JPH0261179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to the structure of a three-terminal piezoelectric filter suitable for surface connection of terminals directly to a circuit pattern of a synthetic resin or ceramic substrate.

[Prior art and its problems]

With the recent miniaturization of electronic components, so-called chip-shaped high-frequency coils and capacitors, whose terminals are directly surface-connected to circuit patterns on synthetic resin or ceramic substrates, are now on the market.

In line with this trend, piezoelectric filters are often used with modified terminal pin shapes for surface connection, but the basic internal structure remains the same and is similar to that of the preceding electronic components. However, since the structure is not simple, various technical problems arise.

FIG. 7 is an exploded perspective view of a conventional three-terminal piezoelectric filter, and FIG. 8 is an assembled perspective view in which the terminals are modified for surface connection.

A box body 1 whose upper side and two opposing sides are open and which is integrally formed with a terminal 2, a conductive rubber 3 having anisotropic conductivity in the thickness direction, an entire surface electrode 4 on one main surface, and a box body 1 formed integrally with a terminal 2. It is composed of a piezoelectric vibrator 6 having a divided electrode 5 on its main surface, and a terminal 7 having an arcuate curved portion 8.

The divided electrode 5 of the piezoelectric vibrator 6 contacts the terminal 2 through the conductive rubber 3 inside the box 1, and the entire surface electrode 4
contacts the curved portion 8 of the terminal 7.

Reference numeral 9 denotes a protrusion that clamps the side surface of the piezoelectric vibrator 6 and fixes it inside the box body 1.

The box body 1 and the terminal 7 are housed in a case 10, and by pressing the end of the curved part 8 of the terminal 7 against the inner surface of the case 10, the curved part 8 and the full electrode 4, and the terminal 2 and the divided electrode 4 are separated. The connection is made by elastic contact. The presence of the conductive rubber 3 serves to further perfect such elastic contact and to prevent damage or movement of the piezoelectric vibrator 6 due to external forces. Reference numeral 11 denotes a protrusion, and the curved portion 8 is brought into point contact with the entire surface electrode 4 through the protrusion 11 .

Since FIG. 7 shows a structure in which the terminals are inserted into the board, for surface connection, the terminals 2 and 7 are bent into crank shapes, respectively, like terminals 2' and 7' in FIG. 8.

In this way, the conventional structure uses the elastic force of the curved part of the terminal to fix the entire structure, including the piezoelectric vibrator.
Moreover, the elastic force is obtained by utilizing the inner surface of a sealed body such as a case. However, in surface connection where soldering is done on the front side of the board, much higher heat is applied to the sealing body than in the conventional case where soldering is done on the back side of the board.
Thermal expansion tends to cause displacement of internal components and changes in elastic force. Therefore, the characteristics tend to change during soldering, which is undesirable in terms of product reliability. In addition, the conventional structure in which the terminals protruding from one side of the sealing body are surface-connected is fixed on one side, and therefore has the disadvantage that the fixing strength against vibration of the board is inferior to that of other electronic components. Furthermore, when mounting on a board using an automatic machine such as a chip placer, the fact that the terminals are located on only one side in a plane makes it difficult to accurately set the mounting position.

[Purpose of the invention]

An object of the present invention is to be able to fix the entire component including the piezoelectric vibrator without using the elastic force of the spring of a metal plate such as the curved part of the terminal, and to make the terminal protrude from the opposite side. An object of the present invention is to provide a surface-connected piezoelectric filter whose position can have planar symmetry.

[Structure and effects of the invention]

The piezoelectric filter of the present invention has at least one elongated recess, and is embedded in a rectangular box having opposing protrusions on its inner surface, and has one end protruding outward from the side. and an input terminal and an output terminal whose other ends are exposed above the opposing protrusions, and a ground terminal whose one end protrudes outward from the side of the box and whose other end is exposed at the bottom of the recess sandwiched between the protrusions. The terminal is provided with a divided electrode on one main surface and a full electrode on the other main surface, and the split electrode is connected to the exposed part of the input terminal and the output terminal, and the full face electrode is connected to the exposed part of the ground terminal, and the protruding part is connected to the exposed part of the ground terminal. It is characterized by consisting of a rectangular piezoelectric vibrator placed in a recess with its sides sandwiched between the sides, and its characteristics do not change due to the heat of the solder due to surface connection, and the fixing strength is improved, making it suitable for automatic machines. Also suitable for implementation by

[Embodiments of the invention]

Embodiments of the piezoelectric filter of the present invention will be described below with reference to FIGS. 1 to 5. 1 is an exploded perspective view, FIG. 2 is a perspective view showing the shape of a terminal, FIGS. 3 and 4 are an assembled plan view and an assembled side view, and FIG. 5 is a sectional view of FIG. 3.

In FIGS. 1 to 5, 20 and 23 are respectively a box body and a lid made of synthetic resin, 21 is a recess, and 22
24 is an input terminal, 25 is an output terminal, and 26 is a ground terminal.

The rectangular box body 20 is provided with an elongated recess 21 whose edge 30 follows the shape of the rectangular box body 20. At the center of the longer inner surface 27, there is a groove extending from the edge 30 of the recess 21 to the bottom surface 28.
Column-shaped protrusions 29 reaching up to 20 are provided facing each other.
The distance between the opposing protrusions 29 is the width W of the piezoelectric vibrator 22
is almost the same. The input terminal 24 is mainly buried within the edge 30 of the box body 20, but one end is made to protrude to the outside from the side surface so that it can be bent, and the other end is exposed above the protrusion 29. Output terminal 25
is similarly buried in the box body 20, with one end protruding to the outside on the same side as the input terminal 24, and the other end exposed above the other protrusion 29. The ground terminal 26 is buried in the bottom surface 28 of the recess 21 of the box body 20, with one end protruding from the side surface of the box body 20 opposite to the side surface from which the input terminals 24 and output terminals 25 project, making it bendable. The end is exposed on the bottom surface 28 sandwiched between the protrusions 29. The shape of each terminal is shown in FIG. 2 assuming that the box 20 is formed using a lead frame.

24', 25', and 26' are leads that become an input terminal 24, an output terminal 25, and a ground terminal 26, respectively. Although the planar shapes of the leads 24' and 25' are L-shaped, the inclined portions 31 and 32 are mainly buried in the box body 20, and the tips 33 and 34 are exposed. The horizontal part 35 of the lead 26' is buried,
A tip 44 bent like a crank in a vertical plane is exposed.

A rectangular piezoelectric vibrator 2 made of piezoelectric ceramic
On one side main surface of 2, there is a divided electrode 3 divided in the center.
6. A full-surface electrode 37 is formed on the other main surface. The thickness T is measured from the edge 30 of the box body 20 to the bottom surface 28
The depth is approximately the same. The piezoelectric vibrator 22 that performs stretching vibration in the length direction is connected to the side surface 3 of the vibration node.
8 is stored in the recess 21 while being held between the protrusions 29. A flat lid 23 having the same plane size as the box 20 is provided with a hole at a position corresponding to the recess 21 so as not to inhibit the vibration of the piezoelectric vibrator 22, and the lower side is connected to the edge of the box 20. 30 and recessed part 2
Seal 1. Although FIG. 3 to FIG. 5 are shown without the lid 23, the piezoelectric vibrator 22 has two divided electrodes 36 solder 41 on the exposed portion 39 of the input terminal 24 and the exposed portion 40 of the output terminal 25, respectively. Connected by The entire surface electrode 37 is connected to the exposed portion 42 of the ground terminal 26 while being pressed from above. By soldering the divided electrodes 36, the piezoelectric vibrator 22 is completely fixed to the box body 20. A conductive adhesive may be used to connect the divided electrode 36 to the exposed portions 39 and 40, but in any case, since they are located at the same horizontal position and close to each other, there is no need to use conductive wires. However, it is possible to connect conductors using a wire bonder in order to improve production efficiency. Input terminal 24 and output terminal 2 protruding from the side to the outside
5. The ground terminal 26 is bent from the side surface along the outer bottom surface 43 as shown in FIG. Of course, it is also possible to pull it out straight down and use a conventional terminal pin.

