JP4051452B2 - Piezoelectric vibrator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibrator such as a quartz vibrator used in an electronic apparatus, and more specifically, to eliminate the adverse effects that occur when melting metal bumps that support a piezoelectric diaphragm.
[0002]
[Prior art]
Since the piezoelectric vibrator, which is an electronic element, is a vibrating body in the piezoelectric vibrator, how to support it is an important factor that determines its electrical characteristics. In particular, a support structure is important for a crystal unit having a high Q value.
[0003]
Conventionally, for example, in a crystal resonator, a crystal diaphragm is supported and fixed to a ceramic package or the like by a conductive resin bonding material. However, the management of the viscosity and the coating amount of the bonding material is cumbersome and easily affected by the surrounding atmosphere, which has been a cause of variations and fluctuations in the electrical characteristics of the crystal unit.
[0004]
In order to solve such problems, for example, Japanese Patent Laid-Open No. 8-8684 discloses a method in which solder bumps or gold bumps are formed on electrode pads and the piezoelectric diaphragm is electromechanically joined by ultrasonic welding. It has been. Since such a joining structure does not use a conductive joining material, it has the advantage that conventional problems such as excessive supply, insufficient supply, and dripping of the joining material do not occur.
[0005]
The ultrasonic welding used here will be described in detail with reference to FIGS. FIG. 11 is a plan view of the crystal diaphragm, and FIG. 12 is a side view as viewed from the short side direction in FIG. 11 and shows a state in which ultrasonic waves are applied by the ultrasonic welding tool T. The quartz diaphragm 8 has excitation electrodes (main electrodes) 81 and 82 (not shown on the back surface 82) formed on the front and back surfaces, and lead electrodes 81a and 82a are provided at one end in the long side direction from each excitation electrode. It is pulled out and formed so as to be turned around on the opposite surfaces. As shown in FIG. 10, connection electrodes 91 and 92 are formed on a base 9 such as a ceramic package, and metal bumps 91a and 92a are formed on part of the connection electrodes. The extraction electrodes 81 a and 82 a are brought into contact with these metal bumps, and ultrasonic waves are applied from the upper surface of the crystal vibrating plate 8 by the ultrasonic welding tool T.
[0006]
The metal bump is melted by an ultrasonic wave, and the extraction electrode and the connection electrode are electrically and mechanically joined. However, a part of the extraction electrode is formed on the upper surface of the quartz diaphragm to which ultrasonic waves are applied, that is, the opposite surface (back surface) of the connection surface. A disconnection accident occurred. Particularly in recent years, along with the miniaturization of the quartz resonator, the electrodes formed on the quartz diaphragm have been made thinner and thinner, and the above-mentioned danger has been increased. Such a problem is also considered to occur in the piezoelectric vibrator described in the above-mentioned Japanese Patent Application Laid-Open No. 8-8684 because the electrodes are formed on the back surface of the connection surface.
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a highly reliable piezoelectric vibrator that prevents damage to electrodes when a metal bump is welded, ensures a good conduction state, and is highly reliable. It is what.
[0008]
[Means for Solving the Problems]
The present invention is intended to ensure a good conduction state in a piezoelectric diaphragm by not directly contacting an ultrasonic welding tool for applying ultrasonic waves and a normal extraction electrode.
[0009]
That is, as shown in claim 1, a base on which a plurality of connection electrodes are formed, and a pair of main electrodes are formed on the front and back, and each extraction electrode extending from the main electrode is connected to each connection electrode. of the piezoelectric vibrating plate made of a rectangular AT-cut crystal plate extending to the connection plane, the joining of all the lead electrodes of the base of the connection electrode and the piezoelectric vibrating plate, wherein the respective connecting electrodes wherein each extraction electrode A piezoelectric vibrator that is formed by welding metal bumps made of wire bumps formed on one or both of them,
The lead electrode is drawn to the back surface at one end in the long side direction of the piezoelectric diaphragm and through the end in the short side direction, and further extended to the vicinity of the central part in the short side direction to form an extension part. Configuration and a configuration in which an extended portion is formed by being drawn out to the back surface through one end portion in the long side direction of the piezoelectric diaphragm and the other end portion in the short side direction, and further to the vicinity of the center portion in the short side direction. The lead electrode is not formed on the opposite surface of each extension part of the piezoelectric diaphragm, and the piezoelectric diaphragm connects each extension part and each connection electrode with metal bumps made of wire bumps. It is characterized by being cantilever supported .
