JPH02303744A - Vacuum chuck - Google Patents

Abstract

PURPOSE:To improve the precision of the shape of a workpiece after working by forming a plastic sintered body which has continuous holes and in which the supporting rigity for the workpiece is partially varied, as adsorbing surface. CONSTITUTION:After a metal mold is charged with trifluorinated ethylene chloride resin powder, cold press molding is carried out. After a molding body is heating-sintered in air, a desired sintered body 4 is obtained through turning. A stainless jig is attached onto the sintered body 4, and each porosity of the inside and outside diameter parts of the sintered body 4 is reduced, and Young's modulus and hardness are increased. Then, a desired vacuum chuck is obtained by attaching the sintered body 4 onto the top part 6 of a base plate 1 made of Al alloy. The surface of the vacuum chuck is superfinely turned to form an adsorbing surface, and an Al magnetic disc plate 7 is vacuum-adsorbed, and the both surfaces are superfinely turning-worked. Thus, the precision of the shape of a workpiece after working can be improved by partially varying the supporting rigidity of the vacuum chuck.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a vacuum chuck that utilizes the continuous pores of a sintered plastic body. It is used to adsorb the end face of an object that has the same hardness as the plastic being used, or an object that is harder than the plastic, and hold and fix it during processing or when measuring dimensions and shapes. Ru.

Therefore, the adsorbed material is plastic.

Soft metals such as aluminum and copper, iron, glass, semiconductor crystal materials such as silicon, gallium, arsenic, YAG,
Crystalline materials such as GGG, silicon carbide.

Examples include ceramics such as alumina.

[Conventional technology and its divisions] Types of chucks conventionally used include mechanical chucks, electromagnetic chucks, and empty chucks, among which vacuum chucks are suitable for thin non-magnetic materials. It has been used. Typical examples of suction targets include aluminum magnetic disks, glass for photomasks, and wafers made of crystalline materials such as silicon.

The shape and structure of the suction surface of a conventional vacuum chuck is a continuous vacuum groove with a geometrical shape containing scattered through holes or through holes. However, since the suction force of these is non-uniform, the suction surface and the object to be suctioned are deformed, which poses a problem in accuracy in ultra-precision machining. Therefore, porous materials such as sintered metal scraps and sintered ceramics, which have more uniform adsorption power, have been used. However, because these materials themselves have high hardness, if minute dust adheres to the suction surface.

Thin objects to be attracted are deformed and attracted, resulting in deterioration of shape accuracy after processing.

In addition, when adsorbing, holding, and detaching soft materials such as aluminum 12 and copper, these adsorbed objects may be damaged. Furthermore, when processing an adsorbed object, these sintered bodies have high support rigidity and low damping ability against vibrations, so automatic vibrations are likely to occur, making it difficult to process with high precision.

Therefore, porous bodies made of sintered plastics with low hardness and high attenuation have been proposed in Japanese Patent Laid-Open No. 63-21.0148 and other publications. However, when machining thin objects such as aluminum magnetic disk substrates, the edge of the thin object's machined surface has different boundary conditions depending on the supporting state, so it is difficult to use a vacuum chuck with low Young's modulus and hardness, such as plastics. , a phenomenon in which the flatness of the edge of the machined surface deteriorates significantly on the order of 0.1 μm occurs. For this reason, the recording area of the magnetic disk must avoid the edges, leading to a reduction in the recording area. Furthermore, from a macroscopic perspective, the deterioration in the flatness of the edge also led to the deterioration in the radial straightness of the disk.

Another problem is that when using plastic for the chuck material, it is important that it has excellent water, oil, and solvent resistance, and that dimensional changes do not occur, and that it is necessary to ensure the accuracy of the suction surface. Since the plastic chuck part needs to be fixed to a highly rigid metal base and then subjected to surface treatment, it is also necessary to have excellent adhesion properties. However, water resistance, oil resistance, solvent resistance, and adhesion properties are contradictory (
(For example, with conventional urethane resins that have adhesion properties, water resistance, oil resistance, and solvent resistance are sacrificed. As a result, the dimensions of the adsorption surface gradually change, and the area density of the adsorbed object after processing was leading to deterioration.

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the present inventors have conducted various studies on vacuum chucks that utilize the continuous pores of a sintered plastic body. It was discovered that this problem could be solved by partially changing the support rigidity, and the present invention was completed.

