Conductive Adhesives
Conductive adhesives offer electrical or thermal conductivity between the components they seal together. The adhesives accomplish this conductivity by mixing metal powders and flakes with either single components or two-part epoxy or adhesive.
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Applications of Conductive Adhesives
The use of conductive adhesives is most common in the electronics and electrical industry. These adhesives may be used in die attachment, electro-plating, heat sink assembly, medical electrodes, solder masking, hard disk drive components, and hearing aids. They can also be specially designed to adhere flooring that controls the buildup of static. Conductive adhesives can be combined with conductive flooring to reduce foot traffic static and its detrimental consequences. Static-resistant flooring is important in workplaces that handle sensitive electronics.
Materials Used in Manufacturing Conductive Adhesives
Conductive adhesives may be made out of a variety of metals, including silver, nickel, copper, and silver-coated nickel. Silver offers the most electrical conductivity and graphite adhesive formulations have also been developed for applications in which metallic additives are not desirable.
How to Use Conductive Adhesives
Conductive adhesives can be dispensed in dots or small lines to make electrical connections between two components. Curing may be accomplished using heat, Ultraviolet light, or moisture. The heat curing process involves heating a substance to the point where it is molten and then allowing it to cool. This melting and cooling system produces another epoxy-based adhesive: hot melt adhesives.
Ultraviolet curing is done without heat but rather uses ultraviolet light to initiate the curing process of melting down and hardening. Various chemical bases of adhesives can be cured this way, but because of the electrical properties developed during the process, conductive adhesives benefit particularly. The conductive adhesive using UV light can set immediately. Moisture causes some adhesives to go through a chemical change that creates the desired bond if the environment is just right. Depending on the curing system, the chemical base, and their intended use and formulation, the conductive adhesives may be flexible or rigid, thermally conductive, moisture-resistant, and have varying degrees of viscosity.
Types of Conductive Adhesives
Conductive adhesives are either one component adhesives or multiple component epoxy adhesives. One component adhesives require heat curing and bond quickly. Epoxy conductive adhesives, however, are more complicated. Epoxies must be mixed with the conductive metal element for the specific application moments before being spread onto the object for bonding. Epoxy is usually made up of bisphenol-A and epichlorohydrin, which are both present to strengthen the bond and the humidity and moisture-resistant coating. The epoxy mix and conductive liquid are kept separate until the time they are mixed and applied.