JP2801355B2 - Nickel-plated copper wire and its manufacturing method - Google Patents

Description

The present invention relates to a nickel-plated copper wire and a method for manufacturing the same.
More specifically, the present invention relates to a nickel-plated copper wire having excellent corrosion resistance and good discoloration resistance when used for a lead wire of an electronic component or an electronic device, and a method of manufacturing the same.

(Prior Art) Silver-coated copper wires have been frequently used for lead wires of electronic components and electronic devices because of their good solderability. However, this lead is expensive because it is coated with silver.

For this reason, in recent years, lead wires in which the surface of a core wire made of copper or a copper alloy is plated with nickel instead of silver are widely used. This nickel-plated copper wire not only exhibits the properties such as good conductivity, good workability, and heat resistance of copper or copper alloy as a constituent material of the core wire, but also has the corrosion resistance peculiar to nickel. And has the advantage of being cheaper than silver.

(Problems to be Solved by the Invention) By the way, for example, when a silicon chip is soldered at the time of manufacturing a diode using the above-described nickel-plated copper wire, the nickel-plated copper wire becomes 300 to 400 in this step. It is exposed to a high temperature environment of about 1 hour of soldering at a temperature of 200 ° C. and curing for 16 hours at a temperature of 200 to 250 ° C.

However, when the nickel-plated copper wire is exposed to the high-temperature environment as described above, the copper component constituting the core wire diffuses through the nickel-plated layer toward the surface. Has a problem in that it is discolored and its corrosion resistance is reduced.

An object of the present invention is to solve the above-mentioned problems, and to provide a method for producing a nickel-plated copper wire with less discoloration of the surface even under a high-temperature environment, and hence less decrease in corrosion resistance.

(Means for Solving the Problems) The present inventors have conducted intensive studies in order to achieve the above-mentioned object. As a result, when the nickel plating layer is composed of coarse crystal grains of nickel, the coarse crystal grains have no pin. It has been found that since there are few holes and grain boundaries, diffusion of the copper component of the core wire to the surface is suppressed, and as a result, surface discoloration and deterioration of corrosion resistance are suppressed.

The nickel-plated copper wire of the present invention is also considered in view of the fact that the crystal grain size of nickel in the nickel-plated layer is determined by the crystal grain size of copper of the core wire as the base. We have developed a manufacturing method.

That is, the nickel-plated copper wire of the present invention is made of copper or a copper alloy, and has a core wire having a crystal grain size of copper of 5.0 μm or more, and a thickness of 0.1 to 5.0, which is formed by electroplating the surface of the core wire. and a nickel plating layer having a thickness of μm, and a method for producing the same is characterized in that a core wire made of drawn copper or a copper alloy is subjected to an annealing treatment to adjust the crystal grain size of copper to 5.0 μm or more. Then, electroplating is performed on the surface of the core wire to form a nickel plating layer having a thickness of 0.1 to 5.0 μm.

First, the core of the nickel-plated copper wire of the present invention is made of copper or a copper alloy. Specifically, tough pitch copper (TP
C), Cu-0.1% Ag, Cu-0.15% Sn, and the like. Also,
An EF wire formed by cladding copper on the surface of a steel wire may be used.

In this core wire, the crystal grain size of copper is adjusted to a size of 5.0 μm or more. When the crystal grain size is smaller than 5.0 μm, when a nickel plating layer is formed on the surface of the core wire by an electroplating method described later, the nickel crystal grain size follows the copper crystal grain size. Therefore, the crystal grain size of nickel also becomes small, and as a result, many pinholes and grain boundaries are present in the nickel plating layer, and the effect of the nickel plating layer to prevent copper from diffusing from the core wire is reduced. It is.

The thickness of the nickel plating layer formed on the surface of the core wire is 0.
It is set to 1 to 5.0 μm. If the thickness is less than 0.1 μm, the resulting nickel-plated copper wire will have insufficient discoloration resistance and corrosion resistance, and even if the thickness is greater than 5.0 μm, nickel-coarse crystals will not be formed in the plating layer. It is. The preferred thickness of the nickel plating layer is 0.
It is about 5 to 3.0 μm.

The nickel-plated copper wire of the present invention is manufactured as follows.

First, the core wire drawn to a predetermined wire diameter is annealed to adjust the crystal grain size of copper to a size of 5.0 μm or more.

In the core wire that has been subjected to the wire drawing, the crystal grain size of copper is generally small due to the surface reduction applied during the wire drawing.

Therefore, by performing an annealing treatment on this core wire,
The copper crystal grains are coarsened and the crystal grain size is adjusted to 5.0 μm or more.

The conditions of the annealing treatment are appropriately selected depending on the reduction rate of the area of the drawn core wire and the size of the resulting copper crystal grain size. Usually, the annealing temperature is 300 ° C. or more and the annealing time is 0.1 to 25.
Selected within the range of 0 minutes.

Next, nickel plating is applied to the annealed core wire by an electroplating method.

The conditions of the electroplating at this time, for example, the composition of the plating bath to be used, the bath temperature, the current density, etc., may be the same as the conditions conventionally used for nickel plating. At this time, the thickness of the nickel plating layer is adjusted to a range of 0.1 to 5.0 μm by appropriately selecting a plating time and the like in addition to the above conditions.

In the course of the electroplating, the nickel plating layer grows along the copper crystal grains of the core wire as the base. Therefore, since the grain size of the copper crystal is 5.0 μm or more, the crystal grains of nickel constituting the nickel plating layer are coarsened, and the effect of preventing copper diffusion is increased.

(Examples of the Invention) Examples 1 to 9 and Comparative Examples 1 to 3 The materials shown in Table 1 and a wire diameter having a crystal grain diameter of copper of 0.1 were used.
An 8 mm core wire was subjected to an annealing treatment in an N ₂ atmosphere furnace under the conditions shown in Table 1 to adjust the respective copper crystal grain sizes to the sizes shown in Table 1.

Next, each core wire was subjected to electroplating under the following conditions to form a nickel plating layer having a thickness shown in Table 1.

Bath composition: Nickel sulfamate 300 g /, Nickel chloride 30 g /, Boric acid 30 g / Bath temperature: 55 ° C Current density: 5 A / dm ^{2 The} obtained nickel-plated copper wires were evaluated according to the following specifications.

Copper diffusion amount: Nickel-plated copper wire is subjected to heat treatment for 1 hour in a hydrogen atmosphere at 350 ° C, and then to heat treatment for 16 hours in an air atmosphere at 250 ° C, from the surface (the surface of the nickel plating layer). The amount of copper in the plating layer up to a depth of 100 mm was quantified. The smaller the quantitative value, the more
This shows that the nickel plating layer has good copper diffusion preventing ability.

Corrosion resistance: heat-treated nickel-plated copper wire under the same conditions as those used for copper diffusion measurement, immersed in a 15% hydrochloric acid solution and dried, and then heat-treated at 200 ° C in an air atmosphere for 10 hours. The corrosion area generated was calculated as the ratio (%) of the area of the corroded portion to the entire surface of the wire.

The smaller the value, the better the corrosion resistance.

Workability: Twisting test was performed 40 times in the forward direction and 30 times in the reverse direction for a 50 mm length of the nickel-plated copper wire, and the soundness of the nickel plating was evaluated.

：: No peeling of nickel plating, ×: Peeling of nickel plating.

 The above results are collectively shown in Table 1.

(Effects of the Invention) As is clear from the above description, the nickel-plated copper wire of the present invention has a large copper crystal grain size of the core wire, so that the nickel crystal grain size of the nickel plating layer formed on the core wire surface also becomes large. As a result, even if the copper component of the core wire attempts to diffuse to the surface due to exposure to a high-temperature environment, the nickel plating layer suppresses the diffusion, suppressing discoloration of the surface and improving corrosion resistance. Therefore, the nickel-plated copper wire of the present invention
Its industrial value is great as a lead wire for electronic components and electronic equipment.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C25D 5/00-7/12

Claims (2)

(57) [Claims] Claims: 1. A copper or copper alloy having a crystal grain size of copper.
A nickel-plated copper wire comprising: a core wire having a thickness of 5.0 μm or more; and a nickel plating layer having a thickness of 0.1 to 5.0 μm and formed on the surface of the core wire by electroplating. 2. A core wire made of a drawn copper or copper alloy is subjected to an annealing treatment to adjust the crystal grain size of copper to 5.0 μm or more, and then the surface of said core wire is electroplated to a thickness of 0.1 μm. A method for producing a nickel-plated copper wire, comprising forming a nickel-plated layer having a thickness of 5.0 μm.