Anisotropic conductive adhesives

Abstract

Anisotropic conductive adhesives (ACAs) are a set of materials typically combining either epoxy or acryl adhesives and conductive particles to allow electrical connection across what would otherwise be a standard mechanical adhesive assembly. They differ from isotropic conductive adhesives such as silver epoxy in that the conductive particles are loaded and distributed in such a way that they do not conduct within the bulk of the adhesive but do conduct in the Z-axis when they are trapped between electrodes on the top and bottom substrates. This allows them to offer some unique advantages compared with isotropic adhesives or various solder technologies. In the case of touch panels, these advantages are primarily related to its low temperature and high interconnect density capabilities, although cost and speed of assembly may also be considerations. ACAs are widely used in the display and electronics assembly industries. In flat panel displays, they are used to make the connection between the drive circuitry and the display itself. They are also used extensively in other applications that require high-density and/or low-temperature assembly at high volume. This includes touch panels, camera modules for mobile phones, touchpads for notebook computers, and RFID assemblies for smartcards. ACAs have also had limited success in semiconductor packaging, but the reliability requirements for these applications are not always possible to achieve with ACA technology.