JP5637453B2 - Magnetic sensor, magnetic encoder, and method of manufacturing magnetic sensor - Google Patents

Description

  The present invention relates to a magnetic encoder capable of detecting the magnetism emitted from a magnetic medium by a magnetic sensor and obtaining the displacement or speed of a movable member.

  Many mechanical devices perform feedback control by accurately detecting the displacement and speed of a movable member. One example is a lens barrel for an autofocus camera. In the lens barrel, a focus mechanism is provided for moving the focusing lens back and forth with an electric motor or an ultrasonic motor. In order to detect the rotational displacement of the rotating cylinder constituting the focus mechanism, a magnetic encoder is used in order to detect the movement amount of the magnetic medium (that is, the advance / retreat amount of the focusing lens group) with high accuracy.

  In order to detect displacement with high accuracy, the magnetic encoder is required to have high resolution. The resolution can also be expressed by the magnetization pitch of the magnetic medium, and the magnetization pitch is conventionally 30 to 50 μm, but 10 to 20 μm and further 10 μm or less have been demanded. As the resolution increases, the influence of the gap, which is the distance between the magnetic medium and the detection element, increases, and it is necessary to eliminate the gap fluctuation. For this reason, a method in which the magnetic medium and the detection element are brought into contact with each other and slid is advantageous, and is often employed.

  In this application, in order to make it easy to understand the positional relationship between the magnetic sensor and the magnetic medium, the direction in which the magnetic medium and the magnetic sensor reciprocate relatively is the X axis, and the center of curvature of the magnetic medium is the direction perpendicular to the X axis. The direction intersecting with the Z axis is defined as the Z axis, and the other as the Y axis. When the magnetic medium is a curved surface, the X axis is the tangential direction of the magnetic medium at the point in contact with the magnetic sensor. In addition, when the point at which the force that presses the magnetic sensor against the magnetic medium (pressurization point) is located on the Z-axis, the origin of the X-axis is used, and the position shift in the X direction from the X-axis origin (that is, the pressurization point) Is defined as an X offset. Furthermore, in order to make it easy to understand the relative orientation between the sliding surface of the magnetic sensor and the magnetic medium, the angle at which the sliding surface rotates about the X axis as the rotation axis is the pitch angle, and the angle at which the sliding surface rotates about the Y axis is the roll. When the sliding surface is parallel to the X axis, the roll angle is defined as 0 degree, and when the sliding surface is parallel to the Y axis, the pitch angle is defined as 0 degree.

  Patent Document 1 discloses a method for reducing gap variation due to the X offset and roll angle of a detection element. A detection element having a very narrow width of 0.04 to 0.3 mm, which is 2 to 15 times the magnetization pitch, is proposed. By reducing the sliding direction width of the detection element in contact with the magnetic medium to 0.3 mm or less, gap variation due to X offset and roll angle variation is reduced, and signal output amplitude is stabilized.

Japanese Patent Laid-Open No. 2006-64381 JP 2006-187839 A JP 2006-234542 A

  By reducing the width in the sliding direction to 0.3 mm or less as in Patent Document 1, even if there is a variation in X offset or roll angle, gap variation can be suppressed. A problem has occurred. Since the width w in the sliding direction is small, the ridges at both ends in the sliding direction of the detection element are likely to come into contact with the magnetic medium, and therefore it is necessary to chamfer the ridges. A conventional detection element is obtained by forming an element on a wafer and then cutting the wafer with a grindstone. However, in order to form a chamfered surface on the ridge, it is necessary to carry out after making individual substrates having detection elements alone, and it is difficult to reduce the manufacturing cost.

  Patent Document 2 discloses a method of polishing sensor chips arranged in a row with a wire. However, the chamfered surface tends to be concave reflecting the cross-sectional shape of the wire, and there is a possibility that an edge may remain even after polishing, and it is difficult to obtain high slidability when sliding with a magnetic medium. For example, as shown in the sensor substrate 310 of FIG. 9, after forming the GMR sensor 302 on the Si substrate 301 and covering the coating 303, the corners of the Si substrate are chamfered with a grinding wire so that the cross section is concave. A chamfered surface 307 may be formed.

  In Patent Document 3, dummy chips are arranged on both sides of the sensor chip, but the edge of the sensor chip itself remains exposed on the medium facing surface. There is a possibility that the edge contacts the curved surface of the magnetic medium constituting a part of the cylindrical surface. Since two parts of the same size as the sensor chip are added, the assembly process becomes complicated and it is difficult to reduce the manufacturing cost.

  An object of the present invention is to provide a magnetic sensor having excellent industrial mass productivity and high slidability, a magnetic encoder using the magnetic sensor, and a method of manufacturing the magnetic sensor.

The magnetic sensor of the present invention is connected to the sensor board that slides on a magnetic medium, a wiring board on which the sensor board is provided, a sensor holding plate that supports the sensor board via the wiring board, and the wiring board. With a flexible cable,
The sensor substrate is rounded on the edge of the detection surface that slides with the magnetic medium,
The R chamfered surface is a convex curved surface facing the magnetic medium, and has a surface roughness Ra <1 nm.

  The R chamfered surface is preferably a surface formed by dry etching.

  The sensor substrate (sensor chip) preferably has a detection element utilizing a giant magnetoresistive effect. The width w of the sensor substrate is preferably 0.6 mm or more. w is a width dimension in the X direction in which the medium slides, and corresponds to a dimension in the direction along AA ′ in FIG. The detection surface between the pair of R chamfered surfaces is configured such that a portion serving as a sliding surface is continuously formed of at least one of a flat surface and a convex curved surface, and does not include an edge or a concave surface. The surface of the film covering the detection element corresponds to the detection surface.

  The magnetic encoder according to the present invention is characterized by detecting rotational displacement of a camera lens barrel using the magnetic sensor and a magnetic medium.

The method for manufacturing a magnetic sensor of the present invention includes a step of coating a detection element constituting a magnetic sensor formed on a Si wafer with a photoresist,
Heating the photoresist to form a resist pattern having a convex curved surface at the ridge;
Dry etching the resist pattern and the Si wafer, and transferring at least a part of the shape of the convex curved surface to the Si wafer;
Cutting the Si wafer to obtain a rectangular sensor substrate having at least a part of the convex curved surface at the ridge and the convex curved surface having surface roughness Ra <1 nm.

The method of manufacturing a magnetic sensor of the present invention includes a step of forming a detection element using a giant magnetoresistance effect on a Si wafer,
Coating the detection element with a rectangular photoresist;
Heating the rectangular photoresist to round the corners of the ridgeline to obtain a resist pattern having a convex curved ridge;
The step of transferring the shape of the ridges of the convex curved surface to the rest of the resist pattern and the Si wafer by dry etching the resist pattern and the Si wafer;
Removing the remainder of the resist pattern;
Cutting the Si wafer so as to leave at least a part of the ridge of the convex curved surface transferred to the Si wafer, and obtaining a rectangular sensor substrate having a chamfered surface roughness Ra <1 nm on the ridge It is characterized by providing.

  The magnetic encoder of the present invention preferably has a pressing load of 50 mN or more and 800 mN or less against the magnetic medium in a direction perpendicular to the sensor holding plate.

  If it is less than 50 mN, that is, less than 5 gf, the pressing load force of the detection element against the magnetic medium is too small, so that the detection surface moves away from the magnetic medium surface during sliding, and the output voltage fluctuates. This occurs due to slight undulations on the surface of the magnetic medium, jumping at the convex portion, separation due to external force, and the like. If it exceeds 800 mN, that is, 82 gf, it is possible to push the detector element off and to release it by an external force, but a problem of wear resistance occurs. In a magnetic medium coated with a magnetic material on a plastic film, when the load increases, the surface of the magnetic medium is deformed and the width of the detection element is small. The phenomenon of shaving occurs and the wear resistance deteriorates rapidly.

The load value at which the surface of the magnetic medium is deformed can be obtained as follows. A transparent glass plate is pressed against the surface of a magnetic medium having a curvature radius of 25 mm, and a load at which the contact width between the transparent glass and the magnetic medium becomes 0.5 mm is obtained. When observed from the back side of the transparent glass, the difference between the area where the magnetic medium is in close contact with the surface of the transparent glass and the area where the magnetic medium is not in close contact can be clearly distinguished visually from the back side of the transparent glass. . Therefore, the width of the close contact area is defined as the contact width. The contact width was 0.5 mm and the surface of the magnetic medium was deformed. The width direction of the magnetic medium was 3 mm. The surface of the magnetic medium has an average surface roughness Ra of about 1 μm. The plastic film of the magnetic medium is a PET film having a thickness of 200 μm, and the magnetic material is a strontium ferrite powder having an average particle diameter of 1 μm to 10 μm applied to a thickness of 30 μm. The pressing load at which the deformation starts is 1136 mN (116 gf), and the load per unit that causes the magnetic medium to deform from the contact area is 757 mN / mm ² . Considering the safety factor, the pushing load is set to 800 mN (82 gf) or less, and preferably about 530 mN / mm ² or less. By setting the load value per unit to 530 mN / mm ² or less, the deformation of the magnetic medium surface by the sensor substrate does not occur. In other words, when the longitudinal dimension of the sensor substrate is fixed and the load value per unit area is 530 mN / mm ² , the width of the sensor substrate in the sliding direction needs to be 0.5 mm or more.

  The substantially central portion of the sensor holding portion becomes a load point that applies a pressing load to the magnetic medium. When the detection element is arranged at this load point, the difference in output of the detection element depending on the moving direction can be minimized with respect to the reciprocal movement relative to the magnetic medium.

  According to the present invention, it is possible to provide a magnetic sensor having excellent industrial mass productivity and high slidability, a magnetic encoder using the same, and a method for manufacturing the magnetic sensor.

It is the schematic explaining the manufacturing process of a sensor board | substrate. It is a top view of the sensor substrate of an example. FIG. 3 is an A-A ′ cross-sectional view of the sensor substrate of FIG. 2. FIG. 3 is a perspective view of a wiring board provided with the sensor board of FIG. 2. It is the schematic of the magnetic encoder of an Example. It is a side view of the magnetic encoder of FIG. It is sectional drawing of the sensor substrate of a reference example. It is sectional drawing explaining an outline about the position shift of a sensor board | substrate. It is sectional drawing of the sensor substrate of a comparative example.

  Hereinafter, embodiments will be described in detail with reference to the drawings. The present invention is not necessarily limited to these. For ease of understanding, the same reference numerals are used for the same parts or parts. In order to indicate the left or right side of the paired portions, alphabets such as a or b are added after the reference numerals. For example, if the code is 50, 50a and 50b correspond.

Example 1
FIG. 1 is a schematic diagram for explaining a manufacturing process of a sensor substrate.
First, a silicon oxide film is formed on one surface of a 6-inch diameter silicon wafer 1 by thermal oxidation, and a patterned silicon oxide film (not shown) is formed only at a position where a GMR element as a detection element is to be formed. ) Was left. Subsequently, a plurality (thousands) of GMR sensors 2 including wirings and GMR elements were formed by using a photolithographic technique, a vacuum film forming technique, and an etching technique. The GMR sensor was covered with a coating 3 which was an oxide protective film except for electrode terminals.

  (Step S1) Next, a photoresist film was applied on the silicon wafer so as to cover the GMR sensor 2 having the coating 3 and prebaked. After exposure through a photomask using an i-line stepper, development was performed for several minutes to form a rectangular photoresist 4 film. The cross section of the sensor substrate formed by the process of FIG. 1 schematically corresponds to the AA ′ cross section of FIG.

  (Step S2) Next, the film of the photoresist 4 was heated and baked at a temperature of 120 ° C. for 150 seconds (so-called reflow was performed). At this time, the fluidity of the photoresist increased due to the effect of heating, and the rectangular ridges were rounded due to surface tension. When the heating was completed, the resist pattern 5 was obtained by solidifying while maintaining the roundness of the ridges.

(Step S3) Next, using an ICP (inductively coupled plasma) dry etching apparatus, dry etching is performed with plasma 6 on the exposed surface of the resist pattern 5 and the silicon wafer 1 while using CF ₄ gas at a flow rate of 50 sccm and oxygen gas 10 sccm. Went. Since the silicon oxide film was not present in the portion not covered with the resist pattern 5, the etching progressed and a groove was formed in the silicon wafer. When the inner wall surface of the groove has a predetermined R shape 7 ′, the etching is finished. The resist pattern was only etched in a range where the GMR sensor 2 was not exposed.

(Step S4) Next, the remaining resist pattern was removed with a solvent.
(Step S5) Next, in the groove portion 1a formed by etching, the silicon wafer was cut with a dicer to cut the rectangular base portion 1b. As a result, the base side became a sensor substrate in which the ridgeline was chamfered by dry etching. Since this separation also separates adjacent GMR sensors 2, a plurality of sensor substrates including one GMR sensor 2 were obtained. In addition, illustration of process S5 was abbreviate | omitted in FIG.

  In order to accurately transfer the R surface shape of the ridge of the resist pattern 5 to the R shape of the groove portion, a photoresist having a dry etching rate equivalent to that of a silicon wafer is used. A composite wafer (for example, an AlTiC substrate for a thin film magnetic head) in which different phases or grain structures are combined has a different dry etching rate for each phase or grain structure. Therefore, it is not preferable to apply the present invention.

  FIG. 2 is a top view of the sensor substrate 10 manufactured using the manufacturing process of FIG. An R chamfered portion 7 is formed between the surface of the sensor substrate 10 facing the medium and the side surface obtained by cutting. The GMR sensor 2 forms a bridge circuit with a plurality of GMR elements 2a, and is connected to the electrode pad 2c through the wiring film 2b. Each GMR element 2a is specifically composed of a laminated film that becomes a spin valve type giant magnetoresistive effect element. The width of the sensor substrate was 0.5 mm and the length of the sensor substrate was 3.0 mm. The width w is a dimension in the A-A ′ direction, that is, the sliding direction. In FIG. 2, the length is the longitudinal dimension of the sensor substrate and is orthogonal to w.

3 is a cross-sectional view taken along the line AA ′ of the sensor substrate 10 of FIG. The details of the GMR sensor 2 are shown in a simplified manner. R chamfers are formed on the ridges on both sides of the surface on which the GMR sensor 2 is formed on the silicon substrate 1c. The end of the SiO ₂ coating 3 was formed to have a smooth taper. The coating thickness in the flat region was about 2 μm. Even if the GMR element and the wiring are included, the thickness is several μm, and the thickness of the sensor substrate can be regarded as the thickness of the wafer. The SiO ₂ film on the GMR element forms a magnetic gap with the surface of the magnetic sheet 60. The detection surface between the R chamfered surfaces is composed of a flat surface and a smooth convex curved surface.

  FIG. 4 is a perspective view of the sensor substrate 10 of FIG. 2 and the wiring substrate 20 provided with the same. The wiring board 20 is a glass epoxy board in which a wiring circuit is formed, and the electrode pad 2 c of the sensor board and the wiring pad 21 of the wiring board are electrically connected via the bonding wire 23. The wiring pads 21 and the wiring terminals 22 are paired and are electrically connected within the wiring board. It is difficult to directly connect an FPC (Flexible Print Circuit) to the electrode pad 2c due to the difference in size. Therefore, a wiring board was provided. An FPC is connected to the wiring terminal via lead-free solder.

  FIG. 5 shows a schematic diagram of the magnetic encoder of the embodiment. The arrangement of the magnetic sheet 60, which is a magnetic medium, the sensor substrate 10 having the GMR element 2a, the glass epoxy wiring substrate 20, the sensor holding plate 30, and the mounting base 50 as viewed from the magnetic medium side is shown. For easy understanding, the see-through magnetic sheet 60 is indicated by a dotted line, and the mounting base 50 hidden behind the sensor holding plate 30 is indicated by a chain line. The mounting base corresponds to a part of the camera lens barrel.

  In FIG. 5, the sensor holding plate 30 is fixed to the mounting bases 50 a and 50 b with screws using holes 39 a and 39 b formed in the fixing portion 37. By fixing the sensor holding plate 30 to the mounting base, the sensor substrate 10 is pressed against the magnetic sheet 60 at a predetermined position with a predetermined load. The sensor holding plate 30 is configured by a plate spring made of an integral metal thin plate. Specifically, the sensor holding plate 31 that holds the glass epoxy wiring board 20, two elastic arm portions, and one fixed portion. 37 is provided.

  The sensor holding plate made of an integral leaf spring is made thinner compared to the case where the elastic arm portion is manufactured and assembled with another member having high rigidity or when the pivot is used together with the sensor holding plate. In addition, the sensor holding plate made of an integral leaf spring reduces the posture angle variation of the sensor substrate, contributing to a reduction in the number of parts and an assembly cost. When this sensor holding plate is used for a magnetic encoder, it is used in a flat state. In order to enhance the spring property, bending in advance and making it a three-dimensional structure in the Z direction (thickness direction) not only increases the processing cost, but also due to unexpected deformation due to the assembly process of the magnetic encoder This is not preferable because the spring load varies and the posture angle also varies.

  The elastic arm portion includes an elastic deformation portion 32 and a support portion 33. When the dimension auxiliary line L4 (the auxiliary line on the lower side in FIG. 5) is virtually extended, the line corresponds to the boundary between the support part 33 and the fixing part 37. The elastic deformation portion extends in a direction along M2, and has a zigzag shape that meanders in a direction along L2. The rotation axes in the pitch direction are indicated by alternate long and short dash lines. Elastic deformation portions 32 a and 32 b are connected to both sides of the sensor holding portion 31 so that the one-dot chain line serves as a rotation axis in the pitch direction of the sensor holding portion 31. The other end of each elastically deformable portion 32 is supported by a support portion 33 that functions as a cantilever, and the support portion is connected to be joined to a fixed portion 37.

  The elastic deformation portion 32 becomes a portion that generates a spring load when the sensor substrate 10 is pressed against the magnetic sheet 60, and stabilizes the sliding of the magnetic sheet 60 and the sensor substrate 10. Moreover, since the elastic deformation part 32 can make pitch rigidity small, it can suppress the breadth of an air gap with respect to pitch angle fluctuation | variation.

  The center of the GMR element 2a in the sensor substrate 10 (the intersection of the center line of the one-dot chain line and the two-dot chain line) is more magnetic than the rotational axis (the one-dot chain line parallel to the Y axis) in the pitch direction of the elastic deformation portion 32. On the edge 60a side. By adopting this positional relationship, it is possible to suppress the influence of pitch angle fluctuations in the GMR element 2a, and to suppress the deformation of the support portion 33 when the sensor substrate is pressed against the magnetic sheet. .

  The ends of the pair of support portions 33 a and 33 b are connected to the fixed portion 37. And the support part 33 is comprised by the cross part 34 which supports an elastic deformation part, and the wide part 35 and the wide part 36 which exist between the cross part 34 and a fixing | fixed part. In the intersecting portion 34, slits are provided in the X-axis direction on both sides of the portion connected to the elastic deformation portion 32. In the region where the slit 33s is formed, the width M1 of the intersecting portion is smaller than the width M2 in the remaining portion of the intersecting portion. Providing the slits 33 s prevents stress from being concentrated at the connecting portion between the elastically deforming portion and the intersecting portion even when an external force such as an impact is applied. Since most of the intersecting portions are widened to be M2, the rigidity is enhanced as compared with the configuration in which the support portion is extended by a thin arm having a uniform width. In the wide width portion 36, the width M3 is widened toward the inside (center line side) to the extent that the wiring substrate 20 can be avoided in order to secure a space 36s when the wiring substrate 20 is inclined by an external force such as an impact. To increase the rigidity. In the wide portion 36, the width is further expanded to (M3 + M4) toward the outside and the space between the fixed portion 37 is filled, thereby contributing to improvement in rigidity. The smaller hole 38 provided in the wide portion 36 is used for temporarily fixing the sensor holding plate, and is not a hole for securely fixing.

