JP2001157925A - Metal hollow body for electric discharge machining, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a super-fine metal hollow body forming the electrode and its manufacturing method, and realize the super-fine drilling by the characteristic of an improved electrode without using any complicated apparatus in the prior art. SOLUTION: A plurality of wires formed of a first metal 3 are spirally twisted to form a hollow structure of a super-fine metal hollow body 10 for the electric discharge machining, a second metal 2 is welded in a spiral recess 5 formed between at least the wires adjacent to each other, and the melting point of the second metal 2 is lower than the melting point of the first metal 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal hollow body for an electrode, which can be used for electric discharge machining and which can form an extremely fine hole.

[0002]

2. Description of the Related Art In conventional pore discharge machining, a pulsed arc discharge is induced in a minute gap between an electrode and a work in a dielectric liquid to bore the work. Φ
A hole diameter of about 0.1 to 3.0 mm was perforated. For the electrodes, brass or copper pipes through which a working fluid that increases the current density and discharges decomposition gas and processing chips while cooling the work is passed are used.

[0003] Japanese Patent Application Laid-Open No. 2-30435 proposes a conventional technique relating to a means for supplying a working fluid around an electrode. FIG. 9 shows a case where a metal pipe is used as an electrode.
FIG. 10 uses a metal wire as an electrode. In FIG. 9, reference numeral 50 denotes a workpiece, in which a metal pipe 52 as an electrode is drilled while being lowered into a fine hole 51 partially processed. The working fluid A ₁ is sent from above the hole of the metal pipe 52 to cool the work 50, and the decomposition gas and the processing dust 53 are discharged from the mouth of the work 50.
It is discharged as working fluid A ₂ with.

If a finer hole is required than in FIG. 9, a metal wire 54 is used as an electrode as shown in FIG. Then, the working liquid A ₃ is injected from the outer periphery of the metal wire 54 via the nozzle 55. With such simple means, complete discharge of the decomposition gas and the processing waste 53 cannot be expected, so the apparatus 100 shown in FIG. 11 has been proposed.

In FIG. 11, a metal wire 54 for perforating a workpiece 50 is guided by an electrode guide 101 and rotates as shown by an arrow B or slides up and down as shown by an arrow C. The lower surface of the pressure vessel 102 supporting the electrode guide 101
The processing liquid is sealed by the liquid sealing member 103 in contact with the work 50. The nozzle 55 for ejecting the working fluid is provided with the pressure vessel 10
The pressurized working fluid fixed to the second wall fills around the metal wires 54 in the fine holes 51, and discharges decomposition gas and processing waste 53 to the outside through the gas vent holes 104. Reference numeral 105 denotes a cover for preventing the decomposition gas and the processing dust 53 from scattering. Reference numeral 106 denotes an arm extending from the base 107, and moves while holding the pressure vessel 102 when piercing the plurality of pores 51.

According to this prior art, since the pore processing is performed in a high-pressure environment of the pressure vessel, the size of the generated gas is reduced, while the immersion input of the working fluid into the pores is increased. As a result, it is described that the working fluid can be smoothly fed into the pores, and that the cooling of the discharge part and the discharge of the processing waste and gas are improved.

[0007]

However, in recent years, as semiconductor parts and electronic parts have become higher in density and smaller in size, start holes for wire electric discharge machining of press punching dies represented by IC lead frames have become more precise. Extremely fine hole processing is required. In other words, high accuracy is required for the shape and straightness of the start hole and the difference in hole diameter between the inlet and the outlet.

Conventionally, a Cu pipe having an outer diameter of 0.08 mm has been used for processing an extremely fine start hole, but there have been various problems described later. Since Cu itself has low rigidity, if a workpiece made of a cemented carbide is drilled while being discharged, it is easily bent in the hole. Further, in the process of drilling a through hole in a thick plate work, the discharge of the Cu pipe due to electric discharge was large, the machining efficiency was poor, and there was also a problem in the straightness of the hole. Therefore, the present invention proposes a structure of an ultra-fine metal hollow body to be an electrode and a method of manufacturing the same, and an ultra-fine hole can be obtained without using a complicated device shown in the prior art due to the improved characteristics of the electrode according to the present invention. Realize processing.

