CZ303399A3 - Saw wire - Google Patents

Abstract

Circular saw wire with a cut width of less than 0.3 mm, steel wire assembly, interlayer, which prevents hydrogen wire brittleness and ensures sufficient adhesion of the metal binder phase; metal binder phase into which diamond grains are deposited.

Description

The invention relates to a saw wire.

BACKGROUND OF THE INVENTION

The production of thin wafers from blocks or single crystals of brittle hard materials is largely accomplished by separation processes using bonded abrasives or a loose abrasive grain saw wire. If it is an expensive starting material, such as monocrystalline or polycrystalline silicon blocks, the smallest loss in cutting is of great economic importance. Therefore, in the production of silicon wafers from silicon blocks today, for example, cutting widths of less than 0.3 mm are prior art. The silicon wafers are separated either by diamond-punched holes or by multiple wire saws using abrasive compositions in the form of suspensions, preferably those containing silicon carbide.

The cutting width during cutting is naturally greater than the thickness of the saw blade. diameter of the saw wire. The coarser the cutting grain used, the wider the cut, the unwanted material loss increases accordingly. Therefore, the effort to select the finest abrasive grain that still brings acceptable

77569 (77569a.doc) 9 9 999 9 9 9 9

999999 99 99 cutting power. For diamond grain punched holes, the grain size of D 46 (FEPA Standard or 325/400 mesh according to US ASTME 11) with a mean diameter of about 50Π μιη has been established as a practical lower limit.

The wire saw has the advantage that the required small cutting widths can still be realized with blocks over 200 mm in diameter. In this separation technique, a high-strength steel wire is guided as a saw wire through multiple grooves through grooved rollers by adding a suspension with grains of very hard material, mostly silicon carbide with a grain size of 20 to 25 μιη, under moderate pressure by the block to be cut. The wire works continuously over the entire cross-section of the block. Disadvantageously, the wire itself wears heavily and can therefore only be used once.

Since the metal-bonded friction diamond liner used, for example, in punches, wears considerably less than a wire when slurrying with a slurry, it has already been tried to lining the wire with a diamond grain.

In order to hold the diamond grains firmly on the saw wire, the binder phase should consist of metal. In practice, nickel has proven to be a suitable bonding metal in the coating production of metal-bonded diamond friction linings. Nickel can be deposited, for example, in pure form electrolytically or electrolessly as a nickel alloy with proportions of phosphorus or boron. For electroless nickel alloys, the term chemical nickel has been established.

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Disadvantageous is the formation of hydrogen in the plating itself and also in the normal preparation of the carrier material, which can lead to spontaneous fractures in the case of unalloyed, high-strength steel wires due to the so-called hydrogen embrittlement. Unalloyed, high-strength steel wires are typically used for suspension wire saws. Higher alloy steels, which are insensitive to hydrogen embrittlement, have the disadvantage that the electroplated nickel layers often do not adhere sufficiently. With multiple turns required in a wire saw, these layers, even with embedded diamond grains, pop out.

Special press Diamond wire saw for precision cuts by W. Ebner, fa. Well from Eurotec No. 218 of February / March 1985, FIG. 3 is an electron micrograph of a galvanically coated diamond saw wire, FIG. 4 an electron micrograph of a chemically coated saw wire, and FIG. 5 an electron micrograph of a mechanically coated diamond saw wire. rolled surface layer. While the scale is shown in Fig. 4, no scale data is shown in Fig. 3 and Fig. 4. Further information on the grain size or composition of the surfaces shown is also missing. The production of the illustrated wires is not disclosed. Under point 2 of the special press, it is stated that the diamond can be applied to the wire in three ways, namely galvanic deposition, chemical coating and mechanical rolling. Details of the manufacturing processes are not included in the file. It is only mentioned that wires below 0.1 mm in diameter cannot be galvanically coated due to the hydrogen embrittlement of the wire emerging in the galvanic bath, and that the chemical coating is performed only in individual cases. Problem

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999 9 999 99 99 99 99 however, hydrogen embrittlement also occurs at higher wire diameters.

Only mechanically-rolled diamond grain wire is available on the market, and this wire is available only in laboratory lengths. Such a wire loses its cutting ability very quickly because the diamond grains break out easily. In addition, the tensile strength of the carrier wire is greatly reduced due to the penetration of sharp-edged diamond particles, so that only slight cutting forces can be achieved.

Thus, a saw wire with a cutting width of <0.3 mm is not available in a diamond-bonded metal grain design.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a cross-section of a circular saw wire with a cutting width of less than 0.3 mm having a cutting performance comparable to suspension cutting and can be reused many times.

