JP3903698B2 - Quartz vibrating piece manufacturing method and quartz crystal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a method for manufacturing a crystal vibrating piece housed in a package of a crystal device, and to a crystal device using a crystal vibrating piece by such a manufacturing method.
[0002]
[Prior art]
FIG. 18 is a flowchart simply showing a conventional manufacturing process in the case of manufacturing a crystal resonator element used in a crystal device such as a crystal resonator.
[0003]
In the figure, first, a quartz crystal wafer is formed by cutting a raw quartz crystal obtained by a predetermined crystal growth process as a piezoelectric material that generates vibration by applying a voltage. Then, the quartz wafer is polished to increase the parallelism between the front and back surfaces of the wafer and to adjust to a predetermined thickness. Then, the processed crystal wafer is cut to the size of a chip for forming a crystal vibrating piece, and the cut end surface is polished to obtain a crystal piece (ST1).
[0004]
Next, an electrode film is formed on the surface (both front and back surfaces) of the crystal piece by vapor deposition or the like. That is, an electrode is formed on a crystal piece that is a piezoelectric body, and an excitation electrode and an external electrode for supplying a drive voltage from the outside are connected to the surface of the electrode in order to generate a predetermined vibration. For this purpose, an extraction electrode is provided (ST2).
[0005]
FIG. 19A shows the film structure of the electrode film 8. On the crystal piece 2, Cr is first formed as an underlayer 3 by vapor deposition or the like, and an electrode layer 4 made of, for example, silver is formed thereon as an upper layer.
[0006]
Next, as shown in FIG. 21, the power supply electrode 6 which is an external electrode is joined using solder (ST3), and then annealed to remove internal stress applied up to this joining step. (ST4).
[0007]
Then, the mass of the electrode film 8 formed in ST2 is adjusted, that is, the components of the electrode layer 4 are added and overlapped, or the electrode layer is irradiated with an electron beam, an ion beam, or a laser beam. The frequency is adjusted to remove the metal coating 4 and reduce its mass (ST5). In other words, the actual vibration frequency is adjusted with respect to the desired frequency of the quartz crystal vibrating piece to match the desired vibration performance.
[0008]
When the frequency adjustment is completed, the crystal resonator element is sealed in the package in a vacuum or a nitrogen atmosphere to complete the crystal resonator (ST6). In the case of surface mounting, a crystal resonator is further resin-molded (ST7). At this time, a heating stress is applied to the crystal vibrating piece.
[0009]
[Problems to be solved by the invention]
By the way, in the piezoelectric device using the piezoelectric vibrating piece made by the manufacturing process as described above, as shown in FIG. 20, when the product is in a high temperature environment, for example, an environment of about 125 degrees Celsius, the vibration frequency There was a problem that changed.
[0010]
In this case, the vibration frequency of the piezoelectric vibrating piece changes so as to be low. Thereby, there exists a problem that desired vibration performance cannot be hold | maintained.
[0011]
And the problem in the manufacturing process mentioned above can be considered as a cause of such a fluctuation | variation.
[0012]
That is, it is considered that the process shown in FIG. 21 proceeds when heat is applied to the piezoelectric vibrating piece after the soldering step of the feeding electrode (lead) 6 in ST3 (ST4 to ST7). First, the power supply electrode 6 is joined by diffusion of solder components to the surface of the electrode film 8 by heat. However, when this solder component is placed in a high-temperature environment in the above-described manufacturing process such as ST4 annealing process or ST7 molding process after bonding, as shown by the arrow in FIG. It will spread further.
[0013]
In this case, the diffused solder component increases the weight of the electrode film 8 and changes the frequency as described above, which has an adverse effect.
[0014]
Further, as shown in FIG. 19B, under this high temperature, the chromium component of the underlayer 3 also diffuses into the upper electrode layer 4 in contact therewith to form the diffusion layer 5. The surface of the electrode layer 4 is hardly affected.
[0015]
Here, it has been found that when the high melting point metal component such as chromium is diffused in the electrode layer 4, the diffusion of the solder component can be prevented. However, in the structure of the electrode film 8 as shown in FIG. 19A, the chromium component diffuses only in the vicinity of the region in contact with the underlayer 3, while the solder component is opposite to the side where the underlayer 3 is present. Therefore, the above-described effect of suppressing solder diffusion due to the diffusion of chromium cannot be expected.
[0016]
Therefore, in the electrode film structure shown in FIG. 19A, a method of providing an intermediate layer (not shown) between the base layer 3 and the upper layer 4 and including the chromium component in the intermediate layer is also conceivable.
[0017]
Therefore, specific studies were made on such an attempt. As a result, such an intermediate layer in which a chromium component was mixed with a conductive metal was provided, and the chromium component was sufficiently diffused into the upper layer. In order to suppress the frequency change to about 5 ppm, the chromium content of the intermediate layer needs to be 4 percent or more in terms of atomic weight.
[0018]
However, with such a film structure, the CI (crystal impedance) value increases, so the film thickness must be 150 nm or more. In addition, when the chromium component is sufficiently diffused in the upper layer in order to suppress the frequency change as described above, another problem that the solder flow becomes insufficient occurs.
The present invention eliminates the above-mentioned problems, and sufficiently diffuses and mixes components capable of preventing the diffusion of the solder component in the electrode film, thereby preventing the deterioration of the vibration characteristics, and its manufacturing method, An object of the present invention is to provide a quartz crystal device using a quartz crystal vibrating piece having such characteristics.
[0019]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an excitation electrode to which a drive voltage is applied to the surface of a crystal piece, and a connection electrode connected to the excitation electrode via a lead electrode. On the other hand, a method for manufacturing a crystal vibrating piece to which a feeding electrode for applying an external driving voltage is bonded, wherein the crystal piece is formed from a crystal wafer obtained by cutting a crystal block. An intermediate layer made of a mixed layer of Cu and a conductive metal (Ag or Au), and an intermediate layer formed on the surface of the base layer made of one of Ti, Cr, and Ni. An electrode film provided with an upper layer made of the conductive metal (Ag or Au) is formed, the power feeding electrode is brought into contact with the connection electrode of the electrode film and joined by soldering, and then heat-treated The water before the joining step. While relieving the stress applied to the piece, the material component of the intermediate layer is diffused into the upper layer and deposited on the surface of the upper layer, and the mass of the electrode film is increased or reduced. This is achieved by a method of manufacturing a quartz crystal vibrating piece that is frequency adjusted by performing.
[0020]
According to the configuration of claim 1, the quartz crystal resonator element according to this manufacturing method is provided as a film configuration of the electrode film on the base layer made of one of Ti, Cr, and Ni, and on the base layer. And an intermediate layer made of a mixed layer of conductor metal and an upper layer made of the conductor metal (Ag or Au) provided on the intermediate layer.
[0021]
Then, the power supply electrode is brought into contact with the connection electrode of the electrode film, joined by soldering, and then subjected to heat treatment to relieve the stress applied to the crystal piece until the joining step, and the material of the intermediate layer Components are diffused into the upper layer and deposited on the surface of the upper layer.
[0022]
That is, in the present invention, the component of the underlayer is selected from one of Ti, Cr, and Ni, but these components are not expected to diffuse into the upper layer. In other words, these components are not intended to be diffused in the upper conductive metal and prevent the solder from being diffused, and the underlying layer is suitable for bonding the crystal and the conductive metal. Is selected.
[0023]
On the other hand, as a result of various studies on conditions for actively diffusing effective components other than the refractory metal in the thickness direction of the electrode film, an intermediate layer composed of a mixed layer of the Cu component and the conductor metal is provided. He devised a positive heat treatment after the joining process.
[0024]
That is, placing in a high temperature environment after manufacturing or after forming the electrode film leads to diffusion of the solder component used for bonding into the electrode film as described above. Therefore, the addition of a simple heat treatment process does not solve the problem. The inventors have studied various conditions for preventing the diffusion of solder while introducing a heat treatment step for the diffusion of components other than the refractory metal component, and in the present invention, as described above, This is achieved by devising a heat treatment step in which an intermediate layer is provided on the intermediate layer and the Cu component of the intermediate layer is positively deposited on the electrode layer.
[0025]
Thereby, since there is a Cu component deposited to the surface of the electrode film, it is considered that the Cu component is mixed to the vicinity of the surface of the electrode film. Thus, the solder component is not easily diffused along the surface of the electrode film even in a high temperature environment in the subsequent mounting process and the like, and the diffused solder component does not increase the weight of the electrode film.
[0026]
In addition, since the Cu component mixed so as to be deposited on the surface of the electrode film does not increase the CI value, it is not necessary to take measures for increasing the CI value, which causes another problem other than solder diffusion. Nor.
[0027]
According to the second aspect of the present invention, there is provided an excitation electrode to which a driving voltage is applied to the surface of a crystal piece, and a connection electrode connected to the excitation electrode via a lead electrode. On the other hand, a method for manufacturing a crystal vibrating piece to which a feeding electrode for applying an external driving voltage is bonded, wherein the crystal piece is formed from a crystal wafer obtained by cutting a crystal block. An intermediate layer made of a mixed layer of Cu and a conductive metal (Ag or Au), and an intermediate layer formed on the surface of the base layer made of one of Ti, Cr, and Ni. An electrode film provided with an upper layer made of the conductive metal is formed, and the feeding electrode is brought into contact with the connection electrode of the electrode film by soldering, and at least on the excitation electrode, Forming the outermost layer with Al, then By treating, the stress applied to the crystal piece by the joining step is relaxed, and the material component of the intermediate layer is diffused into the upper layer to be deposited on the surface of the upper layer, and the outermost layer This is achieved by a method of manufacturing a quartz crystal vibrating piece in which Al is diffused into the upper layer and the frequency is adjusted by performing mass increase or mass reduction processing on the surface of the electrode film.
[0028]
According to the configuration of claim 2, the quartz crystal resonator element is provided on the base layer made of one of Ti, Cr, and Ni, and on the base layer, as in the first aspect of the invention. And an upper layer of at least the excitation electrode portion of the electrode film provided on the intermediate layer and having an upper layer made of the conductive metal. The point of having an outermost surface layer is different from that of the first aspect.
[0029]
Here, aluminum (Al) is selected as the outermost surface layer by forming Al on the conductive metal and diffusing Al in the conductive metal (Ag or Au), thereby applying the solder to the conductive metal. Diffusion can be suppressed, the Al component does not accompany an increase in CI value, and a weight layer is formed on the excitation electrode in advance to increase the mass in advance before the frequency adjustment step. This is because it can serve as an adhesive layer with the weight layer.
[0030]
And after forming this outermost surface layer, since it heat-processes actively and the material component of an outermost surface layer is diffused in the said upper layer below it, Cu component is different from the case of Claim 1, The Al component diffuses in the film thickness direction upward from the intermediate layer and downward from the outermost surface layer.
[0031]
As a result, an effect exceeding that of the first aspect is exhibited and diffusion of the solder component to the electrode film (upper layer) is suppressed.
[0032]
According to a third aspect of the present invention, there is provided an excitation electrode to which a driving voltage is applied to the surface of a crystal piece, and a connection electrode connected to the excitation electrode via an extraction electrode. A method for manufacturing a crystal vibrating piece in which a feeding electrode for applying an external driving voltage to an electrode is bonded. The crystal piece is formed from a crystal wafer obtained by cutting a crystal block. On the surface of the crystal piece, an underlayer made of one of Ti, Cr, and Ni, an intermediate layer provided on the underlayer and made of a mixed layer of Cu and a conductor metal (Ag or Au), An electrode film provided on the intermediate layer and having an upper layer made of the conductive metal is formed, the power feeding electrode is brought into contact with the connection electrode of the electrode film and joined by solder, and at least on the extraction electrode And forming an outermost surface layer of Al, In addition, by heat treatment, the stress applied to the crystal piece by the joining step is relieved, and the material component of the intermediate layer is diffused into the upper layer and deposited on the surface of the upper layer, and the outermost surface This is achieved by a method for manufacturing a quartz crystal vibrating piece in which Al in the layer is diffused into the upper layer and the frequency is adjusted by performing mass increase or mass reduction treatment on the surface of the electrode film.
