JPS63229253A - Polishing method - Google Patents

Abstract

PURPOSE:To carry out a stable polishing operation by holding abrasive grains by means of the surface tension or adhesion of a liquid and reducing the liquid content of a compression molded liquid-bond grinding wheel, making a liquid stay on a surface, and pressing a material to be polished against it to carry out polishing. CONSTITUTION:The mixing ratio between abrasive grains and liquid is optionally set so as to obtain a convenient condition for the operations of mixing, compression, molding, etc., and this mixture is compression molded and treated to reduce the contained liquid, increasing the physical strength to obtain an effective liquid-bond grinding wheel. This liquid-bond grinding wheel is mounted on a polishing device, a liquid is sprayed or poured on its surface to make the liquid stay on the surface, and a material to be polished is pressed against it and made relatively slide. Thereupon, the liquid penetrates the fine spaces of the abrasive grains and, finally, the liquid is stopped on a face including the mutual contact points of the abrasive grains, providing a funicular zone in which the liquid continuously exists. Hence, by adjusting the quantity of liquid which is fed to the surface, a most favorable mixing condition can be set, enabling a stable polishing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polishing method for precisely polishing a material to be polished such as a hard brittle material, a metal material, or a synthetic resin material.

<Conventional technology> Liquid bond grinding wheels are made by adding a small amount of liquid to abrasive grains, mixing them uniformly, placing them in a mold, and compressing them.This liquid bond grinding wheel can be used to grind hard and brittle materials, metal materials, and synthetic materials. The technology for precisely polishing materials to be polished such as resin materials is described in R. Tani and Kawaguchi, "Development of a high-efficiency polishing method using a liquid bond grindstone," Japan Society of Mechanical Engineers Paper 15 (No. 1471, 1986-113). r
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Kawaguchi, "Development of a high-efficiency polishing method using liquid bond grinding wheels" Production Research Vol. 37, No. 7, 1985, 73, R. Kawaguchi, "Application of liquid bond grinding wheels to interface polishing" 1985 Japan Society of Precision Machinery Autumn Conference Academic Tani, Kawaguchi, ``High-Efficiency Polishing of Silicon Wafers Using Liquid Bond Grinding Stones,'' published in Proceedings of the 1985 Precision Engineering Spring Conference Academic Conference Proceedings J.

(Problems to be Solved by the Invention) However, the method described in the above-mentioned literature sets the mixing ratio of abrasive grains and liquid to be between the Pendler region and the funicular region, and performs mixing and compression. , when performing operations such as molding, the fluidity of the mixture is poor because the mixing ratio of the liquid is small, and it is difficult to mix the abrasive grains and the liquid uniformly, resulting in non-uniformity. If compression molding is performed in a non-uniform mixed state, the density and hardness of the molded whetstone will vary, leading to partial collapse of the whetstone during polishing and uneven polishing results.

The mixing ratio of abrasive grains and liquid between the Pendler region and the funicular region is not constant because it varies depending on the type of abrasive grains and liquid, the particle size and shape of the abrasive grains, etc., but it is generally The proportion of liquid that occupies the abrasive grains is much smaller than that of the abrasive grains, usually only about 20% of the abrasive grains.For this reason, the liquid that makes up the liquid pound grinding wheel is a liquid that evaporates more easily than this liquid. A method has also been proposed in which the diluted liquid is mixed with abrasive grains in excess, and then the excess liquid is removed by evaporation. However, since this diluting liquid uses hexane or alcohol, it is highly flammable and highly toxic, and special care must be taken when handling it.

Furthermore, even if the abrasive grains and liquid are mixed at an appropriate and uniform ratio, the liquid used in the liquid pound grinding wheel has the property of evaporating if left alone, such as water or oil. Because of this, molded liquid pound abrasive wheels have poor storage stability, and if the mixture of abrasive grains and liquid is not polished immediately after molding, the abrasive grains and liquid will evaporate over time due to evaporation of the liquid. As a result, the polishing conditions vary depending on the polishing process, making it difficult to maintain constant polishing efficiency and precision.

