JP2010177810A - Piezoelectric oscillation device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric oscillation device that has high reliability enough to suppress metal diffusion while a brazing metal material is melted, and to provide a method of manufacturing the same. <P>SOLUTION: A crystal oscillator 1 includes a crystal vibrating plate 2, a package member 3 and a cover 4, wherein the crystal vibrating plate 2 and the package member 3 are electrically and mechanically connected with each other by a brazing metal material 6. A gold-tin alloy is formed inside the brazing metal material 6, and the outer periphery of the brazing metal material 6 gets into gold or gold-rich status. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibration device used in electronic equipment and the like, and a method for manufacturing the piezoelectric vibration device.

  In recent years, piezoelectric vibration devices used for electronic devices and the like have been miniaturized and thinned. For example, taking a crystal resonator as an example of a piezoelectric vibration device, a crystal vibration plate that performs piezoelectric vibration is bonded to the inside of a container body (package member) having an upper opening through a conductive adhesive, and the opening portion is flat. In general, a structure hermetically sealed with a lid of a shape. Here, a metal brazing material is used in place of the adhesive because of the improvement of the change over time of the crystal resonator and the problem of clogging of the adhesive in the adhesive supply nozzle (see, for example, Patent Document 1).

  In the piezoelectric vibration device (crystal oscillator) of Patent Document 1, a crystal piece and an IC chip are electromechanically connected to a container body (package member) by an alloy of gold (Au) and tin (Sn). . In the second embodiment of Patent Document 1, gold and tin are diffused into gold by heating and melting in a high temperature furnace to form an alloy of gold and tin. However, in the above configuration, there is a risk that the molten tin diffuses to the crystal piece side via the extraction electrode drawn from the excitation electrodes on the front and back sides of the crystal piece and reaches the excitation electrode. If tin reaches the excitation electrode by diffusion, the characteristics of the crystal unit will be adversely affected. In addition, when a metal brazing material of gold and tin is heated and melted to form an alloy, a problem of taking in a metal such as an internal wiring conductor (for example, formed of a gold film) around the metal brazing material (so-called “ There is also concern about the “eating out”.

JP 2002-133504

  The present invention has been made in view of the above points, and an object of the present invention is to provide a highly reliable piezoelectric vibration device and a method for manufacturing the piezoelectric vibration device by suppressing metal diffusion during melting of the metal brazing material. Is.

  To achieve the above object, the invention of claim 1 is a piezoelectric vibration device in which a piezoelectric diaphragm and a package member are electromechanically connected by a metal brazing material, and inside the metal brazing material, A gold-tin alloy is formed, and the outer peripheral region of the metal brazing material is in a gold or gold rich state.

  According to the above configuration, since the gold-tin alloy is formed inside the metal brazing material and the outer peripheral region of the metal brazing material is in a gold or gold-rich state, the diffusion of tin when the metal brazing material is melted is prevented. Can be suppressed. Specifically, since the outer peripheral region of the metal brazing material is in a gold or gold-rich state, the gold in the outer peripheral region serves as a barrier and can suppress diffusion of tin around. The “gold-rich” state refers to an alloy state in which the gold ratio is higher than that of the gold-tin eutectic alloy (gold: tin = 80: 20).

  In order to achieve the above object, according to a second aspect of the present invention, the piezoelectric diaphragm and the package member are connected in a gold-tin alloy state inside the metal brazing material. That is, the piezoelectric diaphragm and the package member are electromechanically connected with the outer peripheral region of the metal brazing material being gold or gold rich, and are also electromechanically connected by the gold-tin alloy inside the metal brazing material. It is connected. Thus, since the outer peripheral area of the metal brazing material is gold or gold rich, the gold-tin alloy inside the metal brazing material has a high gold ratio. Since the gold ratio is high, the eutectic point (eutectic temperature) rises and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor. Thereby, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor and to suppress the diffusion of tin to the surroundings.

  In order to achieve the above object, the invention according to claim 3 is a method of manufacturing a piezoelectric vibrating device in which a piezoelectric vibrating plate and a package member are electromechanically connected by a metal brazing material. Alternatively, either one of the package members is composed of two kinds of metals having different melting points, or a metal and an alloy having different melting points, and one metal having a high melting point is the other metal having a low melting point or one metal and the other metal. A second metal brazing material formed of the same material as the one metal is formed on the piezoelectric diaphragm or the package member on which the first metal brazing material is not formed and the first metal brazing material is formed. After the metal brazing material forming step for forming the metal brazing material and the metal brazing material forming step, the first metal brazing material and the second metal brazing material are integrated by heating and melting to join the piezoelectric diaphragm and the package member. And a step, which is a method for manufacturing a piezoelectric vibrating device having.

  According to the above manufacturing method, in the metal brazing material forming step, the first metal brazing material has a structure in which one metal is disposed outside the other metal. The first metal brazing material is composed of two types of metals having different melting points, or a metal and an alloy having different melting points, and the other metal or an alloy of one metal and the other metal is more than one metal. Also has a low melting point. Further, since the second metal brazing material made of the same material as that of one metal is formed, the ratio of the one metal increases in the entire metal brazing material when the metal brazing material is heated and melted. As a result, the eutectic point rises and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor. Therefore, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor. Further, the low melting point metal (the other metal) in the inner region of the first metal brazing material can be prevented from diffusing to the surroundings (specifically, the piezoelectric diaphragm side or the package member side) due to melting.

