JP2007023357A - Copper alloy plate to be electrically connected through wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper alloy plate to be electrically connected through a wire, which has a tin or tin alloy plated film on the outermost layer, and inhibits a copper component from eluting due to contact-potential difference between dissimilar metals to inhibit the copper component from electrochemically migrating. <P>SOLUTION: The copper alloy plate includes: employing a copper alloy plate as a base material, which comprises 1.7-2.3% Fe, 0.02-0.2% Si, less than 0.1% Sn, less than 0.01% P, 0.03% or less Ni, 0.03% or less Mn, 1-4% Zn, 0.01-0.4% Mg and the balance Cu with unavoidable impurities; and forming a plated layer of tin or a tin alloy on the outermost surface layer of a rolled copper alloy plate, into a thickness of 0.5 μm or more when the cross section is observed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a copper alloy plate for electrical wiring connection such as a bus bar for an electrical wiring connection box (Junction Box, Junction Block, or abbreviation JB, relay box, or abbreviation RB) of an automobile. The present invention relates to a copper alloy plate for electrical wiring connection that has an effect of suppressing chemical migration.

This type of electrical wiring junction box is required to prevent electrochemical migration due to moisture. Specifically, in JB or RB, it is prevention of a decrease in insulating property of a copper alloy plate for energization called a bus bar arranged on a plane.
These copper alloy plates are subjected to surface coating such as tin or tin alloy plating in order to improve the corrosion resistance and maintain the low contact resistance of the electrical contact portion (see, for example, Patent Document 1 below). In these surface coatings, pre-plating is often used mainly for cost reduction by improving productivity.

  In such an electrical wiring junction box, it is necessary to take a circuit arrangement in which bus bars having both positive and negative potentials are adjacent to each other. In recent years, there is a tendency to reduce the interval between bus bars due to a demand for miniaturization in particular, and further studies have been made to increase the operating voltage (boost from 14V to 42V), so that the electrochemical migration of the bus bar material itself can be suppressed. Of particular importance.

  Usually, between the bus bars arranged in a plane, there is provided a resinous insulating partition such as nylon that is slightly higher than the thickness of the bus bar called a rib, but the electrochemical migration phenomenon is caused by this insulating partition. Occurs with or without presence. This is different from a tracking phenomenon that causes a decrease in insulation resistance of a so-called insulating partition. Regardless of the presence or absence of an insulating partition wall, when a water droplet adheres between adjacent bus bars due to surface tension or the like, an electrochemical migration phenomenon occurs therethrough, and the bus bar metal component is eluted from the high potential side bus bar.

The elution of the bus bar metal component is particularly remarkable in the bus bar in which the above-mentioned outermost layer is plated with tin or tin alloy. This is because the cut surface of the bus bar press-punched from the pre-plated copper alloy plate is a state in which the material (base material) is exposed and a large contact potential difference is generated between the tin plating and the copper alloy. This is because elution is more likely to proceed in the case of no plating. Therefore, the bus bar base material is required to have a property that the metal component does not easily elute even if tin plating is performed and a performance that guarantees long-term reliability of the tin plating itself. Here, the long-term reliability of tin plating means that tin plating is difficult to alloy and contact reliability is unlikely to decrease.
In addition, regarding the copper alloy plate for bus bars of an electrical wiring connection box, there is the following Patent Document 2 as a conventional technique. However, Patent Document 2 discloses a copper alloy with improved insulation resistance reduction, that is, improved tracking resistance, in a structure having an insulating partition between bus bars that are not subjected to surface coating such as tin plating. It does not disclose the long-term reliability of the tin plating and the suppression of electrochemical migration of the busbar subjected to the above.

JP 2004-68026 A JP 2003-321720 A

  Therefore, the present invention is a copper alloy plate for electric wiring connection in which tin or tin alloy plating is applied to the outermost layer, suppressing elution of copper components due to different metal contact potential differences, and copper having a high suppression effect on the occurrence of electrochemical migration The object is to obtain an alloy plate. At the same time, it is an object of the present invention to obtain a copper alloy plate having high electrical conductivity and proof strength required for long-term reliability of tin plating and a copper alloy plate for electrical wiring connection such as a bus bar.

