JP2016166397A - Tin plated copper alloy terminal material, manufacturing method therefor and wire terminal part structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal material hardly generating electric corrosion by using a copper alloy substrate as a crimp terminal crimped to a terminal of a wire consisting of an aluminum wire material.SOLUTION: A copper tin alloy layer is formed on a substrate consisting of copper alloy and a tin layer is formed on the copper tin alloy layer. A tin magnesium oxide layer containing tin:5 atom% or more and 30 atom% or less and magnesium:15 atom% or more and 45 atom% or less and the balance oxygen is formed with thickness of 2 nm or more and 15 nm or less in terms of SiOon the tin layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tin-plated copper alloy terminal material that is used as a terminal to be crimped to an end of an electric wire made of an aluminum wire material, and tin-plated on the surface of a copper alloy base material. It is related with the electric wire terminal part structure formed by attaching.

Conventionally, by crimping a terminal made of copper or a copper alloy to the terminal part of an electric wire made of copper or a copper alloy, and connecting the terminal to a terminal of another device, Connecting to equipment is done. Further, in order to reduce the weight of the electric wire, the electric wire may be made of aluminum or aluminum alloy instead of copper or copper alloy.
For example, Patent Document 1 discloses an aluminum wire for an automobile wire harness made of an aluminum alloy.

  By the way, when the electric wire (conducting wire) is made of aluminum or an aluminum alloy and the terminal is made of copper or a copper alloy, when water enters the crimping portion (engagement portion between the terminal and the electric wire), it depends on the potential difference between different metals. Galvanic corrosion may occur. And with the corrosion of the electric wire, there is a risk that an increase in the electric resistance value at the crimping portion and a decrease in the adhering force (bonding force between the terminal and the electric wire) may occur.

Examples of methods for preventing this corrosion include those described in Patent Document 2 and Patent Document 3.
Patent Document 2 includes a metal part made of a first metal material and a second metal material having a standard electrode potential value smaller than that of the first metal material, and at least a surface of the metal part. It is composed of an intermediate layer that is thinly provided by plating and a third metal material having a standard electrode potential smaller than that of the second metal material, and is thinly provided by plating on at least a part of the surface of the intermediate layer. A terminal having a surface layer is disclosed. The first metal material is copper or an alloy thereof, the second metal material is lead or an alloy thereof, tin or an alloy thereof, nickel or an alloy thereof, zinc or an alloy thereof, and the third metal material is Aluminum or its alloys are described.

  In Patent Document 3, in the terminal region of the covered electric wire, the caulking portion formed at one end of the terminal metal fitting is caulked along the outer periphery of the covering portion of the covered electric wire, and at least the end exposed region of the caulking portion and the vicinity thereof A wire harness terminal structure is disclosed in which the entire outer periphery of the wire harness is completely covered with a mold resin.

JP 2004-134212 A JP 2013-33656 A JP 2011-222243 A

  However, although the structure described in Patent Document 3 can prevent corrosion, there is a problem that the manufacturing cost increases due to the addition of the resin molding process, and further, the miniaturization of the wire harness is hindered by the increase of the terminal cross-sectional area due to the resin. In order to carry out the aluminum-based plating that is the third metal material described in 2, an ionic liquid or the like is used, which causes a problem that it is very expensive.

  By the way, in many cases, a tin-plated terminal material obtained by subjecting a copper or copper alloy base material to tin plating and reflow treatment is used. When this tin-plated terminal material is crimped to an aluminum electric wire, it should be difficult to cause electrolytic corrosion because tin and aluminum have close corrosion potentials, but electrolytic corrosion occurs when salt water or the like adheres to the crimping portion.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a terminal material that does not cause electrolytic corrosion using a copper alloy base material as a terminal to be crimped to an end of an electric wire made of an aluminum wire. And

As a result of diligent research on the electrolytic corrosion of the tin-plated terminal material, the inventors found that the surface tin layer disappears quickly due to the corrosive action of salt water, and the underlying copper-tin alloy layer is exposed, resulting in electrolytic corrosion. It was. Since the corrosion potential of the copper-tin alloy layer is close to that of copper, a high potential difference is generated and aluminum is preferentially corroded.
Therefore, by forming a layer resistant to salt water on the tin layer, corrosion of the tin layer was prevented and exposure of the copper tin alloy layer was suppressed.

