JPH08316684A - Surface mount type piezo-electric device - Google Patents

Abstract

PURPOSE: To enhance the shield of a piezo-electric device while using a base and a cap of nonconductive material for its holder by adopting a shielding construction having the base and the cap coated with a conductive material and electrically connecting both to each other and to the ground in a state an external coating part is capped. CONSTITUTION: The inside of a ceramic base 11 is completely covered with a coating 17 except for a lead part of a lead electrode 15B. A coating 19 is applied to the entire surface of a cap 16 made of ceramic except for an internal side in contact with a sidewall 12, and a coating 19A is applied to an end in the same position as a coating 18 which is applied to an end of the sidewall 12. After a cap is applied to the base, sealing is performed with a sealant for junction and a contact face between the coating 18 and the coating 19A is connected by a conductive material 20 to provide continuity. The coating is grounded by end parts 17A and 17B to obtain shielding of a piezo-electric device 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention seals a piezoelectric element, which is a vibrating element such as a vibrator, a filter, and an oscillator, with a holder made of a non-conductive member base and its cap, and mounts it on a printed circuit board or the like. The present invention relates to a surface mount type piezoelectric device.

[0002]

2. Description of the Related Art In recent years, the tendency of high-density mounting on a printed circuit board (wiring board) has been remarkable, and accompanying this, surface mounting of electronic parts such as piezoelectric vibrators and oscillators has been advanced. These parts, whether they are passive elements or active elements,
Malfunction due to absorption of electromagnetic waves emitted from other parts.

Therefore, the cage used for the surface mounting of the piezoelectric element needs to have a shield structure that does not affect the electromagnetic waves to other parts or an immunity structure that does not allow the electromagnetic waves emitted from the other parts to enter.

Therefore, as shown in FIG. 8, the conventional cage has a structure in which a metal sheet (metal plate) 3 is used for a cap of a ceramic base 1.

A conductive film is formed on the bottom surface of the base 1, an internal mount for accommodating the piezoelectric element and a wiring member for surface mounting are formed inside the conductive film, and a plurality of conductive grooves 1a are formed on the side surface. Has been formed.

These conductive grooves 1a are provided to electrically connect the metal sheet 3 that covers the piezoelectric element after it is housed and the conductive film on the bottom surface. The internal piezoelectric element is formed by the metal sheet 3, the conductive film and the conductive groove 1a. Get a shield structure to cover. In addition,
The conduction between the conductive groove 1a and the metal sheet 3 is obtained by performing seam welding, soldering or the like between the base 1 and the metal sheet 3.

FIG. 9 is a side view showing a state in which the cage 1 having the above structure is mounted on the printed circuit board 4, and the bottom portion of the cage 1 is brought into contact with a ground wire or a ground sheet formed on the printed circuit board 4. I am letting you. Since the grounding wire or the like is normally held at the grounding potential via the grounding terminal, the entire surface of the metal sheet 3 is held at the grounding potential through the conductive groove 1a, so that the electromagnetic waves emitted from the electronic components inside the cage or the inside of the cage are held. External electromagnetic waves are prevented from entering the space. Reference numeral 2 is an internal mount that houses the piezoelectric element.

[0008]

In the conventional cage having the above structure, ceramics are used in place of the metal sheet for the cap when the cost of the cage is reduced. In this structure, a non-conductive adhesive (resin, which is superior in airtightness and workability compared to a conductive adhesive) is used to bond the ceramic base and the ceramic cap.
Glass) is used.

In the cage using the ceramic cap, electromagnetic waves easily enter and radiate from the upper part of the piezoelectric element to be housed, and thus the shield performance is inferior to the cap of the conductive metal sheet.

It is an object of the present invention to provide a surface mount type piezoelectric device in which the shield performance of the piezoelectric element is improved while using a base and a cap of a non-conductive member for the retainer.

[0011]

In order to solve the above-mentioned problems, the present invention provides a base of a non-conductive member having a lead portion for holding a piezoelectric element and for drawing out an electrode of the piezoelectric element to a terminal formed on the back surface. In the surface mount type piezoelectric device, the base and the cap are made of a conductive material on one or both of the inner surface and the outer surface. The shield structure is characterized in that the material is coated, and the outer coating portions of both the base member and the cap are electrically connected to each other in a state of being covered, and the coating portion is grounded at an arbitrary position.

[0012]

[Function] A base made of a non-conductive member such as ceramics is coated with a conductive substance, and at the same time, a cap of the non-conductive member such as ceramics is also coated with a conductive substance. After storing and holding the cap on the base and connecting the coating parts of the two to each other by conducting, and by grounding any part of the coating part of the base or the cap, a coating covering the entire piezoelectric element and its grounding can be obtained. Shields the entire circumference of the piezoelectric element.

[0013]

【Example】

(First Embodiment) FIG. 1 shows an embodiment of the present invention, showing a surface-mounted piezoelectric device having a package structure in which a box-shaped base is covered with a flat plate cap. In the figure, (a) is an inner plan view of the cap, (b) is a partially cutaway side view of the cap, (c) is a top view of the base, and (d) and (e) are ( c) a side sectional view of the base in the directions of arrows A and B,
A back view of the base is shown in (f).

