MACHINING METHOD FOR A PLATE-SHAPED WORKPIECE

Abstract

Machining method for a plate-shaped workpiece (2) for machining a plate-shaped workpiece (2) having a parting line (8a, 8b) and a metal element (12) formed on the parting line (8a, 8b) or in an area corresponding to the parting line (8a, 8b), wherein the machining method for a plate-shaped workpiece (2) comprises: a holding step for holding the plate-shaped workpiece (2) by a clamping table (20) at a clamping in the state in which the metal element (12) is exposed; a first cutting step for cutting the plate-shaped workpiece (2) along the parting line (8a, 8b) using a first cutting blade (26, 26A) after performing the holding step, thereby forming a first cut groove (32) which divides the metal element (12); and a second cutting step for cutting the plate-shaped workpiece (2) along the first cut groove (32) using a second cutting blade (26, 26A) after performing the first cutting step, thereby forming a second cut groove (34) which completely cuts the plate-shaped workpiece (2), so that the cutting blade (26, 26A) projects into an outlet groove (24) of the clamping table (20); wherein the first cutting step includes the step of supplying a cutting fluid (30) containing an organic acid and an oxidizing agent to the plate-shaped workpiece (2).

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a machining method for a plate-shaped workpiece for machining a plate-shaped workpiece which has a parting line and a metal element which is formed on the parting line or in an area corresponding to the parting line. Description of the state of the art

[0002] A wafer, such as a semiconductor wafer, has a front face on which several components are formed by intersecting division lines. The wafer, containing these components, is cut along these division lines, thereby dividing it into individual component chips. In some cases, a metal film is applied to the back face of the wafer, improving the electrical characteristics of each component. However, when this metal film is cut by a cutting blade, the blade can become clogged. Furthermore, cutting the wafer through this clogged blade can cause cracks in the wafer or damage the cutting blade itself.

[0003] In another case, a test element group (TEG) is formed as a metal element at each division line of the wafer, allowing the electrical characteristics of each element to be measured. When this wafer, containing the TEG, is cut along each division line by a cutting blade, the cutting blade can become clogged. Another known plate-shaped workpiece, having a division line and a metal element formed at the division line, is a packed substrate. A packed substrate has an electrode surface in which several electrodes are formed. In a machining process for the packed substrate, the packed substrate is cut from the electrode surface by a cutting blade, thereby dividing it into individual packings.When the packaged substrate is cut through the electrode surface with a cutting blade, a problem arises: burrs can form on the electrodes during the cutting process. To avoid clogging of the cutting blade, a method for cutting a workpiece containing metal electrodes using a saw blade with carbide tips instead of the cutting blade was proposed in Japanese patent application JP H09-55573A. PRESENTATION OF THE INVENTION

[0004] In the cutting method proposed in Japanese patent application JP H09-55573A, the saw blade with carbide tips does not have a self-sharpening function, unlike the cutting blade. Consequently, the sharpness of the saw blade diminishes over time. This leads to a high saw blade change frequency, which reduces machinability. Furthermore, when the metal element formed on the workpiece is cut by a cutting blade, the cutting blade can become clogged, as described above. This creates another problem: the metal element being cut is elongated, causing burrs or distortion. Generally, increasing the feed rate increases the cutting load and the heat generated during cutting, resulting in more burrs and distortion.Accordingly, it is difficult to increase the feed rate while preventing a decrease in processing quality.

[0005] JP 2016 - 54 182 A discloses a method for machining a plate-shaped workpiece which has a parting line and a metal element which is formed on the parting line or in an area corresponding to the parting line.The machining process comprises the following steps: a holding step to hold the plate-shaped workpiece on a clamping table in the exposed state; a first cutting step to cut the plate-shaped workpiece along the parting line using a first cutting blade after performing the holding step, thereby forming a first cut groove that parts the metal element; and a second cutting step to cut the plate-shaped workpiece along the first cut groove using a second cutting blade after performing the first cutting step, thereby forming a second cut groove that completely cuts through the plate-shaped workpiece. In the first cutting step, a cutting fluid containing an organic acid and an oxidizing agent is applied to the plate-shaped workpiece.

