JP2008099143A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device 50 having a discharge protection function for discharging an electrostatic charge into air or a vacuum via a discharge projection due to the discharge reaction of static electricity. <P>SOLUTION: The piezoelectric device 50 has: a crystal oscillating piece 20; an insulating package 51 that mounts the crystal oscillating piece and has first and second external terminals 82; first and second wiring patterns 81 that are formed on the surface of the insulating package and wire the crystal oscillating piece from the first and second external terminals; and the discharge projection 85 that is formed in the first wiring pattern and is formed to the second one. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crystal resonator or crystal oscillator having an electrostatic discharge (ESD) protection function, and more particularly to a piezoelectric device such as a crystal resonator that discharges static electricity into air or vacuum through discharge protrusions.

  Piezoelectric devices using crystal resonator elements are widely used as clock sources for piezoelectric devices such as piezoelectric watches, computers, and mobile phones, or for measuring angular velocity. In recent years, the degree of integration of piezoelectric components has increased, and accordingly, further downsizing of piezoelectric devices has been required. The miniaturization of piezoelectric devices has also weakened electrostatic resistance.

A piezoelectric device must prevent the device from being destroyed by static electricity stored in the human body. For this reason, the ESD test is an HBM (Human Body Model) test. In addition, to prevent the piezoelectric device from being destroyed by static electricity accumulated in the assembly device of the piezoelectric device,
MM (machine model) testing is being conducted. Recently, due to further miniaturization of quartz crystal resonator pieces or piezoelectric devices, rapid charge transfer has occurred when charges charged in the capacitance inherent to the device approach or come into contact with conductors having different potential potentials. (Charged device model) Tests are also being conducted.

The ESD withstand voltage of a piezoelectric device using a crystal vibrating piece is about 500 V, which is a lower value than other piezoelectric parts. For this reason, it is required to improve the ESD withstand voltage of the piezoelectric device. In particular, with the miniaturization of piezoelectric devices, patterns are often destroyed by electrostatic discharge in thin wiring patterns. In addition, a certain type of piezoelectric device, for example, a surface-mount type crystal oscillator, has an electronic component element such as an IC (integrated circuit) element or a capacitor in addition to a crystal vibrating piece. It is necessary to prevent the IC element or the electronic component element in such a piezoelectric device from being destroyed by static electricity.
JP 2001-235497 A

  An object of the present invention is to prevent electrostatic charges in the air or vacuum through discharge protrusions by electrostatic discharge reaction in order to avoid damage to the crystal resonator element or the electronic elements in the piezoelectric device by electrostatic discharge reaction. A piezoelectric device having a discharge protection function for discharging is provided.

A piezoelectric device according to a first aspect includes a crystal vibrating piece, an insulating package having the crystal vibrating piece mounted thereon and having first and second external terminals, and first and second external terminals formed on the surface of the insulating package. First and second wiring patterns that are wired from the first to the crystal vibrating piece, and discharge protrusions that are formed in the first wiring pattern and formed into the second wiring pattern.
According to the above configuration, the charges are canceled out between the electrostatic charges collected at the discharge protrusions and the induced charges in the air or vacuum. That is, the electrostatic charge of the piezoelectric device causes an electrostatic discharge reaction with particles in the air or vacuum through the discharge protrusion. Therefore, the piezoelectric device can sufficiently pass the test even in the HBM test, the MM test, or the CDM test. Further, even in an apparatus in which a piezoelectric device is actually used, the piezoelectric device has electrostatic resistance.

In the piezoelectric device according to the second aspect, the distance between the discharge protrusion and the second wiring pattern is 1 μm to 20 μm.
The minimum interval between the electrode patterns of the quartz crystal resonator element mounted in the piezoelectric device is about 20 μm. For this reason, according to the above configuration, electrostatic charges are not collected on the electrode pattern of the quartz crystal vibrating piece, but are collected on the discharge protrusions having an interval of 1 μm to 20 μm. The electrostatic charge of the piezoelectric device causes an electrostatic discharge reaction with air or vacuum particles through the discharge protrusions, so that the quartz crystal resonator element is less likely to be damaged by the electrostatic charge.

In the piezoelectric device according to the third aspect, the wiring pattern is formed of a conductive paste made of a refractory metal, and this conductive paste is further plated.
According to the above configuration, since the discharge protrusion can be formed of the same material as the external terminal used for the insulating package, the discharge protrusion can be formed without preparing a special material and without increasing a special process. Can be formed. The conductive paste includes tungsten or molybdenum, and is plated with nickel or gold.

In the piezoelectric device according to the fourth aspect, the discharge protrusion has a thickness of 3 μm to 20 μm.
In the electrostatic discharge reaction, electric energy is released by the charge of the discharge protrusion and the induced charge in air or vacuum, and an electromigration phenomenon occurs to raise the temperature of the discharge protrusion. At this time, since the thickness of the wiring pattern is 3 μm to 20 μm, even if there are multiple electrostatic discharge reactions as shown in FIG.

