JP2010203974A - Method of evaluating durability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating durability for stably evaluating durability for damage caused by particles. <P>SOLUTION: First, a suspension 100 in which particles 110 are dispersed to a fluorine-based solvent 120 is dripped on the surface of a disk by a dripping/drying treatment of the suspension (step S102). Then, the suspension 100 is dried naturally and particles adhere to the surface of a disk. Further, seek operation is performed to the surface of a disk to which particles have adhered by a head slider 520 for evaluation by seek processing (step S104). The durability of a magnetic disk is evaluated, based on a criterion on whether there are not less than a number of permitted scratches on the surface of a disk after the seek operation in a scratch observation/evaluation processing (step S105). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a durability evaluation method for evaluating the durability against scratches caused by particles adhering to the surface of a storage medium such as a magnetic disk.

  Conventionally, as a durability evaluation for a storage medium such as a magnetic disk, for example, a reliability of evaluating whether or not the storage medium can withstand a standard number of access operations by a head in a hard disk device (HDD) without being damaged. Sexual evaluation is mentioned. In this reliability evaluation, a reliability evaluation for an access operation using a contact start / stop (CSS) method and a reliability evaluation for an access operation using a load / unload (L / UL) method are performed. Further, as the durability evaluation for the storage medium, the following sliding evaluation can be given. In this sliding evaluation, the storage medium is damaged by sliding over a specified time with a sliding pin made of Al-TiC, which is often used as a constituent material of the slider on which the head is mounted, or with the actual head slider itself. It is evaluated whether it can endure without sticking. In these durability evaluations, it is evaluated whether the storage medium is damaged more than allowable when the head repeatedly contacts the storage medium or when the head continues to contact the storage medium.

  Here, in an actual apparatus such as an HDD, in addition to such contact, the storage medium may be damaged due to dust or the like existing in the apparatus. Therefore, a method for evaluating whether or not the storage medium is damaged by performing an access operation to the storage medium in an atmosphere in which particles that are solid particles simulating such dusts are dispersed has been proposed (for example, (See Patent Document 1 and Patent Document 2.)

JP-A-2-181630 JP-A-7-120377

  However, in the durability evaluation by the access operation in the particle atmosphere, there is a possibility that the adhesion density and the adhesion position of the particles with respect to the storage medium change depending on the evaluation. Further, when such durability evaluation is repeatedly performed, a phenomenon may occur in which minute fragments generated when a certain storage medium is damaged are added to the atmosphere as new particles. As a result, there arises a problem that the load on the storage medium increases as the durability evaluation executed later.

  The object of the present invention is to solve the above-mentioned problems and to provide a durability evaluation method capable of stably evaluating the durability against scratches caused by particles.

  The basic form of the durability evaluation method for achieving the above object is a form having a grain adhesion process, an operation process, and an evaluation process described below.

  The particle adhesion process is a process in which particles are adhered on the surface of a storage medium for storing information in which an object approaches or contacts the surface and moves relatively along the surface when used. This particle adhesion process is carried out by dropping a suspension obtained by dispersing a plurality of particles in a dispersion liquid on the surface and volatilizing the dispersion liquid of the dropped suspension. Is attached to the surface of the storage medium.

  The operation process is a process in which the following processing is performed on the surface of the storage medium in which the grains are adhered to the surface by the grain adhesion process. That is, in this operation process, a test specimen simulating the above object is brought close to or in contact with the surface, and the test specimen is moved along the surface relative to the surface to thereby attach the grains. It is a process of crossing.

  The evaluation process is a process of evaluating the durability of the storage medium based on the number of scratches on the surface of the storage medium that has undergone the above operation process.

  According to the durability evaluation method of the present case, it is possible to stably evaluate the durability against damage caused by particles.

FIG. 1 is a process diagram showing a specific embodiment of the durability evaluation method described for the basic form. It is a photograph which shows one of the particle adhesion states confirmed with the high-intensity microscope about the magnetic disk of the some sample. It is the photograph which shows the surface after a seek about one of the magnetic disks of the sample which belongs to the lot evaluated as having sufficient durability. It is a photograph which shows the surface after a seek about one of the magnetic disks of the sample which belongs to the lot evaluated as insufficient durability.

