| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of insulation by using an epoxy resin composition containing specified wt.% of an inorganic filler with a specified average particle size to a resinous solid component. SOLUTION: A layer contacting copper foil is made from an epoxy resin cured by dicyandiamide, and other layers are made from an epoxy resin cured by a phenolic novolak resin. An epoxy resin is mixed with a curing agent and a curing accelerator to make varnish, and a backing is impregnated with the varnish and dried to make a prepreg. In this process, the epoxy resin composition to be used contains 10-20wt.% of an inorganic filler of 1-5μm average particle size to a resinous solid component to have moisture resistance and electrolytic corrosion resistance.
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