Many cordless tool manufacturers have been focusing their attention on lithium-ion batteries. The technology was originally developed for cell phones, laptop computers and other portable consumer electronics applications.

However, lithium-ion battery packs are more complex and require extra assembly steps than other types of rechargeable batteries. For instance, lithium-ion needs to be managed electronically and mechanically to ensure safe, reliable, long-term operation.

To assemble lithium-ion batteries, operators must join multiple layers and delicate foils. Since soldering is out of the question, battery manufacturers often must choose between conductive adhesives or ultrasonic welding.

According to Janet Devine, president of Sonobond Ultrasonics (West Chester, PA), many battery manufacturers prefer ultrasonic welding, because it does not use heat, current, fluxes or fillers. “Ultrasonic welding produces better weld strength and electrical conductivity than using conductive adhesives,” she points out. “The lower resistance resulting from the ultrasonic bonding, and the ability to weld dissimilar materials [such as copper, aluminum, lithium and nickel], are additional advantages of the ultrasonic process.”