The copper alloy plate for electrical wiring connection according to the present invention is Fe: 1.7-2.3%, Si: 0.02-0.2%, Sn: less than 0.1%, P: less than 0.01% , Ni: 0.03% or less, Mn: 0.03% or less, Zn: 1-4% and Mg: 0.01-0.4%, and the balance is subjected to rolling of a copper alloy composed of Cu and inevitable impurities. The outermost layer of the surface has a tin or tin alloy plating layer having a thickness of 0.5 μm or more as observed from the cross section.
The copper alloy further contains Pb: 0.0005 to 0.015% or / and Al: 1% or less as required. Desirably, Bi, As, Sb, and S are each limited to 0.003% or less, and the total of these is limited to 0.005% or less, O content is 10 ppm or less, and H content is 20 ppm or less. The

The copper alloy plate for electrical wiring connection according to the present invention can suppress electrochemical migration. It also has the characteristics required for JB busbar materials, especially JB busbar materials with higher voltage than conventional ones, such as long-term reliability of tin plating, high electrical conductivity and strength (strength), etc. It is suitable as a copper alloy plate for electrical wiring connection.
Furthermore, the copper alloy for electrical wiring connection according to the present invention does not require the entire surface plating with tin or a tin alloy, and has the advantage that the conventional tip plating process can be used as it is. There is an advantage that a bus bar can be manufactured.

The copper alloy according to the present invention is an alloy that hardly causes elution of a copper component due to electrochemical migration. Hereinafter, the reasons for limiting the composition of the copper alloy will be described.
Fe;
Fe precipitates finely and forms a local battery with the base material copper on the surface of the alloy, thereby suppressing elution of the copper component of the alloy. However, if the content exceeds 2.3%, coarse Fe particles are crystallized or precipitated, and the local battery balance that has been uniformly formed on the entire surface of the alloy is lost, and copper elution is accelerated due to local potential concentration. On the other hand, if it is less than 1.7%, the ingot structure at the time of casting is not refined, and external shear stress at the time of hot rolling is concentrated on the coarse grain boundary, so that hot rolling cracks are easily generated. Therefore, the Fe addition amount is set to 1.7 to 2.3%. Desirably, it is 1.8 to 2.2%, and in this range, a finely cast structure can be obtained stably, and copper elution due to electrochemical migration is suppressed.

Si, P;
Si is added as a deoxidizing material. P is often used as a deoxidizing material, but if this alloy system is P deoxidized so that more than 0.01% P remains, fine Fe-P precipitates are generated and regenerated during annealing. Inhibits crystals. If a uniform recrystallized structure cannot be obtained, local battery concentration of the copper alloy occurs locally and the amount of copper elution increases. Therefore, the residual amount of P needs to be less than 0.01%, and additional deoxidation is performed with Si. Si does not form an Fe compound that suppresses recrystallization. For additional deoxidation, it is necessary to add Si until 0.02% or more remains. However, if the residual amount exceeds 0.2%, the conductivity becomes lower than 50% IACS, and the current carrying capacity becomes more limited. Therefore, the Si residual amount is set to 0.02 to 0.2%. Desirably, it is 0.03 to 0.1%, and a proper deoxidation and uniform recrystallization structure can be obtained in this range.

Zn, Mg;
Since the solid solution Zn added in the copper alloy is at an electrochemically lower potential than copper, it is effective in preventing elution of the copper component. On the other hand, Mg has the same effect. However, in this alloy in which copper elution is suppressed by sufficient Fe addition, even if Zn and Mg are added alone, the suppression effect exceeding the effect obtained by Fe addition cannot be exhibited. However, when Fe, Mg, and Zn are added simultaneously, a synergistic effect is exhibited in suppressing copper component elution. Among these, the appropriate addition amount of Zn is 1 to 4%. If less than 1%, even if Fe and Mg are co-added, sufficient copper elution suppression effect cannot be obtained, and if added over 4%, the conductivity is less than 50% IACS, and the current carrying capacity is allowed. Create constraints. Desirably, it is Zn: 2-3%. The appropriate amount of Mg is 0.01 to 0.4%. If less than 0.01%, even if Fe and Zn are co-added, a sufficient copper elution suppression effect cannot be obtained, and if added over 0.4%, the conductivity falls below 50% IACS, and current is applied. This limits the current capacity. Desirably, Zn: 0.1 to 0.3%. For this alloy system, Mg and Zn must be co-added within the above-mentioned addition amount range.

