JPH0659615B2 - Polishing method with flexible polishing sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention uses a flexible and highly durable polishing sheet that is particularly useful for precisely polishing the surface of electronic parts such as magnetic heads and silicon wafers. It relates to a polishing method.

[Prior art]

Conventionally, precision polishing methods for electronic or electric parts are
"A flexible polishing sheet with an abrasive-grain coating layer, in which various types of abrasive grains are applied in a thin layer with an adhesive to the surface of a relatively heat-resistant thermoplastic resin sheet (including tapes) such as polyester (Including polishing tape) ”, the surfaces of the flexible polishing sheet and the like and the surface of the substance to be polished to be polished are pressed against each other and relatively slid (rubbed) with each other,
A method of precision polishing the surface of a substance to be polished such as the electronic component into a mirror surface has been generally performed.

However, in the "known precision polishing method for the surface of electronic or electric parts, etc." that uses the above-mentioned known abrasive-coated flexible polishing sheet, i) during precision polishing, the abrasive coating of the polishing sheet is performed. The polishing layer itself of the known polishing sheet is not sufficient in durability of polishing performance, because the removal of the abrasive grains of the layer occurs relatively easily in a severe polishing state, ii) In addition, the above-mentioned abrasive coating The layer is not a layer having a sufficient thickness in general, and is usually a thin layer having a thickness of about 10 μm or less. Iii) Generally, the layer was first exposed on the outermost surface of the abrasive grain coating layer. Due to the fact that the known polishing sheet often loses the polishing performance due to the removal of the abrasive grains, the known polishing sheet cannot be reused repeatedly,
A large number of substances to be polished cannot be precision-polished one after another unless the abrasive grain-coated polishing sheet is used for precision polishing and then replaced.

Therefore, in the known polishing method, the efficiency in the precision polishing operation (in other words, the productivity of the polishing product) was extremely poor.

[Problems to be Solved by the Present Invention]

This invention, in the conventionally known polishing method, when precision polishing the surface of an electronic component or the like using a flexible polishing sheet, the abrasive grain coating layer is thin, and the abrasive grains in the abrasive grain coating layer are Since it is easy to fall off, for example, the polishing operation must be interrupted after each one to two times of precision polishing, and the polishing sheet must be replaced.
The efficiency of the polishing operation (the productivity of precision-polished products) was extremely poor, but it is an object of the present invention to provide a polishing method that solves this problem all at once.

[Means for solving problems]

The present invention has an average particle diameter in the range of 0.1 to 60 μm and 2 to 80% by volume of abrasive grains having a Knoop hardness of 1000 or more.
Of a polishing sheet obtained by surface-treating a flexible aromatic polyimide sheet having a thickness of 30 to 500 μm, which is uniformly dispersed and incorporated at least in the entire thickness direction at a blending ratio of The surface and the surface of the substance to be polished (material to be polished) to be polished are 50 to 2000 g / cm ²
Under pressure, the two are relatively slid while being pressed against each other to polish the surface of the substance to be polished until its maximum roughness (R _max ) becomes 20 μm or less. A polishing method using a sheet is provided.

The present invention intermittently provides a "flexible polishing sheet in which abrasive grains are uniformly dispersed in an aromatic polyimide sheet (including film, tape, etc.)" that has sufficient mechanical strength, heat resistance, polishing performance, etc. Alternatively, since it is a precision polishing method suitable for continuous and repeated use, it is an excellent polishing method with high productivity for polishing products such as electronic and electric parts.

In particular, in the present invention, a method of using a flexible polishing sheet containing a biphenyltetracarboxylic acid-based or pyromellitic acid-based aromatic polyimide in a state in which abrasive particles uniformly dispersed are firmly held is used for polishing. In addition, the aromatic polyimide itself constituting the polishing sheet has mechanical strength (especially tensile modulus, MIT folding strength, etc.), heat resistance (heat loss rate when heated to 500 ° C.), moisture resistance. It also has excellent properties (equilibrium moisture absorption at 25 ° C at 50% humidity), chemical resistance, etc., so it has excellent heat resistance at high temperatures, long-term polishing durability, chemical resistance to various polishing liquids, etc. Excellent polishing performance can be exhibited, and high productivity precision polishing can be achieved.

