Conductive Epoxy Adhesives and Formulations

Conductive epoxy adhesives consist of an epoxy resin matrix, conductive fillers, curing agents, and other additives. Conductive fillers are further classified into metallic fillers, silver-plated fillers, inorganic fillers, and composite fillers.

Metal-Filled Conductive Adhesives

Metal fillers that can be used to prepare conductive adhesives include gold powder, silver powder, copper powder, nickel powder, nickel-palladium carbonyl powder, molybdenum powder, zirconium powder, and cobalt powder. Among these, silver has high electrical conductivity and stable performance, making it the most widely used. Although copper powder has lower electrical conductivity than silver powder, its low cost makes it a relatively ideal industrial conductive filler.

The main issue with copper powder is its susceptibility to surface oxidation. It can be modified using aminopropylmethyldiethoxysilane (KH-902) to improve dispersion and increase electrical conductivity, achieving a conductivity of \(1.31×10^{-2} \Omega·\text{cm}\).

Carbon-Filled Conductive Adhesives

Graphene and carbon nanotubes replace metals in small quantities. Nitrogen-doped graphene nanosheets (N-GNS) prepared by chemical intercalation and thermal exfoliation of graphite only require 1% (mass fraction) to reach the percolation threshold. And the conductive adhesive prepared using N-GNS as a conductive filler has better performance than the conductive adhesive prepared using carbon black or multiwalled carbon nanotubes.

Three Formulations for Epoxy Conductive Adhesives

Epoxy Conductive Adhesive Formulation

Nonionic gemini fluorocarbon surfactant

KT-703 Anionic fluorocarbon surfactant

KT-702 Nonionic fluorocarbon surfactant

Imidazole CAS 288-32-4

Oxybenzone 2-Hydroxy-4-methoxybenzophenone CAS 131-57-7

Dicyandiamide CAS 461-58-5

Hydrophobic Fumed Silica

Hydrophilic Fumed Silica

Butyl glycidyl ether CAS 2426-08-6

Tert-Butyl Glycidyl Ether CAS 7665-72-7

Performance and Application: This epoxy resin anisotropic conductive adhesive has strong bonding, high peel strength, and high insulation resistance in the packaging layer gap, which can meet the special requirements of electronic product assembly processes.

Modified Epoxy Conductive Adhesive Formulation

Performance and Application: This conductive adhesive has good bonding performance and low resistance value, making it a structural conductive adhesive. Mainly used for bonding microwave components such as copper, aluminum, gold plating, silver plating, etc., it can also be used for sealing and repairing other conductive devices

Electrically and Thermally Conductive Epoxy Adhesive Formulation

Performance and Application: This adhesive has low viscosity and high thermal conductivity and can be used for bonding and packaging electronic and electrical components.