That is, in the tin-plated copper alloy terminal material of the present invention, a copper tin alloy layer is formed on a base material made of a copper alloy, and a tin layer is formed on the copper tin alloy layer. Further, a tin magnesium oxide layer containing tin: 5 at% to 30 at%, magnesium: 15 at% to 45 at%, and the balance being oxygen is formed with a thickness of 2 nm to 15 nm in terms of SiO ₂ . .

  In the tin magnesium oxide layer, if the tin content is less than 5 at%, the electrical conductivity of the tin magnesium oxide layer is lowered, so that the contact resistance is deteriorated, and if it exceeds 30 at%, the anticorrosion effect is poor. When the magnesium content is less than 15 at%, the anticorrosion effect is poor, and when it exceeds 45 at%, the solder wettability is deteriorated. Moreover, if the thickness is less than 2 nm, there is no anticorrosion effect on the tin layer, and if it exceeds 15 nm, the solder wettability is deteriorated.

  In the method for producing a tin-plated copper alloy terminal material of the present invention, a copper plating layer and a tin plating layer are laminated in this order on a base material made of a copper alloy containing 0.5% by mass or more and 3% by mass or less of magnesium. Heat treatment is performed at a temperature of 235 ° C. to 600 ° C. for a time of 5 seconds to 30 seconds, and an oxygen-containing gas having a temperature of 20 ° C. to 80 ° C. is supplied to the surface to form a tin magnesium oxide layer.

  If the magnesium content of the substrate is less than 0.5% by mass, a sufficient amount of magnesium cannot be supplied to the surface during the heat treatment, and if it exceeds 3% by mass, the amount of magnesium supplied to the surface during the heat treatment becomes excessive. Solder wettability. If the temperature of the heat treatment is less than 235 ° C. or the time is less than 5 seconds, the magnesium cannot be sufficiently supplied to the tin layer, and if it exceeds 600 ° C. or heated for more than 30 seconds, the supply amount of magnesium becomes excessive, and the solder The wettability becomes worse. If the temperature of the oxygen-containing gas is less than 20 ° C., an oxide cannot be formed sufficiently, and if it exceeds 80 ° C., it is excessively oxidized and the contact resistance increases.

  And the terminal produced using the tin plating copper alloy terminal material of this invention was crimped | bonded to the terminal of the electric wire which consists of aluminum or an aluminum alloy, and it was set as the electric wire terminal part structure.

  According to the present invention, the tin-magnesium oxide layer provided on the tin layer can prevent corrosion, and the disappearance of the tin layer and the exposure of the copper-tin alloy layer can be prevented. It is possible to prevent food and suppress an increase in electric resistance value and a decrease in fixing force.

It is sectional drawing which shows typically the tin plating copper alloy terminal material of this invention. It is a perspective view which shows the example of the terminal to which the terminal material of this invention is applied. It is a front view which shows the terminal part of the electric wire which crimped | bonded the terminal of FIG.

A tin-plated copper alloy terminal material according to an embodiment of the present invention and a manufacturing method thereof will be described.
As schematically shown in FIG. 1, the tin-plated copper alloy terminal material 1 according to the present embodiment has a copper-tin alloy layer 3 formed on a base material 2 made of a copper alloy. A tin layer 4 is formed on the tin layer 4, and a tin magnesium oxide layer 5 is formed on the tin layer 4.

  The base material 2 may be a copper alloy containing magnesium (Mg) in a range of 0.5% by mass or more and 3% by mass or less, and a copper alloy consisting of copper (Cu) and inevitable impurities is suitable. is there. In addition to magnesium, phosphorus (P) may be contained in the range of 0.01 mass% to 0.05 mass%.

  Magnesium diffuses to the surface during the heat treatment described below and reacts with tin to form tin magnesium oxide. If the magnesium content is less than 0.5% by mass, a sufficient amount of magnesium cannot be supplied to the surface during the heat treatment, and if it exceeds 3% by mass, the amount of magnesium supplied to the surface during the heat treatment becomes too large. Solder wettability deteriorates.

The copper-tin alloy layer 3 is a layer formed by sequentially forming a copper plating layer and a tin plating layer on the base material 2 and performing the above-described heat treatment, and the copper tin alloy layer 3 is mainly composed of Cu ₆ Sn _5. It is a compound layer of a tin alloy (Cu-Sn). The average thickness of the copper-tin alloy layer 3 is preferably 0.4 μm or more and 1 μm or less. If it is too thin, whiskers are likely to be generated, and if it is too thick, it is uneconomical as a terminal material.

  The tin layer 4 is a layer made of tin (Sn) formed by heat treatment of the above-described tin plating layer. The average thickness of the tin layer 4 is preferably 0.2 μm or more and 2 μm or less. If it is too thin, there is a risk of lowering solder wettability and electrical connection reliability. If it is too thick, the dynamic friction coefficient of the surface is increased. At the same time, the attachment / detachment resistance when used with a connector or the like tends to increase.

The tin-magnesium oxide layer 5 is a layer of tin-magnesium oxide (Sn—Mg—O) formed on the tin layer 4 after the heat treatment described above, and is measured by an AES (Auger Electron Spectroscopy) analyzer. It is formed so as to cover the entire surface of the tin layer 5 with a SiO ₂ equivalent thickness of ₂ nm or more and 15 nm or less. If the thickness is less than 2 nm, there is no anticorrosive effect on the tin layer 5, and if it exceeds 15 nm, the solder wettability is deteriorated.

  The composition of the tin-magnesium oxide layer 5 is tin: 5 at% or more and 30 at% or less, magnesium: 15 at% or more and 45 at% or less, and the balance is oxygen. If the tin content is less than 5 at%, the electrical conductivity of the tin magnesium oxide layer 5 is lowered, so that the contact resistance is deteriorated, and if it exceeds 30 at%, the anticorrosion effect becomes poor. When the magnesium content is less than 15 at%, the anticorrosion effect is poor, and when it exceeds 45 at%, the solder wettability is deteriorated.

Next, the manufacturing method of this tin plating copper alloy terminal material 1 is demonstrated.
As the base material 2, a magnesium alloy having a magnesium content of 0.5 mass% or more and 3 mass% or less, for example, a copper alloy “MSP1” containing magnesium from Mitsubishi Shindoh Co., Ltd. (magnesium: 0.5 to 0.9 mass%, A plate material made of phosphorus (0.04% by mass or less) is used, and the surface of the plate material is treated by degreasing, pickling, etc., and then copper plating and tin plating are performed in this order.

For copper plating, a general copper plating bath may be used. For example, a copper sulfate bath mainly composed of copper sulfate (CuSO ₄ ) and sulfuric acid (H ₂ SO ₄ ) may be used. The temperature of the plating bath is, for example, 20 ° C. or more and 50 ° C. or less, and the current density is 1 A / dm ² or more and 40 A / dm ² or less. The film thickness of the copper plating layer formed by this copper plating is preferably 0.03 μm or more and 0.5 μm or less. If it is too thick, diffusion of magnesium in the base material is inhibited during heat treatment, and magnesium can be supplied to the tin layer. It becomes difficult.

As a plating bath for forming the tin plating layer, a general tin plating bath may be used. For example, a sulfuric acid bath mainly composed of sulfuric acid (H ₂ SO ₄ ) and stannous sulfate (SnSO ₄ ) is used. Can do. The temperature of the plating bath is, for example, 15 ° C. or more and 35 ° C. or less, and the current density is 1 A / dm ² or more and 30 A / dm ² or less. The film thickness of this tin plating layer is 0.6 μm or more and 2.5 μm or less.

  As the heat treatment, after performing a reflow treatment in which the surface temperature of the material is 235 ° C. or more and 600 ° C. or less in a reducing atmosphere and heated for 5 seconds to 30 seconds, the oxygen concentration is 15% by volume to 30% by volume. The following oxygen-containing gas is supplied to the surface of the material at a temperature of 10 ° C. or higher and 80 ° C. or lower for a time of 1 second to 30 seconds to cool and solidify the surface, and then 20 ° C. The water of 60 ° C. or lower is supplied and cooled.

  By this heat treatment, copper and tin react between the base material 2 and the tin plating layer on the surface to form a copper tin alloy layer 3 made of the compound, and the copper tin alloy layer 3 remains on the copper tin alloy layer 3. A tin layer 4 is disposed, and a tin magnesium oxide layer 5 is formed on the tin layer 4. This tin magnesium oxide layer 5 is a compound layer formed by magnesium being diffused from the copper alloy of the base material 2 to the upper layer by heat treatment and reacting with the oxygen-containing gas and tin supplied to the surface of the tin layer 4. is there.

  Under this heat treatment condition, if the temperature at the time of heating is less than 235 ° C. or the heating time is less than 5 seconds, magnesium cannot be sufficiently supplied to the tin layer 4, and if heated above 600 ° C. or more than 30 seconds, the magnesium The supply amount becomes excessive and solder wettability is deteriorated. Further, when the temperature of the oxygen-containing gas at the time of cooling is less than 10 ° C. or the supply time to the material surface is less than 1 second, the oxide cannot be sufficiently formed, and the temperature exceeds 80 ° C. or the supply time is 30 seconds. When it exceeds, it will be oxidized excessively and contact resistance will increase. If the oxygen content of the oxygen-containing gas is less than 15% by volume, oxides are not formed and the anticorrosion effect becomes poor. When it exceeds 30 volume%, it will be oxidized excessively and contact resistance will deteriorate.

And the tin plating copper alloy terminal material 1 manufactured in this way is shape | molded by the terminal 10 of a shape as shown, for example in FIG.
The terminal 10 is a female terminal in the example of FIG. 2, and is a connecting portion 11 into which a male terminal (not shown) is fitted from the tip, and a caulking portion caulking portion in which the exposed core wire 12 a of the electric wire 12 is caulked. 13. A covering caulking portion 14 to which the covering portion 12b of the electric wire 12 is caulked is integrally formed in this order.
FIG. 3 shows a terminal structure in which the terminal 10 is caulked to the electric wire 12, and the core caulking portion 13 is in direct contact with the core wire 12 a of the electric wire 12.

In this terminal 10, since the tin magnesium oxide layer 5 is formed on the tin layer 4 as described above, disappearance due to corrosion of the tin layer 4 can be prevented. For this reason, since the exposure of the copper tin alloy layer 3 under the tin layer 4 can be prevented, the electric wire 12 to which the terminal 10 is connected is an aluminum core wire 12a, and the core wire caulking portion 13 of the terminal 10 is used. Even if it becomes the state crimped | bonded to the aluminum core wire 12a, generation | occurrence | production of the electrolytic corrosion with the aluminum core wire 12a can be prevented reliably.
In addition, the electric wire 12 can be applied to any of a bare electric wire with a conductive wire exposed and a covered electric wire having a conductive wire as a core wire and a periphery covered with an insulating layer. In the present invention, both the bare wire and the core wire of the covered wire are referred to as an electric wire.

  A copper plating layer and a tin plating layer were formed on a copper alloy plate having a magnesium content shown in Table 1. The copper plating layer had a thickness shown in Table 1, and all the tin plating layers had a thickness of 1 μm. The copper alloy plate with plating layer was subjected to the heat treatment (reflow treatment and oxide formation treatment) shown in Table 1, and then poured into water at 40 ° C. to perform a cooling treatment to obtain a sample.

  About the obtained sample, the thickness of the surface oxide layer, the composition of the oxide layer (magnesium concentration and tin concentration) were measured, and solder wettability and contact resistance were evaluated.

<Thickness of oxide layer>
Using an AES (Auger Electron Spectroscopy) analyzer PHI700 manufactured by ULVAC-PHI Co., Ltd., etching was performed with argon ions until no oxygen was detected on the sample surface, and the time required for the etching was measured. The measurement was performed by scanning □ 1 μm with an electron beam diameter of 10 nm, and then detecting Auger electrons generated from that region. The “SiO ₂ equivalent film thickness” of the oxide layer was calculated from the required time using the etching rate of SiO ₂ measured in advance with the same model. The method of calculating the SiO ₂ etching rate was calculated by dividing the time required for etching 20nm etched with argon ion side of the SiO ₂ film of a thickness of 20nm is in 1.5mm square area of . In the case of the above analysis apparatus, since it took 17 minutes, the etching rate is 1.2 nm / min. For example, sample no. In No. 1, since etching took 1 minute and 40 seconds (1.7 minutes), the SiO ₂ equivalent film thickness was set to 2 nm. AES has an excellent depth resolution of about 0.5 nm, but the etching time with an Ar ion beam differs depending on the material. Therefore, to obtain a numerical value of the film thickness, a sample with a known and flat film thickness is procured. Then, the etching rate must be calculated. Since the above is not easy, the “SiO ₂ equivalent film thickness” calculated from the time required for etching is defined by the etching rate calculated for the SiO ₂ film whose film thickness is known. Therefore, it should be noted that the “SiO ₂ equivalent film thickness” is different from the actual oxide film thickness. When the film thickness is defined by the SiO ₂ conversion etching rate, even if the actual film thickness is unknown, the film thickness is unambiguous and can be quantitatively evaluated. As a method of measuring a film thickness of several nm or less, the film thickness can also be measured by direct observation with a TEM in addition to AES. Although TEM can observe up to one atomic layer, it is a special case such as a single crystal, and the plating material like this case is affected by the surface roughness, so it has a resolution of about 1 nm. In the case of AES, although it depends on the atoms, the detection depth is 3 to 5 atomic layers, so that it can be detected up to about 0.5 nm. As for the analysis range, TEM can only measure up to about 5 μm on the X-axis, so only local information can be obtained, but AES can obtain information up to about 100 μm, and it is average over a wide range. Information can be obtained. Therefore, AES was used for the measurement of the oxide film thickness this time.

