JP4166147B2 - Method for producing copper alloy plate for high-strength electrical and electronic parts - Google Patents

Description

  The present invention relates to a method for producing a copper alloy plate for electric and electronic parts that is used as a terminal, a connector, a wire harness, a terminal, a relay, a switch, a lead frame, a spring material, and the like and has high strength and excellent spring characteristics.

Conventionally, high-strength copper alloys such as Be copper and phosphor bronze (PBS) have been used for the above applications.
Be Copper (CDA17410: Cu-0.3Be) tensile strength: 800 N / mm ^2, a spring limit: 700 N / mm ^2, in conductivity 40% IACS about, since the excellent bendability, for electrical and electronic components It is used as a high-grade spring material. However, this field has expanded rapidly due to the recent popularization of mobile phones and personal computers, but from the environmental problems of Be (Be is easy to oxidize and the generated oxide is harmful to the human body), melt casting, heat treatment, etc. The manufacturing process of this type requires careful attention, and in particular, the amount of production is limited due to the need for special equipment for melting casting. But it is expensive. Phosphor bronze, on the other hand, has a low electrical conductivity, so it cannot cope with downsizing, and because of its large anisotropy, it is difficult to mold, and because it has poor stress relaxation properties, it cannot secure the holding force of the spring during heat generation. Problems have arisen.

  In order to meet these needs, (1) Cu-10% Sn, (2) Cu-Ni-Sn-Zn (see Patent Document 1 below) and the like have been proposed. However, although (1) has the same strength as Be copper, it is inferior in bending workability, has a large anisotropy, and is difficult to form by bending. (2) is Ni: 0.1% or more and less than 0.5%, Sn: more than 1.0% and less than 2.5%, Zn: more than 1.0% and not more than 15%, P: 0.00. One or both of 0001% or more and less than 0.05% and Si: 0.0001% or more and 0.05% or less are contained. If necessary, Ti: 0.0001% or more and 0.2% or less, Mg0 0.0001% or more and 0.2% or less, Ag: 0.0001% or more and 0.2% or less, and Fe0.0001% or more and 0.6% or less, including 0.0001 to 1% in total or necessary In addition, the total amount of one or more of Ca, Mn, Be, Al, V, Cr, Co, Zr, Nb, Mo, In, Pb, Hf, Ta, B is 1% or less. It is a copper alloy consisting of the remaining impurities and Cu. When compared with Be copper, the tensile strength and spring limit Is still at a low level.

JP 2000-80427 A

  An object of the present invention is to obtain a tensile strength and a spring limit value close to those of a Be copper plate for the Cu—Ni—Sn—Zn based copper alloy plate.

  In the present invention, a copper alloy having substantially the same composition as that of the copper alloy plate described in Patent Document 1 is obtained by improving its production method, and Ni: 0.1% or more. Less than 0%, Sn: more than 0.5% and less than 4.0%, Zn: more than 1.0% and not more than 20%, P, Si, Ti, Mg, Ag, Fe, Ca as required One, or two or more of Mn, Be, Al, V, Cr, Co, Zr, Nb, Mo, In, Pb, Hf, Ta, and B: 1% or less in total, and remaining impurities and Cu An intermediate annealing with recrystallization performed in the middle of the cold rolling process and a stabilizing annealing after the final cold rolling are applied to the copper alloy obtained under the temperature range of 200 to 850 ° C. for 5 seconds to 1 minute. And the processing rate of the said last cold rolling shall be 72% or more.

According to the present invention, it is possible to produce a copper alloy plate having a tensile strength of 700 N / mm ² or more, a spring limit value of 550 N / mm ² or more, and excellent bending workability. In addition, the copper alloy plate produced according to the present invention has an electrical conductivity of 20% IACS or more, and is excellent in stress relaxation resistance, stress corrosion cracking resistance, migration resistance, solder weather resistance, and whisker resistance. Yes.

Hereinafter, the manufacturing method of the copper alloy plate for high-strength electrical and electronic parts according to the present invention will be described in detail.
First, the reason for adding each additive element (essentially the same as the copper alloy described in Patent Document 1) will be described.
(Ni)
Ni is an element that improves strength and stress relaxation resistance by co-addition with Sn. If the content is less than 0.1%, the above effect cannot be obtained. If the content is 1.0% or more, the conductivity and solder weather resistance are lowered, which is disadvantageous in terms of cost. Therefore, the addition amount of Ni is set to 0.1% or more and less than 1.0%. Desirably, it is 0.1% or more and less than 0.5%.