[0009]

As a structure of a metal hollow body for electric discharge machining, a plurality of wires made of a first metal are helically twisted to be hollow, and formed at least between adjacent wires. A second metal is welded to the spiral depression, and a metal having a melting point lower than that of the first metal is used.

[0010] The first metal is Mo, W, Cu, T
i, Fe, Zn and at least one selected from alloys containing them as a main component, and the second metal is Au, Ag, C
u, Al, Ni, Zn, Sn, P, and at least one selected from alloys containing these as main components, a third metal is plated around the first metal, and the third metal is plated with the first metal. It is preferable that the second metal is welded to the formed spiral recess.

According to the above construction, the metal hollow body for electric discharge machining has an outer diameter of 0.05 mm to 0.5 mm and an inner diameter of 20% to 80% of the outer diameter. Can be easily obtained.

As a method for manufacturing a metal hollow body for electric discharge machining, a plurality of first metal members having a melting point higher than that of the second metal by providing close contact or a gap around the second metal line. The wire is helically twisted and then heated at a temperature equal to or higher than the melting point of the second metal to melt the second metal and weld it between adjacent first metals to form a hollow electrode.

[0013] Then, the metal hollow body is passed through a die having a hole diameter equal to or smaller than the outer diameter of the metal hollow body.
Excessive welding of the second metal on the outer peripheral side of the first metal is removed, and the accuracy of the hole diameter to be processed is improved.

Further, before twisting the first metal and the second metal, a third metal is formed on the surface of the first metal so that the second metal has improved weldability to the first metal. Is preferably applied. Further, as the third metal, it is preferable to use one or more of Ni, Cu, Au, Ag, Sn, Zn, and any of these alloys.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The weak points inherent to Cu as an electrode are as follows.
If the material is changed to W, the characteristics are greatly improved. However, it is difficult to plastically process a fine hollow hole in W.
Therefore, the present inventors have conceived of forming a metal hollow body for electric discharge machining to be a hollow electrode by using a stranded wire using W as one of two kinds of metals as shown in FIG. The stranded wire 1 which is a starting material of FIG. 1 is arranged around a second metal 2 composed of a wire of a 72% Ag—Cu alloy, and a first metal 3 composed of a wire having the same diameter of W is disposed around the second metal 2. It is formed by twisting.

Next, the stranded wire 1 is continuously passed through a pipe-type softening furnace in a reducing atmosphere at 850 ° C. to form a metal hollow body 10 shown in FIG. In FIG. 2, reference numeral 3 denotes a first metal, and a second metal 2 is melted in a pipe-type softening furnace, cooled outside the furnace, and in a state as indicated by a black spot between adjacent first metals. Weld. As a result, a pipe-shaped metal hollow body 10 having the hollow portion 4 is formed. Since the layer of the second metal 2 to be welded between the first metals is likely to be non-uniform, the metal hollow is formed by passing a die having a hole diameter equal to or less than the outer diameter of the stranded wire 1 in the final step. It is preferable that the outer diameter of the body 10 be adjusted to improve the accuracy of the hole diameter of the processing hole. The depression 5 serves as a discharge path for processing chips carried out by a processing liquid described later.

As a machining fluid for electric discharge machining, a dielectric fluid having a high degree of insulation is generally used. Since the gap between the electrode and the work is extremely narrow, a material having a very high viscosity is not suitable, and a low-viscosity oil such as kerosene is suitable. In addition, the use of water containing an additive and controlling the specific resistance to 70,000 to 100,000 Ω · Cm greatly suppresses the electrolytically deteriorated layer around the processing hole, so that even if the processing hole is deep, there is no dripping at the entrance edge. High-precision drilling without burrs.

