JPH0548242Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a magnetic head, and more specifically to a magnetic head made of sendust material.

(b) Prior art The magnetic head to which the present invention is directed, as shown in Fig. 1, has a plate-shaped magnetic core 1 made of sendust material.
a, 1b, and a non-magnetic substrate 2a, which is bonded to the outer surface of the head chip H consisting of the magnetic cores 1a, 1b.
2b, and a coil 5 wound around a rear convex portion 4 formed by a groove 3 in one magnetic core 1a. Incidentally, one example of this type of head was published in Japanese Unexamined Patent Application Publication No. 1989-
No. 2224. FIG. 2 shows a method of manufacturing such a magnetic head. In FIG. Join so that the entire surfaces match each other. In this state, as shown in C', a groove 3 is formed between the front part and the rear part, thereby forming a rear convex part 4. A coil 5 previously formed using a winding machine is attached to this convex portion 4 and soldered to a terminal 6 on the non-magnetic substrate 2. A gap spacer 7 is provided at the front part.

Next, the other magnetic core wafers 1 at the stage shown in b are stacked on top of each other as shown in d and bonded with glass to obtain a combined product 8. A notch 9 is made toward the rear, leaving a track width W at the front of the combined object 8 as shown in e. This cut 9 cuts a portion connecting the rear portions of the magnetic core wafer 1, and separates the magnetic core wafer 1.

Finally, the magnetic head is sliced along the dotted line 10 shown at e to complete the magnetic head as shown in FIG.

Sendust material (Fe-Al-Si alloy) used as the material of the magnetic core 1 has high saturation magnetic flux density, high magnetic permeability, and excellent wear resistance. On the other hand, non-magnetic substrate 2
The most commonly used material is crystallized glass, which has a thermal expansion coefficient close to that of sendust material and is highly dense. In addition, in these bonding processes, a highly heat-resistant bonding method is required, as the magnetic damage layer caused by various groove processing, polishing, etc. in the above manufacturing method is removed by heat treatment immediately before cap bonding. Bonding using fritted glass, which is most compatible with chemically bonded glass, has been proposed.

(c) Problems to be solved by the invention Generally, sendust material (Fe, Si, Al alloy)
The coefficient of thermal expansion is 175×10 ^-7 /℃ from room temperature to 600℃
It has a large temperature dependence of ~185×10 ^-7 /°C, and its temperature dependence increases (superlinear) as the temperature increases. On the other hand, for crystallized glass, which is a non-magnetic substrate, materials have been developed that are relatively similar to sendust materials, with values ranging from 150×10 ^-7 /℃ to 170×10 ^-7 /℃, but the temperature dependence of the coefficient of thermal expansion is It is constant (linear). Therefore, in order to obtain a bond with high heat resistance, if a frit glass with a high melting point is used for bonding, the difference in thermal expansion coefficient will increase as the temperature increases, and as shown in Figure 4, the difference in coefficient of thermal expansion between the magnetic core wafer 1 and the non-magnetic substrate 2 The joined body was significantly deformed, causing problems such as difficulty in forming winding grooves and gap surfaces. In order to avoid this, attempts have been made to, for example, cut the magnetic core wafer 1 into small pieces and bond them to the non-magnetic substrate 2, but this complicates the manufacturing process and does not essentially eliminate thermal strain at the bonding interface. This has caused problems such as occurrence of cracks at the bonding layer interface during processing and deterioration of the magnetic properties of the sendust material. Furthermore, the fritted glass material used has a thermal expansion coefficient (150×10 ^-7 /°C ~ 160×
10 ^-7 /℃).
In the bonding layer, compressive stress occurs at the sendust interface and tensile stress occurs at the substrate interface, and in order to alleviate these stresses, the thickness of the bonding layer needs to be 20 to 30 μm or more. In general, frit glass has less hardness and wear resistance than crystallized glass, and it causes problems such as caving between the head core and the substrate during head operation, making the contact with the recording medium unstable. was occurring.

(d) Means for solving the problem In the present invention, the composition of the sendust material forming the magnetic core is Fe-Al-Si-Ni alloy, and the composition ratio of Si is 5 to 7% by weight. use.
On the other hand, as a non-magnetic substrate, the coefficient of thermal expansion is
A crystallized glass substrate material having a temperature of 150×10 ^-7 /°C to 160×10 ^-7 /°C is used in the range of 600°C.

Then, the magnetic core and the nonmagnetic substrate are bonded together using frit glass.

