JP2000114912A - Piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric component capable of making both securing mounting strength and solving an insertion loss failure compatible by managing the filling area of a low elastic material within a prescribed range. SOLUTION: Conductive supporting bodies 18 and 19 are fixed to a node part of one principal plane of a piezoelectric element 10 utilizing a length vibration mode and the bodies 18 and 19 of the element 10 are connected and fixed to the pattern electrodes 21 and 22 of a mounting substrate 20. A low elastic material 40 is filled in the gap between the element 10 and the substrate 20 in the range being narrower than the length of the element 10 with the bodies 18 and 19 as a center. In this case, the ratio of the filling width L1 of the material 40 to the length L of the element 10 is defined as 0.2<=L1/L<=0.45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for mounting a piezoelectric element such as an oscillator and a filter, particularly a piezoelectric element utilizing a length vibration mode, on a mounting substrate.

[0002]

2. Description of the Related Art Conventionally, in a piezoelectric component in which a piezoelectric element utilizing a longitudinal vibration mode is mounted on a mounting substrate on which a pattern electrode is formed, a conductive support is fixed to a node portion of the electrode of the piezoelectric element. It is known that this support is connected and fixed to a pattern electrode of a mounting substrate, and a gap between the piezoelectric element and the mounting substrate is filled with a rubber-like elastic material (low elastic material) such as silicone rubber or urethane rubber. (See Japanese Patent Application Laid-Open No. 10-107578).

FIG. 1 shows an example of such a piezoelectric component.
1 is a mounting substrate, 2 is a pattern electrode, 3 is a conductive adhesive,
4 is a piezoelectric element, 5 is a support, and 6 is a rubber-like elastic material.
Filling the rubber-like elastic material 6 as described above increases the mounting strength of the piezoelectric element 4 with respect to the mounting substrate 1 and increases the vibration load of the piezoelectric element 4 by the rubber-like elastic material 6, thereby reducing the substantial Qm. It is for lowering.

[0004]

In the case of a conventional piezoelectric component, the rubber-like elastic material 6 is filled over the entire area of the piezoelectric element 4. Therefore, it is easy to secure the mounting strength of the piezoelectric element 4, but the rubber-like elastic material 6 restrains the vibration of the piezoelectric element 4 more than necessary, and the Qm is excessively reduced, resulting in poor insertion loss. There was a case.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piezoelectric component which can maintain both the mounting strength and the elimination of poor insertion loss by managing the filling area of the low elasticity material within a predetermined range.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, an electrode is provided on at least one of the front and back main surfaces, and a conductive support is fixed to a node portion of the electrode. A piezoelectric element utilizing the length vibration mode, and an insulating mounting substrate having a pattern electrode formed on the upper surface, and a pattern electrode of the mounting substrate is formed on a main surface on which a support for the piezoelectric element is fixed. In the piezoelectric component having the support body connected to and fixed to the pattern electrode of the mounting board, the support body is connected to the gap between the piezoelectric element and the mounting board, in a range narrower than the length of the piezoelectric element around the support body. A piezoelectric component filled with a low-elastic material, wherein the ratio of the filling width L1 of the low-elastic material to the length L of the piezoelectric element is in the range of 0.2 ≦ L1 / L ≦ 0.45. I will provide a.

When the ratio L1 / L of the filling width L1 of the low elastic material to the length L of the piezoelectric element exceeds a predetermined value, Qm sharply decreases, and when L1 / L falls below the predetermined value, the mounting strength decreases. It drops sharply. Therefore, by maintaining the filling region of the low elasticity material within a predetermined range (0.2 to 0.45), it is possible to secure the mounting strength of the piezoelectric element to the mounting substrate and to eliminate the insertion loss of the piezoelectric element. We found that we could balance.

As the low elasticity material in the present invention, a material having soft rubber elasticity, such as silicone rubber or urethane rubber, having excellent adhesiveness to the piezoelectric element and the mounting substrate and having insulation properties is desirable. Young's modulus of low elasticity material is 1
MPa to 1000 MPa is desirable.

As a method of connecting the piezoelectric element to the pattern electrodes of the mounting substrate, for example, two electrodes are formed on one main surface of the piezoelectric element, supports are fixed to these electrodes, and these supports are mounted. The two pattern electrodes of the substrate may be individually connected and fixed, or a support may be fixed to the electrode on one main surface of the piezoelectric element, and this support may be connected to one pattern electrode of the mounting substrate and The electrode on the other main surface of the element may be connected to another pattern electrode of the mounting board via a wire. In either case,
A gap between the piezoelectric element and the mounting board is filled with a low elastic material.

