JPS598115A - Magnetic head - Google Patents

Abstract

PURPOSE:To improve the productivity and the yield of a magnetic head, by providing cantilever-shaped parts, which face each other and are adjacent to each other, in plane plate-shaped magnetic materials which should become a head core and subjecting facing parts of these cantilever-shaped parts to laser welding. CONSTITUTION:Cantilever-shaped parts 13a and 13b which face each other and are adjacent to each other are formed in parts of two adjacent plane plate- shaped magnetic materials 15a and 15b, and facing parts of these cantilever- shaped parts 13a and 13b are subjected to laser welding, thereby forming a magnetic head. When the same process as the glass joining process of a ferrite head is used to mold glass near a front gap face 10, the front gap is stabilized for a long time. In this case, since no thermal residual stress is generated in the junction part due to laser welding, the junction of mold glass to the front gap face 10 is not affected by laser welding. Thus, good welding where cracks or the like are not generated is performed, and the productivity and the reliability of the magnetic head are improved considerably.

Description

[Detailed Description of the Invention] The present invention relates to a magnetic head. In recent years, as the magnetic properties of video tapes have improved, it has been desired that Sendust heads with even higher saturation magnetic flux density appear in video heads instead of conventional ferrite. .

However, since sendust is a polymetal different from ferrite, bonding a pair of core-shaped sendust with glass does not have sufficient bonding strength, and cutting methods that apply only a slight cutting force, such as a wire saw, cut the bonding strength to about 200 μm. Although it is possible to cut chips into chips with a thickness of .

On the other hand, a joining method using silver solder has also been used to join a pair of core-shaped centasts. In the case of a hiteo head, for example, a silver solder foil with a thickness of several micrometers is sandwiched between the back gap opposing surfaces of a pair of core-shaped sendust,
After 10, perform track alignment of the front gap surface,
Next, with the pair of sendust cores pressed against each other so that the silver wax foil is firmly sandwiched between the sendust cores on both sides, the silver wax foil is melted in a high-temperature vacuum and diffused into the sendust core. This is to join a pair of sendust cores. Although this method can provide sufficient bonding strength for practical purposes, the operator must be very careful in sandwiching the silver solder foil, which is several micrometers thick, between the back gap facing surfaces to prevent it from wrinkling. This work required a lot of force and nerves, and was extremely difficult to automate, resulting in extremely low productivity. Furthermore, in the above method of melting the silver solder while a pressing force is applied to the pair of sendust cores, the melted silver solder acts like a lubricant against the pressing force, and the pair of sendust cores There was a major problem in that the relative positions of the two components would shift, impairing the precision of track alignment and lowering the yield in terms of assembly precision. In addition, at the back gap surface where silver solder bonding is performed, silver solder diffuses into the sendust9, and since sendust is extremely sensitive to mixed elements and its magnetic properties deteriorate, the area near the back gap surface is The problem was that the magnetic resistance would increase.

Recently, attempts have been made to join sendust using a laser, but it has also been difficult to put joining by laser welding into practical use at a mass production level. The reason for this is that sendust is more brittle than stainless steel, etc., and cannot withstand the thermal stress during rapid cooling during laser welding, resulting in cracks in the weld. This is shown in Figures 1 and 2.
This will be explained in detail using figures. In Figure 1, (1a)
(xb) is a winding groove (2a) forming a winding window (2b
) is the core made of sendust formed, and (3)
is the back gap surface, and (4) is the front gap surface. The cores (1a) (lb) Id and the track portions provided in the front gap portions are held in a state where they are properly abutted against each other and pressed against each other by the members (5a) and (5b) of the welding jig. (5) is a laser beam,
The joint of the gap is scanned in the direction of arrow (a) and the core (la) (lb) is welded. Figure 2 is a cross-sectional view of the core after laser welding! 0,
(B) is the melted and solidified part of sendust caused by the laser beam (5), and (6) is the boundary between the melted and solidified part (B) and the base material.

Now, in FIG. 2, after the laser beam (, A) passes through the molten solidified part (E3), the volume contracts with rapid cooling, and a large thermal stress is generated in the vicinity of the boundary (6).

Since sendust is inherently brittle compared to stainless steel, etc., it cannot withstand this thermal stress, causing a large rack near the boundary (6), making it difficult to obtain good welding and resulting in extremely weak welding strength. do not have. For this reason,
Conventionally, laser welding of sendust cores was carried out by heating the sendust core to around 700°C to reduce the relative temperature difference9, which resulted in poor mass production. The present invention overcomes the above-mentioned drawbacks of the conventional method. It is an object of the present invention to provide a magnetic head that can be manufactured with high productivity and high yield.

In order to achieve the above object, a magnetic head of the present invention includes a plurality of flat magnetic materials in which at least one set of adjacent flat magnetic materials are welded to each other.
The flat magnetic materials to be welded together are provided with mutually opposing and adjacent cantilevered beam-shaped parts, and the opposing parts of the beam-shaped parts are laser welded.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 3, (7a) and (7b) are cores made of sendust, (8a) and (sb) are winding grooves forming winding windows, (9) is a back gap surface, and OQ is a front gap surface. --m---- On one surface of the core (7aX7b), a groove (lla) (Ilb) with a width of 0.2 III is formed along the longitudinal direction near the opposing adjacent surfaces of the core (7a) (7b). and width Q, 31+11
A large number of grooves (12a) (12b) are formed along the width direction at appropriate intervals in the longitudinal direction. These grooves (Ha)
(11b) (r2a) (1zb) has a depth of approximately Q, 3
In mm, these grooves (lla) (llb) (12
In a) (12b), a large number of pairs of cantilevered beam-shaped portions (13a) (13b) are formed which are adjacent to each other and opposite to each other.

At the front gap surface (+1), tracks (not shown in the figure) are formed at positions corresponding to each of the beam-shaped portions (13a) (13b) and are butted against each other. The beam-shaped portion D3a) ( The dimensions of tab) are
Considering that the diameter of the laser beam used for normal bath contact is on the order of several hundred μm, the beam diameter %, L<
is 0.15 mytt in both the longitudinal direction and the width direction of the core so that it is less than that. In addition, core (7a) (7b)
are pressed against each other by a jig not shown.

Now, in this state, the six pairs of opposing and adjacent beam-shaped parts (13a) (]ab) are brought into contact with spot a of laser light from the same direction as in FIG. In this case, in order to obtain high-quality welding with good reproducibility in the beam-shaped parts (13a) (13b) with a fine structure, it is necessary to use YA suitable for fine processing.
It is preferable to use a G laser, and it is further preferable to use a pulse-excited YAG laser, which allows the laser irradiation energy to be set accurately and with good reproducibility.

In this example as well, a pulse excitation YAG laser is used with a pulse width of 8 fFIII! Spot welding is performed by irradiating each beam shaped portion (13a) (tab) with one pulse of a 1c11 pulse of laser pulse having an energy of about IJ with zero defocus.

Figure 4 shows beam-shaped parts (13a) (13) by spot welding.
It is an enlarged sectional view showing the melt solidification part which occurs in b). Since the beam-shaped portions (13a) (13b) have a minute shape as described above, their heat capacity is small, and when exposed to laser irradiation, the tips of the beam-shaped portions (13a) (13b) almost completely collapse. It becomes uniformly molten. After this, the molten part enters the cooling process, but the heat conduction into the core (7a) (7b) is
Since the thermal conduction resistance is higher than in the conventional case explained using Fig. 2, the beam-shaped portion (
13a) (13b), and during this cooling process, the uniform surface in the beam-shaped part (13a) (tab) becomes almost a plane, and in fact, the boundary between the melted and solidified parts Line CI4 becomes a substantially horizontal straight line.

Therefore, the thermal contraction of the molten solidified part during this cooling process occurs in the direction of the arrow (c), but the beam-shaped part (taaXtab
) is completely free from shrinkage in the direction of arrow (c), so no thermal stress is generated, and therefore good welding without cracks can be obtained.

In this way, six pairs of beam-shaped parts (13a) (13b
) are all spot welded, and then grooves (12a) (
1zb> to obtain a head chip with a thickness of Q, j 5 mlN.

At this time, multiple cuts were made using a peripheral cutter having an outer diameter of 50 mm, a rotational speed of 3000 rpm, and a thickness of 0.25 nm, but the welded portion did not suffer any damage. of course,
No problems occurred with ultrasonic cleaning.

The head chip thus obtained is shown in FIG.