[0033]
According to the configuration of claim 3, the quartz crystal resonator element is provided on the base layer made of one of Ti, Cr, and Ni, and on the base layer, as in the invention of claim 1. An intermediate layer made of a mixed layer of metal and a conductor metal, and an upper layer made of the conductor metal provided on the intermediate layer, and at least on the upper layer of the lead electrode portion of the electrode film The point of having an outermost surface layer made of Al is different from that of the first aspect.
[0034]
And after forming this outermost surface layer, since it heat-processes actively and the material component of an outermost surface layer is diffused in the said upper layer below it, Cu component is different from the case of Claim 1, It diffuses in the direction of film thickness upward from the intermediate layer and downward from the outermost surface layer. In particular, in the third aspect, the outermost surface layer is formed in the lead electrode portion where the power supply electrode as the external electrode is connected to the connection electrode to be joined by solder, and therefore, in a limited path where the solder leads to the excitation electrode. In addition to Cu, Al component is also diffused.
[0035]
As a result, an effect exceeding that of the first aspect is exhibited and diffusion of the solder component to the electrode film (upper layer) is suppressed.
[0036]
The invention according to claim 4 is the structure according to any one of claims 1 to 3, wherein the film thickness of the underlayer is 5 nm or more and 30 nm or less, and the mixing ratio of Cu and conductor metal (Ag or Au) of the intermediate layer However, the atomic ratio of Cu is 30% or more and 60% or less, the film thickness of the upper layer is 20 nm or more and 180 nm or less, and the total film thickness of the upper layer and the intermediate layer is 100 nm or more and 500 nm or less. It is characterized by.
[0037]
In the configuration of claim 4, the film thickness of the underlayer is 5 nm or more and 30 nm or less because if the film thickness is less than 5 nm, the adhesion strength of the electrode film is insufficient, so the film thickness is 30 nm. This is because the CI value rises to an unacceptable range.
[0038]
When Cu (copper) is less than 30 percent by atomic ratio, the solder diffusion preventing effect described later is reduced or lost. If copper exceeds 60 percent by atomic ratio, a change in frequency occurs over time after the product is completed.
[0039]
The reason why the total film thickness of the intermediate layer and the upper layer is 100 nm or more and 500 nm or less is that, in this range, there is no problem with respect to the CI (crystal impedance) value of the product in this range.
[0040]
Furthermore, if the film thickness of only the upper layer is not more than 20 nm, the bonding strength between the connection electrode and the feeding electrode becomes insufficient, and if it exceeds 180 nm, the diffusion of the copper (Cu) component in the film thickness direction may be insufficient. is there.
[0041]
According to a fifth aspect of the present invention, in the structure according to any one of the second to fourth aspects, the film thickness of the outermost surface layer is 5 nm or more and 30 nm or less.
[0042]
According to the structure of Claim 5, unless the thickness of the said outermost surface layer is 5 nm or more, the frequency change reduction effect as mentioned later will not appear. Moreover, since this effect becomes constant when the thickness of the outermost surface layer is 30 nm, this is the upper limit.
[0043]
The invention according to claim 6 is the structure according to any one of claims 1 to 5, wherein the heat treatment temperature is 200 degrees Celsius or more and 300 degrees Celsius or less, and the treatment time is 2 minutes or more and 1.5 hours or less. And
[0044]
According to the configuration of claim 6, if heating is not performed at 200 degrees Celsius or more for 2 minutes or more, stress relaxation in the previous process is difficult and diffusion of a necessary Cu component becomes difficult. When heat-treated for 5 hours or more, the bonding strength of the electrode may be insufficient. According to a seventh aspect of the present invention, there is provided a quartz crystal device in which a quartz crystal vibrating piece in a package is accommodated and sealed, wherein the quartz crystal vibrating piece is excited so that a driving voltage is applied to a surface thereof. An electrode and a connection electrode connected to the excitation electrode via an extraction electrode, and a power supply electrode for applying a driving voltage from the outside is joined to the connection electrode by solder, and the excitation Each electrode film constituting the electrode, the extraction electrode, and the connection electrode is provided on a base layer made of one of Ti, Cr, and Ni, and a mixture of Cu and Ag or Au. And an electrode film provided on the intermediate layer and provided with the upper layer made of Ag or Au, the material component of the intermediate layer being diffused into the upper layer, and the upper layer Precipitate on the surface of the To the surface of the electrode film, and a structure in which the frequency adjustment by performing a mass increase or mass reduction process, the quartz crystal device is achieved.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0046]
FIG. 1 is a perspective view showing a crystal resonator as an example of a crystal device using a crystal resonator element according to an embodiment of the present invention, FIG. 2 is a schematic plan view, and FIG. 3 is a schematic cross-sectional view.
[0047]
In these drawings, the crystal resonator 10 includes a package 12 in which a space portion 12a is formed and a plate-like crystal vibrating piece 11 that is long in one direction and is sealed in the package.
[0048]
The quartz crystal vibrating piece 11 is a plate formed in a strip shape, for example, using quartz. On the quartz vibrating piece 11, an excitation electrode 19 and connection electrodes 13 and 14 are formed in a manufacturing process described later. . The excitation electrode 19 is for applying a driving voltage from the outside to generate a predetermined thickness shear vibration in the crystal based on the piezoelectric action. The excitation electrode 19 and the connection electrode are connected by extraction electrodes 13a and 14a.
[0049]
The excitation electrode 19 is similarly formed on the back surface of FIG. 1, and the connection electrode 14 is connected to the excitation electrode 19 formed on the front surface side via an extraction electrode 14a. The connection electrode 13 is connected to an excitation electrode (not shown) of the same shape formed on the back surface side via an extraction electrode 13a.
[0050]
The package 12 is formed of, for example, a metal material. Specifically, the package 12 is formed of easily processed white or more preferably Kovar, etc., and is formed as a hollow cylinder having a front side open in FIG. 1 and a bottom 23 on the back side. ing.
