JPH05279200A - Etching of ferrite - Google Patents

Abstract

PURPOSE:To improve the uniformity and accuracy of a chemically etched relief pattern formed on a ferrite single crystal surface by decreasing the fluctuation of the etching amounts in the single crystal surface or between individual ferrite crystals. CONSTITUTION:A mask pattern is applied to the surface of a ferrite single crystal and the crystal is subjected to chemical etching treatment in an aqueous solution composed mainly of phosphoric acid to form a relief pattern corresponding to the form of the mask. In the above process, a ferrite 28 is attached to a supporting plate 26 of a swinging apparatus 16 in a state fixed on a fixing jig 30 and moved in the form of figure '8' in a plane containing the single crystal surface to be etched while stirring the aqueous solution composed mainly of phosphoric acid with a propeller stirrer 18 placed above the single crystal surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a ferrite single crystal surface by chemical etching. In particular, in a magnetic head core using a ferrite single crystal, the surface thereof has a predetermined irregular shape, for example, a fixed magnetic disk device (RDD). The present invention relates to a chemical etching method suitably used for forming an air bearing surface (ABS surface), a track and the like in a magnetic head core.

[0002]

BACKGROUND ART Conventionally, ferrite single crystals have been used as a constituent material for magnetic head cores and the like, but in order to be applied to the intended use, it may be necessary to perform accurate processing. Yes, for example, JP-A-62-234214
In the publications and the like, a method of manufacturing a monolithic type RDD core (slider) by processing a ferrite member by photolithography and chemical etching is disclosed.

That is, when manufacturing a monolithic type RDD core by applying such photolithography and etching, as shown in FIG. 1, first, as shown in FIG.
A so-called gap bar 2 having an annular magnetic path having a magnetic gap 4 with a predetermined gap was formed from a ferrite single crystal, and its sliding surface 6 was mirror-polished to further remove processing strain on the mirror surface. After that, a predetermined etching pattern, in other words, a mask pattern is applied to the sliding surface 6 by the resist 8. Then, the gap bar 2 on which the mask pattern is formed is chemically etched to form a concavo-convex pattern corresponding to the mask pattern on the sliding surface 6 of the gap bar 2, whereby the air floating surface 10 and the track are formed. Twelve are born. Then, the individual RDD cores are cut out from the gap bar 2 that has been subjected to such processing.

By the way, according to such a method, the RD
When manufacturing an uneven processed product such as a D core, from the viewpoint of productivity, a plurality of sets of uneven shapes (patterns) corresponding to the product, such as the gap bar 2, are formed on the ferrite single crystal surface. Further, a method is adopted in which a plurality of ferrite single crystals such as the gap bar 2 are simultaneously immersed in an etching solution to perform chemical etching.
For example, in the past, a plate-shaped jig having a mounting surface in the vertical direction was radially mounted on a rotary drive shaft hanging in the etching tank, and the mounting surface in the vertical direction of the jig was mounted. On the other hand, when the ferrite single crystal member to be etched such as a gap bar is attached and fixed, the rotary drive shaft is rotated, thereby etching the ferrite single crystal member and the etching tank. The contact with the liquid is adapted to take place under a stirring mode.

However, in the ferrite single crystal member thus etched, for example, in the gap bar 2 which gives the above-mentioned magnetic head core, the liquid flow generated by the rotation causes a gap between the gap bars or in the gap bar. There are places with different flow velocities on the bar surface, the amount of etching varies between the gap bars and within the gap bar, and due to the directional liquid flow, the etching depth tends to be deeper on the downstream side of the mask, and In some cases, the etching may be locally non-uniform on the surface. The variation in the etching amount within one etching batch (composed of a plurality of gap bars that are simultaneously etched) is ± 1μ within the gap bar.
m within the batch (between the gap bars) was also ± 3 μm.

On the other hand, in the chemical etching process of the gap bar that provides the magnetic head core, the etching amount is set to avoid the influence of noise caused by the etched ferrite surface and to secure the S / N ratio of the signal. At least 20 μm, preferably 30 μm or more,
At that time, it is necessary for the track width and the width of the air-bearing surface to have a variation of ± 5 μm or less among these products. For that purpose, the variation of the etching amount within a batch is within ± 1.5 μm. Although it is necessary, as described above, the conventional etching method was not able to sufficiently meet the requirement.

[0007]

The present invention has been made in view of the above circumstances, and its object is to form an uneven pattern on a single crystal surface of ferrite by chemical etching. The object of the present invention is to provide a processing method capable of improving the uniformity and accuracy of the pattern by reducing the variation in the etching amount in the plane of the single crystal and further between the ferrites.

