JP2017085532A - Crystal oscillator and electrode structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure of a crystal oscillator having excellent contact with an electrode layer, and capable of simultaneously achieving high reliability and lower price and stably operating although it uses Ag-Pd-Cu (APC) alloy, and a crystal oscillator including the same.SOLUTION: A crystal oscillator 20 includes a crystal lens 21 which oscillates by an electric signal, and electrodes 22a and 22b arranged on at least one surface of the crystal lens and including a first layer 23a and a second layer 23b. The first layer includes tungsten(W), and the second layer includes Ag-Pd-Cu(APC) alloy.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a crystal resonator and an electrode structure thereof, and provides an electrode structure of a crystal resonator capable of stably operating while simultaneously satisfying high reliability and low price, and a crystal resonator including the same. To do.

  In general, a crystal resonator is used for various applications such as a frequency oscillator, a frequency adjuster, and a frequency converter. Such a crystal resonator uses a crystal having excellent piezoelectric characteristics as a piezoelectric material, and at this time, the crystal serves as a stable mechanical vibration generator.

  In this case, the quartz crystal used as the piezoelectric body is artificially grown in a high-pressure autoclave, and is processed in size and shape so as to have desired characteristics by cutting around the crystal axis. It is manufactured in the form of a wafer. At this time, the crystal must be formed to have a low phase noise, a high Q value, and a low frequency change rate with respect to time and environmental changes.

  Here, the Q value is a value indicating band selection characteristics in a resonator, a filter, an oscillator, or the like, and is also called a quality factor. The Q value is calculated by the ratio of the center frequency to the bandwidth of 3 dB (dB), and the larger the Q value, the better the frequency selection characteristic.

  A two-layer electrode structure was used for a conventional crystal unit. Specifically, gold (Au) is used as an electrode layer, and chromium (Cr) is used as a bonding layer between a quartz substrate and a gold (Au) electrode layer.

  Such a structure using gold (Au) as an electrode layer requires an expensive cost, and a technique for substituting this structure has been studied. In particular, an Ag—Pd—Cu (APC) alloy has been developed as a material that can replace gold (Au). However, such an APC alloy has a problem that contact with a quartz substrate is lowered.

  Therefore, there is a need for a solution to solve this.

JP2015-109633A

  The object of the present invention is to use Ag-Pd-Cu (APC) alloy as an electrode layer, and to be excellent in contact with the electrode layer, to simultaneously satisfy high reliability and low price and to operate stably. An object is to provide an electrode structure of a crystal resonator and a crystal resonator including the same.

  A crystal resonator according to an embodiment of the present invention includes a lens that vibrates by an electrical signal, and an electrode unit including a first layer and a second layer disposed on at least one surface of the lens, and the first layer includes: Tungsten (W) is included, and the second layer includes an Ag—Pd—Cu (APC) alloy.

  A crystal resonator according to another embodiment of the present invention includes a crystal that vibrates by an electric signal, and an electrode unit including first to fourth layers disposed on at least one surface of the crystal, and the first layer The third layer includes tungsten (W), and the second layer and the fourth layer include an Ag-Pd-Cu (APC) alloy.

  According to still another embodiment of the present invention, an electrode structure of a crystal resonator includes a first layer and a second layer stacked on a main surface of a crystalline lens, the first layer includes tungsten (W), and the second layer includes the second layer. The layer comprises an Ag—Pd—Cu (APC) alloy.

  Since the crystal resonator according to the embodiment of the present invention uses Ag (Pd) -Cu (APC) alloy as an electrode layer and uses tungsten (W) as an intermediate layer between the crystal substrate and the electrode layer, the electrode layer is peeled off. The phenomenon can be prevented.

  Therefore, it is possible to reduce the price as compared with a conventional electrode layer using gold (Au), and at the same time, have an electrode structure of a crystal resonator capable of operating stably and stably. A crystal resonator including the same can be provided.