  In this way, by widening the support portion toward the base, the rigidity is increased, and the sensor substrate 10 is prevented from being inclined in the roll direction. Due to this rigidity improvement, even if it is used in the state of a flat plate spring, it can be used thin and pivotless. A one-dot chain line parallel to the Y-axis direction corresponds to a center line connecting the center of the sensor holding unit 31 and the center of the fixed unit 37. The elastic arm portions were formed symmetrically with respect to the center line.

  In FIG. 5, an electrode pad is provided in the vicinity of the lower end of the sensor substrate 10 and is electrically connected to the wiring substrate 20 via wire wiring, and the wiring terminal of the wiring substrate 20 is electrically connected to the FPC 40 via lead-free solder. (Lead-free solder is hidden in the FPC and is not shown in FIG. 5). The FPC 40 is supported by the resin 51 at the lower end of the fixed portion 37. The electrical signal from the GMR element 2a is taken out through the wiring board 20 and the FPC 40. The FPC (flexible cable) is narrow between the wiring board 20 and the resin 51. This narrowing does not hinder the operation of the sensor holding plate in the pitch direction. If an FPC having a large width is used, the rigidity of the FPC becomes dominant, and it is not preferable because the elastic deformation portion tends to be prevented from acting so that the sensor holding plate faces the magnetic sheet in parallel.

  L0 is the distance between the rotational axis in the pitch direction of the elastic deformation portion and the center of the GMR element, and corresponds to the distance between the one-dot chain line and the two-dot chain line along the X direction. L1 corresponds to the distance from the rotation axis in the pitch direction of the elastic deformation portion to the edge 60a of the magnetic sheet (the edge on the side close to the fixed portion). L2 corresponds to the dimension from the rotation axis in the pitch direction of the elastic deformation portion (one-dot chain line in the direction along the X axis) to the root of the intersecting portion 34 (boundary with the wide width portion 35). L3 corresponds to the dimension from the rotation axis in the pitch direction of the elastic deformation portion to the root of the thick portion 35 (boundary with the wide portion 36). L4 corresponds to the dimension from the rotation axis in the pitch direction of the elastic deformation portion to the root of the wide portion 36 (boundary with the fixed portion 37).

  FIG. 6 is a side view when viewed from the magnetic medium side from the left to the right in FIG. 5 (negative direction of the Y axis). In this state, the sensor substrate 10 is pressed against the magnetic sheet 60 and the elastic deformation portion is bent. When the magnetic sheet 60 is provided in a lens barrel for a camera, the displacement in the illustrated rotation direction can be detected by a magnetic sensor.

  The magnetic sheet 60 according to FIG. 5 was prepared by fixing a tape-like plastic film coated with a magnetic material to a nonmagnetic surface having a predetermined curvature with an adhesive. The width Wb of the magnetic sheet was 3 mm, and the radius of curvature of the magnetic sheet surface was 27.5 mm.

(Reference Example 1)
FIG. 7A is a cross-sectional view of the sensor substrate 110 of Reference Example 1. FIG. A GMR sensor 102 and a coating 103 covering the GMR sensor 102 were formed on the Si substrate 101c. The difference from the embodiment of FIG. 3 is that the chamfered portion 107a of the slope is formed at the ridge of the Si substrate 101c, so that the corner becomes the edge 107b. The taper of the chamfered portion 107a was formed by wet etching. Specifically, a portion other than the ridge portion where the tapered surface is desired to be formed was masked with a resist, and the ridge of the Si substrate was anisotropically etched with a KOH solution to form a tapered surface. When the sensor substrate 110 is replaced with the sensor substrate 10 of FIG. 6 and the magnetic sheet 60 is reciprocated, the angle of the tapered surface of the sensor substrate 110 forms an edge, and the magnetic sheet is scraped off. There has occurred.

