JP4161868B2 - Method for measuring natural frequency of air film of magnetic head - Google Patents
Method for measuring natural frequency of air film of magnetic head Download PDFInfo
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- JP4161868B2 JP4161868B2 JP2003351490A JP2003351490A JP4161868B2 JP 4161868 B2 JP4161868 B2 JP 4161868B2 JP 2003351490 A JP2003351490 A JP 2003351490A JP 2003351490 A JP2003351490 A JP 2003351490A JP 4161868 B2 JP4161868 B2 JP 4161868B2
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- magnetic head
- air film
- natural frequency
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- 238000000034 method Methods 0.000 title claims description 12
- 230000001050 lubricating effect Effects 0.000 claims description 15
- 239000010687 lubricating oil Substances 0.000 claims description 13
- 238000005259 measurement Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- -1 perfluoro Chemical group 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Images
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- Supporting Of Heads In Record-Carrier Devices (AREA)
- Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
- Manufacturing Of Magnetic Record Carriers (AREA)
Description
本発明は、磁気ディスクの回転による動圧空気軸受けにより浮上する磁気ヘッドの空気膜の固有振動数を測定する方法に関する。 The present invention relates to a method for measuring the natural frequency of an air film of a magnetic head that is levitated by a dynamic pressure air bearing caused by rotation of a magnetic disk.
固定磁気ディスク装置（いわゆるハードディスク装置：ＨＤＤ）においては、記録密度を増大させるため、磁気ヘッドの浮上量（磁気ヘッドの底面と磁気ディスク表面との距離）の狭小化が急速に進行されている。浮上量が低減すると、磁気ヘッドの浮上姿勢が磁気ディスク表面のうねりの影響を受けやすくなり、特に磁気ヘッドの浮上を支えている磁気ディスクと磁気ヘッドスライダの間の空気膜（以下「磁気ヘッドの空気膜」という。）の固有振動数と磁気ディスク表面のうねりの振動数が一致した場合には、共振現象が生じて磁気ヘッドの浮上が不安定となり、磁気ディスク表面との接触を誘発し、最悪の場合にはヘッドクラッシュに至る。
このため、磁気ヘッドの空気膜の固有振動数を把握することは、ＨＤＤの設計を行う上で重要である（例えば特許文献１参照）。
In a fixed magnetic disk device (so-called hard disk device: HDD), the flying height of the magnetic head (the distance between the bottom surface of the magnetic head and the surface of the magnetic disk) is rapidly decreasing in order to increase the recording density. When the flying height is reduced, the flying posture of the magnetic head becomes more susceptible to the waviness of the surface of the magnetic disk, and in particular, an air film (hereinafter referred to as “the magnetic head of the magnetic head”) If the natural frequency of the air film matches the frequency of the undulation of the magnetic disk surface, a resonance phenomenon occurs and the flying of the magnetic head becomes unstable, inducing contact with the magnetic disk surface, In the worst case, it leads to a head crash.
For this reason, grasping the natural frequency of the air film of the magnetic head is important in designing the HDD (see, for example, Patent Document 1).
磁気ヘッドの空気膜の固有振動数を測定する方法としては、レーザードップラー振動計（ＬＤＶ）により磁気ヘッドの浮上量変動を直接測定して空気膜の固有振動数を導出する方法がある。
しかしながら、上述の方法により磁気ヘッドの空気膜の固有振動数を測定する場合には、次のような問題がある。
すなわち、ＬＤＶを用いる場合、磁気ヘッドスライダの背面に対してレーザー光を照射するが、磁気ヘッドを保持するサスペンションのタイプによっては、磁気ヘッドスライダの背面を覆い隠してしまう形状のものがあり、このタイプの磁気ヘッドに対しては磁気ヘッドの浮上量変動を測定することができない。
本発明は、上述の点に鑑み、磁気ヘッドを保持するサスペンションのタイプによらずに、磁気ヘッドの空気膜の固有振動数を測定する方法を提供することを目的とする。
However, when the natural frequency of the air film of the magnetic head is measured by the above method, there are the following problems.
That is, when LDV is used, the back surface of the magnetic head slider is irradiated with laser light, but depending on the type of suspension that holds the magnetic head, there is a shape that covers the back surface of the magnetic head slider. For a type of magnetic head, the flying height fluctuation of the magnetic head cannot be measured.
An object of the present invention is to provide a method for measuring the natural frequency of an air film of a magnetic head regardless of the type of suspension that holds the magnetic head.
本発明は、上述の目的を達成するため、最表面に液体潤滑剤が塗布されて潤滑層が形成されてなる磁気ディスクの回転によりその表面上に浮上する磁気ヘッドの空気膜の固有振動数測定方法において、前記磁気ヘッドを浮上させたときに前記潤滑層に形成される液体潤滑剤の流動分布を測定し、この液体潤滑剤の流動分布から前記磁気ヘッドの固有振動数を導出することを特徴としている。
磁気ディスクの回転により磁気ヘッドを浮上させると、磁気ヘッドの空気膜の固有振動数で空気膜の圧力が変動し、この空気膜の圧力の変動によって液体潤滑剤の流動分布が潤滑層に形成される。
従って、この液体潤滑剤の流動分布を測定することにより、磁気ヘッドの空気膜の固有振動数を測定することができる。
In order to achieve the above-mentioned object, the present invention measures the natural frequency of the air film of a magnetic head that floats on the surface of a magnetic disk formed by applying a liquid lubricant to the outermost surface and forming a lubricating layer. In the method, the flow distribution of the liquid lubricant formed in the lubricating layer when the magnetic head is levitated is measured, and the natural frequency of the magnetic head is derived from the flow distribution of the liquid lubricant. It is said.
When the magnetic head is levitated by rotating the magnetic disk, the air film pressure fluctuates at the natural frequency of the air film of the magnetic head, and the flow distribution of the liquid lubricant is formed in the lubricating layer by the fluctuation of the air film pressure. The
Therefore, the natural frequency of the air film of the magnetic head can be measured by measuring the flow distribution of the liquid lubricant.
本発明によれば、磁気ヘッドを浮上させたときに潤滑層に形成される液体潤滑剤の流動分布を測定し、この液体潤滑剤の流動分布から磁気ヘッドの固有振動数を導出するようにしたので、液体潤滑剤の流動分布を測定することにより、磁気ヘッドのサスペンションのタイプによらずに、磁気ヘッドの空気膜の固有振動数を測定することができる。 According to the present invention, the flow distribution of the liquid lubricant formed in the lubricating layer when the magnetic head is levitated is measured, and the natural frequency of the magnetic head is derived from the flow distribution of the liquid lubricant. Therefore, by measuring the flow distribution of the liquid lubricant, the natural frequency of the air film of the magnetic head can be measured regardless of the type of suspension of the magnetic head.
