JP2503071B2 - Method for manufacturing core for magnetic head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic head core, and particularly for a magnetic head in which the width accuracy of a convex portion such as a track provided on a sliding surface with a recording medium is improved. The present invention relates to a core manufacturing method.

(Background Art) In recent years, magnetic tapes used in video tape recorders (VTRs), floppy disk drives (FDDs), fixed magnetic disk drives (RDDs), etc. have improved magnetic recording density. The requirements for the flying height and magnetic characteristics of the magnetic core have become strict, and the track formed on the sliding surface of the magnetic head core with the recording medium is required to have high width accuracy.
In D, it is required to provide a track having a track width with a dimensional accuracy of ± 1 μm or less. Similar to this track, similar dimensional accuracy is required even for a pair of air bearing surfaces that are formed to project at a predetermined height on the sliding surface of the magnetic head core with respect to the recording medium.

By the way, when manufacturing such a core for a magnetic head, generally, in order to manufacture a large number of cores,
A long so-called gap bar having an annular magnetic path, which has a coil winding hole and a magnetic gap of a predetermined gap, is used, and the gap bar is used as a sliding surface for a recording medium. Thus, protrusions such as a track having a predetermined width and height, an air bearing surface, etc. are formed so as to correspond to the number of manufacturable cores.

And, in the past, machining was adopted for the formation of the convex portion, but problems such as chipping and cracks were caused during the machining, and a machining error was large, and dimensional accuracy could not be sufficiently improved. From, for example, JP-A-62-40
Japanese Patent Laid-Open No. SHO 56-22217 discloses a technique for improving the track width accuracy by combining machining with finishing by ion etching.
Auxiliary grooving processing (preprocessing) by laser processing is applied,
After that, a method for improving the processing accuracy of the track width by finishing with ion etching processing has been clarified.

However, in the ion etching process adopted in these conventional methods, the etching rate is slow, and the ratio of the etching rates of the core material (gap bar) and the mask material cannot be made large. Since the depth cannot be increased, a magnetic gap remains on both sides of the track, forming a pseudo track, which causes a problem of noise. Of course, according to the laser processing, although such a pseudo track can be removed, thermal processing causes thermal damage to the track, and cracks due to thermal stress occur to deteriorate magnetic characteristics. The problem is inherent.

On the other hand, a method of manufacturing a core for a magnetic head by photolithography and an etching process is disclosed in JP-A-62-234214.
It is disclosed in Japanese Patent Publication No. According to this method, a predetermined mask pattern is applied to the surface of the gap bar, which is the sliding surface with the recording medium, using an appropriate resist,
Then, by chemically etching the gap bar on which the mask pattern is formed, a concave-convex pattern corresponding to the mask pattern is formed on the surface of the gap bar, so that a track and an air-bearing surface are generated there. .

By the way, when a convex portion such as a track or an air-bearing surface is formed on the predetermined surface of the gap bar with high width dimension accuracy by such a method, the side etching amount and the linearity of the etching edge portion should be further improved. It is necessary to obtain stable dimensional accuracy, but when the etching depth by this chemical etching process becomes deep, the side etching amount also becomes large, and accordingly, dimensional accuracy deteriorates and linearity also deteriorates. It is inherent. For example, when a track is formed by performing chemical etching to a depth of about 30 μm, the track width accuracy deteriorates to about ± 1.5 μm.

(Problem to be Solved) Here, the present invention has been made in view of such circumstances, and the problem to be solved is to provide a predetermined gap bar in order to manufacture a magnetic head core. The purpose is to obtain a magnetic head core suitable for high-density recording by increasing the width accuracy when forming convex portions such as tracks on the surface by chemical etching.

(Solution) In the present invention, in order to solve the problem, a gap bar made of ferrite having a coil winding hole and a magnetic gap is used, and a surface serving as a sliding surface with respect to a recording medium is used. In the method of manufacturing a magnetic head core having a step of forming a convex portion such as a track having a predetermined width and height by performing a chemical etching process on the surface to be etched of the gap bar. A step of forming a primary convex portion having a width matching the width of the convex portion by applying a first mask and performing a first chemical etching process, and a size sufficient to cover the primary convex portion. Using a second mask, the center line of the primary protrusion and the center line of the second mask are aligned, and the second mask is attached to the first chemical etching surface of the gap bar. After granting And forming a secondary convex portion having a height corresponding to the height of the convex portion by performing a second chemical etching treatment, the secondary convex portion corresponding to the convex portion being formed. Is.

(Concrete Configuration) In short, the present invention forms a first mask having a predetermined pattern corresponding to a target convex portion of a track or the like on the surface of the gap bar that is a sliding surface of the recording medium. First, the gap bar surface is first shallowly etched by performing the first chemical etching process to form a primary convex portion with high dimensional accuracy, and then a second convex portion is formed on the primary convex portion so as to cover the primary convex portion. By forming a mask and performing a second chemical etching process, the area around the primary convex portion is etched to form a secondary convex portion having a height corresponding to the height of the target convex portion. By doing so, it is possible to significantly improve the dimensional accuracy of the target convex portion of the track or the like, particularly the width dimensional accuracy thereof, which is given by the secondary convex portion.

That is, as the two-step chemical etching process according to the present invention is schematically shown in FIG. 1, in the present invention, first, the first mask 2 is applied as shown in FIG. The first chemical etching treatment is applied to the surface 6 of the gap bar 4 which is to be slid with the recording medium, so that the first mask 2 as shown in FIG.
The primary convex portion 8 corresponding to is formed on the surface to be etched of the gap bar 4 with a predetermined height (h ₁ ). This primary convex portion 8 is
The width of the final convex portion of the target track or the like, more specifically, the width (w) corresponding to the width of the top portion of such convex portion is formed, and its height (h ₁ ) is This corresponds to the etching depth of the first chemical etching process: h ₁ . In the present invention, by making the etching depth: h ₁ shallow, it is intended to improve the dimensional accuracy of the primary convex portion 8, particularly the dimensional accuracy of its width: w, and therefore the etching depth: h ₁ As the depth becomes shallower, the dimensional accuracy of the primary projection 8 is improved, but the primary etching depth: h ₁ is determined according to the dimensional accuracy required for the primary projection 8. For example, the width of the primary convex portion 8: ± 1μ with respect to w
When the dimensional accuracy within m is required, the etching depth: h ₁ is within about 20 μm.
Also, as will be described later, the secondary convex portion that becomes the final convex shape
When 12 has a stepped shape as shown in FIG. 1 (g), the etching depth: h ₁ is generally 10 μm or more,
It is possible to avoid the influence of noise due to the formation of the pseudo track.

Then, after the primary convex portion 8 is formed in this way,
The first mask 2 is removed, and thereafter, the second mask 10 is formed so as to cover the primary convex portion 8 as shown in FIG. 1 (c). The second mask 10 has the entire surface of the primary convex portion 8 and the width of the primary convex portion 8 under the condition that the center line of the second mask 10 and the center line of the primary convex portion 8 are substantially aligned with each other. It is provided in a symmetrical form with respect to the center line so as to cover a predetermined range of the surface to be etched in the direction. The size of the second mask 10 is the same as that in FIGS. 1 (d) and 1 (e).
As shown in FIGS. (F) and (g), it is determined according to the second etching depth: h ₂ , in other words, the height of the secondary convex portion 12.

Next, in this way, the etched surface of the gap bar 4 provided with the second mask 10 is further subjected to the second chemical etching treatment, whereby the secondary convexities of the two kinds of shapes shown in the figure are formed. The part 12 is formed. That is, the surface to be etched (first chemical etching surface) of the gap bar 4 is sequentially etched by the second chemical etching process, and is removed at a predetermined etching depth: h ₂ . When the end point of the second chemical etching process is positioned within the inclined wall surface 8a of the primary convex portion 8 formed by the first chemical etching process, it is shown in FIGS. 1 (d) and 1 (e). The secondary convex portion 12 having the shape as described above is formed. On the other hand, when the end point 14 of the second chemical etching process does not reach the inside of the inclined wall surface 8a of the primary convex portion 8, as shown in FIGS. The part 12 is to be formed.

