JPH0217303B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for use in supporting ultra-thin workpieces when both sides of the workpiece are polished with high precision using a double-sided polishing device such as a lapping machine. It concerns the carrier to be used.

[Prior art] The processing principle of a lapping plate is to sandwich a workpiece between upper and lower surface plates, and use abrasive grains (lap agent) to directly change the flatness of the surface plate.
The machining accuracy of the workpiece is determined by the following three factors.

(1) Planar accuracy of upper and lower surface plates.

(2) Abrasive grain characteristics.

(3) Circumferential speed and trajectory length associated with carrier motion.

Therefore, the planar accuracy of the upper and lower surface plates is maintained sufficiently for the required machining accuracy of the workpiece, and furthermore,
When abrasive grains with characteristics suitable for the workpiece material and machining accuracy are used (when the above factors (1) and (2) are sufficiently satisfied in terms of softness), the above factor (3) , that is,
Equalization of the resultant circumferential speed and trajectory length due to the relative movement between the carrier that holds the workpiece and the upper and lower surface plates is a condition for improving machining accuracy.

A conventionally known lapping machine has a plurality of carriers meshed with a sun gear located at the center and internal gears surrounding it, and a workpiece held by the carriers is machined on both sides by upper and lower surface plates. When performing two-way machining, the upper and lower surface plates are stopped and the sun gear and internal gear are rotated to create a planetary motion of the carrier's rotation and revolution. ing.

During the above processing, the center point of the carrier that makes planetary motion draws a perfect circular trajectory centered on the sun gear, and each point other than the center point of the carrier moves toward the center due to the movement accompanying the rotation. The trajectory length is larger than that of a point. That is, the trajectory length at the center point of the carrier is the smallest, and increases in proportion to the distance from the center. Therefore, the machining speed of the workpiece held by the carrier becomes partially uneven, and the machining accuracy decreases.

In addition, when machining using the 4-way method, the upper and lower surface plates are driven at the same time, but in general, the dimensions of the surface plates in this type of lapping machine are outer diameter / inner diameter = 2.5 ~
3, there is a speed difference of 2.5 to 3 times between the circumferential speed on the outer circumferential side and the circumferential speed on the inner circumferential side, and due to the influence of this speed difference, the machining accuracy becomes even worse. This will result in a decline.

In addition, such a double-sided polishing apparatus requires a carrier that is thinner than the workpiece, so a very thin carrier must be used when processing a workpiece that is as thin as a micron, such as a semiconductor wafer.

However, as the wall thickness of the carrier becomes thinner, its strength inevitably decreases, especially the strength of the teeth cut around it, making it more likely to break. There are many cases where this becomes difficult.

Therefore, the present inventor proposed a double-sided polishing device capable of solving such problems in Japanese Patent Application No. 59-211938. This uses a carrier with a larger diameter than the surface plate, and a ring-shaped gear attached to the outer circumference of the carrier meshes with an internal gear with a slightly larger number of teeth that is fixedly arranged around the surface plate. At the same time, an eccentric cam attached to the drive shaft at the center of the polishing section is brought into contact with the inner ring attached to the inner peripheral surface of the carrier, and the rotation of the eccentric cam causes the carrier to swing in the radial direction and The gear is rotated at a very low speed based on the difference in the number of teeth between the gear and the ring gear, and the workpiece held by the carrier is processed by upper and lower surface plates.

According to such a double-sided polishing device, by suppressing the rotation of the carrier as much as possible, it is possible to reduce local unevenness in workpiece machining speed and improve machining accuracy. By attaching the inner ring and the ring-shaped gear as separate members to the periphery, there are advantages such as the ability to form the carrier itself to be extremely thin.

However, when a large-diameter carrier is made of thin-walled steel plates, a decrease in its strength is unavoidable.
It is very difficult to maintain proper flatness in the carrier because the distortions caused when punching the workpiece holding hole and the distortions caused when the inner ring and ring gear were attached tend to remain. Furthermore, during the polishing process, abrasive grains flow in and out on the carrier and flow into gear meshing parts, cam contact parts, etc., which causes problems such as easy wear of movable parts.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned problems specific to thin-walled carriers, maintain high strength and excellent flatness, and prevent wear of moving parts caused by abrasive grains. The purpose is to obtain a carrier that is difficult to generate.

[Means for Solving the Problems] In order to solve the above problems, in the carrier of the present invention, the annular carrier body having a plurality of work holding holes is made larger in diameter than the surface plate by a thin metal plate. A ring-shaped gear that meshes with a pin wheel fixed around the surface plate and has a slightly smaller number of teeth than the number of pins of the pin wheel is fixed to the outer periphery of the carrier body, and a ring gear is fixed to the outer periphery of the carrier body. To this end, we have taken technical measures to fix the inner ring that comes into contact with the eccentric cam attached to the drive shaft in the center of the polishing section, and to form ring-shaped protrusions on the inner and outer peripheries of the carrier body. ing.

