JP2002294368A - Copper alloy for terminal and connector and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-Ni-Sn-P based copper alloy which is producible by annealing heat treatment in a short time, and has excellent stress relaxation resistance without requiring high casting or heat treatment technology. SOLUTION: The copper alloy for a terminal and a connector has a composition containing, by mass, 0.8 to 1.5% Ni, 0.5 to 2.0% Sn, 0.015 to 5.0% Zn and 0.005 to 0.1% P, and the balance Cu with inevitable impurities, and the area ratio of precipitates is <=5%. Process annealing in the process of a cold rolling stage and stabilization annealing after final cold rolling are performed in the temperature range of 250 to 850 deg.C for 5 sec to 1 min in a continuous furnace, and the temperature increasing and cooling rate at this time is controlled to >=10 deg.C/sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy used for terminals, connectors, wire harnesses, terminals and the like, and more particularly to a terminal for automobiles and other consumer and industrial use which has excellent stress relaxation resistance and solder weather resistance.・ Related to copper alloy for connectors.

[0002]

2. Description of the Related Art Conventionally, so-called brass has been frequently used in the above applications in view of strength-conductivity balance and low cost. However, for example, due to the recent development of electronic control of automobile engines, the current-carrying materials for junction blocks for automobiles and their connection parts, such as relay parts, terminals and connectors, have performances that can ensure reliability under high-temperature environments such as engine rooms. It has become required.

One of the most important characteristics in the reliability under the high temperature environment is a characteristic of maintaining the contact fitting force, that is, a so-called stress relaxation characteristic. That is, when a constant displacement is given to the copper and copper alloy spring-shaped parts, for example, when the tabs of the male terminals are fitted with the spring-shaped contacts of the female terminals, these connecting parts are in the engine room. When held in such a high temperature environment, the contact fitting force is lost over time, but it is a resistance characteristic to the loss. Brass has a problem that its stress relaxation resistance is low.
Phosphor bronze is often used for terminals requiring higher strength than brass. However, phosphor bronze also has low stress relaxation resistance, and has a problem with conductivity and migration resistance.

On the other hand, Japanese Patent Application Laid-Open No. 4-154942 discloses a Cu-Ni-Sn-P alloy having excellent stress relaxation resistance. This alloy disperses the Ni-P intermetallic compound uniformly and finely, and provides strength, conductivity, spring limit,
This is a precipitation-type copper alloy that improves stress relaxation resistance and the like.
The precipitation activation energy of the Ni-Si intermetallic compound, which is a precipitate of the Cu-Ni-Si alloy known as Corson copper alloy, is relatively high at about 80 kJ / mol. The compound has a low deposition activation energy of about 25 kJ / mol. This indicates that the Ni-P intermetallic compound easily precipitates and further easily agglomerates and coarsens, and the above publication also discloses that the Ni-P compound is prevented from agglomerating and coarsening, and has a spring limit value and a stress resistance. In order to obtain properties such as relaxation properties and bending workability, the cooling start and end temperatures of hot rolling, the cooling rate, and the temperature and time of the heat treatment for 5 to 720 minutes applied during the subsequent cold rolling process The necessity of strictly controlling is described.

However, in the case of annealing, for example, the time required for inserting the product into the annealing furnace, the time required for raising the temperature, and the holding time for 5 to 720 minutes, and cooling the product to a temperature that does not cause unnecessary oxidation Such a strict control of the heat treatment process leads to inefficiency in production, and furthermore, this is reflected in the product price. On the other hand, JP-A-5-311
No. 288 discloses that the P content is 0.005 to 0.5% by weight, and further, 0.005 to 0.5% by weight of Fe, N
A method of co-adding i, Co, or the like to form an intermetallic compound with P to reduce solid solution P is disclosed. However, in such a method, depending on the processing and heat treatment conditions, there is always a possibility that a coarse metal phosphorus compound that deteriorates bending workability and plating property is formed.

