JP2012192469A - Electrodeposition liquid for fixed-abrasive saw wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrodeposition liquid for a saw wire capable of being manufactured at high speed to which a large amount of abrasive grains are adhered.SOLUTION: The electrodeposition liquid for the saw wire contains 100 to 10,000 pts.mass of abrasive grains and 50 to 100 pts.mass of colloidal particles of at least one of a titanium oxide and a zirconium oxide and has the electrical conductivity of lower than 10 mS/cm.

Description

  The present invention relates to an electrodeposition solution for a fixed abrasive saw wire. When the electrodeposition liquid for fixed abrasive saw wire according to the present invention is used, hard abrasive grains such as diamond can be fixed to the surface of the metal core wire at high speed.

  When manufacturing silicon solar cells and various semiconductor devices, columnar or block material ingots made of single crystal silicon, polycrystalline silicon, amorphous silicon, sapphire, crystal, etc. are cut into wafers of desired thickness by slicing. Is done.

  A thin metal wire is used as a processing method for cutting such a hard and highly brittle material with high accuracy and low cost, and abrasive grains made of diamond or CBN (Cubic Boron Nitride) are supplied to the cut surface of the material ingot. Cutting with a free abrasive grain method is generally performed.

  However, the loose abrasive method requires a long processing time, and when cutting a large-diameter material ingot, it is difficult to supply the abrasive particles to the center of the material ingot. It was also bulky. Therefore, in recent years, development of a fixed-abrasive saw wire that can be cut at high speed without supplying loose abrasive grains by fixing abrasive grains to the outer peripheral surface of a metal wire (metal core wire) in advance has been developed. Has been tried.

  By the way, in the fixed abrasive type saw wire, the adhesiveness between the metal core wire and the abrasive greatly affects the cutting performance and durability. Therefore, various techniques have been studied in order to firmly bond the abrasive grains to the metal core wire and prevent the abrasive grains from falling off.

Patent Document 1 proposes a saw wire in which a soft plating layer and a hard plating layer are provided on a metal core wire, and abrasive grains are fixed between both plating layers.
Patent Document 2 proposes a saw wire in which abrasive grains on which a metal plating layer has been formed in advance are fixed on the metal core wire with a plating layer formed on the metal core wire.

JP-A-9-150314 JP 2006-181701 A

  However, as proposed in Patent Document 1, when a soft metal plating layer is provided between the metal core wire and the abrasive grains, the abrasive grains sink into the soft metal plating layer during the cutting process, and the metal provided thereunder There was a risk of damaging the core wire and breaking the saw wire.

  In addition, in the case of the so-called dispersion plating method in which abrasive grains dispersed in a plating solution are adhered while plating a metal core wire as in Patent Document 2, the electrical conductivity of the solution is reduced due to the plating metal salt contained in a high concentration. Therefore, the electric field strength (potential difference) in the electrolytic cell could not be increased.

  The present inventors cannot increase the electrodeposition rate of abrasive grains in a plating bath with high electrical conductivity because the speed at which the abrasive grains migrate to the surface of the metal core wire is proportional to the electric field strength (V / cm). I found. Specifically, if the plating voltage is forcibly increased, the supply of plating metal ions to the surface of the metal core wire will not be in time, causing generation of hydrogen gas on the surface of the metal core wire and poor adhesion of abrasive grains due to plating burn. For this reason, there is a limit to the plating voltage that can be applied, and there is also a limit to the electrodeposition speed of the abrasive grains. Therefore, for example, the conventional dispersion plating method as in Patent Document 2 has found that the electrodeposition rate of the abrasive grains on the saw wire has an essential limit.

  Then, an object of this invention is to provide the electrodeposition liquid for saw wires which can manufacture the saw wire to which many abrasive grains adhered at high speed.