[0010]
The metal bump may be a stud bump (wire bump) made of gold, silver, copper or the like using a wire bonding technique, or may be a bump made of solder. The metal bumps may be welded using a technique such as thermocompression bonding or ultrasonic welding.
[0011]
With the above configuration, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bump, and the reliability of bonding is increased. In addition, since the lead electrode is not formed on the opposite surface (back surface) of the lead electrode connected to the metal bump, the thermocompression bonding tool, the ultrasonic welding tool, etc. do not come into contact with the lead electrode, and the electrode conduction Can be kept in a good state.
[0012]
In addition, as shown in claim 2, a base on which a plurality of connection electrodes are formed, a plurality of main electrodes, and each extraction electrode for leading the main electrodes to the outside are formed, and each extraction electrode is connected to the connection electrode A metal formed on any one or both of the connection electrode and the extraction electrode, with the piezoelectric diaphragm extending on the connection surface of the base plate and the entire connection of the connection electrode of the base and the extraction electrode of the piezoelectric vibration plate The piezoelectric vibrator is formed by welding bumps, and the piezoelectric diaphragm is such that each extraction electrode is drawn out to one end in the long side direction of the piezoelectric diaphragm and is cantilevered by the connection electrode. A protective film that is thicker than each of the extraction electrodes may be formed on the surface opposite to the surface on which the extraction electrodes connected to the metal bumps of the piezoelectric diaphragm are formed. .
[0013]
If the extraction electrode is formed, the protective film may be formed on the upper part. If it is not formed, it may be formed directly on the quartz diaphragm. As the material of the protective film, a thick metal film made of nickel, chromium or the like may be formed on the extraction electrode, or an insulating material such as silicon may be used.
[0014]
According to the second aspect, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bump, and the reliability of the bonding is increased. In addition, since a protective film is formed directly on the extraction electrode and on the quartz plate, the extraction electrode and the quartz oscillation that affect the excitation of the quartz crystal even if an ultrasonic wave is applied to the part using an ultrasonic welding tool. It will not damage the board substrate.
[0015]
As shown in claim 3, a base on which a plurality of connection electrodes are formed , a plurality of main electrodes and each lead electrode for leading the main electrodes to the outside are formed, and the lead electrodes are connected to the connection electrodes. Welding of the metal bumps formed on one or both of the connection electrode and the extraction electrode, and joining all of the piezoelectric diaphragm extending to the base and the connection electrode of the base and the extraction electrode of the piezoelectric vibration plate The lead electrode is extended at one end portion in the long side direction of the piezoelectric diaphragm and through the central portion in the short side direction, and further extending to both ends in the short side direction. The lead electrode is not formed on the opposite surface of each extension part of the piezoelectric diaphragm, and the piezoelectric diaphragm has the metal bumps between the extension parts and the connection electrodes. Can be supported in a cantilevered manner. It may be configured characterized.
[0016]
According to the third aspect of the present invention, the extraction electrode is formed at one end portion in the long side direction of the piezoelectric diaphragm and through the central portion in the short side direction to the back surface and further extending to both ends in the short side direction. The lead electrode is not formed on the opposite surface of each extension part of the piezoelectric diaphragm, and the piezoelectric diaphragm connects each extension part and each connection electrode with a metal bump. it therefore is a structure characterized by being cantilevered by the connection electrode and the extraction electrode can be bonded between the metal by molten metal bumps, increasing the reliability of the junction. In addition, since the extraction electrode is not formed on the opposite surface (back surface) of the extraction electrode connected to the metal bump, the ultrasonic welding tool does not come into contact with the extraction electrode, and the continuity of the electrode is improved. Can keep.