[0008]

According to the present invention, in order to solve such a problem, a predetermined mask pattern is provided on a single crystal plane of ferrite, and then the mask is subjected to chemical etching treatment in a phosphoric acid-based aqueous solution. When forming a concavo-convex pattern corresponding to the pattern on the single crystal surface of the ferrite, in the plane including the single crystal surface to be etched, the ferrite is randomly oriented at any point on the single crystal surface. A method of etching a ferrite characterized in that the phosphoric acid-based aqueous solution is agitated by an agitating means arranged above the single crystal plane while being swung so as to move Is.

In the method of the present invention as described above,
Preferably, a plurality of ferrites are arranged such that their etched single crystal planes are substantially in the same plane, and the plurality of ferrites are electrically connected to each other, and By performing the chemical etching treatment under the state, it is possible to more effectively improve the variation in the etching amount among the plurality of ferrites.

[0010]

Concrete Structure By the way, as ferrite to which the etching method according to the present invention is applied, Mn-Z
There is a ferrite member having a single crystal part in a part thereof in addition to a single single crystal body made of a material such as n-ferrite. The exposed single crystal plane of the single crystal portion of such a ferrite member is generally
According to a conventional method, mirror-polished with diamond abrasive grains,
The surface to be processed is smooth in advance. This is because the surface morphology of the single crystal plane to be etched also influences the surface texture of the resulting etched surface, regardless of the uniformity of etching in the subsequent chemical etching process. It should be noted that this mirror-polishing advantageously employs a polishing process using diamond abrasive grains having a grain size of 4 μm or less.

Further, such a ferrite may be, if necessary, in an inert atmosphere such as N ₂ prior to the processing according to the present invention being applied to the single crystal surface to be etched. Annealing treatment is applied. Note that this annealing treatment is generally performed at a temperature of about 200 ° C. to 600 ° C., preferably about 250 ° C. to 550 ° C. for at least 10 minutes or longer, preferably for 30 minutes or longer, Needless to say, if a glass such as a bonding glass or a gap glass is used for the ferrite, a temperature below the melting point of such glass is adopted.

Further, if necessary, the ferrite may be treated with a solution containing an amine compound or pre-etched with an aqueous solution of phosphoric acid as disclosed by the present applicant in Japanese Patent Application No. 63-75744. A known pretreatment such as a treatment is appropriately performed for the purpose of improving the linearity of the etching edge portion and the pattern accuracy.

In the present invention, a ferrite having a surface to be etched (single crystal surface) which has been subjected to the above-mentioned treatment is used, and a mask having a predetermined pattern is first formed on the surface to be etched. However, a known method such as screen printing is appropriately selected from the viewpoint of required accuracy and economical efficiency. Among them, it is preferable to use an exposure method using a photoresist because of pattern accuracy and process simplicity. The method will be adopted. As the mask, various types of masks such as positive type or negative type photoresist, metal such as Cr or SiO or SiO ₂ formed by vacuum deposition, sputtering, CVD method or the like can be used. It is possible, and in addition to the operability and the economical efficiency, it is appropriately selected in terms of the adhesion to the ferrite surface of the mask.

Next, on the etched single crystal surface of ferrite to which such a predetermined mask pattern is applied,
A chemical etching treatment is performed in a phosphoric acid-based aqueous solution, whereby an uneven pattern corresponding to the mask pattern is formed on the etched single crystal surface of the ferrite.

In the present invention, during this chemical etching treatment, the ferrite to be treated is moved in a random direction at any point on the single crystal plane within the plane including the single crystal plane to be etched. As described above, the phosphoric acid-based aqueous solution is agitated by the agitating means arranged above the single crystal plane while being rocked, whereby uniform etching of the ferrite single crystal plane can be achieved. It was decided.

In such a chemical etching process, for example, as shown in FIG. 2, a rocking device 16 and a propeller stirring device 18 are installed in a constant temperature bath 14 containing a phosphoric acid-based aqueous solution (shown by phantom lines). It can be carried out using an attached etching processing apparatus. This rocking device 1
6 includes a drive unit 20, a swing plate 22 that is swung by the drive unit 20, and a support column 24 and a support plate 26 that are integrally fixed to the swing plate 22. The support plate 26
Are arranged horizontally in a phosphoric acid-based aqueous solution, and can be swung in random directions in a horizontal plane. Then, on the support plate 26, as shown in FIG. 3, there is provided a fixing jig 30 in which a plurality of ferrites (gap bars) 28 are fixed with their single crystal faces to be etched up. , Multiple can be attached.

In the propeller agitator 18, the propeller 32 is rotatably driven by a reversing type motor 34, and the motor 34 is supported by a support tool (not shown), while the propeller 32 is supported. Is immersed in a phosphoric acid-based aqueous solution, and is positioned above the ferrite 28 mounted on the support plate 26 of the rocking device 16. Reference numeral 36 is a heater for heating the phosphoric acid-based aqueous solution to a predetermined temperature.