[0051]
The quartz crystal resonator element 11 is inserted into the space 12a from the open end 18a of the package 12, and at one end thereof, a lead terminal 17 as a power supply electrode drawn from the outside of the package onto the connection electrodes 13,14. , 17, that is, inner leads 17 a, 17 a are joined using solders 15, 16, respectively.
[0052]
The open end 18a of the package 12 is sealed with a plug 18 inserted therein. As shown in FIGS. 2 and 3, the plug 18 is made of a metal ring 18b fitted into the inner peripheral portion of the open end 18a of the package 12, and a glass material or the like disposed inside the ring 18b. And an insulating member 18c.
[0053]
The crystal vibrating piece 11 is supported by a cantilever system by fixing one end side of the crystal vibrating piece 11 through the plug 18 and setting the back side as a free end 21. The insulating member 18c of the plug 18 insulates the lead terminals 17, 17 penetrating therethrough.
[0054]
Thus, the crystal resonator element of the present invention is applied to various crystal devices such as a crystal resonator and a crystal oscillator having an integrated circuit added thereto.
[0055]
Next, a method for manufacturing the crystal vibrating piece 11 will be described.
[0056]
FIG. 4 is a flowchart showing a method for manufacturing a quartz crystal vibrating piece according to the first embodiment of the present invention.
[0057]
First, the raw quartz crystal obtained by a predetermined crystal growth process is cut to form a quartz wafer. Then, the quartz wafer is polished to increase the parallelism between the front and back surfaces of the wafer and to adjust to a predetermined thickness. Then, the processed crystal wafer is cut to the size of a chip for forming a crystal vibrating piece, and the cut end face is polished to obtain a crystal piece 21 (ST10). A state in which the electrode film of the crystal vibrating piece 11 of FIGS. 1 to 3 is not formed is a crystal piece 21.
[0058]
Next, as shown in FIG. 5, an electrode film 25 is formed on the surface (both front and back surfaces) of this crystal piece by vapor deposition or the like. The excitation electrode 19 described in FIG. 1 and connection electrodes 13 and 14 for connecting the excitation electrode and an external electrode for supplying a drive voltage from the outside are provided on the surface of the crystal piece 21 (ST11).
[0059]
FIG. 5 shows the film structure of the electrode film 25. On the crystal piece 11, first, a base layer 22 is formed by evaporation or the like from one of Ti, Cr, and Ni as a base. Here, the use of one of Ti, Cr, and Ni has good adhesion to gold or silver as a conductor metal, and can avoid an increase in CI value without inhibiting the function of the intermediate layer described later. Because of the nature. Next, a mixed layer 23 of a conductor metal and the copper (Cu) is formed on the base layer 22 as an intermediate layer by vapor deposition or the like. Next, an upper layer 24 which is an electrode layer is formed on the intermediate layer 23 by vapor deposition or the like with a conductive metal such as gold (Au) or silver (Ag). In this embodiment, silver is selected for the upper layer 24.
[0060]
Next, after the electrode film 25 is formed, the power supply electrode (inner lead) 17a is brought into contact with the electrode film 25 through the solders 15 and 16 as shown in FIG. Joining (ST12). The solders 15 and 16 may be PbSn as normal solder or SnCu, for example, as lead-free solder. Here, when lead-free solder is used, the influence of lead contamination on the environment does not occur.
[0061]
Further, heat treatment is performed after the bonding (ST13). This heat treatment is performed, for example, by accommodating the crystal piece 21 on which the electrode film 25 is formed in a thermostat.
[0062]
In this case, the heat treatment relaxes the stress applied to the crystal piece 21 until the joining step of ST12 and diffuses the Cu component of the intermediate layer 23 into the upper layer 24 as shown in FIGS. This is carried out in order to deposit as component 26 on the surface of 24.
[0063]
Thereby, in this embodiment, the intermediate | middle layer 23 is provided on the base layer 22, and the Cu component of this intermediate | middle layer 23 is actively diffused to an upper layer direction. Then, as shown in FIGS. 5 and 6, the electrode layer 24 is deposited on the upper electrode layer 24 to form a diffusion mixed layer 27 in which the copper (Cu) component 26 is surely present in the vicinity of the surface. I am doing.
[0064]
Here, as the film formation conditions of the electrode film 25 in ST11, in the present embodiment, preferably, the film thickness of the base layer 22 is 5 nm or more and 30 nm or less, and the intermediate layer 23 is a mixture of copper and a conductive metal such as silver. Regarding the ratio, the atomic ratio of copper is 30% or more and 60% or less, the film thickness of the intermediate layer 22 and the upper layer 24 is 100 nm or more and 500 nm or less, and the film thickness of only the upper layer 24 is 20 nm or more and 180 nm or less. Set to.
[0065]
That is, if the thickness of the underlayer 22 is less than 5 nm, the adhesion strength between the crystal 21 and the intermediate layer 23 is insufficient. This is because if the film thickness of the underlayer 22 exceeds 30 nm, the CI value may increase excessively and exceed the allowable range.
[0066]
In addition, regarding the mixing ratio of copper and silver in the intermediate layer 23, if the copper is less than 30 percent by atomic ratio, the solder diffusion preventing effect described later is reduced or lost. If copper exceeds 60 percent by atomic ratio, a change in frequency occurs over time after the product is completed.
[0067]
In addition, the reason why the total film thickness of the intermediate layer 23 and the upper layer 24 is 100 nm or more and 500 nm or less is that, in this range, there is no problem with respect to the CI (crystal impedance) value of the product in this range. .
[0068]
Furthermore, if the film thickness of only the upper layer 24 is not more than 20 nm, the bonding strength between the connection electrode and the feeding electrode is insufficient, and if it exceeds 180 nm, the diffusion of the copper (Cu) component into the upper layer 24 in FIG. 7 is insufficient. There is a risk.
[0069]
In the heat treatment in ST13, for example, the temperature is 200 degrees Celsius or more and 300 degrees Celsius or less, and the treatment time is 2 minutes or more and 1.5 hours or less.
