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Aluminum Wire Harness

1.

INTRODUCTION

In the automobile industry, demand for weight reductionof the parts has been extremely strong because environmental awareness has been increasing in recent years. At
the same time, there have been constant concerns for theresource depletion and the sudden rise in the price ofcopper, which is a conductor material for the existing wire
harness. Therefore, search for an alternate material tocopper is one of the great challenges for wire harness
manufacturers.
We focused attention on aluminum because of its lightweight, its moderate price and its abundance. We haveadvanced in the development of an aluminum wire usingaluminum alloy as a conductor material and in the peripheral technology to apply the aluminum wire to a wire harness.
We have just completed the development of an installation technology of a wire harness using aluminum wires(aluminum wire harness) to automobiles. It has alreadybeen decided to be installed in a mass-production automobile from 2012. In this mass-production automobile, its
backdoor harness trimmed weight to about 15% byadopting the aluminum wires.

2.

COMPOSITION

A wire harness is a product manufactured by combining
various component parts such as wires, terminals, connectors and a protector. As shown in Figure 1, the wire
weight accounts to about 60 - 70% of the gross weight ingeneral.
The aluminum wire harness significantly reduces weightby substituting its wire from the existing copper wire to
the aluminum wire.
Clamp Fuse
2%0% Others
Tape
5%
Tube 2%
4%
Grommet2%
Terminal
4%
Protector
4%
Connector
Wire
9%
64%

3.

PROPERTIES

To adopt an aluminum wire, developments of both thewire itself and its peripheral technology are important. We
will explain the three prime properties in these technologies: “the alloy material used for the wire conductor”,“aluminum wire connection technology” and “the countermeasures for galvanic corrosion in the terminal part”.
3.1 Alloy Material Used for the Wire Conductor
We have developed a 1000 system aluminum by slightly
adding Fe, Cu and Mg to aluminum. This alloy material isa Furukawa Electric’s own alloy called MS2AL that fulfills
the five capabilities required for the wire harness in agood balance: conductivity rate, jointing property,
mechanical strength, flexibility and bending ability.
3.2 Aluminum Wire Connection Technology
To ensure the stable performance of aluminum wire electrical connection, we have developed a terminal for small
size aluminum wires that have equal to or less than 2.5 sq
of cross sectional area. Aluminum wires have strongoxide films on its surfaces and the following issues areimportant for an excellent electrical connection. They are
the dent made to the wire barrel by crimping the terminal,
the wire elongation caused by the strong compression
and the wire penetration into grooves formed at the wire
connection part, called serration, of the terminal.
The terminal for the aluminum wire is designed toremove the oxide film effectively. The wire barrel deployment length is optimized for wire diameter and the terminal is shaped to have approximately 60 % of wire compression ratio, furthermore edge part is increased bychanging the serration shape.
This terminal for aluminum wires makes the electricalperformance and the mechanical strength compatible asshown in Figure 2, and guarantees an excellent connection performance, which could not be obtained with traditional terminals.

R/B
4%

Figure 1

Weight ratio of wire harness per component part.

Furukawa Review, No. 41

20126

Aluminum Wire Harness

0.7

0.8

0.9

11.1

Strength at pressing part

1.2

Crimp height C/H [mm]

10090
80
7060
50
4030
20
100
1.3

10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

0.7

0.8

0.9

1.0

1.1

1.2

Crimp height C/H [mm]1009080
7060
50
40
30
20
1001.3Dropping method

Molding method

Strength of pressing part [N]Resistance at pressing part after duration
Strength of pressing part [N]

10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.00.0Resistance value at pressing part [mΩ]Resistance value at pressing part [mΩ]Initial resistance at pressing part

Resistance and strength capability of the terminal exclusive toaluminum wires (left ﬁgure) and the conventional terminal (right ﬁgure)(In this example, resistance ＜1.0mΩ and strength＞70N are required.)
The terminal exclusive to aluminum wires has wide acceptable ranges of C/H (arrow rangein the ﬁgures) and it can achieve electrical and mechanical capability simultaneously.

Figure 2

Connecting property of the terminal foraluminum wire.
Figure 4

Because of the oxide film of the aluminum wire, an
unstable electrical connection was the problem in case oflarge size cables with large number of strands. Therefore,
we decided to adopt the pre-processing for wires larger
than 2.5 sq to connect the tips of wires with an ultrasonicsolder or an ultrasonic welding shown in Figure 3. By
crimping the welded wires, even large size wires can beelectrically connected effectively.

Figure 3

3.3

Ultrasonic soldered aluminum wire and crimping.

