FR2667606A1 - MECHANICAL CHEMICAL POLISHING ABRASIVE AND METHOD OF POLISHING A PART USING THE ABRASIVE - Google Patents

Abstract

The invention relates to a chemical mechanical polishing abrasive. The chemical-mechanical polishing abrasive of the invention comprises a suspension of colloidal silica and a mechanical abrasive chosen from one or more materials from the group comprising Fe2 O3, Fe3 O4, MgO, BaCO3, CaCO3, MnO2, CeO, SiO2, CeO2 , Cr2 O3 and Al2 O3 Application of chemical mechanical polishing abrasive: inexpensive and efficient polishing of the surface of a hardened machined part.

Description

The present invention relates to a chemical mechanical polishing abrasive

  for use in polishing hard substrates such as ceramics, crystalline materials, glass and similar materials whose surfaces must be polished to a high degree. The financial aspect of polishing and machining of ceramics can often be the most expensive part of the ceramic production process Economic considerations for polishing ceramics involve both time and products

  consumables used For the final polishing of ceramics

  diamond-based abrasives are widely used, these abrasives being expensive and the process of

  polishing that uses them being long.

  Conversely, the machining of ceramics can be very detrimental Unlike the machining of metals that are ductile, ceramics are generally very brittle The brittle nature of ceramics makes them very sensitive to breakage under the surface This deterioration under the surface adversely affects important physical properties of ceramics These properties

  adversely affected by machining

  reduce the mechanical strength of the ceramic, variations in its magnetic properties and

  even changes in its electronic properties.

  The machining of elaborate ceramics has traditionally been accomplished by hard abrasives such as diamond and silicon carbide. Although this has resulted in surfaces that are acceptable in some circumstances, there is still some degree of surface deterioration and degradation. the underlying part when using these compounds The use of softer polishing abrasives, such as colloidal silica, for the machining of elaborate ceramics has been taken into consideration.

  colloidal polished alumina, silica and silicon.

  In fact, colloidal silica has been used extensively for polishing silicon wafers.

  the use of colloidal silica to polish ceramics

  The elaborate techniques tend to give a polished, elaborated ceramic product with a significant phase relief. It is supposed that the relief is due to the chemical dissolution by colloidal silica of selective grains on the materials.

elaborate ceramics.

  The use of colloidal silica to polish surfaces of silicon, metals, glass, garnets and sapphires is disclosed in the article by HW Gutsche and JW Moody, entitled "Polishing of Sapphire with Colloidal Silica", J Electrical Chemical Soc. 125, No. 1, pages 136-138 (1978) This article discloses that colloidal silica exerts a chemical effect on sapphire which is a hard material, allowing colloidal silica to polish sapphire The article says nothing about the combination of colloidal silica with other substances

  for polishing hardened materials.

  The use of CaCO 3, BaCO 3 and Mg O as chemical mechanical polishing abrasives is revealed in an article by H Bora and RJ Stokes, published in the Study of Mechanochemical Machining of Ceramics and the Effect on Thin Film Behavior, report No. 00014-80-C-0437-1 (of April 30, 1981) This report describes in detail the polishing of thin layers of Mg O, A 1203 and Si by various abrasives including rock, calcite, fluorite and various other abrasives including window glass The three compounds mentioned above have been shown to be able to accomplish polishing

  mechano-chemical of one or more of the above materials.

  None of the mechanical-chemical abrasives used were

  associated with colloidal silica.

  Mechano-chemical polishing of sapphire, silicon and quartz crystals is described by N.

  Yasunaga, U Tarumi, to Obara in "Mechanism and Applica-

  Mechanism of the Mechanochemical Polishing Method Using Soft Powder, "The Science of Ceramic Machining and Surface Finishing II, Special Publication NBS 562, U S Government

  Printing Office, Washington, DC, pages 171-183 (1979).

  Sapphire, silicon, quartz have been polished with

  mechano-chemical mediums wet and dry.

  Mechano-chemical environments included Ba CO 3, Fe 3 O 4, Ca CO 3, Si O 2, Ce O 2, diamond and Mn O 2.

  of the article is a description of the formation of

  Crystalline silica materials in the mixed powder abrasive during polishing of a workpiece Crystalline materials were produced by polishing the hard materials described above at high temperatures and high pressures with the use of the mixed powder The article does not disclose the use of colloidal silica in any way for chemical mechanical polishing. It is an object of the present invention to provide an inexpensive chemical mechanical polishing abrasive capable of polishing a cured workpiece without selective abrasion of the surface particles of the

hardened part.

