JP3977682B2 - Quartz crystal resonator and its holding structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crystal resonator in an industrial technical field, and more particularly to a holding structure for a crystal resonator (a surface mount resonator) using a eutectic alloy for surface mounting.
[0002]
[Prior art]
(Background of the Invention) Surface mounted resonators are small and light, and are used as a reference source for frequency and time of mobile devices such as mobile phones. In recent years, higher reliability and higher frequency have been demanded, and due to this, a review of the holding structure and the like has been demanded.
[0003]
(Example of Prior Art) FIGS. 3 and 4 are diagrams for explaining one conventional example, FIG. 3 is an exploded view of a surface-mounted vibrator, and FIG. 4 is a sectional view of a crystal piece.
The surface-mounted vibrator is formed by housing a crystal piece 2 in a container body 1 and covering a cover 3, and sealing the crystal piece 2. The container main body 1 is made of, for example, a concave laminated ceramic, and has a pair of metallized layers (crystal terminals) 4 as connection terminals for the crystal piece 2 on the inner bottom surface. On the outer surface (bottom surface and side surface), there are mounting electrodes (not shown) for surface mounting electrically connected to the crystal terminals 4.
[0004]
The quartz crystal piece 2 has excitation electrodes 5 on both main surfaces, and leads electrodes 6 for external connection are formed on both sides of one end through extraction electrodes. The lead-out electrodes 6 are formed by folding back to the opposite surface through the side surfaces of the corners. Each of these electrodes is formed by vapor deposition or the like from the main surface of the crystal piece 2 with the first layer being the base electrode 8 and the second layer being the conduction electrode 9. Here, the first layer (base electrode 8) is Cr, and the second layer (conduction electrode 9) is Au. Since the crystal piece 2 and Au as the conductive electrode 9 have low adhesion strength, Cr is interposed as a base electrode 8 that is familiar to them.
[0005]
Then, the lead-out electrodes 6 on both sides of the one end are fixed by the conductive adhesive 7 so as to face the crystal terminals 4 on the inner bottom surface corresponding to the lead electrodes 6. For example, a cover 3 made of metal is joined to a metal ring or metallization layer (not shown) provided on the opening end surface of the container body 1 by seam or beam welding.
[0006]
[Problems to be solved by the invention]
(Problems of the prior art) However, the surface mount resonator having the above-described configuration has the following problems due to the holding structure in which the crystal piece 2 is fixed by the conductive adhesive 7. That is, the conductive adhesive 7 is based on, for example, a silicon-based resin made of a polymer as an organic substance.
[0007]
For this reason, for example, when the conductive adhesive 7 is cured, an emitted gas is generated from the organic substance, which adheres to the crystal piece 2 and deteriorates the aging characteristics. In particular, as the frequency increases (for example, 100 MHz or more) and the crystal piece 2 becomes thinner, the influence becomes larger and the problem becomes more prominent. The same applies when the specifications are strict and high reliability is required.
[0008]
(Object of the Invention) An object of the present invention is to provide a quartz crystal unit and its holding structure that improve the secular change characteristic and promote high frequency and high reliability.
[0009]
[Means for Solving the Problems]
(Points of interest and application) The present invention focuses on an existing holding structure in which a metal supporter and a crystal piece are joined together by a eutectic alloy, and is applied to a surface mount vibrator as a basic solution. In the present invention, this makes it possible to obtain a surface-mount resonator that does not generate gas from organic substances and that maintains good aging characteristics.
[0010]
In addition, according to the present invention, basically, the electrode structure of the electrode lead-out portion in the crystal resonator (crystal piece) is the base electrode from the main surface of the crystal piece, the conductive electrode from the second layer, and the shielding electrode from the third layer. , and the bonding electrode comprising the fourth layer from the eutectic alloy, said base electrode is Cr, the conductive electrode is Au, the shielding electrode Cr and Ni, the bonding electrode is a AuGe, the shielding electrode of the bonding electrode The conductive electrode is prevented from being eaten at the time of melting.
[0011]
【Example】
FIG. 1 is a view of a surface-mounted vibrator for explaining an embodiment of the present invention, FIG. 1 is an assembled sectional view, and FIG. 2 is a sectional view of a crystal piece. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.
