JPH0725569B2 - Low temperature fusible glass composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low-temperature fusible glass composition which is used as a material for filling voids of a magnetic head and which can be fusion-bonded at a relatively low temperature. Is.

[Conventional technology]

In recent years, a magnetic recording / reproducing apparatus such as a video tape recorder is required to have a high-density recording / reproducing function, and accordingly, a magnetic head capable of performing high-density recording / reproducing is also required. Therefore, a magnetic head using a core in which a thin film made of an alloy magnetic material having a high magnetic permeability and a high saturation magnetic flux density is formed on a gap facing surface of a block made of an oxide magnetic material having a high magnetic permeability is used. It has become to.

Conventionally, in the above core, a pair of blocks are integrated by fusing glass through a thin film, and as the glass, a low melting point glass containing lead as a main component is usually used.

[Problems to be Solved by the Invention]

However, in the magnetic head using the conventional low melting point glass, there is a problem that a reaction called nucleation occurs at the interface between the low melting point glass and the alloy magnetic material, and further, a portion where the magnetism is lost is generated in the alloy magnetic material. have.

In the low melting point glass containing lead as a main component, oxygen is generated by the following reaction.

It is considered that the PbO ₂ → PbO + (O) alloy magnetic material undergoes nucleation by being oxidized by the generated oxygen, and as a result, the oxidized portion becomes nonmagnetic. Further, in the low-melting-point glass, cracking and chipping occur at the above-mentioned nucleation-caused portion, resulting in a decrease in the yield of the magnetic head.

Further, the above low-melting glass generally has low hardness, and for example, there are few low-melting glasses that can be fused at 500 ° C. and have Vickers hardness of 300 or more. Therefore, in the conventional magnetic head, the fused glass portion tends to be worn earlier than the core made of a magnetic material. However, on the contrary, in the case of a glass having a high hardness, the viscosity becomes large and the flow of the glass at the time of welding deteriorates.

Further, in the case of a magnetic head formed with an alloy magnetic thin film, if the thermal expansion coefficients of the oxide magnetic material and the low melting point glass are significantly different, internal stress occurs between the alloy magnetic thin film and the low melting point glass, Cracks also occur in the low melting point glass and further in the alloy magnetic thin film.

In general, many low-melting glasses contain oxides of alkali metals such as Na ₂ O and often have poor water resistance.

[Means for Solving the Problems]

In order to solve the above problems, the low-temperature fusible glass composition according to the present invention has a SiO ₂ content of 5 to 8 wt%, a PbO content of 60 to 65 wt%, an Al ₂ O ₃ content of 1 to 2 wt%, and a B ₂ O ₃ content. 7 to 10 weight%, Tl ₂ O5~1
2% by weight and Bi ₂ O ₃ 12 to 15% by weight, and is characterized in that the coefficient of thermal expansion matches the coefficient of the oxide magnetic material.

[Work]

According to the above configuration, the low-temperature fusible glass composition has a relatively small amount of lead oxide that causes nucleation, and by adding Bi ₂ O ₃ instead, nucleation is suppressed. As a result, the occurrence of loss of magnetism in the alloy magnetic material of the magnetic head is reduced. Further, the reduction of nucleation can reduce cracking and chipping of the glass composition. Also, Bi
_{Since it} contains a relatively large amount of ₂ O ₃ and Tl ₂ O, the viscosity is considerably low, and the glass easily flows during welding.

In addition, since the glass composition does not contain an alkali metal or the like and contains Al ₂ O ₃ , the glass composition has excellent water resistance and further excellent wear resistance.

Further, by making the coefficient of thermal expansion of the glass composition substantially equal to that of the oxide magnetic material, the internal stress between the alloy magnetic material and the glass becomes small, and the occurrence of glass cracks can be suppressed.

〔Example〕

 An embodiment of the present invention will be described below.

SiO ₂ , PbO, Al ₂ O ₃ , B ₂ O ₃ , Tl ₂ O and Bi ₂ O ₃ were sampled in fixed amounts in accordance with the composition shown in Table 1, and were collected in a platinum crucible at a temperature of 1200 ° C for 1 to 2 Sample 1 was prepared by melting and mixing for a period of time.

The physical properties of the obtained glass composition of Sample 1 were measured, and the results are also shown in Table 1.

As described above, the yield point of the obtained glass composition is 350 ° C.
Since the viscosity becomes considerably lower, the glass easily flows even at a working temperature of 480 ° C. in the magnetic head manufacturing process, and welding is possible. Furthermore, this glass composition has a Vickers hardness of 390 and is excellent in abrasion resistance.

Further, when the thermal expansion coefficient of the glass composition is made to substantially match the thermal expansion coefficient 120 of the oxide magnetic material, such as ferrite, when welding is performed at 480 ° C., the internal stress between the alloy magnetic material and the glass is increased. Can be reduced, and the occurrence of glass cracks can be suppressed.

〔The invention's effect〕

The low fusion glass composition according to the present invention, as described above,
SiO ₂ 5 to 8 wt%, PbO60~65 wt%, Al ₂ O ₃ 1~2 wt%, B ₂ O ₃ 7~10 wt%, Tl ₂ O5~12 wt%, Bi ₂ O ₃ 12~1
It is composed of 5% by weight.

Therefore, the low-temperature fusible glass composition suppresses nucleation in a magnetic head having an alloy magnetic thin film,
The occurrence of loss of magnetism in the alloy magnetic material of the magnetic head is reduced. Further, the reduction of nucleation can reduce the glass cracking in the magnetic head.
As a result, it is possible to significantly reduce the yield in manufacturing the magnetic head.

Further, since the low-temperature fusible glass composition contains a relatively large amount of B ₂ O ₃ and Tl ₂ O, the yield point is 350 ° C. or lower, that is, the viscosity becomes low, and it easily flows even at a temperature of about 480 ° C.,
Welding becomes possible. In addition, it does not contain alkali metals,
In addition, since it contains Al ₂ O ₃ , it is also excellent in water resistance. Further, this type of glass has a Vickers hardness of 350 or more and is excellent in abrasion resistance.

Further, by making the coefficient of thermal expansion of the glass composition substantially the same as that of the oxide magnetic material, the internal stress between the alloy magnetic material and the glass is reduced, and the occurrence of glass cracks can be suppressed. There is also an effect that the yield at the time of manufacturing can be improved.

Claims (1)

[Claims] 1. SiO ₂ 5 to 8% by weight, PbO 60 to 65% by weight, Al ₂
O ₃ 1 to 2 wt%, B ₂ O ₃ 7~10 wt%, Tl ₂ O5~12 wt%, Bi ₂ O ₃ low temperature fusible glass composition comprising 12-15 wt%.