Further, (g) is an external view of the base with the cap covered, and (h) is a partially cutaway external view thereof.

In the present embodiment, the base structure of the cage is made of ceramic and has a box shape. The base 11 is made of ceramics, the side wall 12 made of ceramics surrounds the base 11, and the base 11 is made of ceramics. A fixed portion 1 provided on the above to support the piezoelectric element 13 in an internal space in a cantilever manner.
4 and.

Lead electrodes 15A and 15B for drawing out the electrodes of the piezoelectric element 13 to the outside are formed of a conductive material on the fixed portion 14, and the lead electrode 15A has an end portion formed on the back surface of the base 11 below the fixed portion 14. The lead electrode 15B is extended along the upper surface of the base 11 to a position facing the fixed portion 14, and an end portion is formed on the back surface of the base 11.

Both ends of the lead electrodes 15A and 15B drawn out to the back surface of the base 11 are connected to electrodes such as a printed board on which a holder is mounted.

The piezoelectric element 13 is provided with counter electrodes 13B and 13C on both surfaces of a piezoelectric substrate 13A, and counter electrodes 13B and 1C are provided.
3C has a lead portion at the end of the fixing portion 14, and the lead electrode 15A, 15B is adhered by a conductive substance at the lead portion.

The cap 16 is made of ceramics,
It is formed in a plate shape that covers the upper surface of the base side wall portion 12.

Here, in this embodiment, in order to obtain a shield structure for the entire peripheral surface of the piezoelectric element 13, each portion of the base and the cap are coated with a conductive substance.

The coating is applied to the whole surface of the ceramic base 11 inside the base except for the lead portion of the lead electrode 15B, and the grounding terminals 17A and 17B are drawn out to the back surface of the base 11. The side wall portion 12 is provided with a coating 18 extending from the coating portion of the base 11 to the upper end surface at one place.

The ceramic cap 16 is coated on the entire inner surface except the contact surface with the side wall 12.
9 is applied, and the coating 19A is applied to the end surface of the side wall portion 12 at the same position as the coating 18 pulled out to the end surface.

After the base is capped, it is sealed with a sealing agent for bonding resin or frit glass, and then the contact surfaces of the coatings 18 and 19A are electrically connected by the conductive substance 20. .

With the above coating structure, in this embodiment, even when the base and the cap 16 are made of ceramics, both the upper surface and the lower surface of the piezoelectric element 13 are covered with the coatings 17 and 19, and the side portion of the piezoelectric element 13 is further covered. Can be covered with a coating 18 and these coatings can be grounded by the ends 17A, 17B.
It is possible to obtain a shield for almost the entire surface of 3.

The conductive connection between the coatings 17 and 19 may be obtained at a plurality of points.

(Second Embodiment) FIG. 2 shows another embodiment of the present invention. 1 is different from FIG. 1 in that the ceramic base side wall portion 12 is coated 21 on the entire inner surface and the entire end surface, and the ceramic cap 16 is coated 22 on the entire inner surface and the entire end surface. The structure is

At this time, the conductive connection between both coatings 21 and 22 after the base is covered with the cap is made over the entire circumference.

In the present embodiment, complete shielding is performed including the side surface of the piezoelectric element, and the shield effect can be further enhanced.

(Third Embodiment) FIG. 3 shows another embodiment of the present invention. 1 is different from FIG. 1 in that the base side wall 12 made of ceramics is coated with coating 23 on one side of its inner surface and up to its end face, and the cap 16 made of ceramics is also coated with coating 24 over the entire one end face. It is in.

The present embodiment has a structure in which one side of the piezoelectric element is completely shielded as compared with the structure of FIG. 1, the shield effect is enhanced as compared with the case of FIG. It is possible to improve work efficiency such as conducting connection.

In this embodiment, instead of coating on one side, both sides or three sides may be used.

(Fourth Embodiment) FIG. 4 shows another embodiment of the present invention. 1 is different from FIG. 1 in that the coating 18 is applied at a plurality of positions, the base side wall portion 12 is provided with a coating 25 on the entire end surface thereof, and the cap is also provided with a coating 26 on the entire inner surface and the entire end surface. It is in.

In the present embodiment, the conductive connection between the base and the cap is made over the entire circumference, which is more effective than the structure shown in FIG.

Note that the conductive connection between the base and the cap may be replaced with the entire circumference, and the work efficiency may be increased by providing a plurality of locations.

(Fifth Embodiment) FIG. 5 shows another embodiment of the present invention. 1 is different from FIG. 1 in that instead of the coating 17 applied on the upper surface of the base 11, the back surface of the base 11 is coated 27 on the entire surface excluding the terminals 15A and 15B.
The structure is

In this embodiment, the grounding position can be arbitrarily designed while the shield effect is the same.

For the other parts, the configurations shown in FIGS. 2 to 4 can be arbitrarily and selectively adopted.

(Sixth Embodiment) FIG. 6 shows another embodiment of the present invention, which is applied to a surface-mounted piezoelectric device having a package structure in which a flat plate base is covered with a box-shaped cap.