  Hereinafter, specific embodiments of the durability evaluation method described above for the basic mode will be described with reference to the drawings.

  FIG. 1 is a process diagram showing a durability evaluation process which is a specific embodiment of the durability evaluation method described for the basic mode.

  The durability evaluation process of this specific embodiment is executed on a sample magnetic disk extracted for each lot from among the magnetic disks mass-produced in lot units. As a result, durability evaluation for the magnetic disks of each lot is performed.

  Also, unlike the present embodiment, such sample extraction and durability evaluation processing are executed at a timing such as when mass production of a newly designed magnetic disk is started or when manufacturing conditions are changed. May be.

  The durability evaluation process shown in the process diagram of FIG. 1 is roughly the following process. That is, in this durability evaluation process, a seek operation on the magnetic disk of the sample with particles attached is performed by an evaluation head equivalent to a head used in an apparatus such as an HDD on which the magnetic disk to be evaluated is mounted. . Then, the durability is evaluated by determining whether or not the surface of the sample magnetic disk is damaged by the seek operation.

  In this durability evaluation process, first, a plurality of particles 110 are dispersed in the fluorinated solvent 120 to create a suspension 100 (step S101).

  In the present embodiment, as will be described later, particles 110 are attached to the surface of the magnetic disk by dropping and drying the suspension 100 on the surface of the sample magnetic disk.

  In the processing of step S101, alumina or carbon particles 100 are used as the material of the suspension 100. In particular, alumina particles are preferred because they are used as general abrasives and are readily available. Further, in the present embodiment, the particles 100 having an average particle size of 3 μm or less are used. This is because particles having a particle size exceeding 3 μm may be repelled by the evaluation head during the seek operation.

  In the process of step S101, a fluorine-based solvent 120 having a surface tension of 20 mN / m or less and a heat of evaporation of 100 KJ / Kg or less is used as the material of the suspension 100. The reason why the surface tension in this range is used is that when the surface tension exceeds 20 mN / m, when the suspension 100 dropped on the surface of the sample magnetic disk is dried, the surface is dried on the surface. This is because spots may remain. The reason why the heat of evaporation is in the above range is that if the heat of evaporation exceeds 100 KJ / Kg, condensation may occur during the drying.

  Here, the magnetic disk to be evaluated in the durability evaluation process, that is, the magnetic disk mass-produced in the lot to which the sample magnetic disk 200 belongs, is on the surface in the same manner as a general magnetic disk for HDD mounting. A lubricant is applied. Some fluorinated solvents will melt such lubricants. Therefore, in the process of step S101 described above, as the material of the suspension 100, a fluorine-based solvent that does not melt the lubricant of the sample magnetic disk 200 is used.

  An example of a fluorine-based solvent that satisfies the above conditions is perfluorocarbon (PFC).

  In the process of step S101, a plurality of particles 110 are mixed in the fluorinated solvent 120 at a concentration in the range of 0.002 to 0.01 wt% and stirred to create the suspension 100. . This is because according to the suspension 100 corresponding to this concentration range, when a scratch is generated by the above-described seek operation, the scratch is easily observed.

  Subsequent to the processing in step S101, the suspension 100 is dropped onto the surface of the magnetic disk 200 and dried (step S102).

  In the process of step S102, first, the suspension 100 is dropped using the micropipette 300.

  In this dripping, first, a part of the suspension 100 prepared as described above is sucked by the micropipette 300. In the present embodiment, this suction is performed immediately after the stirring in the process of step S101 and when the particles 110 are uniformly dispersed in the fluorinated solvent 120. Following this suction, the suspension 100 is dropped from the micropipette 300 onto the surface of the sample magnetic disk 200 in a drop amount of 1 to 5 μL. This dropping amount is such that the diameter (dropping diameter) of the suspension 100 spreading on the surface after dropping is 3 to 10 mm. In the present embodiment, as the dropping position of the sample on the surface of the magnetic disk 200, the vicinity of the center between the edge of the disk fixing hole vacated in the center of the disk and the outer periphery is adopted. In this embodiment, all of the dropping amount, the dropping diameter, and the dropping position are values that make it easy to observe the scratches generated by the seek operation.

