JP2012124025A - Plated copper wire and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plated copper wire which further suppresses growth of an intermetallic compound layer high in brittleness between Sn-based plating and a conductor than before while suppressing reduction in conductivity of the conductor as much as possible, and prevents deterioration of bending resistance characteristics and bonding strength when soldered even held in an environment at a high temperature.SOLUTION: The plated copper wire has a copper-zinc alloy layer containing zinc dispersed in copper in the outer periphery of a core material containing copper as a main component, and is provided with a plating layer containing tin as the main component in the outer periphery of the copper-zinc alloy layer. The average concentration of zinc in the copper-zinc alloy layer is 35 mass% or more, and thickness of the copper-zinc alloy layer is 0.1 μm or more.

Description

  The present invention relates to a plating-coated copper wire that does not deteriorate its bending resistance even in a high-temperature environment and does not decrease connection strength even in solder connection, and a method for manufacturing the same.

  There are wiring rationalization products such as a power supply board (PSB) and a bus bar in which an insulating coating layer is provided on a conductor plated with Cu or Sn and further processed into a three-dimensional structure. In addition, as wiring components that are used in movable parts and require high bending resistance, there are various solder plated conductors such as in-vehicle flexible flat cables (FFC) and high-frequency coaxial cables. The conductor used for these applications is required to be highly conductive in order to propagate signals and power.

  The conductors used for the above-described wiring components are generally made of a Cu-based material, and these conductors are often subjected to pure Sn plating or solder plating. These Sn-based surface treatments have the effect of reducing the contact resistance in connector connection while exhibiting the anticorrosive effect of the conductor. Further, in the case of solder connection with a substrate or the like, there is an effect of improving the wettability by melting the conductor plating.

Conventionally, Sn—Pb solder is often used as the Sn-based surface treatment. However, in accordance with Pb regulation, pure Sn-based, Sn-Ag-based, Sn-Ag-Cu-based, Sn-Cu-based Pb, etc. Free solder plating is used. Conventionally, for example, in Sn-based plated conductors used in flat cables, Cu and Sn react at the interface between the conductor and the Sn-based plated layer to cause Cu ₃ Sn (ε phase) or Cu ₆ Sn ₅ (η phase). ) Cu-Sn based intermetallic compound layer, and this intermetallic compound layer is a hard and brittle layer, it is known that the mechanical properties (for example, bending resistance) of the Sn based plated conductor are deteriorated. The thickness of the intermetallic compound layer is controlled by adjusting the final annealing conditions in the manufacturing process of the Sn-based plated conductor (for example, Patent Document 1), and the Sn-based plated conductor has bending resistance characteristics. Has been proposed.

  On the other hand, in the technical field of Sn-based plated conductors in recent years, even if the thickness of the intermetallic compound layer is controlled in the manufacturing process of the Sn-based plated conductors, Problems have been reported to occur.

JP 2003-86024 A Japanese Patent Laid-Open No. 1-262092 JP 2008-221333 A

When the Sn-based plating conductor is used in a vehicle, or in a high-current wiring member such as HEV (Hybrid Electric Vehicle) or EV (Electric Vehicle), or in a high-temperature environment such as direct sunlight, the environmental temperature is Sn-based plating. Cu ₃ Sn or Cu ₆ Sn _{5 at} the interface between the conductor and the Sn-based plating layer due to solid phase diffusion between Sn in the Sn-based plating and the Cu-based material constituting the conductor even below the melting point of An Sn-based intermetallic compound layer is formed. At this time, the higher the heat retention temperature, that is, the use environment temperature of the product, the solid phase diffusion proceeds, and the intermetallic compound layer grows thicker.

The intermetallic compound layer is generally brittle, the fracture toughness value of Cu ₃ Sn is 1.7 (MPa · m ^1/2 ), and the Cu ₆ Sn ₅ is 1.4 (MPa · m ^1/2 ). The fracture toughness value of 10 ² to 10 ³ (MPa · m ^1/2 ) is extremely small. Therefore, when the intermetallic compound layer grows thick between the solder and the conductor, the intermetallic compound layer or the interface between the intermetallic compound layer and the solder or conductor is likely to break, and the bending resistance of the conductor deteriorates. Alternatively, there is a problem that the reliability of the solder connection portion is remarkably lowered. Therefore, a new material or structure that suppresses the growth of the intermetallic compound layer under the usage environment of the Sn-based plated conductor has been demanded.