In order to achieve the above object, the present invention provides the following.
(1) It contains 100 to 10000 parts by mass of abrasive grains, 50 to 100 parts by mass of at least one colloidal particle of titanium oxide or zirconium oxide, and has an electrical conductivity of less than 10 mS / cm. Characteristic electrodeposition solution for saw wire.
(2) The electrodeposition liquid for saw wire according to (1),
It contains a water-soluble phosphorus compound.
(3) The electrodeposition liquid for saw wire according to (1) or (2), wherein the pH is 5 or more and 10 or less.
(4) The electrodeposition liquid for saw wire according to any one of (1) to (3), wherein the colloidal particles have a negative charge.

  According to the electrodeposition liquid for saw wire according to the present invention, by applying a voltage between the metal core wire of the saw wire and the electrodeposition tank storing the electrodeposition liquid for saw wire, the charged colloidal particles are converted into the metal core wire. Precipitates on the surface. At the same time, colloidal particles adhering to the abrasive grains are pulled to the metal core wire, and colloidal particles heading toward the metal core wire press the abrasive grains, so that the abrasive grains adhere to the surface of the metal core wire, and colloidal particles precipitated at the same time A metal oxide layer is formed and the abrasive grains are fixed to the surface of the metal core wire. At this time, since the electric conductivity of the electrodeposition liquid for saw wire is set to be relatively low, less than 10 mS / cm, almost no side reactions such as metal elution and gas generation occur even when a high electric field strength is applied. Colloidal particles and abrasive grains can be electrodeposited on the metal core wire without causing it. Moreover, the dispersibility of colloidal particles and abrasive grains is excellent due to the low electrical conductivity, and the bath liquid can be managed in a more stable state.

  The inventors have made a mixed solution in which abrasive grains are mixed in a solution obtained by charging and dispersing each of oxides or hydrated oxide particles of Ti or Zr as an electrodeposition solution for saw wire, and for this saw wire. When a metal core wire is immersed in an electrodeposition solution and a voltage is applied to the metal core wire, the abrasive grains are found to precipitate as a metal oxide at high speed on the surface of the metal core wire together with an oxide or hydrated oxide of Ti or Zr, The present invention has been reached. In addition, it is found that the addition of water-soluble phosphorus compounds such as phosphoric acid and condensed phosphoric acid is effective for the dispersion and precipitation of colloidal particles. It was found that the composition ratio of abrasive grains and colloidal particles affects the adhesion.

  The electrodeposition liquid for saw wire according to the present invention comprises 50 parts by mass or more and 100 parts by mass or less of water as a medium and at least one of titanium oxide colloidal particles or zirconium oxide colloidal particles (hereinafter also simply referred to as colloidal particles). It contains a colloidal dispersion and 100 to 10000 parts by mass of diamond, CBN (Cubic Boron Nitride) and other abrasive grains.

  As the kind of titanium oxide used in the present invention, anatase type titanium dioxide (including metatitanic acid) and orthotitanic acid (amorphous) are preferable. Moreover, you may use other titanium dioxides, such as a rutile type. Zirconium oxide is not particularly limited, but is preferably amorphous or crystalline such as monoclinic or cubic.

  These colloidal particles are dissolved in water by dissolving an inorganic titanium compound such as titanium chloride, titanium oxychloride, titanium sulfate and titanyl sulfate, and added with a catalyst such as hydrochloric acid or nitric acid as necessary, and then hydrolyzed at room temperature or by heating. Can be obtained. Alternatively, it can be obtained by hydrolysis of an organic titanium compound such as titanium alkoxide or titanium acetylacetonate.

  Further, as raw materials for the zirconium oxide particles, zirconium oxychloride, zirconyl sulfate, zirconium carbonate, zirconium alkoxide, crystalline zirconium oxide sol, and the like can be used, but are not limited to these raw materials.

  Thus, the titanium oxide colloidal particles or zirconium oxide particles obtained in the acidic solution are positively charged. However, the colloidal particles used in the saw wire electrodeposition liquid of the present invention are preferably negatively charged in an acidic to neutral colloidal dispersion. This is because when these colloidal particles are positively charged in an acidic to neutral colloidal dispersion, the colloidal particles aggregate and the dispersion becomes unstable.