Sn;
This alloy is an alloy system that secures strength by Fe precipitation or solid solution elements of Mg and Zn, but the strength (yield strength) can be further improved by the addition of Sn. This is effective in reducing the circuit width of the bus bar, that is, downsizing and reducing the materials used. However, if Sn is added in excess of 0.1%, the conductivity is below 50% IACS. Therefore, the Sn addition amount is less than 0.1%. Within this range, the conductivity is maintained at 50% IACS or more, and the strength is improved.
Ni;
Ni is mixed as an inevitable impurity, or has an effect of strengthening grain boundaries and preventing cracking during hot rolling in the copper alloy, and is added as necessary. However, if it exceeds 0.03%, the effect is saturated and the conductivity is lowered. Therefore, the content is 0.03% or less (including 0%).

Mn;
Mn is mixed as an inevitable impurity, or has an effect of strengthening grain boundaries and preventing cracking during hot rolling in the copper alloy, and is added as necessary. However, if it exceeds 0.03%, the effect is saturated and the conductivity is lowered. Therefore, the content is 0.03% or less (including 0%).
Pb;
Pb is mixed as an unavoidable impurity, or is added as necessary to improve machinability and press punchability. Pb does not affect the properties of the final product plate, but if added over 0.015%, it segregates at the grain boundaries and cracks occur during hot rolling. On the other hand, if it is less than 0.0005%, the above-mentioned action cannot be obtained. Therefore, the Pb content is 0.015% or less (including 0%), and 0.0005% or more is contained when the above action is required.

Al;
Al is an element that is most effective in suppressing copper elution in the present alloy system, and the copper elution suppressing effect can be further strengthened by addition of Al. However, since it has a great influence on the decrease in conductivity and may cause Sn plating peeling, the upper limit of the addition amount is 1%. If it exceeds 1%, the conductivity is less than 50% IACS, and tin plating is peeled off. Therefore, the total amount is restricted to 1% or less. Desirably, it is 0.6% or less.
Bi to H;
These elements are mixed as inevitable impurities. Bi, As, Sb, and S segregate at the grain boundaries and generate cracks during hot rolling, so it is desirable to limit each individually to 0.003% or less, and to a total of 0.005% or less. On the other hand, if O and H are large, blowholes are generated in the ingot, and if O is large, a large amount of oxide is generated in the molten metal and hinders the flow of the molten metal, so the O content is 10 ppm or less and the H content. Is preferably limited to 20 ppm or less.

Subsequently, tin or tin alloy plating of the copper alloy plate for electrical wiring connection according to the present invention will be described.
Tin or tin alloy plating is the only plating that enables low contact resistance maintenance of electrical contacts at low cost. Further, in the case of a bus bar to which a high voltage is applied, if there is no tin plating covering the surface, the elution of the copper component starts to occur on the entire surface of the high potential side bus bar, so that it is easy to transition to a short circuit state. Therefore, tin or tin alloy plating is essential for the present copper alloy plate.

On the other hand, if the entire surface of the copper alloy plate is covered with tin plating, elution of the copper component is suppressed, but the bus bar is usually made by stamping a pre-plated material from the viewpoint of cost reduction. Yes, the material of the press cut surface is exposed. Here, elution is most likely to proceed at a portion where the tin layer and the material are in contact with different metals, and the shortest electrode is most likely to be short-circuited due to reprecipitation of the eluted copper. For this reason, even with brass (C2600) frequently used in ordinary JB, the eluted and re-deposited copper hydroxide compound may short circuit between the bus bars, resulting in a smoke generation state.
Therefore, in order to suppress the short circuit (leak) phenomenon, it is necessary to combine a copper alloy (a copper alloy according to the present invention) that hardly causes elution of a copper component due to electrochemical migration and tin or tin alloy plating. Further, in order to maintain the low contact resistance of the contact and prevent the elution of the copper component on the entire surface of the bus bar, the tin or tin alloy plating needs to have a thickness of 0.5 μm or more as measured from the cross section. In addition, as tin alloy plating, tin-silver alloy plating, tin-copper alloy plating, etc. can be used.

