JPH06179932A - Copper alloy for conductive spring - Google Patents

Abstract

PURPOSE:To obtain a copper alloy for conductive spring used for terminal, connector, relay, switch, etc. CONSTITUTION:The alloy has a composition consisting of 15-43% Zn, 0.01-0.3% Mg, <=0.0015% S, <=0.0015% O, and the balance Cu or further containing, as accessory components, 0.005-2.0% of one or >=2 elements among Sn, P, Ni, Cr, Co, Al, Mn, Fe, Si, Ti, Zr, In, and B and further containing, besides the above, 0.01-15% Zn. By this method, the copper alloy having high strength and high electric conductivity and excellent in stress relaxation property, thermal peeling resistance of plating, silver plating suitability, and migration resistance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy for conductive springs used in terminals, connectors, relays, switches and the like.

[0002]

2. Description of the Related Art Conventionally, brass has been widely used as one of these spring copper alloys.

[0003]

In recent years, due to the miniaturization of equipment and parts, materials having high strength and spring characteristics have been demanded, and particularly from the viewpoint of long-term reliability of spring characteristics, materials having good stress relaxation characteristics. Is required. Further, in order to improve the stress relaxation characteristic, it is necessary to prevent the temperature rise of the parts during use as much as possible, and therefore, a material having a good heat dissipation property, that is, a high electric conductivity is required.

Further, there is a demand for a highly reliable material which has good heat-resistant peeling property of Sn plating and solder plating and which does not cause a migration phenomenon in the presence of water.

In response to these required characteristics, it has been desired that brass used conventionally has long-term reliability of spring characteristics, that is, improvement of stress relaxation characteristics. Then, it was found that the stress relaxation characteristic is improved by adding Mg.

[0006] However, it has been known that the heat-resistant peeling property of the plating is remarkably deteriorated by adding Mg to this alloy, and an improvement has been demanded.

[0007]

In view of such a situation, Cu
As a result of research on -Zn-Mg-based alloys, an alloy having good properties as a spring material has been obtained.

That is, according to the present invention, Zn: 15-43
%, Mg: 0.01 to 0.3%, S: 0.0015% or less, O: 0.0015% or less, and a copper alloy consisting of the balance Cu or P, Sn, Ni, Cr, Co, A as described above.
1 of l, Mn, Fe, Si, Ti, Zr, In and B
It is a copper alloy conductive spring alloy containing 0.005 to 2.0% of one kind or two or more kinds.

The reasons for limiting the components of the alloy of the present invention are shown below.

Zn is added in order to reduce the cost and improve the mechanical strength and the migration resistance, and the reason for setting its content to 15 to 43% is that if the content is less than 15%, the strength is insufficient and if 43% is required. If added over, β phase will precipitate,
This is because the corrosion resistance and cold workability deteriorate.

The reason for setting the Mg content to 0.01 to 0.3% is that Mg improves the stress relaxation characteristics but deteriorates the heat-resistant peeling property of the plating. This is because even if O is specified, the stress relaxation characteristics cannot be improved, and if it exceeds 0.3%, the heat-resistant peeling property of the plating decreases.

The reason why the S content is 0.0015% or less is that the S content should be very low in order to lower the Mg content and improve the heat-resistant peeling property of the plating while improving the stress relaxation characteristics. This is because it was found that when S exceeds 0.0015%, a large amount of Mg becomes a sulfide and is dispersed in the material, and the stress relaxation characteristics are not improved. This is because, even if the Mg content is low, the heat-resistant peeling property of the plating deteriorates, and when the plated product is heated, defects such as swelling and blistering will occur.

The reason why the O content is 0.0015% or less is that not only the stress relaxation characteristics are not improved by Mg as an oxide, but also the heat-resistant peeling property of the plating is deteriorated, and the plated product is heated. This is because defects such as blister occur.

That is, the contents of S and O are both 0.0
By setting the content to 015% or less, the stress relaxation property can be improved even if the Mg content is lowered, and the heat peeling resistance of the plating can be improved by lowering the Mg content.

Further, it has been found that the regulation of the contents of S and O is a key point in order to prevent the heat-resistant peeling property of the plating and the stains and blisters of the plating even with a small amount of Mg.

The content of P, B and other subcomponents is 0.00
The reason for setting it to 5 to 2.0% is that the addition of a subcomponent improves the strength, but if it is less than 0.005%, it has no effect, and
This is because if it exceeds%, the workability is lowered and the conductivity is remarkably lowered.

[0017]

EXAMPLES Next, examples and comparative examples will be described.

Table 1 shows the composition of the copper alloys of the tested examples, and Table 2 shows the composition of the tested copper alloys of the comparative example. The copper alloys with these compositions are melt-cast in the atmosphere,
An ingot having a size of mmt × 60 mmw × 120 mml was obtained. These ingots were chamfered on one side by 3 mm to mechanically remove surface defects, then heated at a temperature of 750 to 800 ° C. for 2 hours and then hot rolled to a thickness of 6 mmt. After pickling to remove surface scale, cold rolling was performed to a thickness of 0.5 mmt. After that, annealing was performed at 500 ° C. for a predetermined time. The grain size after this annealing was adjusted to 10 μm. Then, after finishing cold rolling to 0.3 mmt, the surface was finally ground with # 1200 emery paper to remove surface defects such as scales and the like, to give a test material.