In any case, the end point 14 of the second chemical etching process is set so as not to reach the top surface 8b of the primary projection 8 beyond the inclined wall surface 8a of the primary projection 8. Since the dimensional accuracy in the width direction of the convex portion 12 can be maintained at a high level, a track for the purpose of the secondary convex portion 12 thus obtained,
It can be used as a convex portion such as an air bearing surface. Further, the height of this secondary convex portion 12 is the etching depth by the second chemical etching treatment: h ₂ or more, but the etching depth by the first chemical etching treatment: h ₁ , the second chemical etching treatment. Etching depth due to etching treatment: The height is equal to or less than the height (h ₁ + h ₂ ) obtained by adding h ₂ , and is equal to the height of the target convex portion of the track or the like.

By the way, an example of a more specific process relating to the method of manufacturing a magnetic head core according to the present invention is shown in FIGS. 2 (a) to 2 (g).

That is, FIG. 2 clarifies an example of manufacturing a magnetic head core for a monolithic RDD magnetic head. First, as shown in (a), a magnetic gap 16 having a predetermined gap is provided. Further, the elongated gap bar 20 in which an annular magnetic path is formed due to the existence of the coil winding hole 18 is manufactured using a ferrite material such as a ferrite single crystal according to a known method. Next, the first mask 24 is applied in a predetermined pattern to the surface 22 that is the sliding surface of the gap bar 20 with the recording medium so as to provide a target track or air floating surface. After that, [(b)] is subjected to the first chemical etching process to form the primary convex portions 26 [(c)].

Further, the gap bar 20 having the primary convex portion 26 is formed.
On the other hand, as shown in (d), the second mask 32 is applied so as to cover the primary convex portion 26. The alignment of the pattern of the first mask 24 and the pattern of the second mask 32 is accurately performed with reference to the alignment mark 30 or the like formed on the surface to be etched by the first chemical etching process. Be done. Also, 28 in (b)
Is a mask for forming the alignment mark 30. Then, the surface to be etched (first chemical etching processing surface) of the gap bar 20 provided with the second mask 32 is subjected to the second chemical etching processing, and as shown in (e). As described above, the secondary convex portion 34 corresponding to the track or the air bearing surface is formed.

Then, after that, with respect to the gap bar 20 on which the secondary convex portion 34 is formed, according to a conventional method, cutting processing for determining the length of the magnetic head core, leading lamp processing, further forming processing of the yoke portion, etc. After being processed [(f)], the individual magnetic head cores 36 are cut out [(g)]. In the magnetic head core 36 thus cut out, a pair of left and right air-bearing surfaces 38, 3
The 8 and the track 40 are formed by the secondary convex portions 34 formed in a predetermined pattern as described above.

By the way, the gap bar made of ferrite used in the present invention will be configured by appropriately adopting various magnetic materials such as Mn-Zn ferrite and Ni-Zn ferrite as in the conventional case. Particularly in the present invention, it is desirable that the surface portion of the gap bar to be etched is composed of a single crystal. However, it is not necessary that the entire ferrite material that gives the gap bars be composed of a single crystal body, and at least only the surface where the mask pattern is formed and the convex portion is formed by the chemical etching treatment is a ferrite single crystal. It is also possible to use a single crystal-polycrystalline composite material that is configured in some way. As is well known, the gap bar has a magnetic gap of a predetermined width and a coil winding hole, and an annular magnetic path is formed by the existence of the coil winding hole. .

Further, when at least the surface of the gap bar, which is the sliding surface with respect to the recording medium, is made of ferrite single crystal, the single crystal surface to be etched is disclosed in Japanese Patent Application No. 62-171666. (100),
The crystal orientations of (110), (311), (332), (611), and (331) are advantageously used. And, the linearity of the etching ridge formed by etching is ± 5 μm.
The crystal orientation of the etched surface is selected from the above, and the boundary of the mask pattern is a single crystal (100) or (110) plane in order to maintain the cross-sectional shape to be line symmetric within the range of m. It is set to be included in. Therefore, for example, when the (100) plane is selected as the surface to be etched, the mask pattern is formed so as to extend in the <100> or <110> axis direction, and when the (311) plane is selected, , The mask pattern is formed so as to extend in the <332> axis direction.