Therefore, during the etching process, the rocking device 1
6 is operated to swing the ferrite 28 so as to move an arbitrary point on the single crystal surface in a random direction, so that the ferrite 28 is moved along the single crystal surface to be etched,
A relative flow having a flow velocity higher than natural convection is generated between the single crystal surface and the phosphoric acid-based aqueous solution, and the flow has no directionality and a uniform flow is generated. It will be. In addition, by operating the propeller stirrer 18 during the etching process, the phosphoric acid-based aqueous solution in the constant temperature bath 14 is constantly stirred uniformly, and when the reversing type motor 34 is used, The rotation direction is reversed every predetermined time, so that the stirring becomes more uniform. As a result, uniform etching is realized, etching is not locally uneven in the etching surface, and the uniformity of the concavo-convex patterns formed on the ferrite single crystal surface is effectively increased. That will be the case.

With respect to the relative flow speed between the single crystal plane and the phosphoric acid-based aqueous solution, that is, the flow velocity, it should be at least larger than natural convection. When the flow rate is increased, as is clear from FIG. 6 showing the result of etching at a temperature of 70 ° C. using a phosphoric acid aqueous solution having a concentration of 80%, the etching rate decreases and the etching takes time. When the etching time becomes long, the adhesive force of the resist decreases, and the width accuracy of the formed track, the air-bearing surface, etc., in other words, the width accuracy of the concavo-convex pattern, deteriorates. Further, when the flow velocity is increased, the force of peeling the resist acts due to the liquid flow, which also reduces the width accuracy of the concavo-convex pattern. Therefore, in the present invention, in general, 1000 mm / se
The relative flow described above is induced so as to be c or less, and preferably 300 mm / sec or less in order to secure a sufficient etching rate.

In short, the oscillating speed of the oscillating device 16 and the propeller agitating device 18 are controlled so as to obtain such a flow velocity.
The rotation speed of is set to a low speed. In order to swing the ferrite 28 in random directions, for example,
It is conceivable that the support plate 26 of the rocking device 16 is alternately moved clockwise and counterclockwise along the "8" shape shown in FIG. In that case, the width W of the right-handed portion (or left-handed portion) and the length L from the right-handed portion to the left-handed portion are substantially equal so that the relative flow directions and flow velocities are not biased. It is desirable to set so that Also usually their width: W and length:
L is set to be larger than the individual size of the ferrite 28 (gap bar 2). Alternatively, the supporting plate 26 of the rocking device 16 can be slid along a circular shape centered on a point set outside the supporting plate 26.

The phosphoric acid-based aqueous solution used in the chemical etching treatment is an aqueous solution containing an acid mainly composed of phosphoric acid, and various known phosphoric acid-based aqueous solutions can be used. When the amount of water in the phosphoric acid-based aqueous solution is large, the etching process takes a long time. Therefore, generally, the upper limit of the amount of water is about 95% by weight, in other words, the lower limit of the acid concentration is 5%. It is desirable to keep it at about wt%.

Further, such a chemical etching treatment in a phosphoric acid-based aqueous solution is carried out at an appropriate temperature for a predetermined time in accordance with the target etching amount of the single crystal plane, that is, the etching depth. It will be,
As pointed out above, it is desirable to avoid adopting an etching time that is too long, because if the etching time becomes long, the adhesive force of the resist will decrease and the pattern accuracy will decrease. Preferably, an etching time of 3 hours or less is adopted. Also, regarding the etching treatment temperature, it is possible to adopt a temperature up to the boiling point of the phosphoric acid-based aqueous solution, but if the temperature is too high, the amount of water in the phosphoric acid-based aqueous solution will be changed, and effective etching will be performed. In general, it is desirable to carry out etching at a temperature in the range of room temperature to 90 ° C., usually 50 to 80 ° C.

By such a chemical etching operation, uniform etching is realized, and the uniformity of the ferrite concavo-convex patterns is improved. In the present invention, as shown in FIGS. 2 and 3. , Ferrite 28
When a plurality of ferrites 28 are simultaneously etched, the plurality of ferrites 28 are electrically connected to each other in order to further improve the variation in the etching amount between the plurality of ferrites 28 and further improve the uniformity of the uneven pattern. It will be conducted. The electrical continuity of the ferrites 28 can be realized by various known means, but normally, the fixing jig 30 is used.
The facing corners of the plurality of ferrites 28 arranged above are exposed, and the corners are exposed to each other.
As shown in FIG. 5, all ferrites 2 are connected by a conductive material such as carbon paste 38.
8 are electrically connected to each other. The carbon paste 38 may be provided so as to straddle between the adjacent fixing jigs 30, 30.