  In the process of step S102, following the dropping, the dropped suspension 100 is dried. In this embodiment, this drying is performed by natural drying for 1 to 5 minutes with respect to the magnetic disk 200 of the sample after the suspension 100 is dropped. By such natural drying, the fluorinated solvent 120 of the suspension 100 is volatilized, and the particles 100 are left on the surface of the sample magnetic disk 200.

  The processing from step S101 to step S102 described above corresponds to an example of the particle adhesion process in the basic form described above. The sample magnetic disk 200 corresponds to an example of a storage medium in this basic form. Further, the suspension 100 in FIG. 1 corresponds to an example of the suspension in this basic form. Further, the particle 110 in FIG. 1 corresponds to an example of a particle in this basic form. 1 corresponds to an example of the liquid to be dispersed in this basic form.

  Here, in the present embodiment, as described above, the fluorine-based solvent 120 having a surface tension of 20 mN / m or less is used as the material of the suspension 100 in the process of step S101 in FIG. This surface tension is lower than the surface tension of water of 73 mN / m. It is known that water leaves dry spots due to such high surface tension during drying. In this embodiment, generation of dry spots is avoided by using the fluorinated solvent 120 having a surface tension lower than that of water.

  This means that an application mode in which the liquid to be dispersed has a surface tension lower than that of water is preferable to the basic mode described above.

  The fluorinated solvent 120 in FIG. 1 also corresponds to an example of a dispersion liquid in this application mode.

  In the present embodiment, as the above-described fluorine-based solvent 120, a solvent that does not melt the lubricant of the sample magnetic disk 200 is used as described above. Thereby, it is avoided that the lubricant is dissolved into the suspension 100 dropped as described above.

  This means that the application modes described below are preferable to the basic mode described above. In this application mode, the storage medium has a surface coated with a lubricant. Further, in the dispersion liquid, the lubricant has non-melting property with respect to the dispersion liquid.

  The fluorinated solvent 120 in FIG. 1 also corresponds to an example of a dispersion liquid in this application mode.

  Subsequent to the processing described so far, in the durability evaluation processing of FIG. 1, it is confirmed by observing the adhesion location that the particles 110 are adhered in the desired adhesion state on the surface of the sample magnetic disk 200 (step). S103).

  In this embodiment, observation of an adhesion location is performed using the high-intensity microscope 400 typically shown in FIG. The high-intensity microscope 400 includes a stage 410 on which an observation object is placed, a high-intensity light source 420 that illuminates the observation field, a camera 430 that captures the observation field, and a monitor 440 that displays the captured image. I have.

  In the process of step S <b> 103, the sample magnetic disk 200 to which the particles 110 are attached is placed on the stage 410. Then, the position and orientation of the camera 430 are adjusted so that the spot where the particles 110 are attached is captured in the field of view. Then, the image of the part taken by the camera 430 is enlarged at a desired magnification and displayed on the monitor 440.

  In the process of step S103, it is visually checked whether or not the adhesion state such as the adhesion position, the adhesion density, and the adhesion amount of the particle 110 at the location where the particle 110 is adhered is the following desired adhesion state. It is judged by. That is, it is determined whether or not the particles 110 are adhered with a substantially uniform adhesion density and a sufficient adhesion amount within the above-described drop diameter range. When it is determined that the adhesion state of the particles 110 is not such an adhesion state, the adhered particles 110 are removed, and the processing from step S101 to step S102 is performed again. In the present embodiment, these processes are repeated until it is confirmed in step S103 that the particles 110 are attached in a desired attachment state.

  In the present embodiment, the adhesion state of the particles 110 as described above is easily controlled by the concentration of the suspension 100, the time interval from stirring to suction with the micropipette 300, the dropping position of the suspension 100, and the like. can do. In the present embodiment, a desired adhesion state can be reliably generated by such control of the adhesion state of the particles 110 and the above confirmation.

  This means that the application modes described below are preferable to the basic mode described above.

  This application mode includes an adhesion determination process for determining whether or not the adhesion state of the grains on the surface of the storage medium that has undergone the grain adhesion process satisfies a predetermined condition. In this application mode, the particle adhesion process is a process that is repeated until the adhesion determination process determines that the adhesion state satisfies the predetermined condition.

