Copper alloy

Abstract

A copper alloy, containing: Ni and / or Si, and at least one or more of B, Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Be, with a balance being Cu and inevitable impurities; the copper alloy having a precipitate X composed of Ni and Si; and a precipitate Y composed of Ni and / or Si, and at least one or more of B, Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Be, in which a grain diameter of the precipitate Y is 0.01 to 2 μm.

Description

TECHNICAL FIELD [0001] The present invention relates to a copper alloy applicable as materials for electric and electronic instruments. BACKGROUND ART [0002] Heretofore, generally, in addition to iron-based materials, copper-based materials, such as phosphor bronze, red brass, and brass, which are excellent in electrical conductivity and thermal conductivity, have been used widely as materials for electric and electronic instruments (electrical and electronic machinery and tools). [0003] Recently, demands for miniaturization, weight saving, and associated high-density packaging of parts of electric and electronic instruments have increased, and various characteristics of higher levels are required for the copper-based materials applied thereto. Examples of basic characteristics required include mechanical properties, electrical conductivity, stress relaxation resistance, bending property, and spring property. Of those, improvements in stress relaxation resistance, tensile strength, ...

AI Technical Summary

Benefits of technology

[0015] For solving the above-mentioned problems, the present invention contemplates providing a copper alloy having high bending property and excellent tensile strength, electrical conductivity and stress relaxation resistance, wherein characteristics of the copper alloy may be readily balanced depending on uses, and the copper alloy is favorable for materials of lead frames, connectors, terminals or the like of electric and electronic instruments, particularly for materials of vehicle connectors, terminals, relays and switches or the like.

[0016] The inventors of the present invention have conducted intensive studies on a copper alloy suitably used for electrical and electronic parts, and have noticed the relations between characteristics of the alloy and grain diameters of Ni—Si precipitates and other precipitates in a copper alloy structure, and between the proportions of the distribution density of the precipitates and suppression of coarsening of crystal grains. As a result, the inventors have completed, through intensive studies, the copper alloy of the present invention that is able to form a material having excellent tensile strength and being excellent in bending property, electrical conductivity, and stress relaxation resistance.

[0030] The copper alloy of the present invention compatibly has a tensile strength and a bending property (R / t) at high levels, without impairing electrical conductivity, while stress relaxation resistance that may largely affect reliability of connectors and terminals is further improved. The copper alloy of the present invention is excellent in bending property and stress relaxation resistance, as compared with conventional copper alloys having the same level of tensile strength. The copper alloy of the present invention is a copper alloy favorable for use in electric and electronic instruments that are required for higher characteristics upon miniaturization. In addition to the above, the copper alloy of the present invention is excellent in other properties such as spring property.

Problems solved by technology

Accordingly, conventional copper alloys are not always durable to long term uses due to increased stress loaded on the material and increased temperatures of working environments.

The required characteristics have reached a level that cannot be satisfied with conventional commercially available, mass-produced alloys, such as phosphor bronze, red brass, and brass.

The method can provide high-strength materials by employing a large cold-working ratio, but employment of a large cold-working ratio (generally 50% or more) is known to conspicuously degrade bending property of the resultant alloy material.

However, the precipitation-type alloy has such problems that the crystal grain size increases to cause giant crystal grains upon the solution treatment, and that the crystal grain size upon the solution treatment remains unchanged and becomes the crystal grain size of a product since the aging treatment generally does not involve recrystallization.

An increased amount of Ni or Si to be added requires a solution treatment at a higher temperature, and it results in that the crystal grain size tends to increase to cause giant crystal grains, through a heat treatment in a short period of time.

The resultant giant crystal grains occurred in this way cause problems of conspicuous deterioration in bending property.

However, the resultant alloy has a tensile strength of about 640 MPa at most, which is not sufficient for satisfying the recent demands for high strength through miniaturization of parts.

Addition of Si to the copper alloy decreases the amount of the Ni—P precipitate, to thereby reduce the mechanical strength and electrical conductivity.

Further, excess Si and P cause problems of occurrence of crack upon hot working.