JP2000040935A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device which is proper for cost reduction and miniaturization. SOLUTION: In a piezoelectric device, a piezoelectric substrate 2 and a container 3 containing the piezoelectric substrate 2 are installed, an exciting electrode, a pad electrode 8 and a lead electrode for electrically connecting the exciting electrode to the pad electrode 8 are installed on the surface of the piezoelectric substrate 2, a land electrode 10 for connection with the pad electrode 3 is installed in the container 3, and the pad electrode 3 and the land electrode 10 are connected electrically and mechanically by conduction bumps 9. This device has the structure of a metallic multilayer film, where a metallic film in which the pad electrode is integrally formed with the exciting electrode Ni 6 on the surface of the metallic film and a metallic film 7 formed of silver on the surface the Ni are formed. Thus, the film thickness of the pad electrode 8 is substantially made to be thick. Then, yield is improved, and the cost of the piezoelectric device can be reduced, since the peeling of the pad electrode 8 and the damage to the piezoelectric substrate 2 by shocks at forming of the conduction bumps can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric device, and more particularly, to a piezoelectric device suitable for miniaturization.

[0002]

2. Description of the Related Art In recent years, mobile communication devices such as cellular phones have been reduced in price and miniaturized.
The parts to be used also need to be inexpensive and small. Such a requirement is not an exception for a SAW filter used as a signal selecting means and a piezoelectric device such as a quartz oscillator used as a reference signal source.
Until that time, the quartz substrate and the ceramic container were replaced by a connecting means using a conductive adhesive or a wire bonding, and as shown in FIG.

FIG. 3 is a cross-sectional view of a conventional crystal unit using a bump connection method. A quartz oscillator 100 shown in FIG. 1 includes a quartz substrate 101 and the quartz substrate 101.
Container 102 having a recess for accommodating
And a lid 103 for sealing the ceramic container 102. On the surface of the quartz substrate 101, an excitation electrode located at a substantially central portion thereof, a pad electrode 104 located at an end thereof, and a lead electrode connecting these electrodes are integrally formed by a metal thin film 105 made of Au or Al. Is formed. At the same time, the Au bump 106 is pressed against the surface of the pad electrode 104 with a specific pressure, and at the same time, the metal is diffused and connected by applying an impact by ultrasonic vibration. Then, the Au bump 106
And the land electrode 10 provided in the ceramic container 102
7 while pressing it with a specific pressure.
Pulse heat is supplied from at least one of the ceramic container 102 side and the ceramic container 102 side to perform thermocompression bonding. As a result, the excitation electrode and the functional terminal 108 of the crystal unit 100 provided below the ceramic container 102 are electrically connected, and the crystal substrate 101 is connected to the ceramic container 1.
02 and stored. Thus, the crystal unit 100
With this configuration, the mounting area of the crystal substrate 101 is reduced, and the size of the crystal unit 100 is reduced.

[0004]

However, as described above, the Au bump 106 and the pad electrode 1
Since the connection with the pad electrode 104 is performed by pressing both at a specific pressure and applying an impact by ultrasonic vibration, the pad electrode 104 is pressed by the pressure and the impact of ultrasonic vibration.
In some cases. That is, the thickness of the pad electrode 104 provided on the surface of the quartz substrate 101 is extremely small because it depends on the thickness of the metal thin film 105 forming the excitation electrode. Accordingly, the pad electrode 104 made of such a thin metal thin film 105 may not be able to withstand the pressure generated when the Au bump 106 is connected and the distortion caused by the shock of the ultrasonic vibration, and may be peeled off. In particular, when the pad electrode 104 is made of an Al film, a stronger pressure and an impact of ultrasonic vibration are required to break the thick oxide film layer existing on the surface of the Al film and connect to the Au bump 106. Therefore, the above problem is more likely to occur, and the crystal substrate 101 may be damaged by an excessive impact. Therefore, a piezoelectric device such as a quartz oscillator having a structure as shown in FIG. 1 has a problem that the yield is degraded due to the above-mentioned problem, and the cost cannot be reduced. Further, when the metal thin film 107 is made of an Al film, in addition to the above problems, the metal compound of Al and Au is mechanically fragile, so that the quartz substrate 101 and the ceramic container 102
In some cases, there is a problem that the bonding strength with the crystal resonator cannot be sufficiently obtained, whereby the crystal resonator cannot obtain sufficient impact resistance. The present invention has been made to solve the above-described problem, and has as its object to provide a small-sized piezoelectric device that is inexpensive and has excellent impact resistance.

[0005]