The hollow portion 4 has a role of circulating the high-pressure working fluid, and it is an important step to prepare the second metal 2 layer by passing through a die in order to prevent water leakage. As described with reference to FIG. 9 of the related art, another role of the processing fluid is to cool the work and discharge the decomposition gas and the processing waste 53. In order for the processing liquid A _{2 to} be smoothly discharged from the mouth of the work 50 together with the decomposition gas and the processing chips 53, a gap is required between the inner diameter of the processing hole and the outer diameter of the metal pipe 10. If the gap is large, the discharge of the decomposition gas and the processing debris 53 becomes easy, but the precision of the processing hole decreases.

In the metal hollow body 10 shown in FIG. 2 of the present invention, cracks and processing chips 53 are discharged along the spiral depression 5 of the stranded wire 1, so that the gap can be minimized. If the hollow metal body 10 is rotated in the direction corresponding to the twisting of the stranded wire 1 during drilling, the decomposition gas and the processing dust 53 are more effectively discharged. In other words, the spiral recess 5 plays a role equivalent to a chip discharge groove in a drill.

An enlarged photograph of a cross section of the metal hollow body 10 formed by the above procedure taken with a microscope is shown below. FIG. 3 is a cross-sectional photograph of the stranded wire 1 as a starting material. In FIG. 3, the first metal 3 is represented by a speckled black dot. FIG. 4 is a cross-sectional photograph of the stranded wire 1 continuously passed through the inside of the pipe-type softening furnace. In FIG. 4, the second metal 2 is melted in a pipe-type softening furnace and the adjacent first metal 2 is melted.
Therefore, a hollow portion 4 is formed at the center. FIG. 5 is a cross-sectional photograph of a metal hollow body in which a layer of the second metal 2 which has been excessively welded is removed by passing a die having a diameter equal to or smaller than the outer diameter of the stranded wire 1 and the accuracy of the outer diameter is adjusted. It is. On the outer periphery of the metal hollow body, the substance of the depression 5 that is naturally formed is shown.

The first metal 3 is composed of Mo, W, Cu,
The second metal 2 is made of at least one selected from Ti, Fe, Zn and an alloy containing them as main components, and the second metal 2 has a lower melting point than Au, Ag, Cu, Al, Ni, Zn, S
1 selected from n, P and alloys containing them as main components
You may select from more than species and combine them. Further, so that the second metal 2 improves the weldability to the first metal 3,
On the surface of the first metal 3, Ni, Cu, Au, Ag, Sn,
It is preferable to perform plating of a third metal made of Zn or any of these alloys.

As a form of the starting material, as shown in FIG.
If the wire diameter of the metal 2 is increased and the inner diameter of the first metal 3 is set to be eight in close contact with the periphery of the second metal 2, FIG.
A larger hollow is formed. As shown in FIG. 7, when the second metal 2 at the center is twisted in a hollow state and the first metal 3 is twisted around the second metal 2, the outer diameter is assumed to be equivalent to that of FIG. A hollow portion is formed.

The outer diameter of the metal hollow body 10 can be freely selected by a combination of the wire diameter and the number of the first metal 3 and the wire diameter of the second metal 2. However, when the outer diameter of the hollow metal body 10 becomes 0.5 mm or more, the C
Problems caused by the use of the u-pipe are considerably solved, and the economic efficiency of the metal hollow body 10 of the present invention is reduced. Also, metal hollow body 1
When the outer diameter of 0 is 0.05 mm or less, the mechanical strength is reduced in the step of adjusting the outer diameter by a die, and the inner diameter may be distorted. Therefore, the Young's modulus E (E = stress / strain) of the metal hollow body 10 is 147000 N / mm.
It is preferably at least ² .

Similarly, regarding the inner diameter, the first metal 3
Can be freely selected by a combination of the wire diameter and the number of the wires and the wire diameter of the second metal 2. However, when the inner diameter is 20% or less of the outer diameter, the flow of the working fluid is impeded. When the inner diameter is 80% or more of the outer diameter, the Young's modulus E is 14700.
0 N / mm ² or less.