FIG. 6 is an assembled plan view showing another embodiment of the piezoelectric filter of the present invention.

The box body 50 is provided with two recesses 51,
A piezoelectric vibrator 52 is housed in each recess 51, and the two piezoelectric vibrators 52 are connected in series. 53 is an input terminal, 54 is an output terminal, 55
is a ground terminal, and its shape is the same as in the embodiments already described. The terminal 56 becomes an output terminal for the left vibrator 52 and an input terminal for the right vibrator 52. The planar shape of the terminal 56 is T-shaped, and the tip extends to two protrusions 57 and 58 and is exposed. Since the terminal 56 serves as a relay terminal, the portion to be soldered only needs to be exposed as the exposed portion 59, and all other portions may be buried in the box body 50. The ground terminals 55 may also be connected in common and only one terminal may be brought out to the outside. When connecting a plurality of piezoelectric vibrators 52 in this manner, the input terminal 53, output terminal 54, and ground terminal 55 of the entire piezoelectric filter may be protruded to the outside as surface connection terminals or pin terminals.

As described above, the piezoelectric filter of the present invention can fix the piezoelectric vibrator to the box body and connect the terminals and electrodes using solder or adhesive without using the elastic force of the spring of the metal plate. This fixation and connection occur at approximately the same vertical position and between the exposed portion of the terminal and the split electrode of the piezoelectric vibrator in very close proximity. Moreover, only the piezoelectric vibrator is inside the recess, and there is nothing else that can move, including the terminals. Therefore, even if high heat is applied to the box during face-to-face connection, as long as the solder or adhesive does not melt, the characteristics will not change due to changes in the positions of the components or the connections between the terminals and electrodes. In addition, the terminals can be projected outward from opposing sides of the box body to provide symmetry, thereby improving the strength of fixing the terminals to the substrate during surface connection. Obtaining this symmetry is also useful when attaching to a substrate using automatic machinery.

Furthermore, the piezoelectric filter of the present invention has a simple structure that can be almost completed by housing the piezoelectric vibrator in a recess and connecting the exposed part of the terminal of the box body and the split electrode with solder etc. Easy to assemble compared to piezoelectric filters. Of course, the piezoelectric filter of the present invention has a structure suitable for surface connection, but it can also be used by inserting it into a board by bending the protruding terminals straight down to form terminal pins. In this case, the piezoelectric filter using terminal pins can be made extremely low in height.

In the embodiment of the present invention, the pair of protrusions are provided at only one location, but if a plurality of nodes are to be formed in the piezoelectric vibrator, the pair of protrusions may be provided at multiple locations.
In that case, the exposed portion may be provided not on all the protrusions but only on a specific protrusion.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing an embodiment of the piezoelectric filter of the present invention, Fig. 2 is a perspective view showing the shape of the terminal, Figs. 3 and 4 are an assembled plan view and an assembled side view, and Fig. 5 3 is a sectional view of FIG. 3, FIG. 6 is an assembled plan view showing another embodiment of the present invention, and FIGS. 7 and 8 are an exploded perspective view and an assembled perspective view, respectively, of a conventional piezoelectric filter. 20,50...Box, 21,51...Recess, 2
2,52...Piezoelectric vibrator, 24,53...Input terminal, 25,54...Output terminal, 26,55...Earth terminal, 29,57,58...Protrusion, 30...
Edge, 36...Divided electrode, 37...Full surface electrode, 3
9, 40, 42...Exposed part.

Claims (1)

[Claims] 1. A rectangular box having at least one elongated recess and an opposing protrusion on its inner surface;
An input terminal and an output terminal embedded in the box body, each having one end protruding outward from the side surface and the other end exposed above the opposing protrusion; one end protruding outward from the side surface of the box body; A ground terminal is exposed at the bottom of the recess with the other end sandwiched between the protrusions, a split electrode is provided on one main surface, and a full electrode is provided on the other main surface, and the split electrode is used to expose the input terminal and output terminal. 1. A piezoelectric filter comprising a rectangular piezoelectric vibrator disposed within a recess with its entire surface electrode connected to an exposed portion of a ground terminal and its side surface being sandwiched between the protrusions.