According to a first aspect of the present invention, there is provided an electro-optical device comprising: an exciting electrode on a surface of a piezoelectric substrate; and a pad electrode connected to the exciting electrode via a lead electrode. In a piezoelectric device electrically and mechanically connected by conductive bumps to a container provided with land electrodes for connection with the pad electrodes, the pad electrodes are made of a metal multilayer film. It is characterized by. The invention described in claim 2 is the same as the invention described in claim 1,
The pad electrode is a metal multilayer film including an Al film, a Ni film, and an Ag film. According to a third aspect of the present invention, in addition to the first aspect, the pad electrode has an A
It is characterized by being a metal multilayer film composed of a u film, a Ni film and an Ag film.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a sectional structural view of an embodiment of a quartz oscillator according to the present invention. A crystal resonator 1 shown in FIG. 1 includes a crystal substrate 2, a ceramic container 3 having a recess for accommodating the crystal substrate 2, and a lid 4 for sealing the ceramic container 3. . On the surface of the quartz substrate 2, an excitation electrode located at a substantially central portion thereof, a pad electrode portion located at an end thereof, and a lead electrode connecting these electrodes are integrally formed by a metal thin film 5 made of Au or Al. Is formed. The crystal oscillator 1 shown in FIG. 3 is different from the conventional crystal oscillator shown in FIG. 3 in that a Ni film 6 is formed on the surface of a metal thin film 5 at a pad electrode portion, and further a metal film is formed on the surface. A metal multilayer film on which an Ag film 7 is formed is formed, and the metal multilayer film portion including the three layers is used as a pad electrode 8. At this time, the Ni film 6 and the Ag film 7 can be easily formed by using an evaporation method. The Ni film 6
The reason why is interposed between the stacked layers is that the bonding strength between the thin films can be obtained as compared with the case where the Ag film 7 is formed directly on the surface of the Al or Au film. By forming the pad electrode 8 as a metal multilayer film in this manner, it is the same as the case where only the pad electrode 8 is formed substantially thick without affecting the thickness of the other excitation electrodes and the lead electrodes. State. Therefore, even when the Au bump 9 is pressed against the surface of the pad electrode 8 at a specific pressure and stress is generated at the time of applying ultrasonic vibration to diffuse the metal, a single-layer thin film is formed. Since the thickness of the pad electrode 8 is larger than that of a pad electrode made of a metal film, the pad electrode 8 is less likely to peel off. Further, since the surface of the Ag film 7 is harder to be oxidized and the diffusion speed is faster than that of the Al film, even if the pressure and the shock of the ultrasonic vibration are set to be weak, the Ag film 7 can be easily Au.
The bump 9 can be formed. After the formation of the Au bumps 9, the Au bumps 9 and the ceramic container 3 are formed.
Thermocompression bonding is performed by supplying pulsed heat from at least one of the quartz substrate 2 side and the ceramic container 3 side while pressing the land electrode 10 provided therein at a specific pressure. Thus, the excitation electrode provided on the quartz substrate 1 and the quartz oscillator 1 provided below the ceramic container 3
And the quartz crystal substrate 2 is fixed to the ceramic container 3 and housed therein.
Then, the quartz resonator 1 is completed by sealing the ceramic container 3 using the lid 4.

Further, as an example of the present invention, a quartz oscillator using a flat quartz substrate as shown in FIG. 3 has been described as an embodiment. However, the present invention is not limited to this, and as shown in FIG. The quartz substrate 2 is formed with a recess in an appropriate position on one main surface of the quartz substrate 2 by using a technique such as etching, and the thin portion remaining in the recess is used as the vibrating section 12 and the vibrating section is formed. It may be a quartz crystal unit using an integrally formed annular surrounding portion for supporting the periphery of the crystal unit. Although a quartz oscillator has been described as an example of the present invention in the embodiments, the present invention is not limited to this, and other piezoelectric devices such as a SAW device may be used. Further, in one embodiment according to the present invention, quartz crystal was described as a piezoelectric material constituting a piezoelectric device, but the present invention is not limited thereto, and other materials such as lithium niobate and lithium tantalate may be used. A piezoelectric device using a piezoelectric material may be used.

[0008]

As described above, according to the first aspect of the present invention, a thick film is formed by providing a Ni film and a metal multilayer film made of an Ag film on the surface of the pad electrode provided on the piezoelectric substrate. A pad electrode is obtained, and the pressure at the time of forming the conductive bumps and the peeling of the pad electrode due to the impact of ultrasonic vibration are less likely to occur, whereby the piezoelectric device can easily form the conductive bumps. In addition, there is an effect that the price can be reduced by improving the yield. Further, even in a piezoelectric device having an Al electrode, since the conductive bumps are formed so as to be firmly connected to the Ag film, the piezoelectric substrate is mechanically and firmly fixed in the container. Has the effect of improving the impact resistance, and can set the pressure applied during the formation of the conductive bumps and the impact of the ultrasonic vibration to be small, thereby removing the pad electrode and breaking the piezoelectric substrate. It is possible to obtain an improvement in yield due to the suppression of occurrence, and to achieve an effect of achieving a reduction in price.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of a quartz oscillator according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the quartz resonator according to the present invention.

FIG. 3 is a cross-sectional configuration diagram of a conventional crystal unit.

[Explanation of symbols]

1,100 crystal oscillator, 2,101 crystal substrate, 3,10
2 ceramic container, 4103 lid, 5, 105 metal thin film,
6, Ni film, 7Ag film, 8, 104 pad electrode, 9, 1
06 Au bump, 10, 107 land electrode, 11, 10
8 function terminals, 12 vibrating parts,

Claims (3)

[Claims] A container provided with an excitation electrode on a surface of a piezoelectric substrate and a pad electrode connected to the excitation electrode via a lead electrode, and a land electrode for connecting to the pad electrode is provided in a container. A piezoelectric device electrically and mechanically connected by bumps, wherein the pad electrode is made of a metal multilayer film. 2. The semiconductor device according to claim 1, wherein said pad electrode is a metal multilayer film comprising an Al film, a Ni film and an Ag film.
The piezoelectric device as described. 3. The semiconductor device according to claim 1, wherein said pad electrode is a metal multilayer film including an Au film, a Ni film, and an Ag film.
The piezoelectric device as described.