  According to the above manufacturing method, the first metal brazing material has a structure in which one metal is arranged outside the other metal or an alloy of the one metal and the other metal. After heating and melting, the piezoelectric diaphragm and the package member can be in a state where the outer peripheral region of the metal brazing material is joined with a high ratio of one metal.

  In the joining step, an alloy of the second metal brazing material and the other metal may be formed by heating and melting. By forming the alloy in this way, it is possible to ensure good conduction between the piezoelectric diaphragm and the package member (conduction between the excitation electrode via the internal wiring conductor and the external terminal on the bottom surface of the package member).

  Further, as described above, the outer peripheral region of the metal brazing material is in a state in which the ratio of one metal is high after heating and melting, so the second metal brazing material inside the metal brazing material and the other metal or one metal The alloy of the other metal is in a state where the ratio of the one metal is high. Since the ratio of one metal is high, the eutectic point (eutectic temperature) rises, and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor. To do. Accordingly, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor and to suppress the other metal from diffusing to the surroundings.

  In the metal brazing material forming step, the first metal brazing material may be arranged so that one metal surrounds an outer peripheral surface of the other metal or an alloy of the one metal and the other metal. Even in such a configuration, an alloy is formed of the other metal and the second metal brazing material by heating and melting. Since one metal is arranged so as to surround the outer peripheral surface of the other metal or the alloy of one metal and the other metal, the outer peripheral region of the metal brazing material has a high ratio of one metal after heating and melting. Thus, the alloy of the second metal brazing material inside the metal brazing material and the other metal can be brought into a state in which the ratio of one metal is high. Since the ratio of one of the metals is increased in this way, the eutectic point (eutectic temperature) rises and before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor, Melting is complete. Accordingly, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor and to suppress the other metal from diffusing to the surroundings.

  In the metal brazing material forming step, the first metal brazing material may be arranged so that one metal covers the other metal or an alloy of one metal and the other metal. In such a configuration, since one metal is also present on the upper surface of the other metal or one metal and the other metal alloy of the first metal brazing material, for example, a piezoelectric diaphragm by ultrasonic application and The following effects can be obtained even when temporarily bonding the package member. That is, since the upper surface of the first metal brazing material is covered with one metal and is made of the same element as the second metal brazing material, an ultrasonic wave and a load are applied to temporarily connect the piezoelectric diaphragm and the package member. When the stop bonding is performed, the metal atoms are easily bonded to each other, and the temporary bonding can be performed by applying a weak load. That is, less load is required than when dissimilar metals are temporarily bonded. Thereby, it is possible to suppress the “slip” of the member at the time of temporary bonding by applying ultrasonic waves.

  The one metal and the second metal brazing material are preferably metals that are difficult to form oxides on the surface and that are rich in malleability. As an example, gold is preferable.

  In the metal brazing material forming step, the first metal brazing material is arranged so that one metal covers the other metal or an alloy of one metal and the other metal, and the other metal or the one metal The width of one metal covering the side portion of the other metal or the alloy of one metal and the other metal is larger than the thickness of one metal covering the upper surface portion of the alloy of the metal and the other metal. It may be formed large.

  If it is the said structure, the width | variety of one metal which coat | covers the side part of the other metal or one metal and the other metal alloy is the upper surface part of the other metal or one metal, and the other metal alloy. Is formed to be larger than the thickness of one of the metals covering the metal, the effect of suppressing the diffusion of the other metal in the lateral direction (horizontal direction) can be further enhanced. In addition to forming one metal with the same width on both outer sides of the other metal or one metal and the alloy of the other metal, the side of the other metal or one metal and the other metal alloy One metal may be formed so as to have different widths on both outer sides. In this case, for example, by disposing the metal brazing material so that the width of one metal on the side close to the excitation electrode is increased, the diffusion of the other metal in the inner direction of the piezoelectric vibration device is more effectively suppressed. I can.

  As described above, according to the present invention, it is possible to provide a highly reliable piezoelectric vibration device and a method for manufacturing the piezoelectric vibration device by suppressing metal diffusion during melting of the metal brazing material.

1 is a schematic cross-sectional view of a crystal resonator showing a first embodiment of the present invention. The A section enlarged view of FIG. The elements on larger scale of the quartz-crystal diaphragm and lower package member in the 1st Embodiment of this invention. The cross-sectional schematic diagram of the crystal oscillator which shows the 2nd Embodiment of this invention. The B section enlarged view of FIG. The elements on larger scale of the crystal diaphragm and lower package member in the 2nd Embodiment of this invention. The cross-sectional schematic diagram of the 1st metal brazing material in the 2nd Embodiment of this invention.