Therefore, an alkaline component is added to the above acidic colloidal dispersion to make the pH of the colloidal dispersion 5 or higher, and a water-soluble phosphorus compound is added to negatively charge titanium oxide particles or zirconium oxide particles. Is preferred.

As the water-soluble phosphorus compound, phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid or an alkali salt thereof can be used, and a preferable concentration thereof is 1 part by mass or more and 20 parts by mass or less. The water-soluble phosphorus compound dissolves in water to become negative phosphate ions (PO ₄ ³⁻ ), and the phosphate ions adhere to the colloid particles to increase the negative charge of the colloid particles (increase the repulsive force between colloid particles) ), Colloidal particles can be stably dispersed in the colloidal dispersion. The sign of the colloidal particles can be easily measured by a zeta potential measuring device or the like. In the saw wire electrodeposition liquid according to the present invention, the colloidal particles are preferably charged at a potential of -50 mV or less.

  Moreover, as an alkaline component added in order to make pH of a colloid dispersion liquid 5 or more, it is preferable to contain the at least 1 sort (s) of alkaline component chosen from ammonium compound, an alkali metal compound, and amines. The ammonium compound is ammonium hydroxide (ammonia water), the alkali metal compound is sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium silicate, the alkali component selected from amines is ethylenediamine, triethylenetetramine, etc. Examples of such polyamines can be given.

  In addition, as a water-soluble phosphorus compound and an alkaline component, for example, a phosphorus compound that stably disperses colloidal particles, such as ammonium pyrophosphate and ammonium lactate, and a compound that is also an alkaline component that makes the colloid dispersion liquid alkaline are used. You can also

  By adding such an alkali component to the acidic colloidal dispersion, acidic ions such as hydrochloric acid ions and sulfate ions remaining in the colloidal dispersion can be neutralized to adjust the pH to 5 or more. . The pH of the colloidal dispersion is preferably adjusted in the range of 5 or more and 10 or less. If the pH is less than 5, the colloidal particles cannot be uniformly dispersed in the colloidal dispersion. On the other hand, if the pH is higher than 10, the metal core wire is dissolved in the step of attaching abrasive grains to the metal core wire, which is not preferable. In addition, it is preferable that 1 to 50 mass parts is added for the alkaline component to add.

  The particle diameter of the colloidal particles is preferably 1 nm to 500 nm, and more preferably 3 nm to 120 nm. This is because when the colloidal particles are too small, the colloidal particles are likely to aggregate over time and the amount of precipitation is not stable, and when the colloidal particles are too large, the colloidal particles are likely to precipitate. By treating the colloidal dispersion with a stirrer such as a homomixer for a predetermined time, colloidal particles having a desired particle size can be obtained.

  Further, the electric conductivity of the colloidal dispersion is preferably greater than 0 and less than 10 mS / cm, and a more preferable range is 0.05 mS / cm or more and 5 mS / cm or less. Thus, by setting the electrical conductivity of the colloidal dispersion to a relatively low value, a large amount of colloidal particles can be stably dispersed, and many abrasive grains can be quickly attached to the metal core wire. it can.

  If the electrical conductivity is less than 0.05 mS / cm, it may be difficult to stably control the amount of titanium oxide or zirconium oxide deposited due to impurities in the colloidal dispersion. On the other hand, if it is greater than 10 mS / cm, the amount of elution of the metal core wire into the electrodeposition liquid for saw wire increases, such being undesirable. The electrical conductivity can be lowered by performing a desalting treatment such as bringing the colloidal dispersion into contact with pure water through an ion exchange membrane. When the electrical conductivity is too high, the electrical conductivity can be lowered by dialysis or auto draining the supernatant of the colloidal dispersion.