The hollow portion 4 is heated at a temperature equal to or higher than the melting point of the second metal 2 to melt the second metal 2 and weld it between the adjacent first metals 3 to form a hollow. , FIG.
In the case where the cross-sectional area of the second metal 2 is relatively large as shown in (2), the excess of the molten second metal 2 excessively flows to the outer diameter side, In some cases, weirs are formed around the metal 3 without welding and clogging occurs.

In order to prevent the phenomenon that the second metal 2 blocks the hollow portion 4 like a bamboo node, as shown in FIG.
It is effective to dispose the second metal 2 with a gap inside the metal 3. That is, the wire diameter of the first metal 3 is d
1, the number is n1, the outer diameter of the stranded wire 1 is D, the inner diameter is d,
If the wire diameter of the second metal 2 is d2 and the number thereof is n2,
Area of the second metal 2 welded around the first metal 3 =
It suffices that (D ² −d ² −d1 ² · n1) π / 4 and the total cross-sectional area of the second metal 2 = d2 ² · n2 · π / 4 are balanced. Further, it is preferable that the expression (1) be established by multiplying a filling factor β indicating a rate at which the periphery of the first metal 3 is filled with the second metal 2. In ^{(D 2 -d 2 -d1 2 ·} n1) π / 4 · β = d2 2 · n2 · π / 4 (1) The present invention, beta is 0.6 to 0.8 is practical.

Next, a description will be given of the result of preparing the metal hollow body 10 of the present invention and an electrode made of a conventional Cu pipe and comparing the characteristics of electric discharge machining. As an example, there are three types based on an eight-strand starting material in which a first metal 3 is in close contact with a second metal 2 as shown in FIG. 6 and a second metal as shown in FIG. One kind was prepared in which a gap was provided around the metal 2 and the first metal 3 was a starting material of eight strands.

Example 1 As Example 1, a 48 μm wire made of Zn was used for the second metal 2 at the center, and the first metal 3 made of 20% Zn—Cu was used around the wire.
Eight 1 μm wires were twisted and continuously passed through a pipe-type softening furnace in a reducing atmosphere at 500 ° C. Then, φ
Outer diameter φ0.1m by passing through 0.1mm die
m, and a metal pipe 10 having an inner diameter of 0.045 mm was obtained. Incidentally, the inner diameter of the metal pipe 10 is 45% of the outer diameter, the filling coefficient is β = 1.01, and the Young's modulus is E = 1600.
00 N / mm ² .

(Embodiment 2) As Embodiment 2, the second
Of a 42 μm wire made of 72% Ag—Cu is used as the metal 2 of
Eight 8 μm wires were twisted and continuously passed through a pipe-type softening furnace in a reducing atmosphere at 850 ° C. Then, φ
Outer diameter φ0.1m by passing through 0.1mm die
m, a metal pipe 10 having an inner diameter of 0.04 mm was obtained. Incidentally, the inner diameter of the metal pipe 10 is 40% of the outer diameter, the filling coefficient is β = 1.13, and the Young's modulus is E = 3040.
00N / mm ² .

Example 3 As Example 3, a 67 μm wire made of 40% Zn—Cu was used as the second metal 2 at the center, and the first metal 3 made of W was 42 around the wire.
Eight μm wires were twisted and continuously passed through a pipe type softening furnace at 950 ° C. in a reducing atmosphere. Then, φ
By passing a 0.15mm die, the outer diameter φ0.1
A metal pipe 10 having a diameter of 5 mm and an inner diameter of 0.065 mm was obtained. Incidentally, the inner diameter of the metal pipe 10 is 43 times the outer diameter.
%, The filling factor is β = 0.84, and the Young's modulus is E = 2.
It was 65000 N / mm ² . In Examples 1 and 2 in which the filling coefficient β exceeds 1.0, a slight clogging occurs in the hollow portion 4 for collecting an electrode as a sample having an effective length of 50 mm, and the yield of Example 1 is 80. %, The yield of Example 2 was reduced to about 90%, but the yield of Example 3 was 9%.
There was almost no problem at about 5%.