A piezoelectric device according to a fifth aspect is the fourth aspect in which a plurality of discharge protrusions are formed.
Since the wiring pattern has a thickness of 3 μm to 20 μm, a plurality of discharge protrusions are formed, so that the discharge protrusions are unlikely to sublime. However, another discharge projection can be substituted.

According to the piezoelectric device of the sixth aspect, the insulating package has the bottom ceramic layer and the wall ceramic layer, and the discharge protrusion is formed on at least one of the bottom ceramic layer or the wall ceramic layer. .
According to the above configuration, the discharge protrusion can be formed anywhere as long as it has a space on the surface of the insulating package.

In the piezoelectric device according to the seventh aspect, first and second metal layers that are electrically connected to the first and second wiring patterns are formed on the surface of the crystal vibrating piece, and the first metal layer, the second metal layer, Is narrower than the distance between the discharge protrusion and the second wiring pattern.
Electrostatic discharge first occurs at the discharge protrusion with the narrowest interval where electromigration phenomenon is likely to occur. According to the said structure, it is wider than the space | interval of the location in which the discharge protrusion was formed rather than the narrowest space | interval of the 1st metal layer and 2nd metal layer which were formed in the quartz crystal vibrating piece. For this reason, even if a surge of static electricity occurs, electrostatic discharge is generated at the discharge protrusion, and the first metal layer and the second metal layer of the crystal vibrating piece are not affected.

In an eighth aspect, the insulating package mounts an electronic element having electrical continuity with the crystal vibrating piece, has third and fourth external terminals different from the first and second external terminals, and the piezoelectric device is insulated. The third and fourth wiring patterns formed on the surface of the conductive package and wired from the third and fourth external terminals to the electronic element, and the second discharge protrusion formed on the third wiring pattern and formed on the fourth wiring pattern And having.
According to the above configuration, the piezoelectric device on which the electronic element is mounted can cause an electrostatic discharge reaction at the second discharge protrusion so that the electronic element is not destroyed by the electrostatic discharge reaction.

In the piezoelectric device of the ninth aspect, the second discharge protrusion sets the interval between the second discharge protrusion and the fourth wiring pattern in accordance with the electrostatic withstand voltage of the electronic element.
Although the electrostatic withstand voltage varies depending on the type of electronic element, the interval between the second discharge protrusion and the fourth wiring pattern can be adjusted according to the electrostatic withstand voltage.

According to the present invention, the discharge protrusion in the piezoelectric device causes an electrostatic discharge reaction between the electrostatic charge and the induced charge in the air or vacuum. For this reason, the ESD withstand voltage of the piezoelectric device can be improved.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Configuration of crystal unit 50>
Hereinafter, a crystal resonator 50 according to each embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a crystal resonator 50 according to the first embodiment of the present invention. 1A is an overall perspective view, FIG. 1B is a cross-sectional view, and FIG. 1C is a top view with the metal lid 71 removed.

  The surface-mount type crystal unit 50 includes an insulating ceramic package 51 and a metal lid 71 that covers the package of the crystal unit 50. The metal lid 71 is made of Kovar (iron (Fe) / nickel (Ni) / cobalt (Co) alloy). The ceramic package 51 includes a bottom ceramic layer 51a, a wall ceramic layer 51b, and a pedestal bottom ceramic layer 51c, which are pressed from a green sheet using a slurry containing ceramic powder mainly composed of alumina and a binder. . As a material of the ceramic package 51 constituting the package, glass ceramic may be used instead of ceramic powder mainly composed of alumina, or a non-shrinkable glass ceramic substrate may be used. As understood from FIG. 1B, the package constituted by the plurality of ceramic layers 51 a to 51 c forms a cavity 58, and the crystal vibrating piece 20 is mounted in the cavity 58.

  The tuning fork type crystal vibrating piece 20 has an electrode pattern formed on the arm portion 21 and the base portion 29. The wiring pattern of the base portion 29 has an adhesive region 33 that is electrically connected to the conductive adhesive 31. The tuning fork type crystal vibrating piece 20 is bonded with the conductive adhesive 31 so as to be horizontal with the bottom ceramic layer 51a, and generates a predetermined vibration.

  On a part of the upper surface of the pedestal ceramic layer 51c, a wiring layer 81 is formed which is electrically connected to the bonding region 33 of the tuning fork type crystal vibrating piece 20. At least two terminal electrodes 82 formed on the lower surface of the ceramic package 51 are external terminals when surface-mounted on a printed board (not shown). The internal wiring 83 is an electrical conduction portion that connects the wiring layer 81 and the terminal electrode 82. A metallized layer is provided at the upper end of the wall ceramic layer 51 b, and a sealing material 37 made of a low temperature metal brazing material formed on the metallized layer is formed for joining the metal lid 71. The wall ceramic layer 51 b and the metal lid 71 are welded via the sealing material 37.

<Method for Manufacturing Ceramic Package 51>
Next, a method for manufacturing the ceramic package 51 will be described.
A plurality of ceramic layers 51a to 51c having predetermined dimensions are formed from the green sheet. The plurality of ceramic layers 51a to 51c are punched out of the outer shape so as to have dimensions based on a preset compression rate. Next, the plurality of ceramic layers 51a to 51c are laminated and pressure-bonded in a predetermined number of combinations. This lamination process can be performed, for example, by press-bonding at 200 to 250 degrees C for a certain period of time. In this way, the ceramic package 51 having the cavity 58 can be formed. In practice, a large number of ceramic packages 51 are formed at the same time.

  Next, a through-hole 93 for conducting conduction between the front and back surfaces of the ceramic package 51 is formed by laminating and pressing the ceramic package 51. The internal wiring 83 is formed by filling the through holes 93 and the like with a conductive paste made of a refractory metal such as tungsten (W) or molybdenum (Mo). Subsequently, a conductive paste made of a refractory metal is thickly applied to form a wiring layer 81 on the front surface side, a terminal electrode 82 on the back surface side, and a wiring pattern 85 for electrostatic discharge described later. At this stage, the wiring layer 81, the terminal electrode 82, the internal wiring 83, and the electrostatic discharge wiring pattern 85 of the ceramic package 51 are connected to each other. Thereafter, gold (Au) plating is performed on the wiring layer 81, the terminal electrode 82, the internal wiring 83, and the electrostatic discharge wiring pattern 85 by electroplating to function as a wiring or the like.

Next, the ceramic package 51 formed as described above is fired at about 1550 to 1650 degrees C in a hydrogen atmosphere. This firing shrinks the size by about 20% and completes the ceramic package 51 in which the cavity 58, the wiring layer 81, the terminal electrode 82, the internal wiring 83, the wiring pattern 85 for electrostatic discharge, and the like are formed.
<Configuration of tuning fork type crystal vibrating piece 20>

  FIG. 2A is a diagram illustrating the entire configuration of the tuning fork type crystal vibrating piece 20, and FIG. 2B is a cross-sectional view taken along the line BB of one vibrating arm 21 of the tuning fork type crystal vibrating piece 20. The base material of the tuning fork type crystal vibrating piece 20 is formed of a crystal single crystal wafer 10 processed into a Z-cut. In order to obtain the required performance in a small size, as shown in FIG. 2A, the tuning fork type crystal vibrating piece 20 is divided into a bifurcated portion in parallel with a base 29 and upward from the base 29 in FIG. A pair of extending vibrating arms 21 is provided.

  The tuning-fork type crystal vibrating piece 20 is a vibrating piece that transmits a signal at, for example, 32.768 KHz, and is an extremely small vibrating piece. The overall length is about 2.0 mm and the width is about 0.5 mm. Grooves 211 are formed on the front and back surfaces of the vibrating arm 21 of the tuning fork type crystal vibrating piece 20. Two groove portions 211 are formed on the surface of one vibrating arm 21, and two groove portions 211 are similarly formed on the back surface side of the vibrating arm 21. The groove 211 is provided to suppress an increase in CI value.

  The base portion 29 of the tuning fork type crystal vibrating piece 20 is formed substantially in a plate shape. The length of the base 29 with respect to the vibrating arm 21 is about 36%. A first electrode pattern 23 and a second electrode pattern 25 are formed on the vibrating arm 21 and the base 29 of the tuning fork type crystal vibrating piece 20. Both the first electrode pattern 23 and the second electrode pattern 25 have a structure in which a gold (Au) layer of 400 angstroms to 3000 angstroms is formed on a chromium (Cr) layer of 50 angstroms to 700 angstroms. A tungsten (W) layer or a titanium (Ti) layer may be used instead of the chromium (Cr) layer, and a silver (Ag) layer may be used instead of the gold (Au) layer. In some cases, an Al (aluminum) layer is used.

  As shown in FIG. 2A, a first base electrode 23a and a second base electrode 25a are formed on the base 29 of the tuning fork type crystal vibrating piece 20, and a first groove is formed in the groove 211 of the arm 21. An electrode 23d and a second groove electrode 25d are formed, respectively. Further, as shown in FIG. 2B, second side electrodes 25c are formed on both side surfaces of the left arm portion 21 in FIG. First side electrodes 23c are formed on both side surfaces of the right arm 21 (not shown).

The first side electrode 23c and the second side electrode 25c are connected to the base electrode 23a and the base electrode 25a via the first connection electrode 23b and the second connection electrode 25b. The first electrode pattern 23 and the second electrode pattern 25 to be mirrored are also formed on the back surface of the tuning fork type crystal vibrating piece 20. Since the tuning fork type crystal vibrating piece 20 is small, the gap WA between the side electrode 25c and the groove electrode 23d is about 20 μm as shown in FIG. Further, the gap WB between the first connection electrode 23b and the second connection electrode 25b is also about 20 μm . For this reason, the side electrode 25c and the groove electrode 23d are short-circuited, or the first connection electrode 23b and the second connection electrode 25b are short-circuited, and a defective product is likely to appear in the ESD test.

<Wiring pattern for electrostatic discharge>
FIG. 3 is an enlarged view of the ceramic package 51, and shows a wiring pattern for electrostatic discharge in the first embodiment of the crystal unit 50. FIG. 4 shows an electrostatic discharge wiring pattern of the crystal resonator 50 according to the second embodiment. FIG. 5 shows an electrostatic discharge wiring pattern of the quartz resonator 50 according to the third embodiment. FIG. 6 shows an electrostatic discharge wiring pattern of the crystal resonator 150 according to the fourth embodiment. FIG. 7 shows an electrostatic discharge wiring pattern of the crystal oscillator 250 according to the fifth embodiment.

<< Embodiment 1 >>
FIG. 3A is a ceramic package 51 before the crystal vibrating piece 20 is mounted, and is a cross-sectional view taken along the line AA in FIG. 3B is a top view of the ceramic package 51, and FIG. 3C is a cross-sectional view as seen from the CC direction of FIG. 3B.
A wiring layer 81 is formed on the pedestal ceramic layer 51c. The wiring layer 81 is coated with the conductive adhesive 31 when the tuning fork type crystal vibrating piece 20 is mounted. When the application amount of the conductive adhesive 31 is large, one electrode and the other electrode of the tuning fork type crystal vibrating piece 20 may be short-circuited due to the conductive adhesive 31 protruding. In order to prevent this, the wiring layer 81 is formed on the pedestal ceramic layer 51c. The pedestal ceramic layer 51 c prevents the tuning-fork type crystal vibrating piece 20 from tilting and contacting the bottom surface of the cavity 58.

  A pair of wiring patterns 85-1 for electrostatic discharge is formed from the pair of wiring layers 81. The pair of wiring patterns 85-1 extends to the ceramic layer 51a along the pedestal ceramic layer 51c. A wiring pattern 85-1 having comb-like protrusions is formed on the upper surface of the ceramic layer 51 a that is the bottom surface of the cavity 58. The protrusion interval WC of the pair of wiring patterns 85-1 facing each other is 1 μm to 20 μm. The interval WC is preferably 1 μm to 10 μm. The gap WA between the side electrode 25c and the groove electrode 23d of the tuning-fork type crystal vibrating piece 20 or the gap WB between the first connection electrode 23b and the second connection electrode 25b is about 20 μm. For this reason, the protrusion interval WC must be narrower than 20 μm. This is because, when the protrusion interval WC is larger than 20 μm, the electrostatic charge is accumulated not in the wiring pattern 85-1 but in the vicinity of the gap WA or the gap WB of the tuning-fork type crystal vibrating piece 20. The wiring pattern interval WC can be appropriately changed according to the withstand voltage or current withstand determined by the minimum electrode pattern interval of the tuning-fork type crystal vibrating piece 20.

  When the crystal unit 50 comes into contact with a human body or another device, an electrostatic charge is induced in the wiring pattern 85-1 of the comb-like projection. The electrostatic charges are concentrated on the protrusions of the wiring pattern 85-1 of the comb-like protrusions to form an electric field. Since some static charge is accumulated in the wiring pattern 85-1 of the comb-like protrusion, the opposite charge of the particles in the air or vacuum is induced. At this point, an electrostatic discharge reaction occurs between the electrostatic charge of the wiring pattern 85-1 of the comb-like protrusion and the induced charge in the air or vacuum, canceling out the charges carried by both. In other words, the electrostatic charge of the crystal unit 50 causes an electrostatic discharge reaction with particles in the air or vacuum through the wiring pattern 85-1 of the comb-like projection.

  In the electrostatic discharge reaction, the electric charge of the wiring pattern 85-1 of the comb-like protrusion and the induced electric charge in the air or vacuum release electric energy, and an electromigration phenomenon occurs. The discharged electric energy raises the temperature of the wiring pattern 85-1 of the comb-like protrusion. The wiring pattern 85-1 of the comb-like protrusion is formed of a conductive paste made of a high melting point metal such as tungsten or molybdenum, and the thickness thereof is 3 μm to 20 μm. Therefore, the wiring pattern 85-1 of the comb-like protrusion is Due to the high heat generated by the electrostatic discharge reaction, the comb-like projection wiring pattern 85-1 is rarely sublimated. As shown in FIG. 9, there are two surge peaks in the discharge current waveform diagram from the human body, the first peak is the discharge from the hands and arms, and the next peak is the discharge from the trunk. Even for such a plurality of surge peaks, the wiring pattern 85-1 of the comb-like projections can be dealt with many times because of less sublimation.

  Since the wiring pattern 85-1 of the comb-like protrusion is less likely to sublime due to high heat of the electrostatic discharge reaction, the wiring pattern 85-1 may be a wiring pattern having one protrusion. However, when the thickness of the wiring pattern 85-1 of the conductive paste is about 3 μm, the interval between the wiring patterns is not widened by the sublimation of the wiring pattern, so that a plurality of protrusions are formed like comb-shaped protrusions. It is better to be done. In FIG. 3, the wiring pattern 85-1 having a pair of comb-like protrusions is described. However, only one wiring pattern 85-1 may be formed and the other may not have a discharge protrusion. .

<< Embodiment 2 >>
4A is a ceramic package 51 before the crystal vibrating piece 20 is mounted, and is a cross-sectional view taken along the line AA in FIG. 4B. FIG. 4B is a top view of the ceramic package 51.
A wiring layer 81 is formed on the pedestal ceramic layer 51c. On the wiring layer 81, the tuning fork type crystal vibrating piece 20 is bonded and mounted with the conductive adhesive 31 through the bonding region 33.

  A wiring pattern 85-2 having a triangular protrusion extends from the internal wiring 83. Unlike the first embodiment, a wiring pattern for electrostatic discharge is not formed directly from the wiring layer 81. In the first embodiment, the wiring pattern 85-1 must be formed by applying a conductive paste made of a refractory metal on the upper surface and side surfaces of the pedestal ceramic layer 51c, which is difficult to manufacture. However, the wiring pattern 85-2 having triangular protrusions can be easily manufactured because a conductive paste made of a refractory metal may be applied to the surface of the bottom ceramic layer 51a.

  The interval WC between the triangular protrusions of the pair of wiring patterns 85-2 is 1 μm to 20 μm. Preferably, the interval WC is 1 μm to 20 μm. Preferably, the interval WC is 1 μm to 10 μm. This is because if the protrusion interval WC is larger than 20 μm, the electrostatic charge is accumulated not in the wiring pattern 85-2 but in the vicinity of the gap WA or the gap WB of the tuning-fork type crystal vibrating piece 20. The wiring pattern interval WC can be appropriately changed according to the withstand voltage or current withstand determined by the minimum electrode pattern interval of the tuning-fork type crystal vibrating piece 20.

  When the crystal unit 50 comes into contact with a human body or another device, an electrostatic charge is induced in the wiring pattern 85-2 of the triangular protrusion. The electrostatic charges are concentrated on the protrusions of the triangular protrusion wiring pattern 85-2 to form an electric field. Since some static charge is accumulated in the wiring pattern 85-2, the opposite charge of particles in air or vacuum is induced. The wiring pattern 85-2 also has a thickness of 3 μm to 20 μm. Therefore, the triangular projection wiring pattern 85-1 is sublimated due to the high heat generated by the electrostatic discharge reaction generated in the triangular projection wiring pattern 85-2. Few. Thereby, ESD countermeasures for the crystal vibrating piece 20 can be completely performed. The tip of the triangular projection wiring pattern 85-2 is preferably as thick as possible, and may have a thickness of 20 to 40 μm. This is because the tips of the triangular protrusions remain in the thickness direction even after multiple electrostatic discharge reactions.

<< Embodiment 3 >>
FIG. 5A is a ceramic package 51 before the crystal vibrating piece 20 is mounted, and is a cross-sectional view taken along the line AA in FIG. FIG. 5B is a top view of the ceramic package 51. FIG.5 (c) is sectional drawing seen from CC direction of FIG.5 (b).
A wiring layer 81 is formed on the pedestal ceramic layer 51c. On the wiring layer 81, the tuning fork type crystal vibrating piece 20 is bonded and mounted by the conductive adhesive 31 through the bonding region 33.

  A wiring pattern 85-3 having triangular protrusions and comb-like protrusions extends from the internal wiring 83. Unlike the first embodiment, a wiring pattern for electrostatic discharge is not formed directly from the wiring layer 81. The triangular protrusion 85-31 of the wiring pattern 85-3 is formed on the bottom surface in the cavity 58, that is, the top surface of the bottom surface ceramic layer 51a. Further, as shown in FIG. 5C, the comb-like protrusions 85-32 of the wiring pattern 85-3 are formed on the side surface in the cavity 58, that is, on the wall surface ceramic layer 51b. As described above, various protrusions can be provided in a region having a space in the cavity 58. The distance WC between the pair of triangular protrusion wiring patterns 85-31 and the distance WC between the pair of comb-shaped protrusion wiring patterns 85-32 are 1 μm to 20 μm. Preferably, the interval WC is 1 μm to 10 μm. These intervals WC can be appropriately changed depending on the withstand voltage or withstand current determined by the minimum electrode pattern interval of the tuning fork type crystal vibrating piece 20.

  When the comb-like crystal resonator 50 comes into contact with a human body or another device, an electrostatic charge is induced in the wiring pattern 85-2 of the triangular projection or the wiring pattern 85-32 of the comb-like projection. Since some static charge is accumulated in the wiring pattern 85-3, the opposite charge of particles in air or vacuum is induced. The wiring pattern 85-3 also has a thickness of 3 μm to 20 μm. Therefore, the triangular projection wiring pattern 85-1 is sublimated due to the high heat generated by the electrostatic discharge reaction generated in the triangular projection wiring pattern 85-3. Few. Thereby, ESD countermeasures for the crystal vibrating piece 20 can be completely performed.

<< Embodiment 4 >>
FIG. 6 is a drawing of the crystal resonator 150, and the pedestal ceramic layer 51c is not provided. For this reason, the height of the crystal unit 150 can be reduced, which is suitable for downsizing. FIG. 6A is a ceramic package 51 before the crystal resonator element 20 is mounted on the crystal resonator 150, and is a cross-sectional view taken along the line AA in FIG. 6B. FIG. 6B is a top view of the ceramic package 51.
In FIG. 6, the wiring layer 81 is formed on the ceramic layer 51a. An adhesion region 33 of the tuning fork type crystal vibrating piece 20 is adhered and mounted on the wiring layer 81 by the conductive adhesive 31. In this case, since there is no pedestal ceramic layer 51c, it is necessary to prevent the tuning fork type crystal vibrating piece 20 from tilting.