[0006] JP 2004 - 259 936 A discloses the provision of a cutting blade whose cutting depth can be adjusted when cutting a workpiece.

[0007] Therefore, an objective of the present invention is a machining method for a plate-shaped workpiece for machining a plate-shaped workpiece which has a parting line and a metal element which is formed on the parting line or in an area corresponding to the parting line, in which the feed rate can be increased by this method in comparison with the prior art.

[0008] In accordance with one aspect of the present invention, a machining method for a plate-shaped workpiece is provided for machining a plate-shaped workpiece having a parting line and a metal element formed on the parting line or in a region corresponding to the parting line, wherein the machining method for a plate-shaped workpiece comprises a holding step for holding the plate-shaped workpiece by a clamping table in a clamping position in a state in which the metal element is exposed; a first cutting step for cutting the plate-shaped workpiece along the parting line using a first cutting blade after performing the holding step, thereby forming a first cut groove that divides the metal element;and a second cutting step for cutting the plate-shaped workpiece along the first cut groove using a second cutting blade after performing the first cutting step, thereby forming a second groove that completely cuts the plate-shaped workpiece, so that the cutting blade projects into an outlet groove of the clamping table; wherein the first cutting step includes the step of supplying a cutting fluid, comprising an organic acid and an oxidizing agent, to the plate-shaped workpiece.

[0009] According to the machining method of the present invention, the plate-shaped workpiece is cut in two steps along its thickness direction using a first and second cutting blade. Accordingly, the thickness of the workpiece to be cut can be reduced in each step, thus increasing the machining speed (feed rate) compared to cutting the workpiece completely in one step. Furthermore, during the first cutting step, a cutting fluid containing an organic acid and an oxidizing agent is supplied to the workpiece. The organic acid in the cutting fluid modifies the metal present on the workpiece, reducing its ductility and thereby preventing the formation of burrs.Furthermore, the surface properties of the metal element are altered by the oxidizing agent contained in the cutting fluid, causing the metal element to lose its ductility, resulting in easier cutting and thus improved machinability.

[0010] The above and other aims, features and advantages of the present invention and the manner of realizing them will be made clearer and the invention itself best understood by studying the following description, the claims attached to it, with reference to the attached figures, which show a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is a top view of a packaged substrate; Fig. Figure 2 is a view of the packaged substrate, which is in Fig. 1 is shown, from below; Fig. 3 is an enlarged sectional view showing a holding step; Fig. Figure 4 is an enlarged sectional view showing a first cutting step; Fig. 5A is an enlarged sectional view showing a second cutting step in the case of using the same cutting blade that was used in the first cutting step; Fig. 5B is a Fig. 5A Similar view showing the case of using a cutting blade that has a thickness smaller than that of the cutting blade used in the first cutting step; Fig. 6A is a cross-section of electrodes contained within the packaged substrate after the first cutting step has been performed, while pure water is supplied for comparison. Fig. 6B is a view similar to Fig. 6A, which shows the case of supplying a cutting fluid comprising an organic acid and an oxidizing agent according to the present invention; Fig. Figure 7 is a graph representing the average distance between connections after performing the first cutting step in the case of supplying pure water and in the case of supplying the cutting fluid; and Fig. Figure 8 is a side view showing a nozzle means for supplying the cutting fluid in the first cutting step according to a modification. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0011] Preferred embodiments of the present invention will now be described in detail with reference to the figures. Fig. Figure 1 shows a top view of a packaged substrate 2 as a workpiece to be machined by the machining method of the present invention. Fig. Figure 2 is a top view from below of the packaged substrate 2, which is in Fig. 1 is shown. As in Fig. 1 and Fig. As shown in Figure 2, the packaged substrate 2 has a rectangular base substrate 4. The base substrate 4 has an electrode surface 4a on the front side and a sealed surface 4b on the rear side. Several electrodes 12 are formed on the electrode surface 4a. The sealed surface 4b is opposite the electrode surface 4a. The electrode surface 4a of the base substrate 4 has a perimeter border 5 and two areas without a component 5a. Furthermore, three component areas 6a, 6b, and 6c are defined such that they are surrounded by the perimeter border 5 and the two areas 5a without components. The base substrate 4 is formed from a metal frame, for example.