(Reference Example 2)
FIG. 7B is a cross-sectional view of the sensor substrate 210 of Reference Example 2. A GMR sensor 202 and a coating 203 covering the GMR sensor 202 were formed on the Si substrate 201c. A difference from the embodiment of FIG. 3 is that an R chamfered blend processing portion 207 is formed on the edge of the Si substrate 201c. The blending portion 207 was formed by reciprocating while wrapping the wrapping tape (# 10000) against the ridge of the Si substrate. Two chamfering conditions in Reference Example 2 were examined. For each condition, the sensor substrate 110 was replaced with the sensor substrate 10 of FIG. 6, and the magnetic sheet 60 was reciprocated. The results are shown in Table 1. 3 and no. 4 shows.

  FIG. 8 is a cross-sectional view for explaining the outline of the positional deviation of the sensor substrate. FIG. 8A shows a state in which the magnetic sheet 60 attached and fixed to a part of the lens barrel 61 for the camera and the sensor substrate 110 slide. FIG. 8B shows how the sensor substrate is displaced to the position indicated by reference numeral 110 ′ when an external force such as an impact is applied to the camera. In such a case, the sensor substrate tries to return to the original position, but if there is an edge on the edge of the sensor substrate, the magnetic sheet may be damaged. Accordingly, as shown in FIG. 7A, Reference Example 1 and FIG. 8C, it was examined to form a tapered surface by dropping the corners of the sensor substrate 110. a represents the width of the tapered surface (dimension in the direction parallel to the medium facing surface of the sensor substrate), and b represents the depth of the tapered surface (dimension in the thickness direction of the sensor substrate). As shown in FIG. 8D, it was expected that the taper surface was in contact with the surface of the magnetic sheet 60 to avoid damage. As shown in Fig. 2, good results could not be obtained. In addition, although the chamfered surface of the concave curved surface by wire grinding | polishing was examined instead of the flat taper surface, there was no change in forming an edge and the result of the evaluation item was the same.

  Table 1 shows the results of comparing the slidability and the like for the examples and the reference examples. The width and depth at the chamfered portion are the same as a and b in the description of FIG. No. in Table 1 1 is Example 1 and Ra is an AFM (Atomic Force Microscope), and is 10 μm × 10 μm square arbitrarily selected from the chamfered surfaces as viewed from the direction perpendicular to the medium facing surface of the sensor substrate. The area was scanned and measured. When 10 samples obtained from the same wafer were measured, the average value of Ra was 0.6 nm, and the evaluation items also had good results. Low cost, high quality, high productivity and high slidability were obtained. The R chamfered surface of the sensor substrate of Example 1 subjected to vapor phase etching had an Ra of less than 1 nm, but the problem of sticking to the magnetic sheet 60 (sticking) did not occur.

  Among the evaluation items in Table 1 tested in the configuration of FIG. 7A, the slidability ○ was satisfactory even after 20,000 reciprocations, but the slidability x was chattered during the first reciprocation, Did not endure use. Chatter ○ indicates that chatter did not occur, and chatter × indicates that the sensor substrate could not be properly slid due to catching and vibration. Cost ○ indicates that a lot of chamfering can be applied to the wafer at one time in order to add a dry etching (vapor phase etching) process in the middle of the wafer process. Yes. The cost x indicates that both the taper processing and the blending processing cannot be collectively chamfered in wafer units, and the processing cost has increased. No. In the blending process No. 4, a good result was obtained in terms of sliding performance by increasing the depth, but fine dust (particles) is generated by machining. Since the cleaning for removing the particles is involved, the man-hours and costs for the processing further increase.