<Composition of oxide layer (magnesium concentration and tin concentration)>
The sample surface was subjected to argon etching for 1 minute using an AES analyzer PHI700 manufactured by ULVAC-PHI, Inc., and the adsorbed carbon on the surface was removed, followed by quantitative analysis.

<Solder wettability>
The solder wettability is determined by applying a flux on the sample surface under the following flux application conditions using a solder checker WET-6000 manufactured by Reska Co., Ltd. according to the soldering test method (equilibrium method) of JIS-C0053. And the wettability of lead-free solder.
(Flux application conditions)
Flux: 25% by mass rosin-ethanol, flux temperature: room temperature, flux depth: 8 mm, flux immersion time: 5 seconds, draining method: edge was applied to filter paper for 5 seconds to remove the flux.
A sample coated with this flux is fixed to the apparatus, immersed in lead-free solder in a solder bath at a depth of 1 mm at a depth of 1 mm and held for 30 seconds, and a zero cross time of 5 seconds or less is acceptable. Anything exceeding that was considered defective.

<Contact resistance>
The contact resistance measurement method conforms to JCBA-T323, using a 4-terminal contact resistance tester (manufactured by Yamazaki Seiki Laboratories: CRS-113-AU), sliding resistance (1 mm) and contact resistance at 0.98 N Was measured. Measurement was performed on the plated surface of the flat plate sample.

<Change rate of contact resistance>
The sample was processed into a terminal shape, crimped to an aluminum wire, the contact resistance between the aluminum wire and the terminal was measured, and then subjected to a salt spray test according to JIS Z 2371 for 168 hours, and then again aluminum The contact resistance between the wire and the terminal was measured, and the change rate of the contact resistance was calculated. The contact resistance was measured in accordance with JIS-C-5402 using a 4-terminal contact resistance tester (manufactured by Yamazaki Seiki Laboratory: CRS-113-AU).
These measurement results and evaluation results are shown in Table 2.

As apparent from Table 2, the sample No. 1-4 show that the solder wettability is good, the change in contact resistance after the salt spray test is small, and no corrosion or electrolytic corrosion occurs.
In contrast, sample no. In No. 5, since the substrate did not contain magnesium, the oxide layer did not contain magnesium, and the contact resistance greatly changed in the salt spray test. Sample No. 6 also had a large change in contact resistance due to the low magnesium content in the substrate. Sample No. In No. 7, since the magnesium content in the base material was too large, the solder wettability was deteriorated, and the contact resistance itself was increased because the oxide layer was thick.

DESCRIPTION OF SYMBOLS 1 Tin plating copper alloy terminal material 2 Base material 3 Copper tin alloy layer 4 Tin layer 5 Tin magnesium oxide layer 10 Terminal 11 Connection part 12 Electric wire 12a Core wire 12b Covering part 13 Core wire crimping part 14 Covering crimping part

Claims (3)

A copper tin alloy layer is formed on a base material made of a copper alloy, and a tin layer is formed on the copper tin alloy layer. Tin: 5 at% or more and 30 at% or less, magnesium A tin-plated copper alloy terminal material characterized in that a tin magnesium oxide layer containing 15 at% or more and 45 at% or less and the balance being oxygen is formed with a thickness of 2 nm or more and 15 nm or less in terms of SiO ₂ .   After laminating a copper plating layer and a tin plating layer in this order on a base material made of a copper alloy containing 0.5% by mass to 3% by mass of magnesium, the temperature is 235 ° C. or higher and 600 ° C. or lower for 5 seconds or longer 30 A method for producing a tin-plated copper alloy terminal material, wherein the tin-magnesium oxide layer is formed by performing heat treatment for a period of seconds or less and supplying an oxygen-containing gas to the surface at a temperature of 20 ° C to 80 ° C. A wire terminal part structure, wherein a terminal produced using the tin-plated copper alloy terminal material according to claim 1 is crimped to a terminal of a core wire of an electric wire made of aluminum or an aluminum alloy.

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