The gist of the present invention resides in a vacuum chuck characterized in that the suction surface is made of a plastic sintered body with continuous pores whose supporting rigidity for an object to be suctioned is partially changed.

Describing this in detail below, in order to obtain the vacuum chuck of the present invention, first a plastic sintered body is manufactured by sintering fine powdery plastic particles. The plastic sintered body is formed into continuous pores by cold compaction and heating sintering in a non-oxidizing atmosphere according to conventional methods.

Next, as shown in the example of the aluminum magnetic disk substrate mentioned above, as a result of various studies, we found that the problem of flatness deterioration near the edges could be improved by increasing the support rigidity of the chuck part corresponding to the deteriorating part. could be prevented.

That is, deterioration can be prevented by partially and intentionally adjusting the reaction force caused by the elastic compressive deformation of the suction surface when the suction target is vacuum suctioned. There are two ways to change the support rigidity: change the physical properties such as Young's modulus and hardness, and change the chuck thickness.
■It is Noh. The former can be further determined by the following two methods if
It is Noh. (1) By partially changing the compression ratio of the mold during powder compaction to increase the density, or by partially reheating a sintered body with uniform porosity to soften and compress it and reduce the porosity. This increases Young's modulus and hardness. (2)
The continuous pores of a sintered plastic are partially impregnated with another plastic and solidified to increase Young's modulus and hardness.

The plastics used in the above-mentioned present invention are, for example,
Fluororesin, polyvinyl chloride resin, polyethylene resin,
Examples include polypropylene resin, polycarbonate resin, epoxy resin, etc. These resins have excellent water resistance, oil resistance, and solvent resistance, and have very little change in one dimension, which is essential for ultra-precision processing. However, there is a problem of poor adhesion, and to solve this problem, the particle size and porosity of the raw material powder of the plastic sintered body are adjusted so that the adhesive penetrates into the continuous pores to an appropriate depth. I did it like that. As a result, the adhesive hardens.

The anchoring effect was demonstrated and sufficient anchoring force was obtained.

[Example] Next, the vacuum chuck of the present invention will be explained in more detail with reference to an example.

FIGS. 1 and 2 are perspective views of an embodiment of the present invention, and FIG. 3 is a partially cutaway perspective view of a conventional example.

Example 1 Trifluorochloroethylene resin powder with an average particle size of 100 μm was filled into a mold, cold press molded at a required pressure of 120 kgf/d, and the molded body was heated in air at 215° C. for 3
After heating and sintering for an hour, it is turned and has an outer diameter of 96 m and an inner diameter of 24 m.
A sintered body 4 made of copper and having a thickness of 3+m was manufactured (see FIGS. 1 and 2). This sintered body had a porosity of 40%, an average pore diameter of 20 μm, a Young's modulus of 40 kgf/an'', and a Shore D hardness of 55. In order to increase the hardness, the porosity was reduced by softening and compressing by contacting a stainless steel jig at 400°C with a pressure of 30 kgf/d for 3 seconds.This operation reduced the outer diameter to 9.
4.6ny+i, and the inner diameter was 25.4mm. The region 5 where a decrease in porosity is observed is within a depth of 1 m from the surface, and the range within a depth of 0.4 mm from the surface has a porosity of 0%.
Met. The part with 0% porosity has a Young's modulus of 200 kgf/
mm2, and Shore D hardness was 87.

Next, an epoxy resin adhesive was applied to the peak portion 6 of the aluminum alloy base plate 1, and the sintered body 4 was adhered to form a vacuum chuck. At this time, the adhesive is applied to the continuous pores of the sintered body.
The adhesive penetrated to a depth of 2 mm, and as a result of a peel test, it was confirmed that the adhesive part did not peel off, indicating that the sintered body was destroyed and that the adhesive strength was sufficient.

The vacuum chuck manufactured as described above was attached to an ultra-precision lathe equipped with vacuum piping (not shown in FIG. 2), and the surface of the sintered body was turned with ultra-precision to form a suction surface. A 3.5-inch aluminum magnetic disk plate 7 was vacuum-adsorbed using the vacuum holes 2, vacuum grooves 3, and continuous pores of the sintered body 4, and ultra-precision turning was performed on one side and both sides using a diamond cutting tool. The size of the disc plate is 95mm outer diameter, 25mm inner diameter, 1.27n+w+ thickness, and 0 chamfers on the inner and outer diameters.
．． It is 35011. The results of turning are shown in Table 1.