Although the reason for this mutual electrical conduction of the ferrites 28 is not yet clear, variations in the etching amount between the ferrites 28 connected to each other are effectively improved, so that the uneven pattern is made uniform. Properties can be significantly enhanced and the unevenness of the uneven pattern between them can be advantageously improved.

By removing the mask from the single crystal surface of the ferrite 28 which has been subjected to the uneven etching treatment as described above, the desired uneven pattern is uniformly and accurately formed on the single crystalline surface. Within the crystal plane, and between multiple single crystal planes (ferrite),
Thus, the uneven pattern with less variation can be advantageously realized.

[0026]

EXAMPLES In order to more specifically clarify the present invention, typical examples of the present invention will be shown below.
Further, it goes without saying that the description of such examples should not be construed as limiting in any way.

Example 1 Mn-Zn ferrite single crystal body (Fe ₂ O ₃ : 52.6)
Mol%, ZnO: 16.4 mol%, MnO: 31.0 mol%), according to the present invention, is applied to the gap bar as shown in FIG. , The sliding surface that is the etched surface,
After mirror-polishing with diamond abrasive grains in the same manner as in the conventional art, a plurality of (64) thereof are rocked by a fixing jig (30) as shown in FIGS. 2 and 3. (1
It was fixed horizontally on the support plate (26) of 6).

The plurality of gap bars (ferrite 28) fixed on the support plate (26) in this way are
The rocking device (16) and the propeller stirring device (18) were dipped in an etching solution consisting of a 0% concentration phosphoric acid aqueous solution.
While operating, the chemical etching treatment was performed at a temperature of 80 ° C. for 110 minutes. The support plate (2
6) is swung in the shape of “8”, and the swing stroke of the “8” is length L: 60 mm, width W: 60 mm (see FIG. 4), and the time required for one cycle is 3 It was 0.5 seconds. Further, the propeller (32) was rotated at a low speed of 30 rpm, while the rotation direction was reversed by a reversal cycle of 5 minutes / time.

As a result of such etching treatment, the variation of the etching amount within the gap bar was ± 0.5 μm, and the variation of the etching amount within the batch, that is, between the gap bars was ± 3.0 μm. From this result, it can be seen that the variation in the etching amount within the bar is reduced by the uniform flow of the liquid. However, the variation between the bars (within the batch) was not so different from the conventional method due to the difference in the surface state of the gap bar.

Example 2 As shown in FIG. 5, a plurality of gap bars (ferrite 28) were short-circuited with each other using a carbon paste (38), and then a chemical etching treatment was carried out in the same manner as in Example 1. did. The electrical resistance value between the gap bars after conducting with the carbon paste (38) was 2 kΩ or less.

As a result of such etching treatment, the variation in the etching amount in the gap bar was ± 0.5 μm, but the variation in the etching amount between the electrically conductive gap bars was ± 1.0 μm. It was confirmed that the variation within the batch (between gap bars) was remarkably improved.

[0032]

As is apparent from the above description, the ferrite etching method according to the present invention realizes a uniform etching process with less variation in the etching amount, so that the target uneven pattern can be accurately formed. It is well formed, and if a plurality of ferrites are electrically conducted to each other during the chemical etching treatment, the variation in the etching amount between the plurality of ferrites can be remarkably improved. It became.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an example of a method for manufacturing a magnetic head core of a fixed magnetic disk device.

FIG. 2 is an explanatory diagram showing an example of implementation of an etching processing method according to the present invention.

FIG. 3 is a plan view showing a state in which a plurality of ferrites are attached to a fixing jig.

FIG. 4 is an explanatory diagram showing an example of “8” swinging;

FIG. 5 is an explanatory view showing an example of a different etching method according to the present invention.

FIG. 6 is a graph showing an example of the relationship between the etching rate and the flow rate of a phosphoric acid aqueous solution.

[Explanation of symbols]

 2 Gap bar 4 Magnetic gap 6 Sliding surface 8 Resist 10 Air floating surface 12 Track 14 Constant temperature bath 16 Oscillating device 18 Propeller stirring device 26 Support plate 28 Ferrite 30 Fixing jig 32 Propeller 38 Carbon paste

Claims (2)

[Claims] 1. An uneven pattern corresponding to the mask pattern is formed on the ferrite single crystal surface by applying a predetermined mask pattern to the ferrite single crystal surface and then performing chemical etching in a phosphoric acid-based aqueous solution. In forming the ferrite, the ferrite is swung so as to move an arbitrary point on the single crystal plane in a random direction within a plane including the single crystal plane to be etched, while the single crystal plane is formed. An etching method of ferrite, characterized in that the phosphoric acid-based aqueous solution is agitated by an agitating means disposed above the. 2. A plurality of the ferrites are arranged such that their etching single crystal planes are located substantially in the same plane, and the plurality of ferrites are electrically connected to each other. The method for etching ferrite according to claim 1, wherein: