JP2006033181A - Crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal oscillator for preventing changes in a vibration characteristic due to a frequency adjusting film. <P>SOLUTION: The crystal oscillator is configured, such that a vibration region is formed by forming exciting electrodes to both principal sides of a crystal chip and opposed to each other on both the sides and the frequency-adjusting film is provided onto the vibration region by vapor-deposition, a reinforcing layer whose area is greater than that of the vibration region and having a strong adhesive force to the crystal chip and the exciting electrode is provided onto the vibration region, and the frequency-adjusting film is provided onto the reinforcing layer. Further, the exciting electrodes are made of Au, Ag or Al, the reinforcing layer is made of Cr, Ni or Ti and the thickness of the reinforcing layer is configured to be 500 Å or smaller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystal resonator in the technical field, and more particularly to a crystal resonator in which the frequency adjustment is facilitated and the standard is maintained.

A crystal resonator is known as a frequency control element, and is used as an oscillator or a resonator (filter element). In recent years, with the improvement in performance of various electronic devices, strict standards for crystal resonators are required. One of the factors hindering such demand is a problem of the adjustment film at the time of frequency adjustment.

(Example of Prior Art) FIG. 4 is a view of a crystal resonator (crystal piece) for explaining one conventional example. FIG. 4 (a) is a cross-sectional view taken along the line AA in FIG. 4 (b). Is a plan view.

  The crystal resonator is made of a crystal piece 1 having an AT cut, for example. Both main surfaces of the crystal piece 1 have a pair of opposing excitation electrodes 2 (ab). For example, extraction electrodes 3 (ab) extend to both ends. Here, a planar outer region formed by the pair of excitation electrodes 2 (ab) is defined as a vibration region. Both extended ends of the extraction electrode 3 (ab) are fixed to the bottom surface of the container with a conductive adhesive (not shown) and hermetically sealed. And it is mainly incorporated in an oscillation circuit as an oscillator.

  The excitation electrode 2 (ab) and the extraction electrode 3 (ab) are made of Au (gold) whose base is Cr (chrome), for example, by vapor deposition. Since Au as the excitation electrode 2 (ab) or the like has a weak adhesion with the crystal piece 1, Cr having a strong adhesion with both is provided as a base. Then, a frequency adjustment film 4 made of, for example, Ag (silver) is provided on the excitation electrode 2 (ab) by vapor deposition to adjust the vibration frequency. In the AT cut, the vibration frequency increases in inverse proportion to the thickness of the crystal piece 1. Therefore, the vibration frequency is adjusted in the direction of decreasing by adding the frequency adjustment film 4.

(Problems of the prior art) However, the crystal resonator having the above-described configuration has the following problems when adjusting the vibration frequency by vapor deposition. That is, the frequency adjusting film 4 by vapor deposition may protrude from the outer periphery of the excitation electrode 2 (ab) due to the accuracy of the plating frame (mask) as shown in FIG.

  For example, the subsequent heat treatment changes the state of the adjustment film attached to the crystal piece 1, and there is a problem that the vibration characteristics change, for example, the vibration frequency changes. In short, since the adhesion strength between the crystal piece 1 and Ag as the adjustment film is small, the state changes due to, for example, condensation by heat treatment. As the size of the excitation electrode 2 (ab) decreases as the size of the excitation electrode 2 decreases, the mask accuracy decreases and the problem increases.

(Object of the Invention) An object of the present invention is to provide a crystal resonator in which a change in vibration characteristics due to a frequency adjusting film is prevented.

  According to the present invention, as shown in the claims (Claim 1), an excitation electrode opposed to both main surfaces of a crystal piece is formed to form a vibration region, and a frequency adjusting film is formed on the vibration region by vapor deposition. In the quartz crystal resonator, the quartz crystal piece and the excitation electrode and a reinforcing layer having a strong adhesive force are provided on the vibrating region as an area larger than the vibrating region, and the frequency adjusting film is provided on the reinforcing layer. The configuration is as follows.

  With such a configuration, the frequency adjustment film protruding from the excitation electrode during frequency adjustment adheres to the reinforcing layer. And since a reinforcement layer has strong adhesive force with a frequency adjustment film | membrane, it does not produce a change in a state by subsequent heat processing. Therefore, the vibration characteristics such as the vibration frequency are kept constant.

  As shown in claim 2 of the present invention, the excitation electrode of claim 1 is made of Au, Ag or AL, and the reinforcing layer is made of Cr, Ni or Ti. Thereby, the reinforcing layer strengthens the adhesive force between the crystal piece and the excitation electrode.

  In the third aspect, the reinforcing layer of the first aspect is 500 mm or less. As a result, the reinforcing layer has a large conduction resistance, so that it becomes an insulating film, and prevents, for example, a change in interelectrode capacitance without an electrical influence.