[0006]

In any case, Cu
Conventionally, Ni-P compounds have been positively precipitated in order to enhance the stress relaxation resistance of -Ni-Sn-P-based alloys.
Strict heat treatment was required to uniformly and finely precipitate the Ni-P compound, and the product was expensive. Therefore, the present invention relates to a Cu-Ni-Sn-P-based alloy which is inexpensive and has excellent stress relaxation resistance, which does not require advanced casting or heat treatment technology and can be produced by an extremely short annealing heat treatment. The purpose is to obtain.

[0007]

Means for Solving the Problems The present inventor has studied the precipitation of a Ni-P compound in a Cu-Ni-Sn-P-based alloy in which a Ni-P compound was conventionally positively precipitated as a precipitation-type copper alloy. The above object was achieved by suppressing as much as possible and treating it as a solid solution type copper alloy. That is, the copper alloy for a terminal / connector according to the present invention is Ni:
0.8 to 1.5% by mass, Sn: 0.5 to 2.0% by mass,
Zn: 0.015% to 5.0% by mass or less, P: 0.00
5% to 0.1% by mass, the balance being Cu and inevitable impurities, and the area ratio of precipitates is 5% or less.

[0008] The above-mentioned copper alloy further contains Mg;
To 0.2% by mass and Fe: 0.001 to 0.1% by mass, or both. Further, it is desirable that the O content be 50 ppm or less and the H content be 2 ppm or less. And the said copper alloy may be Ag, Ti, Si, Ca, Mn, Be, Al,
V, Cr, Co, Zr, Nb, Mo, In, Pb, H
f, Ta, B, one or more of
０．０0.03%, and 0.0005 to 0.3% in total.

The above-mentioned copper alloy for terminals and connectors is hot-rolled, if necessary, then cold-rolled, annealed at least once during the cold-rolling and recrystallized, and more stable after the final cold-rolling. Although it is manufactured by annealing, in order to obtain excellent stress relaxation resistance, it is necessary that the area ratio of undissolved matters such as precipitates is 5% or less after stabilized annealing.
Alternatively, the conductivity needs to be 90% or less of the maximum value of the conductivity obtained by annealing the alloy.
Therefore, annealing in the middle of the cold rolling step is performed in a continuous furnace at a temperature range of 450 to 850 ° C. for 5 seconds to 1 minute, and stabilized annealing after final cold rolling is performed in a continuous furnace at 250 to 850 ° C. It is carried out in a temperature range of 850 ° C. for 5 seconds or more and 1 minute or less, and in each case, the rate of temperature rise and cooling is 10 ° C./second or more.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The copper alloy for terminals and connectors according to the present invention will be described in detail below. First, the reason for adding each additive element and the reason for limiting the composition will be described. (Ni) Ni dissolved in the mother phase has an effect of reducing the moving speed of dislocations under stress. This action improves stress relaxation resistance and strength. However, when the compound with P contained in the copper alloy of the present invention is formed by annealing, the amount of solid solution is reduced, so that the stress relaxation resistance is significantly reduced. Therefore, it is necessary to dissolve Ni in the copper alloy of the present invention. If the content is less than 0.8% by mass, the desired stress relaxation resistance and strength cannot be obtained. If the content exceeds 1.5% by mass, a compound with P is easily formed, and Electric conductivity and solder weather resistance are reduced, which is disadvantageous in cost. Therefore,
The addition amount of Ni was set to 0.8 to 1.5% by mass.

(Sn) Sn is effective in improving mechanical properties, in particular, in improving the balance between proof stress and elongation, and further in improving the formability, spring limit value and stress relaxation resistance.
If the content is less than 0.5% by mass, no effect is obtained, and if the content is more than 2.0% by mass, the electric conductivity is reduced, which is not economical. Therefore, the addition amount of Sn is set to 0.5 to 2.0% by mass. (Zn) Zn is an essential element for suppressing the migration of Cu and preventing the leakage current when water intrusion or dew condensation occurs between the poles of the electric or electronic component to which the voltage is applied. is there. Further, it is an element that improves strength, improves solder adhesion, and suppresses the generation of whiskers after Sn plating. If the Zn content is less than 0.015% by mass, the migration resistance, the improvement in solder adhesion, and the effect of suppressing whisker generation are small. , It is easy to cause corrosion cracking. Therefore, the Zn content is 0.015 to 5.0% by mass.
The following is assumed.