It is a schematic sectional drawing of the crystal oscillator package by one Example of this invention. It is a schematic sectional drawing which shows the two-layer type electrode structure of the crystal oscillator by one Example of this invention. It is a schematic sectional drawing which shows the 4-layer type electrode structure by the other Example of this invention. The results of a peel test using a tape with respect to Comparative Example 1 in which an electrode layer was formed directly using Ag—Pd—Cu (APC) alloy on the top of the crystalline lens were photographed. This is an enlarged photograph of the peel test result. After forming an intermediate layer using chromium (Cr) on the upper part of the crystalline lens, an electrode layer is formed using Ag-Pd-Cu (APC) alloy on the upper part of the intermediate layer, and the intermediate layer is wet etched. The result was taken. This is a photograph of a crystal resonator in which an intermediate layer is formed using tungsten (W) on the upper portion of the crystalline lens, and then an electrode layer is formed on the upper portion of the intermediate layer using an Ag-Pd-Cu (APC) alloy. A quartz crystal of a comparative example in which the electrode layer is made of gold (Au) and the intermediate layer is made of chromium (Cr), the electrode layer is made of an Ag—Pd—Cu (APC) alloy, and the intermediate layer is made of tungsten (W). It is a graph which shows the result of having measured each ESR of the crystal oscillator of the Example which was made.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for a clearer description.

  In addition, the same reference numerals are used throughout the drawings for parts having similar functions and operations.

  Further, in the entire specification, “including” a component means that the component can be further included without excluding other components unless specifically stated to the contrary. To do.

  Hereinafter, a crystal resonator and an electrode structure thereof according to an embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 shows a cross section of a crystal resonator package 1 according to an embodiment of the present invention. Referring to FIG. 1, the crystal unit 10 includes a crystal body 11 including a crystal piece, and a first electrode 12 a and a second electrode 12 b formed on both surfaces of the crystal body 11. In particular, the first electrode 12a and the second electrode 12b may be formed symmetrically on both surfaces of the crystalline lens 11. Thereby, the crystal unit 10 can be formed in a package structure as shown in FIG.

  Such a crystal resonator package 1 includes a floor layer 16a, an electrode pad 14 formed on the floor layer 16a, a crystal body 11 fixed on one side on the electrode pad, and an upper surface of the floor layer 16a. And a bump 15 disposed between the other side of the crystalline lens 11.

  In this case, as described above, the first electrode 12 a and the second electrode 12 b that are electrically connected to the electrode pad 14 may be formed on the upper and lower surfaces of the crystalline lens 11. A support layer 16b that forms a space for accommodating the crystalline lens 11 may be formed on the peripheral edge of the floor layer 16a. A lid 17 for sealing the space can be disposed on the support layer 16b.

  2 and 3 are enlarged views of the crystal unit 10 shown in FIG. A crystal resonator 20 having a two-layer electrode structure according to an embodiment of the present invention will be described with reference to FIG. 2 and a crystal resonator 30 having a four-layer electrode structure will be described with reference to FIG.

  Crystal resonators 20 and 30 according to an embodiment of the present invention include crystal bodies 21 and 31, first electrodes 22 a and 32 a and second electrodes 22 b and 32 b formed on upper and lower surfaces of the crystal bodies 21 and 31, respectively. including. The first electrode 12a and the second electrode 12b can be defined as electrode portions. That is, the electrode unit can be disposed on at least one surface of the crystalline lenses 21 and 31.

The crystal bodies 21 and 31 generate a piezoelectric effect by an electric signal and are not limited thereto, but a crystal piece made of SiO ₂ can be used. In this case, the crystal bodies 21 and 31 are formed by cutting a crystal wafer.

  The first electrodes 22a and 32a and the second electrodes 22b and 32b provide an electric signal to the crystal bodies 21 and 31 to generate a piezoelectric effect in the crystal bodies 21 and 31, and the piezoelectricity of the crystal bodies 21 and 31. It can be a means for outputting an electric signal depending on the effect. In this case, the first electrodes 22a, 32a and the second electrodes 22b, 32b are formed by depositing substances to be described later on the upper and lower surfaces of the crystalline lenses 21, 31 through a process such as vapor deposition.

