JPS5923049B2 - Insulating ceramics for high frequency circuit boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to insulating ceramics used for base stems of electron tubes, circuit boards, etc., and particularly to providing insulating ceramics with a small dielectric stack in a high frequency region.

Dielectric stacking is one of the basic characteristics when practically evaluating and evaluating the electrical properties of ceramic materials used for electron tube base stems or circuit boards. It is a quantity expressed by the product of dielectric stack ε and dielectric loss tangent [and δ, ε·tan δ, and is an important factor for evaluating the insulation properties of materials, especially in a high frequency region. The smaller the dielectric stack, the better the high-frequency O-wave insulation. Additionally, materials with larger dielectric stacks experience more power loss and, as a result, more heat generation. Therefore, it is necessary for high frequency insulating materials to have a small dielectric stack. 5. For the reasons mentioned above, a forsterite 2Mg0-SiO2 substrate, which has a small dielectric stack in the microwave region, has been used as a material for the base stem of an electron tube.

However, as electronic devices become more sophisticated, microphones and
o Electron tubes that operate at frequencies even higher than the mouth wave region, for example in the gigahertz band, are now required. However, at frequencies above the microwave range, the dielectric stacking of forsterite increases as the frequency increases. Therefore, forsterite! 5. This has the disadvantage that the insulation properties deteriorate and the output is adversely affected. The object of the present invention is to eliminate these drawbacks and provide a ceramic material with a small dielectric stack even in the frequency range higher than microwaves. ■o In order to achieve the above object, the insulating ceramic of the present invention has a content of 50% to 90% by weight.
of magnesia MgO and 30% by weight or less of silica SiO
2 and 10% to 40% by weight of alumina Al2O3 are sintered.

The present invention will be explained in detail with reference to 15 Examples below.

This three-component ceramic is manufactured by the following steps.

1 Magnesia, silica, and alumina powders are mixed in a ball mill to obtain the composition as described above.

The mixed powder of 2 was heat treated at 1300°C for 1 hour.

3. To 100 parts of the heat-treated powder, 8 parts of polyvinyl butyral as a binder and di-phthalate as a plasticizer.
- 10 parts of butyl, 1 part of sorbitan triollate as a dispersant, 8 parts of butyl alcohol as a solvent, 30 parts of methyl ethyl ketone, and 12 parts of methyl alcohol,
120 using alumina balls in a polyethylene pot.
Time ball milling.

The slurry obtained by 4-ball milling is shaped by the doctor blade method to create a raw ceramic sheet.

5 Punch out a raw ceramic sheet into a predetermined shape and hold it in the atmosphere.
Preliminary firing is performed at 300° C. for 1 hour to evaporate the binder solvent and the like.

Fifth, main firing is performed at 1550° C. for 2 hours in a hydrogen atmosphere to obtain an insulating ceramic plate.

The thus obtained ternary ceramic, namely MgO-S
For iO2-Al2O3 ceramics with different component ratios, the dielectric constant and dielectric loss tangent were measured at frequencies of 106 Hz and 1010 Hz, and the electric loss factor was calculated.
It is shown in the table in the figure.

Figures 2 and 3 are distribution diagrams of dielectric loss factors for the compositions of each material shown in Figure 1. Figure 2 shows the distribution of dielectric loss factors at a frequency of 106 Hz, and Figure 3 shows the distribution of dielectric loss factors at a frequency of 1010 Hz. It is a diagram.

That is, from Figure 1A and b, the dielectric loss factor increases as the content of alumina increases, and especially when the content exceeds 40% by weight, it increases rapidly especially in the band of 10 GHz or higher. As the content increases, the dielectric constant decreases and the dielectric loss tangent increases, and it can be seen that the dielectric loss factor increases particularly at 30% to 40% by weight.

Further, referring to FIGS. 2 and 3, it can be seen that at a frequency of 106 Hz (FIG. 2), when the magnesia content becomes 50% by weight or less, the dielectric loss factor suddenly increases.

In addition, in the case of the frequency band of 1010 Hz, the dielectric loss factor is about 21 with 40% by weight of alumina, 60% by weight of silica, and 40% by weight of magnesia, and the effect of using these ceramics is recognized for these frequency bands. But 106
It can be seen that since it is high in the Hz band, it is not suitable for ceramics whose characteristics are constant over a wide band.

Also, at 1010Hz (Figure 3), alumina is IO
When the weight percentage is exceeded, the dielectric loss factor becomes large, and the dielectric loss factor becomes larger than between 10 weight percent and O weight percent. Furthermore, although magnesia has an extremely small dielectric loss factor in both FIGS. 2 and 3, it is extremely susceptible to acids and is therefore unsuitable for use in electron tube stems or circuit boards.

The ceramics with uniform characteristics over a wide range obtained from FIGS. 1 to 3 above have a composition of silica O to 30% by weight, alumina 10% to 40% by weight, magnesia 5% by weight,
It is 0% to 90% by weight.

Ceramics with compositions within this range are shown in Figure 1A.
, b, each document number is shown surrounded by a black frame in FIGS. 2 and 3. Among these ceramics of each composition, document numbers 2, 3, 5, 10, 12, 17, 22, 2
As a comparative example, the frequency dielectric loss factor characteristics of Material Nos. 14 and 19 and forsterite [F] are shown in FIGS. 4 and 5. According to the figure, the dielectric loss factor in the range surrounded by the black frame in Figures 2 and 3 or in the vicinity thereof is extremely uniform against changes in frequency compared to forsterite or those outside the black frame range. It turns out that.

As described above, according to the present invention, it is possible to realize insulating ceramics that have a low dielectric loss factor even when the frequency becomes high, and have little change in frequency. In addition, in the present invention, if the content of each oxide is slightly outside the limited range, it is clear that it is within the range because it has the same effect as the present invention. be.

[Brief explanation of the drawing]

Figure 1 is a table showing the characteristics of three-component ceramics including the insulating ceramic of the present invention, Figures 2 and 3 are diagrams explaining the distribution of dielectric loss factors, and Figures 4 and 5 are It is a frequency dielectric loss factor characteristic of an Example and a comparative example. In the figure, 1 to 33 and 1 to 1 each indicate the same document number,
F and [F] indicate forsterite.

Claims (1)

[Claims] 1 An insulating ceramic consisting essentially of three components: magnesia, silica, and alumina, with 50% to 90% by weight of magnesia (MgO) and 30% by weight or less of silica (Si).
O_2 and 10wt% to 40wt% alumina Al_2
It is made by sintering O_3, 10^6 ~ 10^1^0
The dielectric loss factor in the high frequency region of Hz is 21×10^-^4
An insulating ceramic for high frequency circuit boards, characterized by the following: