JPH0710495B2 - Polishing guide resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to the manufacture of thin film magnetic transducers, and in particular to the throat of a throat obtained by grinding the transducer gears to final dimensions. The present invention relates to an electric polishing guide mechanism that enables accurate height measurement.

The thin film converter performs high density data recording on a magnetic disk medium. The thin film converter is manufactured in a lump by providing a plurality of thin film conversion elements that are aligned in common with parallel pole pieces on a single substrate. The entire substrate is ground along a plane approximately parallel to the transducer pole tips. Much of the conversion efficiency depends on the length of the converter gear, called the final throat height. Precise control of the length of this converter gear will give optimum conversion efficiency.

B. Prior Art The prior art for measuring the distance ground to control its final throat height utilized an electrical grinding guide mechanism. These mechanisms have generally utilized a first and a second resistance element called a polishing guide resistor having ends parallel to the polishing surface provided at both ends of the substrate. During fine polishing of the substrate, the end of the resistor that supports the pole tip is also polished, causing a change in resistance proportional to the polished distance. The position of the polished end with respect to the final throat height is monitored by measuring the resistance of each resistive element.

In rough polishing in the early stages of polishing, the electrical polishing guidance mechanism provides a rough, polishing indication by producing a well-defined and detectable step change in resistance. The step change is obtained by placing an electrical element, which is destroyed by the polishing at a known distance from the final polishing surface, in parallel with the polishing guide resistor. Such a polishing guide mechanism is disclosed in U.S. Pat. No. 3,821,815.

C. Problems to be Solved by the Invention These conventional polishing mechanisms that utilize resistors to measure the polishing distance to the final throat height are rectangular in shape and as a function of the polished distance. It causes a non-linear resistance change. These non-linearity measurements impose limits on obtaining very accurate throat height tolerances. In rough polishing, the slope of resistance versus polishing distance is steep enough to make the measurement of polishing distance very inaccurate. At the final polishing stage, the resistive element provides a very flat resistance-to-polishing distance characteristic, making the final measurement of throat height vague. Therefore, these resistance elements have only a small polishing range.

Accordingly, it is an object of the present invention to provide a method for accurately measuring the polishing distance in the manufacture of mass-produced thin film magnetic heads.

Another object of the present invention is to provide an electrical polishing guide resistor having a resistance that varies linearly over the distance being abraded.

D. Means for Solving the Problems These aims are met by the abrasive guide resistor according to the invention. An electrical polishing guide resistor is provided that produces a substantially linear change in resistance as a function of polishing distance.
The resistors are placed on either side of the transducer array. During polishing of the substrate of the transducer array, the resistance of the resistor changes to represent the position of the polished tip. The change in resistance monitored will provide an accurate measurement of the throat height of the transducer array.

In the preferred embodiment of the present invention, a chrome resistor is attached to each end of the transducer array. The resistors are configured so that their effective length increases as the effective width of the resistor decreases during polishing. As such, the change in resistance is nearly linear, increasing the resolution of the control of the polishing distance and extending the polishing distance for which resistance measurement is available. This embodiment has a pair of discrete conductors. The conductors are located along the first and second tapering converging tips of the chrome resistance material deposited to form a polishing guide resistor with the conductors. The tip of the resistor converges toward the tip of the substrate surface to be polished. The back end of the resistor is parallel to the surface to be polished. Preferably, the slope of the first and second converging tips of the resistor decreases rearward, making the resistance change versus polishing distance more linear. When polishing begins, the resistor is also polished and the resistance change between the conductors is measured, which is proportional to the polished distance. The unique slope of the resistor end provides a linear resistance change as polishing progresses.

In another embodiment of the present invention, an electrical abrasive guide resistor comprises a first rough abrasive resistive portion adjacent a second fine abrasive resistive portion. The rough abrasion resistant portion has an end of the fine abrasion resistant portion and a continuous wide base edge and two further edges that converge toward the polishing surface. Coarse polishing resistors provide a resistance-to-polishing distance slope of less than 0.1 ohm / micron during the initial stages of polishing. In the final polishing step, the fine abrasion resistant portion provides a resistance change of about 25 ohms / micron.

E. Example Referring to FIG. 5, one end of a substrate 11 having a plurality of thin film transducers 12 attached thereto is shown. The final throat height 1 of the pole face 12a of the transducer 12 parallel to the polished surface 11a of the substrate 1
An electropolishing guide resistor 14 is shown having a tip 14a parallel to 5. The resistor 14 is a metallic material, preferably chrome,
On the substrate and consisting of a resistor 14b bounded by two conductors 16,17. The resistance ratio of chromium resistors to those conductors is 2: 1. A similar abrasive guide resistor is also provided at the opposite end of substrate 11.

When polishing the substrate 11 to obtain the final throat height of the transducer 12, a coarse polish of up to about 10 .mu.m can be achieved by optically monitoring the position of the polished tip. At the end of the rough polishing step, the ends of the substrate with the polishing resistor are at levels within 5 μm with respect to the final throat height. Each resistor from 10 μm to final throat height
A 14b resistor is used to monitor the level error. The detected level error is used to balance the polishing forces at both ends of the substrate. The final polishing distance from 10 μm to the final throat height is obtained by monitoring the position of the polished tip using resistance measurements of two polishing guide resistors 14.

A conventional electrical polishing guide resistor has a non-linear response curve as shown by the solid curve in FIG. This curve is approximately proportional to

Rx = Rs · L / (X + H) + Rc where Rx is the measured resistance between the two conductors 16 and 17, Rs is the sheet resistance of the chrome resistor 14b, and Rc is the conductor 16 and 17 Is the contact and conductor resistance of the connection to L, L is the effective length of the chromium resistor 14b, and X is the tip of the resistor 14b.
The polishing distance or width from 14a to the final throat height, and H is the final width of the polishing resistor at the final throat height.

The conventional electrical polishing guide resistor has a resistance to polishing distance characteristic of 10
Limits usable response to fine polishing distances of μm. As is apparent from FIG. 6, when rough polishing the substrate, the response curve A for the first 6 μm polish is too steep to produce an ideal polish measurement. At the lower end of the response curve, the change in resistance becomes slower as the polishing distance increases, making the signal-to-noise ratio unsatisfactory. As the polishing distance approaches zero, the change in resistance becomes very large with the slight removal of material during polishing. Therefore, the dynamic range of the abrasive guide resistor is limited to approximately the bend of curve A. This is because in this range, increasing the polished distance gives a moderate change in the resistance Rx. The dashed curve B in FIG. 6 shows the resistance Rx obtained according to the invention at the polished distance.

The resistor structure of FIG. 1 is used to make the resistance of the electrically polished guide resistor linear. This resistor consists of a layer of chrome 20 as one strap. This resistor has a trailing end 20c parallel to the final throat height 15. The side edges 20a, 20b of the resistor 20 converge towards the surface 11a at an angle Z with respect to the polished surface 11a. The final length Lf of the resistor at throat height is about 480 μm. Its initial length Ls is 20 μm. The resistor of FIG. 1 provides an effective increase in the length of resistor 20 as polishing progresses,
Therefore, the resistance versus polishing distance is linear, as shown by curve B in FIG. To make the resistance-to-polishing distance more linear, as shown in FIG. 2, the slope of the resistor ends 20a20b and conductors 16 and 17 during the initial stage of polishing should be slightly less than that of the rest. The resistors and the conductors may be inclined so as to be large. Furthermore, it has been found that an increase in the spacing between the conductors 16, 17 can provide improved resolution in rough polishing. The x and y coordinates in microns for each end shown in FIG. 2 are shown in the table below.

The X coordinate is the distance from the center line to the conductor 17. The Y coordinate is the width of the resistor 20.