As described above, the structure of the magnetic head is such that mutually opposing and adjacent beam-shaped portions (13a) (13b) are formed in part of two adjacent flat magnetic materials (15a) (lsb). It has a structure in which opposing parts of the beam-shaped parts (13a) and (13b) are laser welded. Incidentally, glass may be molded near the front gap 1fiQO using the same process as the glass bonding process of the ferrite head.In this way, the front gap can be stabilized for a long period of time, which is very effective in practice. 0 in this case,
The weak bonding strength of the glass is already due to the beam shape part (13a)
There is no problem because sufficient strength is obtained by welding the front gap surface (tab), and as mentioned above, there is no thermal residual stress in the laser welded joint.
The bonding of the molded glasses in No. 1 is not affected by laser welding at all.

FIG. 6 shows another embodiment, in which the notch (16a) (
16b) After glass-bonding a core made of Sendust with K-corresponding grooves formed in it in the same way as in the case of ferrite,
A chip aη having a predetermined size and shape is obtained by cutting with a wire saw, and then a laser beam (q) is used to bathe the opposing surfaces of the opposing and adjacent beam-shaped portions (18a) and (18b).Thermal stress Although it seems to be quite disadvantageous compared to the first embodiment in terms of this, since the welded part has a minute beam shape, the cooling rate of the welded part after laser welding is slower than in the conventional method. Therefore, burn cracks do not occur and good welding is performed.Also, the beam shape part (18aX
1sb) is indicated by the arrow in the cooling process after welding) (e)
The magnetic material tends to contract in this direction, and the thermal stress generated thereby acts to attract the flat magnetic materials (19a) and (19b) to each other, which has the effect of strongly forming a front gap and a back gap.

In addition, in this embodiment, the pace on which the magnetic head is fixed is
It becomes possible to weld the tip θ at the same time as welding the beam-shaped portions (18a) and (18b).

FIG. 7 shows yet another embodiment. In this embodiment, the magnetic head is made by laminating a plurality of flat magnetic material sheets υ made of thin plates, and the beam-shaped portion of each flat magnetic material @0 is stacked. (2
), adjacent t's are welded to each other by laser light and the whole is fixed as one body. In the first and second embodiments, the opposing surfaces of the beam-shaped portions (13M) (13b) S or (18a) (18b) constituted a part of the back gap surface (9). In the embodiment, it is a part of the flat surface of the flat magnetic material υ.

Note that the flat magnetic material (15a) (15b), (tea)
(1sb), but it is particularly effective when using brittle materials such as sendust.

As explained above, according to the magnetic head according to the present invention, by laser welding the beam-shaped portion, it is possible to perform good welding without generation of P1 cracks, and therefore productivity and reliability can be greatly improved. obtain.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating a conventional method of manufacturing a magnetic head, FIG. 2 is a sectional view illustrating a molten and solidified portion of a conventional magnetic head formed by laser welding, and FIGS. 3 is a perspective view illustrating the manufacturing method of the magnetic head, FIG. 4 is a sectional view illustrating the melted and solidified part by laser welding, and FIG. 5 is a perspective view of the magnetic head, and j
Figure g7 is a perspective view of a magnetic head in another embodiment. (9)... Back gap surface, aO... Front gap surface, (taa) (13b) (tea) (tab)
tn--Beam shaped part, (15a) (15b) (19
a) (19b) (2L = flat magnetic material, Foundation)...
・Pace Figure 1 Figure 2 Figure 5 Figure 4

Claims (1)

[Scope of Claims] 1. In a magnetic head composed of a plurality of flat magnetic materials in which at least one set of adjacent flat magnetic materials are welded to each other, the flat magnetic materials to be welded to each other are A magnetic head in which adjacent cantilevered beam-shaped parts are provided, and opposing parts of the beam-shaped parts are laser welded. 2. The magnetic head according to claim 1, wherein the material of the flat magnetic material is Sendust. 3. The magnetic head according to claim 1, wherein the beam-shaped portion is welded to the pace to which the magnetic head is fixed. 4. A back gap part and a front gap part in which a track part having a predetermined width is formed, the opposing surfaces of the beam-shaped part form a part of the back gap surface, and the front gap part is provided with glass. The magnetic head according to claim 1, wherein the magnetic head is molded. 5. The flat magnetic material is a thin plate, and a plurality of the flat magnetic materials are laminated, and the adjacent flat magnetic materials are fixed to each other by welding the beam-shaped portions, as described in claim 1. magnetic head.