JP2507723B2 - Copper wire for signal transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a copper wire for signal transmission, which is used for inter-device wiring such as audio equipment, video equipment, computers and the like, wiring inside equipment, and the like.

[Conventional technology]

Conventionally, tough pitch (TPC) annealed copper wire is used as the copper wire for signal transmission, and oxygen-free copper (OFC) is used for higher-grade ones.
Annealed copper wire has been used. All of these are drawn and rolled after continuous casting and rolling such as SCR method and dip forming method.Since they undergo hot working, they have fine recrystallization and it is not possible to obtain excellent transmission efficiency. difficult. Generally, the signal transmission of a copper wire largely depends on the number of crystal grain boundaries existing in the longitudinal direction of the electric wire, that is, the signal transmission direction, and the layer of impurities such as Cu ₂ O and sulfide accumulated there. The reason for this is thought to be that the grain boundaries and the impurities accumulated there act as if they were capacitors with a very small capacitance, bringing in capacitance and detection. In other words, in order to improve the conduction efficiency, it is effective to reduce the amount of oxygen and the number of crystal grains, and recently the crystal grains of OFC copper wire were coarsened by heat treatment for some high-grade audio. After that, a hard copper wire in which crystal grains are oriented in the longitudinal direction by drawing is disclosed in JP-A-60-380.
No. 8 has been proposed.

[Problems to be solved by the invention]

However, although it is enlarging the crystal grains, technically, the diameter is about 1/5 to 1/3 of the wire diameter, for example 1.6 mm in diameter.
In the wire of No. 3, the grain size is limited to 0.3-5 mm, and it is still a polycrystal, and since the diameter is reduced by drawing in the cold, the transition in the copper wire Lattice defects such as density and atomic vacancies are increasing. Such lattice defects act similarly to the crystal grain boundaries and impurities accumulated there, and reduce the transmission efficiency.

Further, the conventional TPC copper wire is an ingot cast by using a cooling mold and is drawn after hot rolling, and has innumerable ingot defects on the surface and inside. That is, the surface has defects such as cracks and surface roughness caused by rubbing between the mold and the ingot, and the defects such as cracks and blowholes generated during solidification shrinkage tend to remain inside. As described above, such an internal defect is not preferable, and a surface defect is not preferable for a high frequency signal current flowing near the surface of the wire. When used as a twisted wire, the wires having surface defects come into contact with each other to form a complicated circuit, which causes phase difference and attenuation of signals.

[Means for solving problems]

As a result of various studies in view of this, the present invention has found that the signal transmission characteristics of the OFC copper wire are strongly related to the manufacturing method and the processing method thereof, and further studies have revealed that the signal transmission copper having excellent signal transmission characteristics. We have developed a wire that has a single crystal structure of oxygen free copper (OFC) or a unidirectional solidification structure in the longitudinal direction, and has an electrical conductivity of 100% or more or a tensile strength of 20 kg / mm ² or less. It is a feature.

That is, the present invention is a wire rod-shaped ingot having a single crystal structure of OFC or a unidirectionally solidified structure in the longitudinal direction or a plastic wire by a slight drawing or the like to make a copper wire for signal transmission, and its conductivity Is 100% IACS or more or the tensile strength is 20 kg / mm ² or less, it has extremely excellent signal transmission characteristics.

As a method for obtaining an OFC single crystal or a copper wire having a unidirectionally solidified structure in the longitudinal direction, a hot mold continuous casting method using a mold heated above the melting point of OFC, an ingot non-rotating casting method applying the Czochralski method, or The bridgman method may be used for casting, or slight plastic working may be applied to the obtained ingot, but the hot mold casting method is most preferable in consideration of ingot quality and productivity.

[Action]

The OFC single crystal structure or the copper wire of the longitudinal direction unidirectionally solidified structure is used for signal transmission, although the conventional material has undergone sufficient hot or cold working to make it a copper wire. This processing strain causes deterioration of the signal transmission characteristics, and in order to eliminate this, the ingot or the ingot is slightly plastically processed to form a copper wire. In addition, the conductivity of the copper wire is 100% IACS
The above or the tensile strength of 20 kg / mm ² or less means that the signal transmission characteristics when the OFC copper wire is used as a conductor as it is is that the value of conductivity is 100% IACS and the value of tensile strength is 20 kg. /
This is because the value changes remarkably at mm ² . That is, the signal attenuation becomes extremely small when the conductivity is 100% IACS or more or the tensile strength is 20 kg / mm ² or less.

The conductivity value of OFC copper wire usually has a positive correlation with the specific gravity value of the ingot. Because OFC copper wire contains a small amount of oxygen and hydrogen gas even if it is OFC, for example.
There are minute defects such as pinholes depending on the inappropriate solidification conditions. Therefore, when there are many minute defects, the specific gravity value decreases and the conductivity also decreases. The conductivity of the OFC ingot produced using a normal water-cooled mold is 99.8% IACS with good quality.
(However, the specific gravity value is about 8.935), and in order to obtain a conductivity of 100% IACS or more, it is necessary to form a unidirectionally solidified structure in the longitudinal direction. The reason is that in a unidirectionally solidified structure, there is no grain boundary that prevents the current from flowing in the direction of current flow, and during casting, oxygen, hydrogen gas, and other impurities are discharged from the solidification interface into the molten metal, causing defects. Is less likely to occur.

Also, the signal transmission characteristics of OFC copper wire unidirectionally solidified in the longitudinal direction, especially the factors that increase the amount of signal attenuation, are factors that uniformly increase the strength of the copper wire. Is used, the signal transmission characteristic becomes extremely good. As a factor that enhances the strength of the copper wire, the strain of the copper wire and the impurity element are the main factors. Conductivity is 100% I even if a slight plastic working is applied to
The tensile strength should be ACS or more and 20kg / mm ² or less.