[0070]
That is, if it is not heated at 200 degrees Celsius or more for 2 minutes or more, it becomes difficult to diffuse the necessary Cu component together with stress relaxation in the previous process. When heat treatment is performed at 300 degrees Celsius or more for 1.5 hours or more, This is because the bonding strength of the electrodes is insufficient.
[0071]
Next, the mass of the electrode film 25 formed in ST11 is adjusted, that is, the component of the electrode layer 24 is further evaporated to further increase the weight, or the electron beam, ion beam, or laser beam is irradiated. In other words, the metal film of the electrode layer 24 is subtly removed to adjust the frequency to reduce its mass (ST14). In other words, the actual vibration frequency is adjusted with respect to the desired frequency of the crystal vibrating piece 11 to match the desired vibration performance.
[0072]
When the frequency adjustment is completed, the quartz crystal resonator element is sealed in the package 12 described with reference to FIG. 1 in a vacuum or a nitrogen atmosphere to complete the quartz crystal resonator (ST15). Then, the crystal unit is resin-molded (ST16).
[0073]
The present embodiment is configured as described above, and after the power supply electrode 17a is brought into contact with the connection electrode 13 of the electrode film 25 and bonded by the solders 15 and 16, the heat treatment of ST13 is performed, and thereby the bonding process is completed. In addition, the stress applied to the crystal piece 21 is relaxed, and the copper (Cu) component of the intermediate layer 23 is diffused into the upper layer 24 and further deposited on the surface thereof.
[0074]
As a result, since there is a copper (Cu) component deposited up to the surface of the upper layer 24 that is the electrode layer, the components of the solder 15 and 16 remain on the surface of the electrode film 25 even in a high temperature environment in the subsequent mounting process or the like. Accordingly, the diffused solder component does not increase in weight of the electrode film 25.
[0075]
In particular, the diffusion mixture layer 27 and the precipitation layer 26 shown in FIG. 6 are formed, so that the conventional solder diffusion at the interface between the underlayer and the upper layer and the interface between the upper layer and the air layer is suppressed. And solder diffusion in the diffusion mixed layer 27 is also suppressed.
[0076]
For this reason, it is effectively prevented that the vibration frequency of the quartz crystal vibrating piece 11 shifts lower than a desired frequency due to an increase in the weight of the electrode film 25.
[0077]
In addition, since the Cu component diffused from the intermediate layer 23 is a component having a low electrical resistance, the diffusion mixed layer 27 in FIG. 6 is an alloy of silver and copper and has a low resistance value. Can be kept low.
[0078]
FIG. 8 is a flowchart showing a method for manufacturing a quartz crystal vibrating piece according to the second embodiment of the present invention. FIG. 9 shows a schematic plan view of the quartz crystal vibrating piece 30 corresponding to the second embodiment. In this figure, the portions denoted by the same reference numerals as those of the quartz crystal vibrating piece 11 in FIGS. The overlapping description is omitted.
[0079]
First, the crystal piece 21 is obtained by the same process as ST10 of FIG. 4 (ST21).
[0080]
Next, as shown in FIG. 10, an electrode film 36 is formed on the surface (front and back surfaces) of this crystal piece by vapor deposition or the like (ST22).
[0081]
10A shows at least the structure 36a of the region of the excitation electrode 19 in the electrode film 36, and FIG. 10B shows the structure 36b of the region other than the excitation electrode 19 in the electrode film 36. .
[0082]
In these figures, first, a base layer 32 made of one of Ti, Cr, and Ni is formed on the crystal piece 21 by vapor deposition or the like. This foundation layer 32 is the same as the foundation layer 22 of the first embodiment.
[0083]
Next, an intermediate layer 33 that is a mixed layer of a conductive metal, for example, gold (Au) or silver (Ag) and copper (Cu) is formed on the base layer 32 by vapor deposition or the like.
[0084]
Next, an upper layer 34 to be an electrode layer is formed. The upper layer 34 is the same as the upper layer of the first embodiment, and is formed of a conductive metal such as gold (Au) or silver (Ag). In this embodiment, silver is selected as the upper layer 34.
[0085]
Further, after the upper layer 34 is formed, as shown in FIG. 12, the power supply electrode (inner lead) 17a is joined via the solders 15 and 16 with the electrode film 36a being in contact therewith. (ST23). The solders 15 and 16 may be PbSn as normal solder or SnCu, for example, as lead-free solder. Here, when lead-free solder is used, the influence of lead contamination on the environment does not occur.
[0086]
Furthermore, in this embodiment, as shown in FIG. 9, the outermost surface layer 35 is further formed on at least the excitation electrode 19 (ST24). The outermost surface layer 34 is formed by vapor deposition or the like by selecting aluminum (Al).
[0087]
Here, aluminum (Al) is selected as the outermost surface layer 35 by depositing Al on the conductor metal and diffusing Al into the conductor metal (Ag or Au), thereby forming the conductor metal of the solder. In order to suppress the diffusion of Al, the Al component does not increase the CI value, and before the frequency adjustment process, a weight layer is formed on the excitation electrode to increase the mass in advance. This is because it can serve as an adhesive layer between the weight layer and the weight layer.
[0088]
That is, in this case, on the excitation electrode 19, the electrode film 36 a has the base layer 32, the intermediate layer 33, the upper layer 34, and the outermost surface layer 35 as shown in FIG. In the electrode portion, the electrode film 36 b has the base layer 32, the intermediate layer 33, and the upper layer 34, and does not have the outermost surface layer 35.
[0089]
Thereafter, heat treatment is performed (ST25). This heat treatment is performed, for example, by accommodating the crystal piece 21 on which the electrode films 36a and 36b are formed in a thermostat.
[0090]
Here, the heat treatment is performed in order to relieve the stress applied to the crystal piece 21 until the bonding step ST23 and to exhibit the action shown in FIGS.
[0091]
In this embodiment, as shown in FIG. 11A, the copper (Cu) component of the intermediate layer 33 is diffused with respect to the upper layer 34 in the region of the excitation electrode 19. At the same time, the aluminum (Al) component of the outermost surface layer 35 diffuses into the upper layer 34, thus forming a diffusion mixed layer 37. Further, the outermost surface layer 35 formed in ST24 exists on the diffusion mixed layer 37.
[0092]
In addition, as shown in FIG. 11B, in the region other than the excitation electrode 19, the copper (Cu) component of the intermediate layer is diffused into the upper layer 34 to form a diffusion mixed layer 37. That is, the upper layer 34 is diffused with a copper (Cu) component to form a diffusion mixed layer 37 and further deposited on the surface thereof to constitute a deposited layer 38.
[0093]
Here, as the film formation conditions of the electrode film of ST22, in the present embodiment, the film thickness of the base layer 32 is preferably 5 nm or more and 30 nm or less, and the mixing ratio of copper and conductor metal such as silver in the intermediate layer 33 is preferable. , The atomic ratio of copper is 30% or more and 60% or less, and the total film thickness of the intermediate layer 32 and the upper layer 34 is 100 nm or more and 500 nm or less, and the film thickness of only the upper layer 34 is 20 nm or more and 180 nm or less. Set.
[0094]
In the heat treatment in ST25, for example, the temperature is 200 degrees Celsius or more and 300 degrees Celsius or less, and the treatment time is 2 minutes or more and 1.5 hours or less.
[0095]
These conditions are the same as in the first embodiment, and the reason is also common.
[0096]
Here, in the present embodiment, the thickness of the outermost surface layer 35 is preferably 5 nm or more and 30 nm or less.
[0097]
That is, unless the thickness of the outermost surface layer 35 is 5 nm or more, a frequency change reducing effect as described later does not appear. Further, since this effect becomes constant when the thickness of the outermost surface layer 35 is 30 nm, this is the upper limit.
[0098]
When the heat treatment of ST25 is completed, frequency adjustment (ST26) is performed, sealing is performed with the package 12 (ST27), and necessary mold processing is performed (ST28). These steps are the same as the corresponding ST14, 15, 16 in the first embodiment.
[0099]
Thus, also in this embodiment, the components of the solders 15 and 16 are not easily diffused along the surfaces of the electrode films 36a and 36b even in a high temperature environment in the subsequent mounting process, and the diffused solder components are not diffused into the electrode film. No increase in weight.
[0100]
In particular, in the region of the excitation electrode 19, as shown in FIG. 11, the outermost surface layer 34 and the diffusion mixed layer 37 are formed, and in the other regions, the diffusion mixed layer 37 and the precipitation layer 38 are formed. In addition, it is possible to suppress the diffusion of solder at the conventional boundary between the upper layer and the air layer and the boundary between the upper layer and the underlayer.
[0101]
For this reason, it is effectively prevented that the vibration frequency of the crystal vibrating piece 11 is shifted lower than a desired frequency due to the increase in weight of the electrode films 36a and 36b.
[0102]
In addition, in this case, since the Cu component diffused from the intermediate layer 33 and the outermost surface layer 35 is a component having a low electric resistance, the diffusion mixed layer 37 is an alloy of silver and copper, and has a low resistance value. Therefore, the CI value can be kept low.
[0103]
In particular, in this embodiment, in ST26, when a weight layer of gold or silver is newly provided on the outermost surface layer 34 by vapor deposition or the like by a weight increase method, as in the conventional case, gold or silver is used. Compared with the case where a weight layer is added to the electrode surface, the adhesion of the weight layer is improved. For this reason, it is possible to prevent the added weight layer from peeling off when the product is used. Furthermore, if the frequency adjustment method using the mass reduction process is used, the frequency change speed can be reduced due to the presence of Al, which is suitable for precise frequency adjustment.
[0104]
FIG. 13 is a flowchart showing a method for manufacturing a quartz crystal resonator element according to the third embodiment of the present invention. FIG. 14 shows a schematic plan view of the quartz crystal vibrating piece 40 corresponding to the third embodiment. In this figure, the portions denoted by the same reference numerals as those of the quartz crystal vibrating piece 11 of FIGS. The overlapping description is omitted.
[0105]
In FIG. 13, the processes of ST31, 32, and 33 are the same as the processes described in ST21, 22, and 23 of FIG.
[0106]
In this embodiment, after the bonding step ST23, as shown in FIG. 15, electrode films are formed on the front and back surfaces of the crystal piece 21. Here, FIG. 15A shows the film structure of the extraction electrode portion of the quartz crystal vibrating piece 40 of FIG. 14, and FIG. 15B shows the film structure of at least the excitation electrode 19 region. Yes.
[0107]
With respect to each of these film structures, the portions denoted by the same reference numerals as those in the second embodiment have the same layer structure, and thus redundant description is omitted.
[0108]
In ST34, in particular, the outermost surface layer 44 is formed on the upper layer 34 of the region of the extraction electrode 14a shown in FIG. 14 (the same applies to the extraction electrode 13a on the back side). In this case, the outermost surface layer 44 is formed of aluminum in the same manner as the outermost surface layer 35 of the second embodiment.
[0109]
Next, heat treatment is performed in ST35. The conditions for this heat treatment are the same as those in ST25 of the second embodiment.
[0110]
The film structure after the heat treatment of ST35 is shown in FIGS. 15 (c) and 15 (d). In this case, FIG. 15C shows the film structure of the extraction electrode portion of the crystal vibrating piece 40 of FIG. 14 after the heat treatment, and FIG. 15D shows the film structure of at least the region of the excitation electrode 19. Is shown.
[0111]
As can be seen from a comparison between FIG. 15A and FIG. 15C, on the extraction electrode 14a (13a), the copper (Cu) component of the intermediate layer 33 diffuses upward in the film thickness direction with respect to the upper layer 34. To do. At the same time, the aluminum (Al) component of the outermost surface layer 44 diffuses downward in the film thickness direction with respect to the upper layer 34, thus forming a diffusion mixed layer 37.
[0112]
Further, as can be seen from a comparison between FIG. 15B and FIG. 15D, in the region of the excitation electrode 19, the copper (Cu) component of the intermediate layer 33 is diffused in the upper layer 34 in the film thickness direction to perform diffusion mixing. Layer 37 is formed. That is, in the upper layer 34, a copper (Cu) component is diffused to form a diffusion mixed layer 37, and the component is deposited on the surface to form a deposited layer 38.
[0113]
Next, frequency adjustment is performed (ST36). This step is particularly important. In this embodiment, the frequency adjustment is performed by, for example, irradiating the diffusion mixed layer 37 in the region of the excitation electrode 19 with an electron beam, an ion beam, or a laser beam. A frequency adjustment is performed to finely remove the metal coating of the layer 37 and reduce its mass.
[0114]
This is due to the following reason.
[0115]
In this embodiment, an outermost surface layer 44 is formed on the surface of the extraction electrode 14a (13a), and this region is formed from the outermost surface layer 44 and the intermediate layer 33 to the upper layer 34 particularly in the film thickness direction. In this way, copper (Cu) and aluminum (Al) components are diffused in the upper and lower directions to prevent the diffusion of solder components. In particular, since solder is applied to the connection electrodes 13 and 14 in FIG. 14, if the portion of the lead electrode 14a (13a) is selectively processed, most of the solder diffusion can be effectively prevented. The same effect as other embodiments is exhibited.
[0116]
On the other hand, since the outermost surface layer 44 is not formed in the region of the excitation electrode 19, it is possible to selectively remove a metal having a high removal efficiency such as an alloy of silver and copper in the diffusion mixed layer 37 in this region. . That is, since there is no tough oxide film (aluminum oxide) made of aluminum in the region of the excitation electrode 19, it is possible to adjust the frequency of the mass reduction method in a short time.
[0117]
Thus, by shortening the frequency adjustment time, it is not necessary to increase the temperature greatly during frequency adjustment, and an excessive frequency change does not occur due to the temperature decrease after completion. It is possible to effectively prevent large fluctuations.
[0118]
When the frequency adjustment is completed, the quartz crystal resonator element is sealed in the package 12 described in FIG. 1 in a vacuum or a nitrogen atmosphere to complete the quartz crystal resonator (ST37). A crystal resonator is resin-molded (ST38).
[0119]
FIG. 16 is a table summarizing samples of quartz crystal resonator pieces manufactured by several manufacturing methods (units of thickness and film thickness are nm). In this table, sample 1 and sample 2 are comparative examples manufactured by a conventional manufacturing method different from the present invention, and all other embodiments of the present invention are applied to other samples. In this table, each sample is shown in detail with the above-described conditions such as each underlayer and intermediate layer applied thereto, and among these samples, the manufacturing method of the first embodiment is applied to samples 3 to 7. However, the conditions are variously changed. Sample 8 is according to the second embodiment, and sample 9 is according to the third embodiment.
[0120]
FIG. 17 shows the results of testing the performance of each sample in FIG.
[0121]
Regarding the aging characteristics tested for 125 hours at 125 degrees Celsius after production, Samples 3 to 9 of the present invention showed a good result that the frequency change was minus 5 ppm or less and Samples 14 and 15 were minus 2 ppm or less. The changes were all as good as 5Ω or less.
The present invention is not limited to the above-described embodiment. Each structure of each above-mentioned embodiment can be abbreviate | omitted, or can be combined arbitrarily arbitrarily.
[0122]
Further, the quartz crystal resonator element and the manufacturing method thereof according to the present invention can be applied not only to the crystal resonator and the crystal oscillator but also to any crystal device using the quartz crystal resonator element.
[0123]
【The invention's effect】
As described above, according to the present invention, a method for manufacturing a quartz crystal vibrating piece that can sufficiently prevent the deterioration of the vibration characteristics by sufficiently diffusing and mixing the components capable of preventing the diffusion of the solder component in the electrode film, It is possible to provide a quartz crystal device using a quartz crystal vibrating piece having such characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example of a crystal resonator as a crystal device according to an embodiment of the present invention.
FIG. 2 is a schematic horizontal cross-sectional view of the crystal resonator of FIG.
3 is a schematic vertical sectional view of the crystal resonator of FIG. 1. FIG.
FIG. 4 is a flowchart for explaining a first embodiment of a method for producing a quartz crystal resonator element according to the invention.
5 is a schematic cross-sectional view showing a film structure of an electrode film by the manufacturing method of FIG.
6 is a schematic cross-sectional view showing the film structure of the electrode film after the heat treatment by the manufacturing method of FIG. 4;
7 is a schematic cross-sectional view showing the principle of diffusion of a refractory metal component of an electrode film by the manufacturing method of FIG.
FIG. 8 is a flowchart for explaining a second embodiment of the method for producing a quartz crystal resonator element according to the invention.
9 is a schematic plan view showing a quartz crystal vibrating piece manufactured by the manufacturing method of FIG. 8. FIG.
10 shows a film structure of an electrode film by the manufacturing method of FIG. 8, (a) a schematic sectional view of a film structure in a region of an excitation electrode, and (b) a schematic sectional view of a film structure in a region other than the excitation electrode.
11 shows a film structure after heat treatment of the electrode film by the manufacturing method of FIG. 8, (a) a schematic cross-sectional view of the film structure in the region of the excitation electrode, and (b) a schematic cross-sectional view of the film structure in the region other than the excitation electrode. Figure.
12 is a schematic cross-sectional view showing the principle of diffusion of copper and Al components in the electrode film by the manufacturing method of FIG.
FIG. 13 is a flowchart for explaining a third embodiment of the method for producing a quartz crystal resonator element according to the invention.
14 is a schematic plan view showing a quartz crystal vibrating piece manufactured by the manufacturing method of FIG.
15A is a schematic cross-sectional view of the film structure of the extraction electrode region of the electrode film by the manufacturing method of FIG. 13, FIG. 15B is a schematic cross-sectional view of the film structure of the region of the excitation electrode, and FIG. The schematic sectional drawing of the film | membrane structure of the area | region of the extraction electrode of the electrode film after the heat processing by a manufacturing method, (d) The schematic sectional drawing of the film | membrane structure of the area | region of the excitation electrode.
