JPS6012343Y2 - ceramic filter - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a ladder-type ceramic filter using piezoelectric resonators.

To explain a conventional ceramic filter using figures, FIG. 1 is a front sectional view of the ceramic filter.

1 and 2 are piezoelectric resonators;
The small protrusion 4 of the terminal plate 3 is adjacent to the vibrating contact point 2.

Insulating plates 5 are inserted between predetermined spaces between terminal plates 3 to configure a desired circuit in the filter.

Filter components such as the piezoelectric resonators 1 and 2, the terminal plate 3, and the insulating plate 5 are crimped and supported within a resin case 6 by an elastic body 7 and sealed with a lid 8.

The case 6 sealed with the lid 8 is housed in a metal case 9 and then sealed with a filler 10.

However, such a conventional ceramic filter requires a metal case 9 to ensure a shielding effect, and the filter becomes larger by the size of the metal case 9, which is contrary to miniaturization.

Furthermore, when the metal case 9 is manufactured by press working, the price of the metal case 9 becomes high considering the metal drawing die, which affects the cost of the filter.

Furthermore, since the case 6 is made of resin, there are also problems with mechanical strength, dimensional accuracy, temperature characteristics, etc.

In order to eliminate this drawback, the present invention makes the case 6 made of aluminum (A1) and forms an oxide film on its surface.

The oxide film is formed, for example, by anodic oxidation in an electrolyte solution.

This will be explained below using figures.

FIG. 2 is a front sectional view of a filter showing an embodiment of the present invention, in which 11 and 12 are piezoelectric resonators.

The vibration contacts of these piezoelectric resonators 11 and 12 are provided with terminal plates 13.
small protrusions 14 are adjacent to each other, and an insulating plate 15 is inserted between desired terminal plates 13, and filter components such as the piezoelectric resonators 11, 12, terminal plates 13, and insulating plates 15 are placed in a predetermined position in a case 16. After being inserted in the order shown in FIG. 1, it is pressed and supported by the elastic body 17, which is the same as in the conventional example shown in FIG.

In the present invention, the material of the case 16 is N, and the A1 anodic oxide film 18 is formed on the surface of the N case 16 to serve as insulation between the case 16 and the components.

After the components are housed in the case 16 and crimped, a lid 19 is placed on the case 16 and the components are sealed with a filler 20.

As described above, according to this embodiment, since the case 16 is made of metal, it has a shielding effect, and there is no need to cover it with the conventional metal case 9.

As described above, the oxide film 18 provides insulation between the case 16 and the components, so naturally there is no problem with the filter characteristics.

Therefore, the case 16 of the present invention satisfies the effects of the conventional resin case 6 and metal case 9 at the same time.
The metal case 9 is unnecessary, the wall thickness can be made thinner than that of a resin case, and the A1 anodic oxide film is extremely thin (several μm), contributing to the miniaturization of the filter.

Furthermore, since the present invention does not require a diaphragm die for the metal case 9, it is possible to reduce the cost of the filter.

It is well known that the N anodic oxide film has sufficient electrical insulation even if it is thin, and is also extremely resistant to mechanical peeling, so there is no need to worry about it in actual use. do not have.

The A1 soot of the present invention can be manufactured by Guicasting, and since it is made of metal, it is naturally extremely convenient in terms of mechanical strength, dimensional accuracy, temperature characteristics, etc., compared to conventional resin cases.

Next, as another example, if the lid 19 in FIG. 2 is also formed of A1 and the oxide film 18 is formed on its surface, the filter component is surrounded from all angles by N, so that the electrical shielding effect is improved. It becomes even more certain.

[Brief explanation of the drawing]

Figure 1 is a front sectional view of a conventional ceramic filter, Figure 2 is a front sectional view of a conventional ceramic filter.
The figure is a front sectional view of a ceramic filter showing an embodiment of the present invention. In the figure, 11 and 12 are piezoelectric resonators, 13 is a terminal board, 14 is a small protrusion, 16 is an A1 case, 18 is an N oxide film, and 19 is a lid.

Claims (1)

[Claims for Utility Model Registration] 1. Filter components such as a plurality of piezoelectric resonators and a plurality of terminal plates having small protrusions adjacent to the vibrating contacts of these piezoelectric resonators are housed and crimped in a case in a predetermined order. Further, in the ceramic filter covered with a lid, the case is made of aluminum whose surface is covered with an oxide film. 2. The ceramic filter according to claim 1, wherein the lid is also made of aluminum whose surface is covered with an oxide film.