In addition, since the binding medium of the abrasive grains in a liquid pound wheel is liquid, it lacks physical strength even when compression molded, and will collapse if the material to be polished is pressed too hard. The liquid pound grinding wheel is easily damaged when it is fixed to a device, and therefore, the liquid pound grindstone must always be carried while being housed in a strong container or fixed to the device for polishing, resulting in extremely poor workability.

Furthermore, during the polishing process using a liquid pound grinding wheel, in order to suppress the temperature rise of the polished material due to the frictional heat of processing and to remove the chips that adhere to the surface of the liquid pound grinding wheel, Flushing or spraying with water or other cooling liquid is desirable, but is not easily implemented as it softens and accelerates the wear of the liquid pound wheel, often causing it to collapse.

Means for Solving the Problems The present invention was proposed in view of the above, and involves mixing abrasive grains and a liquid so that the liquid exists between the abrasive grains, and using the surface tension or adhesive force of the liquid to bind the abrasive grains. A liquid pound grinding wheel formed by holding and compression molding has a reduced amount of liquid gold, and a liquid is present on the surface of the liquid pound grinding wheel so that the material to be polished is polished while being pressed. It is.

The abrasive grains of the liquid pound wheel used in the polishing method of the present invention include diamond, corundum, emery, garnet,
Silica stone, tripoli, calcined dolomite, fused alumina, artificial emery, silicon carbide, boron carbide, iron oxide, calcined alumina, chromium oxide, cerium oxide, zirconium oxide, magnesium oxide, calcium carbonate, magnesium carbonate,
Any abrasive grains that can be used as ordinary abrasive grains, such as silica and shirasu, may be used, and the abrasive grains used have a particle size of approximately 30 gm or less.

Further, the liquid of the liquid pound grindstone used in the polishing method of the present invention includes water, an alkaline solution, an acid solution, an aqueous solution of many other salts, a polymer solution, an oily liquid, a magnetic fluid, and the like.

Effect> The mixing ratio of abrasive grains and liquid when forming the liquid pound grindstone of the present invention can be arbitrarily set so as to be in a state convenient for operations such as mixing, compression, and forming. When mixing abrasive grains and liquid, there is generally an excess of liquid over the abrasive grains in order to provide fluidity, but even if there is an excess of liquid, drying or other processing can remove the liquid. This reduces the content. Therefore, the mixing ratio of abrasive grains and liquid does not need to be particularly considered at the stage before molding, so this mixing process is easy and does not cause uneven density or hardness of the molded product. In order to increase the fluidity of the mixture, the mixture is granulated to an appropriate size and the pressure is 1i! When molded, the density and hardness of the molded product become more uniform. When performing the granulation operation, the mixing ratio of the liquid and the abrasive grains can be set to a state convenient for the granulation operation.

As described above, after the abrasive grains and liquid are mixed at a mixing ratio that is optimal for molding, this mixture is compression molded. The pressure required for this compression molding is approximately 100 kg/cm2 or more, preferably 300 kg/cm2 or more.

After the mixture of abrasive grains and liquid is compression molded as described above, the liquid contained in this molded product is subjected to a reduction treatment. This liquid can be reduced by drying or by contacting it with a liquid-absorbing agent, but this treatment can be carried out before compression molding, or if granulation is added, the granulated mixture can be used during granulation. You can also do this for

In this way, reducing the liquid contained in the molded product increases its physical strength, so that it does not easily collapse or break even when the material to be polished is pressed hard, and it becomes easier to transport and attach to polishing equipment. , making it an effective liquid pound grinding wheel.

When the liquid content of the above-mentioned molded product decreases and the mixing state of the liquid with the abrasive grains reaches the lower limit of the Pendler region, most of the contained liquid is adsorbed on the surface of the abrasive grains. Since the adsorbent liquid does not easily evaporate, the molded product can be stored for a long period of time, and the liquid content hardly changes over time, resulting in extremely good stability.

