JPH07320435A - Magnetic head assembly and magnetic disk device formed by using the same - Google Patents

Abstract

PURPOSE:To obtain a magnetic head assembly which has less deformation of crown than heretofore by constituting the magnetic head assembly in such a manner that the coefft. of thermal expansion of a gimbal spring is higher than the coefft. of thermal expansion of a slider. CONSTITUTION:The magnetic head assembly is so constituted as to include the slider 10 and the gimbal spring 20 on which the slider 10 is mounted and has a coefft. of thermal expansion at 20 to 80 deg.C larger by 10 to 60% than the coefft. of thermal expansion of the slider. The materials and characteristics of the slider 10 and the spring 20 are specified in order to make the effect of the constitution more remarkable. Namely, the slider 10 is so constituted as to contain carbide alumina titanate and that the spring 20 is so constituted as to include 25 to 30% by weight cobalt, 8 to 12% by weight chromium, and 15 to 30% by weight nickel. The magnetic head assembly is so constituted that the coefft. of thermal expansion at 20 to 80 deg.C is 6.3X10<-6> to 9.1X10<-6> in addition to the constitution described above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head assembly used in a magnetic disk device.

[0002]

2. Description of the Related Art Magnetic head assemblies for hard disk drives and floppy disk drives include a slider and a gimbal spring. The slider is an extremely hard member having wear resistance. A typical material of the slider is a metal oxide sintered body such as ceramic or ferrite.
An electromagnetic conversion element that converts the magnetism on the magnetic medium into an electric signal is attached to the slider. In some cases, the slider itself also serves as a part of the electromagnetic converter. The slider is attached to the gimbal spring with an adhesive. The gimbal spring is a metal member having elasticity. A typical gimbal spring material is stainless steel. The gimbal spring elastically holds the slider on the magnetic recording medium.

The gimbal spring presses the slider onto the magnetic recording medium. Therefore, when the magnetic recording medium is stationary, the slider is in contact with the magnetic recording medium.
When the magnetic recording medium starts rotating, a levitation force is generated on the slider. The levitation force causes the slider to fly. When the magnetic recording medium is rotating, a minute gap is generated between the slider and the magnetic recording medium. When the magnetic recording medium stops rotating, the slider comes into contact with the magnetic recording medium again. Such a movement of the slider is called a contract start stop.

The shape of a general slider is shown in FIG. Referring to FIG. 8, the slider 10 is attached to the gimbal spring 20. The slider 10 is
It has air bearing surfaces 11 and 12.

Referring to FIG. 9, air bearing surfaces 11 and 12
Are formed in a slightly convex curved shape. This curved portion is called a crown. Further, the height C of the crown is hereinafter referred to as a crown amount C. Here, the height C of the crown refers to the distance C between the straight line connecting the end points X and Y of the air bearing surfaces 11 and 12 and the point Z on the air bearing surfaces 11 and 12 where the distance from this straight line is the maximum. . 2mm long,
In the case of an air bearing surface with a width of 0.3 mm, the crown amount C is 0.0
It is about 5 μm. By providing the crown, it is possible to prevent the medium from sticking to the slider. Also, the crown has a function of speeding up the flying of the head. That is, the head can be quickly floated from the medium even if the medium speed is low. This helps improve the durability of the medium. Further, a chamfered portion having an angle of about 30 is formed at the ends of the air bearing surfaces 11 and 12 in the disc traveling direction. The chamfer produces a levitation force on the slider.

In order to keep the operation of the magnetic recording device normal, the motion and posture of the flying slider 10 must be kept constant. The movement and attitude of the slider 10 during flying are affected by the shapes of the air bearing surfaces 11 and 12 of the slider 10. In order to keep the movement and posture of the slider 10 constant, the shape of the air bearing surfaces 11 and 12, that is, the shape of the crown must be kept constant.

By the way, it is known that the crown is largely deformed due to heat change. This crown deformation is
It can be grasped by the change of the crown amount C. The rate of change of the crown amount C due to the heat change may exceed 50%.

An example of the technique for suppressing the deformation of the crown due to heat change (hereinafter referred to as "conventional technique") is described in Japanese Utility Model Laid-Open No. 1-133362. The purpose of this prior art is to eliminate the phenomenon of deformation of the magnetic head when the magnetic head is bonded to the gimbal spring. In this case, the cause of the deformation of the magnetic head is
There is a difference in temperature before and after bonding. Incidentally, what is called a magnetic head in the prior art is a member corresponding to a slider.

