Freudenberg Sealing Technologies is launching an impermeable rectangular busbar overmold that seals reliably and helps prevent damage to an electric vehicle’s power electronics. The company said this solution also reduces assembly complexity by combining the busbars, seal and guide in one complete package that is ready for installation on the vehicle assembly line. The new product will be showcased for the first time at the upcoming Battery Show in Detroit.
Oil-cooled electric motors are commonly employed in various electric vehicles. To maintain reliable vehicle operations, Freudenberg said it is crucial to protect sensitive power electronics within the inverter from exposure to motor oil by sealing around the busbar motor/inverter interface. Additionally, other electrical busbars with rectangular geometries, like those found in immersion-cooled batteries and oil pumps, also require sealing along their metallic cables. This necessity underscores the importance of establishing a permanent seal for the current-carrying rectangular conductors, often referred to as ‘busbars.’
However, achieving tight seals with busbars having rectangular geometries poses challenges, the company said. Traditional busbars are die-cut from copper or aluminum sheets and then bent to the desired shape. The resulting rectangular busbar is not ideal for standard sealing, as the corners prevent effective compression of the sealing material. Even attempts to enhance the contact surface with partially embossed edges or press-on structures do not yield satisfactory sealing results. Post-processing methods like potting can be used but are time-consuming and impractical for large-scale industrial applications. They also require additional space, limiting busbar design flexibility.
Freudenberg Sealing Technologies said it succeeded in developing a sealing innovation that reliably seals rectangular busbars and can prevent associated damage to the power electronics in electric vehicles. This recently patented, sealed, rectangular busbar overmold includes an elastomeric layer, which is applied to the rectangular busbar and bonds firmly with the metallic conductor and the surrounding plastic later in the manufacturing process.
The company said the new busbar seal configuration enables an impermeable bond created by chemically pretreating the conductor surface with a primer and applying a special elastomeric coating. This creates a firmly bonded intermediate layer, which is followed by thermoplastic injection molding. At the same time, Freudenberg said the flexible coating reduces stress on the threshold between the copper and the thermoplastic matrix. The elastic coating reduces the notch effect at the conductor edges, which minimizes the susceptibility of the electronic component to stress cracking.