-First embodiment-
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the embodiment of the present invention, a description will be given by taking as an example a crystal resonator in which a crystal plate is used as a piezoelectric vibration plate.
FIG. 1 is a schematic cross-sectional view of a crystal resonator showing a first embodiment of the present invention. The crystal resonator 1 is a piezoelectric vibration device having a rectangular shape in plan view and a substantially rectangular parallelepiped shape, and includes a crystal vibration plate 2 and a lower package member 3 that accommodates the crystal vibration plate 2 therein (hereinafter abbreviated as a base in the present embodiment). The upper package member 4 that hermetically seals the opening of the base 3 (hereinafter abbreviated as a lid in the present embodiment) is a main component. The upper surface of the bank portion 30 of the base 3 made of ceramic and the outer peripheral portion of the metal lid 4 are joined via a joining material 5. The internal space 10 is formed by joining the lid and the base, and the crystal diaphragm 2 is accommodated in the internal space 10. Specifically, the crystal diaphragm 2 is in an electromechanical connection with the base 3 by a metal brazing material 6.

  The base 3 is a box-shaped body made of a ceramic fired body, and has a rectangular shape in plan view. A pair of mounting pads 7 and 7 made of metal is formed at a position near one end of the inner bottom surface 301 of the base 3. On the bottom surface 302 of the base 3, external terminals 34 are formed that are joined to an external device or the like by solder or the like. The mounting pad 7 and the external terminal 34 are electrically connected by an internal wiring conductor (not shown). The mounting pad 7 is formed by laminating tungsten and nickel in this order on the ceramic sheet by a printing technique. A pillow 8 made of an insulating material is formed on the inner bottom surface 301.

  The quartz diaphragm 2 is an AT-cut quartz plate having a rectangular shape in plan view, and a pair of excitation electrodes 23 and 23 for driving the quartz plate are formed on the front and back main surfaces (21 and 22), respectively. A pair of extraction electrodes 24 and 24 are formed on the front and back main surfaces (21 and 22) from the excitation electrode 23, respectively. The extraction electrode 24 on the one main surface 21 side of the crystal plate extends to the end of the one main surface 21, and the extraction electrode 24 on the other main surface 22 side of the crystal plate extends from the end of the other main surface 22 to the crystal plate. It is routed to the end of the one main surface 21 via the side end of the. These extraction electrodes have a positional relationship that does not overlap in plan view, and are each extracted to the vicinity of both ends of one short side of the quartz plate. FIG. 1 is a cross-sectional view taken along a straight line passing through the extraction electrode 24 on the other main surface 22 side in the long side direction of the crystal unit.

  The terminal portion of the extraction electrode 24 of the crystal diaphragm and the mounting pad 7 of the base are joined by the metal brazing material 6, and an enlarged view of a portion A in FIG. 1 is shown in FIG. As shown in FIG. 2, a gold-tin alloy (AuSn) is formed inside the metal brazing material 6, and the outer peripheral region of the metal brazing material is a gold (or gold rich) region. The inventors consider that an intermetallic compound of gold (Au) and tin (Sn) or the like is formed in a region between the gold (outer peripheral region) and the gold-tin alloy region. The above-mentioned “gold rich” means an alloy state in which the gold ratio is higher than that of the gold-tin eutectic alloy (Au: Sn = 80: 20).

  As shown in FIG. 2, the region where the gold-tin alloy (AuSn) is formed is vertically formed inside the metal brazing material 6 so as to connect the extraction electrode 24 and the mounting pad 7. And good conduction between the base and the base (conduction between the excitation electrode via the internal wiring conductor and the external terminal on the bottom of the base) can be ensured.

  Further, according to the above configuration, the gold-tin alloy is formed inside the metal brazing material 6 and the outer peripheral region of the metal brazing material is in a gold or gold-rich state. Diffusion can be suppressed. Specifically, since the outer peripheral region of the metal brazing material is in a gold or gold-rich state, the gold in the outer peripheral region serves as a barrier and can suppress diffusion of tin into the periphery.

  Furthermore, since the outer peripheral area of the metal brazing material 6 is electromechanically connected to the quartz vibrating plate 2 and the base 3 in a gold or gold rich state, the gold-tin alloy inside the metal brazing material has a high gold ratio. It is in a state. By increasing the gold ratio in this way, the eutectic point (eutectic temperature) rises and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal of the surrounding extraction electrode. Accordingly, it is possible to prevent the molten metal brazing material from taking in the metal of the surrounding extraction electrode and to suppress the diffusion of tin to the surroundings.

  Next, the manufacturing method of the crystal resonator according to the first embodiment of the present invention will be described focusing on the process of bonding the crystal diaphragm and the base. FIG. 3 is a partially enlarged view of the crystal diaphragm and the lower package member (base) in the first embodiment of the present invention. A first metal brazing material 61 is formed on the mounting pad 7 formed on the inner bottom surface 301 of the base. A gold flash plating layer 610 is formed on the upper surface of the first metal brazing material 61. Here, the gold flash plating layer 610 is an ultrathin metal thin film formed of gold, and in order to easily perform temporary bonding of the piezoelectric diaphragm and the package member by applying ultrasonic waves in a temporary bonding process described later. Is formed.

(Metal brazing material forming process)
The first metal brazing material 61 is composed of two kinds of metals having different melting points. Specifically, one metal (611) of the high melting point material is formed on the outside, and the other metal (612) of the low melting point material is formed on the inside of the one metal. Here, gold is used for one metal 611 and tin is used for the other metal 612, both of which are formed with a predetermined film thickness by electrolytic plating. Here, on the surface of the other metal 612 (tin), an ultrathin gold strike plating layer (the role of a seed layer when gold is plated on the tin plating layer) (not shown) is formed. Then, a gold flash plating layer 610 is formed on the upper surface of the first metal brazing material 61 by an electrolytic plating method. Here, the thicknesses of the gold flash plating layer and the gold strike plating layer are very thin compared to the formation thickness of one metal and the other metal. On the other hand, as for the quartz diaphragm, a pair of excitation electrodes 23 and a lead electrode 24 are formed on a quartz base plate by a vacuum deposition method, and lead electrodes 24 and 24 drawn to one end on the main surface 21 side of the quartz diaphragm 2. A second metal brazing material 62 is deposited at a predetermined film thickness on the edge of the first metal by electrolytic plating.

(Temporary fixing process)
Next, the crystal diaphragm 2 is temporarily bonded to the base 3 on which the first metal brazing material 61 is formed. Specifically, the crystal vibrating plate 2 is positioned and placed on the base 3 by the image recognition means so that the second metal brazing material 62 substantially coincides with the first metal brazing material 61 in plan view. After the positioning and mounting, an ultrasonic wave is applied while applying pressure while the ultrasonic horn is in contact with the quartz diaphragm. Thereby, the first metal brazing material 61 and the second metal brazing material 62 are temporarily bonded. Note that the gold flash plating layer 610 described above can easily bond the metal atoms by applying a weak load by making the metal of the surface layer the same kind of metal as the second metal brazing material 62 so that the metal atoms are easily bonded. . Further, the gold used for the flash plating layer 610 and the second metal brazing material 62 is suitable for the temporary bonding because it is difficult to form an oxide on the surface and is highly malleable. As described above, the temporary bonding of the same kind of metals requires less load than the case of temporarily bonding the dissimilar metals. Thereby, it is possible to suppress the “slip” of the member at the time of temporary bonding by applying ultrasonic waves.

(Joining process)
After the temporary fixing step, the first metal brazing material 61 and the second metal brazing material 62 are integrated by heating and melting in an atmosphere heated to a predetermined temperature. As a result, the quartz crystal plate 2 and the base 3 are joined (in this embodiment, the quartz plate is cantilevered). At this time, the other metal 612 (tin), which is a low melting point material, diffuses inside the metal brazing material 6 by heating and melting, and one metal 611 (tin) in contact with the other metal 612 (gold) also melts. Then, it diffuses inside the metal brazing material 6. Further, the second metal brazing material 62 adjacent through the gold flash plating layer is also melted and diffused inside the metal brazing material 6. The heating atmosphere is controlled by a temperature profile controlled at a predetermined temperature and a predetermined time and other various conditions, whereby a gold-tin alloy is formed inside the metal brazing material 6, and an outer peripheral region of the metal brazing material 6 is Changes to gold or gold rich state.

  After the joining step, fine adjustment of the frequency is performed by adjusting the mass of the excitation electrode, and the opening in the upper part of the base is hermetically sealed with the lid 4 via the joining material 5. A metal brazing material such as a gold-tin alloy is used for the bonding material 5.

  In the first embodiment of the present invention, in FIG. 3, the formation width of the second metal brazing material 62 is substantially the same as the formation width of the first metal brazing material 61, but is not limited thereto. The formation width of the second metal brazing material 62 and the first metal brazing material 61 may be different. For example, if the formation width of the second metal brazing material 62 is larger than the formation width of the first metal brazing material 61, the crystal plate is positioned and placed on the base (first metal brazing material 61). It can be made easier.

  According to the manufacturing method of the present invention, in the metal brazing material forming step, the first metal brazing material 61 has a structure in which one metal 611 is disposed outside the other metal 612. The first metal brazing material 61 is composed of two types of metals having different melting points, and the other metal 612 has a lower melting point than the one metal 611. Further, since the second metal brazing material 62 made of the same material as that of the one metal 611 is formed, the ratio of the one metal 611 increases in the entire metal brazing material when the metal brazing material is heated and melted. As a result, the eutectic point rises and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal such as the surrounding extraction electrode. Therefore, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding extraction electrode. Further, the low melting point metal (the other metal 612) in the inner region of the first metal brazing material 61 can be prevented from diffusing to the surroundings (specifically, the crystal diaphragm side or the base side) due to melting.

  In addition, according to the manufacturing method of the present invention, the first metal brazing material 61 has a structure in which one metal 611 is disposed outside the other metal 612. The diaphragm and the base can be in a state where the outer peripheral region of the metal brazing material 6 is joined in a gold or gold rich state.

  An alloy of the second metal brazing material and the other metal may be formed by heating and melting. By forming the alloy in this way, it is possible to ensure good conduction between the piezoelectric diaphragm and the package member (conduction between the excitation electrode via the internal wiring conductor and the external terminal on the bottom surface of the package member).

  Further, as described above, since the outer peripheral region of the metal brazing material is in a gold or gold-rich state after heat melting, the gold-tin alloy inside the metal brazing material has a high gold ratio. Since the gold ratio is high, the eutectic point (eutectic temperature) rises and the melting of the metal brazing material is completed before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor. Thereby, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor and to suppress the diffusion of tin to the surroundings.

-Second Embodiment-
The second embodiment of the present invention will be described by taking as an example a crystal resonator using a crystal diaphragm as a piezoelectric diaphragm as in the first embodiment. In addition, about the structure similar to 1st Embodiment, while attaching | subjecting the same number and omitting a part of description, it has an effect similar to the above-mentioned embodiment. Hereinafter, a description will be given focusing on differences from the first embodiment.

  FIG. 4 is a schematic cross-sectional view in the long side direction of a crystal unit showing a second embodiment of the present invention. As shown in FIG. 4, the crystal resonator 1 according to this embodiment includes a lower plate member 3 (hereinafter referred to as “hermetic seal”) that hermetically seals the crystal diaphragm 2 and the excitation electrode 23 formed on one main surface 21 of the crystal diaphragm 2. , And the upper package member 4 (hereinafter abbreviated as the upper lid member) that hermetically seals the excitation electrode 23 formed on the other main surface 22 of the crystal diaphragm 2 are the main constituent members. . The lower lid member 3 and the upper lid member 4 are bonded to the crystal diaphragm 2 via a bonding material 5, respectively.

  The lower lid member 3 is a flat plate having a rectangular shape in plan view, and a Z-plate crystal is used. The lower lid member 3 has a bonding region with the crystal diaphragm 2 in a region near the outer periphery of the one main surface 31 of the lower lid member. One main surface 31 of the lower lid member 3 is a flat and smooth surface (mirror finish), and a bonding material (not shown) is formed in the bonding region. The bonding material is integrated with a metal film formed in the vicinity of the outer periphery of the quartz crystal plate by heating and melting to form the bonding material 5. The bonding material has a structure in which a plurality of metal films are laminated, and is formed by a vapor deposition method in the order of a chromium layer (not shown) and a gold layer (not shown) from the bottom layer side. A plating layer is formed on the gold layer by electrolytic plating in the order of tin (not shown) and gold (not shown). The bonding material may have a film configuration in which a chromium layer and a gold layer are vapor-deposited from the lowermost layer side, and a gold-tin alloy plating layer is laminated thereon.

  An electrode pattern 36 is formed on the inner surface of one main surface 31 of the lower lid member 3 with respect to the bonding region with the quartz crystal diaphragm 2 (see FIG. 5). Of the electrode pattern 36, the portion bonded to the bonding electrode (25) of the crystal diaphragm via the metal brazing material is the bonding electrode 33. The electrode pattern 36 is connected to a through conductor (via) 34 formed so as to penetrate in the thickness direction of the lower lid member, and is connected to an external terminal 35 formed on the other main surface (bottom surface) 32 of the lower lid member 3. In the present embodiment, the electrode pattern 36 has a layer configuration in which a gold layer is formed on the chromium layer by an evaporation method. The electrode pattern 36 and the chromium layer and the gold layer of the bonding material near the outer periphery of the lower lid member are formed simultaneously.

  As shown in FIG. 5, a first metal brazing material 61 is formed on the bonding electrode 33 of the lower lid member. The first metal brazing material 61 is composed of one metal 611 and the other metal 612. One metal 611 is made of gold and the other metal 612 is made of tin, both of which are formed by electrolytic plating. One metal 611 is disposed so as to cover the entire other metal 612. Here, on the surface of the other metal 612 (tin), an ultrathin gold strike plating layer (the role of a seed layer when gold is plated on the tin plating layer) (not shown) is formed. As shown in FIG. 5, the width of one metal 611 covering the side surface portion of the other metal 612 is formed larger than the thickness of one metal 611 covering the upper surface portion of the other metal 612. . The width of one metal 611 surrounding the side surface portion of the other metal 612 is substantially constant. That is, in FIG. 5, the other metal 612 is disposed approximately at the center of the one metal 611 in the width direction.

  In FIG. 4, the quartz crystal plate 2 is an AT cut quartz plate cut out at a predetermined angle. The quartz diaphragm 2 includes a vibrating portion 20 in a thin region where the excitation electrode 23 is formed, a protrusion 26 formed in an outer peripheral region of one main surface 21 of the vibrating portion 20, a thin portion 27, and a frame portion 28. These are integrally formed. Here, the frame portion 28 surrounds the vibrating portion 20 in an annular shape and is formed thicker than the vibrating portion. In addition, the upper surface of the projection part 26 and one main surface of the frame part 28 are shape | molded so that it may be located on substantially the same plane. Further, the thin portion 27 is formed between the vibration portion 20 and the frame portion 28 and is formed thinner than the vibration portion 20.

  The vibration part 20, the protrusion part 26, and the thin part 27 of the crystal diaphragm 2 are formed by wet etching. A pair of excitation electrodes 23 and 23 are formed on the front and back main surfaces (one main surface 21 and the other main surface 22) of the vibration unit 20 so as to face each other by vapor deposition. In the present embodiment, the excitation electrode 23 is formed on the front and back main surfaces of the vibration unit 20 in a chromium and gold film configuration in order from the bottom. The film configuration of the electrode is not limited to this, and other film configurations may be used.

  Lead electrodes 24 are led out from the excitation electrodes 23 on the front and back main surfaces of the crystal diaphragm. The extraction electrode 24 extracted from the excitation electrode 23 on the other main surface 22 side passes through the vibration part 20 in the thickness direction and is led out to the one main surface 21 side. The extraction electrode 24 is led out to the outer portion of the protrusion so as to cover the surface of the protrusion 26 (the protrusion on the left side in FIG. 4). In addition, the conductor part formed in the surface of the protrusion part 26 becomes the joining electrode 25 among extraction electrodes. On the other hand, the extraction electrode 24 extracted from the excitation electrode 23 on the one principal surface 21 side is led out to the outer portion of the protrusion so as to cover the surface of the protrusion 26 (the protrusion on the right side in FIG. 4). In addition, the conductor part formed in the surface of the protrusion part 26 becomes the joining electrode 25 among extraction electrodes. A second metal brazing material 62 (see FIG. 5) is formed on the bonding electrode 25 described above. In the present embodiment, the second metal brazing material 62 is made of gold by electrolytic plating.

  Both main surfaces 21 and 22 of the crystal diaphragm 2 and the front and back main surfaces of the frame portion 28 are mirror-finished and formed as flat smooth surfaces. In the crystal diaphragm 2, the front and back main surfaces of the frame portion 28 are configured as a joint surface between the lower lid member 3 and the upper lid member 4, and the vibration portion 20 is configured as a vibration region. A bonding material (not shown) for bonding to the lower lid member 3 or the upper lid member 4 is formed on the front and back main surfaces of the frame portion 28. Here, the formation widths of the bonding materials formed on the front and back main surfaces of the frame portion 28 are substantially the same and have the same film configuration. In the present embodiment, the bonding materials formed on the front and back main surfaces of the frame portion 28 are each formed with a chromium layer (not shown) and a gold layer (not shown) from the lowermost layer side by vapor deposition, and a gold plating layer thereon (Not shown) has a structure in which the layers are laminated by an electrolytic plating method. In addition, the formation width of the bonding material formed on the front and back main surfaces of the frame portion 28 is substantially the same as the bonding material formed near the outer periphery of each lid member of the lower lid member described above and the upper lid member described later. ing.

  As shown in FIG. 5, the bonding electrode 33 of the lower lid member and the bonding electrode 25 of the crystal diaphragm are bonded via the first metal brazing material 61 and the second metal brazing material 62.

  In FIG. 4, the upper lid member 4 is a flat plate having a rectangular shape in plan view, and a Z-plate crystal is used in the same manner as the lower lid member 3. In a plan view, the outer dimension of the upper lid member 4 is substantially the same as the outer dimension of the crystal diaphragm 2, and the joint surface side of the upper lid member 4 with the crystal diaphragm 2 is a flat smooth surface (mirror finish). . A bonding material (not shown) is formed in a bonding region with the crystal diaphragm 2 near the outer periphery of the upper lid member 4. The bonding material is integrated with a metal film formed in the vicinity of the outer periphery of the quartz crystal plate by heating and melting to form the bonding material 5. The bonding material has a structure in which a plurality of metal films are laminated, and is formed by vapor deposition in the order of a chromium layer (not shown) and a gold layer (not shown) from the lowermost layer side. A plating layer is formed on the gold layer by electrolytic plating in the order of tin (not shown) and gold (not shown). The bonding material may have a film configuration in which a chromium layer and a gold layer are vapor-deposited from the lowermost layer side, and a gold-tin alloy plating layer is laminated thereon.

  Next, a method for manufacturing the crystal unit 1 according to the second embodiment of the present invention will be described with a focus on the process of bonding the crystal diaphragm and the lid member.

  First, a wafer made of Z-plate crystal, in which a large number of the lower lid members are integrally formed, is prepared. Next, at a predetermined position of each lower lid material region formed on one main surface 31 of the wafer, the through conductor 34, a part of the bonding material (chrome and gold) on the lower lid material side, an electrode pattern 36, an external terminal 35 is formed (not shown).

(Metal brazing material forming process)
Then, a tin plating layer and a gold plating layer are formed by electrolytic plating on a part of the bonding material (gold layer) on the lower lid material side. Thereby, the bonding material on the lower lid member side is formed (not shown). On the other hand, one metal and the other metal are formed on the electrode pattern 36 (joining electrode 33) by the electrolytic plating method with a structure as shown in FIG. Thereby, the first metal brazing material 61 is formed. Here, the first metal brazing material 61 is made of two types of metals having different melting points. Specifically, one metal 611 of the high melting point material is formed on the outside, and the other metal 612 of the low melting point material is formed on the inside of the one metal. Here, gold is used for one metal 611, and tin is used for the other metal 612, and one metal 611 is disposed so as to cover the entire other metal 612. Here, the thickness of the gold flash plating layer and the gold strike plating layer is very thin compared to the formation thickness of one metal and the other metal, and in this embodiment the gold flash plating layer is 0.6 to The 1.4 μm gold strike plating layer is formed as a thin film further than the gold flash plating layer.

  The first metal brazing material 61 is formed by first forming tin (the other metal) on the electrode pattern 36 (joining electrode 33) by electrolytic plating. At this time, a masking process is performed using a resist so as not to be plated except in the bonding material forming region on the outer peripheral portion of the bonding electrode and the lower lid member. After the tin plating layer is formed on the bonding electrode, the resist is peeled off to form a resist in which a region for forming one metal of the lower lid member and a bonding material forming region near the outer periphery of the lower lid member are opened. Then, a gold strike plating layer serving as a seed layer is deposited on the surface of the tin plating layer (the other metal) and the resist opening by an electrolytic plating method. In this state, after forming gold (one metal) by electrolytic plating, the resist is peeled off. Thereby, the first metal brazing material 61 is formed.