[0012] In each of the component areas 6a, 6b, and 6c, several mounting sections 10 for a component are configured such that they are separated by several first and second division lines 8a and 8b that intersect at right angles. Each mounting section 10 is configured with several electrodes 12. These electrodes 12 are insulated by a cast plastic provided on the base substrate 4. Each of the first division lines 8a is cut along its center to separate the electrodes 12 formed at each division line 8a. Similarly, each of the division lines 8b is cut along its center to separate the electrodes 12 formed at each division line 8b.

[0013] Although not shown, a component is mounted at each mounting section 10 for a component of the base substrate 4. Each component has several electrodes that are connected by gold wires to the electrodes 12 of each mounting section 10 for a component of the base substrate 4. As shown in Fig. As shown in Figure 2, three sealed plastic sections 18 are formed on the rear sides of the three component areas 6a, 6b and 6c, i.e. on the sealed surface 4b of the base substrate 4. Each component is sealed with this plastic.

[0014] Now, a machining method for a plate-shaped workpiece according to a preferred embodiment of the present invention is described with reference to the Fig. 3-7 described. In this preferred embodiment, the packaged substrate 2 is used as a plate-shaped workpiece. First, as described in Fig. As shown in Figure 3, a holding step is performed to hold the packaged substrate 2 under suction by a clamping table 20 at a clamping of a cutting device (not shown) in the state in which the electrodes 12, which are formed at the division lines 8a and 8b of the packaged substrate 2, are exposed.

[0015] The clamping table 20 includes a suction passage 22 and several outlet grooves 24. The suction passage 22 is connected to a vacuum source (not shown) via the clamping of the cutting device. The outlet grooves 24 are designed to correspond to the respective division lines 8a and 8b of the packaged substrate 2. The outlet grooves 24 serve to prevent the tip (outer edge) of the cutting blade from cutting into the clamping table 20 when the packaged substrate 2 is being completely cut. The packaged substrate 2 is held on the clamping table 20 in the state in which the division lines 8a and 8b of the packaged substrate 2 are aligned with the outlet grooves 24 of the clamping table 20, as shown in the top view.Then the suction passage 22 of the clamping table 20 is brought into contact with the vacuum source through the clamping of the cutting device, so that a vacuum is applied by the vacuum source to the suction passage 22, whereby the packaged substrate 2 is held by the clamping table 20 under suction.

[0016] After performing the holding step, a first cutting step is carried out to cut the packaged substrate 2 along the division lines 8a and 8b using a cutting blade 26 as a first cutting blade, thereby forming a first cut groove 32 which divides each electrode 12 formed at the division lines 8a and 8b, as shown in Fig. 4 shown. In this first cutting step, a cutting fluid 30, which contains an organic acid and an oxidizing agent, is supplied from a pair of nozzles 28 for a cutting fluid, which are located on both sides of the cutting blade 26, as shown in Fig. 24 shown, are provided. That is, the packaged substrate 2 is not cut deeply by the cutting blade 26 to form a first cut groove 32 which divides each electrode 12, while the cutting fluid 30 is supplied to the packaged substrate 2.