For other similar reasons, the combination of the appropriate crystal orientation and the direction in which the boundary line of the mask pattern extends is (110) and <100>, (110) and <110>, (332) and <311>, respectively. , (611) and <331>, and (331) and <611> are suitably selected.

The surface to be etched of such a gap bar has a surface roughness that affects the dimensional accuracy after etching. It is desirable that the surface be treated. Further, the surface to be etched, prior to being subjected to the two-step chemical etching treatment according to the present invention, a surface treatment with an aqueous solution of an amine compound such as an alkanolamine at a concentration of 50% or less,
Either an etching treatment with an acid solution such as a phosphoric acid aqueous solution to a depth of at least 10 Å or more, and an annealing treatment in an inert gas such as N ₂ (about 200 to 600 ° C), or a combination of them. It is preferably applied to stabilize the adhesion of the surface to be etched to the mask material. Note that this adhesiveness affects the dimensional accuracy of the width of the (secondary) convex portion such as the track or the air bearing surface formed by etching, and further the angle of the inclined wall surface.

In addition, in order to perform the first and second chemical etching treatments according to the present invention on the etched surface (sliding surface) of the gap bar that has been subjected to this pretreatment, in the predetermined pattern, the first and second chemical etching treatments are performed. The masks are sequentially formed. For this purpose, a known method such as screen printing is appropriately selected from the viewpoint of required accuracy and economical efficiency. Above all, a photoresist is used because of the pattern accuracy and the process simplicity. A method by photolithography is adopted. As the mask, it is possible to use various types of masks such as positive type or negative type photoresist, SiO or SiO ₂ formed by vacuum deposition, sputtering or CVD method, etc. Along with this, it will be appropriately selected from the viewpoint of the adhesion to the ferrite surface of the mask, etc., but as described above, the photoresist is advantageously used in consideration of the simplicity of the process. .

Furthermore, the first and second chemical etching treatments according to the present invention are sequentially performed on the etched surface of the gap bar provided with the first and second masks in the predetermined pattern as described above. However, as the etching liquid, a phosphoric acid-based acid aqueous solution is generally used, and the intended chemical etching is performed by immersing the gap bar in the phosphoric acid-based acid aqueous solution. The concentration of the phosphoric acid-based acid aqueous solution and the etching rate, and the solution temperature and the etching rate at that time have the relationships shown in FIGS. 3 and 4, respectively. Based on this relationship, each etching condition can be appropriately selected according to the target etching depths: h ₁ and h ₂ in the first and second chemical etching processes, respectively.

A resin such as a photoresist, which is a mask material, swells when it is dipped in an aqueous solution for a long time and its adhesive strength is reduced.
Therefore, the concentration and liquid temperature of the phosphoric acid-based acid aqueous solution will be appropriately selected depending on the etching depth in each chemical etching treatment, but if the concentration is less than 10% by weight, the etching rate becomes too slow, On the other hand, if it exceeds 85% by weight, the etching rate is high but the viscosity becomes high, making it difficult to perform etching with high precision. Therefore, the concentration is preferably in the range of 10 to 85% by weight. Also, when the liquid temperature exceeds 90 ° C, evaporation of water is severe, the concentration changes greatly, and it becomes difficult to control the liquid temperature.
On the other hand, if the temperature is lower than 40 ° C., the etching rate is slow, so it is usually desirable to use a liquid temperature in the range of 40 to 90 ° C.

The phosphoric acid-based acid aqueous solution used here does not mean only an aqueous solution consisting of phosphoric acid alone, but also an aqueous solution containing a small amount of another acid such as sulfuric acid in phosphoric acid. And, phosphoric acid-based means that phosphoric acid is contained in an amount of 80% or more based on the whole acid.