(Temporary fixing process)
Next, on the bonding material in each lower lid member region of the wafer, the crystal vibrating plates 2, 2,... Is positioned and placed so as to face one main surface 31. At this time, the bonding material of each lower lid member 3 and the bonding material formed on the bonding surface side of the lower lid member of the frame portion 28 of the crystal diaphragm are positioned and placed so as to substantially coincide with each other in plan view. Yes. Further, the first metal brazing material 61 on the joining electrode 33 formed on the one principal surface 31 of the lower lid member 3 and the second metal brazing material 62 formed on the joining electrode 25 of the crystal diaphragm 2 are also seen in a plan view. Positioning is placed so as to substantially match. Then, after positioning and placing, an ultrasonic wave is applied while applying pressure while the ultrasonic horn is in contact with the crystal diaphragm 2. As a result, the first metal brazing material 61 and the second metal brazing material 62, the bonding material of the lower lid member 3, and the bonding material of the frame portion 28 of the crystal diaphragm are temporarily bonded (the lower lid member 3 and the crystal vibration). The plate 2 is temporarily fixed and joined) (not shown).

  Fine adjustment of the frequency by adjusting the mass of the excitation electrode of the crystal diaphragm 2 is performed after the crystal plate and the lower cover member are temporarily fixed and joined. Thereafter, the upper lid member 4 is temporarily bonded to the crystal diaphragm 2. Specifically, the upper cover members 4, 4..., 4 are individually separated by the image recognition means so that one main surface of the upper cover member faces the other main surface 22 of each of the quartz diaphragms temporarily bonded. Position and mount. At this time, the bonding material of each upper lid member 4 and the bonding material on the bonding surface side of the upper lid member of the frame portion 28 of each crystal diaphragm are positioned and placed so as to substantially coincide with each other in plan view. Then, after positioning and mounting the upper lid member on the crystal diaphragm, ultrasonic waves are applied while applying pressure while the ultrasonic horn is in contact with the upper lid member. As a result, the upper lid member 4 and the crystal diaphragm 2 are temporarily bonded (not shown).

(Joining process)
After the temporary fixing step, the first metal brazing material 61 and the second metal brazing material 62 are integrated by heating and melting in an atmosphere heated to a predetermined temperature. At the same time, the bonding material formed on each of the crystal diaphragm and each of the upper lid member and the lower lid member is also integrated by the heating and melting. As a result, the upper lid member 4, the crystal diaphragm 2 and the lower lid member 3 are joined (joined). At this time, the other metal 612 (tin), which is a low melting point material, diffuses inside the metal brazing material 6 by heating and melting, and one metal 611 (tin) in contact with the other metal 612 (gold) also melts. Then, it diffuses inside the metal brazing material 6. Further, the second metal brazing material 62 in contact with one metal 611 is also melted and diffused inside the metal brazing material 6. The heating atmosphere is controlled by a temperature profile controlled at a predetermined temperature and a predetermined time and other various conditions, whereby a gold-tin alloy is formed inside the metal brazing material 6, and an outer peripheral region of the metal brazing material 6 is Changes to gold or gold rich state. In the present embodiment, the lower lid member 3, the crystal diaphragm 2 and the upper lid member 4 are temporarily bonded and joined in a vacuum atmosphere. However, the joining is performed in an inert gas atmosphere such as nitrogen. May be.

(Individual process)
After the joining step, the lower lid member connected in the wafer state is cut by dicing. Specifically, a large number of crystal resonators 1, 1,..., 1 are collectively formed by dividing and cutting adjacent crystal resonators of the lower lid member to which the upper lid member and the crystal diaphragm are joined by dicing. Obtained at the same time.

  In the second embodiment of the present invention, an alloy is formed of the other metal and the second metal brazing material by heating and melting. And since one metal is arranged so as to surround the outer peripheral surface of the other metal, the outer peripheral region of the metal brazing material becomes a gold-rich state after heating and melting, and the gold-tin alloy inside the metal brazing material is converted into a gold ratio. Can be in a high state. Since the gold ratio is high in this way, the eutectic point (eutectic temperature) rises, and before the molten metal brazing material takes in the metal such as the surrounding internal wiring conductor (electrode pattern 36), the metal brazing The melting of the material is finished. Thereby, it is possible to prevent the molten metal brazing material from taking in the metal such as the surrounding internal wiring conductor and to suppress the diffusion of tin to the surroundings.

  In the second embodiment of the present invention, the width of one metal covering the side surface portion of the low melting point metal (the other metal) is larger than the thickness of the one metal covering the upper surface portion of the other metal. Is formed. For this reason, the effect of suppressing the diffusion of the low melting point metal (the other metal) in the lateral direction (horizontal direction) can be further enhanced.

-Modification of the second embodiment-
Modifications of the second embodiment of the present invention are shown in FIGS. In FIG. 6, the first metal brazing material 61 is arranged so that one metal 611 covers the entire other metal 612. Here, as in the second embodiment, an ultrathin gold strike plating layer (not shown) is formed on the surface of the other metal 612 (tin).

