JPS6145285B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a gap in a magnetic head, and more particularly to a method for forming a gap using so-called glass bonding, which can form a narrow gap length as set. A common method for manufacturing ferrite magnetic heads for computers, VTRs, audio, etc. is to form them into a predetermined shape, mirror polish them, then melt the glass material and use capillary action to fill the gap in the gap. It is. This glass bonding method has an excellent feature that, for example, by selecting an appropriate glass material, good adhesive strength can be obtained between the ferrite material that makes up the head core and the glass material, allowing the production of a sufficiently strong head. . Moreover, this strong adhesion also results in the effective gap length becoming wider than the set value due to the progress of the reaction between the ferrite material and the molten glass material. In other words, the optical gap and the magnetic gap do not match, and the latter has a large value, and even if a gap is formed with a 1 μm spacer, it is substantially 1.1 to 1.4 μm, resulting in large variations in accuracy. The widening of the gap described above is thought to be due to the process-affected layer. In other words, the commonly used polishing method for ferrite is lapping using fine diamond powder, and this process generates a process-altered layer, which exists as an amorphous phase with a thickness of 0.05 to 0.2 μm, and is difficult to scratch. The thickness is not constant because it is an accumulation of Therefore, when the processed ferrite is glass bonded while facing each other, the corrosive effect between the glass and the ferrite increases as the processing strain is large, and decreases as the process strain is close to zero. However, in the past, there was no method for measuring this process-affected layer, and the condition of the processed surface of the ferrite, the degree of distortion, and the state of diffusion corrosion of the glass-ferrite after glass bonding were not fully understood, and the characteristics of the magnetic head of the finished product were not fully understood. The electrical conditions were individually compensated and incorporated into the magnetic recording device. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to propose a method that can form a gap length as set without enlarging a predetermined gap length. That is, in this invention, the thickness d of the process-affected layer of ferrite is measured, and for a predetermined gap length g, g
This is a method for forming a gap in a magnetic head using glass bonding using a -2D spacer. Alternatively, a nonmagnetic layer of g-2d/2 may be formed on one side of the gap surface by a method such as vapor deposition or sputtering, and the opposite surface may be welded. In addition, the method for measuring the process-affected layer is to select a sample with a strain-free ferrite processed surface and good crystal regularity using reflected electron diffraction, and using this as a reference, obtain the complex reflection coefficient ratio of the sample using ellipsometry. This is a method for determining the thickness of the process-affected layer. The method for measuring the process-affected layer will be specifically explained below. To measure thin films using ellipsometry, a method is used to simultaneously determine the phase difference (Δ) and dichroism (R _P /R _S ) of the sample. Figure 1 shows a diagram explaining the principle of ellipsometric analysis. Based on this, the fast axis of the compensator C is tilted by π/4, the polarizer P ₁ and the analyzer A ₁ are both rotated, and the light transmitted through the analyzer is is zero, P direction θ,
The A direction ψ is measured, and the phase difference Δ of the sample Sa and the reflection coefficient ratio R _P /R _S (2
chromaticity). The phase difference and the reflection coefficient ratio are determined by the following formula, and when the reflection by the thin film sample is determined from both of them, the complex reflection coefficient ratio R _P /R _S is obtained. Δ=π/2−2θ, R _P /R _S =tanψ R _P /R _S =(R _P /R _S )exp(iΔ) In addition, Fig. 2 shows an explanatory diagram of reflection in a thin film.
Assuming that the refractive index of the atmosphere n ₁ , the refractive index of the lower layer n ₃ , the refractive index of the thin film n ₂ , its thickness d ₂ , the angle of incidence on the tile φ ₁ and the measurement wavelength λ, R _P /R _S is a function of these. can be expressed. Next, the Fresnel reflection coefficient at each interface can be determined. Furthermore, from Snell's law, n ₁ sinφ ₁ = n ₂ Sinφ ₂ = n ₃ Sinφ ₃ can be obtained. Here, if n ₁ , n ₃ , λ, and φ ₁ are known and Δ and ψ are measured, the refractive index and thickness of the thin film can be obtained from the above relational expression of the complex reflection coefficient ratio. By the way, it is necessary to obtain the refractive index n ₃ of the base as a known value, and even if we process the sample so that there is no thin film and obtain n ₃ , we cannot obtain a value that can be extrapolated to zero, so we use backscattered electron diffraction. use law. In other words, in the backscattered electron diffraction method, the diffraction is attenuated by d ^-2 to ^{d -3} depending on the depth compared to the same transmission type, so the information obtained is limited to the surface information, and the information obtained is limited to the surface information. In the case of a regular polycrystalline structure, a ring-shaped diffraction spot is obtained in the diffraction image, and in the case of an irregular polycrystalline structure, a halo image is obtained. Therefore, a sample in which a ring-shaped diffraction spot is obtained in the case of a process-affected layer can be regarded as having a regular crystal structure without distortion. From this sample
It is sufficient to obtain n ₃ and apply it as a reference value to the previous ellipsometry method. Next, a method for forming the gap will be explained. Fig. 3 shows a cross-sectional view of the magnetic head, and the explanation will be based on this. First, the layer thickness d of the mirror-finishing altered layer of ferrite is measured using the above-mentioned measuring method. If the predetermined gap length is g, then On the other hand, a spacer with a dimension of g-2d is prepared, this spacer is placed in the gap part, and molten glass is poured into the gap part to form a gap. Here, the degree of diffusion corrosion between the glass and ferrite is limited to the thickness of the process-affected layer measured as described above, so if the corrosion amount 2d is subtracted from the spacer g of the predetermined gap length in advance, Even if the gap expands due to erosion, it can be formed to a predetermined gap length. That is, by using the g-2d spacer, a predetermined gap length, especially a narrow gap length, can be easily set and formed even with the glass bonding method. Examples according to the present invention will be shown below to clarify its effects. The gap length g of the magnetic head was set to 1.0 μm and glass bonding was performed using a g-2d spacer according to the method of this invention described above (numbers 1 to 3), and those using the conventional glass bonding method (numbers 4 to 6). ) was evaluated based on the gap accuracy of the finished product head. In addition, the layer thicknesses of the process-affected layers of all samples were measured using this measuring method, and compared with the thickness expanded by the gap glass. These results are shown in Table 1. As is clear from these results, it can be seen that the gap accuracy was significantly improved by the method of the present invention. Furthermore, it can be seen that in the conventional method, the accuracy decreases in proportion to the thickness of the process-affected layer measured earlier. Furthermore, the method of this invention reduces variations in accuracy and improves yield to over 90%.

[Table] As described above, the method for forming a gap in a magnetic head according to the present invention takes advantage of the mass productivity of glass bonding, and furthermore, the reproducibility of the set gap length is extremely excellent.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of polarization analysis, FIG. 2 is an explanatory diagram of the state of reflection in a thin film, and FIG. 3 is an explanatory diagram of the head gap.

Claims (1)

[Claims] 1. The thickness d of the process-affected layer on the processed surface of the magnetic head core material was determined by using backscattered electron diffraction to select a sample with no strain on the processed surface and good crystal regularity, and using this as a reference to determine the complex reflection of the sample using ellipsometry. A method for forming a gap in a magnetic head, characterized in that the coefficient ratio is obtained, the thickness of the process-affected layer is measured by a method, and glass bonding is performed using a spacer of g-2d for a predetermined gap length g. .