Sarraf, D. and Schmidt, H., "Electrical Crimp Consolidation," SAE Int. J. Engines 10(4):2017, doi:10.4271/2017-01-1646.
Aluminum wire is receiving increased attention for automotive applications due to the potential for cost and weight savings. Termination of aluminum wire is problematic due to the tenacious surface oxide on the strands. The oxide is an electrical insulator and is difficult to displace during termination. Consequently, many of the strands within a crimped wire bundle can be electrically isolated from the terminal, which can result in higher than expected crimp resistance, less stable crimp resistance, and the potential for excess heating of the termination. Prior solutions employed additives such as brass powder to puncture the oxide film and form a diffusion bond between strands, or features such as screens or serrations that increase wire deformation and displace the oxide mechanically to promote strand-strand bonding. Both solutions have drawbacks. Additives increase cost and process complexity and can serve as contaminants to adjacent processes. The required features can be difficult to produce and may require high crimping effort. This present work uses an electrical potential applied at the moment of crimp formation to puncture the surface oxide and allow the formation of conductive a-spots. Increased current flow then welds the wires together at the a-spots to increase electrical conductivity and stabilize the crimp mechanically. A simple nodal resistor model was developed to explain operating principles and to help predict the correct working parameters. The process was implemented on a bench press with 6mm2 wire. Test data showed a significant reduction in crimp resistance over unprocessed terminals, and the resulting process is clean and requires no consumables.