CN100581731C - Surface processsing method of white gem crystal - Google Patents

Abstract

The invention relates to a surface processing method for a sapphire crystal, in particular to a method of chemical-mechanical polishing by silicon dioxide solution with weight concentration of 30 to 50 percent. The operation conditions of finishing polish are as follows: the PH value of the solution is 9 to 11, the temperature is controlled within 22 to 25 DEG C, the rotating speed of a machine tool is 40 to 100 revolutions per min, and the polishing time is 8 to 14 hours. The method of the invention can increase the processing precision of the sapphire crystal, the surface roughness can reach 0.5nm rms, and the processing time can be greatly reduced.

Description

A kind of surface processing method of white gemstone crystal

technical field

The invention relates to a surface processing method of white gem crystals, in particular to a process of processing white gem crystals with a chemical mechanical polishing method to achieve an ultra-smooth surface.

Background technique

The chemical oxygen iodine laser is one of the most promising high-power lasers due to its short wavelength and good transmission characteristics. Due to the need to carry a high power density, the thermal deformation of optical components in the cavity, especially the laser output window, has become one of the important factors restricting the development of high-power lasers. According to foreign literature reports, due to a series of unique and excellent physical and chemical properties, white gem has been widely used in high-power lasers (such as HF, DF, CO2 lasers) as window materials, and is also used in infrared military equipment, satellites and Instrumentation for space technology, etc. Because of the high power density to be carried, ultra-smooth surface processing of high-power laser output window materials is necessary.

In the past, people used the method of processing white gemstones: asphalt disks were used for polishing, and diamond micropowder was used as polishing abrasives. The surface roughness of the white sapphire substrate processed by this method is generally 2-3nm rms, and the surface finish is not good, with many scratches.

The ultra-smooth surface of the white sapphire substrate was processed according to the traditional process. The polishing liquid was diamond paste, the polishing disc was an asphalt disc, the polishing time was 40 hours, and the surface roughness was 1nm rms.

According to the literature report (Ultra-smooth and high-flatness polishing process for brittle and hard materials-excerpted from "Ultra-precision Machining and Measurement and Control Technology Papers"), the polishing disc is made of tin plate, and the polishing liquid is colloidal SiO ₂ solution. After polishing (polishing time is about For more than several hundred hours), the surface roughness of the white gemstone substrate is 0.23nm rms.

Contents of the invention

The object of the present invention is to provide a super-smooth surface processing method of white gemstone crystal. Using the method to process the white gem crystal can make the surface roughness of the white gem crystal reach <0.5nm rms.

To achieve the above object, the technical solution adopted in the present invention is:

A kind of surface processing method of white sapphire crystal, adopts weight concentration 30-50% silicon dioxide aqueous solution (such as: the 80# aqueous solution that Japanese fujimi company produces) to carry out chemical mechanical polishing through the white sapphire crystal substrate of grinding process, solution PH The value is 9-11. The polishing machine adopts a two-axis or four-axis grinding and polishing machine, and an optical polishing cloth is laid on the polishing disc. The machine speed is 40-100 rpm, and the polishing time is 8-14 hours; through chemical mechanical polishing The method makes white sapphire crystal achieve an ultra-smooth surface of less than 0.5nm rms. The temperature of the polishing process is controlled at 22-25°C.

A two-axis or four-axis grinding and polishing machine is used, with a smooth-surfaced grinding block as a grinding disc, the abrasive is boron carbide, and the machine speed is 40-100 rpm;

The first fine grinding: use boron carbide with a particle size of F14, and the surface is evenly ground, usually for 5 minutes to 1 hour;

The second fine grinding: use boron carbide with a particle size of F10, and the surface is evenly ground, usually for 10 minutes to 1.5 hours;

The third fine grinding: use boron carbide with a particle size of F5, and the surface is evenly ground, usually for 20 minutes to 3 hours;

The fourth fine grinding: use boron carbide with a particle size of F3.5, and the surface is evenly ground, usually for 30 minutes to 5 hours.

The temperature in the grinding process is controlled at 22-25° C.; the grinding block with a smooth surface is a diamond block or a precision ceramic block.

The beneficial effects of the present invention are:

The method of the invention can not only improve the processing quality of the white gemstone, but also greatly reduce the processing time. After processing, the white gemstone crystal has a good surface finish and no scratches, and its surface roughness is less than 0.5nm rms. The invention is beneficial to carry out the processing work of the output window of the high-power laser and the instrument of the infrared military equipment and the satellite.

Detailed ways

Due to the high hardness of white gemstones, it brings certain difficulties to processing. According to the basic properties of white gemstones, precision ceramics are used as grinding discs for white gemstones for rough grinding and fine grinding, because precision ceramics contain α-Al ₂ O ₃ components, and their hardness is slightly lower than that of white gemstones. Copper, glass, etc. are denser than ceramics themselves than the above materials. After fine grinding with other materials such as iron, copper, glass, etc., some scratches will appear on the surface of white sapphire. Using ceramic rough grinding and fine grinding can solve this key problem. The material used is boron carbide. In order to speed up the time of coarse grinding and fine grinding, several models of boron carbide can be used, and the distance between the models should not be too close.

In the past, the mixture of asphalt and rosin was basically used as the polishing material after the white sapphire lens was finely ground, but because the uniformity of its particles in the polishing material is not absolutely the same, the larger particles are often pressed into the polishing disc. This will cause scratches on the surface of the white sapphire lens, which directly affects the quality of the experiment, and the surface roughness cannot meet the requirements. By understanding some advanced materials at home and abroad, combined with the problems we actually encountered, and after repeated demonstrations, we replaced the traditional asphalt polishing method with a polishing cloth. The polishing material is Japanese 80# polishing liquid. After a certain polishing time, the surface roughness of white gemstone can reach less than 0.5nmRMS.