In the prior art, it is estimated that the difference in the coefficient of thermal expansion between the magnetic head and the gimbal spring causes the deformation of the magnetic head. Then, by matching the thermal expansion coefficients of the magnetic head and the gimbal spring,
We are trying to prevent deformation of the magnetic head. That is, in the prior art, alumina titanate carbide (Al2O3TiC) is used as the material of the magnetic head, and 43w% Ni is used as the material of the gimbal spring. In this case, the thermal expansion coefficients of the magnetic head and the gimbal spring are 7.9 × 10 ^−6, which are almost the same.

[0010]

However, it has been clarified by experiments by the inventor that the deformation of the magnetic head cannot be prevented by the structure of the prior art. Hereinafter this experiment is referred to as Experiment 0. In Experiment 0, the slider material was alumina titanate carbide and the gimbal spring material was Ni.
42 alloy containing 42 wt% of.

Prior to the experiment, the coefficient of thermal expansion of the alumina titanate carbide was measured. The result is shown in FIG. In this measurement, the coefficient of thermal expansion was measured for 6 samples. The measurement was performed every 10 ° C. When these measurement results were averaged, the thermal expansion coefficient of alumina titanate carbide was about 5.7 × in the range of 0 ° C. to 80 ° C.
It was found to be 10 ^-6 .

On the other hand, the thermal expansion coefficient of 42 alloy is 6.0 × 1.
It was 0 ^-6. The amount of thermal expansion coefficient difference D is ((E1 / E
When defined by 2) -1) × 100, D is about 5%.
However, E1 is the coefficient of thermal expansion of the gimbal spring, E2
Is the coefficient of thermal expansion of the slider. The difference of 5% in the coefficient of thermal expansion indicates that the coefficient of thermal expansion of the slider and the coefficient of thermal expansion of the gimbal spring are substantially the same.

The results of experiment 0 are shown in the graph of FIG.

In the graph of FIG. 11, the horizontal axis represents temperature,
The vertical axis represents the crown amount C, respectively. In the figure, black circles indicate measured values when the temperature rises, and white circles indicate measured values when the temperature falls. That is, in this experiment, the temperature was 20 ° C to
After the crown amount C was measured while raising the temperature to 40 ° C., the crown amount C was measured while lowering the temperature to 20 ° C. again. One trial is made by this series of measurements. The measurements of one trial are connected by a curve. In the experiment, three trials were performed for three sliders 10 having different crown amounts C. FIG. 11 shows the results of three trials.

As a result of this experiment, the average change amount of the crown amount C per temperature change of 20 ° C. was 8 nm. In other words, the effect of preventing deformation of the crown by the configuration of the conventional technology is
Turns out not enough.

[0016]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a magnetic head assembly having less crown deformation than conventional ones. In order to achieve this object, as a result of experiments, it was discovered that when the coefficient of thermal expansion of the gimbal spring is set to be larger than that of the slider, the deformation of the crown can be prevented more effectively. This was an unexpected result in the conventional common sense.

In order to achieve the above-mentioned object based on the results of this experiment, in the following embodiments of the present invention, the thermal expansion coefficients of the slider and the gimbal spun rig are set so as to satisfy a specific relationship. That is, the thermal expansion coefficients of the two are set so that the deformation of the gimbal spring cancels the deformation of the slider. More specifically, the coefficient of thermal expansion of the gimbal spring is set to be larger than the coefficient of thermal expansion of the slider by a predetermined ratio.

In one embodiment of the present invention, the slider and the slider to which it is attached have a coefficient of thermal expansion of 20 ° C. to 80 ° C. of 10% to 6% higher than that of the slider.
A magnetic head assembly is configured to include a gimbal spring having a thermal expansion coefficient of 0%. In another embodiment of the present invention, the coefficient of thermal expansion of the gimbal spring is set to be 30% to 50% larger than that of the slider in order to make the effect of the above-mentioned configuration more remarkable. In another embodiment of the present invention, the coefficient of thermal expansion of the gimbal spring is set to be about 46% larger than that of the slider in order to make the effect of the above-mentioned configuration more remarkable.

