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Abstract

A method for preparing a high thermal conductivity and low dissipation factor adhesive varnish for build-up (combining) additional insulation layers is disclosed, where the adhesive varnish is used for high-density interconnected printed circuit boards or package substrates. The method comprises steps of: selecting at least two epoxy resins from a group including a tri-functional epoxy resin, a rubber-modified or Dimmer-acid-modified epoxy resin, a bromide-contained epoxy resin, a halogen-free/phosphorus-contained epoxy resin, a halogen-free/phosphorus-free epoxy resin, a long-chain/halogen-free epoxy resin, and a bisphenol A (BPA) epoxy resin; adding selected epoxy resins into a pre-treatment vessel with a certain ratio; heating and mixing them well to form an epoxy resin precursor; cooling the epoxy resin precursor; during the cooling process, adding a solvent to the epoxy resin precursor to adjust the viscosity of the epoxy resin precursor; adding a bi-hardener solution, a catalyst, a solvent, and a flow modifier and mixing them well with the epoxy resin precursor; adding an inorganic filler with high thermal conductivity and mixing it with the mixture in step (d) in vacuum to obtain a suitable viscosity value; and leaving the mixture in step (e) undisturbed for a period of time to form the high thermal conductivity and low dissipation factor adhesive varnish for build-up (combining) additional insulation layers.

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First Claim