When people look at the liquid crystal display on their cell phone or television, they arent thinking about how the pictures get there. Even if they were, few would entertain the idea that adhesives play a crucial role in turning electrical signals into images. But thats just what anisotropically conductive adhesives (ACAs) do. By forming films that conduct electricity in one dimension but are insulating in the other two, they can connect matrices of electrodes that pass signals to the individual pixels of an LCDs. These products have been in existence for some time , but innovation continues apace as higher-resolution displays and slimmer electronics shrink the space between electrodes.

ACAs are typically made by filling relatively conventional epoxy insulating adhesives with conductive particles, which are either pure metal or metal-coated polymer. They must cure in seconds under high-temperature, high-pressure, thermocompressive bonding between an IC and display electrodes formed on the glass substrates in the LCD. The conductive particles can form a connection when theyre trapped between these raised electrodes, while the adhesive ensures that each connection is electrically isolated. As technology trends shrink the spacing in the matrix pattern of electrodes, the conductive particle size must be reduced. This poses challenges to formulators in this high-value market so great that some users have turned away from ACA films. However, some recent inventions claim to have resolved this issue.

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