Table 1: Outer peripheral flatness and radius straightness of 3.5-inch aluminum magnetic disk substrate Machining conditions Rotation speed: 3000 rpm Feed amount: 1O
μ error/rev Feed direction: Depth of cut from inner circumference to outer circumference = 10 μm Cutting oil: White kerosene spray Bit: Single crystal diamond bit 2m wide flat bite Vacuum degree: 360 mm Hg Example 2 Tetrafluoroethylene resin with average particle size of 250 μm The powder was filled into a mold, cold press molded at a required pressure of 100 kgf/cd, and the molded product was heated in air at 380°C.

After heating and sintering for 3 hours, the porosity is 50% and the average diameter of the pores is 5.
5μ SHOR, Young's modulus 20kgf,
] A sintered body with a hardness of 48 was produced. The size of the sintered body was an outer diameter of 92°6 mm, an inner diameter of 27.4 nn, and a thickness of 3 m. In order to increase the Young's modulus and hardness of the outer and inner diameter portions of this sintered body, an injection molding machine is used to apply trifluorochloride ethylene resin to the outer and inner diameter surfaces of the sintered body using a conventional method. Outsert injection molding was performed. Injection conditions are injection pressure 800kg.
f/cm, the mold and sintered body temperatures were 80°C, the cylinder temperature was 260°C, and the nozzle temperature was 310°C.

After injection molding, strain relief annealing was performed at tgo°C for 2 hours. As a result, the injected resin entered the continuous pores of the sintered body by 0.2 m and was firmly fixed.

The injection part had a Young's modulus of 210 kgf/mm" and a shore D hardness of 88. The extra injection molded part of the 0th order was turned, and the outer diameter was 94.6 mm, the inner diameter was 25.4 mm, and the thickness of the injection molded part 5 was 1 m. Using the same method as in Example 1, the sintered body was bonded to a chuck plate to form a vacuum chuck, and a 3.5-inch aluminum magnetic disk plate was subjected to ultra-precision turning.The results are shown in Table 1. show.

Example 3 Polyvinyl chloride resin powder with an average particle size of 130 μm was filled into a mold, cold press molding was performed at a required pressure of 180 kgf/ad, and the molded product was heated to 115 μm in a nitrogen gas atmosphere.
After heating and sintering at 10°C for 3 hours, it was turned to form a piece with an outer diameter of 94.6 cm, an inner diameter of 25.4 m, a thickness of 3 cm, a flange-shaped portion 10 of a thickness of II m, and a width of 1.5 m as shown in Fig. 2. A sintered body was produced. This sintered body has a porosity of 30% and an average pore diameter of 15 μm.
, Young's modulus 60kgf/■2. The Shore D hardness was 58.Next, epoxy adhesive was applied to the peak portions 6 of the aluminum alloy chuck plate 1, and the sintered body 4 was adhered to form a vacuum chuck. At this time, the adhesive was applied to the continuous pores of the sintered body by 0.3 m.
It was confirmed that the adhesive strength was sufficient.

The vacuum chuck manufactured as described above was mounted on an ultra-precision lathe in the same manner as in Example 1, and the surface of the sintered body was ultra-precision turned to form a flat suction surface, and a 3.5-inch aluminum magnetic disk plate was attached. Performed ultra-precision processing. The results are shown in Table 1.

Conventional Example A vacuum chuck made of hard polyurethane resin was manufactured as follows. 50 g of liquid base polyester was heated to 85°C, and 6.35 g of methylene bis-orthochloroaniline as a hardening agent was heated and dissolved at 120°C and added thereto.
After mixing and defoaming, pour into a suitable mold and heat at 120℃ for 5 minutes.
By heating and curing for a period of time, a hard polyurethane resin with an outer diameter of 100+ m and a thickness of 3 mm was produced. This resin has a Young's modulus of 1.7
kgf/=2, and shore D hardness was 42.

Next, this resin 8 is bonded to a third layer using a rigid rubber adhesive.
After adhering to the chuck base plate 1 shown in the figure, turn the outer diameter to 9.
4.6. The inner diameter was set to 25.4++a, and vacuum holes 2 and vacuum grooves 9 were further processed to form a vacuum chuck.

