JPH0818230B2 - Polishing method - Google Patents

Description

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

<Prior art> A liquid bond grindstone is one in which a small amount of liquid is added to the abrasive grains, mixed evenly, placed in a mold, and compression-molded. The technique of precision polishing finishing of the material to be polished such as resin material is "valley,
Kawada "Development of high-efficiency polishing method using liquid bond grindstone" Proceedings of the Japan Society of Mechanical Engineers, Volume 50, 471, Showa 60-11, "Tani, Kawada" Development of high-efficiency polishing method using liquid bond grindstone "Production Research Vol. 37, No. 7, 1985, 7 ”,“ Tani, Kawada “Application of Liquid Bonded Grinding Wheel to Surface Polishing” Proc. High-efficiency polishing of silicon wafer "Proceedings of 1987 Precision Engineering Society Spring Conference Academic Lecture Proceedings".

<Problems to be solved by the invention> However, the method described in the above-mentioned literature, the mixing ratio of the abrasive grains and the liquid, set so as to be between the Pendler region and the funicular region, mixing, compression, When you perform operations such as molding,
Since the mixing ratio of the liquid is small, the fluidity of the mixture is poor, and it is difficult to uniformly mix the abrasive grains and the liquid, resulting in non-uniformity. When the abrasive grains and the liquid are compression-molded in a non-uniform mixed state, the density and hardness of the molded grindstone vary, the grindstone partially collapses during polishing, and the polishing finish is uneven. Will occur.

The mixing ratio of the abrasive particles and the liquid such that it is between the pendular area and the funicular area is not constant because it varies depending on the type of the abrasive particles and the liquid, the particle diameter of the abrasive particles, the shape, etc. The proportion of the liquid that occupies is much smaller than that of the abrasive grains, and is usually only about 10 to 20% of the abrasive grains. Therefore, a method has been proposed in which the liquid constituting the liquid bond grindstone is diluted with a liquid that is more volatile than the liquid, the diluted liquid is excessively mixed with the abrasive grains, and then the excess liquid is removed by evaporation. . However, since this diluting liquid uses hexane or alcohol, it has properties such as high flammability and strong toxicity, and special care must be taken in handling.

Further, even if the mixing ratio of the abrasive grains and the liquid is properly and uniformly mixed, the liquid used in the liquid bond grindstone has a property of evaporating when itself left as water or oil. Since there are many things, the formed liquid bond grindstone has poor storage stability. Then, after the mixture of the abrasive grains and the liquid is molded, if the polishing process is not performed immediately, the ratio of the abrasive grains to the liquid changes with time due to the evaporation of the liquid, so that the polishing conditions vary depending on the polishing. In reality, it is difficult to keep polishing efficiency and accuracy constant.

In addition, since the liquid bond grindstone has a liquid binding medium for the abrasive grains, it has poor physical strength even when compression-molded, and will collapse if the material to be polished is pressed strongly. It is easily damaged when fixed to. For this reason, the liquid bond grindstone must always be transported in a strong and easily housed state, or fixed to a device and polished, resulting in extremely poor workability.

Further, during the polishing process using the liquid bond grindstone, the temperature rise of the material to be polished due to the frictional heat of processing is suppressed, and the facets of the liquid bond grindstone are removed to remove the facets on the surface of the liquid bond grindstone. It is desirable to flush or atomize water or other cooling liquid, but this is not easy to do because it will soften and accelerate wear on the liquid bond wheels and often cause collapse.

<Means for Solving Problems> The present invention has been proposed in view of the above, in which the abrasive grains and the liquid are mixed to allow the liquid to exist between the abrasive grains, and the abrasive grains are generated by the surface tension or the adhesive force of the liquid. After reducing the liquid content of the liquid bond grindstone formed by holding and holding the liquid bond, the liquid is present on the surface of the liquid bond grindstone so that the material to be polished is pressed and polished. To do.

As the abrasive grains of the liquid bond grindstone used in the polishing method of the present invention, diamond, corundum, emery, garnet, silica, tribolite, 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, silica, shirasu, etc. It can be a stuff. And, the grain size of the above-mentioned abrasive grains is about 30 μm or less.

The liquid of the liquid bond grindstone used in the polishing method of the present invention is water, an alkaline solution, an acid solution, an aqueous solution of many other salts, a polymer solution, an oily liquid, a magnetic fluid, or the like.