[0017] Amino acids can be used as the organic acid. Examples of amino acids that can be used here include glycine, dihydroxyethylglycine, glycylglycine, hydroxyethylglycine, N-methylglycine, β-alanine, L-alanine, L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine, L-alloisoleucine, L-isoleucine, L-phenylalanine, L-proline, sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothreonine, L-homoserine, L-thyroxine, L-tyrosine, 3,5-diiodo-L-tyrosine, β-(3,4-dihydroxyphenyl)-L-alanine, 4-hydroxy-L-proline, L-cysteine, L-methionine, L-ethionine. L-Lanthionine, L-Cystathionine, L-Cystine, L-Cystic acid, L-Glutamic acid, L-Aspartic acid, S-(Carboxymethyl)-L-Cysteine, 4-Aminobutyric acid, L-Asparagine, L-Glutamine, Azaserine, L-Canavanine, L-Citrulline, L-Arginine, δ-Hydroxy-L-Lysine, Creatine, L-Kynurenine, L-Histidine, 1-Methyl-L-Histidine, 3-Methyl-L-Histidine, L-Tryptophan, Actinomycin C1, Ergothioneine, Apamin, Angiotensin I, Angiotensin II, Antipain, etc.Among others, glycine, L-alanine, L-proline, L-histidine, L-lysine, and dihydroxyethylglycine are particularly preferred.

[0018] Aminopolyacids can also be used as the organic acid. Examples of aminopolyacids that can be used here include iminodiacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, hydroxyethyliminodiacetic acid, nitrilotrismethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, 1,2-diaminopropanetetraacetic acid, glycoletherdiaminetetraacetic acid, transcyclohexanediaminetetraacetic acid, ethylenediamineorthohydroxyphenylacetic acid, ethylenediaminedisuccinic acid (SS isomer), β-alaninediaacetic acid, N-(2-carboxyatoethyl)-L-aspartic acid, N-N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, etc.

[0019] Furthermore, carboxylic acids can be used as organic acids. Examples of carboxylic acids that can be used here include saturated carboxylic acids such as formic acid, glycolic acid, propionic acid, acetic acid, butyric acid, valeric acid, caproic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, malic acid, succinic acid, pimelic acid, mercaptoacetic acid, glyoxylic acid, chloroacetic acid, pyruvic acid, acetoacetic acid, etc.; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, mesaconic acid, citraconic acid, aconitic acid, etc.; and cyclic unsaturated carboxylic acids such as benzoic acid, toluic acid, phthalic acid, naphthoic acids, pyromellitic acid, naphthalic acid, etc.

[0020] Examples of oxidizing agents that can be used there include hydrogen peroxide, peroxides, nitrates, iodates, periodates, hypochlorites, chlorites, chlorates, perchlorates, persulfates, dichromates, permanganates, cerates, vanadates, ozonated water, silver(II) salts, iron(III) salts, and their organic complex salts.

[0021] Furthermore, a corrosion inhibitor can be mixed into the cutting fluid 30. Mixing in the corrosion inhibitor prevents corrosion (elution) of the metal contained in the packaged substrate 2. A heterocyclic ring compound with at least three nitrogen atoms in its molecule and a fused ring structure, or a heterocyclic aromatic ring compound with at least four nitrogen atoms in its molecule, is preferably used as the corrosion inhibitor. The aromatic ring compound preferably comprises a carboxyl group, a sulfo group, a hydroxy group, or an alkoxy group.

[0022] Specifically preferred examples of the aromatic ring compound include tetrazole derivatives, 1,2,3-triazole derivatives and 1,2,4-triazole derivatives.

[0023] Examples of tetrazole derivatives that can be used as corrosion protection include those that have no substituent group on the nitrogen atoms forming the tetrazole ring and that have a substituent group inserted at the 5-position of the tetrazole selected from the group consisting of a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group, or an alkyl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxyl group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group.

[0024] Examples of 1,2,3-triazole derivatives that can be used as corrosion inhibitors include those that have no substituent group on the nitrogen atoms forming the 1,2,3-triazole ring and that have a substituent group inserted at the 4-position and / or the 5-position of the 1,2,3-triazole, selected from the group consisting of a hydroxy group, a carboxyl group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group, or an alkyl or aryl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxyl group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group.

[0025] Furthermore, examples of 1,2,4-triazole derivatives that can be used as corrosion protection include those that do not have a substituent group on the nitrogen atoms forming the 1,2,4-triazole ring and that, inserted at the 2-position and / or the 5-position of the 1,2,4-triazole, have a substituent group selected from the group consisting of a sulfo group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group, or an alkyl or aryl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxyl group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group.

[0026] As described above, the cutting fluid 30, which contains an organic acid and an oxidizing agent, is supplied through the nozzles 28 for the first cutting step. Accordingly, the metal forming the electrodes 12 is modified by the organic acid contained in the cutting fluid, reducing its ductility and thus suppressing the formation of burrs. Furthermore, the surface properties of the electrode 12 are altered by the oxidizing agent contained in the cutting fluid 30, resulting in a loss of ductility for each electrode 12. This makes each electrode 12 easier to cut, thereby improving machinability.

[0027] A test was performed to determine the degree of distortion of each electrode 12 of the packaged substrate 2 in the case where the first cutting step was carried out while the cutting fluid 30 was supplied, compared with the case where the first cutting step was carried out while pure water was supplied, with reference to Fig. 6A, Fig. 6B and Fig. 7. In this test, the distance between adjacent electrodes 12 of the packaged substrate 2 was set to 100 µm. Furthermore, the feed rate during the first cutting step, while pure water was being fed, was set to 40 mm / s, and the feed rate during the first cutting step, while the cutting fluid 30, which contains an organic acid and an oxidizing agent, was being fed, was set to 100 mm / s.

[0028] Fig. Figure 6A is a sectional view of the packaged substrate 2, which was cut along division lines 8a and 8b, in the case of performing the first cutting step while pure water was supplied, and Fig. 6B is a sectional view of the packaged substrate 2, which has been cut along division lines 8a and 8b, in the case of performing the first cutting step while the cutting fluid 30, which contains an organic acid and an oxidizing agent, is supplied.

[0029] How Fig. 6A can be drawn, the degree of distortion at each electrode 12 is large and the adjacent electrodes 12 are short-circuited at a certain position in the case where the first cutting step is carried out while pure water is supplied. In contrast, in Fig. 6B observed that the degree of distortion of each electrode 12 is evidently small when the first cutting step is performed while the cutting fluid 30 is being supplied. It is assumed that this result is due to the fact that the metal of each electrode 12 is modified by the organic acid contained in the cutting fluid 30, which suppresses ductility and thus prevents the formation of burrs.

[0030] Fig. Figure 7 is a graph showing the average distance between terminals after cutting the packaged substrate 2 along the division lines 8a, in the case where pure water was supplied and in the case where the cutting fluid 30, containing an organic acid and an oxidizing agent, was supplied. Initially, the distance between adjacent electrodes 12 (terminals) of the packaged substrate 2 is set to 100 µm. Furthermore, the feed rate is set to 40 mm / s in the case where pure water is supplied in the first cutting step, and to 100 mm / s in the case where the cutting fluid 30, containing an organic acid and an oxidizing agent, is supplied in the first cutting step.

[0031] How Fig. As can be seen from Figure 7, the average distance between terminals after cutting is 38.0 µm when pure water is supplied in the first cutting step. In contrast, the average distance between terminals after cutting is 80.8 µm when the cutting fluid 30 is supplied in the first cutting step. The result that the average distance between terminals after cutting is short means that each electrode 12 was significantly elongated by the cutting process, whereas the result that the average distance between terminals after cutting is long means that the degree of distortion of each electrode 12 due to cutting is small.

[0032] Furthermore, in the case of the introduction of the cutting fluid 30 in the first cutting step, the surface properties of each electrode 12 are altered by the oxidizing agent contained in the cutting fluid 30, such that the ductility of the metal formed by each electrode 12 is lost, resulting in the effect of each electrode 12 being easily cut. Accordingly, the feed rate can be increased to 100 mm / s in this case. That is to say, it is evident that the feed rate in the case of the introduction of the cutting fluid 30 in the first cutting step is improved compared to the feed rate of 40 mm / s in the case of the introduction of pure water in the first cutting step.