The invention relates to a saw wire consisting of a steel wire, an interlayer which, on the one hand, avoids hydrogen brittleness of the wire and, on the other hand, ensures sufficient adhesion of the metal binder phase and the metal binder phase in which the diamond grains are embedded.

The saw wire according to the invention, including the abrasive grain layer, preferably has a diameter of up to 0.25 mm.

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As a steel wire, a non-corrosive chromium-nickel steel spring steel wire is preferably used. Material types 1.4310, 1.4401, 1.4539, 1.4568 and 1.4571 (designation according to German industrial standard 17224) are suitable.

The intermediate layer preferably comprises a metal, a metal alloy, or a combination of two metals, respectively. metal and metal alloys.

Preferably, it is a metal, a metal alloy, or a combination of two metals, respectively. metal and metal alloy which can be electroplated and a hydrogen barrier.

Suitable metals are, for example, copper, e.g. brass.

This is particularly advantageous

which at the same time works as and nickel and like alloy of metals throws nickel.

The intermediate layer preferably has a thickness of from 1 to 10 µm.

The metal binder phase preferably consists of nickel or nickel. of nickel alloy.

Particularly preferably it consists of electroless nickel (chemical nickel).

The metal binder phase preferably has a thickness of from 5 to 20 µm.

The diamond grains preferably have a size of from 5 to 30 μηα.

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They are preferably present on the wire in an amount such that their mean distance is no more than 5 times, and preferably 1 to 3 times their mean diameter.

Preferably, the thickness of the interlayer around the wire does not change by more than 5%.

Preferably, the thickness of the metal binder phase around the wire does not change by more than 5%.

The saw wire according to the invention can be produced, for example, as follows:

A steel wire with an interlayer which prevents both the hydrogen brittleness of the wire and ensures sufficient adhesion of the metal binder phase is known in the art. Such wires consisting of a nickel-plated wire of material 1.4310 (according to German Industrial Standard 17224) are available, for example, under the designation 12 R 10 Nicoat from Sandvik, Dusseldorf.

In principle, however, it is also possible according to the method known in the art to coat the steel wire with a suitable intermediate layer.

For the production of the starting material for the saw wire according to the invention, wires whose diameter is still three times greater than the diameter of the wire according to the invention are preferably used for this purpose. These wires can be nickel-plated economically according to the known method. By drawing this coated starting material, for example, spring wires with about 2 □ μιη can be used

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9999 999 99 99 99 99 Thick, well-adhering nickel coating and high tensile strength can also be produced from high-alloy spring steels.

In principle, both electrolytic plating and electroless plating are known as a method for depositing a metal binder phase with diamond grains on an intermediate layer wire.

Although electrolytic plating is faster and cheaper, electroless plating is preferably used because it allows for a uniform thickness of the binder phase layer.

Here, the procedure is as follows:

The interlayer coated wire is subjected to a chemical pretreatment adapted to the base material. Pretreatment is a prerequisite for obtaining an adhesive coating. It is known in the art and usually consists of known degreasing, etching and activation treatments. Subsequently, the coating is carried out in a so-called chemical nickel-plating diamond bath (bath for electroless nickel plating). Such baths are known in the art. By suitably moving the wire and the electrolyte, the diamonds are evenly distributed over the entire circumference of the wire. The thickness of the precipitated binder phase is dependent on the size of the diamond particles. These suitable process parameters are known in the art.

Advantageously, the binder phase is thermally cured following the coating. This is preferably done by a heat treatment of at least 1 hour.

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Optimal curing preferably requires a temperature of 250 to 450 ° C, particularly preferably about 350 ° C.

By thermal curing, the properties of the binder phase are greatly improved, the tensile internal stress is degraded, the adhesion increases and the hardness increases by more than 50%.

This achieves not only a stronger deposition of the deposited diamond particles, but also increases the wear resistance of the binder phase, so that the diamond loss due to matrix wear is delayed.

These temperatures lead to a drastic loss of tensile strength and elasticity in the case of high-strength unalloyed wire, which is unacceptable for use in a wire saw. In addition, unalloyed steel wire is susceptible to corrosion.

In general, therefore, considering all the influences on the operating behavior of the saw wire, it is preferable to use a highly alloyed carrier material as the starting material for making the saw wire of the invention. Preferably, diamonds are deposited on the wire provided with the intermediate layer described in the electrolessly deposited metal binder phase.

However, some non-alloyed, described interlayer coated wire with an electrolytically excluded, non-curable binder phase containing diamonds is also perfectly suited for some applications.