[0010]

2 and 3 show an example of a piezoelectric component according to the present invention. 10 is a piezoelectric element, 20 is a mounting board,
Reference numeral 30 denotes a cover.

The piezoelectric element 10 utilizes a longitudinal vibration mode, and includes a rectangular parallelepiped base 11 as shown in FIG. The base 11 is formed of, for example, a piezoelectric ceramic material, and a plurality of internal electrodes 12 are provided in the base 11.
Is formed in a layer shape so as to be orthogonal to the longitudinal direction. Base 1
1 denotes one internal electrode 12 as indicated by an arrow P in FIG.
Are polarized in the longitudinal direction of the base 11 so as to be opposite to each other on both sides. However, both ends of the base 11 are not polarized.

On one side surface of the base 11, a groove 13 extending in the longitudinal direction of the base 11 is formed.
One side is divided into two. Further, a first insulating film 14 and a second insulating film 15 are formed on the side surface divided by the groove 13. On one side of the base 11 divided by the groove 13, every other exposed portion of the internal electrode 12 is covered with a first insulating film 14. On the other side of the base 11 divided by the groove 13, Internal electrode 12 not covered with film 14
Every other exposed portion is covered with the second insulating film 15.

External electrodes 16 and 17 are formed on the portion of the base 11 where the insulating films 14 and 15 are formed, that is, on both sides of the groove 13. Therefore, the internal electrode 12 not covered with the first insulating film 14 is connected to the external electrode 16, and the internal electrode 12 not covered with the second insulating film 15 is connected to the external electrode 17. That is, the internal electrodes 12 are alternately connected to the external electrodes 16 and 17.

In the piezoelectric element 10, the external electrodes 16, 1
7 is used as an input and output electrode. At this time, the base 1
1 except for both ends, an electric field is applied between the adjacent internal electrodes 12, so that it becomes piezoelectrically active.
At both ends, the substrate 11 is not polarized, and furthermore, since no electrodes are formed on both end surfaces of the substrate 11, no electric field is applied and the substrate becomes piezoelectrically inactive. Therefore, the external electrode 1
By applying a signal between the bases 6 and 17, an alternating electric field in the longitudinal direction of the base 11 is applied to each piezoelectric layer of the active portion, and a driving force for expansion and contraction is generated in each piezoelectric layer. The fundamental vibration in the vibration mode is excited. The base 11
Although inactive portions are provided at both ends of the substrate 11, the inactive portions are not essential, and the entire substrate 11 may be used as the active portions.

Conductive supports 18 and 19 are fixed on the external electrodes 16 and 17 of the piezoelectric element 10 and at the node (central portion in the lengthwise direction) of the piezoelectric element 10, respectively. The supports 18 and 19 of this embodiment are formed by applying a conductive paste on the electrodes 16 and 17 to a thickness of, for example, about 100 μm and curing the paste.
Gold bumps or the like may be used.

The structure of the piezoelectric element 10 is not limited to the structure shown in FIG. 4, but may be a structure as shown in FIG. In this case, two types of piezoelectric layers (a) and (b) as shown in FIG.
To expose the internal electrodes 12 in two rows on one side surface of the base 11. Then, by forming the external electrodes 16 and 17 at the portions where the internal electrodes 12 are exposed, every other internal electrode 12 is connected to the external electrodes 16 and 17. In this case, no groove 13 is formed.

The mounting substrate 20 is a rectangular insulating thin plate made of alumina ceramic, glass ceramic, glass epoxy resin or the like. On the upper surface of the mounting substrate 20, input and output side pattern electrodes 21 and 22 are formed by sputtering, vapor deposition, and evaporation. It is formed by a known method such as printing. A part of each of the pattern electrodes 21 and 22 is extended to the back side via the side edge of the mounting board 20. The piezoelectric element 10 is connected and fixed so that the input and output external electrodes 16 and 17 face the pattern electrodes 21 and 22 of the mounting substrate 20. That is, the support 18 on the external electrode 16 is placed on the connecting portion 21 a of the input-side pattern electrode 21,
Are bonded onto the connection portions 22a of the output-side pattern electrodes 22 with a conductive adhesive 23 (see FIG. 2) or the like. The piezoelectric element 10 is horizontally mounted on the mounting substrate 20 so that the end of the piezoelectric element 10 does not contact the upper surface of the mounting substrate 20.