To achieve a broader range of polishing that covers both rough and final polishing, the embodiment of Figure 3 is shown. An extension 22 has been added to the resistor 20 of FIG. The extension 22 comprises a rough abrasion resistant portion K having a base portion in contact with the tip of the fine abrasion resistant portion L. 10 μm
Its extension 22, starting with a fine polishing dimension W equal to, extends by a distance W ₁ of 70 μm to the rough polishing starting edge along the two converging ends 23, 24. The resistance change during rough polishing is about 4 to 15 ohms. The fine polishing resistance change is from about 25 ohms to 275 ohms for a resolution of about 25 ohms / μm. Compared to the conventional abrasive resistor of Figure 1 for a 50: 1 resistor to conductor resistance ratio,
The performance of the embodiment of FIG. 3 is shown in FIG. The improvement in resolution during coarse polishing, noise reduction and linearity during fine polishing is apparent from curve c in that figure. A conventional abrasive resistor exhibits the characteristics a and b in FIG. In curve c,
The resistance changes loosely but clearly during the rough polishing, ie at the polishing distance W ₁ . After that, the resistance increases greatly at the polishing distance w which is the width of the resistor 20. The resistance Rx directly represents the polishing distance W, and thus the final throat height, so that better control is obtained for the finely ground portion.

F. Effect Therefore, by effectively shaping the ends of the polishing resistor, the effective change in polishing distance versus resistance can be controlled.
Tilting the ends of the resistor causes a more direct resistance change, providing greater noise reduction than conventional polish control mechanisms.

[Brief description of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention having a shape which effectively makes resistance change versus polishing distance linear, and FIG. 2 is a book which makes resistance change versus polishing distance more linear. FIG. 3 is a diagram showing another embodiment of the invention, FIG. 3 is a diagram showing yet another embodiment of the present invention for performing rough polishing distance measurement as well as fine polishing distance measurement, and FIG. 4 is an implementation of FIG. FIG. 5 shows resistance vs. polishing distance characteristics for an example, FIG. 5 shows a conventional electrical polishing guide resistor on one side of an array of thin film transducers, and FIG. 6 shows a conventional and inventive polishing guide resistor. It is a figure which shows the characteristic of resistance-to-polishing distance.

Claims (2)

[Claims] 1. A planar polishing guide resistor formed on the surface of the substrate so as to give a linear resistance change in response to a change in the position of the polishing edge of the substrate to be polished, wherein the resistor is a resistor. A first and a second conductor attached to the base surface so as to define a first edge and a second edge of the base material, and an entire area of the base surface sandwiched by the first and second conductors. The first conductor and the second conductor are separated from each other by a predetermined distance at the initial polishing edge position of the base body, and the first conductor and the second conductor are moved further from the initial polishing edge. Second
The conductor extends to the back at an angle with respect to a vertical line with respect to the polishing edge so that the distance between the conductors increases, and terminates at a predetermined distance from the polishing edge. A conductor, the second conductor, the initial polishing position, and an area defined by the conductor end portion are attached to the surface of the base body in contact with the first conductor and the second conductor. , Polishing guide resistor. 2. A planar polishing guide resistor formed on the surface of the substrate so as to give a linear resistance change in response to a change in the position of the polishing edge of the substrate to be polished. A first and a second conductor attached to the base surface so as to define a first edge and a second edge of the base material, and an entire area of the base surface sandwiched by the first and second conductors. The first conductor and the second conductor are separated from each other by a predetermined distance at the position of the initial polishing end of the base body, and are separated from the initial polishing end over most of the length thereof. To the polishing edge so as to increase the distance between the first conductor and the second conductor, and extends backward at an angle with respect to a vertical line to the polishing edge, and the initial polishing is performed over the remaining length. It extends perpendicular to the edge and then terminates, and the low resistance material is A conductor, the second conductor, the initial polishing position, and an area defined by the conductor end portion are attached to the surface of the base body in contact with the first conductor and the second conductor. , Polishing guide resistor.