The present invention is by no means limited to the above specific description and preferred embodiments, and various changes, modifications, improvements and the like based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It is to be understood that the present invention is also embodied in addition to the above, and the present invention also includes those embodiments.

For example, in the above specific description, the description is based mainly on the magnetic head core for RDD, but the present invention is by no means limited to this, and the magnetic head core for FDD or the magnetic head for VTR is not limited thereto. The present invention is advantageously applied to the manufacture of magnetic cores, so that the convex portions of the recording / reproducing tracks and the like formed on the sliding surfaces of the magnetic head cores are formed with high dimensional accuracy.

(Examples) Hereinafter, some examples of the present invention will be shown in order to more specifically clarify the present invention. However, the present invention is not limited to the description by the description of the examples. It goes without saying that this is not what is done.

Example 1 Mn-Zn composed of (100), (110) and (110) planes
Using a ferrite single crystal plate material, its (110) surface is mirror-polished by a conventional method with diamond abrasive grains with a grain size of 1/4 μm so that the surface roughness is R _max : 0.02 μm or less. And then heated to 50 ° C. in (1 + 10) H ₃ PO ₄ aqueous solution.
The surface is etched by 1000Å by immersing for 4 minutes, and then 400 ℃ in N ₂ atmosphere (O ₂ concentration <30ppm).
And annealed for 30 minutes.

Then, on the mirror-polished surface (surface to be etched) of the pretreated Mn-Zn ferrite single crystal plate (110) surface, a rectangular resist pattern extending in the longitudinal direction in the direction perpendicular to the (100) surface, It was formed under the photolithography conditions shown in Table 1 below.

Then, with respect to the obtained Mn-Zn ferrite single crystal plate to which the resist pattern (mask) was applied, H ₃ PO ₄
In a phosphoric acid aqueous solution with a concentration of 77.8% by weight and a liquid temperature of 80 ° C,
Chemical etching treatment was performed with different etching times to obtain ferrite single crystal plates with various etching depths.

The dimensional accuracy of the etching depth of the ferrite single crystal plate chemically etched in this way and the width in the lateral direction of the rectangular pattern formed therein was measured, and the results are shown in Table 2 below. As is apparent, when the etching depth is shallow, the width dimension accuracy of the convex pattern to be formed is extremely high. After forming the primary projections that give the projections, the second chemical etching process is further performed to etch around the primary projections to form final projections such as tracks with high dimensional accuracy. It is understood that it is possible.

Example 2 According to the process shown in FIG. 2, a monolithic RDD
A magnetic head core was manufactured.

First, there, the magnetic gap 16 and the coil winding hole 18 at predetermined intervals are formed by the Mn-Zn ferrite single crystal combined so that the gap facing surface becomes the (100) surface and the sliding surface becomes the (110) surface. After manufacturing a so-called gap bar 20 having an annular magnetic path, the surface 22 which is a sliding surface of the so-called gap bar 20 has a particle size of 1/4 so that the depth of the magnetic gap 16 becomes 10 μm.
It was mirror-polished with diamond abrasive grains of μm. afterwards,
The gap bar 20 was annealed at 400 ° C. for 30 minutes in an N ₂ atmosphere, then ultrasonically cleaned in a 20% ethanolamine aqueous solution at 25 ° C. for 30 minutes, and thereafter, photolithography shown in Table 1 above. Under the conditions, the first mask 24 is formed, then H ₃ PO ₄ concentration: 77.8% by weight, liquid temperature: 8
The first chemical etching was performed by stirring in an aqueous phosphoric acid solution at 0 ° C. for 30 minutes to form primary protrusions 26 having a depth of 10 μm.

Further, after that, the first mask 24 is removed by peeling, and then the primary projection 26 formed by the first chemical etching process is covered with the photolithography conditions shown in Table 3 below. The second mask 32 was formed on the. The alignment of the pattern of the primary convex portion 26 and the second mask 32, the alignment mark 30 formed on the etched surface 22 by the first chemical etching process,
± 2μ by aligning with the alignment mark formed on the photomask when exposing the second mask 32
It could be done within m.