  The process of step S103 in this embodiment corresponds to an example of an adhesion determination process in this applied mode. Further, the processing from step S101 to step S102 in the present embodiment also corresponds to an example of a particle adhesion process in this applied mode.

  In the durability evaluation process of FIG. 1, when it is confirmed in the process of step S103 that the particles 110 have adhered in a desired adhesion state, the process proceeds to step S104.

  In the process of step S104, a seek operation is performed on the sample magnetic disk 200 for which the adhesion state of the particles 110 has been confirmed. In the present embodiment, this seek operation is performed using a tester 500 schematically shown in FIG.

  The processing in step S104 corresponds to an example of the operation process in the basic mode described above.

  The tester 500 includes a spin stand 510 that rotates and drives a magnetic disk around a rotation shaft 511, an arm 530 that has an evaluation head slider 520 mounted on the tip, and a seek operation on the evaluation head slider 520 by moving the arm 530. And a carriage 540 for performing the above. Here, as described above, the evaluation head slider 520 is equivalent to a head slider used in a device such as an HDD on which a magnetic disk to be evaluated to be mass-produced is mounted.

  The evaluation head slider 520 corresponds to an example of the “test object imitating an object” in the basic form described above.

  In this embodiment, by using such an evaluation head slider 520, durability can be evaluated with a load close to the load applied to the magnetic disk 200 by an actual head slider.

  This means that an application form in which the object is a slider mounted with a head for performing information storage and / or information reproduction with respect to the storage medium is preferable to the basic form. .

  The actual head slider imitated by the evaluation head slider 520 of this embodiment corresponds to an example of an object in this application mode.

  In the process of step S104, the sample magnetic disk 200 in which the adhesion state of the particles 110 is confirmed is mounted on the spin stand 510 and rotated. The rotation speed at this time is the same as the rotation speed of the magnetic disk in an apparatus such as an HDD on which the magnetic disk to be evaluated is mounted.

  Then, the evaluation head slider 520 performs a seek operation within a seek range that crosses the adhesion location of the particles 110. The seek operation at this time is a reciprocating operation with a frequency of 2 Hz over a seek time of 30 to 60 sec. In this embodiment, both the seek time and the frequency of the seek operation are values at which it is easy to observe scratches generated by the seek operation.

  In the present embodiment, the rotation of the sample magnetic disk 200 by the spin stand 510 and the above-described seek operation by the evaluation head slider 520 result in a state where scratches due to particles occur in an actual device such as an HDD. A close state is simulated. In the present embodiment, this makes it possible to evaluate the durability in accordance with the actual situation.

  This means that the application modes described below are preferable to the basic mode described above.

  In this application mode, the storage medium has a disk shape. The operation process is a process in which the storage medium is first rotated about the center of the storage medium and the next process is executed on the rotating storage medium. That is, this operation process is a process of moving the object from the center of the storage medium toward the outer periphery or from the outer periphery of the storage medium toward the center with respect to the rotating storage medium.

  The process of step S104 in FIG. 1 also corresponds to an example of an operation process in this applied form.

  In the durability evaluation process of FIG. 1, following the process of step S104, it is observed whether or not a large number of scratches exceeding the allowable limit are formed on the surface of the sample magnetic disk 200 by the seek operation in the process of step S104. (Step S105). The processing in step S105 corresponds to an example of an evaluation process in the basic form described above.

  In the present embodiment, the observation in step S105 is performed using the high-intensity microscope 400 used for observing the adhesion state of the particles 110 in step S103.

  In the process of step S 103, the sample magnetic disk 200 that has undergone the above-described seek operation is placed on the stage 410. Then, the position and orientation of the camera 430 are adjusted so that a portion corresponding to the seek range is captured in the field of view. Then, the image of the part taken by the camera 430 is enlarged at a desired magnification and displayed on the monitor 440.

  In this embodiment, when it is confirmed by this observation that there are no more scratches than allowable, the magnetic disk mass-produced in the same lot as the sample magnetic disk 200 has sufficient durability. It is evaluated that On the other hand, when the existence of a large number of scratches exceeding the allowable range is confirmed by this observation, it is evaluated that the durability of the magnetic disk mass-produced in this lot is insufficient.