The concrete processing method of described super-smooth surface of white sapphire crystal is as follows:

Example 1

Select Φ30mm white sapphire crystal substrate

1. Fine grinding process:

Grinding Disc: diamond block

Abrasive: boron carbide

Grinding machine: two-axis grinding and polishing machine, the machine speed is 80 rpm;

The first fine grinding: use boron carbide with a particle size of F14, and the surface is evenly ground, usually for 6 minutes;

The second fine grinding: use boron carbide with a particle size of F10, and the surface is evenly ground, usually for 20 minutes;

The third fine grinding: use boron carbide with a particle size of F5, and the surface is evenly ground, usually for 30 minutes;

The fourth fine grinding: use boron carbide with a particle size of F3.5, and the surface is evenly ground, usually for 40 minutes.

The temperature of the grinding process is controlled at 22-25°C;

2. Polishing process:

An optical polishing cloth is laid on the polishing disc;

Polishing agent: 40% silicon dioxide aqueous solution by weight (such as: 80# aqueous solution produced by Fujimi Company in Japan) 80# aqueous solution

Solution pH value: 9

Grinding machine: two-axis grinding and polishing machine

Machine speed: 50 rpm

Polishing temperature: 22-25°C

Polishing time: 8 hours

The white sapphire crystal achieves an ultra-smooth surface of less than 0.5nm rms by chemical mechanical polishing; the temperature of the polishing process is controlled at 22-25°C.

Example 2

Select Φ110mm white sapphire crystal substrate

1. Fine grinding process:

Grinding Disc: diamond block

Abrasive: boron carbide

Grinding machine: four-axis grinding and polishing machine, the machine speed is 40 rpm;

The first fine grinding: use boron carbide with a particle size of F14, and the surface is evenly ground, usually for 1 hour;

The second fine grinding: use boron carbide with a particle size of F10, and the surface is evenly ground, usually for 1.5 hours;

The third fine grinding: use boron carbide with a particle size of F5, and the surface is evenly ground, usually for 3 hours;

The fourth fine grinding: use boron carbide with a particle size of F3.5, and the surface is evenly ground, usually for 5 hours.

The temperature of the grinding process is controlled at 22-25°C;

2. Polishing process:

An optical polishing cloth is laid on the polishing disc;

Polishing agent: 30% aqueous solution of silica by weight

Solution pH value: 11

Grinding machine: four-axis grinding and polishing machine

Machine speed: 40 rpm

Polishing temperature: 22-25°C

Polishing time: 14 hours

The white sapphire crystal achieves an ultra-smooth surface of less than 0.5nm rms by chemical mechanical polishing; the temperature of the polishing process is controlled at 22-25°C.

Example 3

Select Φ80mm white sapphire crystal substrate

1. Fine grinding process:

Grinding Disc: diamond block

Abrasive: boron carbide

Grinding machine: four-axis grinding and polishing machine, the machine speed is 60 rpm;

The first fine grinding: use boron carbide with a particle size of F14, and the surface is evenly ground, usually for 0.5 hours;

The second fine grinding: use boron carbide with a particle size of F10, and the surface is evenly ground, usually for 50 minutes;

The third fine grinding: use boron carbide with a particle size of F5, and the surface is evenly ground, usually for 1 hour;

The fourth fine grinding: use boron carbide with a particle size of F3.5, and the surface is evenly ground, usually for 3 hours.

The temperature of the grinding process is controlled at 22-25°C;

2. Polishing process:

An optical polishing cloth is laid on the polishing disc;

Polishing agent: 50% aqueous solution of silica by weight

Solution pH value: 10

Grinding machine: four-axis grinding and polishing machine

Machine speed: 90 rpm

Polishing temperature: 22-25°C

Polishing time: 12 hours

The white sapphire crystal achieves an ultra-smooth surface of less than 0.5nm rms by chemical mechanical polishing; the temperature of the polishing process is controlled at 22-25°C.

Claims (4)

1. the method for surface finish of a white gem crystal, it is characterized in that: will adopt the weight concentration 30-50% silica aqueous solution to carry out chemically mechanical polishing through the white gem crystal substrate of attrition process, the solution pH value is 9～11, polishing mechanical adopts diaxon or four polisher lappers, on polishing disk, be equipped with optical polish cloth, the lathe rotating speed is 40～100 rev/mins, and polishing time is 8～14 hours;

Described attrition process operation: adopting diaxon or four polisher lappers, is mill with ganoid abrading block, and abrasive material is a boron carbide, and the lathe rotating speed is 40～100 rev/mins;

The first road fine grinding: with granularity is the boron carbide of F14, and surface grinding is even, grinds 5 minutes-1 hour;

The second road fine grinding: with granularity is the boron carbide of F10, and surface grinding is even, grinds 10 minutes-1.5 hours;

The 3rd road fine grinding: with granularity is the boron carbide of F5, and surface grinding is even, grinds 20 minutes-3 hours;

The 4th road fine grinding: with granularity is the boron carbide of F3.5, and surface grinding is even, grinds 30 minutes-5 hours.

2. according to the method for surface finish of the described white gem crystal of claim 1, it is characterized in that: the polishing process temperature is controlled at 22～25 ℃.

3. according to the method for surface finish of the described white gem crystal of claim 1, it is characterized in that: the process of lapping temperature is controlled at 22～25 ℃.

4. according to the method for surface finish of the described white gem crystal of claim 1, it is characterized in that: described ganoid abrading block is diamond piece or high technology ceramics piece.