Further, after that, the gap bar 20 provided with the second mask 32 is stirred for 60 minutes in a phosphoric acid aqueous solution having a H ₃ PO ₄ concentration of 77.8 wt% and a liquid temperature of 80 ° C. to thereby obtain an etching depth. Was subjected to a second chemical etching treatment of 20 μm. The end point of the side etching at the end of this second chemical etching process ends in the inclined wall surface of the primary convex portion 26 as shown in the figure, and therefore, the air floating provided by the formed secondary convex portion 34. The width accuracy of the surface 38 and the track 40 was obtained with a dimensional accuracy of ± 0.7 μm determined by the first chemical etching process, even though their height (total etching depth) was about 30 μm.

In order to obtain such dimensional accuracy, at the end of the second chemical etching process, the end point (14) of the side etching is the upper surface (top surface) of the primary convex portion 26 previously formed.
It is necessary not to reach the end of the side etching, but the end point of this side etching is determined by the alignment accuracy of the second mask 32 and the side etching accuracy during the second chemical etching process, and the former is ± 2 μm. Since the latter is ± 1 μm and the side etching amount in the first chemical etching process is 10 μm, the end point of the side etching in the second chemical etching process is the primary convex portion 26.
It is possible to put it in the inclined plane of.

(Effects of the Invention) As is apparent from the above description, in the method of manufacturing a magnetic head core according to the present invention, a protrusion such as a track having a predetermined width and height formed on the sliding surface thereof is provided. ,
It is formed by the two-step chemical etching treatment method by first performing the chemical etching treatment that defines the width and then performing the second chemical etching treatment that gives the height. The dimensional accuracy of the convex portions can be effectively increased, and the width accuracy of such convex portions can be controlled within ± 1.0 μm.

Further, when forming a track according to the method of the present invention, it is possible to eliminate the pseudo track formed on both sides of the track by the conventional ion etching processing method, or to cope with such a pseudo track. Even if such a stepped portion is formed, it can be effectively moved away from the track surface so that it does not act as a nozzle.

Furthermore, according to the method of the present invention, the etching rate is fast, and etching can be performed at a speed of about 10 times compared with the etching rate by the conventional ion etching method: 0.03 μm / min, and thus the productivity is improved. It also has the advantage of being able to improve significantly.

[Brief description of drawings]

1 (a) to 1 (g) are explanatory views each showing an outline of a two-step chemical etching treatment step according to the present invention,
Figures 2 (a)-(g) are respectively RD according to the present invention.
FIG. 3 is a process explanatory view showing an example of a method for producing a D magnetic head core, FIG. 3 is a graph showing the relationship between the concentration of a phosphoric acid aqueous solution and an etching rate, and FIG. 4 is a phosphoric acid aqueous solution. 5 is a graph showing the relationship between the temperature of P and the etching rate. 2,24: First mask 4,20: Gap bar 8,26: Primary convex portion 10,32: Second mask 12,34: Secondary convex portion 16: Magnetic gap, 18: Coil winding hole 36: Magnetic head core 38: Air bearing surface, 40: Track

Claims (1)

(57) [Claims] 1. A gap bar made of ferrite having a coil winding hole and a magnetic gap is used, and a surface to be a sliding surface with respect to the recording medium is subjected to a chemical etching treatment to obtain a predetermined width. And a method of manufacturing a magnetic head core having a step of forming a convex portion having a height, wherein a first mask is applied to the etched surface of the gap bar, and a first chemical etching treatment is performed. The step of forming a primary convex portion having a width that matches the width of the convex portion, and using a second mask having a size sufficient to cover the primary convex portion, the center line of the primary convex portion and the The second mask is applied to the first chemical etching treatment surface of the gap bar while being aligned with the center line of the second mask, and then the second chemical etching treatment is performed to form the projections. To the height of the department Having a height match, and forming a secondary convex portion corresponding to the convex portion, a manufacturing method of a core for a magnetic head, which comprises.