As a method for suppressing the growth of Cu ₃ Sn, Patent Document 2 discloses that a coating layer made of Zn is added to the surface of a member to be joined made of 0.3 to 3 mass% of solder or made of a Cu-based alloy. It has been proposed to form and bond with Sn alloy solder. By adding Zn to the solder, a Cu—Zn—Sn intermetallic compound layer is formed between the solder and the Cu alloy, thereby suppressing the growth of the Cu—Sn intermetallic compound layer.

  Patent Document 3 proposes a structure having a bonding layer made of a Zn alloy containing 0.1 to 30% of Zn between a solder ball and a substrate. It is said that the growth of the Cu—Sn intermetallic compound layer can be suppressed by intervening Zn in the interface reaction.

  In Patent Document 2, since Zn is added to the entire solder, Zn intervening in the interface reaction between the solder and the Cu-based alloy joined member is a part of the added Zn, and the Cu—Sn-based intermetallic compound layer The degree of growth suppression is small. In addition, a part of Zn that has not intervened in the interface reaction forms a thick Zn oxide film on the surface of the solder plating, so that the wettability is impaired in subsequent solder connection applications. Further, even when a coating layer made of Zn is formed on the surface of the member to be joined, during soldering, since Zn diffuses instantaneously in the molten solder, it is similar to the case where Zn is added to the solder in advance. Zn cannot be effectively intervened in the interfacial reaction.

  Moreover, in patent document 3, although growth of a Cu-Sn type | system | group intermetallic compound layer can be effectively suppressed by making a bonding layer into Zn alloys, such as a Cu-Zn layer, Zn density | concentration in Zn alloy is 0.1-0.1. Since it is as low as 30%, the problem is that the degree of growth inhibition of the Cu—Sn intermetallic compound layer is small. In addition, when the entire conductor is made of a Cu—Zn alloy as in Patent Document 3, the conductivity of the conductor is remarkably lowered, so that it is used for the wiring rationalization product, the flexible flat cable, and the high-frequency coaxial cable. It cannot be used as a conductor.

  Accordingly, an object of the present invention is to further suppress the growth of a highly brittle intermetallic compound layer between the Sn-based plating and the conductor as much as possible while suppressing a decrease in the conductivity of the conductor as much as possible, and to withstand the high temperature holding environment. An object of the present invention is to provide a plating-coated copper wire and a method for manufacturing the same, in which bending characteristics and soldering strength when soldering are not deteriorated.

  Invented to achieve this object, the present invention has a copper-zinc alloy layer in which zinc is diffused in copper on the outer periphery of a core mainly composed of copper, and on the outer periphery of the copper-zinc alloy layer. A plated coated copper wire comprising a tin-based plating layer, wherein the average zinc concentration in the copper-zinc alloy layer is 35 mass% or more, and the thickness of the copper-zinc alloy layer is 0.1 μm or more It is a certain plating coated copper wire.

  When the cross-sectional area of the core material is A and the cross-sectional area of the copper-zinc alloy layer is B, the value of B / A is preferably 0.5 or less.

  The present invention also includes a step of forming a zinc-coated copper wire for forming a zinc layer on the surface of a conductor mainly composed of copper, and heat-treating the zinc-coated copper wire to diffuse zinc into the copper. A method for producing a plated coated copper wire, comprising: a step of forming a copper-zinc alloy layer on an outer periphery of a core material as a main component; and a step of forming a plating layer by performing tin plating on the copper-zinc alloy layer And the average zinc concentration in the said copper-zinc alloy layer is 35 mass% or more, It is a manufacturing method of the plating covering copper wire whose thickness of the said copper-zinc alloy layer is 0.1 micrometer or more.

  When the cross-sectional area of the core material is A and the cross-sectional area of the copper-zinc alloy layer is B, the value of B / A is preferably 0.5 or less.