  Since there is no pedestal ceramic layer 51c, a comb-like projection wiring pattern 85-4 is provided at a location where the wiring layer 81 is extended. As described above, the interval WC between the comb-teeth wiring patterns 85-4 can be changed as appropriate according to the withstand voltage or withstand current determined by the minimum electrode pattern interval of the tuning-fork type crystal vibrating piece 20.

<< Embodiment 5 >>
FIG. 7 is a drawing of the crystal oscillator 250, which has an IC chip 41 and electronic component elements 43 and 45 in addition to the tuning-fork type crystal vibrating piece 20. FIG. 7A is a cross-sectional view in which the crystal resonator element 20 is mounted on the crystal resonator 250 and is welded and sealed with the metal lid 71 through the sealing material 37. FIG. 7B is a top view of the ceramic package 51 from which the metal lid 71 has been removed. In particular, FIG. 7B is a diagram showing the positional relationship between the tuning fork type crystal vibrating piece 20, the IC chip 41, and the electronic component elements 43 and 45. is there. FIG. 7C is a diagram showing wiring patterns 81 and 87 of the ceramic package 51 from which the tuning fork type crystal vibrating piece 20, the IC chip 41 and the like are removed, and a wiring pattern 85-5 for electrostatic discharge. The crystal unit 50 or 150 has two terminal electrodes 82. The crystal oscillator 250 has four terminal electrodes 82. Five or more terminal electrodes 82 may be provided for input / output of the IC element 41.

  The IC chip 41 controls an oscillator, for example, and includes an amplifying unit, a temperature compensating unit, and a sensitive unit. Examples of the amplifying means include an amplifying inverter, and the temperature compensating means includes a computing means, a temperature compensation data storage means, a varicap diode, a load capacitor, a resistance means, and the like.

  Examples of the electronic component elements 43 and 45 include capacitors. The capacitor that is the electronic component element 43 is connected, for example, between the IC chip 41 and the external terminal electrode 82 such that one is at the ground potential. This removes a DC component that becomes noise in the output signal. Further, a capacitor, which is another electronic component element 45, is connected between the IC chip 41 and the external terminal electrode 82, and removes high frequency noise superimposed on the power supply voltage supplied to the external terminal electrode 82.

  A pair of wiring patterns 85-51 for electrostatic discharge is formed from the pair of wiring layers 81. The pair of wiring patterns 85-51 extend to the ceramic layer 51a along the pedestal ceramic layer 51c. Then, a triangular projection wiring pattern 85-51 is formed on the upper surface of the ceramic layer 51a which is the bottom surface of the cavity 58. The protrusion interval WC of the pair of wiring patterns 85-51 facing each other is 1 μm to 20 μm. Preferably, the interval WC is 1 μm to 10 μm. The wiring pattern interval WC can be appropriately changed according to the withstand voltage or current withstand determined by the minimum electrode pattern interval of the tuning-fork type crystal vibrating piece 20.

  In addition, a pair of wiring patterns 85-52 for electrostatic discharge is formed from the wiring layer 87 that is conducted to the IC element 41 or the electronic component element 43. The pair of wiring patterns 85-52 forms a triangular projection wiring pattern 85-52 on the upper surface of the ceramic layer 51 a that is the bottom surface of the cavity 58. The protrusion interval WC of the pair of wiring patterns 85-52 is 1 μm to 10 μm. The interval WC between the wiring patterns 85-52 can be appropriately changed according to the withstand voltage or withstand current determined by the minimum electrode pattern interval of the IC element 41, the electronic component element 43, or the electronic component element 45.

  When the crystal unit 50 comes into contact with a human body or another device, electrostatic charges are induced in the wiring pattern 85-51 of the triangular protrusion or the wiring pattern 85-52 of the triangular protrusion (hereinafter collectively referred to as 85-5). The electrostatic charges are concentrated on the protrusions of the triangular protrusion wiring pattern 85-5 to form an electric field. When a certain amount of electrostatic charge is accumulated in the wiring pattern 85-5 of the triangular protrusion, the opposite charge of particles in air or vacuum is induced. At this point, an electrostatic discharge reaction occurs between the electrostatic charge of the triangular protrusion wiring pattern 85-5 and the induced charge in the air or vacuum, canceling out the charges carried by both. In other words, the electrostatic charge of the crystal oscillator 250 causes an electrostatic discharge reaction with particles in the air or vacuum through the wiring pattern 85-5 of the triangular protrusion. Although the IC chip 41 and the electronic component elements 43 and 45 are provided with countermeasures against static electricity, the crystal oscillator 250 of the fifth embodiment has insufficient ESD withstand voltage of the IC chip 41 and the electronic component elements 43 and 45 themselves. It is effective in such cases.