The inner plan view of the cap is shown in FIG.
(B) is a partially cutaway side view of the cap, (c) is a top view of the base, and (d) is a side sectional view of (c).
A rear view of the base is shown in (e). In addition, (f) shows a partially broken external view of the state in which the base is covered with a cap.

Fixing portions 32A and 3 which are inner leads formed by processing a metal base on a ceramic base 31
2B is joined with a conductive adhesive, and the piezoelectric element 33 is laid over it. In the piezoelectric element 33, electrode terminals 33A and 33B are drawn out to both ends of the back surface and the front surface, and coating is applied from this portion to the fixing portions 32A and 32B and the end surface of the base 31 to form electrode terminals 34 on the back surface of the base 31.
It is connected to A and 34B.

The box-shaped ceramic cap 36 is
The end face is assembled to face the base 31, and the piezoelectric element 3
Seal 3

Here, in the shield structure, a coating 37 is applied to the entire end surface of the base 31 and the entire back surface except the electrode terminals 34A and 34B, and a coating 38 is applied to the entire inner surface and the entire outer end surface of the cap 36. Is provided.

After coating the cap 36 on the base 31, these coatings 37 and 38 are electrically connected by a conductive adhesive 39 at their ends.

Also in this embodiment, the piezoelectric element 33 is completely covered with the coatings 37 and 38, and the complete shield is obtained.

(Seventh Embodiment) FIG. 7 shows another embodiment of the present invention. 6 differs from FIG. 6 in that instead of the coating 37, the coating 40 is applied to the upper surface of the base 31, and only one ground terminal 40A is formed on the back surface.
The conductive connection to the cap 38 is to be made in only one place.

The cap 38 is the ground terminal 4 of the base 31.
The connection terminal 38A is formed at the same position as 0A, and the base 31
For conductive connection with the both, a connection is obtained with the conductive adhesive 41.

Also in this embodiment, the same shield effect as that of FIG. 6 can be obtained. The other portions may have a structure obtained by arbitrarily combining the structures shown in FIGS.

Further, in the above embodiments, the case where the base is made of ceramic is shown, but when the base is made of a non-conductive member such as a resin, the same effect can be obtained by applying the same coating. Play. Although the cap is made of ceramics, it may be a cap made of resin or glass, which is a non-conductive member.

In addition, the cap and the base are sealed and the coating portion is conductively connected by a structure in which a conductive adhesive is used after sealing with a sealing agent, and a sealing agent is used after conducting by an adhesive. The structure may be a stop structure, a structure in which only a sealant is used, or a structure in which a conductive adhesive is used without a sealant, if conduction between the base and the cap is sufficient.

[0050]

As described above, according to the present invention,
In a surface-mounted piezoelectric device having a retainer composed of a non-conductive member base and a non-conductive member cap that covers the base to seal the piezoelectric element, the base is coated with a conductive material. The cap is also coated with a conductive material, the piezoelectric element is housed and held, the base is covered with the cap, and the two coating parts are electrically connected to each other. Since it has a structure to be grounded,
Obtaining a coating that covers the entire piezoelectric element and its grounding has the effect of ensuring the shield of the piezoelectric element.

[Brief description of drawings]

FIG. 1 is a diagram of a surface-mounted piezoelectric device according to an embodiment of the present invention.

2A and 2B are views of a surface-mounted piezoelectric device according to another embodiment of the present invention.

3A and 3B are views of a surface-mounted piezoelectric device according to another embodiment of the present invention.

FIG. 4 is a view of a surface-mounted piezoelectric device according to another embodiment of the present invention.

5A to 5C are views of a surface-mounted piezoelectric device according to another embodiment of the present invention.

6A to 6C are views of a surface-mounted piezoelectric device according to another embodiment of the present invention.

7A to 7C are views of a surface-mounted piezoelectric device according to another embodiment of the present invention.

FIG. 8 is an external perspective view of a conventional surface mount piezoelectric device.

FIG. 9 is a diagram of a mounted surface-mounted piezoelectric device mounted on a printed board.

[Explanation of symbols]

 11, 31 ... Base 12 ... Base side wall portion 13, 33 ... Piezoelectric element 14 ... Fixing portion 15A, 15B, 34A, 34B ... External terminal 16, 36 ... Cap 17, 18, 19, 35, 37, 38 ... Coating 17A, 17B ... Ground terminal 20 ... Conductive adhesive 32A, 32B ... Fixed part

Claims (1)

[Claims] 1. A base of a non-conductive member provided with a lead portion for holding a piezoelectric element and extending an electrode of the piezoelectric element to a terminal formed on a back surface, and a non-conductive member for covering the base to seal the piezoelectric element. In a surface-mounted piezoelectric device including a retainer composed of a cap of a conductive member, the base and the cap have a structure in which a conductive material is coated on one or both of the inner surface and the outer surface, and both the base and the cap are formed. A surface-mounted piezoelectric device characterized by a shield structure in which an outer coating portion of a member is covered and electrically connected to each other and grounded at an arbitrary point of the coating portion.