[0017]
According to a fourth aspect of the present invention, the protective film may be made of a metal according to the second aspect of the present invention.
[0018]
According to the fourth aspect of the present invention, the metal as the protective film can be formed by an extension method of the main electrode (excitation electrode) and the extraction electrode (vacuum deposition method or the like). By changing the opening of the vapor deposition window to a vapor deposition mask limited to only the thick film forming portion, it can be formed relatively easily.
[0019]
According to a fifth aspect of the present invention, in each of the above-described structures, a plurality of metal bumps may be formed on at least one of the connection electrodes .
[0020]
According to the fifth aspect of the present invention, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bump, and the reliability of bonding is increased.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4 by taking a surface-mounted crystal resonator as an example. FIG. 1 is an exploded perspective view of a surface-mounted crystal resonator, and FIG. 2 is an internal cross-sectional view of FIG. 1, corresponding to the AA cross section of the crystal diaphragm shown in FIG. FIG. 3 is a plan view of the crystal diaphragm, and FIG. 4 is a side view as seen from the short side direction in FIG. 3, and also shows the configuration of a part of the base.
[0022]
The surface-mount crystal unit includes a ceramic package 1 constituting a base, a crystal diaphragm 2 mounted on and electrically connected to connection electrodes 12 and 13 formed on the ceramic package, and the connection electrodes 12 and 12. 13 and each of the metal bumps 12a and 13a interposed between the quartz diaphragm 2 and a lid 4 for hermetically sealing the quartz diaphragm 2.
[0023]
The ceramic package 1 includes a ceramic base 10 having a concave internal cross section and a circumferential metal layer 11 formed in an opening around the concave shape. Although not shown, the metal layer 11 includes a metallized layer made of tungsten or the like, a lower plating layer made of nickel or the like formed on the metallized layer, and an upper plating made of gold or the like formed on the upper part of the lower plated layer. Consists of layers. In this embodiment, the thickness of each layer is 18 to 20 μm for the metallized layer 11, 6 μm for the lower plating 12, and 1 μm for the upper plating layer 13.
[0024]
Connection electrodes 12 and 13 are formed on the inner bottom surface of the ceramic package 1, and these connection electrodes 12 and 13 are connected to the outside of the package via connection electrodes (not shown) wired inside the ceramic package. 14 and 15 are electrically drawn out to the outside. A plurality of metal bumps 12a and 13a are formed on the upper surfaces of the connection electrodes 12 and 13, respectively. These metal bumps are wire bumps using gold wires. The wire bump is also referred to as a stud bump, and can be obtained by using a wire bonding technique, for example, by heating the tip of a gold wire into a ball shape, connecting to the connection electrode, and then cutting the wire at a portion near the bump.
[0025]
The connection electrodes 12 and 13 are cantilevered with a rectangular crystal diaphragm 3 which is a piezoelectric diaphragm. The quartz diaphragm 3 is a rectangular AT-cut quartz plate, and excitation electrodes 31 and 32 are formed on the front and back surfaces so as to excite thickness-shear vibration. These connection electrodes are connected to the connection electrodes by extraction electrodes 31a and 32a, respectively. It is pulled out to a position corresponding to 12 and 13.
[0026]
More specifically, the extraction electrode 31a is drawn from the upper surface of the quartz plate on which the excitation electrode 31 is formed to one end portion in the long side direction and through the short side direction end portion to the back surface on which the excitation electrode 32 is formed. It is. The extraction electrode 31a extends to the vicinity of the central portion in the short side direction to form an extension portion 31b. The extraction electrode 32a is drawn out to one end portion in the long side direction and the other end portion in the short side direction of the back surface, and extends to the vicinity of the central portion in the short side direction to form an extension portion 32b. Therefore, the back surface (upper surface) of each of the extending portions 31b and 32b is a quartz diaphragm base portion where no electrode is formed.