The physical strength of the molded product described above varies depending on the type of abrasive grains and liquid, but if the strength of the molded product obtained by the above molding method is still insufficient, it is necessary to In addition, a component (hereinafter referred to as an additive component) that can be easily dissolved or mixed in the liquid and has a function of fixing the abrasive grains together when the concentration in the liquid is high can also be added. This added ingredient is
The abrasive particles are concentrated by the drying process of the molded product as described above, and the abrasive grains are firmly attached to each other, thereby significantly increasing the physical strength of the molded product.

Even if a liquid is sprayed onto the surface of the material to be polished during the polishing process, the above-mentioned additive components easily dissolve or swell upon contact with or mixing with the liquid, resulting in a state close to that of the liquid before drying. For example, if the liquid to be sprayed is water, water glass or a water-soluble polymeric organic substance is effective as the additive component; if the liquid to be sprayed is oil, the additive component is oil. Soluble polymeric organics can be used.

However, when heating and drying a molded product to reduce the liquid content, the above-mentioned additive components may thermally polymerize depending on the type, and when the liquid is sprayed or poured during the next polishing process, they easily return to the state before drying. Sometimes it doesn't come back. Therefore, it is necessary to be careful in selecting the additive components and setting the heat drying treatment conditions, and after mixing and molding the abrasive grains and liquid,
It is also better not to use additive components that deteriorate over time and cause changes in the rate of dissolution, swelling, mixing, etc. in liquids.

However, even if there is deterioration in the additive component, it may be possible to carry out the process as long as the degree of deterioration does not adversely affect the liquid pound grinding wheel.For example, if a water-soluble polymeric organic material is used as the additive component, When the organic substance becomes water-insoluble due to polymerization due to heating, the present invention can be carried out by using a solvent that dissolves the water-insoluble substance as a liquid to be sprayed or flowed during polishing. Also,
Excessive amounts of additive components are undesirable as they may cause the following drawbacks.In other words, in order to quickly liquefy the additive components, a large amount of creating the need to spray liquid;
This is because the mixing state of the abrasive grains and liquid of the liquid pound grindstone has saturability exceeding the funicular region.

Therefore, although the amount of the additive component varies depending on the type of abrasive grains, liquid, and additive component, it is generally 1iII% or less based on the abrasive grains.

The molded product formed as described above, that is, the liquid pound grinding wheel, is attached to a polishing device and left there while spraying or pouring liquid onto the surface, and presses the material to be polished to separate the liquid pound grinding wheel and the material to be polished. slide relative to each other. As a result, the liquid permeates into the fine spaces between the abrasive grains of the liquid pound grinding wheel, and the mixed state of the abrasive grains and the liquid is such that the liquid adheres in an annular shape around the contact points between the abrasive grains. It is a continuous state. This state is in the Pendler region, but when the liquid is further sprayed or poured onto the surface of the liquid pound grinding wheel, the liquid closes on the surface that includes the contact points between the abrasive grains, and the liquid is continuously present in the funicular region. Convert to area. Therefore, when adjusting the amount of liquid supplied to the surface of the liquid pound grinding wheel,
The most preferable mixing state of abrasive grains and liquid for a liquid pound grindstone can be set. In addition, even if a molded product for a liquid bond grindstone is stored for a long time without being used for polishing, the liquid content does not change significantly, so the amount of liquid supplied to the surface of the liquid bond grindstone remains constant. It depends on the stable polishing process.

Further, since the liquid supplied to the surface of the liquid pound grinding wheel is sprayed or poured, the conversion from the Pendler region to the funicular region of the liquid pound grinding wheel starts from the surface of the liquid pound grinding wheel and gradually moves to the inside. In other words, during polishing, the liquid pound wheel remains in a state with a large amount of liquid on its surface, which suppresses the temperature rise due to frictional heat on the surface of the liquid pound wheel that comes into contact with the material to be polished, and reduces the discharge of cutting debris. However, since the inside of the liquid pound grinding wheel remains in a state where there is less liquid compared to the surface area, the physical strength of the liquid pound grinding wheel as a whole increases. It does not collapse even when polished under a pressure of about 112 g/c, and can be efficiently polished under high processing pressure.

