JPH0347681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the thickness of a magnetic coating film on a magnetic disk medium in a magnetic disk device used as an external storage device of an information processing system.

[Conventional technology]

Conventionally, a laser beam measurement method is known as a method for measuring the film thickness of magnetic disk media, but since the optical path system of the device is complicated and expensive, the X-ray method is generally used. Since X-rays are reflected by iron components, the amount of reflection varies depending on the content of iron oxide, which is magnetic powder in the magnetic coating. Therefore, the thickness of the magnetic coating can be measured by irradiating the magnetic coating with X-rays and measuring the intensity of the X-ray calibration curve.

By the way, if the material of the magnetic coating film is different, the content of magnetic powder will also be different, and even if the film thickness is the same, the intensity of the X-ray calibration curve will be different. Therefore, a magnetic disk medium whose film thickness is known in advance is measured by the X-ray method to obtain reference data indicating the relationship between the film thickness and the intensity of the X-ray calibration curve. Based on this reference data, the film thickness value is obtained by converting the X-ray calibration curve intensity actually measured for the magnetic disk medium to be measured into film thickness. Since the same reference data cannot be used if the magnetic coating film is made of different materials, it is of course necessary to prepare reference data for each material of the magnetic coating film.

[Problem that the invention seeks to solve]

However, the intensity of the X-ray calibration curve varies not only depending on the iron component in the magnetic coating film but also on surface conditions such as surface roughness of the substrate on which the magnetic coating film is applied. Therefore, even if the thickness and material of the magnetic coating film are the same, if the surface conditions of the substrate differ, the intensity of the X-ray calibration curve will also differ. Conventionally, therefore, reference data has been created from magnetic disk media of known film thickness for each substrate with different surface conditions and for each magnetic coating film of the same material.

Therefore, during actual measurements, only magnetic disk media with the same substrate surface conditions and magnetic coating material were used.
This means that it cannot be measured. In other words, standard data must be created for each substrate surface condition and magnetic coating material, and the burden of creating standard data is heavy.

Moreover, when it comes to high-mix, low-volume boards, such as special boards with a small number of boards such as recycled boards,
Even if standard data regarding the surface conditions of the substrate and standard data regarding the magnetic coating film are obtained, the efficiency is extremely low because the number of substrates to be measured to which these standard data can be applied is small.

Even if standard data regarding magnetic coatings are obtained, the task of selecting and applying only substrates with the same surface conditions is complicated and has poor workability. Therefore, when trying to measure automatically, the surface conditions and materials of the substrates must be determined for each magnetic disk medium, which has many types of substrate surface conditions and magnetic coating materials, which is inefficient. be.

Furthermore, as in the past, a small amount of measurement error was allowed for magnetic disk media with relatively thick magnetic coatings, but recently, with extremely thin magnetic coatings of 0.5 μm or less, As a result, the tolerance for measurement errors has become extremely small, and increasingly accurate measurements are required.

The technical problem of the present invention is to solve such problems in the conventional method for measuring the thickness of magnetic coatings, to be able to accurately measure even thin magnetic coatings, and to be able to measure automatically. The purpose is to eliminate the need to judge the surface conditions of the substrate every time, so that it is suitable for

[Means for solving problems]

The technical means of the present invention taken to solve this problem is to measure the magnetic coating film of a magnetic disk medium using an X-ray beam. The relationship between the thickness and the X-ray calibration curve intensity is measured, and the reference data of the film thickness and the X-ray calibration curve intensity is obtained in advance, and the X-ray calibration curve intensity of the area without magnetic coating on the magnetic disk medium to be measured is determined. and X of the area where the magnetic coating exists
A method is adopted in which the value of the film thickness of the magnetic coating film is obtained by measuring the linear calibration curve intensity and calibrating it using the reference data. It is also possible to measure the film thickness on both sides at the same time by transmitting X-rays through the area without the magnetic coating and the area of the magnetic coating, or by performing the reflection and transmission measurements at the same time.

[Effect]

FIG. 1 is a characteristic diagram illustrating the operation of this technical means, in which 1 shows reference data and 2 and 3 show measured data. The horizontal axis is the film thickness, and the vertical axis is the X-ray calibration curve intensity. Reference data 1 is obtained by measuring a magnetic disk medium whose film thickness is known by destructive measurement or the like using an X-ray method. When at least two locations with different film thicknesses are measured, as shown in reference data 1 in the figure, the X-ray calibration curve intensity increases in proportion to the film thickness, showing a sloped characteristic. If the material of the magnetic coating film is different, the inclination angle of this reference data 1 will be different. Next, measured data 2 is related to board A, and measured data 3 is related to board B.
The material is the same as that of the magnetic coating film of reference data 1. For both substrates A and B, the X-ray calibration curve intensities A ₀ and B ₀ at locations where the film thickness is 0 μm are the This shows the calibration curve intensity. The fact that the X-ray calibration curve intensities of the portions having no magnetic coating film and indicating 0 μm are different in this way is due to the fact that substrates A and B have different surface conditions.