(Sn)
Sn has an effect on improving mechanical properties, particularly on the balance between yield strength and elongation, and hence on the formability, spring limit value, and stress relaxation resistance, but the effect cannot be obtained at 0.5% or less. If it is contained in an amount of 4.0% or more, the conductivity is lowered, which is not economical. Therefore, the amount of Sn added is more than 0.5% and less than 4.0%. Desirably, it is more than 1.0% and less than 2.5%.

(Zn)
Zn is an essential element that contributes to strength improvement by solid solution and suppresses solder weather resistance, adhesion of various platings, and further suppresses whisker and migration. When the Zn content is 1.0% by weight or less, the solder weather resistance, the adhesion of various platings, and the effect of suppressing whisker and migration are small. When the Zn content exceeds 20%, the conductivity is low. The stress relaxation characteristics are deteriorated, and stress corrosion cracking is more likely to occur. Therefore, the Zn content is more than 1.0% and 20% or less. Desirably, it exceeds 1.0% and is 15% or less.

(Other elements)
P, Si, Ti, Mg, Ag, Fe, Ca, Mn, Be, Al, V, Cr, Co, Zr, Nb, Mo, In, Pb, Hf, Ta, and B are added as necessary. Or it is an element contained as an impurity, The 1 type (s) or 2 or more types are controlled by 1% or less in total amount.
Among these, P is an element that contributes to improving the soundness of the ingot (deoxidation, hot water flow, etc.). For that purpose, the content (residual amount) is effective at 0.0001% or more. On the other hand, if the amount is too large, the mechanical properties, bending workability, or plating properties of the product are hindered.
When Si is added at the time of melt casting, it has an effect as a deoxidizing material, and is added in place of or together with P. For that purpose, the content (residual amount) is preferably 0.0001% or more. On the other hand, if too much Si remains in the matrix as a solid solution, it causes whitening or peeling of the solder and Sn plating, and the electrical conductivity also decreases, so it is 0.05% or less, preferably 0.01% or less. It is desirable to regulate.

Ti, Mg, Fe, and Ag have an effect of improving stress relaxation resistance by addition of a small amount, but any of them is ineffective at less than 0.0001%, and if contained in a total amount exceeding 1%, conductivity, solder The weather resistance and bending workability are reduced. Therefore, when added, the total amount is 0.0001% or more and 1% or less. Desirably, Ti: 0.0001% to 0.2%, Mg: 0.0001% to 0.2%, Ag: 0.0001% to 0.2%, Fe 0.0001% to 0.6 % Or less. These elements can be appropriately added to a copper alloy composed of Ni, Sn, Zn, and Cu, or a copper alloy containing either or both of Si and P.
Ca, Mn, Be, Al, V, Cr, Co, Zr, Nb, Mo, In, Pb, Hf, Ta, and B have a function of improving the stress relaxation resistance. If any element is less than 1%, Ni and Sn, which are the main components of this alloy, do not form intermetallic compounds, but these have low solid solubility limit around room temperature or strong affinity with oxygen. When one or more of these elements are contained in a total amount exceeding 1%, a coarse oxide is formed during melt casting, hot rolling, or thermomechanical treatment, or a coarse crystallized product. Occurs, and the plating property and bending workability are deteriorated. In addition, the conductivity is lowered. Therefore, the addition amount of one or more of these selective elements is 1% or less in total. These elements are (1) a copper alloy composed of Ni, Sn, Zn and Cu, (2) a copper alloy further containing one or both of Si and P, and (3) the element of (1) or (2) In addition, it can be added as appropriate to a copper alloy containing one or more of Ti, Mg, Fe, and Ag.

