JPS634364B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a drive electrode on the surface of one end in the length direction, a floating electrode at a position on the back surface corresponding to this drive electrode, and a drive electrode on the other end of the surface. In edge-mode ceramic filters, in which multiple piezoelectric ceramic plates each having external connection terminals extended from a portion of the piezoelectric ceramic plate are layered in the thickness direction, there is paper or the like that is slightly thinner than the layer spacing between each layer of the piezoelectric ceramic plates. A first coating layer is formed by sandwiching the spacer and immersing it in a melt of a low-temperature melting material that becomes solid or semi-solid at room temperature, such as paraffin, from the end of the drive electrode to a position approximately 1.5 times the width of the ceramic plate. The outside of the first coating layer and the external connection terminals are then immersed in a porous thermosetting resin to form a second layer.
The first resin coating layer is formed by heating at the same time.
The purpose is to absorb the coating layer into the resin coating layer to form micro spaces between the resin layer and spacer of the multi-element edge mode ceramic filter and the piezoelectric ceramic plate.

The edge mode ceramic filter element is the first
As shown in the figure, on one surface of a thin rectangular piezoelectric ceramic plate 1, metal drive electrodes 2, 3 and 4 are provided at the ends as shown in Figure 1a, and a portion of each of these electrodes is connected to a piezoelectric ceramic plate. The ceramic plate 1 is extended to the other end, and the input terminal 2', the ground terminal 3', and the output terminal 4' are pulled out to serve as terminals for external connection. Furthermore, as shown in FIG. 1b, floating electrodes 5 and 5' are provided on the back surface substantially opposite to the drive electrodes 2, 3, and 4 in FIG. 1a. The filter element is constructed by providing electrodes on both sides of the piezoelectric ceramic plate 1. When an input voltage is applied to the input terminal 2' and the ground terminal 3', the piezoelectric ceramic plate 1 vibrates in a displacement direction parallel to the main surface. Edge mode vibration is generated, and an output voltage having a frequency band determined by the width of the piezoelectric ceramic plate 1 is generated between the output terminal 2' and the ground terminal 3'. Furthermore, even if this vibration is mechanically touched in a direction perpendicular to the main surface, it has almost no effect on the vibration characteristics. The energy of the vibration at this time is concentrated only at the ends where the drive electrodes 2, 3, and 4 are provided, so if the length of the piezoelectric ceramic plate 1 is set to 2 to 3 times the width, , 3, and 4 at a position 1.5 times the width or more of the piezoelectric ceramic plate 1 from the end face thereof will not affect the characteristics as a filter. Further, in this type of edge mode ceramic filter, the thickness of the piezoelectric ceramic plate 1 is preferably about 1/10 of the width. For example, a filter with an intermediate frequency of 445 KHz for a radio or radio receiver has a thickness of about 0.2 mm compared to the width of the piezoelectric ceramic plate 1 of about 3 mm. Therefore, if an edge mode ceramic filter is fixed at one end that is not affected by vibrations, it will be mechanically weak against vibrations and shocks and may be damaged.

In the present invention, a plurality of edge mode ceramic filters are stacked in the thickness direction by attaching electrodes to a rectangular piezoelectric ceramic plate to cause edge mode vibration, and after sandwiching a spacer 7 between the layers of the vibrating part, the driving electrode part is A first coating layer is created by covering with paraffin, wax, etc., and then a porous thermosetting resin is soaked on the outside of this coating and heated to harden to form a resin layer.The first coating layer is liquefied to form a resin layer. The present invention relates to a coating method for a multi-element edge mode ceramic filter, in which a resin layer is coated by absorbing the resin layer into the piezoelectric ceramic plate to provide a minute space between the spacer and the piezoelectric ceramic plate.