<Example> The present invention will be explained in detail below.

Example 1 A paste-like mixture made by sufficiently stirring and mixing IKg of abrasive grains GS3000 and 2Kg of a mixed aqueous solution of starch and urethane was poured into a mold.This paste-like mixture had the following properties in the mixed state of the abrasive grains and liquid: The amount of liquid is significantly large and there is almost no air phase, so it is well beyond the funicular region. When the mixture was force dried at 60° C. for 12 hours, the liquid content decreased to 17% and the mixture contained continuous and discontinuous air phases, resulting in a liquid pound wheel.

When measuring the physical properties of the liquid pound grinding wheel obtained in this way,
Hardness: 72, bending strength: 0.1kg/7cm2 or less, compressive strength: 0.1kg/c+*2 or less.

When this liquid pound grindstone is further force-dried at 60°C for 24 hours, it has a hardness of 80 and a bending strength of 4 kg/cm2. The compressive strength was 7 kg/cm2, and the physical strength was significantly improved.

Example 2 Grinding wheel grains [43000] and a liquid 5% CMC aqueous solution were mixed at a weight ratio of 1:0.9, filled into a mold container, and molded at a pressure of 12I using a compression molding machine to form a liquid pound wheel with a thickness of about IG mm. And so. Compressive load at this time: 200-300 Kg/c+*
2. The compression ratio was approximately 3.3. When the obtained liquid pound grindstone was taken out of the mold container, it was in a state of extremely poor physical strength, so that it would crumble just by lifting it by hand, and when its physical properties were measured.

Hardness: 90, bending strength: 0. , IKg/c+*2 or less,
The compressive strength was 0.1 kg/c theory 2 or less.

When the liquid pound grinding wheel prepared in the same manner as above is removed from the mold container and dried to reduce the liquid content to about 5% of the weight of the grinding wheel, the physical strength of the molded product is significantly improved.
Hardness 98, bending strength 10Kg/cm2, compressive strength 20
Kg/cm2, and it did not chip or crumble even when carried or set in a polishing machine. In this dry molded product, there are almost no volatile components in the liquid that makes up the liquid pound grinding wheel, so when the abrasive grains and liquid are mixed, only the non-volatile components reach the point of contact between the abrasive grains. A state where it is slightly attached and remains in the center,
In other words, it is considered to form the lower limit of the Pendler range.

Next, on the surface of the dried molded product, molded product surface 1c112
When approximately 0.02+ sl of water was sprayed per area, the surface softened and the area at a depth of 1 cm or more from the surface could be easily scraped off with a knife, etc.
No softening was observed in areas above +sm.

As the water spraying continued, the softened layer of the molded product became deeper, and at a spray rate of about 1.81 per cm 2 of the molded product's surface, the depth of the softened layer reached the bottom of the molded product. When the physical properties of this softened molded product were measured, the hardness was 91, the bending strength was 0.1Kg/c, 2 or less, and the compressive strength was 7Kg.
cm2 or less, which was the physical property of a liquid pound grindstone before drying.

Example 3 90 ml of liquid 30% acrylic emulsion solution was added dropwise to 1.0 kg of Q13000 abrasive grains, and mixed and granulated using a mixing granulator to a particle size of about 50 to 250 p, m. The mixed granules were supplied to a compression molding machine and compression molded to form a liquid pound grindstone. The liquid content of this liquid pound grinding wheel is 20%, the hardness is 871, and the bending strength is 0.
1Kg 7cm2 or less, compressive strength 0.1Kg/cm
2 or less, but when this was stored indoors for 3 weeks, the liquid content was 3.6%, the hardness was 93, and the bending strength was 10 kg/
cs+2, the compressive strength was 22 Kg/cm2, and the liquid content and physical properties changed significantly.

On the other hand, a liquid pound grindstone that had been compression molded in the same manner as above was placed in a heating machine at 70°C, and the molded product was forced to dry for 12 hours.The liquid content of the molded product was 2.8%, the hardness was 99, the bending strength was 15, The compressive strength was 30, but after storing this molded product indoors for 3 weeks, the results of ° measurement showed that the liquid content and physical properties did not change at all from immediately after drying, indicating that it had excellent storage stability.