The following embodiments of the present invention specify the materials and characteristics of the slider and the gimbal spring in order to make the effect of the above configuration more remarkable. That is, in another embodiment of the present invention, in addition to the above configuration, the slider includes alumina titanate carbide, and the gimbal spring contains 25% to 30% by weight of cobalt and 8% to 12% by weight of chromium. Weight ratio 15%
The magnetic head assembly is configured to include ˜30% nickel. In another embodiment of the present invention, in addition to the above configuration, the magnetic head assembly is such that the coefficient of thermal expansion of the gimbal spring at 20 ° C. to 80 ° C. is 6.3 × 10 ^{−6 to} 9.1 × 10 ^−6. A solid is constructed. In another embodiment of the present invention, the coefficient of thermal expansion of the gimbal spring at 20 ° C. to 50 ° C. is set to about 8.3 × 10 ⁻⁶ in order to make the effect of the above configuration more remarkable.

In the next embodiment of the present invention, in view of the fact that the deformation of the crown becomes a problem, the above configuration is applied to the slider having the crown formed on the air bearing surface. That is, according to another embodiment of the present invention, a slider having a crown formed on the air bearing surface and a gimbal spring having a thermal expansion coefficient larger than the thermal expansion coefficient of the slider by 10% to 60% are attached to the slider. To include,
A magnetic head assembly is constructed.

In the following embodiments of the present invention, a method for forming a crown is specified in addition to the above-mentioned constitution. This is because a problem at the time of crown formation is presumed as one of the causes of slider deformation. That is, in another embodiment of the present invention, a first step of pressing the lower surface of the material member against the concave curved surface of the jig having a concave curved surface and bonding the concave curved surface of the jig to the lower surface of the material member, The slider in which the crown is formed by the second step of forming the upper surface of the material member into a flat shape and the third step of removing the material member from the jig is applied to the above configuration.

The following embodiments of the present invention show a structure in which the above configuration is applied to a magnetic disk device. That is, according to another embodiment of the present invention, a hard disk device includes a slider and a gimbal spring to which the slider is attached and which has a coefficient of thermal expansion that is 10% to 60% higher than the coefficient of thermal expansion of the slider. Composed. According to an embodiment of the present invention, a hard disk device includes a magnetic head and a metal elastic member to which the magnetic head is attached and which has a coefficient of thermal expansion greater than that of the magnetic head by 30% to 50%. Composed.

[0023]

An embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, the magnetic head assembly of the present invention includes a slider 10 and a gimbal spring 20.

The slider 10 has the same structure as that shown in FIG. The outer diameter of the slider 10 is about 2 mm in length, about 1.5 mm in width, and about 0.5 nm in height. The crown amount C is 50 μm. The material of the slider 10 is alumina titanate carbide. Alumina titanate carbide is a hard ceramic.

The thermal expansion coefficient of alumina titanate carbide at 25 ° C. to 900 ° C. is nominally 7.9 × 10 ^-6 . However, in the measurement performed in Experiment 0, the coefficient of thermal expansion of the slider 10 of the present embodiment is 20 ° C.
In the range of 80 ° C., it was about 5.7 × 10 ⁻⁶ .

The gimbal spring 20 has an outer diameter of about 5 mm in length, about 1.0 mm in width and about 0.05 mm in thickness. The gimbal spring 20 is made of a CoCrNi-based spring material. More specifically, the gimbal spring 20 contains 20 to 30 wt% cobalt and 8 to 12 chromium.
It is a metal mainly composed of wt% and nickel 15 to 30 wt%. The other compositions that make up the gimbal spring 20 are primarily iron. A product called Spron # 200 manufactured by Seiko Electronic Components Co., Ltd. is a constant elasticity alloy satisfying the above composition. In a comparative experiment described below, Spron # 200 was used as the material for the gimbal spring 20.

The coefficient of thermal expansion of the gimbal spring 20 at 20 ° C. to 80 ° C. is about 8.3 × 10 ^-6 . Therefore, the difference in coefficient of thermal expansion between the slider 10 and the gimbal spring 20 was about 46%. For reference, 0 ℃ to 5
The coefficient of thermal expansion of the gimbal spring 20 at 0 ° C is
It was 7.3 × 10 ⁻⁶ .

The slider 10 is bonded to the gimbal spring 20 with an adhesive. An epoxy thermosetting adhesive was used as the adhesive. Specifically, Hisol EA9430 manufactured by Toray Industries, Inc. was used.

The crowns of the air bearing surfaces 11 and 12 of the slider 10 were formed by the following method.

Referring to FIG. 2 (a), a jig 40 having an upper surface 41 formed into a concave curved surface is used. Also, the member 30
Consists of alumina titanate carbide. After processing, the member 30 becomes the slider 10.

Referring to FIG. 2B, in the first step, the lower surface of the member 30 is bonded to the upper surface 41 of the jig 40 with the adhesive 42. The member 30 is curved by being bonded to the curved upper surface 41. There is stress in the curved member 30.