  The electrode structure of the crystal resonator will be described in more detail. 2 and 3 showing the electrode structure of the crystal resonator according to one embodiment of the present invention, the crystal bodies 21 and 31 that vibrate by an electric signal and the crystal bodies 21 and 31 are formed on both surfaces and laminated in order. An intermediate layer and an electrode layer.

  The intermediate layer is formed using tungsten (W), and the electrode layer is formed using an Ag—Pd—Cu alloy.

  Referring to FIG. 2 showing a two-layered electrode structure according to an embodiment of the present invention, a first layer 23a, which is an intermediate layer containing tungsten (W), and an electrode layer containing an Ag—Pd—Cu alloy. The first electrode 22a and the second electrode 22b can be formed by the two layers 23b.

  The first layer 23a serves to improve the adhesion between the crystalline lens 21 and the first electrode 22a or the second electrode 22b.

  The second layer 23b provides electrical conductivity, can be reduced in price as compared with a conventional electrode layer using gold (Au), and at the same time has high reliability and operates stably. Can be used, preferably an Ag-Pd-Cu (APC) alloy.

  According to an embodiment of the present invention, the ratio of the thickness of the first layer 23a, which is an intermediate layer, to the thickness of the first electrode or the second electrode is 2 to 30%, which is an electrode layer. The thickness ratio of the second layer 23b may be 70 to 98%.

  When the thickness of the intermediate layer that is the first layer 23a is less than 2% of the thickness of the entire electrode, the adhesive force between the electrode and the crystalline lens may be reduced. On the other hand, if it exceeds 30%, the specific resistance of the entire electrode increases, and there is a risk that the equivalent series resistance (ESR: Equivalent Series Resistance) increases.

  Moreover, when the ratio of the thickness of the intermediate layer is within the range as described above, it is not limited to this, but the entire electrode is within the thickness range of 0.1 to 1.0 μm. Can be formed.

  According to another embodiment of the present invention, the crystal unit may have an electrode structure having a multilayer structure.

  In the case of a crystal resonator having a multilayer structure according to an embodiment of the present invention, the crystalline lens may include a stacked structure in which intermediate layers and electrode layers are alternately and repeatedly stacked from the main surface.

  A two-layer electrode structure may have a structure in which two or more electrode structures are repeatedly stacked, and may include a plurality of intermediate layers made of tungsten (W). In addition, a plurality of electrode layers made of an Ag—Pd—Cu alloy can be included. The plurality of intermediate layers and electrode layers may have a structure in which they are alternately stacked. In the case of a crystal resonator having a multilayer electrode structure, the adhesive force between the first electrode 32a or the second electrode 32b and the crystal 31 can be further improved.

  Referring to FIG. 3, a crystal resonator having a four-layer electrode structure according to an embodiment of the present invention includes a crystal body 31 that vibrates in response to an electric signal, and an intermediate layer and an electrode layer that are sequentially stacked on both surfaces of the crystal body 31. A first electrode 32a and a second electrode 32b.

  The intermediate layer includes a first layer 33a and a third layer 33c containing tungsten (W), and the ratio of the thickness of the intermediate layer to the thickness of the first electrode or the second electrode is 2 to 30%. Can be. The electrode layer includes a second layer 33b and a fourth layer 33d containing an Ag-Pd-Cu (APC) alloy, and the electrode layer has a thickness that is greater than a thickness of the first electrode or the second electrode. The ratio can be 70-98%.

  That is, in the crystal resonator according to the embodiment of the present invention, the first layer 33a, the second layer 33b, the third layer 33c, and the fourth layer 33d are sequentially stacked from the surface of the lens, and the intermediate layer and the electrode layer are alternately arranged. A four-layer electrode structure laminated on the substrate.

  The lens, the intermediate layer, and the electrode layer have different coefficients of thermal expansion, but by using a multilayer electrode structure, the difference in thermal expansion between the lens, the intermediate layer, and the electrode layer can be compensated more precisely. .

  The thickness ratio of the intermediate layer including the first layer 33a and the third layer 33c may be 2 to 30% with respect to the thickness of the first electrode or the second electrode. This is because when the thickness of the first layer 33a and the third layer 33c is less than 2%, the adhesive force between the electrode and the crystalline lens may be reduced, and the thickness of the first layer 33a and the third layer 33c. This is because when the thickness exceeds 30%, the specific resistance of the entire electrode increases, and there is a possibility that the equivalent series resistance (ESR) is increased.

  The proper composition and thickness will vary depending on the product design, and the criteria can be adjusted by the thickness of the second and fourth layers.

  More specifically, the first layer 33a in contact with the crystalline lens complements that the conductive material constituting the electrode is different in thermal conductivity and thermal expansion coefficient from the crystalline lens, and the conductive material of the crystalline lens and the second layer electrode. It is possible to reinforce the adhesion.

  The third layer 33c compensates for the difference in thermal conductivity and thermal expansion coefficient between the electrode of the second layer 33b and that of the electrode of the fourth layer 33d. The adhesion between the electrode of the layer and the conductive material can be enhanced. Further, it is advantageous from the viewpoint of productivity that the third layer 33c is made of the same material as that of the first layer 33a.

  In the case of the fourth layer 33d, trimming needs to be easily performed so that the frequency can be easily adjusted, and it is advantageous to have oxidation resistance.

  In particular, when an Ag-Pd-Cu alloy is used, the equivalent series resistance (ESR) of the crystal resonator and the thickness of the crystal resonator must be adjusted by appropriately selecting the composition and composition ratio of the alloy.

  In the case of a crystal resonator, when an electrode structure is formed by a plurality of electrode layers, the electrode structure is configured such that each electrode layer is connected in parallel to form one resistor.

According to one embodiment of the present invention, in the case of a crystal resonator having a four-layer electrode structure, the resistance of the first layer is R ₁ , the resistance of the second layer is R ₂ , the resistance of the third layer is R ₃ , When the resistance of the fourth layer is R ₄ , the resistance R of the crystal resonator electrode can be expressed by the following equation.

  When the same overall resistance value is targeted, as the ratio of the thicknesses of the second layer or the fourth layer, which is an electrode layer containing an Au—Pd—Cu alloy, becomes relatively larger, the entire electrode constituting the crystalline lens becomes larger. The thickness is reduced and the electrode has a low resistance. On the other hand, when the ratio of the thickness of the electrode layer containing the Au—Pd—Cu alloy is increased too much, there arises a problem that the adhesion with the substrate is lowered. That is, it is necessary to appropriately adjust the thickness ratio of the electrode layers.

  In other words, it is necessary to appropriately adjust the thicknesses of the intermediate layer and the electrode layer in order to secure a low equivalent series resistance (ESR) and secure the adhesion between the crystalline lens and the electrode layer.

  Hereinafter, the electrode structure of the crystal resonator according to one embodiment of the present invention and the effect of the crystal resonator including the same will be described by comparing the comparative example and the embodiment.

[Comparative Example 1]
In the case of Comparative Example 1, an electrode was formed on one surface of the crystalline lens. Moreover, the electrode was manufactured only by one layer which consists of an Ag-Pd-Cu (APC) alloy.

[Comparative Example 2]
In the case of Comparative Example 2, the first electrode and the second electrode were formed on the upper and lower surfaces of the crystalline lens, respectively. In addition, each of the first electrode and the second electrode was manufactured with a first layer made of chromium and a second layer made of an Ag—Pd—Cu (APC) alloy. The first layer was wet etched using a chrome wet etchant.

[Comparative Example 3]
In the case of Comparative Example 3, the first electrode and the second electrode were formed on the upper and lower surfaces of the crystalline lens, respectively. In addition, each of the first electrode and the second electrode was manufactured with a first layer made of chromium and a second layer made of gold (Au).

[Example]
A two-layer electrode structure is applied to the crystal resonator according to one embodiment of the present invention. In particular, tungsten (W) was used for the first layer, and an Ag—Pd—Cu (APC) alloy was applied for the second layer.

  FIG. 4 is a photograph of the result of a peel test using a tape for Comparative Example 1 in which an electrode layer is formed directly on the upper portion of the lens using an Ag—Pd—Cu (APC) alloy. This is an enlarged photograph of the peel test result.

  Referring to FIGS. 4 and 5, since the adhesive force between the electrode layer using the Ag—Pd—Cu (APC) alloy and the lens is weak, the electrode layer is peeled from the lens when a peeling test is performed using a tape. It can be seen that they are easily separated.

  That is, it can be seen that an electrode layer using an Ag—Pd—Cu (APC) alloy has a lower contact property with the crystalline lens, and therefore an intermediate layer is required between the crystalline lens and the electrode layer.

  In FIG. 6, after forming an intermediate layer using crystalline chromium (Cr), an electrode layer is formed on the upper portion of the intermediate layer using an Ag-Pd-Cu (APC) alloy, and the intermediate layer is subjected to wet etching. This is a photograph of Comparative Example 2).

  Conventionally, chromium (Cr) has been widely used as an intermediate layer, but in the case of an Ag-Pd-Cu (APC) alloy, the components are similar to the wet etching liquid (wet etchant) used for chromium (Cr). Since a wet etchant is used, the electrode layer of the Ag-Pd-Cu (APC) alloy is damaged during the wet etching process of the chromium (Cr) intermediate layer formed on the surface of the lens. Arise.

  That is, when chromium (Cr) is used as the intermediate layer, there is a problem that the electrode layer using the Ag—Pd—Cu (APC) alloy is damaged in the step of etching the intermediate layer. There is a problem that it is difficult to realize a precise fine pattern in the forming process.

  FIG. 7 shows an embodiment of the present invention in which an intermediate layer is formed using tungsten (W) on the upper part of the lens and then an electrode layer is formed using Ag—Pd—Cu (APC) alloy on the upper part of the intermediate layer. This is a picture of a crystal unit.

  As shown in FIG. 7, after forming an intermediate layer using tungsten (W) on the upper part of the crystalline lens, an electrode layer is formed using Ag—Pd—Cu (APC) alloy on the upper part of the intermediate layer. In this case, since the Ag—Pd—Cu (APC) alloy is not damaged even when wet etching is performed, it can be seen that the electrode layer is formed constant unlike FIG.

  FIG. 8 shows Comparative Example 3 in which the electrode layer is made of gold (Au) and the intermediate layer is made of chromium (Cr), the electrode layer is made of an Ag—Pd—Cu (APC) alloy, and the intermediate layer is made of tungsten (W). It is a graph which shows the result of having measured the equivalent series resistance (ESR: Equivalent Series Resistance) of the Example which was made.

  In the case of a quartz resonator, the smaller the value of equivalent series resistance (ESR), the faster the operating time characteristics can be realized and the power loss can be minimized.

  The value of equivalent series resistance (ESR) in the crystal resonator satisfies the following equation.

  ρ represents the specific resistance value of the resistance element, A represents the area of the resistance element, and L represents the length of the resistance element. The equivalent series resistance (ESR) is proportional to the specific resistance characteristic and area of the resistance element and inversely proportional to the length.

  In the equivalent series resistance (ESR) of the crystal resonator, ρ represents a specific resistivity value of the electrode material, W corresponds to the width of the electrode, and t represents the thickness of the electrode. L represents the length of the electrode.

  Therefore, in order to manufacture a crystal resonator having a small equivalent series resistance (ESR), a material having a low specific resistance ρ is selected, the electrode length L is shortened, or the electrode width W is not increased. Don't be.

