JPH10217075A - Sheet grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet grinding method capable of finishing the flatness of a grinding surface accurately by a simple processing. SOLUTION: A sheet 4 is fixed to the surface of a surface plate 1 through wax 3 (A). While the surface plate 1 is rotated and rotating wheels positioned oppositely to each other are rotated in the directions reverse to each other, the wheels are brought in contact with the surfaces of the sheet for grinding (B). In this case, a work deformation occurs on the sheet. When the wax is heated and the sheet is released from the surface plate, a warpage occurs for the sheet due to work deformation (C). Then the melted wax is re-cooled for solidification so as to fix the warped sheet as it is on the surface of the surface plate, and the same surfaces of the sheet are mirror-finished after re-ground (D). In this case, because a deformation which is a limit of causing elastic deformation is already applied to the sheet in the grinding in step (B), any new warpage will not occur even if the same surface is ground. Thus, because the surfaces are kept in such conditions as obtained before grinding, a desired flatness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for grinding a thin plate, and more particularly, to a method for grinding one surface of a thin plate and flattening the processed surface.

[0002]

2. Description of the Related Art In order to flatten the surface of a relatively small thin plate of a fired product such as fine ceramics, it is difficult to perform mechanical clamping. Is fixed by using wax, and the surface is ground in this state. However, in this method, processing strain remains in the thin plate due to the force applied to the thin plate during the grinding process. As a result, even if flattened with high precision while being fixed to the surface plate, if the wax is melted to release the adhesive force and the thin plate is removed from the surface plate, the thin plate will bend due to the processing distortion. As a result, desired flatness cannot be obtained. This phenomenon becomes more remarkable as the thin plate to be processed becomes thinner.

Therefore, in order to eliminate the influence of bending due to such processing distortion, both sides of a thin plate have conventionally been ground to obtain a desired flatness on one side. An example is shown in a flowchart of the thin plate grinding method shown in FIG. And the state of the thin plate obtained by performing each process is as shown in FIG.

As shown in FIG. 5A, a thin plate 4 made of fine ceramic is fixed to one surface of a surface plate 1 (opposite surface of a rotary grindstone) by using wax 3 (ST).
1). In this state, the surface of the thin plate 4 is pressed by pressing the rotating grindstone against the surface of the thin plate 4 fixed to the surface plate 1 while rotating the surface plate 1 and rotating the rotating grindstone in the opposite direction to the surface plate 1. After grinding for a predetermined amount, mirror finishing is further performed (ST2). The grinding process accumulates processing strain as an internal stress in the thin plate 4, but since the thin plate 4 is fixed by the wax 3, the thin plate 4 does not warp (FIG. 5B).

Next, the wax 3 is heated and melted to release the adhesive force to the thin plate 4 (ST3). Then
Due to the processing distortion occurring in the thin plate 4, the thin plate 4 is warped (warpage in a state where the center of the surface to be ground is dented) (FIG. 5C). Due to the warpage generated at this time, the thin plate 4
The flatness of the surface exceeds the standard (for example, about 200 nm).

Therefore, in order to eliminate such warpage, the thin plate 4
Is once removed from the surface plate 1 and washed to remove dust and wax generated by grinding the thin plate 4 (ST4). Then, the washed thin plate 4 is turned upside down and placed on the surface plate 1 again, and wax is fixed in this state (ST5, 6). Then, as shown in FIG. 5D, the thin plate 4 is fixed in a state of being curved upwardly. At this time, the degree of warpage is the same (t0) as in FIG.

In this state, the rotating grindstone is brought into contact with the thin plate 4 to grind the back surface of the thin plate 4 (the surface opposite to the surface ground in the previous step (ST2)) in the same manner as in step 2. Then, mirror finishing is performed (ST7). At this time, the grinding amount t is set to be larger than the warpage amount t0 caused by the surface grinding. Thereby, as shown in FIG. 5 (E), the curved upwardly convex portion (the portion indicated by the two-dot chain line) is removed, and the back surface of the thin plate 1 is processed to be flat.

After the wax 3 is heated and melted to release the adhesive force (ST8), the thin plate 4 is removed from the surface plate 1. Then, the flattening process is completed by washing the thin plate 4 (ST9).