In addition, the copper alloy plate according to the present invention has high electrical conductivity, long-term reliability of tin plating, and proof strength required for electrical wiring connecting copper alloy plates such as buspers. Hereinafter, these characteristics will be described.
conductivity;
The conductivity is an index of an allowable energization current value. The copper alloy for bus bars used as the energizing path needs to have a certain level of conductivity. Brass (C2600), which is frequently used as JB, has an electrical conductivity of 27% IACS, but in order to meet JB's demand for miniaturization, it has been found that about 50% of the electrical conductivity is required twice that of C2600. Yes.
Long-term reliability of tin plating;
Due to the diffusion of copper as a base material, tin plating of the outermost layer may change to a hard and brittle copper-tin alloy layer on the entire surface. When soft tin on the surface disappears, contact resistance increases and contact reliability decreases. Therefore, it is necessary to optimize the composition and suppress the copper-tin alloying of tin plating. Mg, Zn, Al, etc. are elements that are effective in preventing copper elution, but at the same time, when tin or tin alloy plating is applied directly to the base material without applying base plating, copper diffusion into tin plating is promoted. Has the effect of Solid solution elements other than these elements, such as Sn, Si, Ni, and Mn are also elements that promote alloying. Increasing the solid solution amount of these elements until the conductivity falls below 50% IACS results in alloying of the tin plating, and the long-term reliability of the tin plating that maintains the low contact resistance cannot be ensured.
In addition, a nickel plating base or a copper plating base can be applied to the base of the tin or tin alloy plating layer as necessary. Thereby, tin or tin alloy plating of the outermost layer is difficult to be alloyed, and contact reliability is further improved.

Proof stress;
The yield strength is an index of the neck strength of the rising portion of the bus bar male stub for connecting the female terminal. The bus bar's original purpose is the current-carrying path, which requires only the minimum strength that can maintain a flat shape. Start up and use as male terminal tab. This tab has a typical thickness of 0.64 or 0.8 mm, and the surface is coated with soft tin plating for ensuring low contact resistance. Receive resistance. Further, when the female connector is fitted, an assembly operator may carefully insert the female connector, and if neither of them has a proof stress of 350 N / mm ² or more, the male tab neck may be broken. It has been found that sufficient resistance to such deformation can be secured at a proof stress of 350 N / mm ² or more.

Copper alloys having the compositions shown in Tables 1 to 4 were melted and cast under the charcoal coating in the atmosphere in a kryptor furnace. Here, it was judged whether casting was possible.
Next, the ingot was held at 800 to 970 ° C. for 30 minutes, and then subjected to hot rolling at a processing rate of 60% to produce a plate material having a thickness of 18 mm. Here, whether or not cracking occurred during hot rolling was determined by visual inspection and a fluorescent flaw detection method. In the fluorescent flaw detection method, a fluorescent dye Super Glow DN-2800II for penetrant flaw detection manufactured by Marktec Co., Ltd. was applied to the entire surface of these test materials, washed and dried, and developed by spraying Super Glow DN-600S as a developer. Thereafter, this test material was irradiated with ultraviolet light.

  Next, this hot-rolled material was introduced into the next-step chamfering machine, and whether or not the milling blade of this chamfering machine was seized was determined. At this time, the milling blade was made of chromoly steel, and the milling blade was brazed with a tungsten carbide carbide chip to the base metal with silver brazing. The peripheral speed of the blade was 6 m / sec. The amount is 1.5 mm / side. Cooling ethanol was added dropwise without using cutting oil. Prepare 20 hot-rolled materials with dimensions of 200mm width x 18mm thickness x 180mm length for each alloy, and after double-side chamfering until they all have a thickness of 15mm, observe the surface of the milling blade by SEM, The state of seizure was investigated. If there was a chip welding trace on the blade surface, it was judged that there was seizure.