  In the present invention, electrostatic charges in a piezoelectric device such as the crystal resonators 50 and 150 or the crystal oscillator 250 are concentrated on the protrusions of the wiring pattern, thereby preventing the wiring pattern region from being electrically disturbed. Furthermore, air or vacuum charges are attracted to the electric field of the discharge protrusion. When a certain amount of electrostatic charge builds up a strong electric field on the discharge protrusions, they undergo an electrostatic discharge reaction with particles in air or vacuum. The ESD withstand voltage is substantially improved without damaging the tuning fork type crystal vibrating piece 20 or the IC chip 41 in the crystal resonators 50 and 150 or the crystal oscillator 250.

<Manufacturing process of tuning fork crystal unit or crystal oscillator>
FIG. 8 is a flowchart showing all the steps of manufacturing the tuning-fork type crystal resonators 50 and 150 to be ceramic package described with reference to FIGS. The tuning fork type crystal oscillator 250 has almost the same flow if a process for mounting the IC chip 41 and the like is added.
<< Process for Forming External Shape of Quartz Vibrating Piece >>
In step S112, a corrosion resistant film is formed on the entire surface of the quartz single crystal wafer 10 by a technique such as sputtering or vapor deposition. That is, when using the crystal single crystal wafer 10 as a piezoelectric material, it is difficult to directly form a film of gold (Au), silver (Ag), or the like, so that chromium (Cr), titanium (Ti), etc. Is used. That is, in this embodiment, a metal film in which a gold layer is stacked on a chromium layer is used as the corrosion resistant film.

  In step S114, a photoresist layer is uniformly applied to the entire surface of the quartz single crystal wafer 10 on which the chromium layer and the gold layer are formed by a technique such as spin coating. As the photoresist layer, for example, a positive photoresist made of novolak resin can be used.

  Next, in step S116, the quartz single crystal wafer 10 on which the photoresist layer is applied with the pattern of the tuning-fork type quartz vibrating piece 20 drawn on the first photomask is exposed using an exposure apparatus. In step S116, both sides are exposed using i-line exposure light of 365 nm using a double-side exposure apparatus.

  In step S118, the photoresist layer of the crystal single crystal wafer 10 is developed, and the exposed photoresist layer is removed. Furthermore, the gold layer exposed from the photoresist layer is etched using, for example, an aqueous solution of iodine and potassium iodide. Next, the chromium layer exposed by removing the gold layer is etched with, for example, an aqueous solution of ceric ammonium nitrate and acetic acid. The concentration of the aqueous solution, the temperature, and the time of immersion in the aqueous solution are adjusted so that the excess portion is not eroded. Thus, the corrosion resistant film can be removed. Next, wet etching is performed on the quartz material exposed from the photoresist layer and the corrosion-resistant film so that the outer shape of the tuning-fork type quartz vibrating piece 20 is obtained using a hydrofluoric acid solution as an etching solution. This wet etching takes about 6 hours to about 15 hours, although the time varies depending on the concentration, type and temperature of the hydrofluoric acid solution.

In step S120, the tuning-fork type crystal vibrating piece 20 shown in FIG. 2 is formed by removing the photoresist layer and the corrosion-resistant film that are no longer needed.
<< Electrode Formation Process >>
In step S122, the tuning fork type crystal vibrating piece 20 is washed with pure water, and a metal film for forming an excitation electrode or the like as a drive electrode is formed on the entire surface of the tuning fork type crystal vibrating piece 20 by a technique such as vapor deposition or sputtering. . This metal film is composed of a chromium layer as a base and a gold layer. For example, the chromium layer has a thickness of 50 to 700 angstroms and the gold layer has a thickness of 400 to 3000 angstroms.

In step S124, a photoresist is applied to the entire surface by spraying.
In step S126, a second photomask corresponding to the wiring pattern is prepared, and the quartz single crystal wafer 10 on which the photoresist layer is coated with the wiring pattern is exposed. Since this wiring pattern needs to be formed on both surfaces of the tuning fork type crystal vibrating piece 20, in step S126, both surfaces of the tuning fork type crystal vibrating piece 20 are exposed using exposure light. The double-sided exposure device can be used to expose both sides of the quartz crystal vibrating piece 20 at one time. Alternatively, the single-sided exposure device can be used to expose one side of the quartz crystal vibrating piece 20 and turn the quartz crystal vibrating piece 20 over to expose the other side. It can also be exposed.

  In step S128, after the photoresist layer is developed, the exposed photoresist is removed. The remaining photoresist becomes a photoresist corresponding to the wiring pattern. Next, the metal film to be an electrode is etched. That is, the gold layer exposed from the photoresist layer corresponding to the wiring pattern is etched, for example, with an aqueous solution of iodine and potassium iodide, and then the chromium layer is etched, for example, with an aqueous solution of ceric ammonium nitrate and acetic acid. Subsequently, the photoresist is removed in step S130. Through these steps, an excitation electrode or the like is formed on the tuning fork type crystal vibrating piece 20 with an accurate position and electrode width. Then, the tuning fork type crystal vibrating piece 20 is cut out from the crystal single crystal wafer 10. If necessary, it is checked whether or not the connecting portion 28 is cut off outside the end portion of the base portion 29.