  When the electrode thickness t is reduced, the equivalent series resistance (ESR) can be reduced, but the deposition cost can be increased. In addition, there is a risk that the cost of the process of etching the electrode to adjust the frequency precisely increases. As the electrode thickness increases, the mechanical vibration characteristics of the lens decrease.

  According to one embodiment of the present invention, the thickness t of the crystal resonator electrode can be adjusted by a desired natural frequency. Although not limited thereto, it may be 1.0 μm or less, and may be adjusted within a range of 0.1 to 1.0 μm depending on a desired natural frequency.

  Therefore, in order to realize a crystal resonator having a low equivalent series resistance (ESR), the electrode length L can be shortened or the electrode width W can be increased.

  On the other hand, in the case of the electrode length L and the electrode width W, there is a possibility of being restricted by the size of the product and the shape of the crystalline lens. Therefore, in order to reduce the equivalent series resistance (ESR), a metal having a small specific resistance ρ can be used as the electrode material.

  Referring to FIG. 8, the ESR of Comparative Example 3 using gold (Au) was measured to be 58.1066 ohm, and the ESR of the Example was measured to be 42.80665 ohm. Therefore, the electrode layer was made of Ag—Pd—Cu ( It can be seen that the ESR characteristic of the example in which the intermediate layer is formed of tungsten (W) with an APC alloy is improved by about 26%.

  This is because the specific resistance of the electrode structure of the example using Ag—Pd—Cu (APC) alloy as the electrode layer and tungsten (W) as the intermediate layer is compared with the intermediate layer formed of chromium (Cr). This is because the overall resistivity is lower than the specific resistance of the example electrode structure.

  That is, an electrode structure of a crystal resonator according to an embodiment of the present invention and a crystal resonator including the same can have improved ESR characteristics compared to a conventional crystal resonator, and a conventional electrode structure using gold. Compared to the above, the manufacturing cost is low, and the adhesive strength between the electrode layer using the Ag—Pd—Cu alloy and the crystalline lens is excellent, so that the reliability and stability are improved.

  The embodiment of the present invention has been described in detail above, but the scope of the present invention is not limited to this, and various modifications and variations can be made without departing from the technical idea of the present invention described in the claims. It is clear to those having ordinary knowledge in the art that

DESCRIPTION OF SYMBOLS 1 Crystal oscillator package 10 Crystal oscillator 11 Crystal 12a, 12b 1st and 2nd electrode 14 Electrode pad 15 Bump 16a Floor layer 16b Support layer 17 Lid

Claims (8)

A lens that vibrates in response to an electrical signal;
An electrode part including a first layer and a second layer disposed on at least one surface of the crystalline lens,
The first layer includes tungsten (W), and the second layer includes an Ag—Pd—Cu (APC) alloy.   2. The crystal resonator according to claim 1, wherein the electrode section has a two-layer electrode structure in which the first layer and the second layer are laminated in order from the crystalline lens.   3. The crystal resonator according to claim 1, wherein a ratio of a thickness of the first layer to a thickness of the electrode portion is 2 to 30%.   4. The crystal resonator according to claim 1, wherein the electrode portion has a structure in which the first layer and the second layer are alternately and repeatedly stacked. 5. A lens that vibrates in response to an electrical signal;
An electrode unit including a first layer, a second layer, a third layer, and a fourth layer disposed on at least one surface of the lens;
The quartz resonator in which the first layer and the third layer include tungsten (W), and the second layer and the fourth layer include an Ag—Pd—Cu (APC) alloy. Including a first layer and a second layer laminated on the main surface of the crystalline lens;
The electrode structure of the crystal unit in which the first layer includes tungsten (W) and the second layer includes an Ag—Pd—Cu (APC) alloy.   The electrode structure of the crystal unit according to claim 6, wherein the first layer functions to improve an adhesive force between the crystalline lens and the second layer.   The electrode structure of the crystal unit according to claim 6 or 7, wherein the first layer and the second layer have a structure in which the first layer and the second layer are repeatedly laminated in order.