<Operation> When the liquid bond grindstone according to the present invention is molded, the mixing ratio of the abrasive grains and the liquid can be arbitrarily set so as to be in a state convenient for operations such as mixing, compression and molding.
Then, when the abrasive particles and the liquid are mixed, the liquid is generally in excess of the abrasive particles in order to provide fluidity,
Even if the liquid is excessive, the liquid content is reduced by drying or other treatment. Therefore,
The mixing ratio of the abrasive grains and the liquid does not need to be particularly taken into consideration in the stage before molding, so that this mixing process is easy and unevenness in the density and hardness of the molded product does not occur. Further, in order to increase the fluidity of the mixture, when the mixture is granulated into an appropriate size and compression 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 particles can be set to a state convenient for the granulation operation.

As described above, when the abrasive grains, the liquid, and the liquid are mixed at a mixing ratio in an optimum state for molding, this mixture is compression molded.
The pressure required for this compression molding is about 100 kg / cm ² or more, preferably 300 kg / cm ² or more.

After the compression molding of the mixture of the abrasive grains and the liquid as described above, the liquid contained in the molded product is reduced. As a method for reducing this liquid, a drying treatment or a contact with a liquid absorbent is carried out, but this treatment is carried out before compression molding or, if granulation treatment is added, at the time of granulation or at the time of granulation. May be done to.

In this way, if the liquid contained in the molded product is reduced, the physical strength increases, and even if the material to be polished is strongly pressed, it will not easily collapse or break, and it will be easy to carry or attach to the polishing device. , Becomes an effective liquid bond grindstone.

When the liquid content of the above-mentioned molded product is reduced and the mixed state of the liquid with respect to the abrasive grains becomes about the lower limit of the Pendler region, most of the contained liquid is in the state of being adsorbed on the surface of the abrasive grains. Since the adsorbed liquid does not easily evaporate, the molded product can be stored for a long period of time, the content of the liquid hardly changes with time, and the stability becomes remarkably good.

Further, the physical strength of the above-mentioned molded product is different depending on the types of the abrasive grains and the liquid, but if the strength of the molded product by the above-mentioned molding method is still insufficient, then the liquid that composes the liquid-bonded grindstone can be prepared in advance. In addition, a component (hereinafter referred to as an additional component) which can be easily dissolved or mixed in a liquid and has a function of fixing the abrasive grains to each other when the concentration in the liquid is high can be added. This additive component is concentrated by the above-mentioned drying treatment of the molded product and firmly fixes the abrasive grains to each other, so that the physical strength of the molded product is remarkably strengthened.

Then, the above-mentioned additive component, even if a liquid is sprayed on the surface during the polishing process of the material to be polished, is easily dissolved or swollen due to contact with the liquid, mixing, etc. to be in a state close to the liquid state before drying. It must be. For example, if the liquid to be sprayed is water, water glass or a water-soluble polymer organic substance is effective as the additive component, and if the liquid to be sprayed is oil, an oil-soluble polymer organic substance should be used as the additive component. You can

However, when the molded product is dried by heating to reduce the contained liquid, the above-mentioned additional components are thermally polymerized depending on the type, and easily become the state before drying when spraying or flowing the liquid in the next polishing treatment. It may not return. Therefore, it is necessary to pay sufficient attention to the selection of the additive component and the setting of the heat drying treatment condition, and after the abrasive grains and the liquid are mixed and molded, the deterioration proceeds with time, the dissolution in the liquid, the swelling, It is better not to use an additive component that causes a change in mixing speed.

However, even if the additive component is altered, it may be possible to implement it if the degree of alteration is such that it does not adversely affect the liquid bond grindstone. For example, a water-soluble polymer organic substance is used as an additive component, and when this organic substance is polymerized by heating to become water-insoluble, a solvent that dissolves the water-insoluble substance is used as a liquid that is sprayed or flushed during polishing. Therefore, the present invention can be implemented. Further, if the added component is too much, the following defects may occur, which is not desirable. That is, in order to quickly make the added component into a liquid state, it is necessary to spray a large amount of liquid when performing a polishing process using the liquid bond grindstone after drying, and the mixed state of the abrasive grains of the liquid bond grindstone and the liquid is generated. This is because there is a possibility of exceeding the funicular range.

Therefore, the addition amount of the additive component is not constant depending on the type of the abrasive grains, the liquid, and the additive component, but is generally 1% by weight or less with respect to the abrasive grains.

