Circuit board unwoven fabric, circuit board prepreg using same and circuit board using same
A circuit board nonwoven fabric comprising a paper-formed structure which comprises a plurality of thick fibers in which the portion of greatest fiber diameter is 5 μm or greater, and a plurality of fine fibers in which the portion of greatest fiber diameter is less than 5 μm, wherein an average fiber length of the thick fibers is greater than an average fiber length of the fine fibers, the number of fine fibers is greater than the number of thick fibers, and the thick fibers have a flat shape with a major axis and a minor axis, the minor axis being oriented in a thickness direction of the paper-formed structure.
1 . A circuit board nonwoven fabric comprising a paper-formed structure which comprises a plurality of thick fibers in which the portion of greatest fiber diameter is 5 μm or greater, and a plurality of fine fibers in which the portion of greatest fiber diameter is less than 5 μm,
characterized in that an average fiber length of the thick fibers is greater than an average fiber length of the fine fibers,
the number of fine fibers is greater than the number of thick fibers, and
the thick fibers have a flat shape with a major axis and a minor axis,
the minor axis being oriented in a thickness direction of the paper-formed structure,
wherein the fiber diameter of the minor axis of the thick fibers is 10 μm or less, and
wherein the fiber diameter of the major axis of the thick fibers is 5 μm-20 μm.
2 . The circuit board nonwoven fabric as claimed in claim 1 , wherein the thick fibers and the fine fibers are aramid fibers.
3 . The circuit board nonwoven fabric as claimed in claim 1 , wherein the proportion of the total area of a nonwoven fabric CD cross section occupied by the thick fibers is 10% or less.
4 . A circuit board prepreg wherein the circuit board nonwoven fabric as claimed in claim 1 is impregnated with a resin.
5 . The circuit board prepreg as claimed in claim 4 , wherein the prepreg thickness is 120%-300% of the circuit board nonwoven fabric thickness.
6 . A circuit board wherein a circuit pattern is provided on a surface of the circuit board prepreg as claimed in claim 4 .