In the present invention, in addition to the area 4 where there is no magnetic coating as shown in FIG. 2, the portion with the magnetic coating 5 is also measured. At least two on the center side and the outer circumferential side of the magnetic disk medium
It is preferable to measure at a certain point. A ₁ is the actual measurement value of the center side a ₁ , and A ₂ is the actual measurement value of the outer peripheral side a ₂ . From the value of the X-ray calibration curve intensity A ₀ at the film thickness of 0 μm,
Line 2 parallel to reference data 1 with the same magnetic coating material
, draw a line parallel to the horizontal axis from the measured values A ₁ and A ₂ , draw a line parallel to the vertical axis from the point where it intersects the line of measured data 2, and find the point of intersection with the horizontal axis. Then, α ₁ becomes the actually measured film thickness on the inner circumferential side, and α ₂ becomes the actually measured film thickness on the outer circumferential side.

Since the magnetic coating film of substrate B is the same as that of substrate A and the substrate of reference data, the line of actual measurement data 3 also runs from point B ₀ parallel to the line of reference data 1.
By subtracting, the measured film thickness can be obtained from the X-ray calibration curve intensity. If substrate B has the same film thickness as A, then the X-ray calibration curve intensity in the magnetic coating area will be smaller by the value of the difference between the X-ray calibration curve intensities A ₀ and B ₀ in the area without the magnetic coating film. Become. As a result, the measured film thickness β ₁ obtained from the value B ₁ near the center and the substrate A
The value α ₁ is the same value, and the value near the outer periphery
The measured film thickness β ₂ obtained from B ₂ and the value α ₂ of the substrate A are the same value. That is, it can be seen that regardless of the surface conditions of the substrate, if the thickness of the magnetic coating film is the same, the actual measured value will be the same.

In other words, within a single board, the thickness and surface conditions of the board are constant in all areas, both those without and those with magnetic coating, so there is no need to determine the surface conditions of the board one by one. By measuring the area without magnetic coating and the area with magnetic coating and calibrating both data with reference data, it is possible to obtain the value of only the film thickness excluding surface condition elements from the X-ray calibration curve intensity. It is possible to measure only the film thickness without considering surface conditions.

For convenience of explanation, the film thickness is measured at two or more locations, but if the film thickness and the X-ray calibration curve intensity are known in advance, it may be at one location.

〔Example〕

Next, examples will be used to explain how the method for measuring the thickness of a magnetic coating film according to the present invention is actually implemented. FIG. 3 is a block diagram showing a measuring device for carrying out the method for measuring the thickness of a magnetic coating film according to the present invention.
A is a magnetic disk medium, and the clamp area 4 near the center hole 6 is not coated with a magnetic coating. 7 is an X-ray tube, which is connected to an X-ray generator 8. Reference numeral 9 denotes an X-ray detector which detects the amount of reflection of the X-rays irradiated from the X-ray tube 7 onto the magnetic disk medium A, that is, the intensity of the X-ray calibration curve. The X-ray detector 9 is driven by a detection power source 10, and its output is input to a pulse height analyzer 11. The measurement data from the pulse height analyzer 11 is processed by a processor 12, and the film thickness value is displayed on a display 13 or printed out by a printer 14. Numeral keys 15 are used to operate the processor 12 and input data.

In this apparatus, first, the X-ray calibration curve intensity of the clamp area 4 on which the magnetic coating film is not applied on the magnetic disk medium A is measured and inputted to the processor 12. Next, the intensity of the X-ray calibration curve at _one point a on the inner peripheral side of the magnetic coating area 5 is measured and input to the processor 12. Similarly, X at ₂ points a on the outer circumferential side of magnetic coating area 5
The calibration curve intensity is measured and input to the processor 12. Then, by comparing the reference data 1 inputted in advance to the processor 12 and the three X-ray calibration curve intensities detected by the X-ray detector 9,
Irrespective of the surface conditions of the clamp area 4, only the film thickness values at the two inner and outer locations of the magnetic coating film 5 are outputted by the display 13 and printer 14.

As mentioned above, for magnetic disk medium B, etc. whose magnetic coating material is the same as that of magnetic disk medium A, the clamp area 4 is also measured using the same method as described above, and the processor 12 calibrates it based on the reference data 1. , film thickness can be measured using the same reference data. In this case, there is no problem even if the components and surface roughness of the substrates are different as described above.

