JPS61101432A - Bonding glass for magnetic head - Google Patents

Abstract

PURPOSE:The titled glass constituting easily a nonmagnetic gap part of magnetic head, obtained by blending a glass-forming oxide containing specific amounts of SiO2, B2O3, and Al2O3 with a modified oxide containing specific amounts of PbO, Na2O, K2O, and Sb2O3 in a specific ratio. CONSTITUTION:Glass comprising 35-45wt% glass-forming oxide part containing 25-35wt% SiO2, 0-7wt% B2O3, and 0-6wt% Al2O3 and 55-65wt% modified oxide containing 52-68wt% 0-5wt% Na2O, 0-5wt% K2O, and 0-1wt% Sb2O3, and 100wt% total amounts of both the oxides, is prepared. The glass has 550-580 deg.C softening point, 435-455 deg.C annealing point, 85-92(X10<-7>deg<-1>) coeffi cient of thermal expansion, constitutes easily nonmagnetic gap part of magnetic head made of Mn-Zn system ferrite, and it has improved corrosion resistance, water resistance, and wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bonding glass for a magnetic head made of Mn--Zn ferrite.

(Prior art) Conventional magnetic heads are composed of Ni, Zn-based ferrite [
However, due to the demand for higher density magnetic recording, Mn-Zn system 7
The demand for industrial light and mechanical heads has been increasing.

The non-magnetic gap in these magnetic heads is constructed by heating and melting glass to a considerably high temperature above its softening point, pouring it into the gap in the ferrite core, and then cooling it to fuse the ferrite and glass. Ru.

(Problem to be solved by the invention) When ferrite and glass are heated to the working temperature range of glass and then cooled down, the difference in thermal expansion between ferrite and glass occurs because the viscosity of glass is low at the beginning of cooling. The stress caused by this is immediately relaxed by the glass, but as the temperature drops and the viscosity of the glass increases, it takes time to relax the stress, so the stress begins to rise and the viscosity increases to 1014·'poise (strain). When the stress increases to about point), the viscous flow of the glass is not actually stable, so the stress accumulates without being alleviated. Glass cracks occur when the residual stress at room temperature exceeds a certain limit. It is near the annealing point (10''-'poise) that the ferrite and glass substantially adhere and stress begins to occur, and this temperature is hereinafter referred to as the fixation temperature.

Figure 1 shows the fixing temperature required for fusion bonding of ferrite and glass, the number of thermal expansion cores of glass, and the thermal expansion coefficient αF of ferrite.
FIG. 3 is a schematic diagram showing the relationship between the

The shaded area is the range where no cracks occur. Because glass has a much stronger compressive strength than tensile strength, it is common to use glass with a coefficient of thermal expansion smaller than 7-Elite for edge fusion.

Until now, many defective products such as glass cracks have occurred due to the characteristic that the coefficient of thermal expansion of Mn-Zn ferrite varies greatly depending on the temperature. As a countermeasure, low softening point glasses as shown in Table 1 have been used. When using low softening point glass, in the manufacturing process of magnetic head products,
Since there are restrictions on the heat treatment temperature, the development of glass with a higher softening point, appropriate viscosity, and coefficient of thermal expansion has been awaited.

Table 1 Physical properties of Corning 8463 glass The present invention:
The present invention provides a glass that satisfies the above requirements.

(Means for solving the problem) In the glass constituting the nonmagnetic gap part of the magnetic head composed of Mn-Zn ferrite, (α)SiO
l 25-35 wt% p B108 0-7 wt%.

A.J., 0. Glass-forming oxides consisting of 0-6 wt%°
(b) Pb0 52-68 wt%, N, 00-5 wt%
%.

K, O0-5wt%, sb, o, 0-1wt%
The modified oxide consists of 55 to 65 wt%, and the total of (α) and (b) is 100 wt%. In addition, its physical properties are (α) softening point 550 ~
5ao (c) (b) Annealing point 435-455 (C) (C) Strain point 410-440) (D) Coefficient of thermal expansion (30-380°C) 85-92 (x1
0'F, 7°l).

(Example) The present invention will be explained below based on test examples.

