KR950001663B1 - Glass solders using magnetic head - Google Patents

Abstract

The soldering glass compsn. for magnetic head comprises 47-57 wt.% of PbO, 24-32 wt.% of SiO2, 5-9 wt.% of B2O3 4-8 wt.% of ZnO, 0-9 wt.% of the mixt. of Na2O and K2O, and 0-4 wt.% of Al2O3. The obtd. soldering glass compsn. is useful in melt-sticking mechanically at high temp. of two parts of ferrite single crystalline in the producing process of VTR magnetic head. The process is useful for preventing crack of glass and reducing of output power, and giving improved chemical resistance and wear resistance, then gives the excellent magnetic head.

Description

Laminated Glass Composition for Magnetic Head

1 and 2 show the manufacturing process of the VTR magnetic head, and FIG. 1 shows the pre-melt state of the laminated glass rod mounted on the ferrite single crystal in which the track part and the winding part are processed.

2 is a cross-sectional view showing the process of bonding the ferrite single crystal of the two parts of the laminated glass filled with the track portion and the winding portion.

* Explanation of symbols for main parts of the drawings

1: laminated glass rod 2: ferrite single crystal

3: winding part 4: track part

5: track width 6: laminated glass

7: nonmagnetic thin film 8: jig

9: bolt

The present invention relates to a laminated glass for a magnetic head that is used to mechanically fuse two parts of a ferrite single crystal at high temperature in the manufacturing process of a VTR magnetic head.

In general, the magnetic head of the VTR is manufactured through a process of processing a track part and a winding part to a Mn-Zn ferrite single crystal, and fusion and bonding the two processed ferrites into laminated glass for the magnetic head. The process will be described in detail based on FIGS. 1 and 2 as follows.

First, FIG. 1 shows a state in which a laminated glass rod is placed on a ferrite single crystal in which a track part and a winding part are processed during the manufacturing process of the VTR magnetic head. As shown in FIG. 1, the track part 4 and the winding part 3 The laminated glass rod 1 of a circular rod on the ferrite single crystal 2 which has been processed is heated so that the laminated glass melt is filled in the track portion 4 and the winding portion 3.

At this time, the excess glass protruding up to the upper planar portion of the ferrite single crystal 2 is polished and removed to coincide with the upper planar portion of the ferrite single crystal 2, and then the polishing is continued for only the winding portion 3 again. The part 3 is processed so that only a little glass remains.

Next, the non-magnetic thin film 7 is coated on the polished surface by sputtering SiO ₂ or Al ₂ O ₃ to a predetermined thickness to form a magnetic head gap.

The ferrite single crystal 2, which has been coated with the nonmagnetic thin film 7, has been processed into two ferrites as shown in FIG. 2 for bonding to the other ferrite single crystal 2 'filled with glass by processing only the track portion 4; When the single crystal (2) (2 ') is bitten by the jig (8) and pressurized with the bolt (9) and heated and fused together, an intermediate product (GB Bar: Glass Bonded Bar) of the magnetic head is obtained.

Subsequently, the intermediate product is cut diagonally to manufacture the magnetic head chip core.

When the fusion bonding of ferrite is performed by using laminated glass in the manufacturing process of the VTR magnetic head as described above, the most important matter is mismatch of thermal expansion coefficient between laminated glass and ferrite.

That is, when the thermal expansion coefficient of the laminated glass is significantly different from the thermal expansion coefficient of the ferrite, there is a problem in that the permeability of the ferrite is reduced due to the residual stress remaining in the magnetic head after bonding, or the glass is cracked and broken.

In consideration of these considerations, in the case of manufacturing a conventional VTR magnetic head, the coefficient of thermal expansion of glass is selected to be 90 to 115 × 10 ⁻⁷ / ° C. (30 ° C. to 350 ° C.) which is slightly lower than ferrite within the range that the output of the magnetic head does not drop. After bonding, the compressive stress is applied to the glass to increase the bonding strength.

Another problem that occurs during fusion is a chemical reaction that occurs at the boundary between ferrite and glass at high temperatures, and the reaction layer resulting from this chemical reaction creates stress on the ferrite and particularly erodes the gap. As a result, the effective track width 5 of FIG. 1 becomes smaller than the actual width, resulting in a problem of decreasing the output of the magnetic head and increasing the rubbing noise.

At this time, the reaction layer produced as a result of the chemical reaction is different depending on the composition of the laminated glass, but is usually glassy.

However, in some cases, crystallization may occur during cooling or heat treatment to cause cracks.

On the other hand, bubbles generated inside the glass during fusion also have a great influence on the characteristics of the magnetic head, and in particular, bubbles or cracks generated in the gap portion are adsorbed by ferrite powder during processing or magnetic powder is adsorbed during operation, thereby decreasing the output of the magnetic head. Increase sliding noise.

In addition, since bubbles or cracks generated inside the glass damage the tape and shorten the life of the tape, the occurrence of such bubbles or cracks should be suppressed as much as possible.

In addition, the hardness or abrasion resistance of the glass also affects the life and performance of the magnetic head. The magnetic tape passing through the front of the magnetic head at high speed is designed to generate turbulent air flow so as not to contact the head. Wear due to contact should be considered.

The wear rate of the glass and the ferrite forming the gap is preferably the same, but when the effective track width of the magnetic head is changed due to the differential wear, the output of the magnetic head is decreased and the sliding noise is increased.

In view of these considerations, the hardness of laminated glass is generally lower than that of ferrite, so it is required to select a glass composition to increase the hardness.