In this way, magnetic disk media with the same magnetic coating material can be calibrated using the same standard data regardless of the surface conditions of the clamp area, but only magnetic disk media with different magnetic coating materials can be calibrated using the same standard data. Separate reference data is created by destructively measuring a magnetic coating made of the same material as the medium, and calibration is performed using the reference data.

It has been known for a long time that the intensity of the X-ray calibration curve varies depending on the surface roughness of the substrate, but in the process leading up to the present invention, this tendency was found to be larger as the voltage generated by the X-ray generator is smaller. It was found that the larger the generated voltage, the less affected by surface conditions. Therefore, when measuring when the voltage generated by the X-ray generator is high, it is possible to measure only the magnetic coating, but according to the method of the present invention, highly accurate measurement is possible regardless of the voltage generated. becomes.

FIG. 4 shows a method for simultaneously measuring the film thickness on both the front and back sides of a magnetic disk medium. Conventionally, since the substrate of a magnetic disk medium is thick, the amount of reflection has been detected and measured one side at a time. That is, after measuring the thickness of the magnetic coating film on the surface, the magnetic disk medium is removed from the measuring device, turned over, reset, and measured again. Therefore, the work efficiency is poor and the operation is complicated, making it difficult to automate.

However, small magnetic disk media with thin substrates can allow X-rays to pass through them.
By using the method of the present invention that transmits X-rays and also measures the clamp area, it becomes possible to measure the film thickness on the back surface as well. The present invention measures the film thickness on the back side at the same time as on the front side.
In FIG. 4, parts that are the same as those of the device in FIG. 3 are given the same reference numerals. In this device, an X-ray detector 91 is disposed on the front side of the magnetic disk medium A, and an X-ray detector 92 is disposed on the back side. The outputs of both X-ray detectors 91 and 92 are input to the processor 12 via the pulse height analyzer 11. With this device as well, the film thickness value on the front side can be obtained by measuring both the clamp area 4 and the magnetic coating area 5 of the magnetic disk medium and calibrating with the reference data as described above. Although the amount of X-ray transmission through the substrate depends not only on the surface roughness of the substrate but also on the thickness and components of the substrate, transmission measurement of the clamp area 4 is also performed when measuring the film thickness on the back surface. Since the processor 12 subtracts the substrate thickness in the clamp area and the magnetic coating film thickness on the front side from the thickness of the magnetic coating film measured by the amount of transmission, the substrate surface condition as well as the substrate thickness can be subtracted. It is possible to obtain only the film thickness value of the magnetic coating film on the back side, regardless of the magnetic coating film or its components. In this way, by simultaneously measuring both the front and back sides of the magnetic disk medium while it is set in the measuring device, the measurement time is cut in half compared to conventional methods, and automatic measurement is also possible since there is no need to turn the magnetic disk medium over. becomes easier. In addition, the method of measuring the substrate thickness in the clamp area and subtracting it from the value of the magnetic coating thickness of the substrate and both sides of the magnetic coating area makes it possible to measure regardless of the substrate thickness. Even magnetic disk media can be easily measured by preparing only standard data regarding the material of the magnetic coating.

〔Effect of the invention〕

As described above, according to the present invention, in addition to the magnetic coating part, by measuring the X-ray calibration curve intensity of the area where the magnetic coating film is not applied, such as the clamp area, the surface roughness of the substrate and the material It is possible to obtain only the film thickness value regardless of the thickness, and no reference data regarding the substrate is required. Therefore, as long as standard data regarding the material of the magnetic coating film is obtained, even magnetic disk media using special substrates of few types can be easily and accurately measured. In particular, the film thickness on the back side can be measured in a transmission manner and simultaneously on the front side, making it extremely suitable for automatic measurement.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the operation of the method for measuring the thickness of a magnetic coating film according to the present invention, Fig. 2 is a diagram showing measurement points on a magnetic disk medium, and Fig. 3 is a block diagram of an apparatus implementing the method of the present invention. , FIG. 4 is a block diagram of an apparatus for simultaneously measuring both sides using the method of the present invention. In the figure, 1 is reference data, 2 and 3 are actually measured data, 4 is a clamp area, 5 is a magnetic coating (region), 7 is an X-ray tube, and 9, 91, and 92 are X-ray detectors, respectively.

Claims (1)

[Claims] 1 In a method of measuring the magnetic coating film of a magnetic disk medium using an Obtain reference data for the X-ray calibration curve intensity in advance, and measure the X-ray calibration curve intensity in the area where there is no magnetic coating on the magnetic disk medium to be measured and the X-ray calibration curve intensity in the area where the magnetic coating exists. A method for measuring the thickness of a magnetic coating film, characterized in that a value of the thickness of the magnetic coating film is obtained by calibrating with the reference data.