[0033] After performing the first cutting step, a second cutting step is performed to cut the packaged substrate 22 along each first cut groove 32 using a second cutting blade, thereby forming a second groove that completely cuts the packaged substrate 2. Fig. Figure 5A shows a first preferred embodiment of this second cutting step. In this first preferred embodiment, which is shown in Fig. As shown in Figure 5A, the same cutting blade 26 used in the first cutting step is used as the second cutting blade to form a second cut groove 34, which completely cuts the packaged substrate 2 along the first cut groove 32 that was previously formed. That is, the packaged substrate 22 is cut along each first cut groove 32 by the cutting blade 26 in such a way that the lower edge of the cutting blade 26 enters the outlet grooves 24 of the clamping table 20 corresponding to each first cut groove 32, so that the second cut groove 34 is formed in such a way that it completely cuts the packaged substrate 2.

[0034] Fig. Figure 5B shows a second preferred embodiment of the second cutting step. In the second preferred embodiment, which is shown in Fig. As shown in Figure 5B, a cutting blade 26a, which has a smaller thickness than the cutting blade 26 used in the first cutting step, is used as the second cutting blade to form a second cut groove 36 that completely cuts the packed substrate 2 along each first cut groove 32 that was previously formed. Accordingly, the second cut groove 36, which is shown in Figure 5B, has a thickness of 26. Fig. 5B shows a width that is smaller than that of the second cut groove 34, which is in Fig. 5A is shown. As in Fig. As shown in Figure 5B, the packaged substrate 2 is cut along the center of each first cut groove 32 by the cutting blade 26A in such a way that the lower edge of the cutting blade 26A enters an outlet groove 24 of the clamping table 20 corresponding to the first cut groove 32, so that the second cut groove 36 is formed in such a way that it completely cuts the packaged substrate 22.

[0035] In each of the first and second preferred embodiments, which in Fig. 5A and Fig. As shown in Figure 5B, the packaged substrate 2 is completely cut along all the first division lines 8a extending in the first direction by moving the cutting blade 26 or 26A. Then, the clamping device holding the clamping table 20 is rotated 90° to completely cut the packaged substrate 2 along all the second division lines 8b extending in a second direction perpendicular to the first. As a result, the packaged substrate 2 can be cut into individual CSPs (chip-sized packages).

[0036] While the machining method of the present invention was applied to the packaged substrate 2 in the preferred embodiments described above, the applicability of the present invention is not limited to such a workpiece. For example, the machining method of the present invention can also be applied to a wafer having a conduction film (a multilayer metal film of Ti, Ni, or Au, for example) having a thickness of several micrometers as an electrode on a rear side, or to a wafer having a TEG at each division line formed on the front side.

[0037] Furthermore, while the cutting fluid 30 is supplied by the pair of nozzles 28 located on both sides of the cutting blade 26 in the first cutting step, any nozzle means suitable for supplying the cutting fluid 30 can be adapted in the present invention. Fig. Figure 8 is a side view of a cutting unit 25 which includes a nozzle medium suitable for applying the cutting fluid 30 according to a modification. As in Fig. As shown in Figure 8, the cutting unit 25 includes a nozzle (shower nozzle) 38 for supplying the cutting fluid 30 in addition to the cutting blade 26 and the pair of nozzles 28. The nozzle 38 is located on the front side of the cutting blade 26 in its cutting device (supply direction).

[0038] By supplying the cutting fluid 30 from the nozzle 38, the cutting fluid 30 can be easily fed to the electrodes 12, so that the metal formed on each electrode 12 is modified by the cutting fluid 30 to suppress the ductility of the metal. Accordingly, the formation of burrs can be suppressed. In particular, the nozzle opening of the nozzle 38 is preferably inclined downwards (for example, towards the working position in which the cutting blade 26 cuts the workpiece), as shown in Fig. Figure 8 shows that this configuration allows the cutting fluid 30 to be supplied more easily to the electrodes 12, so that the metal formed at each electrode 12 can be effectively modified by the cutting fluid 30. The pair of nozzles 28 and the nozzle 38 are used to deliver the cutting fluid 30 in the modification shown in Figure 8. Fig. As shown in Figure 8, only nozzle 38 can be used to supply the cutting fluid 30.

[0039] The present invention is not limited to the details of the preferred embodiments described above. The scope of the invention is defined by the appended claims.

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