<< Frequency adjustment and packaging process >>
Since the tuning-fork type crystal vibrating piece 20 with the electrodes formed is obtained by the steps so far, in step S132, the ceramic on which the wiring pattern having the discharge projections for linear electric discharge shown in FIGS. 3 to 7 is formed. The tuning-fork type crystal vibrating piece 20 is bonded to the package 51 made of the product. Specifically, the tuning fork type crystal vibrating piece 20 is mounted by applying a conductive adhesive 31 to the bonding region 33 of the base 29 of the tuning fork type crystal vibrating piece 20. Thereafter, the conductive adhesive 31 is temporarily cured. Next, the conductive adhesive 31 is fully cured in a curing furnace.

  In step S134, the vibrating arm 21 of the tuning-fork type crystal vibrating piece 20 is further irradiated with laser light to evaporate and sublimate a part of the quartz single crystal wafer 10 or the weight metal of the vibrating arm 21, and the frequency by the mass reduction method. Make adjustments.

  Next, in step S <b> 136, the ceramic package 51 containing the crystal vibrating piece 20 is transferred into a vacuum chamber or the like, and the metal lid 71 is sealed with the sealing material 37. In step S138, the tuning fork crystal unit 50 is finally inspected to check the driving characteristics of the tuning fork type crystal unit 50.

  In the above embodiment, the tuning fork type crystal resonator has been described. However, the present invention is not limited to this, and a crystal resonator having another shape such as a circular shape or a rectangular shape may be used. Although not shown in the drawing, the discharge protrusion may be inclined by 45 degrees or 90 degrees from the Y direction. In the embodiment, the discharge protrusion is formed on the inner side of the package. However, the discharge protrusion may be formed on the outer side of the package instead of the inner side.

The schematic diagram of the crystal oscillator 50 concerning a first embodiment of the present invention is shown. (A) is a diagram showing the overall configuration of the tuning-fork type crystal vibrating piece 20, and (b) is a BB cross-sectional view of one vibrating arm 21 of the tuning-fork type crystal vibrating piece 20. FIG. 3 is a diagram of the first embodiment showing a wiring pattern for electrostatic discharge of the crystal unit 50. FIG. 6 is a diagram of a second embodiment showing a wiring pattern for electrostatic discharge of the crystal unit 50. FIG. 6 is a diagram of a third embodiment showing a wiring pattern for electrostatic discharge of the crystal unit 50; FIG. 10 is a diagram of a fourth embodiment showing a wiring pattern of a package 51 used in the tuning fork type crystal resonator 150. FIG. 10 is a diagram of a fifth embodiment showing a wiring pattern of a package 51 used in a tuning fork type crystal oscillator 250. 5 is a flowchart showing all steps of manufacturing the tuning fork type crystal resonator 50. It is the figure which showed an example of the discharge current waveform of the static electricity from a human body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Crystal single crystal wafer 20 ... Tuning fork type crystal vibrating piece 81 ... Wiring layer 82 ... Terminal electrode 83 ... Internal wiring 85 ... Wiring pattern 50,150 for electrostatic discharge ... Tuning fork type crystal oscillator 250 ... Tuning fork type crystal oscillator WA ... The narrowest gap WB between the side electrode 25c and the groove electrode 23d ... The narrowest gap WC between the first connection electrode 23b and the second connection electrode 25b ... The widest gap in the discharge protrusions of the ceramic package 51

Claims (9)

A crystal resonator element,
An insulating package on which the crystal resonator element is mounted and having first and second external terminals;
First and second wiring patterns formed on the surface of the insulating package and wired from the first and second external terminals to the quartz crystal vibrating piece;
A piezoelectric device having a discharge protrusion formed on the first wiring pattern and formed on the second wiring pattern. 2. The piezoelectric device according to claim 1, wherein an interval between the discharge protrusion and the second wiring pattern is 1 μm to 20 μm. 3. The piezoelectric device according to claim 1, wherein the discharge protrusion is formed of a conductive paste made of a refractory metal, and the conductive paste is plated. The piezoelectric device according to claim 3, wherein the wiring pattern has a thickness of 3 μm to 20 μm. The piezoelectric device according to any one of claims 1 to 4, wherein a plurality of the discharge protrusions are formed. The insulating package includes a bottom ceramic layer and a wall ceramic layer, and the discharge protrusion is formed on at least one of the bottom ceramic layer and the wall ceramic layer. The piezoelectric device according to claim 5. First and second metal layers that are electrically connected to the first and second wiring patterns are formed on the surface of the quartz crystal vibrating piece,
The narrowest distance between the first metal layer and the second metal layer is wider than the distance between the discharge protrusion and the second wiring pattern. The piezoelectric device according to item. The insulating package has a third and a fourth external terminal on which an electronic element having electrical continuity with the quartz crystal vibrating piece is mounted and different from the first and second external terminals,
Third and fourth wiring patterns formed on the surface of the insulating package and wired from the third and fourth external terminals to the electronic element;
The piezoelectric device according to claim 1, further comprising a second discharge protrusion formed on the third wiring pattern and formed on the fourth wiring pattern. The piezoelectric device according to claim 8, wherein the second discharge protrusion sets an interval between the second discharge protrusion and the fourth wiring pattern in accordance with an electrostatic withstand voltage of the electronic element.