Aluminum Technology - The Wiring Harness of the Future Next Generation Terminals for Aluminum Wire Application

Historically aluminum was recognized as a valuable material to achieve weight reduction targets in engines, vehicle chassis and suspension. Aluminum needs to be also considered in new areas like vehicle electrification to support the overall weight reduction targets. The use of aluminum helps to improve fuel economy and brings down CO2 emissions by reducing weight. This benefit is an attractive option for the wiring harness to replace heavier copper conductors. In addition to large cross section wires for power cable, where aluminum conductors are already in use, the intermediate aluminum cable cross section of 2.5mm2 to 6.0 mm2 provides a good potential for car implementation to hit weight saving targets. The major implementation roadblocks for aluminum technology are the surface oxides Al2O3 which are an insulator and the potential galvanic corrosion of aluminum in combination with the always present copper terminal. Galvanic corrosion can occur with the presence of electrolyte fluids inside the car. Traditional termination solutions are mostly dependent on the use of additive materials like paints, grease or similar approaches to protect the aluminum at the crimp area. To achieve a permanently reliable electrical contact, the termination technology between a copper terminal and aluminum wire with single strands, needs to be specifically optimized. Delphi now provides a technology named SMC (Selective Metal Coating). SMC is an innovative technical solution for a wiring harness equipped with aluminum cable. The Wiring Harness of a Vehicle Today reducing weight and simultaneously implementing more functionality is the challenge for the design of wiring harnesses. A wiring harness for a vehicle from 1960 would have a weight 3 to 5 kg. Today, a wiring harness weight can be in the range of 50 to 70 kg, dependent on the equipped functions. The potential to save weight can be identified by analyzing the cable cross section content of a premium car. It is possible to reduce some of this weight by replacing copper with aluminum for cables with cross sectional areas of 1.5mm2 or more (fig. 01). Figure 01. distribution of cable cross section Aluminum cable has the potential to reduce the weight of the wiring harnesses by up to 48% for copper cable cross sectional areas of 1.5mm2 areas or greater. Additional, cables with smaller cross sections like 0.13mm2 made from a copper alloy (CuMg), can be used for signal distribution functions and can also replace some of the bigger 0.35mm2 copper cables. Aluminum Technology The Wiring Harness of the Future Next Generation Terminals for Aluminum Wire Application 2015-01-0245 Published 04/14/2015 Markus Gaertner Delphi Deutschland GmbH CITATION: Gaertner, M., "Aluminum Technology The Wiring Harness of the Future Next Generation Terminals for Aluminum Wire Application," SAE Technical Paper 2015-01-0245, 2015, doi:10.4271/2015-01-0245. Copyright © 2015 SAE International Although replacing the copper with aluminum will result in a larger harness cross section due to the physical characteristics of aluminum compared to copper. Figure 02. shows the relation between copper and aluminum cable in terms of cross section for the same current carrying capacity Aluminum Cable Intermediate Size Aluminum cables with cross sections greater than ≥ 2,5mm2 are designed out of nearly pure aluminum. A typical alloy used is Al 99,7. For lower cross sections, due to cable mechanical requirements several alloys are available that have a higher tensile strength characteristic. Aluminum Cable, Current Load Capacity The theoretical approach of getting the current equivalent cross section between aluminum and copper is the equation (1) based on the same electrical current. The cross section is reversely proportional to the electrical conductivity. The cross section for aluminum needs to be about 1.6 times larger than for copper for carrying the same current.