As an example of the present invention, a comparative test was conducted using six types of glasses shown in Table 2.

Table 2 Physical Properties of Glasses Used in Comparative Tests The ferrite used is Mn-Zn ferrite, and has a shape as shown in Figure 2. 1 is a grooved core, and 2 is a non-grooved core. Figure 3 shows ferrite core 1,
2 are placed facing each other, and a glass rod 3 is placed in the annular portion formed therein. FIG. 4 shows that by heating and cooling the ferrite core shown in FIG. This is a diagram of the person wearing the suit. In this test, the glass was heated in a nitrogen atmosphere continuous furnace at 780° C. for 30 minutes and then cooled, processed as shown in FIG. 5, and the crack occurrence rate was investigated for each glass.

Table 3 shows the results.

Table 3 Crack occurrence rate (100 samples) Among the glasses used in this comparative test, only Glass D had I'yln-
It was found that it is effective for fusion bonding with Zn-based ferrite. Table 4 shows the composition of Glass D.

Table 4 Composition of Glass D (wt%) In the present invention, the ranges of 5iOy and Pbo are each 2
5 to 35 wt% and 52 to 68 wt%
When iOt is less than 25% (・ is pbo more than 68wt%), the softening point decreases, the coefficient of thermal expansion increases, and the corrosion resistance, water resistance, and abrasion resistance of the glass deteriorate.
This is because if the PbO content is 35 wt% or more and PbO is 52 wt% or less, the coefficient of thermal expansion decreases and at the same time the working temperature must be raised, which makes the deterioration of the ferrite and the erosion by glass more severe, which is not preferable.

B, 0. is Nαto in the direction of suppressing the thermal expansion coefficient,
If KsO has a large effect in increasing the coefficient of thermal expansion, NαtO-KtO will sensitize water resistance and corrosion resistance when opened, so it is not desirable to be outside the scope of the claims.

! JtOs is effective in improving corrosion resistance and water resistance, but 6
% or more is not preferable because the working temperature of the glass increases.

The presence of 1% or less of Sb, O, is effective as a refining agent.

(Effects of the Invention) As detailed above, by using the glass of the present invention, it is possible to relatively easily construct the non-magnetic gap portion of the Mn-Zn ferrite magnetic head, and the low melting point shown in Table 1 can be achieved. It has significantly improved corrosion resistance, water resistance, and abrasion resistance compared to glass (Si017% or less, pbo so% or more). Also,
The incidence of cracks is also low.

[Brief explanation of the drawing]

Figure 1 is a graph in which the vertical axis is the difference α, -αF between the thermal expansion coefficient α of glass and the thermal expansion coefficient 4 of ferrite, and the horizontal axis is the fixation temperature of glass and ferrite.The shaded area is the glass and ferrite. It represents the effective range of fusion with. Figure 2 is a schematic side view of the ferrite, Figure 5 is a side view of the assembly device including the ferrite and glass rod, Figure 4 is a schematic diagram of the fused part of the ferrite core and glass, and Figure 5 is the processing of the magnetic head. This is a schematic diagram. 1... Core with groove, 2... Core without groove,
3...Glass rod, 4...Glass fusion part.

Claims (1)

[Claims] 1. In the glass constituting the non-magnetic gap portion of the magnetic head composed of Mn-Zn ferrite, SiO_
2 25-35wt%, B_2O_3 0-7wt%,
Glass-forming oxide portion consisting of 35-45 wt% Al_2O_3 0-64 wt%, PbO 52-68 wt%, Na_2O 0-5 wt%
, K_2O 0-5wt%, Sb_2O_3 0-1w
A bonding glass for an Mn--Zn ferrite magnetic head, characterized in that the modified oxide portion comprises 55 to 65 wt% of the modified oxide portion, and the total of the two oxides is 100 wt%. 2, a) Softening point 550-580 (℃) b) Annealing point 435-455 (℃) c) Strain point 410-440 (℃) D) Coefficient of thermal expansion (30-380℃) 85-92 (×1
The bonding glass for an Mn--Zn-based ferrite magnetic head according to claim 1, which has a physical property of 0^-^7 deg^-^1).