  The electrodeposition liquid for saw wire of the present invention can be obtained by mixing abrasive grains having an average particle diameter of 1 to 60 μm made of diamond, CBN (Cubic Boron Nitride), etc. into the colloidal dispersion prepared as described above. can get. In addition, when the average particle diameter of the abrasive grains 20 to be added is less than 1 μm, the cutting performance of the obtained saw wire is insufficient, and when the average particle diameter is more than 60 μm, it is difficult to adhere to the metal core wire.

  In addition, as other components contained in the electrodeposition liquid for saw wire, depending on the titanium raw material used, chlorine ions, sulfate ions, alcohols and the like are included, but the remaining components are substantially made of water. When colloidal particles made of titanium dioxide are used, a part of water may be replaced with a water-soluble solvent such as alcohol, glycol, glycol ether or ketone as an auxiliary solvent. In this case, a silane derivative such as silica sol or alkyltrimethoxysilane may be added as a binder to improve the coating properties such as hardness and wear resistance of the metal oxide layer formed on the surface of the metal core wire.

  When the metal core wire is immersed in the electrodeposition bath filled with the electrodeposition solution for saw wire prepared as described above, and a voltage is applied between the metal core wire and the electrodeposition bath, the charged colloidal particles become the metal core wire. The colloidal particles are deposited on the surface of the metal core wire to form a metal oxide layer. In addition, during the process of colloidal particle precipitation, the abrasive grains also adhere to the surface of the metal core wire, and the attached abrasive grains are fixed to the surface of the metal core wire by the metal oxide layer. It is thought that the abrasive grains adhere to the metal core wire when the colloidal particles are attracted to the metal core wire or the colloid particles adhering to the abrasive grain are attracted to the metal core wire in the process in which the colloid particles are attracted to the metal core wire. .

  At this time, the electric conductivity of the electrodeposition liquid for saw wire according to the present invention is set to a low value of 10 mS / cm or less, and since there are few ions in the electrodeposition liquid for saw wire, a large number of colloidal particles bind to the ions. Since the electrodeposition liquid is stably dispersed in the electrodeposition liquid, the electrodeposition liquid for saw wire can be managed in a stable state. When an electric field is applied to such a saw wire electrodeposition solution, the colloidal particles start electrophoresis at a high speed, and the abrasive grains together with the colloidal particles are quickly charged by transporting the mixed abrasive grains to the surface of the saw wire. Worn. In addition, since there are few ions in the electrodeposition solution for saw wire, colloidal particles and abrasive grains can be rapidly turned into a metal core wire without causing side reactions such as metal elution and gas generation even when high electric field strength is applied. Electrodeposition can be performed.

  Hereinafter, specific examples will be described. In addition, the electrodeposition liquid for saw wires of this invention is not limited to a following example.

(Pretreatment process of metal core wire)
Using brass-plated steel wire (metal core wire) with a diameter of 0.13 mm as a pretreatment, using an alkali degreasing solution (FC-4360, manufactured by Nippon Parkerizing Co., Ltd.), alkali degreasing at 60 ° C. for 60 seconds and then washing with water, Further, pickling was performed with a 0.1 mol / L sulfuric acid solution at room temperature for 10 seconds.

Next, the electrodeposition solutions for saw wires of Examples 1 to 5 and Comparative Examples 1 to 3 prepared as shown in Table 1 were prepared. The TiO ₂ colloid dispersion and the ZrO ₂ colloid dispersion were prepared as follows.

(Preparation of colloidal dispersion)
TiO ₂ colloid dispersion In Comparative Examples 1 and 2 and Examples 1 to 3, titanium oxide colloids were prepared by the following method. 154 g of titanium chloride aqueous solution (Ti: 15-16 mass %, manufactured by Sumitomo Sitix Co., Ltd.) is diluted with 500 mL of pure water and brought into contact with pure water through an anion exchange membrane at room temperature for 7 hours to remove the anion component (salt chloride). An acidic amorphous titanium oxide colloidal dispersion was prepared by deionization treatment to reduce product ions). In this state, the titanium oxide colloidal particles are positively charged.