  In the durability evaluation process of FIG. 1 described above, a desired adhesion state can be reliably realized by dropping the suspension described above. As a result, according to the durability evaluation process of FIG. 1, even when the sample magnetic disk 200 is replaced and the durability evaluation is repeatedly performed, the evaluation is performed every time. Can be carried out under the conditions described above. That is, according to the durability evaluation process of FIG. 1, it is possible to stably evaluate the durability against scratches caused by particles.

  In the above, PFC is exemplified as an example of the fluorinated solvent, but the fluorinated solvent used in the suspension is not limited to this. The fluorine-based solvent may be, for example, hydrofluorocarbon (HFC) or hydrofluoroether (HFE).

  In the above description, specific numerical ranges for the drop diameter, the drop position, the seek range, and the seek time are exemplified, but the durability evaluation method of the present invention is not limited to these numerical ranges. The drop diameter, drop position, seek range, seek time, and the like are appropriately determined according to the size of the magnetic disk to be evaluated and the access state of the magnetic disk mounting apparatus.

  Next, the present case will be described more specifically based on examples corresponding to the above-described embodiment, but the present case is not limited to the following examples.

  Specific examples of particles and fluorine-based solvents used in this example, and specific examples of the high-intensity microscope and tester used in this example are shown in Table 1 below.

  As shown in Table 1, in this example, alumina particles having an average particle diameter of 3 μm were used as particles. In this example, FC77, a PFC manufactured by Sumitomo 3M Co., was used as the fluorinated solvent. Here, as this PFC made by Sumitomo 3M, PF5060 can be used in addition to this FC77.

  In this example, a suspension having a concentration of 0.005 wt% was prepared.

  In this example, immediately after stirring, the suspension was sucked into the micropipette, and the suspension was dropped in a dropping amount of 2 μL. Further, in this dropping, the dropping position is in the vicinity of a position 24 mm away from the center of the disk. Further, the dropping diameter is about 5 mm. Moreover, in this Example, the natural drying after dripping was performed over 1 minute.

  Further, in this example, the particle adhesion state was confirmed using Micro-MAX (model number: VMX-2100), which is a high-intensity microscope manufactured by Vision Cytec.

  Here, in this embodiment, the adhesion and confirmation of the particles described above were performed on a sample magnetic disk extracted from each of two types of lots having different design and manufacturing conditions.

  FIG. 2 is a photograph showing one of the particle adhesion states confirmed with a high-intensity microscope for a plurality of sample magnetic disks.

  In the photograph of FIG. 2, it can be seen that particles are attached with a substantially uniform adhesion density and a sufficient adhesion amount in a region A circled in FIG. In this example, the magnetic disk of any sample was confirmed to have almost the same adhesion state as that shown in the photograph of FIG. 2 after the adhesion of the particles.

  Next, in this embodiment, the following seek operation was performed for each sample magnetic disk. In this example, the seek operation was performed using an L / UL tester (model number: KT701) manufactured by Koyo Seisakusho. Using this apparatus, the sample magnetic disk was rotationally driven at the same rotational speed as that of the magnetic disk in the apparatus on which the magnetic disk to be evaluated was mounted. Then, a seek operation called a reciprocating motion with a frequency of 2 Hz was performed over a seek time of 50 sec in a seek range where the distance from the center of the disk ranges from 20 mm to 28 mm.

  After this seek operation, scratches were observed using Micro-MAX (model number: VMX-2100), which is a high-intensity microscope manufactured by Vision Cytec.

  As a result of this observation, an evaluation result is obtained that one of the above two lots has no scratches and has sufficient durability, and the other lot has a number of scratches that are more than allowable. It was confirmed that an evaluation result indicating that the durability was insufficient was obtained. Furthermore, for any lot, the same evaluation results were obtained between the magnetic disks of the same lot.

  FIG. 3 is a photograph showing the surface after seek for one of the sample magnetic disks belonging to the lot evaluated as having sufficient durability.

  From the photograph of FIG. 3, there is no visible scratch on the surface of the sample magnetic disk shown in this photograph, and the sample magnetic disk has sufficient durability against scratches caused by particles. You can see that Further, the surface of the other sample magnetic disks belonging to this lot was almost in the same state as shown in the photograph of FIG.