Referring to FIG. 3A, in the second step, the upper surface 31 of the member 30 is flattened.

Referring to FIG. 3B, the member 30 is removed from the jig 40 in the third step. At this time, the stress inside the member 30 is released. Thereby, the curvature of the lower surface of the member 30 is eliminated. On the other hand, along with this, the upper surface of the member 30 is curved. This curve becomes the crown.

Next, referring to FIGS. 4 to 6 and FIG.
The result of the comparative experiment for verifying the effect of the present embodiment will be described.

In this experiment, the crown amount C of the slider 10 is
The temperature change is measured. The experiment was performed on three gimbal springs 20 having different thermal expansion coefficients.

The experimental method is the same as in the case of the experiment shown in FIG. That is, the crown amount C is measured while raising the temperature from 20 ° C to 40 ° C, and then the temperature is set to 2 again.
The crown amount C was measured while the temperature was lowered to 0 ° C. This series of measurements constitutes one trial. In the experiment, one trial was performed for each of the plurality of sliders 10 having different crown amounts C.

The results of the experiment are shown in FIGS. 4-6 and FIG. In each figure, the horizontal axis indicates the temperature and the vertical axis indicates the crown amount C. In the figure, the black circles indicate the measured values when the temperature rises, and the white circles indicate the measured values when the temperature falls.

Experimental results for the magnetic head assembly of this embodiment described above are shown in FIG. Experiment 1
Say. In Experiment 1, the difference in thermal expansion coefficient between the slider 10 and the gimbal spring 20 is 46%. Referring to FIG. 4, in this case, it can be seen that the crown amount C hardly changes in all the three trials. The average amount of change in the crown amount C obtained as a result of three trials is 2 nm.
Met.

FIG. 5 shows experimental results when the difference in thermal expansion coefficient between the slider 10 and the gimbal spring 20 is 110%. That is, the thermal expansion coefficient of the gimbal spring 20 is 12.0 × 10 ⁻⁶ . This experiment is called Experiment 2. As a material for the gimbal spring 20, Spron # 100 manufactured by Seiko Electronic Components Co., Ltd. was used. Figure 5
Referring to, it can be seen that the crown amount C greatly changes in all of the four trials. The average amount of change in the crown amount C obtained as a result of four trials was 24 nm.

FIG. 6 shows the experimental results when the difference in thermal expansion coefficient between the slider 10 and the gimbal spring 20 is 198%. That is, the thermal expansion coefficient of the gimbal spring 20 is 17.0 × 10 ⁻⁶ . This experiment is called Experiment 3. The material of the gimbal spring 20 was stainless steel. Referring to FIG. 6, it can be seen that the crown amount C greatly changes in all of the two trials. The average amount of change in the crown amount C obtained as a result of two trials was 46 nm.

Next, the analysis results of the above comparative experiment will be described with reference to the drawings.

FIG. 7 shows the average amount of change in the crown amount C obtained in Experiments 0 to 3. In FIG. 7, the horizontal axis represents the difference in thermal expansion coefficient, and the vertical axis represents the average amount of change in the crown amount C. The measurement results are indicated by black circles. The numbers attached to the black circles indicate the experiment numbers.

Referring to FIG. 7, when the results of Experiments 0 to 3 are connected by a straight line, the difference in thermal expansion coefficient is at least 10%.
It is understood that in the range R from 60% to 60%, the change in the crown amount C is smaller than in the case where the difference in thermal expansion coefficient is 5%. That is, it can be seen that by setting the difference in thermal expansion coefficient between the slider 10 and the gimbal spring 20 within the range R, the deformation of the crown can be prevented more effectively than in the conventional technique. This is a result contrary to the common general technical knowledge before the present invention, and was an unexpected result.

In order to prevent the deformation of the crown more reliably, the range of the difference in thermal expansion coefficient may be limited to the range R'of 30% to 50%. Further, in order to make the effect more remarkable, the difference in coefficient of thermal expansion may be set to about 46%.

Next, the reason why the deformation of the crown can be prevented by this embodiment will be considered. The exact reason for this is unknown. However, slider 1
It is considered that the phenomenon of 0 simple substance deformation is a strong candidate for the reason. That is, the crown is formed on the slider 10 by the manufacturing method described above. At this time, stress is generated inside the curved slider 10. This stress remains even after being separated from the jig 40. Then, as the temperature rises, the influence of this stress becomes remarkable, and the slider 1
0 is transformed. That is, even if the influence of the difference in the coefficient of thermal expansion from the gimbal spring 20 is removed, the slider 10 deforms independently. Then, by setting the thermal expansion coefficient of the gimbal spring 20 higher than that of the slider 10 by 10 to 60%, it is considered that the deformation of the slider 10 alone is eliminated. That is, it is considered that the deformation of the gimbal spring 20 cancels the deformation of the slider 10 alone.