  Further, 2.4 g of polyphosphoric acid as a neutral to alkaline and effective dispersant was added to the colloidal dispersion diluted with pure water, and immediately after that, morpholine was added to raise the pH to about 8. Further, the colloidal particles were dispersed for 15 minutes with a homomixer, transferred to an ultrafiltration membrane, and deionized water was fed while supplying deionized water until the electric conductivity of the colloidal dispersion became 10 mS / cm or less.

  At this time, the dispersed particle size of the titanium oxide colloidal particles measured by the laser type particle size distribution measuring apparatus was 0.005 μm or more and 0.01 μm or less. Further, the concentration of the titanium oxide colloidal particles was 4% by mass by dry weight.

ZrO ₂ colloidal dispersion In Comparative Example 3 and Examples 4 and 5, a zirconium oxide colloidal dispersion was prepared as follows. Zirconium oxide sol (pH 7.7 ZSL10A, manufactured by Daiichi Kagaku Kagaku Kogyo Co., Ltd.) was diluted with pure water to obtain a 4 mass% zirconium oxide colloidal dispersion. The addition of the dispersant, the addition of the water-soluble phosphorus compound, and the desalting treatment were prepared in the same manner as the above-described titanium oxide colloid dispersion.

  Table 1 shows diamond particles having an average particle diameter of 10 μm in Comparative Examples 1 and 2 and Examples 1 to 3 as abrasive grains in the titanium oxide colloidal dispersion and zirconia colloidal dispersion prepared as described above. It added so that it might become a density | concentration, and in the comparative example 3 and Example 4, 5, the diamond particle with an average particle diameter of 5 micrometers was added so that it might become the density | concentration shown in Table 1, and the electrodeposition liquid for saw wires was obtained.

(Evaluation of electrodeposition solution for saw wire)
Using the electrodeposition liquid for saw wires according to Examples 1 to 5 and Comparative Examples 1 to 3 prepared as described above, saw wires were prepared by the following method, and the performance of the prepared saw wires was evaluated.

(Creation of saw wire)
The electrodeposition bath is filled with the electrodeposition solution for saw wires according to Examples 1 to 5 and Comparative Examples 1 to 3, and the steel wire subjected to the pretreatment step is immersed in the electrodeposition solution while being fed by the power supply roller and the submerged roller. Let The power supply roller is a roller for applying a voltage to the metal core wire, and is provided above the surface of the saw wire electrodeposition liquid and connected to the power supply unit. The submerged roller is provided in the electrodeposition tank and is a roller for immersing the metal core wire in the electrodeposition liquid. In addition, an electrode plate made of SUS304 is provided inside the electrodeposition tank in parallel with the conveying direction of the steel wire.

  The feed roller is connected to the negative electrode, the electrode plate of the electrodeposition tank is connected to the positive electrode, and while applying a voltage of 20 V between them, the steel wire is fed so that the steel wire is immersed in the electrodeposition tank for 1 second, colloidal particles At the same time, the abrasive grains were fixed to the steel wire to obtain a saw wire.

  Further, the obtained saw wire was put in a drying furnace having an in-furnace temperature of 150 ° C. for 60 seconds and dried by heating, the precipitated titanium oxide or zirconium oxide was dehydrated and condensed, and the abrasive grains were firmly fixed to the metal core wire.

Furthermore, a nickel plating layer was formed as a protective layer on the metal core wire to which the abrasive grains were fixed by electrolytic plating. As a plating solution, pure water, 200 g / L nickel sulfamate, 30 g / L nickel chloride hexahydrate, and 30 g / L boric acid are prepared, and a nickel plating solution containing no abrasive grains is prepared. did. Electroplating was performed at a current density of about 20 A / dm ² so that the thickness of the protective layer did not exceed the average particle diameter of the diamond abrasive grains while adjusting the plating solution to pH 4 to 5 and maintaining the temperature at 55 ° C. . Since the plating solution deteriorates when the colloidal particles are eluted in the plating solution, it is preferable to fix the colloidal particles to the metal core wire by dehydrating and condensing the colloidal particles by the aforementioned drying step.

