possesses electrical properties making it an ideal candidate as a laminate (reinforcing layer or bonding sheet) in the construction of multi-layer printed wiring boards. The sheet or laminate comprises the cured residue of:(a) polyphenylene oxide;(b) a bisphenol A-type epoxy resin; and(c) an amine hardener for said epoxy resin, the weight ratio of a:b+c ranging from about 1:10 to 1:2.