As described above, the surface-mounted vibrator is formed by housing the crystal piece 2 in the container body 1 and covering the cover 3 and sealingly sealing it. Here, the container body 1 is provided with a step portion on the inner wall of the recess, and the crystal terminals 4 are provided on both sides of the step portion on one end side. And it has the metallization layer 10 which consists of Au in an opening end surface (frame wall upper surface).
[0012]
Similarly to the above, the crystal piece 2 has the excitation electrodes 5 on both main surfaces and the lead-out electrodes 6 connected to the excitation electrodes 5 on both sides of one end. Also here, the first base electrode 8 is Cr, and the second conductive electrode 9 is Au. Then, a shielding electrode 11 is formed as a third layer on the conductive electrode 9 of the second layer, and a bonding electrode 12 is formed thereon as a fourth layer by vapor deposition or the like. The shield electrode 11 is formed so as to protrude from the bonding electrode 12.
[0013]
In this example, the third-layer shielding electrode 11 is Cr, and the fourth-layer bonding electrode 12 is a eutectic alloy made of AuGe. In the figure, the thickness of each layer is the same, but the Cr of the base electrode 8 is about 300 Å, the Au of the conductive electrode 9 is 600 Å, the Cr of the shielding electrode 11 is 1000 Å or more, and the bonding electrode 12 is 1 to 2 μm. To the extent. The cover 3 is made of metal, and a bonding material 13 made of an eutectic alloy of AuSn is formed by pressure welding on the outer periphery that circulates.
[0014]
In such a case, the lead-out electrodes 6 formed on both sides of one end portion of the crystal piece 2 and the crystal terminals 4 formed on the step portion of the container body 1 face each other, and both end portions of the crystal piece 2 are stepped on both sides. Place on the club. Then, using a jig (not shown), both sides of one end of the crystal piece 2 are heated and pressed. In short, the bonding electrode 12 (eutectic alloy AuGe) of the fourth layer 12 is melted by thermocompression bonding, and both ends of one end are electrically and mechanically connected to the crystal terminal 4.
[0015]
Next, after holding both ends of one end of the crystal piece 2, for example, the excitation electrode 5 is irradiated with an ion beam to adjust the vibration frequency. After the adjustment, the outer periphery of the cover 3 provided with the bonding material 13 (eutectic alloy AuSn) is brought into contact with the opening end surface of the container body 1 and bonded by the same thermocompression bonding as described above. Thereby, the crystal piece 2 is hermetically sealed.
[0016]
With such a configuration, the crystal piece 2 using a eutectic alloy is joined without using the conventional conductive adhesive, and there is almost no organic substance in the container body 1. Therefore, since the emitted gas does not adhere to the crystal piece 2, the secular change characteristic is maintained well, and the high reliability and high frequency of the surface mount vibrator are promoted.
[0017]
In this embodiment, the shielding electrode 11 (Cr) is interposed between the second-layer conducting electrode 9 (Au) and the fourth-layer bonding electrode 12 (eutectic alloy AuGe). Therefore, at the time of thermocompression bonding, the molten bonding electrode 12 is blocked by the shielding electrode 11, and the outflow is suppressed to prevent the conduction electrode 9 from being eaten.
[0018]
In the case where the shielding electrode 11 is not provided, the bonding electrode 12 (AuGe) and the conductive electrode 9 (Au) are fused, and the conductive electrode 9 is attracted to the bonding electrode 12 to cause so-called biting and peeling. This causes poor conduction. Therefore, in this embodiment, the shielding electrode 11 prevents the conduction electrode 9 from being eaten, and the conduction can be reliably maintained.
[0019]
Furthermore, in this embodiment, the container body 1 and the cover 3 are joined by thermocompression using a joining material 13 made of an eutectic alloy of AuSn. In this case, the melting temperature of the bonding material 13 is lower than the eutectic alloy AuGe of the bonding electrode 12 to which the crystal piece 2 is fixed. Incidentally, the melting temperature of AuGe is about 356 ° C., and that of the bonding material 13 is 280 ° C. Therefore, the bonding electrode 12 (AuGe) is not melted when the cover 3 is bonded, and the holding state is maintained.
[0020]
Therefore, both the holding of the crystal piece 2 and the joining of the cover 3 are work steps by thermocompression, thereby facilitating management of equipment. In addition, for example, the equipment investment can be suppressed as compared with the joining by seam welding or beam welding, and the cost can be reduced and the economy can be improved.