(Evaluation of saw wire)
The saw wire obtained as described above was evaluated for the amount of adhered abrasive grains, the adhesion, and the maximum cutting speed of the workpiece. The results are shown in Table 2.

The adhesion density of the abrasive grains is obtained by enlarging the surfaces of the saw wires of Examples 1 to 5 and Comparative Examples 1 to 3 with a scanning electron microscope (SEM) and visually confirming the number of abrasive grains in the field of view. . Arbitrary 10 points on the saw wire were observed and evaluated as A if 100 or more per 1 mm ² , B if 40 or more and less than 100, C if 1 or more and less than 40, and D if less than 1.

  The maximum cutting speed of the workpiece was performed in order to evaluate the performance as an actual saw wire. The saw wires of Examples 1 to 5 and Comparative Examples 1 to 3 are cut to a length of 50 m, attached to a saw wire cutting tester with a tension of 30 N, and the saw wire is fed at a feed rate of 60 m / min. While cutting the silicon single crystal workpiece, the maximum feed rate of the workpiece was measured. The maximum feed rate was measured as the feed rate immediately before the saw wire was disconnected, while gradually increasing the workpiece feed rate.

  Also, the adhesiveness of the abrasive grains is that the saw wire created under the above conditions is subjected to a cold drawing process of about 15% using a drawing die, and the abrasive grains are driven into the plating layer of the saw wire and fall off. A circle was evaluated when no trace was observed, and a circle was marked when omission was observed.

  First, when comparing the amount of abrasive grains of Examples 1 to 5 and Comparative Examples 1 to 3, the saw wire of Examples 1 to 5 has a larger amount of abrasive grains than the saw wires of Comparative Examples 1 to 3. It was confirmed that In all of Examples 1 to 5 and Comparative Examples 1 to 3, the metal core wires were dipped in the electrodeposition liquid for saw wire, but the adhesion density of the abrasive grains of Examples 1 to 5 was large. From this, it was found that the abrasive grains can be more efficiently fixed to the metal core wire by using the electrodeposition liquid for saw wire used in Examples 1 to 5. Therefore, it was confirmed that the saw wire production rate can be improved by the saw wire electrodeposition liquid according to the present invention.

  Moreover, when Examples 1 and 2 and Comparative Example 2 are compared, although Comparative Example 2 has the highest concentration of abrasive grains in the electrodeposition liquid for saw wire, Examples 1 and 2 are more than Comparative Example 2. Excellent results were obtained at the abrasive grain adhesion density and maximum cutting speed. Since the larger the maximum cutting speed, the more abrasive grains were attached to the saw wire, the smaller the electrical conductivity than the abrasive concentration in the saw wire electrodeposition liquid, It was confirmed that the effect on the ease of adhesion of grains was great.

  Therefore, if the electrodeposition liquid for saw wire according to the present invention is used, high-quality saw wire can be manufactured at high speed without adding a large amount of abrasive grains to the processing liquid, thereby reducing the cost and processing time of the processing liquid. It is possible to provide a high-quality saw wire at a low cost.

Claims (4)

  100 parts by weight or more and 10000 parts by weight or less of abrasive grains, 50 parts by weight or more and 100 parts by weight or less of at least one colloidal particle of titanium oxide or zirconium oxide, and an electrical conductivity of less than 10 mS / cm Electrodeposition solution for saw wire.   2. The electrodeposition liquid for saw wire according to claim 1, comprising a water-soluble phosphorus compound.   The electrodeposition liquid for saw wire according to claim 1 or 2, wherein the pH is 5 or more and 10 or less.   The said colloidal particle has a negative charge, The electrodeposition liquid for saw wires as described in any one of Claim 1 to 3 characterized by the above-mentioned.