The molded product molded as described above, that is, the liquid bond grindstone is attached to a polishing device and is present while spraying or pouring a liquid on the surface, and pressing the material to be polished with the liquid bond grindstone and the material to be polished. Slide relatively. As a result, the liquid permeates into the fine gaps of the abrasive grains of the liquid bond grindstone, and the mixed state of the abrasive grains and the liquid is a mode in which the liquid is attached in an annular shape around the contact points of the abrasive grains, It is a continuous state. This state is the Pendler region, but when the liquid is further sprayed or poured on the surface of the liquid bond grindstone, the liquid closes at the surface including the contact points of the abrasive grains, and the funicular region where the liquid continuously exists. Convert to. Therefore,
By adjusting the amount of liquid supplied to the surface of the liquid bond grindstone, it is possible to set the most preferable mixed state of the abrasive grains and the liquid as the liquid bond grindstone. Further, even if the molded product for a liquid bond grindstone is not used in the polishing process and is stored for a long period of time, the liquid content does not change significantly, so that the amount of liquid supplied to the surface of the liquid bond grindstone is always constant. A stable polishing process can be performed.

Further, since the liquid supplied to the surface of the liquid bond grindstone is sprayed or poured, the conversion of the liquid bond grindstone from the pendular region to the funicular region starts from the surface of the liquid bond grindstone and gradually shifts to the inside. That is, since the liquid bond grindstone during the polishing process has a large amount of liquid on the surface, the temperature rise due to frictional heat is suppressed in the surface portion of the liquid bond grindstone with which the material to be polished contacts, and the discharge of cutting chips Does not adversely affect. However, because the liquid inside the liquid bond grindstone changes with less liquid compared to the surface portion, the physical strength of the liquid bond grindstone as a whole becomes high.For example, applying a pressure of about 10 kg / cm ² to the material to be polished. It does not disintegrate even if it is abraded and can be efficiently abraded at a high processing pressure.

<Examples> Examples of the present invention will be described below.

Example 1 1 kg of abrasive grains Q ^# 3000 and 2 kg of a mixed aqueous solution of starch and urethane were sufficiently stirred and mixed, and a paste-like mixture was poured into a mold. This paste-like mixture has a significantly large amount of liquid and almost no air phase in the mixed state of the abrasive grains and the liquid, and thus far exceeds the funicular range. When this mixture was forced to dry at 60 ° C. for 12 hours, the liquid content dropped to 17%, and the mixture contained a continuous and discontinuous air phase, and became a liquid bonded wheel.

When the physical properties of the liquid bond grindstone thus obtained are measured, the hardness is 72, the bending strength is 0.1 kg / cm ² or less, and the compressive strength is 0.1 kg / c.
It was less than m ² .

When this liquid bond grindstone was further dried at 60 ° C. for 24 hours, it had a hardness of 80, a bending strength of 4 kg / cm ² , and a compressive strength of 7 kg / cm ² , and the physical strength was remarkably improved.

Example 2 A grindstone C ^# 3000 and a liquid 5% CMC aqueous solution were mixed at a weight ratio of 1: 0.9.
Was mixed, filled in a mold container and compression-molded by a compression molding machine to obtain a liquid bond grindstone having a thickness of about 10 mm. The compression load at this time was 200 to 300 kg / cm ² , and the compression ratio was about 3.3. The obtained liquid bond grindstone is in a state of extremely poor physical strength, such that it will collapse when just picked up by hand when taken out from the mold container.
The bending strength was 0, the bending strength was 0.1 kg / cm ² or less, and the compression strength was 0.1 kg / cm ² or less.

When the liquid bond grindstone prepared in the same manner as above is taken out from the mold container and dried to reduce the liquid content to about 5% of the grindstone weight, the physical strength of the molded product is remarkably improved, the hardness is 98, and the bending is The strength was 10 kg / cm ² , and the compressive strength was kg / cm ² , and it did not chip or break even when carried or set in a polishing machine. The molded product in this dry state has almost no volatile components in the liquid constituting the liquid bond grindstone, so in the mixed state of the abrasive grains and the liquid, only the non-volatile component causes the contact point of the abrasive grains to rise. It is considered that it is slightly attached to the center and remains, that is, forms the lower limit of the Pendler region.

Then, when about 0.02 ml of water is sprayed onto the surface of the dried molded product per cm ^{2 of} the molded product, the surface softens and the depth of 1 mm or more from the surface can be easily scraped off with a knife. However, no softening was observed at the site where the depth from the surface was 1 mm or more.

When the spraying of water was further continued, the softened layer of the molded product became deeper, and the depth of the softened layer reached the bottom of the molded product at a spraying amount of about 1.8 ml per cm ² of the surface of the molded product. When the physical properties of this softened molded product were measured, hardness 91, bending strength 0.
It was 1 kg / cm ² or less and the compressive strength was 01, kg / cm ² or less, and it was a physical property as a liquid bond grindstone before drying.