[0027]
When ultrasonically welding the metal bumps 31 and 32 and the extraction electrode of the quartz diaphragm, the extension portions 31b and 32b are brought into contact with the metal bumps 12a and 13a, and in this state, the back surfaces of the extension portions 31b and 32b. Press the ultrasonic welding tool against the quartz vibrating plate base part and apply static pressure. Then, by vibrating the ultrasonic welding tool T at a predetermined frequency, the metal bumps are melted and the extraction electrodes 31a and 32a and the connection electrodes 12 and 13 are connected.
[0028]
Note that, when the quartz diaphragm is positioned and mounted on the connection electrode, automatic mounting may be performed using an image recognition technique. In this case, it is possible to control the number of bumps, the formation position or the connection electrode as a marker.
[0029]
The lid 2 for hermetically sealing forms a circumferential joint 21 corresponding to the circumferential metal layer 11 on the lower surface of a metal base material 20 such as Kovar. In this embodiment, the joining portion 21 is made of silver brazing, and hermetic sealing is performed by brazing. For hermetic sealing, glass sealing, laser welding, seam welding, or the like may be used.
[0030]
A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a plan view of the crystal diaphragm. FIG. 6 is a side view seen from the short side direction in FIG. 5 and partially shows the structure of the base, but the description of the ceramic package, the lid, etc. is omitted. The same applies to the following embodiments.
[0031]
Excitation electrodes 41 and 42 (the back surface 42 is not shown) are formed on the front and back surfaces of the rectangular crystal diaphragm 4, and each excitation electrode is connected to the long side of the crystal diaphragm by the extraction electrodes 41 a and 42 a. It is pulled out to one end part in the direction and the central part in the short side direction. In addition, the lead electrodes 41a and 42a are each drawn out to the opposite surface of the crystal diaphragm, and on the side in contact with the connection electrode of the ceramic package (base) 5, extended portions 41b that extend to both ends in the short side direction, 42b is formed.
[0032]
A plurality of metal bumps 51a and 52a are formed on the connection electrodes 51 and 52, respectively, and are joined to the extending portions 41b and 42b. As is clear from FIG. 6, the extraction electrode is not formed on the opposite surface (back surface) of the bonded portion with the metal bumps 51 a and 52 a in the quartz diaphragm, and the ultrasonic welding tool T is brought into contact with the portion. As shown in FIG. 6, the ultrasonic welding tool T used in this embodiment has a reverse concave shape in cross section, and has a configuration in which a partial region is in contact with the quartz crystal plate 4. By applying ultrasonic waves, the metal bumps 51a and 52a are melted, and the extending portions 41b and 42b of the extraction electrode and the connection electrodes 51 and 52 are electromechanically joined.
[0033]
A third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a plan view of the crystal diaphragm, and FIG. 8 is a side view as seen from the short side direction in FIG. 7 and also shows the configuration of a part of the base. In this embodiment, an example in which a protective film is formed is shown. The basic electrode configuration is almost the same as the configuration shown in the second embodiment, and a part of the description will be given using the same numbers.
[0034]
Excitation electrodes 41 and 42 (the back surface 42 is not shown) are formed on the front and back surfaces of the rectangular crystal diaphragm 4, and each excitation electrode is connected to the long side of the crystal diaphragm by the extraction electrodes 41 a and 42 a. It is pulled out to one end part in the direction and the central part in the short side direction. In addition, the lead electrodes 41a and 42a are each drawn out to the opposite surface of the crystal diaphragm, and on the side in contact with the connection electrode of the ceramic package (base) 5, extended portions 41b that extend to both ends in the short side direction. 42b are formed.
