Patent ID: 8088490

Claim:
A halogen-free varnish, comprising: A) composition (A): a resin, wherein the resin includes a bisphenol-A novolac epoxy resin, a first phosphorus-containing novolac epoxy and a second phosphorus-containing novolac epoxy, wherein the first phosphorus-containing novolac epoxy is a side-chain phosphorus-containing novolac epoxy, wherein the first phosphorus-containing novolac epoxy is a novolac epoxy resin linked with an organic ring in which one vertex of the ring is occupied, or formed by a phosphorus atom, wherein the first phosphorus-containing novolac epoxy is an o-cresol novolac epoxy resin linked with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is shown as formula 1, wherein the second phosphorus-containing novolac epoxy is a novolac epoxy resin linked with an organic ring in which one vertex of the ring is occupied, or formed by a phosphorus atom, wherein the second phosphorus-containing novolac epoxy is an o-cresol novolac epoxy resin linked with formula 2, wherein the weight ratio of the combined first phosphorus-containing novolac epoxy and the second phosphorus-containing novolac epoxy of composition (A) to the bisphenol-A novolac epoxy resin of composition (A) ranges from 0.72 to 1.4; B) composition (B): a curing agent, wherein the curing agent includes a benzoxazine resin and a phenol novolac resin; C) composition (C): a flame-retarding agent; D) composition (D): an accelerator; and E) composition (E): fillers.