Example 3 1.0 ml of abrasive grains Q ^# 3000 was mixed with 90 ml of a liquid 30% acrylic emulsion solution little by little while being mixed and granulated by a mixing granulator to a particle size of about 50 to 250 μm, and this mixture was mixed. The granulated material was supplied to a compression molding machine and compression molded to obtain a liquid bond grindstone. The liquid content of this liquid bond grindstone is 20
%, Hardness 87, bending strength 0.1 kg / cm ² or less, compression strength 0.1 kg / c
Although it was less than m ^{2, when} it was stored in the room for 3 weeks, the liquid content was 3.6%, the hardness was 93, the bending strength was 10 kg / cm ² , and the compression strength was 22 kg / cm ² , which markedly affects the liquid content and physical properties. A change has occurred.

On the other hand, a liquid bond grindstone that was compression molded in the same manner as above was placed in a heating machine at 70 ° C, and for 12 hours, the liquid content of the molded product was 2.8%, hardness 99, bending strength 15, compression strength. Although the value was 30, the molded product was stored in the room for 3 weeks, and the measurement result showed that the liquid content and the physical properties did not change at all immediately after drying, and the storage stability was excellent.

Example 4 Petroleum resin 25 g as a liquid for ¹ kg of abrasive grain WA ^# 3000
While dropping 150 ml of xylene solution in which was dissolved, mix and granulate with a mixing granulator, supply to a compression molding machine and load 350 to 4
A liquid bond grindstone was formed by molding at 00 kg / cm ² and a compression ratio of 2.7. When the hardness of this liquid bond grindstone was measured, there was a large variation in hardness depending on the measurement site on the surface of the grindstone,
The lowest value was 72, the highest value was 77, and the average value was 73.

On the other hand, to ¹ kg of abrasive grains WA ^# 3000, while dropping 180 ml of xylene solution in which 25 g of petroleum resin was dissolved as a liquid,
The liquid-bonded grindstone was prepared by mixing and granulating with a mixing granulator and then molding it with a compression molding machine at 350 to 400 kg / cm ^{2 at} a compression ratio of 2.5 in the same manner as above. This liquid bond grindstone was once dried by heating to a liquid content of 5% or less, then 30 ml of xylene containing no petroleum resin was poured onto the surface of the dried product, and the liquid bond grindstone was returned to the original liquid bond grindstone. Hardness of this liquid bond grindstone showed almost no fluctuations at any position on the grindstone surface, with a minimum value of 74, a maximum value of 75, and an average value of 74.5.

Example 5 While dropping 45% acrylic emulsion solution and 3% starch solution as liquids into Q ^# 3000 as abrasive grains, they were mixed and granulated by a mixing granulator, and the mixed granulation product was placed in a mold container. And then supply it to the compression molding machine with a load of 400 to 500 kg / c.
A liquid-ond whetstone was obtained by compression molding with m ² and a compression ratio of 2.1.
Then, the mold container containing this liquid bond grindstone was placed on the rotary table of the flat lapping machine, the sliced silicone wafer surface was pressed against the grindstone surface, and pure water was added to 10 ml / m.
At a ratio of in, the surface of the grindstone was continuously slid while being sprayed. At a processing load of 3 kg and a relative rotation speed of 30 m / min, the processing efficiency was 3 μ / min, and the wear amount of the liquid bond grindstone at a polishing extension time of 20 min was 7 mm.

When 26 minutes passed after continuing the polishing of the silicone wafer, the liquid bond grindstone collapsed and the polishing could not be continued.

On the other hand, the liquid bond grindstone prepared in the same manner as above was taken out of the mold, placed in a metal heating machine, and forcibly dried under the conditions of 50 ° C. and 24 hours. This dry molded product was adhered on a flat lapping machine, and the sliced silicone wafer surface was pressed against the molded product surface, and pure water was slid while continuously spraying the grindstone surface at a rate of 15 ml / min. . When polishing was carried out under the same polishing conditions as above, the processing efficiency was 3 μ / min, but the wear rate of the grindstone at a polishing total time of 20 min was 0.6 mm.
The grinding stone did not disintegrate even after 35 minutes had passed after polishing was continued.

Claims (1)

[Claims] 1. A liquid content of a liquid bond grindstone obtained by mixing abrasive particles and a liquid to allow a liquid to exist between the abrasive particles, holding the abrasive particles by the surface tension or adhesive force of the liquid, and compressively deforming the abrasive particles. After the amount is reduced, a liquid is interposed on the surface of the liquid bond grindstone to polish the material to be polished while pressing the material to be polished.