The manufacturing method of the present invention is a method in which the copper alloy cast material having the above composition is subjected to hot rolling as necessary, followed by cold rolling with intermediate annealing in the middle, followed by stabilization annealing. The intermediate annealing and the stabilization annealing are performed in the temperature range of 200 to 850 ° C. for 5 seconds or more and 1 minute or less, and the processing rate of the final cold rolling before the stabilization annealing is set to 72% or more. If the cast material is thick (for example, 50 mm or more in thickness), homogenization is performed as necessary, then hot rolling, and thin (for example, less than 50 mm) cast material produced by horizontal continuous casting is homogenized. Only the treatment can be performed and hot rolling can be omitted.
The intermediate annealing is for recrystallizing the copper alloy sheet during the cold rolling, and is performed at a temperature in the range of 250 to 850 ° C., more preferably 550 to 650 ° C., for a heating and holding time of 5 seconds or more and 1 minute or less. Do it. This can be done through a continuous furnace. A complete recrystallized structure cannot be obtained at a temperature lower or shorter than this range, thereby reducing the bending workability and stress relaxation resistance of the product. At higher temperatures or longer than this range, the grains and precipitates are coarse. As a result, the tensile strength and spring limit value of the product are lowered, and the bending workability and the stress relaxation resistance are also lowered.

The final cold rolling needs to be performed at a processing rate of 72% or more in order to accumulate a large amount of dislocations and improve the tensile strength and spring limit value of the product. Thus, it is possible to significantly improve the tensile product strength and spring limit value (respectively, 700 N / mm ² or more, 550 N / mm ² or higher), moreover, is not possible to almost deteriorating other characteristics. The upper limit of the working ratio is not particularly limited, about 90% is realistic prospect. In order to produce a higher strength product, the processing rate is desirably 78% or more. The upper limit is desirably 87% or less.
Stabilization annealing is to appropriately release the dislocations introduced in the final cold rolling without causing recrystallization, and to improve the stress relaxation characteristics and spring limit values of the product. It is performed at a temperature within a temperature range of 300 ° C., more preferably 300 to 450 ° C., for a heating and holding time of 5 seconds or more and 1 minute or less. This can be done through a continuous furnace. Dislocations will not be released properly at temperatures lower or shorter than this range, and this will not improve the spring limit value, stress relaxation resistance, and bending workability of the product, and at temperatures higher or longer than this range. The tensile strength and spring limit value of the product will decrease, and the stress relaxation resistance will also decrease.

  The form of the crystal grains of the copper alloy sheet obtained by this manufacturing method is such that the average crystal grain size (a) measured in the sheet width direction on the rolled surface is 1 to 20 μm, and the average crystal grain measured in the direction parallel to the rolling direction. It is desirable that the diameter (b) is 2 to 200 μm and the aspect ratio (b / a) is 2 or more and 10 or less. This crystal grain form can be obtained by setting the grain size of the recrystallized grains (substantially equiaxed crystals) after the intermediate annealing within the range of 1 to 20 μm, which is achieved by the intermediate annealing conditions. The recrystallized grains are stretched in the rolling direction by final cold rolling to form a rugby ball shape having the above aspect ratio. As for the crystal grain of the copper alloy plate of a product, a is 3-10 micrometers, b is 6-100 micrometers, and b / a is similarly 2-10. In this case, the grain size of the recrystallized grains after the intermediate annealing may be in the range of 3 to 10 μm.

Ni: 0.35%, Sn 2.31%, Zn 14.0%, Ca, Mn, Be, and Al containing 0.0001% each of the remaining Cu alloy, with a kryptor furnace under charcoal coating in the atmosphere An ingot was obtained by melting. Next, this ingot was hot-rolled and finished to a thickness of 15 mm, and further cold rolling, intermediate annealing and stabilization annealing were combined to produce a 0.25 mm-thick copper alloy plate. Table 1 shows the cold-rolled material thickness before intermediate annealing, intermediate annealing conditions, cold-rolled material thickness and processing rate after final cold rolling, and stabilization annealing conditions.
Then, about this copper alloy board, the crystal grain size was measured in the following way, and various characteristics were measured in the said way. The results are shown in Table 2.
(Crystal grain size) The rolling surface was measured by a cutting method defined in JISH0501 in the plate width direction and the direction parallel to the rolling direction. In addition, No. which was not recrystallized by intermediate annealing. Measurement was not possible for 3, 5, and 6.

(Tensile strength) A JIS No. 5 test piece was sampled from the copper alloy plate so that the longitudinal direction was the rolling direction, and measured according to JISZ2241.
(Spring limit value) Based on JISH3130, the amount of permanent deflection at room temperature was measured by a moment type test, and Kb0.1 was calculated. The longitudinal direction of the test piece was parallel to the rolling direction.
(Conductivity) Measured based on JISH0505.
(90 ° bending workability) A specimen of 10 mm width and 35 mm length was taken from a copper alloy plate so that the longitudinal direction was the plate width direction, and B-type bending treatment specified in the CESM0002 metal material W bending test The test material was sandwiched between tools, and W bending was performed at a load of 1 t at R / t = 2 using a universal testing machine RH-30 manufactured by Shimadzu Corporation, and the presence or absence of cracks in the bent portion was determined.