  The present invention can be applied as a magnetic encoder capable of detecting the magnetism emitted from the magnetic medium with a magnetic sensor and determining the displacement or speed of the movable member.

1: Silicon wafer,
1a: groove,
1b: base,
1c: silicon substrate,
2: GMR sensor,
2a: GMR element,
2b: wiring film,
2c: electrode pad,
3: coating,
4: Photoresist
5: resist pattern,
6: Plasma,
7: R chamfer,
7 ': R shape,
10: sensor substrate,
11: Surface facing the medium
20: wiring board,
30: sensor holding plate,
30 ': sensor holding plate,
30 ″: sensor holding plate,
31: Sensor holding part,
32a, 32b: elastic deformation part,
32e, 32f: elastic deformation part,
32d: elastic deformation part,
33a, 33b: support part,
33s: slit,
34a, 34b: intersection,
35a, 35b: thick part,
36a, 36b: wide part,
36s: space,
37: fixed part,
38: hole,
39a, 39b: holes,
40: FPC,
41: resin,
50a, 50b: mounting base,
60: Magnetic sheet,
60a: edge of magnetic sheet,
61: barrel,
101c: Si substrate,
102: GMR sensor,
103: coating,
107a: chamfered portion,
107b: edge,
110: sensor substrate,
130: sensor holding plate,
133a, 133b: support part,
133s: slit 201c: Si substrate,
202: GMR sensor,
203: coating,
207: Blend processing section,
210: Sensor substrate

Claims (6)

A sensor board that slides on a magnetic medium; a wiring board on which the sensor board is provided; a sensor holding plate that supports the sensor board via the wiring board; and a flexible cable connected to the wiring board.
The sensor substrate is made of a Si wafer and is slid with a magnetic medium while applying a pressing load . R chamfering formed by dry etching is applied to the ridges on both sides in the sliding direction of the detection surface of the sensor substrate. Has been
The R-chamfered surface is a convex curved surface having no edge facing the magnetic medium, having a width larger than the depth at the chamfered portion , and has a surface roughness of Ra <1 nm. . 2. The magnetic sensor according to claim 1, wherein the convex curved surface has a chamfered portion having a depth of 3 to 6 μm and a width of 20 to 50 μm .   The magnetic sensor according to claim 1, wherein the sensor substrate includes a detection element using a giant magnetoresistance effect.   A magnetic encoder using the magnetic sensor according to claim 1 and a magnetic medium to detect rotational displacement of a camera lens barrel. Coating a detection element constituting a magnetic sensor formed on a Si wafer with a photoresist having an etching rate equivalent to that of the Si wafer;
Heating the photoresist to form a resist pattern having convex curved surfaces on both edges;
Both the resist pattern and the Si wafer are dry-etched using an etching gas containing oxygen gas, and at least a part of the shape of the convex curved surface is transferred to the ridges on both sides of the Si wafer;
Cutting the Si wafer to give an R chamfer having at least a part of the convex curved surface as a ridge, and the R chamfered surface is a convex curved surface without an edge having a width larger than a depth at a chamfered portion; and And a step of obtaining a rectangular sensor substrate having a surface roughness of Ra <1 nm. Forming a sensing element using a giant magnetoresistive effect on a Si wafer;
Coating the detection element with a rectangular photoresist having an etching rate equivalent to that of the Si wafer;
Heating the rectangular photoresist to round the corners of the ridge lines on both sides to obtain a resist pattern having convex curved ridges;
Transferring the shape of the ridges of the convex curved surface to the rest of the resist pattern and both sides of the Si wafer by dry-etching the resist pattern and the Si wafer together using an etching gas containing oxygen gas ; and
Removing the remainder of the resist pattern;
The Si wafer was cut to leave at least a part of the convex curved ridge transferred to the Si wafer, and the R edge was chamfered, and the R chamfered surface was made wider than the depth at the chamfered portion. And a step of obtaining a rectangular sensor substrate having a convex curved surface having no edge and a surface roughness of Ra <1 nm.

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