(Embodiment 4) As Embodiment 4, the second
A 33 μm wire made of 72% Ag—Cu was used as the metal 2, and a twist was formed with an inner diameter of 42 μm with a gap around the wire.
28 μm, which is the first metal 3 made of W,
, And continuously passed through a pipe-type softening furnace in a reducing atmosphere at 850 ° C. Then, φ0.1
The metal pipe 10 having an outer diameter of 0.1 mm and an inner diameter of 0.042 mm was obtained by passing the same through a die having a diameter of 0.1 mm. By the way,
The inner diameter of the metal pipe 10 is 43% of the outer diameter, the filling coefficient is β = 0.69, and the Young's modulus is E = 304000N.
/ Mm ² . In the fourth embodiment, the filling factor is β =
By setting the ratio to 0.69, clogging was not generated over the entire length of the stranded wire 1 and excessive outflow of the molten metal to the outer diameter side was not recognized, and the metal hollow body 10 having a good yield could be obtained.

As comparative examples, the following three types of Cu pipes formed by the prior art were prepared. Comparative Example 1
Was a Cu pipe having an outer diameter of 0.08 mm and an inner diameter of 0.035 mm, and the Young's modulus was E = 118000 N / mm ² . Comparative Example 2 has an outer diameter of 0.1 mm and an inner diameter of 0.04 m
m Cu pipe, Young's modulus is E = 118000
N / mm ² . Comparative Example 3 has an outer diameter of 0.15 mm,
The Cu pipe had an inner diameter of 0.065 mm, and the Young's modulus was E = 118000 N / mm ² .

Using these hollow electrodes having an effective length of 50 mm as a sample, a thickness 2 made of die steel (SKD-11) was used.
A current density of 10 ⁶ to 10 ⁷ W / cm ^{2 is} applied to a 0 mm workpiece.
Table 1 shows the results of drilling by electric discharge machining.
As the evaluation items, the electric discharge machining speed, the consumption amount of the electrode, and the accuracy of the electrode entrance and exit holes were selected from the time required for drilling, and the result of Example 1 was indexed as 100.

[0034]

[Table 1]

Considering the results in Table 1, the electric discharge machining speed is:
Compared to Example 1, Comparative Examples 1 to 3 required 1.3 times as much time, and the amount of electrode consumption reached 8 to 10 times. In Comparative Example 3, the electrodes were so consumed that the holes could not be penetrated. Was.
The hole accuracy is 22 to 3 for both roundness and straightness of inlet and outlet.
It decreased by 3%. In addition, even if the metal pipes have substantially the same dimensions satisfying the conditions of the present invention, the W pipe has 20% Zn-
It was found that the electrode was superior to a metal pipe made of Cu as an electrode.

[0036]

According to the present invention, linear Au, Ag, Cu, Al, Ni,
Mo, Mo is formed by providing a close contact or a gap around a second metal made of Zn, Sn, P and an alloy mainly containing them.
The first metal, which is a plurality of wires made of W, Cu, Ti, Fe, Zn, and an alloy containing them as main components, is twisted and heated at a temperature equal to or higher than the melting point of the second metal, and the second metal is heated. Since the metal was melted and welded between the adjacent first metals to form a hollow metal body, the outer diameter was 0.5 m with little electrode consumption.
m or less can be manufactured inexpensively.

Further, by passing a die having a hole diameter equal to or less than the outer diameter of the second metal, the second metal which is non-uniformly welded to the outer periphery of the plurality of first metals is removed and the second metal is removed. A metal hollow body for electric discharge machining in which a metal layer is prepared to prevent water leakage, and the outer diameter of the hollow metal body is 0.05 mm or more and 0.5 mm or less, and the inner diameter is 20% or more and 80% or less of the outer diameter. So, let the machining fluid flow into the hollow part,
It is possible to provide an electrode that can efficiently and highly accurately process extremely fine holes while discharging processing chips along the spiral depression on the outer periphery.

[Brief description of the drawings]

FIG. 1 is a sectional view of a stranded wire which is a starting material of the present invention.

FIG. 2 is a cross-sectional view of the metal hollow body of the present invention.

FIG. 3 is a cross-sectional photograph of a stranded wire as a starting material of the present invention.

FIG. 4 is a cross-sectional photograph of the metal hollow body of the present invention.

FIG. 5 shows a secondary welded excessively by passing through a die.
5 is a cross-sectional photograph of a metal hollow body in which a second metal layer is prepared while removing the metal.

FIG. 6 shows a first metal surrounding a second metal which is a starting material of the present invention.
FIG. 5 is a cross-sectional view of eight strands in which the metals of FIG.

FIG. 7 is a cross-sectional view of a nine-stranded wire in which a second metal, which is a starting material of the present invention, is twisted in a hollow state, and the first metal is in close contact therewith.

FIG. 8 is a cross-sectional view in which eight first metals are twisted with a gap around a second metal which is a starting material of the present invention.

FIG. 9 is an explanatory view of a processing liquid supply unit using a conventional electrode of a metal pipe.

FIG. 10 is an explanatory view of a working fluid supply means using a conventional metal wire electrode.

FIG. 11 is a sectional view of a working fluid supply device using a conventional electrode of a metal wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stranded wire 2 2nd metal 3 1st metal 4 Hollow part 5 Spiral hollow 10 Metal hollow body

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B21F 7/00 B21F 7/00 Z (72) Inventor Yoshihiro Nakai 1-3-1 Shimaya, Konohana-ku, Osaka-shi, Osaka No. Sumitomo Electric Industries, Ltd. Osaka Works F-term (reference) 3C059 AA01 AB01 DA03 DA07 DB03 DC01 HA14 4E070 AA00 AB00 AC00 BA02 BA20 BD00 EA05 FA02 FA03

Claims (8)

[Claims] 1. An electrode for electric discharge machining, wherein a plurality of wires made of a first metal are spirally twisted to be hollow, and a spiral recess formed between at least adjacent wires. A second metal having a melting point lower than the melting point of the first metal is welded to the metal hollow body for electric discharge machining. 2. The method according to claim 1, wherein the first metal is Mo, W, Cu, Ti,
Fe, Zn and at least one selected from alloys containing them as main components, wherein the second metal is Au, Ag, C
2. The metal hollow body for electric discharge machining according to claim 1, wherein the metal hollow body comprises at least one selected from u, Al, Ni, Zn, Sn, P and an alloy containing these as main components. 3. The method according to claim 1, wherein a third metal is plated around the first metal, and a second metal is welded to a spiral depression formed of the first metal. 1 or 2
2. The metal hollow body for electrical discharge machining according to claim 1. 4. The metal hollow body according to claim 1, wherein the outer diameter of the hollow metal body is 0.05 mm or more and 0.5 mm or less, and the inner diameter is 20% or more and 80% or less of the outer diameter. The hollow metal body for electrical discharge machining according to any one of the above. 5. A plurality of wires made of a first metal having a melting point higher than that of said second metal with a close contact or a gap provided around said second metal in a spiral manner, and thereafter, A metal for electric discharge machining, wherein the metal is heated at a temperature equal to or higher than the melting point of the second metal, and the second metal is melted and welded between the adjacent first metals to form a hollow electrode. A method for manufacturing a hollow body. 6. Excessive welding of the second metal on the outer peripheral side of the first metal is removed by passing the hollow metal through a die having a hole diameter equal to or less than the outer diameter of the hollow metal. The method for producing a metal hollow body for electric discharge machining according to claim 5, characterized in that: 7. The method according to claim 5, wherein before the first metal and the second metal are twisted, the surface of the first metal is plated with a third metal. A method for producing a metal hollow body for electric discharge machining. 8. The method according to claim 8, wherein the third metal is Ni, Cu, Au,
The method for producing a metal hollow body for electric discharge machining according to claim 7, wherein any one of Ag, Sn, Zn, and an alloy thereof is used.