[0035]
A plurality of metal bumps 51a and 52a are formed on the connection electrodes 51 and 52, respectively, and are joined to the extending portions 41b and 42b. As is apparent from FIG. 8, thick film electrodes 43 and 44 that are thicker than the extraction electrodes are formed on the opposite surface (back surface) of the joint portion with the metal bumps 51a and 52a in the quartz crystal plate. In the present embodiment, the thick film electrodes 43 and 44 are formed by depositing a metal such as chromium on top of a normal extraction electrode material (for example, gold) by means such as vacuum deposition. The thick film electrodes 43 and 44 function as a protective film that does not damage a normal extraction electrode or a quartz diaphragm base. The ultrasonic welding tool T is brought into contact with the thick film electrodes 43 and 44, and ultrasonic waves are applied to perform bonding.
[0036]
A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a plan view of the crystal diaphragm, and FIG. 10 is a side view seen from the long side direction in FIG. 9 and also shows the configuration of a part of the base. In this embodiment, only part of the connections are made using metal bumps, and the others are connected by wire bonding.
[0037]
Excitation electrodes 61 and 62 are formed on the front and back surfaces of the rectangular crystal diaphragm 6, and one excitation electrode 61 is formed at one end in the long side direction of the crystal diaphragm by the extraction electrode 61 a and the other excitation electrode 62. Are extracted to the other end by the excitation electrode 62a. Each extraction electrode is extracted on the opposite surface.
[0038]
A plurality of metal bumps 71a are formed on the connection electrode 71, and are joined to the extraction electrode 61a drawn to the opposite surface (back surface) by ultrasonic welding. At the other end of the crystal diaphragm, the extraction electrode 62a and the connection electrode 72 are electrically joined by a wire W formed by wire bonding.
[0039]
In each of the above embodiments, the piezoelectric diaphragm using the thickness shear vibration is exemplified, but the present invention may be applied to a piezoelectric diaphragm of another vibration mode, for example, when a tuning fork type vibrator using flexural vibration is cantilevered. Good.
[0040]
【The invention's effect】
According to the piezoelectric vibrator of the first aspect, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bump, and the bonding reliability is increased. In addition, since the extraction electrode is not formed on the opposite surface (back surface) of the extraction electrode connected to the metal bump, a thermocompression bonding tool, an ultrasonic welding tool, or the like does not come into contact with the extraction electrode. Therefore, it is possible to prevent damage to the electrodes when welding the metal bumps, ensure a good conduction state, and obtain a highly reliable piezoelectric vibrator.
[0041]
According to the second aspect, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bump, and the reliability of the bonding is increased. In addition, since a protective film is formed directly on the extraction electrode and on the quartz plate, the extraction electrode and the quartz oscillation that affect the excitation of the quartz crystal even if an ultrasonic wave is applied to the part using an ultrasonic welding tool. It will not damage the board substrate. Therefore, it is possible to ensure a good conduction state and obtain a highly reliable piezoelectric vibrator.
[0042]
According to the third aspect of the present invention, in the piezoelectric diaphragm having the pair of main electrodes formed on the front and back surfaces, the extraction electrode and the connection electrode can be bonded to each other by melting the metal bumps, and the bonding reliability is increased. In addition, since the extraction electrode is not formed on the opposite surface (back surface) of the extraction electrode connected to the metal bump, the ultrasonic welding tool does not contact the extraction electrode. Therefore, the electrode can be prevented from being damaged when the metal bumps are welded, a good conduction state can be secured, and a highly reliable piezoelectric vibrator can be obtained.
[0043]
According to claim 4, in the piezoelectric diaphragm having a pair of main electrodes formed on the front and back surfaces,
Since a protective film is formed directly on the extraction electrode or on the quartz diaphragm substrate, even if an ultrasonic wave is applied to the part using an ultrasonic welding tool, the extraction electrode or quartz diaphragm substrate that affects the excitation of the quartz resonator Will not hurt. Therefore, it is possible to ensure a good conduction state and obtain a highly reliable piezoelectric vibrator.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view according to a first embodiment.
FIG. 2 is an internal cross-sectional view according to the first embodiment.
FIG. 3 is a plan view of the crystal diaphragm according to the first embodiment.
FIG. 4 is a side view in the short side direction of the crystal diaphragm according to the first embodiment.