In step 7, the back side grinding and
Processing distortion due to internal stress also occurs in the opposite direction during mirror surface processing, but since it has already been greatly curved due to distortion generated during processing on the front side, warpage generated when adhesive force is released Is small (see FIG. 5F). This allows
At least one surface (the surface referred to as the back surface in the above description) has a desired flatness.

The thin plate 1 can be used, for example, for a magnetic piece called a back bar, which is one of the cores which is a main component of a magnetic circuit in a bulk erase type magnetic head. In other words, the flat bar having a desired flatness on one side as described above is cut into thin bars by cutting the thin plate in parallel with the short direction, thereby forming the back bar.

Then, one side of the back bar having the flatness is formed into a flat chip core 3 having a substantially E-shape.
A magnetic circuit and a core of the magnetic head are formed by bonding to the tip of the leg of the book.

[0012]

However, in the above-mentioned conventional thin plate grinding method, the step of grinding the front side of the thin plate 4 and the step of grinding the back side of the thin plate 4 are performed separately. , A processing strain is generated in one direction, and the directions are reversed. as a result,
When the back side is ground, a new processing distortion is generated, and the warpage caused by grinding one side and the warp caused by grinding the opposite side are not balanced, and the thin plate 4 always warps. Would.

When the thin plate 4 is warped, the back bar formed from the thin plate 4 is also warped. Then, a gap is formed in the connection portion between the back bar and the E-shaped chip core, so that adverse effects such as leakage of a magnetic field occur, and the magnetic characteristics of the magnetic circuit in the magnetic head deteriorate. Also, when three leg pieces are to be joined with one back bar, if there is a warp, there is a possibility that any one leg piece cannot be joined. In particular, components such as a back bar are reduced in size due to the downsizing of the magnetic head accompanying the improvement in the magnetic recording density. Further, when further miniaturization is attempted, a problem of flatness also occurs on the chip core side. In addition, in order to grind both the front side and the back side as in the conventional case, it is necessary to turn the thin plate upside down during the grinding process, and accordingly, the thin plate is washed or wax is applied again. Fixing processing is required, and moreover, since a plurality of thin plates are fixed on the surface plate and are ground simultaneously, the "thin plate removal → washing → turning over → re-fixing" is performed individually for the plurality of thin plates. Is required. Therefore, the number of processing steps increases and the processing becomes complicated. In addition, grinding and mirror finishing must be performed on a surface that is not to be finally joined, which is wasteful processing.

The present invention has been made in view of the above-mentioned background, and has as its object to solve the above-mentioned problems and to perform complicated steps (such as steps for washing and reversing the grinding surface of a thin plate). Another object of the present invention is to provide a method of grinding a thin plate, which can eliminate the need for grinding and can finish the flatness of the ground surface with high accuracy.

[0015]

In order to achieve the above object, a thin plate grinding method according to the present invention is characterized in that a surface of a thin plate adhered and fixed on a surface plate with wax is ground,
Then, the adhesive force to the thin plate is released to generate a warp based on the processing distortion generated at the time of the grinding, and the warped thin plate is again fixed on the surface plate in the warped state, and the thin plate is fixed. The same surface is ground again (claim 1).

As a more specific example, a thin plate is bonded and fixed on a surface plate using wax, and the surface of the thin plate is ground. Next, the wax is heated to melt the wax and release the adhesive force to the thin plate, thereby causing a warp based on a processing distortion generated in the thin plate during the grinding. Thereafter, the wax is solidified by cooling, and the thin plate is again fixed on the surface plate in a warped state, and after grinding the same surface of the thin plate again, the ground surface is mirror-finished. Perform processing. Subsequently, the wax is heated and melted, and the thin plate is removed from the surface plate, and then the thin plate is washed (claim 2).

As the thin plate to be processed in the first and second aspects of the present invention, various types can be applied, and for example, a ferrite plate can be used (claim 3).

In the present invention, when a thin plate is fixed on a surface plate and the surface of the thin plate is ground, processing distortion is accumulated in the thin plate. During the grinding, the thin plate is bonded and fixed by wax, so that the warpage is reduced. Does not occur. When the adhesive force of the wax is released after the grinding, the thin plate is warped in accordance with the processing distortion. The processing up to this is almost the same as in the conventional case.

In the case of the conventional method, the thin plate is turned over and the back surface is ground thereafter. In the present invention, the thin plate is fixed again without turning over while warping is generated, and the same surface is ground again. It is characterized by:

That is, when the experiment was repeated,
There is a limit to the processing strain caused by internal stress generated when a thin plate is ground in one direction, and no further processing strain is accumulated even if grinding in the same direction (same surface) after grinding a predetermined amount I understand. In other words, if the thin plate warps to the limit of its own elastic deformation due to the processing distortion generated by grinding a predetermined amount, the thin plate cannot be further elastically deformed even if the same plane is subsequently ground, so that the warping also occurs. Will not occur. The present invention utilizes such a principle. As described above, after grinding a predetermined amount, the adhesive force is temporarily released, and warpage due to processing distortion is positively generated. Even if the surface is ground, no processing distortion is newly generated in the thin plate, and even if the adhesive force by the subsequent wax is released, the thin plate does not warp and maintains the flatness immediately after the completion of the processing.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an apparatus for performing a thin plate grinding method according to the present invention. As shown in FIG. 1A, the lower surface of the disk-shaped surface plate 1 and a part of the upper surface of the rotary grindstone 2 face each other and rotate with each other. Then, as shown in FIG. 1B, a thin plate 4 made of a plurality of fine ceramics to be processed is mounted on the lower surface of the surface plate 1 using wax 3. The wax 3 used at this time is of a hot-melt type and becomes solid at room temperature, and firmly adheres and fixes the platen 1 and the thin plate 4. For example, the wax 3 is easily melted by heating to about 100 ° C., and the adhesive force is reduced. The thin plate 4 is released. Of course, once released, when the thin plate 4 is left standing and cooled without being removed, the molten wax solidifies, and the thin plate 4 is fixed to the surface plate 1 again.

FIG. 2 is a flow chart showing one embodiment of the method for grinding a thin plate according to the present invention using the above-described apparatus. FIG. 3 shows the state of the thin plate 4 in each process performed by the thin plate grinding method according to the present invention.

As shown in FIG. 3A, first, a predetermined number of thin plates 4 are fixed to the surface plate 1 using wax 3 (ST1).
1). In this state, while rotating the platen 1 and rotating the grindstone 2 in the opposite direction, the rotating grindstone 2 is
To grind the thin plate 4 to a depth a (ST
12). At this time, the thin plate 4 undergoes processing distortion due to internal stress due to the force applied during grinding. However, the thin plate 4 is warped as shown in FIG. Maintain a flat state without any Up to this step, it is basically the same as the conventional one. However, the amount of grinding needs to be able to give at least a strain corresponding to the limit of elastic deformation for the thin plate 4 to be processed. In the case of a thin plate, the conditions can be adjusted without cutting a large amount. To be satisfied.

Conventionally, mirror finishing is performed after this.
In the present invention, the wax 3 is heated and melted without mirror finishing, and the thin plate 4 is released from the surface plate 1 (ST13). Then, the thin plate 4 is warped due to processing distortion generated inside the thin plate 4. The warpage is such that the periphery 4a of the thin plate 4
(FIG. 3 (C)) so as to be more distant from the mounting surface of the surface plate 1 than the center 4b of FIG. Then, the warp is a limit amount at which the thin plate 4 can warp. In the illustrated example, the amount of warpage is drawn large for convenience, but the actual amount of warpage (the interval between both ends 4a and the center 4b) is
For example, it is about 200 nm or less.

After the adhesive force is once released in this manner,
The wax 3 is cooled and solidified as it is, and the thin plate 4 is fixed on the surface plate 1 again in a warped state (ST1).
4). As a result, the amount of warpage generated at the time of release shown in FIG. Further, as is clear from the figure, the thickness of the wax 3 is set to be larger than the amount of warpage generated in the thin plate 4 so that even the warped thin plate 4 can be sufficiently fixed. .

In this state, the surface of the thin plate 4 (the same surface as the ground surface in step 12) is ground again to flatten the surface, and then mirror-finished (ST15). Thereby, as shown in FIG. 3D, the protruding ends 4a are removed, and the same flatness as the processing surface of the processing grindstone is obtained.