(P) P is an element mainly contributing to the improvement of the soundness of the ingot (deoxidation, molten metal flow, etc.). P is content,
If it is less than 0.005% by mass, the deoxidizing effect in the molten metal cannot be obtained. On the other hand, if it is added in excess of 0.1% by mass, the Ni-P intermetallic compound is easily precipitated, which is agglomerated and coarsened, impairing the mechanical properties, bending workability or plating properties of the product. Further, even if heat treatment is performed within a range in which the Ni-P compound is not precipitated, the addition of more than 0.1% by mass causes a peeling phenomenon of solder and Sn plating.
Therefore, the added amount of P is set to 0.005 to 0.1% by mass.
In the above range, the content of P is preferably less than 0.03% by mass, and more preferably less than 0.02% by mass.

(Mg, Fe) These elements have the effect of further improving the stress relaxation resistance when added in a small amount. However, any of these elements has no effect at less than 0.001% by mass.
When the content of g exceeds 0.2% by mass and the content of Fe exceeds 0.1% by mass, the conductivity, the weather resistance of the solder, and the bending workability are reduced. Therefore, the added amount of Mg is 0.001 to 0.2% by mass,
The amount of Fe added is 0.001 to 0.1% by mass.

(O, H) The alloy of the present invention also absorbs gas elements H and O at the stage of melting. Since these are expelled from the molten metal during solidification, the O content is reduced to 50 p.
If the H content is not regulated to not more than pm and the H content is not more than 2 ppm, the flowability of the molten metal during casting and the surface of the ingot are deteriorated. Also,
In particular, the residual H causes swelling of the surface due to rolling or annealing in the middle of the process, even if it reaches the plate material processing, which impairs the value as a product. Therefore, the O content is 50
The H content is regulated to 2 ppm or less.
The O content is 30 ppm or less and the H content is 1 p.
pm or less.

(Other selected elements) Ag, Ti, Si,
Ca, Mn, Be, Al, V, Cr, Co, Zr, N
b, Mo, In, Pb, Hf, Ta, and B have a content of each element of 0.0005 to 0.03%, and one or two of them.
When the content of at least one kind is in the range of 0.0005 to 0.3%, there is an effect of improving the heat resistance without impairing the stress relaxation resistance of the copper alloy of the present invention. No problem. When the content of one or more kinds exceeds 0.3%, an oxide is easily formed at the time of melting casting, hot rolling, or working heat treatment, and coarse crystals are easily generated. Hot workability, plating property, bending workability, etc. are easily reduced.

(Area Ratio of Precipitate) In order to improve the stress relaxation resistance of the copper alloy, it is necessary to control the microscopic structure inside the crystal grains that can be observed with a transmission electron microscope. The copper alloy requires at least one intermediate annealing during cold rolling to the final sheet thickness.
It is important to select conditions under which precipitates mainly composed of -P compounds are not formed in order to dramatically improve stress relaxation resistance. In other words, it is difficult in principle to reduce the formation of precipitates during annealing to 0, but by setting the area ratio of precipitates to 5% or less (in a state where most of the added elements are dissolved), the mother phase itself can be formed. Since the resistance to stress relaxation (the action of blocking the movement of a slip line and the disappearance of dislocations) can be maintained, the stress relaxation characteristics are improved. The area ratio is 5%
If the temperature exceeds the dislocation, dislocations in the parent phase will disappear, and as a result, the material properties will be reduced, and sufficient stress relaxation resistance cannot be obtained. Therefore, the area ratio of the precipitate is set to 5% or less.
In order to reduce the area ratio of the precipitates of the product after the stabilizing annealing to 5% or less, it is necessary that the area ratio of the precipitates after the intermediate annealing (before the stabilizing annealing) is 5% or less.