図１は、本発明に係る実施形態の磁気ヘッドと磁気ディスクの関係を示す模式図である。図において、１は磁気ヘッド（スライダ）、３０は、非磁性基板上に下地層（不図示）を介して磁性膜層５，保護膜層４，潤滑層３がこの順に積層された磁気ディスクであり、いずれも周知のものである。
この磁気ディスク３０の回転により誘発される空気流６が磁気ヘッド（スライダ）１の前方から流入することで、磁気ヘッド（スライダ）１と磁気ディスク３０の間の空気膜２に圧力が発生し、磁気ヘッド１の浮上を支える。
一方、磁気ディスク３０の最表面には、液体潤滑剤を塗布してなる潤滑層３が形成され、空気膜２は主として磁気ヘッド１のスライダ形状に依存した固有振動数を有するから、この固有振動数で空気膜２の圧力が変動し、この空気膜２の圧力の変動によって潤滑層３の表面に凹凸形状が形成される。
FIG. 1 is a schematic diagram showing the relationship between a magnetic head and a magnetic disk according to an embodiment of the present invention. In the figure, 1 is a magnetic head (slider), and 30 is a magnetic disk in which a magnetic film layer 5, a
When the
On the other hand, the
この潤滑層３の表面に形成される凹凸形状を潤滑層分布測定装置により測定し、潤滑層３の凹凸形状の周期をＦＦＴ(Fast Fourier Transform)解析により求め、磁気ヘッド１の空気膜２の固有振動数を導出する。
The uneven shape formed on the surface of the lubricating
磁気ヘッドのＨＤＩ(Head Disk Interface)特性を評価するＣＳＳ(Contact Start Stop)テスタと呼ばれる試験装置において、スライダ背面が覆い隠されないタイプの３０％サイズの磁気ヘッドをフッ素系の液体潤滑剤（パーフルオロポリエーテル：ＰＦＰＥ）を表面に塗布してなる磁気ディスク上に設置し、この磁気ヘッドを回転数１０，０００ｒｐｍで回転させた磁気ディスク上の半径位置３０ｍｍで２０分間定点浮上させた。
この間にレーザードップラー振動計（ＬＤＶ）を用い、磁気ヘッドのスライダ背面にレーサー光を照射して磁気ヘッドの浮上量変動を測定し、その浮上量変動から振動数を求めたところ、図２に示すように１００ｋＨｚ，１４０ｋＨｚにおいてピーク７，８が見られた。
一方、磁気ヘッド浮上後の磁気ディスクの表面をＯＳＡ(Optical Surface Analyzer)と呼ばれる光学式磁気ディスク表面検査装置により観察したところ、磁気ヘッドの浮上通過位置である半径位置３０ｍｍ付近において、高さ０．１ｎｍから０．３ｎｍの潤滑層の凹凸が見られた。
In a test device called CSS (Contact Start Stop) tester that evaluates the HDI (Head Disk Interface) characteristics of a magnetic head, a 30% size magnetic head that does not cover the back of the slider is replaced with a fluorine-based liquid lubricant (perfluoro (Polyether: PFPE) was placed on a magnetic disk coated on the surface, and this magnetic head was floated at a fixed point for 20 minutes at a radial position of 30 mm on a magnetic disk rotated at a rotational speed of 10,000 rpm.
During this time, a laser Doppler vibrometer (LDV) was used to measure the flying height fluctuation of the magnetic head by irradiating the back surface of the slider of the magnetic head with laser light, and the frequency was calculated from the flying height fluctuation. Thus,
On the other hand, when the surface of the magnetic disk after flying the magnetic head was observed with an optical magnetic disk surface inspection apparatus called OSA (Optical Surface Analyzer), the height was 0. Unevenness of the lubricating layer of 1 nm to 0.3 nm was observed.
観察された周方向の潤滑層の凹凸形状に対しＦＦＴ解析を行ったところ、図３に示すように１０５ｋＨｚ，１３８ｋＨｚにピーク９，１０が見られた。
このように、潤滑層の凹凸形状からＦＦＴ解析により求めた磁気ヘッドの空気膜の固有振動数は、従来の測定方法であるＬＤＶでの測定結果とほぼ一致し、本発明の測定方法により従来と同等の測定結果を得ることができる。
When FFT analysis was performed on the observed uneven shape of the lubricating layer in the circumferential direction,
As described above, the natural frequency of the air film of the magnetic head obtained by FFT analysis from the uneven shape of the lubricating layer almost coincides with the measurement result of the conventional measurement method LDV. Equivalent measurement results can be obtained.
本発明の磁気ヘッドの空気膜の固有振動数測定方法は、その測定結果をＨＤＤの設計に用いて磁気ヘッドの安定走行を可能とする。 The method for measuring the natural frequency of the air film of the magnetic head according to the present invention enables stable running of the magnetic head by using the measurement result for designing the HDD.
１ 磁気ヘッド（スライダ）
２ 空気膜
３０ 磁気ディスク
1 Magnetic head (slider)
2
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| JP2003351490A JP4161868B2 (en) | 2003-10-10 | 2003-10-10 | Method for measuring natural frequency of air film of magnetic head |
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