Whether or not the present invention can be manufactured was confirmed from the above criteria. The results are shown in Table 5.
No. Although No. 24 was castable, the Fe addition amount was insufficient, the effect of refinement of the cast structure was not exhibited, and cracking occurred during hot rolling.
No. Although 36 was castable, cracks occurred during hot rolling because the Pb content was excessive and the low melting point Pb segregated at the grain boundaries of the cast structure.
No. No. 37 could be cast and hot-rolled, but the amount of Pb added was insufficient, and seizure of the milling blade occurred during face milling of the hot-rolled material, so the subsequent process was abandoned.
No. Nos. 38, 39, 40, and 41 each have an excessive amount of Bi, As, Sb, and S. No. 42 was capable of casting because the total amount of these impurities was excessive, but cracking occurred during hot rolling.
No. No. 26 is a shortage of deoxidation due to shortage of Si addition. No. 43 had an excessive O content, increased oxides of various additive elements in the molten metal, deteriorated the fluidity of the molten metal, and gave up casting.
No. No. 44 could be cast, but the H content was excessive and blowholes were formed inside the ingot, so the process after hot rolling was abandoned.
On the other hand, No. in the range of the composition prescribed | regulated to this invention. 1 to 22 and No. out of range. 23-48. Nos. 23, 25, 27 to 35, and 45 to 48 have good ingot soundness and hot ductility, and can easily obtain a hot-rolled material, and do not cause seizure of a milling blade and can extend its life. is there.

  Subsequently, no. 1-22 and No.1. 23, 25, 27-34, 45-48 hot-rolled sheets were cold-rolled to a thickness of 1.28 mm, and the rolled material wrapped with a charcoal seal was subjected to intermediate annealing in an electric furnace at 540 ° C. for 2 hours. . Next, after removing the oxide scale of the plate material, the product plate thickness was 0.64 mm by final rolling. Further, 400 ° C. strain relief annealing (finish annealing) was performed in a glass stone furnace for 20 seconds. Finally, the adhering glass stone and oxide scale were removed to obtain a final product. All the plate materials had good cold rollability and could be easily manufactured to the final product plate thickness.

The sample with the final thickness of 0.64 mmt was subjected to electrotin plating. Specifically, a tin plating bath (20 ° C.) comprising stannous sulfate 40 g / lit, sulfuric acid 100 g / lit, cresol sulfonic acid 30 g / lit, formalin 5 ml / lit, dispersant 20 g / lit, brightener 10 ml / lit Then, tin plating was performed at a current density of 2.5 A / dm ² . After plating, the sample was cut out, the cross section was cut with a microtome, and the tin plating thickness viewed from the cross section was measured by SEM imaging. Table 6 shows the tin plating thickness of each sample.
Subsequently, for each sample, the tensile strength, proof stress, and conductivity were measured in the following manner, and the copper elution suppression effect, the presence or absence of a short circuit due to the electrochemical migration phenomenon, and the long-term reliability of tin plating were verified. . The results are shown in Table 6.

[Tensile strength, yield strength]
A JIS No. 5 tensile test piece was produced by machining, and a tensile test was carried out using a universal testing machine UH-10B manufactured by Shimadzu Corporation. Here, the proof stress is a tensile strength corresponding to a permanent elongation of 0.2% defined in JIS Z2241.
No. 1 to 22 has a proof stress of 350 N / mm ² or more.

[conductivity]
In accordance with the non-ferrous metal conductivity measuring method specified in JIS H0505, a four-terminal method using a double bridge 5752 manufactured by Yokogawa Electric was used.
No. 1-No. No. 22 has a conductivity of 50% IACS or more. No. 25 has an excessive amount of Si added. No. 27 has an excessive Zn addition amount. No. 29 has an excessive amount of added Mg. No. 31 has an excessive amount of Sn addition, so No. 34 has an excessive amount of Ni added. No. 35 has an excessive amount of Mn added. No. 45 has an excess amount of Al added, so the conductivity does not reach 50% IACS.

[Copper elution suppression effect]
When the rolled surface of the copper alloy for busbars is coated with tin or tin alloy plating on both sides and the pressed surface is exposed, the difference in contact potential between dissimilar metals occurs between the plating layer and the copper alloy. Yes. When moisture intervenes between two bus bars to which both positive and negative potentials are applied, and current flows in a direction that promotes this potential difference, elution of the copper alloy starts from the plating-copper alloy contact surface on the high potential side. In such a state where the concentration of interstitial moisture occurs (for example, self-heating due to a decrease in insulation resistance or drying due to high temperature environment), the electrical conductivity of the interstitial moisture rapidly increases and the eluted metal reprecipitates, Eventually a short-circuit current (leakage current) begins to flow between the insulated bus bars. Therefore, it is possible to verify the copper elution suppression effect by measuring how much the copper alloy has disappeared from the plating-copper alloy contact surface of the bus bar when immersed in water.

  Specifically, two test pieces (corresponding to a bus bar) having a thickness of 0.64 mm, a width of 6.0 mm, and a length of 120 mm obtained by cutting from each sample are separated by a press cut surface of 1.2 mm. It arrange | positions on the same plane (on MC nylon resin board) so that it may face in parallel. A rod-shaped Mc nylon having a width of 1 mm, a height of 0.66 mm, and a length of 100 mm is arranged in the center between the two test pieces, and is installed so that the distance between the two test pieces is 0.1 mm. The two ends of the two test pieces and both ends of the MC nylon resin plate are fixed by winding a Teflon (registered trademark) tape having a width of 10 mm. A constant voltage power source (Kikusui PAD55-35L) is connected to the two test pieces, and a DC voltage of 42 volts is applied between the two test pieces. In this state, the test piece with MC nylon resin plate is immersed in a 50 ppm NaCl aqueous solution stored in a 1 liter beaker. After being immersed for 5 minutes, it is lifted and left in the atmosphere for 5 minutes. After 10 cycles of this 5-minute immersion and 5-minute pull-up drying, the test piece connected to the constant voltage power supply plus side is removed, and the resin is embedded so that the 6 mm wide × 0.64 mm thick surface becomes the observation surface. The surface was mirror-polished, and the depth of burrs generated at the interface between the tin plating layer and the base material was measured. The results are also shown in Table 6. When the depth of punching exceeds 0.2 mm, there is no effect of suppressing copper elution.

  As shown in Table 6, no. 1-No. No. 22 had a depth of 0.2 mm or less. In contrast, no. In No. 23, an excessive amount of Fe was added, so that coarse Fe precipitates and crystallized substances were generated, uneven and local copper elution was promoted, and the base material cross section was deeply swollen. No. 30 is insufficient Mg addition amount. No. 33 was insufficient Zn addition amount and copper elution could not be suppressed. No. In 46, recrystallization was inhibited, and uneven and local copper elution was promoted, so that the cross-section of the base metal was deepened.

[Presence or absence of short circuit due to electrochemical migration phenomenon]
When positive and negative potentials are applied to adjacent bus bars and moisture intervenes between the bus bars, the copper component elutes mainly from the anode side as described above, and the intervening moisture evaporates and concentrates again. Precipitate. Short-circuit current (leakage current) starts to flow between the bus bars due to cross-linking of the copper, copper hydroxide, and copper oxide reprecipitate. Therefore, if it is confirmed whether leakage current flows between the bus bars when the cycle of drying by supplying intervening water assuming dew condensation and the like is repeated, whether or not a short circuit occurs due to electrochemical migration can be verified.

  Specifically, two test pieces (corresponding to a bus bar) having a thickness of 0.64 mm, a width of 6.0 mm, and a length of 140 mm obtained by cutting from each sample are R = 0.3 mm at 20 mm from one end. Is bent to 90 degrees and processed into a "<" shape. The two test pieces are fixed to an MC nylon resin plate having a length of 100 mm so that a 20 mm portion where the two test pieces are bent out. When the two test pieces are fixed, the side portions of 100 mm in length are fixed in parallel so as to face each other with an interval of 1.2 mm. A rod-shaped Mc nylon having a width of 1 mm, a height of 0.66 mm, and a length of 100 mm is arranged in the center between the two test pieces, and is installed so that the distance between the two test pieces is 0.1 mm. The test piece is fixed by winding a Teflon (registered trademark) tape having a width of 10 mm around both ends of the MC nylon resin plate to which two test pieces are fixed. A constant voltage power source (Kikusui PAD55-35L) is connected to the two test pieces, and a DC voltage of 42 volts is applied between the two test pieces. In this state, the bent 20 mm long portion that protrudes is held horizontally, and the test piece with MC nylon resin plate is immersed vertically in a 50 ppm NaCl aqueous solution stored in a 1 liter beaker. After being immersed for 1 second, it is lifted and left in the atmosphere for 5 minutes. This 1-second soaking, 5 minute pull-up and drying were repeated 20 cycles, and the leakage current flowing between the test pieces in the 20 cycles was continuously recorded with a pen recorder. The leakage current (maximum leakage current value) is also shown in Table 6. It has been found that if the leakage current (maximum leakage current value) exceeds 0.5 A during 20 cycles, there is no effect of suppressing leakage current due to electrochemical migration.

As shown in Table 6, no. 1 to 22 each had a maximum leakage current value of 0.5 A or less. On the other hand, no. In No. 28, the amount of Zn added was insufficient, so that the copper elution and the maximum leakage current value could not satisfy the specified values. Similarly, no. Since the amount of Mg added was insufficient, the copper elution and the maximum leakage current value could not satisfy the specified values. No. Since Mg was not added to 32, elution of copper was suppressed by a large amount of solid solution of Zn, but the maximum leakage current value exceeded the specified value.
No. 47 is a copper alloy within the specified range of the present invention, but since the tin plating thickness is thin, the function as a copper elution barrier is weak, and the copper base material on the contact surface of different metals, that is, the copper elution amount in the cross section is Although suppressed, elution from the rolled surface could not be stopped, and the maximum leakage current value was high, which was inappropriate. No. No. 48 is a case where plating is not performed, but copper elution cannot be suppressed. As a result, a short circuit phenomenon between bus bars is caused, and the maximum leakage current value is increased.

[Long-term reliability of tin plating]
In order to ensure the contact reliability of bus bar male tabs and other parts for a long period of time, the outermost tin component will remain even if exposed to engine / exhaust system heat, etc. The pure tin component must remain on the outermost surface without alloying. As a result of a heating acceleration test that reproduces this, the long-term reliability of tin or tin alloy plating can be evaluated by quantifying how much pure tin component remains on the outermost surface.
Specifically, a test piece having a thickness of 0.64 mm, a width of 100 mm, and a length of 100 mm obtained by cutting from each sample is exposed to an air circulation oven at 150 ° C. for 500 hours to promote diffusion. A composition image of these test piece surfaces is taken with a low-magnification SEM (magnification 50 times). The copper-tin alloy layer portion is photographed in black by composition image photographing, and is clearly distinguished from a pure tin component photographed in white. When the proportion of the black portion (copper-tin alloy layer) exceeds 50% with respect to the shooting section 20 mm × 20 mm, it is known that the alloy layer has grown to the outermost surface and contact resistance cannot be ensured. Yes. The long-term reliability of tin plating was determined by setting the case where the black partial area did not exceed 50% to ○ (pass) and the case where it exceeded 50% as × (fail).

  As shown in Table 6, no. 1 to 22 are all ◯, and long-term reliability of tin plating can be secured. On the other hand, no. Nos. 25, 27, 29, 31, 33, 35, and 45 contain excessive amounts of Si, Zn, Mg, Sn, Ni, Mn, and Al, respectively, and the electrical conductivity is less than 50% IACS, so that long-term reliability of tin plating cannot be ensured.

Claims (4)

Fe: 1.7 to 2.3% (mass%, the same applies hereinafter), Si: 0.02 to 0.2%, Sn: less than 0.1%, P: less than 0.01%, Ni: 0.03 % Or less, Mn: 0.03% or less, Zn: 1-4% and Mg: 0.01-0.4%, and the outermost layer on the surface subjected to rolling of a copper alloy composed of Cu and inevitable impurities. The copper alloy plate for electrical wiring connection which has the tin or tin alloy plating layer whose thickness observed from the cross section is 0.5 micrometer or more. The said copper alloy contains Pb: 0.0005-0.015% further, The copper alloy board for an electrical wiring connection described in Claim 1 characterized by the above-mentioned. The said copper alloy contains Al 1% or less further, The copper alloy plate for an electrical wiring connection described in Claim 1 or 2 characterized by the above-mentioned. In the copper alloy, Bi, As, Sb, and S are 0.003% or less in individual parts, and the total of these is 0.005% or less, the O content is 10 ppm or less, and the H content is 20 ppm or less. The copper alloy plate for electrical wiring connection according to any one of claims 1 to 3, wherein