The conventional vacuum chuck manufactured in this way was mounted on an ultra-precision lathe, and the suction surface was machined, and then the aluminum magnetic disk plate was machined. The results are shown in Table 1.

The flatness of the outer peripheral part of the conventional example is 0.05 to 0.22 μm/3a
m, whereas the flatness of the outer peripheral portion of Examples 1 and 2 could be suppressed to within 0°1μ lotus/3 squares. Regarding the radius straightness, the conventional example had a value of 0.8 to 2.1 .mu.l/35 m, whereas the example was able to suppress the radius to within 1 .mu.s+/35 m. In addition, when the plastic sintered body shown in Example 1 of the present invention is used, the outer diameter of the chuck is 92.5 m, and the outer end of the disk is made to overhang the chuck by 0.9 m to eliminate the effect of supporting rigidity. .

The flatness of the outer periphery after disk processing is 0.2 to 0.5 μm1
/3■, and no effect was observed. Therefore, in the example of an aluminum magnetic disk substrate, the outer peripheral portion has a Young's modulus of 100 kgf/a++ or more and 2. Shore D hardness 45
The above is desirable. Here, as in Examples 1 and 2, providing portions with 0% porosity on the outer and inner peripheries of the vacuum chuck also has the effect of reducing vacuum leakage from the chuck.

Further, even by reducing the thickness of the outer peripheral part of the sintered body as in Example 3, it was possible to suppress the flatness of the outer peripheral part to within 0.1 μm/3 m and the radius straightness to within 1 μl/35-. On the other hand, if the thickness of the outer periphery of the sintered body remains unchanged at 3 mm, the flatness of the outer periphery will be 0°08 to 0.25 μm/
It was 3m long and had deteriorated.

The above is an example in which an aluminum magnetic disk substrate is processed. Next, lapping processing of a silicon wafer, which is a semiconductor crystal material, will be explained.

Example 4 The manufacturing method and material 1 mechanical strength of the porous sintered body constituting the vacuum chuck and the portion with increased Young's modulus and hardness of the outer periphery were the same as those shown in Example 1. The cross-sectional configuration of the vacuum chuck is also the same as in Example 1, but it has a disc shape with a diameter of 102 cm. This vacuum chuck was attached to a lapping machine and the sintered body was wrapped to form a suction surface. A silicon wafer with a diameter of 102+m was placed on top of this at a vacuum level of 50.
Alumina abrasive grains with an average particle diameter of 16 μs, which were vacuum chucked with 0nn Ilg and dispersed in water, were dropped in an appropriate amount onto an alumina lap plate while processing at a processing pressure of 0.07 kgf/d.
Wrap speed 4011/l1in, processing speed 44/+mi
Wrapping processing was performed with a processing allowance of 50 um.

As a result of this processing, the flatness of the outer peripheral part of the silicon wafer is 0.
05-0.08pm/3m++.

On the other hand, when the Young's modulus and hardness of the outer circumferential portion of the chuck were not increased, the outer circumferential flatness of a silicon wafer subjected to similar lapping was 0.11 to 0.15 μm and 73 m, which was poor.

[Operations and Effects] The vacuum chuck using the plastic sintered body of the present invention was able to improve the accuracy of the shape of the object to be attracted after processing by partially changing the support rigidity. Furthermore, even if the plastic material does not have adhesive properties, by adjusting the size and porosity of the pores in the plastic sintered body, the two adhesives can enter the pores, exert an anchoring effect, and create a vacuum. Can be glued to the base plate of the chuck. Therefore, a plastic sintered material with excellent water resistance, oil resistance, and solvent resistance can be used, and the shape accuracy of the suction surface can be maintained for a long period of time.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, and FIG. 3 shows a conventional example, each of which is a partially cutaway perspective view. 1...Base plate, 2...Vacuum hole, 3...Vacuum groove. 4... Plastic sintered body, 7... Adsorbed object,
8...Hard urethane resin, 9...Vacuum groove. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) partially changing the support rigidity for the adsorbed object;
A vacuum chuck characterized by a suction surface made of a sintered plastic body with continuous pores. 2) The vacuum chuck according to claim 1, wherein the continuous pores of the plastic sintered body are partially impregnated with another plastic and solidified, and the vacuum chuck has an adsorption surface whose adsorption property is improved by an anchoring effect.