JPS62157778A - Grindstone - Google Patents

Abstract

PURPOSE:To reduce the formation of the projection part after the completion of the trepanning work by making the thickness of the top edge of the grinding part thinner than that of other parts and markedly reducing the radius of the roundness due to abrasion to the min. which can be ignored. CONSTITUTION:A grinding stone is fed in the direction of arrow 13, revolving in the direction of arrow 12 around the revolution axis line 11, and trepanning work is carried out for a silicone wafer 15 attached onto a base 14. Then, the top edge of the second grinding part 2 is rounded through abrasion, accompanied with the advance of the work. Since the radius of curvature of the rounded corner part 16 is 12mum or so, the radius of curvature of the projection part formed onto one edge surface side of the pellet 17 punched out through trepanning becomes 12mum or less, and can be ignored. Therefore, the generation of damage such as crack and chipping on the projection part can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides a method for making pellets for thyristors, for example, silicon (
Old) Way... Cutting out ((trepanning;
Regarding grinding wheels used for trepanning.

[Technical background of the invention and its problems]

Thyristors are generally used for high power control.
The raw material for (lister) is obtained by trepanning with a cylindrical diamond grindstone. That is,
As shown in the bottom of Figure 3, first, the St wafer (A) is fixed to the base (B) K with adhesive, and the diamond grinding wheel (C) for trepanning is rotated while being fed in the direction of the arrow CD. , a disc-shaped pellet (E) was cut out.

However, the conventional diamond grinding wheel (C)
When one way (A) is cut out, a rounded corner (F) is generated at the cutting edge as shown in FIG. In other words, since the side wall of the diamond grindstone (A) is relatively thick, the edge of the diamond grinds away due to long-term use, forming an R section. Therefore, the shape of the cut out pellet (E) has a protrusion (G) projecting like a flange on one end surface, as shown in FIG. As a result, when adhering to a molybdenum (Mo) substrate, damage such as cracks or breakage occurs in the protruding portion CG), which causes pellet defects. Therefore, in the past, the protruding portions CG) were removed one by one by grinding.

However, since this reduces production efficiency, improvements are desired.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a grinding wheel that can reduce the formation of protrusions after trepanning processing of 8i wafers.

[Summary of the invention]

The tip of the grinding wheel for trepanning is made thinner than the other parts, so that the radius of rounding due to wear is minimized to the extent that it can be ignored.

[Embodiments of the invention]

Hereinafter, a grinding wheel according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2 show the grinding wheel of this embodiment. This grinding wheel has a bottomed cylindrical first grinding part (1) and a first grinding part integrally formed at the tip of this first grinding part (1).
The second grinding part (2) is a circular ring with a thinner thickness like the grinding part (1).
), and a cylindrical mounting part (4) coaxially and integrally connected to the bottom plate (3) of the first grinding part (1) and attached to the main shaft of a grinding device (not shown). However,
The first grinding part (1) has a side wall thickness of 0.6rnx.
The first support (5) has a cylindrical shape with a bottom and is made of metal such as steel, and the first support (5) is coated on both the inner and outer surfaces of the first support (5). The first abrasive layer (
6) It consists of. The thickness of the cylindrical side wall of the first support (5) is, for example, about 0.5 mm. On the other hand, the first abrasive grain layer (6) is composed of diamond abrasive grains with a grain size number of #800, for example, which are evenly dispersed and fixed to the first support (5). The first abrasive layer (6) is made of abrasive grains (a binder (8) made of brass, copper, etc. that maintains strength). The second grinding part (2) has a thickness of about δμm and has a length of 1.Jl that continuously protrudes from the tip of the support (5). A cylindrical second support with a diameter of 500 μm and a thickness of approximately 500 μm (
9) and a second abrasive layer 0I deposited on both the inner and outer surfaces of the second support (9). The second support (9) is set so that its inner peripheral surface is flush with the inner peripheral surface of the first support (5). Further, the second abrasive grain layer α1 has the same configuration as the first abrasive grain layer (6) except for the difference in thickness, so the description thereof will be omitted.

In the grinding wheel having the above configuration, while rotating the rotation axis υ in the direction of the arrow a,
When trepanning the St raw material a9 bonded to the base α4, as the process progresses, the tip of the second grinding part (2) becomes rounded due to wear, as shown in Figure 2. . However, the radius of curvature of this rounded corner portion (1e) is approximately 12 μm at most.

Therefore, the pellet α cut out by Trebanning
The radius of curvature of the protrusion formed on one end surface of η is 12μ
m or less, and becomes almost negligible. Therefore, damage such as cracks and chipping does not occur due to the protrusions. Therefore, the step of removing the protruding portion by post-processing becomes unnecessary, which can contribute to improving production efficiency. Furthermore, fewer pellet defects lead to improved reliability of other wafer products, such as thyristors.

In addition, in the above embodiment, the first and second abrasive grain layers (6
Although metal is used as the binder for ) and H, resinoid may also be used. Also, instead of diamond abrasive grains, borazone (boron nitride, BN), aluminum oxide (
Aj'z03), silicon carbide (SiC) may also be used.

Furthermore, if the thickness of the second grinding part (2) is less than 1 μm, the protrusion formed on the pellet can be ignored.

〔Effect of the invention〕

In the grinding wheel of the present invention, the thickness of the tip of the grinding portion is reduced to less than 10 μm, so that the protrusion generated on the pellet after trepanning is negligible. therefore,
This eliminates the need for post-processing to remove protrusions, helping to improve production efficiency. In addition to improving the yield of pellets, it is also possible to improve the reliability of products using these pellets.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a grinding wheel according to an embodiment of the present invention, FIG. 2 is an enlarged view of the main part of FIG. 1, FIG. 3 is an explanatory diagram of trepanning processing of an 8i wafer, and FIG. Fig. 5 is an enlarged view of a pellet obtained by conventional trebanning processing. (1)...First grinding section, (2)...Second grinding section, (
4)...Mounting part. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana ++ 1st Prisoner Figure 2

Claims (2)

[Claims] (1) A hollow cylindrical grinding section having at least one end serving as a grinding section for trepanning processing, and a mounting section coaxially connected to the other end of the grinding section and attached to a grinding device. . A grinding wheel, wherein one end of the grinding part is formed to have a thinner wall thickness and a smaller outer diameter than the other part. (2) The grinding wheel according to claim 1, wherein the thickness of one end of the grinding portion is 50 μm or less.