FIG. 16 is a table showing sample manufacturing conditions using the manufacturing method according to each embodiment of the present invention and comparative sample manufacturing conditions.
FIG. 17 is a table comparing the performance of each sample in FIG. 16;
FIG. 18 is a flowchart for explaining a conventional method of manufacturing a quartz crystal vibrating piece.
19A and 19B show the structure of an electrode film of a conventional crystal vibrating piece, (a) a schematic cross-sectional view showing the film structure during manufacture, and (b) a schematic cross-section showing changes in the electrode film structure due to thermal effects after manufacture. Figure.
FIG. 20 is a graph showing a state of frequency change due to thermal influence after manufacturing a conventional crystal resonator element;
FIG. 21 is a schematic cross-sectional view showing a state of diffusion of a solder component due to a thermal influence after manufacturing a conventional crystal resonator element.
[Explanation of symbols]
10 Crystal resonator
11 Crystal vibrating piece
12 packages
13 Connection electrode
13a Lead electrode
14 Connection electrode
14a Lead electrode
15 Solder
16 Solder
17a Feed electrode
19 Excitation electrode
21 Crystal fragment
22 Underlayer
23 Middle layer
24 Upper layer (electrode layer)
25 Electrode membrane

Claims (7)

  An excitation electrode to which a drive voltage is applied to the surface of the crystal piece, and a connection electrode connected to the excitation electrode via the extraction electrode, and for applying an external drive voltage to the connection electrode A method of manufacturing a crystal vibrating piece to which a feeding electrode is bonded, wherein the crystal piece is formed from a crystal wafer obtained by cutting a crystal block, and one of Ti, Cr, and Ni is formed on the surface of the crystal piece. An underlayer made of seed, an intermediate layer provided on the underlayer and made of a mixed layer of Cu and Ag or Au, and an upper layer made of Ag or Au provided on the intermediate layer The electrode film is formed, the power supply electrode is brought into contact with the connection electrode of the electrode film and joined by soldering, and then heat treatment is performed to relieve stress applied to the crystal piece until the joining step, The material component of the intermediate layer A quartz crystal vibrating piece manufactured by diffusing into an upper layer and precipitating on the surface of the upper layer, and further adjusting the frequency by performing mass increase or mass reduction processing on the surface of the electrode film. Method.   An excitation electrode to which a drive voltage is applied to the surface of the crystal piece, and a connection electrode connected to the excitation electrode via the extraction electrode, and for applying an external drive voltage to the connection electrode A method of manufacturing a crystal vibrating piece to which a feeding electrode is bonded, wherein the crystal piece is formed from a crystal wafer obtained by cutting a crystal block, and one of Ti, Cr, and Ni is formed on the surface of the crystal piece. An underlayer made of seed, an intermediate layer provided on the underlayer and made of a mixed layer of Cu and Ag or Au, and an upper layer made of Ag or Au provided on the intermediate layer Forming an electrode film, abutting the power feeding electrode on the connection electrode of the electrode film and bonding with solder, and further forming an outermost surface layer of Al on at least the excitation electrode, and then heat-treating By the joining process The stress applied to the crystal piece is relaxed, and the material component of the intermediate layer is diffused into the upper layer to be deposited on the surface of the upper layer, and Al of the outermost surface layer is diffused into the upper layer. A method of manufacturing a quartz crystal vibrating piece, wherein the frequency is adjusted by performing mass increase or mass reduction processing on the surface of the electrode film.   An excitation electrode to which a drive voltage is applied to the surface of the crystal piece, and a connection electrode connected to the excitation electrode via the extraction electrode, and for applying an external drive voltage to the connection electrode A method of manufacturing a crystal vibrating piece to which a feeding electrode is bonded, wherein the crystal piece is formed from a crystal wafer obtained by cutting a crystal block, and one of Ti, Cr, and Ni is formed on the surface of the crystal piece. An underlayer made of seed, an intermediate layer provided on the underlayer and made of a mixed layer of Cu and Ag or Au, and an upper layer made of Ag or Au provided on the intermediate layer Forming an electrode film, abutting the power supply electrode on the connection electrode of the electrode film and joining with solder, and further forming an outermost surface layer of Al on at least the extraction electrode, and then heat-treating Until the joining process Relieving the stress applied to the crystal piece, and diffusing the material component of the intermediate layer into the upper layer and precipitating it on the surface of the upper layer, and diffusing Al of the outermost surface layer into the upper layer, A method of manufacturing a quartz crystal vibrating piece, wherein the frequency is adjusted by performing mass increase or mass reduction processing on the surface of the electrode film.   The film thickness of the underlayer is 5 nm or more and 30 nm or less, the mixing ratio of Cu and Ag or Au of the intermediate layer is 30% or more and 60% or less in terms of Cu, and the film thickness of the upper layer 4. The method for manufacturing a quartz crystal vibrating piece according to claim 1, wherein a thickness of the upper layer and the intermediate layer is not less than 100 nm and not more than 500 nm. .   5. The method for manufacturing a quartz crystal vibrating piece according to claim 2, wherein the film thickness of the outermost surface layer is 5 nm or more and 30 nm or less.   6. The quartz crystal resonator element according to claim 1, wherein a temperature of the heat treatment is 200 degrees Celsius or more and 300 degrees Celsius or less, and a treatment time is 2 minutes or more and 1.5 hours or less. Method. A quartz crystal device in which a quartz crystal vibrating piece in a package is accommodated and sealed, and the quartz crystal vibrating piece is connected to an excitation electrode to which a driving voltage is applied on a surface thereof, and the excitation electrode and an extraction electrode. A power supply electrode for applying an external driving voltage to the connection electrode by soldering.
Each of the electrode films constituting the excitation electrode, the extraction electrode, and the connection electrode is provided on a base layer made of one of Ti, Cr, and Ni, and is provided on the base layer. And an electrode film provided on the intermediate layer and provided with the upper layer made of Ag or Au.
The material component of the intermediate layer is diffused into the upper layer and deposited on the surface of the upper layer, and the frequency adjustment is performed by performing mass increase or mass reduction treatment on the surface of the electrode film. A crystal device characterized by comprising:

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