Example 4 Abrasive grain WAII3000. While dropping a xylene solution 1501 in which 25 g of petroleum resin is dissolved as a liquid to I Kg, the mixture is mixed and granulated using a mixing granulator, and then supplied to a compression molding machine at a load of 350 to 400 Kg/cm2 and a compression ratio of 2. .7 to form a liquid pound grindstone. When we measured the hardness of this liquid pound whetstone, there was a large variation in hardness depending on the measurement location on the whetstone surface, with the lowest value being 72,
The highest value was 77 and the average value was 73.

On the other hand, while dropping 18h+ of a xylene solution in which 25g of petroleum resin was dissolved into the abrasive grains WA Cloud 3000 and IKg, the mixture was mixed and granulated using a mixing granulator, and the mixture was granulated using a compression molding machine as above. It was molded at a compression ratio of 2.5 at a weight of 400 kg/c 2 to form a liquid pound grindstone. This liquid pound grindstone was once heated and dried to reduce the liquid content to 5% or less, and then 30 ml of xylene containing no petroleum resin was poured onto the surface of the dried product to return it to the original liquid pound grindstone. The hardness of this liquid pound grinding wheel has almost no variation no matter where it is measured on the grinding wheel surface, with a minimum value of 74.
．． The highest value was 75 and the average value was 74.5.

Example 5 While dropping a 45% acrylic emulsion solution and a 3% starch solution as liquids onto Q Cloud 3000 as abrasive grains, they were mixed and granulated using a mixing granulator, and the mixed granules were placed in a mold container. Fill it and supply it to the compression molding machine, and the load is 400 ~
500Kg/c+w2, compression ratio 2.1te pressure 1i! It was molded into a liquid pound grindstone. Next, the mold container containing the liquid pound grinding wheel was placed on the rotary table of a flat lapping machine, the sliced silicone wafer surface was pressed against the grinding wheel surface, and pure water was added at a rate of 10 m1/sin.
! The grinding wheel was continuously sprayed on the surface while sliding. The machining efficiency at a machining load of 3 kg and a relative rotational speed of 30 m/win was 3 uL/sin, and the amount of wear of the liquid pound grinding wheel during a total polishing time of 20 in was 7 mm.Continuing to polish silicone wafers, the polishing process was completed by 26 m1n. At some point in time, the liquid pound grinding wheel collapsed and it became impossible to continue grinding.

On the other hand, the liquid pound grindstone prepared in the same manner as above was taken out from the mold, placed in a heating machine, and forcedly dried at 50° C. for 24 hours. This dry molded product was glued onto a flat lapping machine, the sliced silicone wafer surface was pushed onto the molded product surface, and the surface of the dry molded product was slid while continuously spraying pure water onto the grindstone surface at a rate of 15 m1/sin. I let it happen. When polishing was performed under the same polishing conditions as above, the processing efficiency was 3g/wi
However, the wear rate of the whetstone remained at 0.6 mm in a total polishing time of 20 m1n, and the whetstone did not collapse even after 35 m1n of continuous polishing.

Claims (3)

[Claims] (1) Mixing abrasive grains and a liquid so that the liquid exists between the abrasive grains, and holding the abrasive grains by the surface tension or adhesive force of the liquid to reduce the liquid content of a liquid bonded grindstone made by compression molding. , a polishing method characterized in that a liquid is present on the surface of the liquid bond grindstone, and the material to be polished is polished while being pressed. (2) The liquid constituting the liquid bond grindstone contains a component that can be easily dissolved or mixed with the liquid and has the function of fixing the abrasive grains together when the concentration in the liquid is high. Characteristic Claim No. (1)
Polishing method described in section. (3) The polishing method according to claim (1), wherein the liquid bond grindstone is obtained by mixing abrasive grains and a liquid, granulating the mixture, and then compression molding the mixture.