  As shown in FIG. 7, the width (a, b) of one metal 611 covering the side surface portion of the other metal 612 is larger than the thickness (c) of the one metal 611 covering the upper surface portion of the other metal 612. ) Is larger. The distance (width) from both side surfaces of the other metal 612 to both outer surfaces of the one metal 611 differs between the left and right sides of the other metal metal 612. That is, the dimensions of a and b in FIG. 7 are in a relation of “a <b” in the inequality.

  In FIG. 7, both side surfaces of the other metal 612 have a width (b) of one metal 611 closer to the excitation electrode than a width (a) of one metal 611 far from the excitation electrode. One metal 611 is disposed outside. By arranging one metal 611 in this way, it is possible to more effectively suppress the diffusion of the other metal 612 (low melting point metal) in the internal direction of the crystal unit. That is, the path length to the excitation electrode can be increased by positioning the other metal 612 in the first metal brazing material 61 in a direction further away from the excitation electrode.

  In the second embodiment of the present invention, the vibration part 20 has a reverse mesa shape in which a protrusion part 26 is formed on the outer periphery, and has a structure in which a thin part 27 is formed outside the vibration part 20. The application of the invention is not limited to the above structure. For example, the shape which did not form a thin part but made the inner side of the frame part a flat plate, and provided the through-hole partially may be sufficient. Further, the present invention can be applied to a structure in which no protrusion is formed on the outer periphery of the vibration part.

  In the second embodiment of the present invention, quartz is used as a material for the two package members (upper lid member and lower lid member), but glass or sapphire may be used in addition to quartz.

  In the first and second embodiments of the present invention described above, the first metal brazing material uses gold for one metal, tin for the other metal, and gold for the second metal brazing material. That is, although it is a combination of gold and tin, application of the present invention is not limited to the above combination, and other combinations may be used. That is, it may be a combination of other metals forming the eutectic alloy, for example, a combination of gold and germanium, gold and silicon, silver and germanium, silver and silicon, or the like. The other metal is not limited to a single element metal having a low melting point, but may be an alloy of one metal and the other metal. For example, gold may be used for one metal and gold tin may be used for the other metal.

  In the embodiment of the present invention, a surface-mount type crystal resonator is taken as an example, but other surface-mount type used in electronic devices such as a crystal oscillator in which a crystal resonator is incorporated in an electronic component such as a crystal filter or an integrated circuit. This method can also be applied to a method for manufacturing a piezoelectric vibration device.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  It can be applied to mass production of piezoelectric vibration devices.

DESCRIPTION OF SYMBOLS 1 Crystal resonator 2 Crystal diaphragm 23 Excitation electrode 24 Extraction electrode 25, 33 Joining electrode 3 Lower package member 35 External terminal 4 Upper package member 5 Joining material 6 Metal brazing material 61 1st metal brazing material 611 One metal 612 Other Metal 62 Second metal brazing material 7 Mounting pad

Claims (7)

A piezoelectric vibration device in which a piezoelectric vibration plate and a package member are electromechanically connected by a metal brazing material,
A piezoelectric vibration device, wherein a gold-tin alloy is formed inside the metal brazing material, and an outer peripheral region of the metal brazing material is in a gold or gold-rich state.   2. The piezoelectric vibration device according to claim 1, wherein the piezoelectric vibration plate and the package member are connected in a gold-tin alloy state inside the metal brazing material. A method of manufacturing a piezoelectric vibration device in which a piezoelectric vibration plate and a package member are electromechanically connected by a metal brazing material,
Either one of the piezoelectric diaphragm and the package member is composed of two kinds of metals having different melting points, or a metal and an alloy having different melting points, and one metal having a high melting point is combined with another metal having a low melting point or one metal. Forming a first metal brazing material disposed on the outside of the other metal alloy;
A metal brazing material forming step of forming a second metal brazing material made of the same material as the one metal on a piezoelectric diaphragm or package member in which the first metal brazing material is not formed;
After the metal brazing material forming step, a joining step of joining the piezoelectric diaphragm and the package member by integrating the first metal brazing material and the second metal brazing material by heating and melting,
A method for manufacturing a piezoelectric vibration device.   4. The method of manufacturing a piezoelectric vibration device according to claim 3, wherein an alloy of the second metal brazing material and the other metal is formed by heat melting in the joining step.   In the metal brazing material forming step, the first metal brazing material is arranged such that one metal surrounds an outer peripheral surface of the other metal or an alloy of the one metal and the other metal. The method for manufacturing a piezoelectric vibration device according to claim 3.   In the metal brazing material forming step, the first metal brazing material is arranged so that one metal covers the other metal or an alloy of one metal and the other metal. The method for manufacturing a piezoelectric vibration device according to claim 3. In the metal brazing material forming step, the first metal brazing material is arranged such that one metal covers the other metal or the whole alloy of one metal and the other metal,
One of the other metal or the alloy of one metal and the other metal that covers the side surface portion of the other metal or the alloy of the one metal and the other metal, rather than the thickness of the one metal that covers the upper surface portion. The method for manufacturing a piezoelectric vibration device according to claim 6, wherein the width of the metal is larger.

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