  In the fourth aspect, the vibration region of the first aspect is a planar outline of a pair of excitation electrodes provided on both main surfaces of the crystal piece. As a result, the crystal resonator is used as an oscillator.

  According to the fifth aspect of the present invention, the vibration region is a planar outer region of two pairs of input / output electrodes provided on both main surfaces of the crystal piece and constitutes a filter element. Thereby, for example, an MCF (Monolithic Crystal Filter) using a dual mode is obtained.

  FIG. 1 is a cross-sectional view of a crystal resonator illustrating one embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

  The quartz crystal resonator is made of an AT-cut crystal piece 1 as described above, and has a pair of excitation electrodes 2 (ab) and extraction electrodes 3 (ab) made of Au with Cr as a base on both main surfaces, and frequency adjustment. A membrane 4 is provided. Again, the planar outer region of the excitation electrode 2 (ab) is defined as a vibration region.

  Here, a reinforcing layer 5 made of Cr similar to the base is provided on the excitation electrode 2 a formed on at least one main surface of the crystal piece 1. The reinforcing layer 5 has a larger area than the excitation electrode 2a and is provided across the surface of the crystal piece 1 that circulates around the excitation electrode 2a. And thickness shall be about 500 mm or less. The frequency adjusting film 4 (Ag) is formed by vapor deposition on the reinforcing layer 5 on the excitation electrode 2a provided on one main surface.

  With such a configuration, as shown in FIG. 2 (plan view), even if the frequency adjustment film 4 (Ag) by vapor deposition protrudes from the excitation electrode 2a due to mask accuracy, the frequency adjustment film 4 is not the reinforcing layer 5. Adhere to. And since the reinforcement layer 5 has strong adhesive force with the frequency adjustment film | membrane 4 as Cr, it does not produce a change in a state also by subsequent heat processing. Therefore, the vibration characteristics such as the vibration frequency are kept constant.

  Further, since the Cr of the reinforcing layer 5 is set to 500 mm or less, the conduction resistance is large, so that it becomes an insulating film, and for example, the interelectrode capacitance between the excitation electrodes 2 (ab) is kept constant without electrical influence.

(Other matters) In the above embodiment, the excitation electrode 2 (ab) is Au, but it may be Ag or AL (aluminum). The reinforcing layer is Cr, but Ni (nickel), Ti (titanium), or the like may be used as long as the material has strong adhesion to the crystal and the excitation electrode 2 (ab).

  Further, although the quartz crystal resonator is intended to be provided with a pair of excitation electrodes 2 (ab) that are opposed to each other between the two principal surfaces, for example, as shown in FIG. 3 (ab), the two principal surfaces are opposed to each other. The same applies to a so-called MCF in which two pairs of excitation electrodes 2 (ab) are provided and one pair is an input electrode and the other pair is an output electrode.

  In this case, the outer area of the two pairs of excitation electrodes 2 (ab) is defined as a vibration region, and the reinforcing layer 5 is formed across the surface of the crystal piece 1 that goes around the vibration region. Then, the vibration frequency (center frequency) and bandwidth are adjusted. The bandwidth is adjusted by providing an adjustment film between the input / output electrodes.

  Further, although the MCF has two pairs of excitation electrodes facing each other, it is of course applicable even if there are three or more pairs of facing electrodes. Even in the case of the pair of excitation electrodes 2 (ab) in the embodiment, they are used as filter elements.

It is sectional drawing of the crystal oscillator explaining one Example of this invention. It is a top view of the crystal oscillator explaining the effect | action of one Example of this invention. 4A and 4B are diagrams of a crystal resonator illustrating another embodiment of the present invention, in which FIG. 4A is a cross-sectional view, and FIG. It is a figure of the crystal resonator explaining a prior art example, the figure (a) is a sectional view, and the figure (b) is a top view. It is a top view of the crystal oscillator explaining a prior art example.

Explanation of symbols

  1 crystal piece, 2 excitation electrode, 3 extraction electrode, 4 frequency adjustment film, 5 reinforcing layer.

Claims (5)

  In a quartz crystal resonator in which a vibration region is formed by forming excitation electrodes facing both main surfaces of a crystal piece, and a frequency adjustment film is provided on the vibration region by vapor deposition, the quartz crystal has a larger area than the vibration region. A quartz resonator comprising: a piece, the excitation electrode, and a reinforcing layer having a strong adhesive force provided on the vibration region, and the frequency adjusting film provided on the reinforcing layer.   2. The crystal resonator according to claim 1, wherein the excitation electrode is Au, Ag, or AL, and the reinforcing layer is Cr, Ni, or Ti.   The crystal unit according to claim 1, wherein the reinforcing layer is 500 mm or less.   2. The crystal resonator according to claim 1, wherein the vibration region is a planar outer region of a pair of excitation electrodes provided on both main surfaces of the crystal piece.   The vibration region is a planar resonator region of two or more pairs of opposing electrodes provided on both main surfaces of the crystal piece and constitutes a filter element.

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