Two types of electrically conductive adhesives provide specific benefits where an electrical interconnect is desired. Isotropic conductive materials conduct electricity in all directions equally, and can be used to replace solder on thermally sensitive components. Isotropic materials can be used on devices that require a ground path. Anisotropic conductive materials allow electrical current to flow only along a single axis (typically the Z-axis), and provide electrical connectivity and strain relief for devices such as flip chips. All electrically conductive adhesives have two common qualities: they provide a chemical bond between two surfaces, and they conduct electricity. Figure 1 is a cross-section of a die bonded to a substrate with an isotropic adhesive.
Typical electrically conductive adhesive formulations are made up of an isolating polymer resin that is filled with conductive particles. The resin provides a mechanical bond between two substrates, while the conductive filler particles provide the desired electrical interconnection.