Figure 2 shows an input terminal 2' for connecting the edge mode ceramic filter shown in Figure 1 to the outside;
An element is made by soldering lead terminals 2'', 3'', and 4'' to the ground terminal 3' and output terminal 4', respectively, with solder 6. This element is shown in the example of three elements in Fig. 3. 3 at a position more than 1.5 times the width of the piezoelectric ceramic plate 1 from the end of the drive electrodes 3, 4, and 5 as shown in FIG.
Piezoelectric ceramic plates 1 are held in a holder 10 at approximately equal intervals, stacked in the thickness direction,
Further, a spacer 7 having a thickness slightly smaller than the layer spacing is inserted between the layers of the vibrating portion of the piezoelectric ceramic plate 1. Next, approximately the width from the tip of the piezoelectric ceramic plate 1.
The first coating layer 8 is covered by immersing it in a melt of a low-temperature melting material that becomes solid or semi-solid at room temperature, such as paraffin or wax, to a position 1.5 times its original size. Furthermore, as shown in FIG. 4, a porous thermosetting resin is coated on the outside of the first coating layer 8, including the holder 10 and the external lead terminals 2'', 3'', and 4'', using a dipping method. When the resin coating layer 9 is formed by heating and curing,
The low-temperature melting wax of the first coating layer 8 is absorbed into the resin coating layer 9, creating a space in the first coating layer 8. When the spacer 10 is made of a flexible material such as Japanese paper, cloth, or plastic, even if the spacer material touches the piezoelectric ceramic plate 1, it will hardly affect the filter characteristics because the direction is perpendicular to the direction of edge mode vibration. do not have. Furthermore, since it is supported by the spacer 10 against external vibrations and shocks, the piezoelectric ceramic plate 1 is less likely to bend and is protected in terms of strength, and the resin coating layer 9 protects the internal vibrating parts. It is possible to obtain an edge mode ceramic filter that not only protects against mechanical vibrations and shocks but also prevents the intrusion of moisture, etc., and has high mechanical and electrical reliability against environmental changes over a long period of time.

Although the above description has been made regarding an edge mode ceramic filter, the same method can be applied to a filter constructed by stacking a plurality of edge mode resonators.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the structure of an edge mode ceramic filter, in which a is the surface where the drive electrode is provided, and b
is a plan view of the surface on which the floating electrode is provided, FIG. 2 is a plan view of the terminal in FIG.
FIG. 3 is a side cross-sectional view of an example in which three elements of the present invention are provided with a first coating layer, and FIG. 4 is a side cross-sectional view of an edge mode ceramic filter provided with a second resin coating layer according to the present invention. It is a diagram. In the figure, 1...piezoelectric ceramic plate, 2,
3, 4... Drive electrode, 5, 5'... Floating electrode,
2'...Input terminal, 3'...Ground terminal, 4'...
Output terminal, 2″, 3″, 4″……terminal for external connection,
6... Solder, 7... Spacer, 8... First coating layer, 9... Resin coating layer, 10... Holder.

Claims (1)

[Claims] 1 A vibrating end portion with a driving electrode provided on the surface of one end in the length direction of a rectangular piezoelectric ceramic plate and a floating electrode provided on the back surface thereof, and a terminal for external connection by extending a portion of each of the driving electrodes. In an edge mode ceramic filter in which a plurality of piezoelectric ceramic plates are stacked one on top of the other in the thickness direction, a spacer slightly thinner than the layer spacing is interposed between each layer of the piezoelectric ceramic plates, and a spacer is inserted between the piezoelectric ceramic plates from the vibrating end. A first coating layer is formed by immersing up to approximately 1.5 times the width of the plate in a melt of a low-temperature melting material that is fixed or semi-solid at room temperature, and further includes the outside of the coating layer and the terminal end. By soaking in a porous thermosetting resin to form a second resin coating layer, the first coating layer is absorbed into the second resin coating layer, and the first coating layer and the second resin coating layer are bonded. A method of packaging a multi-element edge-mode ceramic filter in which a microscopic space is formed between the filters.