Example 1 OFC was dissolved, and the amount of oxygen was 5 ppm by the continuous casting method using a heating mold.
A unidirectionally solidified ingot having a diameter of 1 mm was obtained. That is, as shown in FIG. 1, a graphite mold (2) having an inner diameter of 1 mm and an outer diameter of 30 mm was attached to the side wall of the casting furnace (1), and a heating device (3) in which a kanthal wire was wound around the inner surface of the mold (2). The inner surface of the mold (2) by OFC
Heat above the melting point of. The molten OFC (4) is introduced into the casting furnace (1), and the pinch roll (6) is cast by the mold (2).
The ingot (5) drawn out by is cooled by a water cooling device (7) provided in the vicinity of the outlet of the mold (2), and the ingot (5) is placed in the mold (2).
The molten metal in contact with was solidified continuously.

In this way, the casting speed was changed from 50 mm / min to 600 mm / min at intervals of 50 mm / min, for the copper wire made of the obtained ingot, the conductivity and the tensile strength were measured, and the casting speed and the conductivity were measured. 2 and the relationship between the casting speed and the tensile strength are shown in FIG. As can be seen from the figure, the higher the casting speed, the lower the conductivity and the higher the tensile strength. This is because as the casting speed is faster, the ingot is rapidly cooled, so that a large amount of thermal strain remains inside, and there is no time to allow the impurity elements in the molten metal to diffuse from the solidification interface into the molten metal, forcing it to form a solid solution. This is because
Therefore, in order to reduce this, the casting speed should be made as small as possible.

The signal attenuation characteristics of the obtained ingot were examined, and the relationship between conductivity and signal attenuation is shown in FIG. 4, and the relationship between tensile strength and signal attenuation is shown in FIG. As can be seen from the figure, the signal attenuation has a correlation with the conductivity and the tensile strength.The higher the conductivity and the lower the tensile strength, the smaller the signal attenuation.
In particular, it can be seen that the signal transmission copper wire of the present invention having a conductivity of 100% IACS or more or a tensile strength of 20 kg / mm ² or less has a small signal attenuation amount.

Example 2 OFC was dissolved and a directionally solidified ingot having a diameter of 1 mm and an oxygen amount of 3 ppm was obtained by a mold non-rotating casting method to which the Czochralski method was applied. That is, as shown in FIG. 5, a hole is provided in the furnace lid (8) of the casting furnace (1) for holding the molten metal (4) of OFC, and the cooling device (7 ') is lowered from the hole to remove the molten metal (1). After being set on the surface, the OFC copper rod (5 ') is inserted from above so as to be located at the center of the cooling device (7') and brought into contact with the molten metal surface. In this state, while blowing the N ₂ gas from the cooling device (7 ′) to cool the copper rod (5 ′), the copper rod (5 ′) is pulled up by the rotary air chuck (9), and the OFC ingot (5) having a −direction solidified structure
I got In the figure, (10) indicates a heat insulating material.

In this way, the ingot pulling speed (casting speed) is 50 mm / m
The electrical conductivity, tensile strength, and signal attenuation of the obtained ingot were measured by changing from in to 60 mm / min at an interval of 50 mm / min. As a result, almost the same result as in Example 1 was obtained.

Example 3 In Example 1 and Example 2, the casting speed was 200 mm / min.
With respect to the ingots cast as above, wire drawing was applied at a working rate of 0% to every 1%, and the tensile strength, the electrical conductivity, and the signal attenuation amount were measured. The results are shown in Table 1.

As is clear from Table 1, OFC single crystals or ingots with a unidirectional solidification structure in the longitudinal direction have a conductivity of 100% IACS or more or a tensile strength of 20k even if light processing is applied to them.
It can be seen that excellent signal transmission characteristics are exhibited at g / mm ² or less.

〔The invention's effect〕

Thus, the copper wire of the present invention has excellent signal transmission characteristics,
It is used not only for audio, for audio such as microphone code, but also for video such as video, CT scan, MRI, etc., as well as for internal wiring between devices of large computers, and other cable conductors for the purpose of signal transmission, It has a remarkable effect that the performance can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a heating mold continuous casting method, and FIG.
FIG. 3 is an explanatory view showing the relationship between the conductivity and the casting speed of a single wire made of OFC or a copper wire having a unidirectionally solidified structure, FIG. 3 is an explanatory view showing the relationship between the tensile strength and the casting speed, and FIG. FIG. 5 is an explanatory diagram showing the relationship between the signal attenuation amount and conductivity, FIG. 5 is an explanatory diagram showing the relationship between the signal attenuation amount and tensile strength, and FIG. 6 is an explanatory diagram showing an example of the mold non-rotating casting method. . 1. Casting furnace 2. Mold 3. Heating device 4. Molten metal 5. Ingot 5 '. Copper rod 6. Pinch roll 7,7 '. Cooling device 8. Furnace lid 9. Rotary air chuck 10. Insulation material

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akira Yamazaki 500 Kiyotaki-cho, Nikko-shi Furukawa Electric Co., Ltd. Nikko Denki Copper Works (56) References JP-A-61-163505 (JP, A) JP-A 62-286650 (JP, A) JP 62-136707 (JP, A) JP 63-144849 (JP, A)

Claims (1)

(57) [Claims] 1. A signal having a single crystal structure of oxygen-free copper or a unidirectionally solidified structure in the longitudinal direction and having a conductivity of 100% IACS or more or a tensile strength of 20 kg / mm ² or less. Copper wire for transmission.