JPS6160131B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a Cu-Sn-Be-based conductive spring material that has excellent conductivity and spring properties and is used as a material for electrical equipment such as connectors, switches, and relays. (Prior art) A typical conductive spring material with excellent conductivity and spring properties is a material with a content of 5.5 to 9.0% (by weight, the same applies hereinafter), which is specified as Type 2 or Type 3 in JIS.
Phosphor bronze contains Sn and 0.03 to 0.3% P, but Sn is expensive, and it has poor conductivity, bending formability, and stress for use in recent miniaturized electronic components that require high reliability. Demand for improvement is increasing due to reasons such as insufficient relaxation properties. Therefore, the present applicant first focused on the fact that P remaining in phosphor bronze lowers the conductivity, and invented a Cu-Sn-Be-based material in which deoxidation was performed with Be instead of P. We have succeeded in improving the heat workability by more than 50% compared to phosphor bronze, as well as improving hot workability. (Japanese Patent Publication No. 51-8847) (Problems to be Solved by the Invention) However, although the above-mentioned Cu-Sn-Be material has succeeded in improving conductivity and hot workability, it is difficult to maintain a stable contact pressure in the spring. The stress relaxation property, which is an indicator of whether or not the stress can be maintained, was insufficient. This stress relaxation property is determined by bending a test piece under a load such that a maximum bending stress of 40 kgf/cm ² is applied to it at 200°C.
This is evaluated by removing the load after holding for 100 hours and measuring the residual stress in the test piece, which is considered to be an important property to ensure high reliability of electronic components. Although this material is slightly superior to phosphor bronze, satisfactory values have not been obtained. Therefore, there has been a need for a conductive spring material that has excellent properties such as conductivity, bending formability, stress relaxation properties, etc., and is low cost. (Means for Solving the Problems) The present invention has been completed to solve the above-mentioned conventional problems, and has a weight ratio of 5.0 to 8.0.
% Sn, 0.002-0.2% Be, 0.1-3.0% Ni and/or 0.05-1.0% Fe, and the balance is Cu. That is, in the present invention, the deoxidizing effect of Be is superior to that of P, and the conductivity of the Cu-Sn-Be-based material is lower than that of Cu-Sn.
-Based on the conventional knowledge that it is larger than P-based phosphor bronze, we reduced the formation price by substituting a part of the expensive Sn with Ni and Fe, and also refined the structure and This material was developed based on the new knowledge that heat resistance and mechanical properties can be improved by the precipitation of It has better properties required for conductive spring materials such as workability. Next, the reason for limiting the content of each component is as follows.
If Sn is less than 5%, sufficient mechanical strength cannot be obtained, and if it exceeds 8.5%, elongation decreases and formability such as cold rollability decreases, and the range of 5.0 to 6.5% is the best. preferable. By adding either or both of them, Ni and Fe make the crystal grains finer, and also generate a second phase with Sn or alone to achieve thermal stabilization and improve the above-mentioned properties. If Ni is less than 0.1%, the grain refinement effect is insufficient and stress relaxation properties cannot be improved, and if it exceeds 3%, cold rollability and bending formability deteriorate. Similarly, if Fe is less than 0.05%, the effect of crystal refinement and improvement of stress relaxation properties is insufficient, and if it exceeds 1%, cold rollability and bending formability deteriorate. Ni is most preferably in the range of 0.4 to 2.5%, and it is preferable that Sn+Ni+Fe be 9% or less in any case of Ni alone, Fe alone, or a combination of Ni and Fe. Be, which is a deoxidizing agent, is less than 0.002% and the deoxidizing effect of the molten metal is insufficient, causing many casting defects in the material and deteriorating the rolling workability and mechanical properties.If it exceeds 0.2%, it deteriorates the conductivity and This will lead to an increase in the combined price. (Example)

[Table] Examples 1 to 6 and conventional conductive spring materials shown in Table 1 were melted and cast in a high frequency induction furnace, repeatedly annealed and cold rolled to form a plate with a thickness of 0.63 mm, and final softening annealed at 550 mm. ℃ for 2 hours, followed by 60% cold rolling, followed by low-temperature annealing at 200℃ for 2 hours, and the properties were measured. The results are shown in Table 2. In Table 2, the stress relaxation properties are expressed as the stress residual rate (%) measured by the above method, and the Young's modulus is expressed as (Kg
f/mm ² ), bending formability is (minimum radius of curvature/plate thickness), tensile strength, proof stress, spring limit value (kb value)
All are expressed in (Kgf/mm ² ). Further, 0° indicates the characteristic value in the rolling direction, 90° indicates the characteristic value in the rolling direction, and 90° indicates the characteristic value in the direction perpendicular to the rolling direction. Table 3 shows the residual hardness as an index of thermal stability, measured by microscopic Vickers hardness after holding each sample at 250 to 400°C for 1 hour, and showing the residual hardness in % compared to the hardness at room temperature. .

【table】

[Table] (Effects of the Invention) As is clear from the above description, the present invention replaces a part of Sn in the conventional Cu-Sn-Be material with Ni, Fe.
By substituting one or both of these, the structure is refined and the thermal stability is improved by precipitation of a second phase, which improves stress relaxation properties and bending formability, and further improves conductivity and This material has succeeded in reducing the fabrication price by improving various properties such as workability and at the same time reducing the Sn content, so it contributes to the development of industry as a solution to the problems of conventional conductive spring materials. There are a lot of things to do.

Claims (1)

[Claims] 1 5.0-8.5% Sn and 0.002-0.2% by weight
A conductive spring material consisting of Be, one or both of 0.1 to 3.0% Ni and 0.05 to 1.0% Fe, and the remainder Cu.