  FIG. 4 is a photograph showing the surface after seek for one of the sample magnetic disks belonging to the lot evaluated as having insufficient durability.

  In the photograph of FIG. 4, many scratches are clearly visible in the band-like region B in the drawing. From this, it can be seen that the sample magnetic disk shown in the photograph of FIG. 4 has insufficient durability against scratches caused by particles. Further, the surface of the other sample magnetic disks belonging to this lot was almost the same as the state shown in the photograph of FIG.

  As described above in detail with reference to the embodiment, according to the durability evaluation process shown in FIG. 1, each evaluation can be performed under stable conditions in which particle adhesion states are substantially similar to each other. it can. And the evaluation result stable as mentioned above can be obtained by the evaluation under such a stable condition. That is, according to the durability evaluation process shown in FIG. 1, it is possible to stably evaluate the durability against scratches caused by particles.

  Hereinafter, the following additional remarks are disclosed regarding various forms including the basic form described above.

(Appendix 1)
A suspension in which a plurality of grains are dispersed in a dispersion liquid on the surface of a storage medium for storing information, in which an object approaches or contacts the surface and moves relatively along the surface during use. Dropping and volatilizing the liquid to be dispersed of the dropped suspension, thereby depositing the particles on the surface of the storage medium,
A test object imitating the object is brought close to or in contact with the surface of the storage medium having the particles attached to the surface by the particle adhesion process, and the test object is brought into contact with the surface relative to the surface. An operation process of traversing the adhesion site of the grains by moving along the
A durability evaluation method comprising: an evaluation process for evaluating the durability of the storage medium based on the number of scratches on the surface of the storage medium that has undergone the operation process.

(Appendix 2)
The durability evaluation method according to claim 1, wherein the object is a slider on which a head for executing information storage and / or information reproduction with respect to the storage medium is mounted.

(Appendix 3)
An adhesion determination process for determining whether or not the adhesion state of the grains on the surface of the storage medium that has undergone the grain adhesion process satisfies a predetermined condition;
The durability evaluation method according to appendix 1 or 2, wherein the grain adhesion process is a process that is repeated until it is determined in the adhesion determination process that the adhesion state satisfies the predetermined condition.

(Appendix 4)
The durability evaluation method according to any one of supplementary notes 1 to 3, wherein the dispersion liquid has a surface tension lower than that of water.

(Appendix 5)
The storage medium has a surface coated with a lubricant,
5. The durability evaluation method according to any one of appendices 1 to 4, wherein the dispersion liquid is one in which the lubricant is non-meltable with respect to the dispersion liquid.

(Appendix 6)
The storage medium has a disk shape;
The operation process rotates the storage medium around the center of the storage medium, and the object is moved from the center of the storage medium toward the outer periphery with respect to the rotating storage medium or the storage medium 6. The durability evaluation method according to any one of supplementary notes 1 to 5, wherein the durability evaluation is a process of moving from the outer periphery toward the center.

DESCRIPTION OF SYMBOLS 100 Suspension 110 Particle | grain 120 Fluorinated solvent 200 Sample magnetic disk 300 Micropipette 400 High-intensity microscope 410 Stage 420 Light source 430 Camera 440 Monitor 500 Tester 510 Spin stand 511 Rotating shaft 520 Evaluation head slider 530 Arm 540 Carriage

Claims (3)

A suspension in which a plurality of grains are dispersed in a dispersion liquid on the surface of a storage medium for storing information, in which an object approaches or contacts the surface and moves relatively along the surface during use. Dropping and volatilizing the liquid to be dispersed of the dropped suspension, thereby depositing the particles on the surface of the storage medium,
A test object imitating the object is brought close to or in contact with the surface of the storage medium having the particles attached to the surface by the particle adhesion process, and the test object is brought into contact with the surface relative to the surface. An operation process of traversing the adhesion site of the grains by moving along the
A durability evaluation method comprising: an evaluation process for evaluating the durability of the storage medium based on the number of scratches on the surface of the storage medium that has undergone the operation process.   The durability evaluation method according to claim 1, wherein the dispersion liquid has a surface tension lower than that of water. The storage medium has a surface coated with a lubricant,
The durability evaluation method according to claim 1, wherein the liquid dispersion is one in which the lubricant is non-meltable with respect to the liquid dispersion.