[Detailed description of each requirement of the present invention]

The polishing sheet used in this invention has an average particle size of 0.1 to 6
The abrasive having 0 μm is 2 to 80% by volume, preferably 5
At a compounding ratio of -60% by volume, at least uniformly distributed over the entire thickness of the polishing sheet and incorporated,
Thickness is 30 to 500 μm, preferably 35 to 350 μm
m, and more preferably about 40 to 200 μm, a flexible polishing sheet (film-shaped body, sheet-shaped body, tape-shaped body, etc.) made of a heat-resistant aromatic polyimide sheet such as biphenyltetracarboxylic acid type or pyromellitic acid type. Is included).

In addition, the polishing sheet used in the present invention has a thickness of 2 to 30 times, particularly preferably 3 to 20 times the average particle diameter of the abrasive grains contained therein. Preferred for.

The abrasive grains used in this polishing sheet may be abrasive grains having an average particle size of 0.1 to 60 μm, preferably 0.2 to 50 μm, and more preferably 0.4 to 40 μm. Artificial diamond, cubic boronite, carbon boronite, silicon carbide, chromium oxide, alumina, and the like, "abrasive particles having the above-mentioned average particle diameter, which are composed of abrasive particles having a Knoop hardness of 1000 or more, particularly about 2000 to 8000, are mentioned. You can

The abrasive grains may be abrasive grains in which an inorganic or metallic substance is coated on the entire surface of the abrasive grains.

In the polishing sheet, in addition to the high hardness abrasive grains, for example, graphite, SiO ₂ , SiC, Fe ₂ O ₃ , Cu,
A filler composed of Sn or a mixture thereof may be blended up to a blending ratio of about 20% by volume.

The aromatic polyimide which the polishing sheet mainly comprises is, for example, (A) 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 3,
"Biphenyltetracarboxylic acid or its dianhydride" selected from the group consisting of 3 ', 4,4'-biphenyltetracarboxylic acid and their acid dianhydrides, 2,3,3', 4'- Benzophenonetetracarboxylic acid, 3,3 ', 4,4'-benzophenonetetracarboxylic acid, and "benzophenonetetracarboxylic acid or its acid dianhydride" selected from the group consisting of acid dianhydrides, and pyro An "aromatic tetracarboxylic acid component" mainly containing "aromatic tetracarboxylic acids" selected from the group consisting of meritic acid, and (B) 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 2,2-bis (4-amido) Phenyl)
Aromatic diamines having two benzene rings such as propane, and 1 such as o-, m- or p-phenylenediamine
Using the monomer components (A) and (B) consisting of an "aromatic diamine component" containing an aromatic diamine compound selected from the group consisting of aromatic diamines having one benzene ring, It is a heat-resistant aromatic polyimide obtained by polymerizing and imidizing equimolar amounts. As the aromatic polyimide, a biphenyltetracarboxylic acid-based or pyromellitic acid-based high molecular weight aromatic polyimide is particularly preferable.

In particular, the biphenyltetracarboxylic acid-based aromatic polyimide has a logarithmic viscosity (measured at 50 ° C., concentration: 0.5 g /
100m solvent, solvent; parachlorophenol)
It is preferably 0.1 to 7, particularly preferably 0.3 to 5.

In the present invention, the above-mentioned aromatic polyimide has a “heat resistance” of 300 ° C. or higher, which is represented by the temperature until 5% by weight of the sample is reduced by heating when the sample is heated at 10 ° C./min.
Particularly, those having a temperature of 400 ° C. or higher are preferable, and those having an equilibrium moisture absorption rate (which is a moisture absorption rate which is reached by maintaining the environmental condition of humidity 50% and temperature 50 ° C.) is 2.0% or less,
It is preferable in terms of durability (heat resistance, retention of mechanical properties, etc.) after being molded into a polishing sheet.

In the present invention, the polishing sheet is such that the aromatic polyimide constituting the sheet contains about 50 mol% or more of 3,3 ', 4,4'-biphenyltetracarboxylic acid, pyromellitic acid, or a mixture thereof. , Particularly preferably 60
"Aromatic tetracarboxylic acid component", which is contained in an amount of at least mol%, more preferably 80 to 100 mol%, and an aromatic diamine having two benzene rings such as 4,4'-diaminodiphenyl ether, or paraphenylenediamine. About 5 aromatic diamines having one benzene ring such as
It is a high-molecular-weight aromatic polyimide obtained by polymerizing and imidizing an “aromatic diamine component” containing 0 mol% or more in approximately equimolar amounts, and thus the above-mentioned heat resistance, durability, mechanical properties, etc. In addition to the
That is, it is suitable in terms of stability of polishing performance of repeated use of the polishing sheet a plurality of times in precision polishing.

In the polishing sheet used in the present invention, "abrasive grains having a high hardness with a Knoop hardness of 3000 or more" such as the diamond described above are contained in the aromatic polyimide polishing sheet in an amount of about 2 to 6
The content of 0% by volume, preferably 5 to 50% by volume is preferable in terms of mechanical strength, flexibility, precision polishing performance and the like of the polishing sheet.

The method for producing the polishing sheet used in the present invention is, for example, in an organic polar solvent such as an amide solvent and a phenol solvent,
The above-mentioned abrasive grains are uniformly dispersed, and while the above-mentioned aromatic diamine component and aromatic tetracarboxylic acid component are added and dissolved in the dispersion liquid of the abrasive grains, 8
Both components are polymerized at a polymerization temperature of 0 ° C. or lower to produce a high molecular weight aromatic polyamic acid (aromatic polyimide precursor).
To prepare a solution of the aromatic polyamic acid in which the abrasive particles are uniformly dispersed, and form a liquid thin film on the support surface or the like from the polyamic acid solution in which the abrasive particles are dispersed. Then, finally, the liquid thin film is dried by heating to remove the solvent to form a solidified film, and the aromatic polyamic acid is imidized, and if necessary, heat-treated at a high temperature of about 200 to 600 ° C. Accordingly, a method for producing a flexible polishing sheet made of aromatic polyimide in which abrasive grains are evenly dispersed and incorporated in the entire polishing sheet in the plane direction and the thickness direction is preferable.

The aromatic polyamic acid in the polyamic acid solution used for forming the polishing sheet has an inherent viscosity (measurement temperature; 30 ° C., concentration; 0.5 g / 100 m solvent, solvent; N, N-dimethylacetamide). But about 0.1 to 7,
Particularly, it is preferable that the polymer has a high molecular weight of about 0.3 to 5, and the concentration of the polyamic acid in the solution is about 3 to 50% by weight.

In this invention, after the above-mentioned flexible aromatic polyimide polishing sheet is surface-treated in a state where the abrasive grains are exposed, the surface of the polishing sheet and the surface to be polished of the substance to be polished are pressed against each other and the two are opposed to each other. Used for polishing the surface of the substance to be polished, and further, without replacing the polishing sheet used for the above-mentioned polishing, in which at least the exposed abrasive grains of the outermost surface layer have fallen off. The same polishing as described above is intermittently or continuously repeated many times on the new surface of the polishing sheet until the mechanical strength of the polishing sheet becomes a mechanical strength that cannot be used for the above polishing.

The surface treatment of the polishing sheet is carried out by removing a thin layer of the aromatic polyimide on the outermost surface covering the abrasive grains of the surface layer with a suitable abrasive, and at least a part of the abrasive grains on the surface of the polishing sheet. Any known polishing means may be used as long as it can be exposed.

The polishing of the substance (article) to be polished in the present invention includes (i) fixing the surface-treated polishing sheet to an appropriate fixture in a tensioned state, and the surface of the polishing sheet (abrasive grains are exposed). Surface), while pressing the surface of the substance to be polished with an appropriate pressing force (for example, about 50 to 2000 g / cm ² ), move the substance to be polished back and forth, left and right,
A method of precisely polishing the surface of the substance to be polished by sliding them relative to each other, (ii) A long polishing tape wound in a roll around a supply reel is wound around a plurality of guide rolls, The surface of the polishing tape in a tensioned state during the above-mentioned running (the surface where the abrasive grains are exposed) while being wound on the take-up reel while being run under tension and running at an appropriate speed.
The surface of the material to be polished is about 50 to 2000 g / cm ² ,
Preferably, the pressing force of about 100 to 1000 g / cm ^{2 is applied,} or the pressing force of the substance to be polished is kept in the above-mentioned pressed state and the polishing tape is moved in a direction different from the running direction of the polishing tape. Precision polishing of the surface of the substance to be polished by mechanically sliding it, (iii) Wrap belt-shaped polishing tape around multiple guide rolls and run it with appropriate tension and at an appropriate speed. However, the surface of the material to be polished is pressed against the surface of the polishing tape (the surface where the abrasive grains are exposed) in a tension state during the above-mentioned running with a pressing force of about 50 to 2000 g / cm 3.
^At about ² , simply pressing or moving in a direction different from the running direction of the polishing tape while holding the pressed state of the substance to be polished, slide the both relatively and A method of precisely polishing the surface, (iv) fixing the polishing sheet in a tensioned state, and rotating or periodically reversing the fixed polishing sheet in at least a certain direction around a rotation axis orthogonal to the plane of the polishing sheet. Or, the fixed polishing sheet is reciprocated back and forth in the plane direction, and pressing force is applied to the surface of the polishing sheet (the surface where the abrasive grains are exposed) in a tension state during the rotation or reciprocating movement. About 50-2000g / cm ² ,
Precision pressing of the surface of the substance to be polished by sliding them relative to each other, either by simply pressing or by moving the polishing tape in the direction different from the moving direction of the polishing tape while holding the pressed state of the substance to be polished. And the like.

Since the polishing sheet of the polishing method of the present invention is flexible,
In particular, it can be suitably applied to precision polishing the surface of an electronic component such as a ferrite magnetic head having a curved surface to a mirror surface.

In the present invention, after the precision polishing as described above is performed once or twice using the flexible aromatic polyimide polishing sheet, (a) at least the outermost surface layer used for the above polishing is further polished. (B) The mechanical strength of the polishing sheet cannot be used for the above-mentioned polishing (for example, less than about 5 kg / mm ² without replacing the polishing sheet from which the abrasive grains exposed before use are removed). Tensile strength)
Until (c) the new polishing surface where the abrasive grains of the polishing sheet are exposed, the same precision polishing as described above is intermittently performed on the surface of the substance to be polished such as electric parts such as a magnetic head. Or continuously, many times (at least 3 times or more, preferably 3 to 3 times).
It is repeated 0 times, especially 5 to 20 times).

In the method of the present invention, the polishing of the substance to be polished is performed as a polishing sheet, and is long and narrow (width is about 10 cm or less, particularly 0.5 to 5 cm).
The tape-shaped or belt-shaped polishing sheet (about a certain degree) is used, and while the polishing sheet is continuously running in a tensioned state, the substance to be polished is pressed to continuously perform precision polishing of small electronic parts and the like. It is industrially preferable to repeat the above step many times.

In the polishing method of the present invention, the substance to be polished (article) to be polished includes various heads or magnetic heads for audio, VTR, computer, floppy, etc., or electrons such as magnetic disks, magnetic tapes, silicon wafers, etc. Alternatively, an electric component, ceramic, or the like can be given.

According to the method of the present invention, the maximum roughness (R _max ) of the surface of each of the above-mentioned various substances to be polished is about 20 μm or less, especially 15 μm.
Precision polishing can be easily performed to a mirror surface state of m or less.

〔Example〕

Hereinafter, the present invention will be described in more detail by showing examples of the present invention.

Example 1 A diamond powder having an average particle size of 5 μm was obtained from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether at a compounding ratio of 12.3% by volume. A “flexible aromatic polyimide polishing sheet (thickness: 70 μm)” uniformly dispersed and incorporated in a molecular weight aromatic polyimide was produced.

Further, various physical properties of the polishing sheet were measured, and the various physical properties are shown in Table 1.

The polishing sheet is fixed in a cylindrical shape in a tensioned state, and silicon nitride is pressed against the surface of the polishing sheet with a pressing force of about 300 g / cm ² while sliding to perform honing processing 1
With the honing process, once the time is polished once,
The surface of 10 of the silicon nitride was continuously polished 10 times or more.

1st, 2nd, 5th and 10th in the above polishing
Table 1 shows the polishing performance (grinding ratio) in the second polishing and the surface roughness (R _max ) of the polished silicon nitride.

The polishing sheet can be used for repeated polishing, and the polishing performance was measured. As a result, excellent repeated polishing performance for a long time at high temperature was obtained, and polishing was performed 10 times or more without replacing the polishing sheet. Could be done.

In addition, in the above polishing, the polishing sheet used for polishing 10 times had the physical properties that were sufficient for polishing.

Example 2 Made of a high molecular weight aromatic polyimide obtained from "3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine containing 12.3% by volume of diamond powder having an average particle diameter of 5 µm. Polishing sheet (thickness: 80μ
m) ”was manufactured.

Various physical properties of the polishing sheet were measured.
Table 1 shows those physical properties.

Using the above-mentioned polishing sheet, repeated polishing was carried out in the same manner as in Example 1, and the change in polishing performance was measured.

According to the results, the above-mentioned polishing sheet has excellent repetitive polishing performance at high temperature for a long time, and the physical properties of the polishing sheet are sufficient even after the 10th polishing. Since it was maintained, polishing could be performed 10 times or more.

Example 3 A polishing sheet made of a high molecular weight aromatic polyimide obtained from pyromellitic dianhydride and 4,4-diaminodiphenyl ether containing 12.9% by volume of diamond powder having an average particle diameter of 5 μm (thickness: 90 μm ) ”Was manufactured.

Various physical properties of the polishing sheet were measured.
Table 1 shows those physical properties.

Using the above-mentioned polishing sheet, repeated polishing was carried out in the same manner as in Example 1, and the change in polishing performance was measured.

The results show that the above-mentioned polishing sheet has excellent repeated polishing performance at high temperature for a long time, and the physical properties of the polishing sheet are sufficient even after the 10th polishing. Since it was maintained at 10, the polishing could be carried out 10 times or more.

Comparative Example 1 Using a known diamond-coated polishing sheet (the adhesive is a urethane-based adhesive), the same repeated polishing as in Example 1 was performed. The results such as the polishing performance are shown in Table 1.

In the repeated polishing using the known diamond-coated type polishing sheet, the polishing up to the second time could be performed for a while, but in the polishing after the third time, the surface of silicon nitride could be substantially polished. There wasn't.

Example 4 A long polishing tape formed from the polishing sheet used in Example 1 (thickness: 80 μm, width: 3 cm, length: 5000)
cm), wound around a supply reel in a roll, wrapped around a plurality of guide rolls, connected the tip to the take-up reel, and tensioned this polishing tape at about 20 cm / s.
While traveling back and forth at the speed of ec, the surface of the ferrite magnetic head was moved to about 25
While pressing with a pressing force of 0 g / cm ² , 20 pieces of ferrite magnetic heads were precision-polished continuously 20 times (polishing by reciprocating once for each polishing).

In the repeated precision polishing, the grinding ratio in the 10th precision polishing is 15 or more, and the surface roughness R _max of the ground ferrite magnetic head is about 5 μm or less,
Even in the 20th precision polishing, the above-mentioned grinding performance and the physical properties of the polishing tape were not substantially deteriorated.

[Operation and effect of the present invention]

In the conventionally known polishing method using the abrasive-coated abrasive sheet, the same abrasive sheet (including the abrasive tape) is repeatedly subjected to precision polishing a number of times as in the present invention. Since the abrasive coating layer in the polishing sheet is completely removed in an early stage, it was practically impossible, but in the method of the present invention, a thick aromatic polyimide containing abrasive grains is uniformly incorporated. Since a flexible polishing sheet is used, even if the surface layer of the polishing sheet is gradually ground by precision polishing, new polishable surfaces (surfaces with abrasive grains exposed) are formed one after another, Precision polishing can be repeated many times.

Therefore, according to the method of the present invention, since the polishing sheet can be continuously used for a long period of time without being replaced by the first or second use, various electronic parts (even those having a curved surface can be used). Precision polishing of the surface of a substance to be polished (e.g., good) can be efficiently performed intermittently or continuously, and an abrasive product can be industrially manufactured with high productivity.

Claims (1)

[Claims] 1. An abrasive having an average particle diameter of 0.1 to 60 μm and a Knoop hardness of 1000 or more is 2 to 80% by volume.
Of a polishing sheet obtained by surface-treating a flexible aromatic polyimide sheet having a thickness of 30 to 500 μm, which is uniformly dispersed and incorporated at least in the entire thickness direction at a blending ratio of The surface and the surface to be polished of the substance to be polished are pressed against each other at a pressing pressure of 50 to 2000 g / cm ² while relatively sliding the two,
The surface of the material to be polished has a maximum roughness (R _max ) of 2
A method for polishing with a flexible polishing sheet, which comprises polishing to 0 μm or less.