After the piezoelectric element 10 is mounted on the mounting substrate 20, the gap between the piezoelectric element 10 and the mounting substrate 20 is filled with a low elastic material 40 such as silicone rubber or urethane rubber in a predetermined range. That is, as shown in FIG. 2, the low elasticity material 40 is
In a range smaller than the length L. In the present invention, the ratio between the filling width L1 of the low elastic material 40 and the length L of the piezoelectric element 10 is set in the following range. 0.2 ≦ L1 / L ≦ 0.45

The filling width L1 of the low elasticity material 40 and the piezoelectric element 1
The grounds for setting the ratio to the length L of 0 as described above will be described below. FIG. 7 shows the relationship between L1 / L (%) and Qm.
As is clear from FIG. 7, when L1 / L is 45% or less, Qm has half or more of the maximum value, whereas
When L exceeds 45%, the restraint of vibration increases, and it can be seen that the Qm value of the piezoelectric element sharply drops to half or less of the maximum value. In FIG. 7, the substitution characteristic of the insertion loss characteristic is represented by the sharpness (Qm value) of the mechanical resonance of the piezoelectric element. . FIG. 8 shows the relationship between L1 / L (%) and the mounting strength of the piezoelectric element 10 to the mounting substrate 20. As shown in FIG.
When L1 / L is less than 20%, the mounting strength is the maximum strength (L1
/ L = 1) or less;
If 1 / L is 20% or more, the mounting strength is set to 1 of the maximum strength.
/ 2 or more. As described above, L1 / L is set to 0.
By setting the value in the range of 2 to 0.45, two conditions of eliminating the insertion loss defect and securing the mounting strength can be satisfied.

A cover 30 for covering the piezoelectric element 10 in a non-contact state is adhered on the mounting substrate 20 with an adhesive or the like, and the periphery of the piezoelectric element 10 is sealed. The cover 30 may be a resin cover or a metal cover. As described above, a surface-mounted piezoelectric component can be obtained.

As shown in FIGS. 4 and 5, the piezoelectric element of the above embodiment has been described as an example in which a plurality of piezoelectric layers are laminated to form a length vibration mode element as a whole. The present invention is not limited to this, and may be a length vibration mode element in which electrodes are formed on both main surfaces of one piezoelectric substrate as in the related art. In this case, a conductive support is formed on the electrode on one main surface and connected and fixed to one pattern electrode on the mounting substrate,
The electrode on the other main surface may be connected to the other pattern electrode via a conductive wire.

[0022]

As apparent from the above description, according to the present invention, the gap between the piezoelectric element and the mounting substrate is filled with a low elastic material in a range narrower than the length of the piezoelectric element around the support, Since the ratio of the filling width L1 of the low elastic material to the length L of the piezoelectric element is set to 0.2 ≦ L1 / L ≦ 0.45, the restraint on the length vibration of the piezoelectric element is small, and the mechanical mounting strength is small. Can be secured. Therefore, a highly reliable piezoelectric component having stable vibration characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of an example of a conventional piezoelectric component.

FIG. 2 is a side view of an example of the piezoelectric component according to the present invention.

FIG. 3 is an exploded perspective view of the piezoelectric component shown in FIG.

FIG. 4 is a perspective view of an example of a piezoelectric element used for the piezoelectric component of FIG.

5 is a perspective view of another example of a piezoelectric element used for the piezoelectric component of FIG.

FIG. 6 is a front view of a piezoelectric layer constituting the piezoelectric element of FIG. 5;

FIG. 7 is a diagram showing a relationship between a ratio between a filling width of a low elastic material and a length of a piezoelectric element and Qm.

FIG. 8 is a diagram showing a relationship between a ratio between a filling width of a low elastic material and a length of a piezoelectric element, and mounting strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric element 16, 17 Electrode 18, 19 Support 20 Mounting substrate 21, 22 Pattern electrode 40 Low elastic material

Claims (1)

[Claims] An electrode is provided on at least one of the front and back main surfaces,
A piezoelectric element utilizing a length vibration mode in which a conductive support is fixed to a node portion of the electrode; and an insulating mounting substrate having a pattern electrode formed on an upper surface thereof. The support of the piezoelectric element is fixed. The main surface is opposed to the surface of the mounting substrate on which the pattern electrodes are formed, and in a piezoelectric component formed by connecting and fixing the support to the pattern electrode of the mounting substrate, in the gap between the piezoelectric element and the mounting substrate, A low elastic material is filled in a range narrower than the length of the piezoelectric element around the support, and the ratio of the filling width L1 of the low elastic material to the length L of the piezoelectric element is expressed by:
A piezoelectric component having the following range. 0.2 ≦ L1 / L ≦ 0.45