The saw wire according to the invention is surprising

77569 (77569a.doc) ··························· ·· shows that even with considerably finer grains than with grain D 46, predominantly used in the prior art (for punches), satisfactory cutting performance is still achieved.

The saw wire according to the invention is particularly suitable for cutting expensive hard brittle materials in which the smallest possible loss in cutting is of great economic importance.

The following example serves to further explain the invention.

Example:

60m high-alloy steel wire with a diameter of 0.20 mm, available under the designation 12 R 10 Nicoat from Sandvik, was clamped on a stand, common for electroless nickel plating.

The wire was subjected to degreasing, etching and activation processing, as is common with electroless nickel plating. Subsequently, the coating is carried out in a chemical nickel-plating diamond bath available on the market (under the designation Niposit 65 at Shipley in Esslingen). Diamond particles with a grain size of 15 to 25 μιη are added to the bath (a standardized standard product is available from various suppliers). The movement of the wire and the electrolyte resulted in a uniform placement of the diamonds over the entire circumference of the wire into the binder phase consisting of chemical nickel. After coating, the wire was heat treated at 350 ° C for one hour to cure.

Subsequently, the saw wire was obtained according to the invention

77569 (77569a.doc) φ φ · ♦ · · · · · · · · · · · · · · · · · · · · · · · · ·· ·· ·· wound on wire drums wire saw by fy. Well (Series 3), which was equipped with a measuring system to determine the cutting performance. Prismatic bodies of very pure silicon with a cross-section of 10 x 10 mm were cut ten times in succession with a wire saw. The cutting time was measured and the respective cutting power was calculated.

As comparative tests, the same cutting tests were carried out on conventional wire with mechanically rolled diamond grain (Well, type A 3-2, grain size 60 µm).

The results are shown in Table 1.

Tab. 1: Cutting performance depending on the time of use

Cutting capacity in mm / min Saw wire comparative test Saw wire according to the invention test 1 0.65 1.60 test 2 0.60 1.40 test 3 0.50 1.38 test 4 0.47 1.38 test 5 0.45 1.20 test 6 0.45 1.10 test 7 0.42 0.90 exam 8 0.40 0.80 test 9 0.38 0,8 0 test 10 0.35 0.70

The results in Table 1 show that the cutting power of the wire

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The present invention is 2 to 3 times higher than the cutting power of conventional wire. Furthermore, it is clear that the wire according to the invention has a better cutting performance after a 10-fold use than a new unused reference wire. Accordingly, the resistance of the wire according to the invention is also much higher than that of the known saw wire.

The high cutting performance and the considerably improved wire resistance of the invention result from good mechanical anchorage of the solid particles in the wear-resistant binder phase. In contrast to the comparative wire, a tight diamond lining was also available after several cuts.

Represented by:

Dr. Miloš Všetečka v.r.

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JUDr. Milos Všetečka advocate

120 00 Prague 2, Hálkova 2 ý SGlOLj.

to: / ·· ·· ·· S

Claims (10)

PATENT CLAIMS saw _ __ .. _________ ______ for less than 0.3 mm, consisting of steel wire, an interlayer that both prevents hydrogen brittleness of the wire, and ensures sufficient adhesion of the metal binder phase, and of the metal binder phase in which diamond grains are deposited . The saw wire according to claim 1, characterized in that a non-rusting chrome-nickel steel spring wire is used as the steel wire. The saw wire according to claim 1 or 2, characterized in that the steel wire has a diameter of 0.15 to 0.25 mm. The saw wire according to any one of claims 1 to 3, characterized in that the interlayer consists of a metal, a metal alloy or a combination of two metals, respectively. metal and metal alloys, it can be galvanically coated with good adhesion and also acts as a hydrogen barrier. The saw wire according to claim 4, characterized in that the intermediate layer consists of nickel. The saw wire according to claim 4 or 5, characterized in that the interlayer has a force of 1 to 10 □ μπι. 16 77569 (77569a.doc) • 9 9 ··· 99 · * · ··· «9999 9 9 99 9 999 9 9 «9 • 999 49« 99 99 999 99 99 99 99 99 49 4 9 The saw wire according to any one of claims 1 to 6, characterized in that the metal binder phase consists of nickel or nickel. nickel alloys. The saw wire of claim 7, wherein the metal binder phase has a thickness of from 5 to 20 µm. The saw wire of claim 1, wherein the diamond grains have a size of from 5 to 30 µm. The saw wire according to any one of claims 1 to 9, characterized in that the thickness of the metal binder phase around the wire does not change by more than 5%.