(Stress relaxation rate)
As shown in FIGS. 1 and 2, a test piece 1 having a width of 10 mm is subjected to a bending stress of 80% of the yield strength of the test piece at a position of 80 mm (l) in the cantilever type described in EMAS-3003. After adding and holding the stress at 150 ° C. for 1000 hours with the stress applied, the stress was removed. The amount of deflection (δ) of the test piece at the added point when stress was applied and the displacement (ε1) when the stress was removed were measured, and the stress relaxation rate was measured by the following formula (n = 5 at each temperature) ).
Stress relaxation rate (%) = (ε1 / δ) × 100
The bending stress (σ) is calculated by the following formula.
σ = (3 × E × t × δ) / (2 × l ² )
However,
σ: bending stress = proof strength of test piece × 0.8
E: Young's modulus of test piece (N / mm ² )
t: Thickness of the test piece = 0.25 mm

Table 1 shows that No. manufactured under the conditions specified in the present invention. No. 1 has a higher tensile strength and spring limit value than the data of Patent Document 1, and is excellent in conductivity, bending workability and stress relaxation characteristics.
On the other hand, No. with a low processing rate of final cold rolling. 2 has a low aspect ratio and a low tensile strength and spring limit value. The intermediate annealing temperature and time are less than the standard. No. 3 is a high No. 3 in which recrystallization is not performed, bending workability and stress relaxation characteristics are inferior, and the intermediate annealing temperature and time exceed the specified values. No. 4 is No. 4 in which the crystal grains are coarsened and the aspect ratio is high, the tensile strength, the spring limit value, the bending workability and the stress relaxation property are inferior, and the intermediate annealing time is shorter than specified. No. 5 and the intermediate annealing temperature is lower than specified. In No. 6, no recrystallization was performed, bending workability and stress relaxation characteristics were inferior, and the intermediate annealing temperature was higher than specified. No. 7 has a large grain size and a high aspect ratio, is inferior in tensile strength, spring limit value, bending workability and stress relaxation characteristics, and is not subjected to stabilization annealing. 8 and No. 8 with a short stabilization annealing time. No. 9 is inferior in spring limit value, bending workability and stress relaxation characteristics, and has a stabilized annealing temperature and time exceeding the specified values. No. 10 and the stabilization annealing time is longer than specified. No. 11 was recrystallized and the crystal grains became coarse, the tensile strength, the spring limit value and the stress relaxation characteristic were inferior, and the stabilization annealing temperature was low. No. 12 is inferior in spring limit value, bending workability and stress relaxation characteristics, and has a long intermediate annealing time. No. 13 and intermediate annealing temperature and time No. In No. 14, crystal grains are coarsened, and the tensile strength, spring limit value, bending workability and stress relaxation characteristics are inferior.

It is a perspective view for demonstrating the method of evaluating a stress relaxation rate characteristic. It is the side view.

Explanation of symbols

  1 Test piece

Claims (2)

Ni: 0.1% or more and less than 1.0% (mass%, the same shall apply hereinafter), Sn: more than 0.5% and less than 4.0%, Zn: more than 1.0% and less than 15% , necessary 1 type or 2 types of P, Si, Ti, Mg, Ag, Fe, Ca, Mn, Be, Al, V, Cr, Co, Zr, Nb, Mo, In, Pb, Hf, Ta, B Above: The copper alloy cast material containing 1% or less in total and comprising the remaining impurities and Cu is hot-rolled as necessary, and then cold-rolled to obtain a copper alloy plate for electric and electronic parts. In manufacturing, intermediate annealing with recrystallization performed in the middle of the cold rolling process is performed within a temperature range of 550 to 650 ° C. for 5 seconds or more and 1 minute or less, and the final cold rolling processing rate is 72% or more. and then, subjected to stabilization annealing after the final cold rolling in the temperature range of 300 to 450 ° C. for 5 seconds or more 1 minute following conditions High intensity electrical method for manufacturing an electronic component for a copper alloy sheet, wherein the door. The method for producing a copper alloy plate for high-strength electrical and electronic parts according to claim 1, wherein the average grain size of the recrystallized grains after the intermediate annealing is set to 20 µm or less.

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