  Another object of the present invention is to find a method of polishing a cured machined part using an inexpensive mechanical-chemical abrasive. The present invention relates generally to a mechanical-chemical abrasive. The chemical-mechanical abrasive comprises a suspension of colloidal silica containing one or

several mechanical abrasives.

  According to a variant of this form of embodiment

  The present invention resides in a mechanical abrasive

  chemical composition comprising a colloidal silica suspension and a mechanical abrasive selected from one or more of the group consisting of Fe 2 O 3, Fe 3 O 4, Mg O, BaCO 3,

  Ca 3 CO 3, Mn O 2, Ce O, Si O 2, Ce O 2, Cr 2 O 3 and A 1203.

  In a preferred embodiment, the present invention resides in a chemical mechanical polishing abrasive comprising from about 13 to about 99.3 weight percent of a colloidal silica base slurry and from about 0.7 to about 2.0 percent by weight of a mechanical abrasive The mechanical abrasive is in

  particles having a diameter of about 0.1 gm to about 10 gm.

  The mechanical abrasive is selected from one or more of the materials belonging to a group comprising Fe 2 O 3, Fe 3 O 4, Mg O, BaCO 3, CaCO 3, MnO 2, CeO, SiO 2, CeO 2. , Cr 203 and A 1203. In another embodiment, the present invention relates to a method of polishing one or more machined parts with a chemical mechanical polishing abrasive. The chemical mechanical polishing abrasive

  comprises an aqueous suspension of colloidal silica and a mechanical abrasive selected from one or more of the materials in the group comprising Fe 2 O 3, Fe 3 O 4, 30 Mg O, Ba CO 3, Ca CO 3, Mn O 2, Ce O, Si O 2, Ce O 2, Cr 203 and A 1203.

  The machined part is polished by applying the chemical-mechanical polishing abrasive to a directly machined part, or by means of a polishing pad and placed in contact with the polishing means with one or more machined parts for a period of one year. enough time to polish

a surface of the room.

  The present invention relates to a mechanochemical polishing abrasive and a polishing method

  of a machined part using mechanical polishing abrasive

  The chemical mechanical polishing abrasive of the present invention comprises a material consisting of

  colloidal silica in combination with a mechanical abrasive.

  The colloidal silica material contained in the chemical mechanical polishing abrasive of the present invention chemically reacts with the various surface components that make up the machined parts.

  which are polished with the mechanical polishing abrasive

  The precise chemical reaction that takes place between colloidal silica and the elements and molecules on the surface

  the machined part is not fully understood.

  However, colloidal silica is believed to react with the surface of the cured workpiece by creating a surface material on the workpiece that is softer than the mechanical abrasive. As mentioned above, one of the disadvantages of colloidal silica resides in the fact that it obviously attacks preferential grains on the surface of the cured substrate, so that a raised surface finish may result when the surface of the piece

  is chemically modified by colloidal silica.

  Colloidal silica is normally presented as an aqueous suspension (containing water)

  containing up to 50% or more than 50% silica

  An interesting feature of the colloidal silica suspension is that this silica does not sediment from a suspension even after a long period of time. Colloidal silica is generally contained in

  an aqueous suspension which is mixed with water.

  However, for the purposes of the polishing abrasive of the present invention, the colloidal silica is not necessarily, and in some cases should not, be suspended in water, but may be suspended in some other liquid such as an alcohol and an organic solvent or similar material Water is not desired in the form of a suspension of material in all cases, because the water may react adversely with certain

  machined parts hardened giving a product without interest.

  The colloidal silica recommended for use is an aqueous suspension of colloidal silica. The percentage by weight of colloidal silica

  in the aqueous suspension is not critical.

  It is preferable that the colloidal silica is present in the aqueous suspension in an amount

  from about 15 to about 50 percent by weight or more.

  Other properties of the colloidal silica suspension such as p H, particle diameter, etc., are not absolutely critical for its usefulness in the chemical reaction with the surface of a cured machined workpiece. However, it is preferable that The colloidal silica suspension is greater than about seven times. A colloidal suspension of silica having a pH greater than about seven is a basic suspension, and has been found to react more effectively with the surface of the materials which may be present. polished with the chemical-mechanical polishing abrasive of this

invention.

  The aqueous suspension of colloidal silica may advantageously be any known suspension of colloidal silica. In general, the colloidal silicas are stabilized at a pH of about 8 to 14 and more often at a pH in the range of about 9 to 11 The preferred colloidal silica has a pH range of about 9.8 to 10.2

  and has an average particle diameter of about 0.06 μm.

  The chemical mechanical polishing abrasive of the present invention also contains a mechanical abrasive The mechanical abrasive is generally a softer material than the material constituting the machined part However, the mechanical abrasive is generally harder than the surface material the machined part resulting from the chemical reaction between the colloidal silica components of the polishing abrasive and the hardened part The objective of the mechanical abrasive is to abrasion away the softer materials that have reacted from the surface of the abrasive the machined part

  hardened by leaving a smooth surface Due to the removal of

  By abrasion of the softer reaction product from the surface of the cured part, the mechanical abrasive continually exposes a colloidal silica-cured surface which chemically reacts with the exposed surface. In this way, the selective reaction of the colloidal silica with various grains selective on the surface of hardened parts can be reduced to a minimum by producing a surface

strongly polished hardened substrate.

  The mechanical abrasive useful in the chemical-mechanical abrasive of the present invention may be any material or combination of materials known in the prior art as being suitable for use as a mechanical abrasive. The mechanical abrasive is normally softer, c That is, it is not as hard as the material constituting the machined part. The mechanical abrasive may, for example, be chosen from one or more of the following compounds: Fe 2 O 3, Fe 3 O 4, Mg O, Ba CO 3, CaCO 3, MnO 2, CeO 2, SiO 2, CeO 2, Cr 2 O 3 and A 1203. A preferred mechanical abrasive is Fe 2 O 3 mean diameter of the particles from about 0.1 to about 10 micrometers and especially

from about 0.5 to 5.0 micrometers.

  As previously mentioned, the mechanochemical polishing abrasive of the present invention comprises a colloidal silica suspension and one or more mechanical abrasives. The chemical mechanical polishing abrasive of the present invention normally contains about 0.1 gram of a mechanical abrasive. powder with 100 ml of colloidal silica to a sufficient amount of mechanical abrasive in combination with colloidal silica for the chemical mechanical polishing abrasive to become a viscous suspension The amount of mechanical abrasive required for the mechanical-chemical abrasive becomes a viscous suspension varies according to the mechanical abrasive

  used and according to the silica content of the silica

  loïdale. Water or other diluents such as alcohols, solvents, etc. may be added to the mixture of mechanical abrasives and colloidal silica to reduce the viscosity of the mechanical-chemical abrasive. A low mechanical-chemical abrasive Viscosity is easily applied to parts It evenly covers parts and usually has better flow properties

and abrasion.

  The chemical mechanical abrasive of the present invention advantageously comprises from about 0.07 to about 2.0% by weight of a powdered mechanical abrasive, from about 13 to about 99.2% by weight of colloidal silica and about 0.7% by weight. about 85% by weight of water Water is preferably

deionized water.

  The chemical mechanical abrasive of the present invention is useful for polishing the surfaces of many different machined machined parts. The chemical mechanical polishing abrasive of the present invention can be used to polish the surface of any material that is capable of chemically reacting with a suspension of colloidal silica Examples of such a material include silicon (such as silicon in the form of slices), sapphire, metals, glass, alumina, silicon nitride (Si 3 N 4), gallium arsenide (GaAs), magnesium oxide (MgO), zirconium oxide and other ceramic and non-ceramic cured materials. The chemical mechanical polishing abrasive of the present invention can be used to polish cured parts by any polishing means known in the art of polishing hardened machined parts Polishing can be accomplished by any polishing means therein. included by hand, using a pad and the chemical-mechanical polishing abrasive, or machine using the abrasive of

  liquid chemical mechanical polishing of the present invention.

  It is preferable to use a pad in conjunction with a machine for polishing machined parts cured with the polishing abrasive of the present invention. The polishing abrasive is applied to the stamp or machined parts and the pad is then contacted by friction with at least one surface of the abrasive-coated parts during the polishing step The machined part is polished for a period of time sufficient for the surface of the

  piece is polished to a desired finish.

  Polishing conditions, including pressure and temperature, can affect the polishing speed of parts. However, the abrasive is effective in polishing machined parts over a wide range of pressures and temperatures. not required for

  the chemical mechanical polishing abrasive is effective.

  Some preferred examples of the invention are discussed below. However, many other examples would also fall within the scope of the present invention.

EXAMPLES

Example 1

  In this example, alumina (A 1203) was polished with various abrasives including mechanical abrasives.

  The abrasives have been evaluated for their ability to remove surface material from the surface of the present invention.

  machined parts of alumina, over time.

  The surface of the pieces of alumina has been prepared

  by grinding with 30 micron diamond particles

  meters contained in a hard polymer composite plate, followed by grinding with 6 micrometer diamond particles on a soft polymer composite plate After the preparation of the surface of the alumina, a Knoop mark was made in the machined part hardened with a load of 5 kg, the mark being made at a load speed of 70 pm / second with a load time

  15 seconds Material removal rates were determined by measuring the Knoop brand's diagonal length reduction over time.15 Vibration and semi-automatic polishing machines were used Vibration polishing

  It was used to minimize the mechanical contribution. The tests were monitored for 24 hours. Semi-automatic polishing apparatuses have been used to increase the mechanical contribution.

  The polishing was done on a canvas of

  polishing TEXMETQR) sold by the firm Buehler.

  A summary of the polishing results for machined parts of alumina is given in Table I below:

TABLE I

  Polishing rate Polishing Technique Abrasive (um / h) Polishing by Fe 2 03 0.002 vibrations Colloidal Silica 0.042 Fe 2 03 + (colloidal silica) 0.125 (Micrometers / minute) Mechanical polishing Fe 2 03 rotary nothing Colloidal silica 0.26 Diamond 1 / 4 gm none Diamond 3 μm 0.21 Fe 2 O 3 + (colloidal silica) 0.35 The results indicate that with vibration polishing or mechanical rotary polishing, the chemical mechanical polishing abrasive of the present invention

  comprising a suspension of colloidal silica in combination with

  With mechanical abrasive Fe 2 03 is able to polish alumina at a higher polishing rate than colloidal silica or Fe 2 O 3 alone. In addition, the polishing speed of the colloidal silica abrasive / Fe 2 03 is much higher than the cumulative polishing rates of colloidal silica and Fe 2 O 3 (0.125 gm / h against 0.044 gm / h for vibration polishing and 0.35 gm / minute against

  0.26 gm / min for rotary polishing.

  This example clearly demonstrates that the mechanochemical polishing abrasive of the present invention unexpectedly has a higher polishing rate than

  that of colloidal or mechanical silica abrasives,

individually or cumulatively.

Example II

  Using the same vibration polishing method as above, polished Knoop brand alumina, silicon nitride, and zirconium oxide samples were buffed using colloidal silica, various mechanical abrasives, and various abrasives.

  mechano-chemicals of the present invention.

  The chemical mechanical polishing media consisted of one liter of solution of grams of A 1203, Ce O 2, Cr 203 or Fe 2 O 3 together with 490 ml of an aqueous colloidal silica. From about 10.0, an average particle diameter of about 0.05 to 0.07 gm, a density of 1.390 and contained 50% solids, 5 ml of deionized water was added to the mixture to complete the formula. . Vibration polishing was used to polish the various samples for a period of 24 hours. The polishing rate of each abrasive in gm / ha was then determined. The vibration polishing results of the three samples are given in Table II below. :

TABLE II

  Mechano-chemical polishing rate (um / h) Alumina Nitride media Silicon zirconium polishing oxide A 1203 + colloidal silica 0.045 0, 163 0.173 This 203 + colloidal silica 0.027 0.300 0.1875 This 203 0.006 0.135 Fe 203 + colloidal silica 0.125 0.300 0.448 Fe 2 03 0.003 0.042 0.173 cr 203 + colloidal silica 0.148 0.188 0.233 Cr 203 0.00 0.058 0.00 (CS) colloidal silica 0.044 0.058 The colloidal silica used above is the same colloidal silica as is used in chemical mechanical polishing abrasive Water was not added to the colloidal silica prior to its use

for testing purposes.

  A suspension of each of the mechanical abrasives used in the test was prepared by adding 5 ml of deionized water to about 20 g of the powdered mechanical abrasive. The polishing pressures and temperatures were not critical to the results, but they were kept as uniform as possible throughout the test. The polishing temperature was maintained at approximately 25 ° C while the

  polishing was maintained at about 50 g / cm 2.

  In most cases, the chemical mechanical polishing abrasive of the present invention has polished each material at a higher speed than the colloidal silica or the mechanical abrasive, alone or with cumulative Ce 203 joined to silica. colloidal alone showed in polishing alumina a lower polishing speed

than colloidal silica alone.

Claims (12)

  1 chemical mechanical polishing abrasive, characterized in that it comprises a suspension of silica   colloidal and one or more mechanical abrasives.   A chemical mechanical polishing abrasive according to claim 1, further characterized in that the mechanical abrasive is selected from one or more of the group consisting of Fe 2 O 3, Fe 3 O 4, Mg O, BaCO 3,   Ca 3 CO 3, Mn O 2, Ce O, Si O 2, Ce O 2, Cr 2 O 3 and A 1203.   The chemical mechanical polishing abrasive of claim 1, further characterized in that   colloidal silica has a p H greater than 7.   A chemical mechanical polishing abrasive according to claim 1, further characterized in that the colloidal silica suspension is an aqueous suspension of colloidal silica.   Chemical-mechanical polishing abrasive, characterized in that it comprises an aqueous suspension of colloidal silica and a mechanical abrasive selected from one or more of the materials of the group comprising Fe 2 O 3, Fe 3 O 4, Mg O, BaCO 3, Ca CO 3, Mn O 2, Ce O, Si O 2, Ce O 2, Cr 2 O 3 and A 1203.   A chemical mechanical polishing abrasive according to claim 5, further characterized in that it contains about 0.07 to about 2.0% by weight of the mechanical abrasive and about 13 to about 99.2% by weight of the abrasive. an aqueous suspension of colloidal silica. A chemical mechanical polishing abrasive according to claim 5, further characterized in that   colloidal silica has a pH greater than about 7.0.   A chemical mechanical polishing abrasive according to claim 5, further characterized in that it has particle diameters of from about 0.1 to about micrometers.   A chemical mechanical polishing abrasive, characterized in that it comprises from about 13 to about 99.2% by weight of an aqueous suspension of colloidal silica having a p H greater than about 7, about 0.7 to about 85% by weight of water and about 0.07 to about 2.0% by weight of mechanical abrasive particles of about 0.1 to about 10 microns, the mechanical abrasive being selected from one or more of the materials of the group consisting of Fe 2 O 3, Fe 3 O 4, Mg O, BaCO 3, CaCO 3, MnO 2, CeO, SiO 2, CeO 2, Cr 2 O 3 and A 1203.   A chemical mechanical polishing abrasive according to claim 9, further characterized in that it has particles of diameter ranging from about 0.5 to about 5.0 microns.   The chemical mechanical polishing abrasive of claim 9, further characterized in that the mechanical abrasive is Fe 203.   Process for polishing a machined part, characterized in that it consists in using a chemical-mechanical polishing abrasive comprising a suspension of colloidal silica and one or more mechanical abrasives by application of the chemical-mechanical polishing abrasive to a workpiece and put in contact with this piece with a polishing means for a period sufficient to   polish at least one surface of the machined part.   13 Polishing method according to the claim   12, further characterized in that the mechanochemical polishing abrasive is applied to the polishing means.   14 Polishing method according to the claim   12, further characterized in that the polishing means is a mechanical means using a polishing pad. A method of polishing a machined part, characterized in that it consists in using a chemical-mechanical polishing abrasive comprising an aqueous suspension of colloidal silica and a mechanical abrasive selected from one or more of the materials of the group comprising Fe 2 O 3, Fe 3 O 4, O 2 O, BaCO 3, CaCO 3, MnO 2, CeO, SiO 2, CeO 2, Cr 2 O 3 and A 1203 by application of the mechanical-chemical polishing abrasive to a buffer placed on a mechanical polishing means and frictionally contacting the buffer of the mechanical polishing means with at least one surface of the machined part for a period sufficient to polish the surface of the machined part.