[Function] When the eccentric cam inscribed in the inner ring of the carrier rotates during polishing of a workpiece using the carrier, the carrier is pushed in the radial direction by the eccentric cam and engages with the pin wheel. It performs rocking motion in the radial direction while changing its position, and rotates at a low speed based on the difference in the number of teeth between the ring gear and the pin wheel. Therefore, the speed difference between the various parts of the carrier due to the rotation of the carrier is suppressed as much as possible, and the entire surface of the workpiece held by the carrier is processed under substantially uniform conditions by the upper and lower surface plates.

In addition, the abrasive grains supplied to the polishing part are blocked by the inner and outer protrusions provided on the carrier, and flow into the meshing part between the pin wheel and ring gear, the contact part between the inner ring and the eccentric cam, etc. This prevents the abrasive particles from abrading the various parts.

Furthermore, the above-mentioned protrusions on the carrier eliminate processing distortion of the carrier body and welding distortion with the ring gear and inner ring, increase the rigidity of the carrier body, and make it possible to form an extremely thin carrier.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

1 to 3 show a lapping machine 1 as a double-sided polishing apparatus equipped with a carrier 2 of the present invention, and this lapping machine 1 has the following construction.

That is, first to third drive shafts 5 to 7 connected to a drive source (not shown) are arranged concentrically and independently of each other in the center of the body 4 of the lapping board 1 via bearings 8 to 10. The first
A surface plate support 12 is attached to the upper end of the drive shaft 5, and an annular lower surface plate 13 is mounted on the surface plate support 12.
is fixed with a pin 14, an eccentric cam 15 whose contact portion is formed by a roller 16 is attached to the upper end of the second drive shaft 6, and a pawl 17a is attached to the upper end of the third drive shaft 7. The locking plate 17 provided with the locking plate 17 is attached, and the pawl 17a of the locking plate 17 is made detachable from the support plate 19 fixed to the annular upper surface plate 18 with screws 20. The upper surface plate 18 is configured to be driven by the third drive shaft 7 via the plate 19. In addition, the upper surface plate 18 and the lower surface plate 1
3 is formed to have approximately the same size.

Further, on the body 4, there is provided a pedestal 21 which also serves as a cover and has a cylindrical shape so as to surround the drive shafts 5 to 7.
A pin wheel 22 is fixed to the upper end of the frame 21. This pin wheel 22 has an annular receiving plate 23
At the top, a large number of pins 24, 24, ... are connected to the upper and lower surface plates 1.
3 and 18, and are arranged and fixed at regular intervals so as to be located concentrically.

On the other hand, as is clear from FIG. 4, the carrier 2 has an annular carrier body 30 formed of a thin metal plate such as a steel plate and having a diameter larger than that of the surface plates 13 and 18. A holding hole 31 is formed by punching, and a ring-shaped gear 32 having a slightly smaller number of teeth than the number of pins of the pin wheel 22 is provided on the outer periphery of the carrier body 30 so as not to overlap with the polished surfaces of the surface plates 13 and 18. At the same time, a surface plate 1 is attached to the inner periphery of the carrier body 30, that is, the edge of the center hole 33.
Inner ring 3 so as not to overlap the polished surfaces of 3 and 18.
The carrier main body 30 is connected to the ring gear 32 and the inner ring 34 by a stepped portion 32 provided on the ring gear 32 and the inner ring 34.
This is done by superimposing the ends of the carrier body 30 in a and 34a and spot-electrically welding them at several points P, to reduce the welding distortion at that time and the punching process for the workpiece holding hole 31. In order to eliminate machining distortion, protrusions 35, 3 are provided on the inner and outer peripheral parts of the carrier body 30, which protrude toward the upper surface after the ring gear and inner ring are attached.
6 are each formed by press working. These protrusions 35 and 36 not only remove the above distortion and maintain the tension and flatness of the carrier body 30, but also provide appropriate rigidity to the carrier body, whose flexibility increases due to thinning. It has the function of preventing the abrasive grains supplied to the polishing section from flowing in or out.

The carrier 2 has the ring-shaped gear 32 placed on the receiving plate 23 and partially meshes with the pin 24, and also has the eccentric cam 15 on the inner ring 34.
It is set on the lower surface plate 13 with the rollers 16 in contact with each other, and a workpiece 40 to be machined is fitted and held in each workpiece holding hole 31. At this time, the carrier 2 is eccentric by an eccentric amount E with respect to the center of the surface plates 13 and 18.