Next, another embodiment of this embodiment will be described.

The slider 10 and the gimbal spring 20 of the present invention may be made of any material as long as the difference in the coefficient of thermal expansion is 10 to 60%, and is not limited to the materials mentioned in the above-mentioned embodiments. For example, even when calcium titanate-based ceramics is used as the material of the slider 10 and SUS304 stainless steel is used as the material of the gimbal spring 20, the same effect can be obtained.

The structure of the present invention can be applied not only to the hard disk device but also to the floppy disk device. The magnetic disk device to which the configuration of the present invention is applied can read / write information more accurately than the conventional one.

[0050]

As described above, according to the present invention, the magnetic head assembly is constructed such that the thermal expansion coefficient of the gimbal spring 20 is higher than that of the slider 10 by 10 to 60%. Further, by adopting such a configuration, the present invention can achieve an effect that the deformation of the slider 10 can be prevented more effectively than the conventional technique. As a result, the magnetic disk drive to which the magnetic head assembly of the present invention is applied can read / write information more accurately than the conventional one.

[Brief description of drawings]

FIG. 1 is a perspective view showing the outer appearance of a magnetic head assembly according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a method of manufacturing the slider 10 according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a method of manufacturing the slider 10 according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a result of an experiment for verifying the effect of the first embodiment of the present invention.

FIG. 5 is a diagram showing a result of an experiment for verifying the effect of the first embodiment of the present invention.

FIG. 6 is a diagram showing a result of an experiment for verifying the effect of the first embodiment of the present invention.

FIG. 7 is a diagram showing a result of an experiment for verifying the effect of the first embodiment of the present invention.

FIG. 8 is a view showing a structure of a slider 10.

FIG. 9 is a diagram illustrating a crown amount C.

FIG. 10 is a diagram showing the measurement results of the coefficient of thermal expansion of alumina titanate carbide.

FIG. 11 is a diagram showing a result of an experiment for verifying a temperature change of a crown amount C of a conventional technique.

[Explanation of symbols]

 10 slider 11 air bearing surface 12 air bearing surface 20 gimbal spring 30 member 31 upper surface 40 jig 41 upper surface 42 adhesive C crown amount

Claims (10)

[Claims] 1. A slider, and a gimbal spring to which the slider is adhered and which has a coefficient of thermal expansion at 20 ° C. to 80 ° C. which is 10% to 60% higher than that of the slider. Characteristic magnetic head assembly. 2. The magnetic head assembly according to claim 1, wherein the slider includes alumina titanate carbide. 3. The gimbal spring is 25% by weight.
3. The magnetic head assembly according to claim 2, wherein the magnetic head assembly contains cobalt of 30% to 30%, chromium of 8% to 12% by weight, and nickel of 15% to 30% by weight. 4. The gimbal spring of 20 ° C. to 8 °
Coefficient of thermal expansion at 0 ° C. is 6.3 × 10 ^{−6 to} 9.1 ×
The magnetic head assembly according to claim 3, wherein the magnetic head assembly has a size of 10 ^-6 . 5. The magnetic head assembly according to claim 1, wherein a crown is formed on an air bearing surface of the slider. 6. The crown of the slider presses a lower surface of a material member against the concave curved surface of a jig partially having a concave curved surface to bond the concave curved surface of the jig and the lower surface of the material member. It is formed by a first step, a second step of forming the upper surface of the material member into a planar shape, and a third step of removing the material member from the jig. Item 6. A magnetic head assembly according to item 5. 7. A hard disk drive including a slider and a gimbal spring to which the slider is attached and which has a coefficient of thermal expansion that is 10% to 60% greater than the coefficient of thermal expansion of the slider. 8. A floppy disk device comprising a magnetic head and a metal elastic member to which the magnetic head is attached and which has a coefficient of thermal expansion greater than that of the magnetic head by 10% to 60%. 9. The magnetic head assembly according to claim 1, wherein the adhesive for adhering the slider and the gimbal spring is an epoxy adhesive. 10. The magnetic head assembly according to claim 9, wherein the adhesive is a thermosetting adhesive.