  According to the present invention, the growth of a highly brittle intermetallic compound layer between the Sn-based plating and the conductor is further suppressed as compared with the conventional one while suppressing the decrease in the conductivity of the conductor as much as possible, and the bending resistance is maintained even in a high temperature holding environment. Further, it is possible to provide a plating-coated copper wire and a method for producing the same without causing deterioration in bonding strength when soldering is performed.

It is a figure which shows the cross-sectional photograph of the surface vicinity of the plating coating copper wire of this invention, and a line analysis position. It is a figure which shows the line analysis result in FIG. It is a figure which shows the observation result by the optical microscope of the intermetallic compound layer after 150 degreeC and 1000 hr holding | maintenance in the solder / Cu-Zn layer interface of the plating coating copper wire of this invention. It is a figure which shows the observation result by the optical microscope of the intermetallic compound layer after 150 degreeC and 1000 hr holding | maintenance in the solder / Cu interface of the conventional plating coating copper wire. It is a figure which shows the growth behavior of the intermetallic compound layer in 150 degreeC of this invention and the conventional plating coating copper wire.

  Hereinafter, preferred embodiments of the present invention will be described.

  As a result of studying the average zinc concentration (average Zn concentration) in the copper-zinc alloy layer (Cu-Zn layer) disposed at the conductor and plating interface by the present inventors, the lower limit value of the average Zn concentration is 35 mass% or more, preferably By setting the thickness of the Cu—Zn layer to 0.1 μm or more, the growth of the intermetallic compound layer at the interface when used in a high temperature environment is hardly seen, and the growth is suppressed. It was found that the effect is high.

  The reason why the average Zn concentration in the Cu—Zn layer is defined as 35 mass% or more is that when the average Zn concentration is less than 35 mass%, the growth of the intermetallic compound layer can be suppressed to some extent as compared with the case where Zn is not contained. However, the thickness of the intermetallic compound layer grows to 2 μm or more, and the reason why the thickness of the Cu—Zn layer is defined as 0.1 μm or more is that the thickness of the Cu—Zn layer is less than 0.1 μm. In some cases, the growth of the intermetallic compound layer can be suppressed to some extent as compared with the case where Zn is not contained, but the thickness of the intermetallic compound layer grows to 2 μm or more.

  The present invention also provides a Cu-Zn layer after heat treatment of a zinc-coated copper wire to form a Cu-Zn layer obtained by diffusing Zn into Cu on the outer periphery of a core material mainly composed of Cu. Since the plating layer is formed on the surface, the amount of Zn component melting in the plating layer can be extremely reduced, and the solder wettability of the plating layer is reduced due to the Zn oxide film on the surface of the plating layer. Can be suppressed.

  Further, when the cross-sectional area of the core material is A and the cross-sectional area of the Cu—Zn layer is B, the value of B / A is preferably 0.5 or less. This is because when the value of B / A exceeds 0.5, the conductivity of the plating-coated copper wire is lowered.

  Moreover, it is desirable that the upper limit value of the average Zn concentration is 98 mass% or less. The reason is that when a conductor having a Cu—Zn layer with an average Zn concentration exceeding 98 mass% is plated, Zn diffuses instantaneously in the plating layer, and the diffused Zn forms a Zn oxide film on the surface of the plating layer. The reason for this is that the wettability may be impaired in subsequent solder-connected applications.

  Further, the upper limit value of the thickness of the Cu—Zn layer is desirably 20 μm or less. The reason is that since the Cu—Zn layer has low conductivity, if the thickness exceeds 20 μm, the conductivity of the plating-coated copper wire is remarkably lowered. For example, when a current of 10 MHz is passed, the skin depth (depth from the conductor surface through which the current flows) is about 21 μm, which is considered to have a large influence in the high-frequency region.

  Further, when the cross-sectional area of the core material is A and the cross-sectional area of the Cu—Zn layer is B, the value of B / A is preferably 0.0005 or more. The reason is that when the above-mentioned application is taken into consideration, if the value of B / A is less than 0.0005, the effect of suppressing the growth of the intermetallic compound layer is small.

