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The Copper Alloy Strip EFCUBE-820 for Connectors

1.

INTRODUCTION

ItemConnectors used between circuit boards and between
modules have been becoming smaller and highly-functional because the technological development has been
taking place in response to the high functionalization andthe reduction in size and weight of electronic equipment.
High-strength copper alloys used for small-sized electriccontact materials in small-sized connectors require a better performance to bending to meet the space saving, theresource saving and the productivity improvement, asshown in Figure 1. Although there is a trade-off between aperformance to bending and to strength, these characteristics have been considerably improved by controlling themicrostructures of Cu-Ni-Si alloys (Colson alloys). We
developed a new alloy EFCUBE-820 (UNS: C64775) withthis technology.

Evaluation method
Conform to JIS Z2244

Electric conductivity

Four-terminal method at 20°C 38%IACS

Performance tobending

90° W-type bend
(Minimum bendable radius)
Conform to JIS Z2248

Stress relaxation
rate

Conform to JCBA T309(2004)8%
Keep at 150°C for 1000 hours

Figure 12.

95GPa
105Low elasticity(Young’s modulus)

710
115

125

50%IACS

Young’s modulus

Figure 2680
3t

4t2t

1t0t

Performance
to bending

40
30
20
100%

GeneralCu-Ni-Si alloyHeat-resistant reliability(Stress relaxation rate)

The characteristics of EFCUBE-820 alloy andother copper alloys.

The background of the development.

Evaluation method

Tensile strength
Elongation

30

Electric conductivity

The basic characteristics of the EFCUBE-820(Representative value, Temper-H) and evaluation
methods.

0.2% yield strength

135
10Speeding up ofpress work

The newly developed alloy strip EFCUBE-820 (Temper-H)
was evaluated for the characteristics shown in Table 1,
and the results were compared with the phosphor bronze
alloy (JIS-C5210) and a general Cu-Ni-Si alloy as shownin Figure 2. The representative values of the new alloy
EFCUBE-820’s (Temper-H) basic characteristics areshown in right-hand columns of Table 1.

Item

EFCUBE-820 alloy

740

40

CHARACTERISTICS

Table 1Minimum bendable
radius
R=0770High strength of materials

Terminal materials require an excellent
performance to bending

800MPaPhosphor bronze alloy

Thinning of materials

Small bend radiusSevere dimensional accuracy

245

Strength (Yield stress)

20

Downsizing of terminals

Representative value

Vickers hardness (Hv)

Representative value

The EFCUBE-820 alloy showed a good performance tobending. It had the high strength that was equivalent tothat of the phosphor bronze alloy (Temper-SH-ESH). At
the same time, no crack occurred without an inner bendradius.
Moreover, 180°U-type closely-attached bend test wasperformed with respect to its performance to bending.
Figure 3 shows the results.
The phosphor bronze alloy and the general Cu-Ni-Si
copper alloy generated large cracks that cause a lowering of the contact pressure and a poor conduction. Incontrast, the EFCUBE-820 alloy had the high strength ofgreater or equal to 800 MPa in tensile strength, and also
showed a good performance to bending that had nocrack on the bent part.

800 MPa
Tensile test
Conform to JIS Z2201, 2241

770 MPa
7%
110 GPa

Furukawa Review, No. 392011

12

The Copper Alloy Strip EFCUBE-820 for Connectors

The EFCUBE-820 The phosphor Cu-Ni-Si : The generalalloybronze alloyCu-Ni-Si alloy

Material
Tensile strength/MPaObservation part804

788

733

GoodCrackCrackSurface

U-type bend

Cross section
Width: 1 mmFigure 2

180° U-type bending test.

Shown in Table 2, the EFCUBE-820’s composition is a
Cu-Ni-Si precipitation-hardened copper alloy. It gives consideration to the cost reduction of the materials because
the expensive Ni content is less than in general Cu-Ni-Si
alloys. Also, it contains no environmental pollutants. (Theslightly-added Cr is not hexavalent chromium.)
Table 2The chemical composition of the EFCUBE-820 alloy(mass%)

NiSiZnSnCrMg

2.30

0.65

0.50

0.15

0.15

0.10

The EFCUBE-820 alloy has also an excellent (or good)
performance to plating. When it was plated with Sn, nopeeling was observed in the peeling test at 160°C after
keeping it for 120 hours. When the environmental tests
such as the salt spray test or the mixed gas corrosion test
were performed on Ni-based (thickness: 1 μm) Au plating(thickness: 0.1 μm), it showed a good performance toplating without a pinhole, and corrosion did not attack thebase material. This is the effect of the control of the surface state and the inclusion, and the sub-additive element.

3.

the copper alloys even when the lengths of contact springs(L-length) become short due to the downsizing of connectors. In addition, they require a low Young’s modulus toabsorb the slight size spread caused by the press works
such as a punching and a bending when material terminals
are manufactured. That is because the size spread isprone to affect the contact pressure fluctuation of the electric contact. Also, they require a high conductivity because
the cross section of conductors per 1 pin decreases withthe multipolarization and the narrowing in pitch.
Moreover, materials require a good anti-stress relaxation because the contact pressure is lowered by thecreep phenomenon. The lowering occurs when they areused in box terminals for wire harnesses in automobiles,
and in the high temperature environment where lamps
are a typical source of heat. The high current connectors
require a high conductivity and an anti stress relaxation to
restrain Joule heat and to secure the reliability of the contact pressure.
The EFCUBE-820 alloy shows better characteristics
than existing materials in all the items in Figure 2, so itmeets the requirements above and contributes to thetechnical innovation of connectors. Figure 4 shows theexamples of the optimum applications that take advantage of the EFCUBE-820’s alloy characteristics. Also, its
high strength and its good performance to bending contribute to the thinning of the copper alloy contact materials for connectors. The natural resource saving and thecost reduction are possible by adopting it instead of existing copper alloys.

[Optimum applications of the EFCUBE-820 alloy](CT: connector)

Connectors for electric and electronic devices
CTs for boards, bat ter y CTs, CTs for flexible printed
circuits, card and media CTs, sockets for camera modules
and central processing units, jacks

APPLICATION

Table 3 shows the relation between the development trendof connectors and the required characteristics of the copper alloys that are used in electric contact materials.
Table 3The development trend of connectors and the required
characteristics of the copper alloy electric contact
materials.

The required characteristics of the copper alloy
electric contact material
The trend of connectors
High per- Low stressHighLowHighformance relaxationelectricYoung’sstrength
to bending
rate
conductivity modulus
Space saving
Downsizing
Lowering in height
Multipolarization,
narrowing in pitch
High
High currency
functionHigh reliability
Widening of
Production dimension tolerance
cost
reduction Speeding up ofpress work

Materials require a high strength and a low Young’s
modulus to have deformations within the elastic limits ofConnectors for automobiles
Female terminals for wire harnesses, various switches

High currency connectors
Springs of multi-contact CTs
Figure 44.

The optimum applications of the EFCUBE-820 alloy.

CONCLUSIONEFCUBE-820 has the tensile strength of 800 MPa andshows a good performance to bending. Also, its electric
conductivity and its heat-resistant reliability are good. It isan optimum choice as an electric contact material for various connectors.
For detailed technical data of the EFCUBE-820 alloy,
please consult the catalog on our website.
For more information, please contact
Metal Company
Tel: +81-3-3286-3850 Fax: +81-3-3286-3663

Furukawa Review, No. 39201113