Next, there may be a problem of chemical resistance of the glass, because the erosion of the glass may be caused by the cleaning solution during the cleaning process several times during the manufacturing process of the magnetic head.

Therefore, the laminated glass should be excellent in chemical resistance to the cleaning solution, it should also be used to control the composition of the glass corresponding to the type of cleaning solution.

Finally, there is a problem of securing the working temperature. In general, in the case of low melting glass, the working temperature may be lowered, but chemical resistance and abrasion resistance (hardness) are inferior, and in the case of high melting glass, the reaction layer is likely to be generated. Adequate adjustments should be made to ensure proper working temperatures.

As described above, when selecting a laminated glass composition, a composition capable of simultaneously satisfying the various characteristics described above is required. Among the currently used laminated glass for VTR magnetic heads, various characteristics of the above-described bars are simultaneously applied. It does not satisfy one or two characteristics such as satisfactory but poor wear resistance.

Accordingly, an object of the present invention is to provide a new laminated glass composition capable of simultaneously satisfying all the characteristics required for laminated glass for a VTR magnetic head.

The laminated glass for the VTR magnetic head of the present invention is a lead silicate-based glass, whose composition is 47 to 59 wt% of PbO, 34 to 41 wt% of SiO _{2 as} main components, and ₄ to 8 wt% of ZnO as alkaline earth metal. Na ₂ O and K ₂ O are each contained 0 to 6 wt%, and ZrO ₂ and Al ₂ O ₃ are each contained 0 to ₄ wt%.

The reason for component limitation of the laminated glass composition for a magnetic head of the present invention will be described in detail as follows.

First, PbO and SiO ₂ , which are main components, are closely related to each other. If PbO is less than 47 wt% and SiO ₂ is more than 41 wt%, the chemical resistance and abrasion resistance are increased, but the transition point of glass is 450 ℃ due to the high viscosity of glass. The softening point of the glass becomes more than 500 ° C. and the working temperature becomes too high, resulting in a severe reaction between the ferrite and the glass. Conversely, if PbO is less than 59wt% SiO ₂ is 41wt% is greater than we viscosity of the low working temperature, but can be lowered, danghamyeo resistant, easy to erosion wear off of his head machining alkaline and acid solutions, glass Vickers (Vicker's) since the hardness to be easily worn away to less than 350kg / ㎟ content of PbO and SiO ₂ is not to be 47~59wt%, 30~41wt%, respectively.

Next, Zn, one of the main components of Mn-Zn ferrite, is easy to diffuse into glass because its atomic size is smaller than that of Mn or Fe, and accelerates the reaction with glass during fusion with glass. Therefore, the content of ZnO in the glass is 4 to 8 wt% to lower the ZnO solubility of the ferrite into the glass, thereby suppressing the ferrite dissolution due to chemical reaction at the high temperature. At this time, less than 4wt% has little effect, and at 8wt% or more, devitrification easily occurs during fusion. Therefore, the ZnO content is preferably maintained at 4-8wt%.

On the other hand, if the alkali component Na ₂ O or K ₂ O in the glass is too small, the flowability of the glass is bad because the chemical reaction occurs badly to increase the fusion temperature or long time.

On the contrary, if the content of these components is too high, the chemical resistance becomes poor, and since these alkali components also have a direct proportional relationship with the coefficient of thermal expansion, the amount of alkali should be adjusted to control the coefficient of thermal expansion. When chemical resistance is not required greatly during the processing, it is preferable to adjust Na ₂ O or K ₂ O to ₃ to 6 wt%, 0 to 3 wt%, or 0 to 3 wt% and 3 to 6 wt%, respectively. In this case, it is easy to adjust hardness and coefficient of thermal expansion and to suppress the reaction with ferrite during fusion. However, when a lot of acid and alkali solution are used during processing, chemical resistance is greatly required, so Na ₂ O or K ₂ O The wt% difference is adjusted to about 20% so that the combined amount of Na ₂ O and K ₂ O is ₄ to 8 wt%. In other words, as the content ratio of Na ₂ O or K ₂ O is similar, the chemical resistance is improved.

Next, when the wear resistance is particularly required or the chemical resistance needs to be improved, but the alkali content cannot be reduced due to the thermal expansion coefficient adjustment, a small amount of ZrO ₂ or Al ₂ O ₃ may be added to improve the properties. If more than 4wt% of ZrO ₂ or Al ₂ O ₃ is added or put together, the high temperature viscosity of the glass increases, which increases the working temperature and the fusion time, so the maximum content of these components should be limited to 4wt%.

The physical properties of the laminated glass of the present invention having the composition described above have a transition point of glass of 400 to 450 ° C., a softening point of 450 to 500 ° C., Vickers hardness of 450 to 500 kg / mm 2, a thermal expansion coefficient of 90 to 115 × 10 ⁻⁷ , and a working temperature of 700 to When the magnetic head is manufactured using this method, the glass crack or output decrease due to the difference of thermal expansion coefficient, the output decrease caused by the reduction of effective track width due to chemical reaction, problems due to bubble formation, chemical resistance, It is possible to manufacture a high-quality magnetic head with high reliability, in which various problems such as wear resistance are eliminated.

Claims (1)

Weight% 47≤PbO≤57, 24≤SiO ₂ ≤32, 5≤B ₂ O ₃ ≤9, 4≤ZnO≤8, O <Na ₂ O + K ₂ O≤9 and O≤Al ₂ O ₃ ≤ Laminated glass composition for a magnetic head comprising the composition of 4.