(Specification of conductivity) The conductivity of the copper alloy is as follows:
When annealing is performed during the cold rolling step or after the final cold rolling, the temperature becomes almost maximum under the annealing conditions of 450 to 500 ° C. and 4 hours. This is because the maximum amount of precipitates is generated by annealing. In the alloy of the present invention, as described above, Ni
Since the stress relaxation resistance deteriorates due to the formation of a precipitate mainly composed of a -P compound, the conductivity needs to be 90% or less of the maximum value. The conductivity of 90% or less substantially coincides with the precipitate area ratio of 5% or less. (Stress relaxation rate) In the case of a terminal or the like, the deterioration of the stress relaxation resistance causes troubles such as a decrease in the fitting force between the terminals, and impairs the reliability. However, Ni-
By suppressing the formation of the precipitate mainly composed of the P compound as described above, 30%
The following good stress relaxation resistance can be achieved.

(Working heat treatment step) The copper alloy of the present invention needs to be recrystallized before final cold rolling, but the area ratio of precipitates after annealing needs to be 5% or less. .
As heat treatment conditions therefor, 450 ° C./850° C., more preferably 550 ° C./650° C.
The temperature rises at a speed of at least 2 seconds and reaches a temperature within the above range for 5 seconds or more.
After heating and holding for less than a minute, it is necessary to cool at a rate of 10 ° C./sec or more. If the temperature is lower or shorter than this range, a completely recrystallized structure cannot be obtained. If the temperature is higher or longer than this range, or even if the temperature and the holding time are within the above ranges, the heating or cooling rate is less than 10 ° C./sec. In this case, the area ratio of the precipitate increases, and the stress relaxation resistance decreases. In addition, since the crystal grain size becomes large, deterioration of mechanical properties and the like occurs.

In order to further improve the stress relaxation resistance and the spring limit value, it is desirable to perform stabilizing annealing after the final rolling, but for that purpose, the temperature range is preferably from 250 to 850 ° C, more preferably from 300 to 450 ° C. 5 seconds or more at a temperature of 1
It is desirable to perform the heating and holding for less than a minute. If the temperature is lower or shorter than this range, the dislocations introduced by cold rolling are not properly released, and the stress relaxation resistance and the material properties cannot be improved. Further, even if the temperature is higher or longer than this range, or even if the temperature and the holding time are within the above ranges, if the temperature rise or cooling rate is less than 10 ° C./sec, the area ratio of the precipitates becomes large, and the stress relaxation resistance decreases. And
It is also economically disadvantageous.

[0020]

EXAMPLES The characteristics of the alloys of the present invention will be described below as comparative examples. Example 1 demonstrates the feasibility of producing a plate material and the effect of the added element. In Example 2, the effect of the area ratio of the precipitate and the effect of the heat treatment conditions will be verified. (Example 1) A copper alloy having a composition shown in Table 1 was melted in an air atmosphere under a charcoal coating in an electric furnace. Hot rolling the ingot,
Finished to a thickness of 15 mm. These sheets were subjected to a combination of cold rolling and the heat treatment of the present invention to obtain a sheet having a thickness of 0.25 mm. These were evaluated for material properties in the following manner. The copper alloy according to the present invention can also be manufactured by horizontal continuous casting that does not require hot rolling.

[0021]

[Table 1]

(Mechanical strength) The proof stress and the tensile strength were measured in accordance with JIS No. 5 test piece (n) with the longitudinal direction of the test piece being parallel to the rolling direction.
= 2). (Stress relaxation property) According to the cantilever method described in EMAS-3003, 80% of the room temperature proof stress was applied as the initial stress, and 17
After holding for 1000 hours at 0 ° C. or 200 ° C., the stress was removed, the amount of deflection was measured, and the stress relaxation rate was calculated (n = 5 at each temperature). (Electrical conductivity) The electrical conductivity was evaluated by measuring the electrical conductivity. The conductivity was measured based on JIS H505. (Solder weather resistance) MIL-STD-202F METH
After soldering based on OD 208D,
180 ° C at 1mmφ after 150 ℃ ・ 1000Hr in air
Debending was performed, and the presence or absence of peeling of the solder was visually confirmed (n = 3).

(Migration resistance)
A test piece having a width of 3.0 mm and a length of 80 mm was collected.
The test was performed as a set (n = 4). 1 and 2 are explanatory diagrams of a test method for measuring a leakage current using the test piece. In FIGS. 1 and 2, 2a and 2b are test pieces,
Reference numeral 3 denotes an ABS resin having a thickness of 1 mm, 3a denotes a hole formed in the ABS resin, and 4 denotes a holding plate for the ABS resin 3.
Reference numeral 5 denotes a clip having an insulating coating applied to the surface to press and fix the holding plate 4, reference numeral 6 denotes a battery, and reference numeral 7 denotes an electric wire. The test piece 2a, 2b has an electric wire 6 connected to an end. A dry test of applying a DC current of 14 V from the battery 6 to the two test pieces 2a and 2b shown in FIGS. 1 and 2 and immersing the test pieces in tap water for 5 minutes, followed by drying for 10 minutes, was performed 50 times.
The maximum leakage current during that time was measured with a high-sensitivity recorder (not shown).

(Bending workability) A B-type bending jig specified in the CESM0002 metal material W bending test, having a width of 10 m.
m, a test material processed to a length of 35 mm is sandwiched, and R / R is applied at a load of 1 t using a universal testing machine RH-30 manufactured by Shimadzu Corporation.
After performing a W bending process at t = 0, the 90 ° bent portion was further bent tightly with a load of 1 t, and the presence or absence of a crack in the bent portion was determined (n = 2). (Stress corrosion cracking resistance) 0.25 mmt x 1 from the above plate material
A 2.7 mm × 150 mm test piece was cut out and subjected to a stress corrosion cracking test by the method of Thompson (Materials
Research & Standards (196
1) Performed according to 1081) (n = 4). That is, the test piece was formed into a loop shape as shown in FIG.
, And exposed to a desiccator filled with saturated steam at a temperature of 40 ° C., and the time until the test piece fractured was measured.

Table 2 shows the above measurement results.

[0026]

[Table 2]

No. 2 shown in Table 2 In Nos. 1 to 5, the proof stress, the electrical conductivity, and the contact bending workability were good, the maximum leakage current value in the migration resistance was suppressed to a low value, and the solder weather resistance and the stress corrosion cracking resistance were also good. Excellent relaxation properties. On the other hand, No. Sample No. 6 lacks Ni and thus has a low proof stress and poor stress relaxation characteristics. No. Sample No. 7 has a low conductivity due to excessive addition of Ni and Sn, has poor bending workability, and has peeled off in a solder weather resistance test. No. In No. 8, because of insufficient Zn, peeling occurred in a solder weather resistance test, and the maximum leakage current value in migration resistance was high, which was fatal for automobile terminals. No. In No. 9, since Zn is excessively added, the conductivity is low, and breakage is recognized in a short time in a stress corrosion cracking resistance test. No. In No. 10, since P was insufficient, a sound ingot could not be obtained due to insufficient deoxidation.
No. In No. 11, since P was excessively added, peeling occurred in the solder weather resistance test, and the resistance to stress corrosion cracking was poor. No. In No. 12, the casting was abandoned because O exceeded the upper limit of the claimed range and the flowability of the molten metal was extremely reduced. No.
In No. 13, H exceeded the upper limit of the claimed range, and an ingot was obtained, but was abandoned because a crack occurred during hot rolling.

(Example 2) Copper alloys having the chemical components shown in Table 3 were melted under a charcoal coating in the air in a crypt furnace. In Table 3, since all the added elements are within the range specified by the present invention, a good hot-rolled material was easily obtained, and the cold-rollability was also good. Various plate heat treatments shown in Table 4 were performed on these plate members to obtain 0.25 mm plate members. The material properties, the area ratio of the precipitate, and the crystal grain size of these sheet materials were measured in the following manner. Table 5 shows the results. (Area ratio of precipitates) Using a TEM at a magnification of 90000 times (the most suitable magnification for confirming the precipitates) was 3
Visual observation was performed to measure the ratio of the precipitate per unit area, and the average value was defined as the area ratio. (Crystal Grain Size) Determined by a cutting method in accordance with the method for testing the grain size of copper-brought copper products according to JIS H0501.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

As shown in Table 5, as shown in FIG. 14-1 to 14
-3 is within the range of the thermo-mechanical treatment conditions defined in the present invention, the area ratio of the precipitate is 5% or less, the stress relaxation resistance is excellent, the proof stress, the contact bending workability, the migration resistance, the stress corrosion resistance. Also has excellent cracking properties. In the case of No. 2 which was annealed under the condition that the conductivity was maximum, 14-8
90% or less as compared with. On the other hand, No. 14
-4 to 14-8 are Ni-P by annealing during cold rolling.
Since precipitation mainly composed of a compound occurs, the area ratio of the precipitates exceeds 5% and the conductivity also becomes 90% or more of the maximum value, and the stress relaxation resistance decreases. In addition, No. No. 14-4 had a low annealing temperature and did not have a recrystallized structure. 14-5 to 14-8 are inferior in bending workability because the crystal grains are coarse.

No. In No. 14-9, the annealing temperature during the cold rolling was low and the time was short, so that the area ratio of the precipitate was 5% or less, but the bendability was poor because it was not recrystallized. The stress relaxation resistance is no. It cannot be said that it is better than 14-1 to 14-3. No. In No. 14-10, since the annealing temperature during the cold rolling was high, the area ratio of the precipitate was 5% or less, but the crystal grains became coarse and the bending workability was poor. The stress relaxation resistance is no. It cannot be said that it is better than 14-1 to 14-3.

[0034]

According to the present invention, in particular, excellent stress relaxation resistance, strength, close bending workability, migration resistance,
A copper alloy for terminals and connectors that is excellent in stress corrosion cracking resistance, solder weather resistance, etc. can be manufactured at low cost and with high productivity.

[Brief description of the drawings]

FIG. 1 is a plan view for explaining a method of measuring a maximum leakage current.

FIG. 2 is a side view thereof.

FIG. 3 is a view showing a loop-shaped test piece used for a stress corrosion cracking resistance test.

[Explanation of Signs] 2a, 2b Test pieces

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/08 C22F 1/08 K H01R 13/03 H01R 13/03 A // C22F 1/00 630 C22F 1 / 00A 630A 630K 640 640A 661 661A 685 685Z 691 691B 691C 691A 692 692A 692B

Claims (6)

[Claims] 1. Ni: 0.8 to 1.5 mass%, Sn:
0.5 to 2.0% by mass, Zn: 0.015% to 5.0% by mass or less, P: 0.005% to 0.1% by mass,
A copper alloy for terminals and connectors, characterized in that the balance consists of Cu and unavoidable impurities and the area ratio of precipitates is 5% or less. 2. The method according to claim 1, further comprising one or both of 0.001 to 0.2% by mass of Mg and 0.001 to 0.1% by mass of Fe. Copper alloy for terminals and connectors. 3. O content: 50 ppm or less, H content:
The copper alloy for terminals and connectors according to claim 1, wherein the content is 2 ppm or less. 4. Ag, Ti, Si, Ca, Mn, Be,
Al, V, Cr, Co, Zr, Nb, Mo, In, P
b, Hf, Ta, or one or more of B
005-0.03%, and 0.0005-0.3 in total amount
The copper alloy for terminals and connectors according to any one of claims 1 to 3, wherein 5. The copper alloy for terminals and connectors according to claim 1, wherein the copper alloy has a conductivity of 90% or less with respect to the maximum value of the conductivity obtained by annealing. 6. The copper alloy according to claim 1, wherein annealing in the middle of the cold rolling step is performed in a continuous furnace at a temperature of 450 to 850 ° C. for 5 seconds to 1 minute. Then, the stabilized annealing after the final cold rolling is performed in a continuous furnace for 2 hours.
Performed in a temperature range of 50 to 850 ° C. for 5 seconds to 1 minute,
A method for producing a copper alloy for terminals and connectors, wherein the rate of temperature rise and cooling at that time is 10 ° C./sec or more.