01
Preface

In the automotive industry, there is a strong demand for weight reduction of parts for environmental protection and energy saving reasons. Because of the environmental awareness in recent years, people’s environmental awareness has been increasing. At the same time, there have been concerns about resource depletion and the sudden rise in the price of copper as a conductor material. Copper is the conductor material of existing wiring harnesses. Therefore, finding an alternative material to copper is one of the great challenges facing wiring harness manufacturers.

We focus on aluminum because it is lightweight, affordable, and abundant in variety. We have made progress in the development of aluminum wires using

aluminum alloys as conductor materials and peripheral technologies for applying aluminum wires to wire manufacturing.

We have just completed the development of automotive wiring harness (aluminum wiring harness) installation technology using aluminum wire. We have decided to install this wiring harness on mass-produced cars from 2012. In this mass-produced car, the weight of its rear door wiring harness was reduced by about 15% by adopting aluminum wire.

02
Composition

The wiring harness is a product composed of various components such as wires, terminals, connectors and protectors. Generally speaking, the weight accounts for about 60-70% of the total weight as shown in Figure 1. The aluminum wiring harness changes the original copper wire to aluminum wire, which greatly reduces the weight.

Figure 1 Wiring harness weight ratio per component

03
Attributes

To adopt aluminum wire, the development of aluminum wire itself and its peripheral technologies are important. We will explain the three main characteristics of these technologies:

“alloy materials used for wires”, “aluminum wire connection technology”, and “electrochemical corrosion countermeasures for terminal parts”.

3.1 Alloy materials used for conductor bodies

We developed a 1000 system aluminum that slightly adds iron, copper, and magnesium to aluminum. This alloy material is an alloy developed by Furukawa Electric itself, called MS2AL,

which has a good balance of the five properties required for wiring harnesses: electrical conductivity, connection performance, mechanical strength, flexibility, and bending performance.

3.2 Aluminum Wire Connection Technology

To ensure stable performance of aluminum wire electrical connection, we developed a terminal suitable for small-sized aluminum wire. We developed a terminal for small-sized aluminum wire with a cross-sectional area of ​​2.5 square meters or less. Aluminum wire has a strong oxide film on its surface. To achieve excellent electrical connection, the following issues are very important. They are: dents caused to the wire harness when crimping the terminal, wire elongation caused by strong pressure, and grooves (called “serrations”) formed by the wire penetrating into the wire connection part.

The aluminum wire terminal is designed to effectively remove the oxide film. The expansion length of the wire barrel is optimized according to the wire diameter, the shape of the terminal is about 60% of the wire compression ratio, and the edge part is increased by changing the sawtooth shape.

This aluminum wire terminal makes electrical performance compatible with mechanical strength as shown in Figure 2, and guarantees excellent connection performance, which cannot be obtained with conventional terminals.

Resistance and strength capabilities of aluminum wire terminals (left) and conventional terminals (right)
Aluminum wire (left) and conventional terminals (right)
(In this case, resistance <1.0mΩ and strength >70N are required).
The acceptable C/H range of aluminum wire terminals is very wide (arrow range in the figure), which can achieve both electrical and mechanical performance
Figure 2 Connection characteristics of aluminum wire terminals

Since there is an oxide film on the aluminum wire, there will be problems with unstable electrical connection when using it. Therefore,

we decided to pre-treat the wires larger than 2.5 square feet and connect the wire tips with ultrasonic solder or ultrasonic welding. As shown in Figure

3. By crimping the welded wires, even large-sized wires can be effectively electrically connected.

Figure 3 Ultrasonic welding and crimping of aluminum wire

3.3 Countermeasures for electrochemical corrosion of the terminal part

The terminals of the wiring harness terminal part are generally made of brass or copper alloy. This raises concerns that the connection area between the aluminum wire and the terminal will be electrochemically corroded due to the external environment.

In automotive environment installation, there is a problem of electrochemical corrosion in the part using aluminum wire, and anti-corrosion treatment is required in the terminal part. In terms of anti-corrosion methods, we have developed an environmental deprivation method that uses resin materials to block the contact interface between the aluminum conductor and the copper terminal from the outside.

According to the requirements of our automotive manufacturer customers, we have integrated two anti-corrosion treatment methods. Figure 4 shows the molding method and the dripping method.

Figure 4 Anticorrosion methods

04
Aluminum wire weight reduction lineup and effects

Currently, we have prepared aluminum wire products with a size greater than or equal to 0.75 square, as shown in Table 1. Its conductor standard is based on ISO standards.

Halogen-free materials are used for insulation. The allowable temperature limit is 80℃.

When replacing copper wire with aluminum wire, aluminum wire that is one size larger than copper wire is usually selected due to the difference in conductivity between copper and aluminum.

Therefore, copper wire greater than or equal to 0.5 square is the target replacement wire for aluminum wire.

If aluminum wire is used to replace copper wire, the weight of the wire can be reduced by about 30-40% (depending on the size of the wire). In addition, as a whole wire harness,

the weight can be reduced by about 10-20% (depending on the application or implementation scope).

05
Future plans

We have completed the technology development required for the commercialization of aluminum wire harnesses. Increasing the proportion of aluminum wire usage will be an important issue in the future.

To increase the proportion of aluminum wire usage, it is necessary to “reduce anti-corrosion costs” and “expand the types of wires” (Figure 5).

Since copper wire does not require anti-corrosion treatment, its cost will increase net after using aluminum wire. By minimizing the net increase in cost, the replacement of aluminum wire can be accelerated.

In addition, the current product lineup only includes ordinary wires that can withstand high temperatures of 80°C. Therefore, it is difficult to adopt it in parts that require

heat resistance and bending resistance. By expanding the types of wires such as heat-resistant wires, the use of aluminum wires is expected to increase.

We plan to continue developing this technology, focusing on the two development themes mentioned above:

weight reduction by maximizing the use of aluminum wiring harnesses.

 

Hongchen Electronics has been continuously promoting technological innovation, improving product performance and reliability to meet market challenges and opportunities!

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