JPH0685603A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To provide a resin sealed type piezoelectric resonator which can extremely improve the terminal strength without changing its external shape. CONSTITUTION:The vibrating electrodes 6, 8 and 11 are formed at the opposite positions on both sides of a piezoelectric substrate 1 together with the terminal electrodes 2, 3 and 13 formed at both end part and the center part of the substrate 1 respectively. Then the lead terminals 14-16 are soldered to the electrodes 2, 3 and 13 respectively. The rubber elastic matters 20 and 21 are applied to the vibrating electrodes and the periphery of them except at least the draw-out parts of the lead electrodes, the then the entire peripheral part of the substrate 1 is sealed with the sheathing resin 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated piezoelectric resonator.

[0002]

2. Description of the Related Art Conventionally, a resin-sealed piezoelectric resonator utilizing an energy trap type thickness-shear vibration mode has been used for ceramic filters and ceramic discriminators. This piezoelectric resonator is provided with a horizontally long rectangular piezoelectric substrate 30 as shown in FIG. 4. Input / output terminal electrodes 31 and 32 are formed at both ends of the surface of the piezoelectric substrate 30 and are biased to the terminal electrode 32 side. At the open position, a pair of vibrating electrodes 33, 3
4 are formed. These vibrating electrodes 33 and 34 pass through thin lead electrodes 35 and 36, respectively, and then pass through the terminal electrodes 31 and 32.
Connected with. A wide vibrating electrode 37 is formed on the back surface of the piezoelectric substrate 30 so as to face the vibrating electrodes 33, 34, and a ground terminal connected to the vibrating electrode 37 via a thin lead electrode 38 at the center of the piezoelectric substrate 30. The electrode 39 is formed. Lead terminals 40, 41, 42 are connected and fixed to the terminal electrodes 31, 32, 39 by soldering or the like.

In the case of the above piezoelectric resonator, the terminal electrodes 31, 3
After soldering the lead terminals 40, 41, 42 to 2, 39, the entire piezoelectric substrate 30 is dip-coated with a rubber-like elastic body 43 such as silicon rubber, and the periphery thereof is further dip-coated with an exterior resin 44 such as an epoxy resin. is doing. The rubber-like elastic body 43 serves as a cushion for enabling the thickness shear vibration generated in the vibrating electrodes 33, 34, 37.

[0004]

However, when the entire piezoelectric substrate 30 is dip-coated with the rubber-like elastic body 43 as described above, the rubber-like elastic body 43 causes the vibrating electrodes 33, 3 to be formed.
Since not only 4, 37 but also the terminal electrodes 31, 32, 39 and the lead terminals 40, 41, 42 are applied, the thickness of the exterior resin 44 covering the lead-out portions of the lead terminals 40, 41, 42 becomes thin. However, the terminal strength was weakened. Therefore, when a force in the cleaving direction acts on the input / output lead terminals 40 and 41 during automatic insertion into the printed circuit board, the exterior resin 44 is easily cracked, resulting in a decrease in reliability.

As a countermeasure for this, a method of increasing the thickness of the exterior resin 44 to improve the terminal strength can be considered. However, the exterior resin 44 is restricted due to the restrictions of the external dimension standard and the dip sag standard of the lead terminals 40, 41, 42. It was impossible to increase the thickness of the. Then, the objective of this invention is providing the piezoelectric resonator which can improve a terminal strength significantly, without changing an external shape.

[0006]

In order to achieve the above object, the present invention forms vibrating electrodes at opposing positions on the front and back surfaces of a piezoelectric substrate, and forms terminal electrodes at least at both ends of the piezoelectric substrate. In a piezoelectric resonator in which a lead terminal is connected to a terminal electrode, a rubber-like elastic body is applied to the vibrating electrode and its periphery so as not to cover at least the lead-out portion of the lead terminal, and the entire periphery of the piezoelectric substrate is covered with an exterior resin. It is sealed.

Since the rubber-like elastic body does not cover the entire piezoelectric substrate as in the prior art, but covers at least the vibrating electrode and its periphery so as not to reach the lead-out portion of the lead terminal, the outside thereof is covered with the exterior resin. At this time, the lead-out portion of the lead terminal is thickly and firmly fixed by the exterior resin. Therefore, the terminal strength is significantly improved, and resin cracking during automatic insertion can be prevented.

[0008]

1 and 2 show a piezoelectric resonator utilizing an energy trap type thickness shear vibration mode, which is an example of the present invention. This piezoelectric resonator is one in which two thickness-shear vibration mode resonators are formed on one piezoelectric substrate 1, and an equivalent circuit thereof is shown in FIG. The piezoelectric substrate 1 is made of a horizontally long rectangular piezoelectric ceramic substrate, and is polarized in the direction of its long side. Input / output terminal electrodes 2 and 3 are formed on both ends of the surface of the piezoelectric substrate 1, and the terminals 2 and 3 are electrically connected to the terminal electrodes 2 and 3 at positions near the center of the surface through thin lead electrodes 4 and 5. The vibrating electrodes 6 and 7 are formed respectively. A pair of vibrating electrodes 8 and 9 are formed adjacent to the vibrating electrodes 6 and 7, respectively, and these vibrating electrodes 8 and 9 are electrically connected to each other through a thin lead electrode 10. On the back surface of the piezoelectric substrate 1, a wide vibrating electrode 11 facing the vibrating electrodes 6 and 8 is provided.
And a wide vibrating electrode 12 opposed to the vibrating electrodes 7 and 9 are formed, and these vibrating electrodes 11 and 12 are electrically connected to each other through a grounding terminal electrode 13.

Lead terminals 14, 15, and 16 are connected and fixed to the terminal electrodes 2, 3, and 13 by soldering, respectively. In particular, the upper end portions of the input / output lead terminals 14 and 15 are folded back from the back surface side of the piezoelectric substrate 1 to the front surface side through the upper end, and the folded back end portions are soldered to the terminal electrodes 2 and 3, respectively. There is.

The vibrating electrodes 6, 8, 11 and the upper and lower surfaces of the piezoelectric substrate 1 adjacent thereto and the vibrating electrodes 7, 9, 12 and the upper and lower surfaces of the piezoelectric substrate 1 adjacent thereto are made of rubber-like elasticity such as silicon rubber. The body 20 and 21 are annularly covered, and the entire periphery of the piezoelectric substrate 1 is dip-coated with an epoxy-based exterior resin 22. Therefore, the thickness shear vibration generated at the vibrating electrode is not damped due to the cushioning property of the rubber-like elastic bodies 20 and 21. Further, since the rubber-like elastic bodies 20, 21 are not applied to the terminal electrodes 2, 3, 13 and the lead terminals 14, 15, 16 and are thickly and firmly covered with the exterior resin 22, the lead terminal 1
The strength of the drawn-out portions 14a, 15a, 16a of 4, 15, 16 is very large. Therefore, even if a tearing force acts on the input / output lead terminals 14 and 15 during automatic insertion, the exterior resin 22 can be prevented from cracking. The external dimensions and the dip position of the exterior resin 22 are the same as those of the conventional product.

Further, in the case of the three-terminal type piezoelectric resonator as described above, unnecessary vibration is likely to occur in the grounding terminal electrode 13 and the lead-out electrode 10 portion formed in the central portion of the piezoelectric substrate 1, so that the conventional vibration is generated. However, when the entire piezoelectric substrate was covered with a rubber-like elastic body, unnecessary vibration could not be effectively damped, but in the present invention, the vibration damping effect by soldering the ground lead terminal 16 and the vibration damping effect by the exterior resin 22 are provided. The unnecessary vibration is surely eliminated by the synergistic action with.

Since the conventional dip coating method cannot be used as a method for applying the rubber-like elastic bodies 20 and 21, for example, the piezoelectric substrate 1 is erected vertically, and liquid rubber is dispensed from above by a dispenser. It can be performed by dropping the elastic body. At this time,
Connect the tip of the dispenser to the vibrating electrodes 6, 8, 11 and 7,
By accurately locating the upper part of the piezoelectric substrate 1 in the upper portion of the piezoelectric substrate 1 and the central portion of the piezoelectric substrate 1 in the thickness direction, the dropped rubber-like elastic body flows evenly along the front and back surfaces of the piezoelectric substrate 1, and the lower surface of the piezoelectric substrate 1 And connected in a ring.

The present invention is not limited to the two-element type piezoelectric resonator as in the above-described embodiment, but may be a one-element type as shown in FIG. 4, which is a resin-sealed piezoelectric component having a rubber elastic layer. It is applicable in common to.

[0014]

As is apparent from the above description, according to the present invention, the rubber-like elastic material is applied to the vibrating electrode and its periphery,
Since the lead-out portion of the lead terminal is not covered with the lead-out portion, the thickness of the exterior resin at the lead-out portion of the lead terminal is increased, and the lead terminal can be firmly held. Therefore, the terminal strength can be dramatically improved without changing the external dimensions, and the effect is extremely large especially in the taping product compatible with the automatic insertion machine.

[Brief description of drawings]

FIG. 1 is a front view of an example of a piezoelectric resonator according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an equivalent circuit diagram of the piezoelectric resonator shown in FIG.

FIG. 4 is a front view of a conventional piezoelectric resonator.

[Explanation of symbols]

 1 piezoelectric substrate 2,3,13 terminal electrode 6,8,11 vibrating electrode 7,9,12 vibrating electrode 20,21 rubber-like elastic body 22 exterior resin

Claims (1)

[Claims] 1. A piezoelectric resonator in which vibrating electrodes are formed at opposite positions on front and back surfaces of a piezoelectric substrate, terminal electrodes are formed on at least both ends of the piezoelectric substrate, and lead terminals are connected to the terminal electrodes. A piezoelectric resonator characterized in that a rubber-like elastic body is applied to the vibrating electrode and its periphery so as not to cover at least the lead-out portion of the lead terminal, and the entire periphery of the piezoelectric substrate is sealed with an exterior resin.