[0019]

[Table 1]

[0020]

[Table 2]

About the test materials, tensile strength, elongation, conductivity,
Stress relaxation characteristics, heat resistance peeling property of tin plating, silver plating property, and migration resistance were tested. JIS tensile strength and elongation
A 13B tensile test piece was used to perform a tensile test for measurement. The electrical conductivity was converted into electrical conductivity by measuring the electrical resistance at 20 ° C. by a four-terminal method after processing a test piece of 10 mmw × 100 mml. The stress relaxation characteristic is 10mmw × 100mm as shown in Fig.1.
On a test piece with a plate thickness of 0.3 mm processed into 1
A bending stress of ₀ mm and height y ₀ = 20 mm is applied, and
After heating at 0 ° C. for 1000 hours, the permanent deformation amount (height) y shown in FIG. 2 was measured and the stress relaxation rate {[y (mm) / y
₀ (mm)] × 100 (%)} was calculated. The tin-plating heat-resistant peeling resistance is 10 mmw × 100 m when the test material is subjected to copper underlayer plating of 0.5 to 0.8 μm, electroplated with tin of 1 to 1.5 μm, and then subjected to heat reflow treatment.
After cutting into ml, heat at 150 ° C for a predetermined time (every 100 hours), bend 90 ° on one side once with a bending radius of 0.3 mm (= plate thickness) once, and bend the front and back sides with a field of view of 20 times. The vicinity was observed to confirm the presence or absence of peeling of the plating. The silver plating property is 1μ with silver flash plating on the test material with copper flash plating as the base.
1470 after heating at 450 ° C for 2 minutes
The number of blisters was measured in an area of mm ² (7 mm □ × 30 pieces). Migration resistance is 10 mm for the test material
It was processed into w × 100 ml, set as a set of two pieces as shown in FIG. 3, and immersed in tap water (300 ml) as shown in FIG. Next, a DC voltage of 14 V was applied between these two test materials, and the change in current value with respect to the elapsed time was measured. A representative example of this result is shown in FIG. The migration resistance was evaluated by the time until the current value reached 1.0 A (arrow in FIG. 5).

Table 3 shows the results of these evaluations.

[0023]

[Table 3] From this table, it is understood that the alloy of the present invention has good strength and conductivity, good stress relaxation property, and very good surface quality such as heat resistance peeling property of tin plating and silver plating property.

Contrary to these, No.
Since No. 19 has a low Zn content, it has low strength and poor migration resistance. On the other hand, No. Since No. 20 has a high Zn content, it has low elongation and poor cold workability. No. No. 21 has a poor stress relaxation characteristic because it contains no Mg amount. No. No. 22 has a high amount of Mg and is inferior in heat resistance peeling property of tin plating.

No. 23, No. Since No. 24 has a large amount of O and S, the stress relaxation property, the heat resistance peeling property of tin plating, and the silver plating property are poor.

As described above, the alloy of the present invention is Cu-Z.
The O and S contents of the n-Mg-based alloy are specified, and Sn, P and
Ni, Cr, Co, Al, Mn, Fe, Si, Ti, Z
By adding one or more of r, In, and B, high strength, high conductivity, and good stress relaxation characteristics,
The heat-resistant peeling property of the plating, the silver plating property, and the migration resistance are also good.

[0027]

INDUSTRIAL APPLICABILITY The alloy of the present invention is a copper alloy having high strength, high conductivity, stress relaxation characteristics, heat-resistant peeling property for plating, silver plating property, and migration resistance, and is widely used in terminals, connectors, relays, switches, etc. It is a copper alloy that should be used in the field of parts.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a stress relaxation characteristic test method.

FIG. 2 is an explanatory diagram of a permanent deformation amount in a stress relaxation characteristic test.

FIG. 3 is an explanatory diagram of a test material for a migration resistance test.

FIG. 4 is an explanatory diagram of a migration resistance test.

FIG. 5 is a graph showing changes in current value with respect to elapsed time in a migration resistance test.

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[Procedure amendment]

[Submission date] August 15, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

Conventionally, as one of these spring copper alloy had brass widely used.

Claims (2)

[Claims] 1. Zn: 15 to 43% (weight%, the same hereinafter), Mg: 0.01 to 0.3%, S: 0.0015%
Hereinafter, O: 0.0015% or less and the balance being Cu, a copper alloy for conductive springs. 2. Zn: 15-43%, Mg: 0.01-
0.3%, S: 0.0015% or less, O: 0.0015
% Or less, and Sn, P, Ni, Cr, C as sub-components
O, Al, Mn, Fe, Si, Ti, Zr, In, and 0.005 to 2.0% of one or more kinds of B are contained,
A copper alloy for conductive springs, characterized in that the balance is Cu.