(E) Effect The thermal expansion coefficients of the magnetic core material and the crystallized glass substrate are close to each other from room temperature to high temperatures (700℃), and the fritted glass used has a slightly lower coefficient of thermal expansion than the materials on both sides. Therefore, after joining, they are always in a compressed state, and moreover, they receive approximately equal stress from both sides, and are joined in a balanced state as a whole. Therefore, there is no deformation of the joined body, and the internal stress is distributed symmetrically and in a compressed state where the strength of the glass is strong, so the occurrence of cracks during processing is extremely reduced. Furthermore, the stress generated inside the bonding layer is reduced as the bonding layer becomes thinner, so the thickness is 10 μm.
Sufficient bonding strength can be obtained even with the following bonding layers. When the bonding layer has a thickness of 10 μm or less, the depression of the bonding layer during head operation is extremely small, and the state of contact with the medium is stable.

(f) Example In FIG. 3, (a) shows the thermal expansion temperature characteristics of conventional standard sendust, and (b) shows the thermal expansion temperature characteristics of sendust having a composition according to the present invention.

Commonly known as Sendust alloy
The Fe-Si-Al alloy exhibits excellent magnetic properties since it contains 9.5% by weight of Si, 5.7% by weight of Al, and the balance is Fe. On the other hand, the coefficient of thermal expansion varies depending on the composition, and research by the present inventor revealed that it is particularly influenced by the composition ratio of Si. FIG. 5 shows some of the experimental results, with the horizontal axis showing the weight percent of Si and the vertical axis showing the change in thermal expansion coefficient. The conventional Sendust material had a Si composition ratio of approximately 9.6% by weight. For this reason, in conventional magnetic heads, the thermal expansion of the magnetic core is 175 x 10 ^-7 /°C to 185 x between room temperature and 600°C.
The temperature was 10 ^-7 /℃. Figure 6 shows the change in thermal expansion from room temperature to 600°C for each Si composition ratio.
As is clear from the figure, in the region where the Si composition is 5 to 6%, the thermal expansion coefficient is 150 × 10 ^-7 / °C to 155 × 10 ^-7 /
℃, and its temperature dependence is small (linear)
material is found.

Incidentally, deviation from the composition of standard Sendust causes deterioration of magnetic properties, but by adding Ni, the deterioration of these properties becomes smaller. The decline is not a problem. In the example, an alloy containing 6% Si, 4% Al, 2 to 4% Ni, and the rest Fe was melted in a vacuum and shaped into a wafer.
A comb-shaped magnetic core wafer is formed by performing predetermined groove processing, slicing, and polishing.

Next, a SiO ₂ -Na ₂ O-B ₂ O ₃ paste having the characteristics of D in FIG. A fritted glass layer 11 having the above structure is provided as shown in FIG. 7a, and the magnetic core wafer 1' is placed on the fritted glass layer 11 as shown in FIG. 7b and bonded at a temperature of 600 DEG C. or higher. Thereafter, a magnetic head having the shape shown in FIG. 1 is obtained through the steps shown in FIG. 2c and subsequent steps.

(g) Effects of the invention According to the invention, the coefficient of thermal expansion of the magnetic core is approximately constant from 150×10 ^-7 /°C to 155 in the range from room temperature to approximately 600°C.
×10 ^-7 /℃, and by bonding a crystallized glass substrate with almost the same thermal expansion characteristics with fritted glass, which has a smaller coefficient of thermal expansion than both, there is no deformation during the manufacturing process. An excellent magnetic head without cracks or the like can be obtained. Since the frit glass bonding layer can be formed as thin as 10 μm or less, the bonded portion does not collapse when the magnetic head operates, and stable characteristics can be maintained.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a magnetic head to which the present invention is directed, and FIG. 2 is a diagram of its manufacturing process.
FIG. 3 is a diagram showing the thermal expansion characteristics of each material used in the magnetic head. FIG. 4 is a diagram showing problems in the conventional example. FIG. 5 and FIG. 6 are explanatory diagrams. FIG. 7 is a diagram showing the manufacturing process of the magnetic head of the present invention. 1, 1', 1a, 1b...magnetic core, 2, 2', 2
a, 2b...Nonmagnetic substrate, H...Head chip.

Claims (1)

[Scope of utility model registration request] A magnetic head comprising a head chip in which a pair of plate-shaped magnetic cores are joined and a magnetic gap is formed at the joined part, and a non-magnetic substrate joined to the magnetic core on both sides of the head chip, the material of the magnetic core being is a Fe-Al-Si-Ni alloy, and its
The composition ratio of Si is 5 to 7% by weight, and the nonmagnetic substrate is a crystallized glass material whose coefficient of thermal expansion is 150×10 ^-7 /℃ to 160× in the range from room temperature to 600℃.
10 ^-7 /°C, and the magnetic core and the nonmagnetic substrate are bonded together with frit glass.