Thereafter, the wax 3 is heated and dissolved (ST)
16). Then, since the warpage generated in the thin plate 4 before the start of the grinding process in step 15 is the limit warp generated when the same surface side of the thin plate 4 is ground, the same surface of the thin plate 4 is newly ground. Even more, the distortion is thin plate 4
Therefore, if the desired flatness is obtained while the wax is fixed, the wax 3 is melted and the adhesive force to the thin plate 4 is released. The state after the mirror finishing is maintained, and high-precision flatness is obtained. After the wax 3 is melted as described above, the thin plate 4 is removed from the surface plate 1 and the thin plate 4 is washed (ST17).

The thin plate is ground by the above-described grinding method.
Since the mirror-finished thin plate 4 has good flatness, the back bar formed into a thin rod shape by cutting the thin plate 4 does not warp. Therefore, when forming the core of the magnetic head, an E-shaped chip core (R / W core,
Even if a back bar is connected to the (E core), there is no gap in the joint surface, and three leg pieces can be joined with one back bar without any problem, and the magnetic properties of the core are good. Can be The back side of the thin plate 4 that is not ground is curved, but when used for a back bar or the like as described above, there is no problem because the joining surface is one side.

Further, in the thin plate grinding method according to the present embodiment, the thin plate is turned upside down after the thin plate is once removed and cleaned after the first grinding process of the conventional method, or once after the surface side grinding and mirror finishing. Since there is no need to perform the process of mounting the components on the board again, the number of processes can be reduced (the number of processes is nine in the conventional process, but only seven in the process of the present embodiment). Moreover, since the process of once removing and cleaning is complicated, the total processing time spent for the thin plate grinding can be greatly reduced more than the effect of reducing the number of steps. Therefore, it is possible to reduce a time for manufacturing a product (for example, a magnetic head or the like) manufactured using a part formed from the thinned plate.
Further, since the flatness of the ground surface of the thin plate is good, a high quality product can be manufactured, and the yield is improved. The same effect is obtained even if the components are downsized.

[0030]

As described above, in the method for grinding a thin plate according to the present invention, the ground thin plate is once released, and the thin plate is positively warped. Since the same surface is ground again, the ground surface of the thin plate can be made flat. That is, the warpage that occurs when one surface is ground is the limit warpage that occurs when the same surface is ground. Therefore, even if the thin plate on which such warpage occurs is further ground, no further warpage occurs. Therefore, the flatness of the ground surface of the thin plate can be improved.

In the method for grinding a thin plate according to the present invention, the surface on which the thin plate is ground is single-sided, so that the thin plate is once removed from the surface plate as in the conventional thin plate grinding method. Therefore, the number of processing steps and labor can be simplified.

[Brief description of the drawings]

FIG. 1 is an apparatus for performing a thin plate grinding method according to the present invention.

FIG. 2 is a flowchart showing an embodiment of a thin plate grinding method according to the present invention.

FIG. 3 is a view for explaining an embodiment of a thin plate grinding method according to the present invention.

FIG. 4 is a flowchart showing a conventional thin plate grinding method.

FIG. 5 is a view for explaining a conventional thin plate grinding method.

[Explanation of symbols]

 1 surface plate 3 wax 4 thin plate

Claims (3)

[Claims] 1. A surface of a thin plate (4) adhered and fixed on a surface plate (1) with a wax (3), and then, the adhesive force to the thin plate is released to reduce processing distortion generated during the grinding. The thin sheet having the warpage is fixed on the surface plate again in the warped state, and the same surface of the thin sheet is ground again. Method. 2. A thin plate is bonded and fixed on a surface plate using wax, the surface of the thin plate is ground, and then the wax is melted by heating the wax to release the adhesive force to the thin plate. Thereby, a warp based on the processing strain generated in the thin plate at the time of the grinding is generated, and thereafter, the wax is solidified by cooling, and the thin plate is fixed on the surface plate again in a warped state, After grinding the same surface of the thin plate again, the ground surface is mirror-finished, and then the wax is heated and melted, and the thin plate is removed from the surface plate, and then the thin plate is washed. A method for grinding a thin plate, characterized in that: 3. The method for grinding a thin plate according to claim 1, wherein the thin plate is a ferrite plate.