[0021]
[Other matters]
In the above embodiment, the ground electrode 8 of the first layer is Cr, but the point is that the crystal piece 2 and the conductive electrode 9 of the second layer are familiar. Further, although the conductive electrode 9 is Au, basically, for example, any material having good conductivity of Ag or Al may be used.
[0022]
Further, although the bonding electrode 12 of the fourth layer is made of AuGe, for example, AuSi (melting temperature 363 ° C.) can also be applied, which is basically an inorganic substance and the melting temperature is the melting temperature of the cream solder when mounted on the circuit board. Any eutectic alloy having a crystal transition temperature of 573 ° C. or lower at 220 ° C. or higher may be used. Further, although the third-layer shielding metal 11 is Cr, it may be, for example, CrNi, which is selected from the balance between the second-layer conductive electrode 9 and the fourth-layer bonding electrode 12.
[0023]
The cover 3 is joined by thermocompression bonding using an eutectic alloy of AuSn. However, the cover 3 is not limited to this, and may be seam, beam welding, glass or resin sealing. The quartz crystal piece 2 having the electrode structure of the present invention can be applied not only to the surface mount vibrator but also to the case where it is held by a metal holder.
[0024]
Further, although described as a crystal resonator, the present invention can also be applied to a case where an oscillator or the like is accommodated together with other circuit elements. And although the container main body 1 provided the step part in the recessed part, even if there is no step part, you may thermocompression-bond directly to an inner bottom face. Moreover, the container main body 1 may be joined to the concave cover 3 as a flat plate shape.
[0025]
【The invention's effect】
The present invention is as described above, and basically obtained a surface-mount resonator in which crystal pieces are bonded by thermocompression bonding using a eutectic alloy. It is possible to provide a surface mount resonator with high quality and high reliability. Further, since the shielding electrode is interposed between the conduction electrode and the bonding electrode, the conduction electrode is not eroded when the bonding electrode is melted, and bonding by, for example, thermocompression bonding with good conduction is enabled.
[Brief description of the drawings]
FIG. 1 is an assembled cross-sectional view of a surface-mounted vibrator for explaining an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a crystal piece for explaining an embodiment of the present invention.
FIG. 3 is an assembly diagram of a surface-mount vibrator for explaining a conventional example.
FIG. 4 is a cross-sectional view of a crystal piece for explaining a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Container body, 2 Crystal piece, 3 Cover, 4 Crystal terminal, 5 Excitation electrode, 6 Derivation electrode, 7 Conductive adhesive, 8 Ground electrode, 9 Conduction electrode, 10 Metallization layer, 11 Shielding electrode, 12 Joining electrode, 13 Bonding material.

Claims (2)

An electrode structure of the electrode lead-out part in the crystal resonator in which the lead-out electrode is extended from the excitation electrodes formed on both main surfaces of the crystal piece to provide an electrode lead-out part as a connection terminal and holds the electrode lead-out part Is the ground electrode from the main surface of the crystal piece, the second layer is a conductive electrode, the third layer is a shielding electrode, the fourth layer is a bonding electrode made of a eutectic alloy , the ground electrode is Cr, the conductive electrode Is a quartz crystal resonator , wherein the shielding electrode is Cr or Ni, the bonding electrode is AuGe, and the shielding electrode prevents the conduction electrode from being eaten when the bonding electrode is melted. A quartz crystal piece having an electrode lead-out portion formed by extending an extraction electrode from excitation electrodes on both main surfaces, and a container body having a metallization layer corresponding to the electrode lead-out portion, the electrode lead-out portion and the metallization layer; In the crystal resonator holding structure formed by bonding, the electrode lead-out part and the metallized layer are joined by thermocompression bonding using a eutectic alloy, and the electrode structure of the electrode lead-out part is from the main surface of the crystal piece. The first layer is a ground electrode, the second layer is a conductive electrode, the third layer is a shield electrode, and the fourth layer is a bonding electrode made of a eutectic alloy. The ground electrode is Cr, the conductive electrode is Au, and the shield electrode is Cr. Alternatively, Ni, the bonding electrode is AuGe, and the shielding electrode suppresses the outflow to the conduction electrode when the bonding electrode is melted .

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