FIG. 5 is a plan view of a crystal diaphragm according to a second embodiment.
FIG. 6 is a side view in the short side direction of a quartz crystal diaphragm according to a second embodiment.
FIG. 7 is a plan view of a crystal diaphragm according to a third embodiment.
FIG. 8 is a side view in the short side direction of a quartz crystal plate according to a third embodiment.
FIG. 9 is a plan view of a crystal diaphragm according to a fourth embodiment.
FIG. 10 is a side view in the long side direction of a crystal diaphragm according to a fourth embodiment.
FIG. 11 is a diagram showing a conventional example. FIG. 12 is a diagram showing a conventional example.
1, 5, 7, 9 Ceramic package 2 Lid 3, 4, 6, 8 Crystal diaphragm (piezoelectric diaphragm)
12a, 13a, 51a, 52a, 71a, 72a, 91a, 92a Metal bump 63, 64 Thick film electrode

Claims (5)

A base on which a plurality of connection electrodes are formed;
A pair of main electrodes are formed on the front and back, and a piezoelectric vibration plate made of a rectangular AT-cut quartz crystal vibration plate that extends each extraction electrode extending from the main electrode to a connection surface with each connection electrode;
The piezoelectric vibrating effectuate the joining of all the lead electrodes of the base of the connection electrode and the piezoelectric vibrating plate, the welding of the metal bumps made of the connection electrode and the wire bump formed on either one or both of the extraction electrode A child,
The lead electrode is drawn to the back surface at one end in the long side direction of the piezoelectric diaphragm and through the end in the short side direction, and further extended to the vicinity of the central part in the short side direction to form an extension part. Configuration and a configuration in which an extended portion is formed by being drawn out to the back surface through one end portion in the long side direction of the piezoelectric diaphragm and the other end portion in the short side direction, and further to the vicinity of the center portion in the short side direction. The lead electrode is not formed on the opposite surface of each extension part of the piezoelectric diaphragm, and the piezoelectric diaphragm connects each extension part and each connection electrode with metal bumps made of wire bumps. A piezoelectric vibrator characterized in that it is cantilevered. A base on which a plurality of connection electrodes are formed;
A plurality of main electrodes and each extraction electrode for pulling out the main electrode to the outside, a piezoelectric diaphragm extending each connection electrode to the connection surface with the connection electrode;
A piezoelectric vibrator that performs all bonding of the connection electrode of the base and the extraction electrode of the piezoelectric diaphragm by welding metal bumps formed on either or both of the connection electrode and the extraction electrode,
In the piezoelectric diaphragm, each extraction electrode is drawn out to one end portion in the long side direction of the piezoelectric diaphragm , is cantilevered by the connection electrode, and is connected to the metal bumps of the piezoelectric diaphragm. A piezoelectric vibrator characterized in that a protective film thicker than each of the lead electrodes is formed on the surface opposite to the surface on which the electrodes are formed. A base on which a plurality of connection electrodes are formed ;
A plurality of main electrodes and each extraction electrode for pulling out the main electrode to the outside, a piezoelectric diaphragm extending the extraction electrode to a connection surface with the connection electrode ;
A piezoelectric vibrator that performs all joining of the connection electrode of the base and the extraction electrode of the piezoelectric diaphragm by welding metal bumps formed on one or both of the connection electrode and the extraction electrode ,
The lead electrode has a configuration in which an extension portion is formed at one end portion in the long side direction of the piezoelectric diaphragm and drawn to the back surface through the central portion in the short side direction and further spreads at both ends in the short side direction, An extraction electrode is not formed on the opposite surface of each extension part of the piezoelectric diaphragm, and the piezoelectric diaphragm is cantilevered by connecting each extension part and each connection electrode with a metal bump. the piezoelectric vibrator, characterized in that are. The piezoelectric vibrator according to claim 2, wherein the protective film is made of metal. 5. The piezoelectric vibrator according to claim 1, wherein a plurality of metal bumps are formed on at least one of the connection electrodes.

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