Countermeasures for Galvanic Corrosion in theTerminal Part
Terminals for the terminal part of a wire harness generally
use brass or copper alloys. This raises a concern that galvanic corrosion occurs in the connection area of the aluminum wire and the terminal depending on the externalenvironment.
In an automobile environment installation, the aluminum wire, which is adopted to the part which has a galvanic corrosion concern, needs an anti-corrosion treatment in the terminal part. For the anti-corrosion method,
we have developed an environmental deprivation method
which blocks the contact interface of the aluminum conductor and the copper terminal from outside using a resinmaterial.
We have consolidated two kinds of anti-corrosion treatments based on the specs of our automaker customer.
Figure 4 illustrates both, the molding method and thedropping method.

4.

Anti-corrosion method.

LINEUP AND EFFECT OF WEIGHTREDUCTION

Currently, we have prepared the products of aluminum
wires in sizes greater or equal to 0.75 sq as shown in
Table 1. Their conductor standard is based on the ISOstandards. A halogen-free material is used for the insulator. The allowable temperature limit is 80℃.
When substituting an aluminum wire to a copper wire,choosing the aluminum wire the next size larger than thecopper wire is common because of the difference of electrical conductivity between copper and aluminum.
Therefore, copper wires of greater or equal to 0.5 sq are
the target wires to be substitute with the aluminum wires.
When a copper wire is substituted with the aluminum
wire, about a reduction of 30 - 40% of the wire weight(depending on the size of the wire) can be achieved.
Also, as a whole wire harness, about a reduction of 10 –20% of weight (depending on the application or the extentof the implementation) can be achieved.
Table 1

Replacement of aluminum wire with copper wire.
Copper wire

Wire
type

Aluminum wire

NominalMassdiameter (standard) g/m

Wire
type

NominalMassdiameter (standard) g/m

Weightsaving
effect %

CHFUS

0.5

5.5

ALUS

0.75

3.1

▲43.6

CHFUS

0.75

7.7

ALUS

1.25

5.0

▲35.1

CHFUS

1.25

12.7ALSS2f

9.1

▲28.3

ALSS

2.5 f

11.7

▲45.6

ALSS3f

13.6

▲36.7

HFSS

5.

2f

21.5

FUTURE PLAN

We have completed the necessary technology development to commercialize the aluminum wire harness. In thefuture, increase of the percentage of the aluminum wires’
implementation will be an important theme.
To raise the percentage of the aluminum wires’ implementation, “reducing the cost of anti-corrosion” and“expanding the types of wires” (Figure 5) are necessary.
Because an anti-corrosion treatment is unnecessary forcopper wires, its cost becomes a net increase by imple-Furukawa Review, No. 41

20127

Aluminum Wire Harness

menting the aluminum wire. Keeping the net increase as
small as possible accelerates the substitution to the aluminum wire.
Also, the current lineup only includes the general wires
which are resistant at 80℃. Therefore, their adoption to
the parts which require heat resistance and anti-bending
ability is difficult. By expanding the types of wires such asa heat resistance wire, the implementation rate of the aluminum wires is expected to increase.
■Required kinds of wires per harness partENGINE

INST

INST
○
FLOOR
DOOR
○
E/R○ ○○ENGINE
◎ ○ ○
◎
HEV○
○

FLOOR

120℃ heat resistance
Normal aluminum wire
100%
90%
80%

0%
31%

Micro wire

Shielded wire（thick wire）
Shielded wire （thin( wire）
150℃ heat resistance
120℃ heat resistance
100℃ heat resistanceVibration resistanceAnti-bending ability

E/R

◎
○○○
○

Anti-bending ability
100℃ heat resistance
Copper wire (less than or equal to 0.35)

0%
5%

0%
5%

31%

31%

70%

0%
8%
5%
31%

60%

6%
8%
5%
31%

50%
40%
30%

69%

64%

64%

56%20%

50%

10%
0%

Presentstate
Normal wire

Figure 5Antibending
Normal wire
Anti-bending

ShieldNormal wire
Anti-bending
Shield

100℃
120℃
heat resistance heat resistance
Normal wire Normal wire
Anti-bending Anti-bending
ShieldShield100℃ heat resistance 100℃ heat resistance
120℃ heat resistancePrediction of aluminum wire adoption rate.

We are planning to continue the development of the technology with a focus on the two development themes
above to achieve a weight reduction impact by using thealuminum wires to the maximum extent.
For more information, please contact:
Technological Element Group
Component Develop. UNIT
Engineering & Development DEPT.
Engineering Division
Furukawa Automotive systems INC.
TEL: +81-749-38-4150 FAX: +81-749-38-4160

Furukawa Review, No. 41

20128