In the lapping machine having the above configuration, the drive shaft 6
When the eccentric cam 15 is rotated by rotating it in the direction of arrow A, the carrier 2 is pushed in the radial direction by the roller 16 of the eccentric cam 15, and the carrier 2 is moved in the range 2E while changing the meshing position with the pin wheel 22. As it sways,
It rotates in the direction of arrow B at a speed based on the difference between the number of pins of the pin wheel 22 and the number of teeth of the ring gear 32, and therefore the workpiece 40 held by the carrier 2 swings together with the carrier 2. While rotating around the drive shaft 6, its upper and lower surfaces are polished by upper and lower surface plates 13 and 18.

Here, the rotation speed N of the carrier 2 and the drive shaft 6
There is a relationship between the rotational speed n and Z ₁ : number of pins of the pin wheel Z ₀ : number of teeth of the ring gear, N=Z ₁ −Z ₀ /Z ₀ ×n, but Z Since ₁ −Z ₀ is a small value, the rotation speed N of the carrier 2 is the rotation speed n of the drive shaft 6.
It becomes extremely small. For example, Z ₁ = 64, Z ₀
= 60, n = 60r.pm, then N = 4r.pm.

Therefore, the effect on polishing of the difference in trajectory length of each part of the carrier 2 due to rotation of the carrier 2 can be almost ignored. , each workpiece 40 held by the carrier 2 is 2E
With a momentum of ×n, the entire surface is the upper and lower surface plates 13, 18
They will rub against each other almost evenly.

Even in the 4-way polishing process in which the upper and lower surface plates 13 and 18 are rotated, the influence of the rotation of the carrier 2 is almost eliminated, so the machining accuracy is improved compared to the conventional polishing process in which the carrier makes planetary motion at a high speed. .

Further, the abrasive grains supplied to the polishing section during the above-mentioned processing are stopped by the protrusions 35 and 36 on the carrier 2, and are stopped at the meshing portion between the pin wheel 22 and the ring gear 32, and between the eccentric cam 15 and the inner ring 33. This prevents the abrasive grains from flowing into the contact areas with the abrasive grains, thereby preventing the abrasive grains from abrading the various parts. Furthermore, the protrusions 35 and 36 maintain the tension and flatness of the thin carrier 2, and increase its rigidity, thereby improving the usability and durability of the carrier 2.

[Effects] Separately formed ring gears and inner rings are attached to the outer and inner peripheries of the carrier body, so the strength of the outer and inner peripheries of the carrier, where large forces are applied during driving, can be reduced by reducing the wall thickness of the carrier body. At the same time, the carrier body can be made as thin as desired depending on the workpiece, making it easy to obtain a carrier suitable for processing extremely thin workpieces. can.

In addition, since ring-shaped protrusions are provided on the inner and outer peripheries of the carrier body, the reinforcing effect of the protrusions increases the strength of the thin carrier and at the same time maintains the necessary rigidity. Moreover, the formation of these protrusions generates radial and radial tension in the carrier body, which causes distortion caused when punching the workpiece holding hole and when installing the ring gear and inner ring. Since the distortion is removed, the carrier can maintain sufficient flatness, and furthermore, the protrusions function as a wave barrier to prevent the abrasive grains on the carrier from flowing in and out during polishing. It is possible to reliably prevent movable parts such as the meshing part between the ring gear and the pin wheel and the contact part between the inner ring and the eccentric cam from being worn out by the abrasive grains.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the essential parts of a double-side polishing apparatus using the carrier of the present invention, Fig. 2 is a cross-sectional view of the main parts with the surface plate removed, Fig. 3 is a plan view thereof, and Fig. 4. is a partial cross-sectional view of the carrier. 2...Carrier, 6...Drive shaft, 13...Lower surface plate, 1
5... Eccentric cam, 18... Upper surface plate, 22... Pin wheel, 2
4... Pin, 30... Carrier body, 31... Work support hole, 32... Ring-shaped gear, 34... Inner ring, 3
5... Projection, 40... Work.

Claims (1)

[Claims] 1. An annular carrier body with a plurality of work holding holes is formed from a thin metal plate to have a larger diameter than the surface plate, and a pin wheel fixed around the surface plate is engaged with the outer periphery of the carrier body. At the same time, a ring-shaped gear having a slightly smaller number of teeth than the number of pins of the pin wheel is fixed, and an inner ring on which an eccentric cam attached to a drive shaft in the center of the grinding section comes into contact is fixed to the inner periphery of the carrier body. A carrier for a double-sided polishing device, characterized in that ring-shaped protrusions are formed on the inner and outer circumferences of the carrier body, respectively.