  When manufacturing a plated coated copper wire having such a configuration, the Cu—Zn layer disposed at the conductor and plating interface can be formed as a Cu—Zn layer by sputtering or electroplating, but as a Zn single layer, A method of forming a Cu—Zn layer by interdiffusion with Cu of the conductor by heat treatment after formation is preferable because it is simple and economical, and it is easy to adjust the Zn concentration. In addition to the plating method, a sputtering method, a cladding method, or the like can be applied to the formation of the Zn single layer.

  According to the present invention described above, the growth of the highly brittle intermetallic compound layer between the Sn-based plating and the conductor is further suppressed as compared with the conventional one while suppressing the decrease in the conductivity of the conductor as much as possible. It is possible to provide a plating-coated copper wire and a method for producing the same without causing deterioration in bending resistance and bonding strength when soldered.

  Examples 1 to 10 of the present invention, Conventional Examples 1 and 2 and Comparative Examples 1 to 6 are shown below.

Example 1
A Zn layer having a thickness of 4 μm was formed on a pure Cu (tough pitch copper; TPC) round wire of φ0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. FIG. 1 and FIG. 2 show an electron microscope image and a line analysis result near the surface of the cross section of the obtained zinc-coated copper wire. From these figures, it was confirmed that a Cu—Zn layer having an average Zn concentration of 45 to 65 mass% was formed on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 2)
A Zn layer having a thickness of 4 μm was formed on a pure Cu (oxygen-free copper: OFC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Similarly, at this time, it was confirmed that a Cu—Zn layer having an average Zn concentration of 45 to 65 mass% was formed on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 3)
A Zn layer having a thickness of 2 μm was formed on a pure Cu (TPC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

Example 4
A Zn layer having a thickness of 5.4 μm was formed on a pure Cu (TPC) round wire with a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 5)
A Zn layer having a thickness of 0.08 μm was formed on a pure Cu (TPC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 6)
A 0.08 μm thick Zn layer was formed on a pure Cu (TPC) round wire of φ0.17 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 7)
A Zn layer having a thickness of 4 μm was formed on a pure Cu (TPC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 8)
A Zn layer having a thickness of 8 μm was formed on a pure Cu (TPC) round wire with a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

Example 9
A Zn layer having a thickness of 10 μm was formed by electrolytic plating on a pure Cu (TPC) round wire having a diameter of 0.15 mm. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Example 10)
A 17 μm thick Zn layer was formed on a pure Cu (TPC) round wire with a diameter of 0.178 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Conventional example 1)
A lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm is formed by hot dipping on a φ0.1 mm pure Cu (TPC) round wire without a Cu—Zn layer. did.

(Conventional example 2)
A leaded solder plating layer (plating composition: Sn-37 mass% Pb) having a thickness of 20 μm was formed on a pure Cu (TPC) round wire of φ0.1 mm without a Cu—Zn layer by hot dipping.

(Comparative Example 1)
A Zn layer having a thickness of 4 μm was formed on a pure Cu (TPC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a leaded solder plating layer (plating composition: Sn-37 mass% Pb) having a thickness of 20 μm was formed by hot dipping.

(Comparative Example 2)
A Zn layer having a thickness of 1 μm was formed on a pure Cu (TPC) round wire with a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Comparative Example 3)
A Zn layer having a thickness of 5.7 μm was formed on a pure Cu (TPC) round wire with a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Comparative Example 4)
A Zn layer having a thickness of 0.04 μm was formed on a pure Cu (TPC) round wire with a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Comparative Example 5)
A Zn layer having a thickness of 10 μm was formed on a pure Cu (TPC) round wire having a diameter of 0.1 mm by electroplating. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

(Comparative Example 6)
A Zn layer having a thickness of 17 μm was formed by electroplating on a pure Cu (TPC) round wire having a diameter of 0.1 mm. Thereafter, Cu and Zn were mutually diffused by an electric annealing heat treatment to form a Cu—Zn layer on the surface of the pure Cu round wire. Next, a lead-free solder plating layer (plating composition: Sn-3.0 mass% Ag-0.5 mass% Cu) having a thickness of 20 μm was formed by hot dipping.

  The plating-coated copper wires formed in Examples 1 to 10, Conventional Examples 1 and 2 and Comparative Examples 1 to 6 are held at a constant temperature bath set at 150 ° C. for 1000 hours for various times, and formed at the conductor and plating interface. The state of the intermetallic compound layer was observed by a cross section with an optical microscope, and the thickness was measured by the area method. FIGS. 3 and 4 show enlarged cross-sectional photographs of the plating / conductor interface of Example 1 and Conventional Example 1 after holding at 150 ° C. × 1000 hr, respectively. From these figures, it is clear that the thickness of the intermetallic compound layer of Example 1 is significantly suppressed as compared with Conventional Example 1.

  Similarly, the growth behavior (thickness change) of the intermetallic compound layer of Example 1 and Conventional Example 1 in a 150 ° C. environment is quantified and the result of comparison is shown in FIG. It was confirmed that the thickness of the intermetallic compound layer of Example 1 after holding at 150 ° C. × 1000 hr was 2 μm or less, and could be suppressed to 1/3 or less of about 7 μm of Conventional Example 1.

  Table 1 shows the results of comparative evaluation of the thickness of the intermetallic compound layer after holding the core material, the average Zn concentration of the Cu—Zn layer, the thickness of the Cu—Zn layer, and the kind of solder, and holding at 150 ° C. for 1000 hours. Shown in

Here, the average Zn concentration is obtained by integrating the Zn concentration in the Cu—Zn layer by the thickness and dividing by the thickness of the Cu—Zn layer. For example, in the case of FIG. 2, it can obtain | require as follows.
Average Zn concentration in FIG. 2 = (60% × 3.5 μm + 50% × 2 μm + 25% × 0.5 μm) / 6 μm = 54%

  First, with respect to the average Zn concentration of the Cu—Zn layer, in Examples 1 to 4 in the range of 35 mass% or more, the growth of the intermetallic compound layer was slow, and all were 2 μm or less. On the other hand, in the case of Comparative Example 2 in which the average Zn concentration is 10 mass%, although the effect of suppressing the growth of the intermetallic compound layer is recognized, the growth of the intermetallic compound layer is fast and the thickness is 4.5 μm, which is larger than 2 μm. It was higher. That is, it can be determined that the average Zn concentration of the Cu—Zn layer is appropriate to be 35 mass% or more. As a cause of this, the present inventors believe that the Cu—Zn alloy is related to having a solid solubility limit of Zn up to 35 mass% Zn, and the metal is above 35 mass% Zn exceeding the solid solubility limit of Zn. It is said that the effect of suppressing intermetallic layer growth is high. For that reason, the average Zn concentration is more preferably 38 mass% or more which certainly exceeds the solid solubility limit. Moreover, when the Zn density | concentration in the outermost surface after the heat processing in an Example was measured, it was 35-100 mass%. In all the examples, the Cu—Zn layer was a diffusion layer in which the Zn concentration decreased from the outermost surface toward the inside.

  Next, regarding the type of solder, Examples 1 and 2 in which a Cu—Zn layer is provided between the plating layer and the conductor and lead-free solder is used are 150 ° C. × 1000 hr regardless of the type of conductor such as TPC and OFC. It was found that the thickness of the intermetallic compound layer can be suppressed to 2 μm or less even after the holding. On the other hand, in Conventional Example 2 and Comparative Example 1 using leaded solder as the plating layer, the thickness of the intermetallic compound layer after holding at 150 ° C. × 1000 hr was about 9.5 μm and 8 μm, respectively. In comparison, it was found that the growth of the intermetallic compound layer was large. That is, in the case of leaded solder, it was found that the effect of suppressing the growth of the intermetallic compound layer by the Cu—Zn layer was smaller than that of the lead-free solder.

  Next, in order to compare the bending resistance of Example 1 and Conventional Example 1 after holding at 150 ° C. × 1000 hr, R = 15 mm, 90 ° left / right bending test was performed, and the number of bending until the conductor broke was investigated. The results are shown in Table 2.

  It was confirmed that Example 1 of the present invention had a bending resistance of 1.5 times or more compared to Conventional Example 1.

  Table 3 shows the results of evaluating the sample after being held at 150 ° C. × 1000 hr by changing the thickness of the Cu—Zn layer and the Cu—Zn / Cu cross-sectional area ratio. In Examples and Comparative Examples, the value of B / A when the thickness of the Cu—Zn layer, the average Zn concentration, the cross-sectional area of the core material is A, and the cross-sectional area of the Cu—Zn layer is B is Zn The thickness is adjusted by a known method such as changing the layer thickness and heat treatment conditions.

  Regarding the electrical conductivity, based on the electrical conductivity of a sample having no Cu—Zn layer, a sample whose value decreased by 1% or more was evaluated as “x”, and a sample having a lower value was evaluated as “◯”. As a result, regardless of the size of the conductor, for Examples 5 to 10 in which the thickness of the Cu—Zn layer was 0.1 μm or more, the thickness of the intermetallic compound layer was 2 μm or less. In Comparative Example 4 in which the Cu—Zn layer was less than 1 μm, the effect of suppressing the growth of the intermetallic compound layer was not obtained. Further, in Comparative Examples 5 and 6 in which the Cu—Zn / Cu cross-sectional area ratio exceeded 0.5, the growth of the intermetallic compound layer was small, but the conductivity was reduced. That is, in order to combine growth suppression of the intermetallic compound layer and high conductivity, the thickness of the Cu—Zn layer is required to be 0.1 μm or more, and the Cu—Zn / Cu cross-sectional area ratio is 0.5 or less. Is preferred.

  In Examples 1 to 10 according to the present invention, the Zn layer is preliminarily formed as a Cu—Zn layer by heating before the solder plating treatment, so that Zn hardly dissolves during the plating during the solder plating treatment. Therefore, the oxide film formed on the plating surface is as thin as 30 nm or less, and the wettability is not impaired in the subsequent solder connection application.

  As described above, according to the present invention, the growth of the intermetallic compound layer at the plating / conductor interface at high temperature holding can be suppressed, the bending resistance characteristic of the conductor is not deteriorated, and long-term reliability can be obtained even in the solder connection portion. I understand that. By this effect, the product to which the present invention is applied can be used in a high temperature environment.

  Although TPC and OFC are shown as the core material of the examples, the present invention is not limited to TPC and OFC, and can be applied to any Cu and Cu alloy that forms a Cu-Zn compound. As long as the above-described decrease in conductivity is not affected, the Cu alloy type is, for example, one or more selected from Mg, Zr, Ti, Nb, Ca, V, Ni, and Mn. A so-called dilute Cu alloy containing an additive element of 100 mass ppm or less may be used.

  The material of the plating layer is not limited to Sn—Ag—Cu plating, and Pb-free solder plating not containing Pb such as pure Sn, Sn—Ag, or Sn—Cu can be used.

  The shape of the conductor is not particularly limited, and may be a rectangular shape or a round cross section.

  In this example, it is considered that there is almost no diffusion of Zn to the plating layer side. However, as long as the effect of the present invention is not adversely affected, it does not exclude an aspect in which Zn diffuses to the plating layer side. .

Claims (4)

A plating-coated copper wire having a copper-zinc alloy layer in which zinc is diffused in copper on the outer periphery of a core material mainly composed of copper, and a plating layer mainly composed of tin on the outer periphery of the copper-zinc alloy layer Because
The average zinc concentration in the copper-zinc alloy layer is 35 mass% or more,
A plating-coated copper wire, wherein the copper-zinc alloy layer has a thickness of 0.1 μm or more.   2. The plated coated copper according to claim 1, wherein a value of B / A is 0.5 or less, where A is a cross-sectional area of the core material and B is a cross-sectional area of the copper-zinc alloy layer. line. Forming a zinc-coated copper wire for forming a zinc layer on the surface of a conductor mainly composed of copper;
Heat-treating the zinc-coated copper wire to diffuse zinc into the copper to form a copper-zinc alloy layer on the outer periphery of the core composed mainly of copper;
A method for producing a plated coated copper wire comprising a step of performing tin plating on the copper-zinc alloy layer to form a plating layer,
The average zinc concentration in the copper-zinc alloy layer is 35 mass% or more,
A method for producing a plating-coated copper wire, wherein the copper-zinc alloy layer has a thickness of 0.1 μm or more.   The plating-coated copper according to claim 3, wherein a value of B / A is 0.5 or less, where A is a cross-sectional area of the core material and B is a cross-sectional area of the copper-zinc alloy layer. Wire manufacturing method.