This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-181097, filed on Sep. 16, 2016, the entire content of which is incorporated herein by reference.
This disclosure relates to a tuning-fork type crystal resonator that has a feature in a lead-out structure of an electrode.
In association with reduction in size of electronic equipment, more and more request for reduction in size to a tuning-fork type crystal resonator has increased. One of advantageous structures for the reduction in size of a tuning-fork type crystal resonator includes, what is called, a tuning-fork type crystal resonator with a three-arm structure. The tuning-fork type crystal resonator includes: a base portion; two vibration arms extending in parallel with one another from the base portion; and a supporting arm extending between these supporting arms from the base portion.
In the case of a tuning-fork type crystal resonator, as it is well known, it is necessary to extend a first excitation electrode and a second excitation electrode that are electrically separated as predetermined to total eight surfaces including principal surfaces and side surfaces of respective vibration arms. A tuning-fork type crystal resonator with a three-arm structure employs a structure that arranges a part of each of a first excitation electrode and a second excitation electrode on a supporting arm and uses the portions as connection pads with a package. Examples of such structure are disclosed by, for example, FIG. 5 of Japanese Unexamined Patent Application Publication No. 2003-163568, FIG. 1 of Japanese Unexamined Patent Application Publication No. 2010-259023, and similar Japanese Unexamined Patent Application Publication.
According to a first aspect of this disclosure, there is provided a tuning-fork type crystal resonator. The tuning-fork type crystal resonator includes a base portion, a first vibration arm and a second vibration arm, a supporting arm, a first connection pad and a second connection pad, and a first excitation electrode and a second excitation electrode. The first vibration arm and a second vibration arm are parallelly extending from the base portion. The supporting arm extends from the base portion between the first vibration arm and the second vibration arm. The first connection pad and a second connection pad are disposed on a part of the supporting arm to connect to outside. The first excitation electrode and the second excitation electrode respectively extended from the first connection pad and the second connection pad to the first vibration arm and the second vibration arm. The first excitation electrode is extended from the first connection pad so as to reach a side surface of the first vibration arm on a supporting arm side, via a region including a part of a principal surface of the supporting arm and a part of a side surface of the supporting arm on a first vibration arm side, an inner bottom surface of a first bifurcated portion present between the supporting arm and the first vibration arm, and a circumferential portion of the first bifurcated portion in the base portion. The second excitation electrode is extended from the second connection pad so as to reach a side surface of the second vibration arm on a supporting arm side, via a region including a part of the principal surface of the supporting arm and a part of a side surface of the supporting arm on a second vibration arm side, an inner bottom surface of a second bifurcated portion present between the supporting arm and the second vibration arm, and a circumferential portion of the second bifurcated portion in the base portion.
The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:
The following describes embodiments of a tuning-fork type crystal resonator according to this disclosure with reference to drawings. Each drawing used in the description is merely illustrated schematically for understanding this disclosure. In each drawing used in the description, like reference numerals designate corresponding or identical elements, and therefore such elements may not be further elaborated here. Shapes, dimensions, materials, and similar factor described in the following embodiments are merely preferable examples within the scope of this disclosure. Therefore, the disclosure is not limited to only the following embodiments.
[1. Structure of Tuning-Fork Type Crystal Resonator with Three-Arm Structure]
First, a description will be given of a fundamental structure of the tuning-fork type crystal resonator with the three-arm structure for better understanding of this disclosure.
The tuning-fork type crystal resonator 10 includes a base portion 11, a first vibration arm 13a and a second vibration arm 13b, a supporting arm 15, grooves 13c, and the excitation electrodes (see
In such tuning-fork type crystal resonator 10, as illustrated in
In order to generate such flexure vibration, the excitation electrodes are arranged with respect to the first vibration arm 13a and the second vibration arm 13b. The following describes this with reference to
As can be seen from
The structure of such tuning-fork type crystal resonator with the three-arm structure is preferably applied to a tuning-fork type crystal resonator of, in a package size of a crystal resonator, for example, equal to or less than 1.6 mm×1.0 mm size, what is called, equal to or less than 1610 size. Specimens of the following working example and comparative example are also examined with 1610 size. Obviously, this size is one example.
[2. Lead-Out Structure and Electrostatic Withstand Voltage Property of Excitation Electrode]
Next, the following describes that a lead-out structure of the excitation electrode influences an electrostatic withstand voltage property of the tuning-fork type crystal resonator, with reference to
[2-1. Structure of Tuning-Fork Type Crystal Resonator of Working Example and Comparative Example]
As illustrated in
In the tuning-fork type crystal resonator 20 of the working example, a width W1 of the portion provided on the principal surface of the supporting arm 15 in the first excitation electrode 21a was set to be 30 μm. A width W2 of the circumferential portion of the first bifurcated portion 17a of the base portion 11 in the excitation electrode 21a was set to be 50 μm. The portions of the excitation electrode 21a provided on the side surface of the supporting arm 15 and the inner bottom surface of the first bifurcated portion 17a were formed such that approximately all the portions became the excitation electrode in a thickness direction (a direction perpendicular to the paper surface in
Although the above-described electrode width and similar width were set to be the above-described values in the experiment, the width W1 is preferably at least 30 μm according to the examination of the inventor. Considering the effect of the disclosure that provides the electrode also on the side surface of the supporting arm and the inner bottom surface of the bifurcated portion, the width W2 of 50 μm is unnecessary, and the width W2 is preferably equal to or more than 20 μm considering convenience of manufacturing. Of the excitation electrode 21a, the portions provided on the side surface of the supporting arm and the bottom surface of the first bifurcated portion 17a does not need to be approximately all in the thickness direction of the tuning-fork type crystal resonator 20 (the direction perpendicular to the paper surface in
On the opposite-side surface of the tuning-fork, a second excitation electrode 21b also is provided beyond the contour of the second bifurcated portion 17b and over a part of the side surface of the supporting arm 15 and an inner bottom surface of the second bifurcated portion 17b. It is preferred that a width of the electrode and a detail of a formation region of the electrode on the side surface of the supporting arm and on the inner bottom surface of the second bifurcated portion 17b are similar to the first excitation electrode.
On the other hand, in the tuning-fork type crystal resonator 30 of the comparative example, as illustrated in
In the tuning-fork type crystal resonator 30 of the comparative example, the width W1 of the portion provided on the principal surface of the supporting arm 15 in the first excitation electrode 19a was set to be 30 μm. A width W4 of the circumferential portion of the first bifurcated portion 17a of the base portion 11 in the first excitation electrode 19a was set to be 20 μm. The above-described width W3 was set to be 20 μm.
On the opposite-side surface of the tuning-fork, also the second excitation electrode 19b is extended so as to reach the side surface of the second vibration arm 13b on the supporting arm 15 side via a part of the principal surface of the supporting arm 15, a region that is the principal surface of the base portion 11 and is apart from the second bifurcated portion 17b by the distance S, and the corner portion of the second bifurcated portion 17b on the second vibration arm 13b side.
[2-2. Electrostatic Withstand Voltage Test Result]
An electrostatic withstand voltage test (ESD test) was performed on the respective tuning-fork type crystal resonators of the working example and the comparative example, so as to confirm the effects of the disclosure. The specimens used for the test were prepared by implementing the tuning-fork type crystal resonator illustrated in
As the electrostatic withstand voltage test, an HBM (human body model) test of JESD22-A114 standardized by JEDEC was performed. This test applies voltages to external terminals of the vacuum-sealed tuning-fork type crystal resonators described above based on standardized conditions and sequentially increases the applied voltage, and then evaluates the withstand voltage by a frequency variation amount (Δf/f) and a crystal impedance (CI) variation amount (ΔCI) of the specimens at that time. The applied voltages were set as five conditions of 100 V, 200 V, 300 V, 400 V, and 500 V. The voltage was applied five times at each of the voltages. The frequency variation and the CI variation were measured every time, and the specimen that deviated from the standard was determined to be a failure. The upper limit of the applied voltage was set to 500 V due to their required specifications.
A portion 31 surrounded with a dashed circle in
According to an examination of the inventor of this application, in the case of the tuning-fork type crystal resonator with a three-arm structure, when the excitation electrode side is viewed from the adhesion pad, the region where the excitation electrode is extended inside the bifurcated portion from the crystal-resonator principal surface was found to be the region (weak region) easily broken down by static electricity (see
The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
Number | Date | Country | Kind |
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2016-181097 | Sep 2016 | JP | national |