JP5049702B2 - Stacked crystal unit - Google Patents

Description

  The present invention relates to a multilayer crystal resonator by direct bonding, and more particularly to a method for deriving an electrode to the outer surface of the crystal resonator.

(Background of the Invention)
A crystal resonator is known as a frequency control element, and is incorporated in an oscillation circuit of various electronic devices. In recent years, with the miniaturization and simplification, for example, a stacked crystal resonator using direct bonding using a siloxane bond has been proposed.

FIG. 9 is a view of a laminated crystal resonator for explaining one conventional example . FIG. 9 (a) is a cross-sectional view taken along the line AA of FIG. 9 (b), and FIG. FIG.

  The crystal unit is formed by directly joining the second and third crystal plates 1 (bc) to both main surfaces of the first crystal plate 1a with their crystal axes (XYZ) aligned. The first crystal plate 1a has, for example, a tuning fork crystal piece 2 that functions as a vibrator body, and the bottom surface of the tuning fork base portion 2a is connected (coupled) to the outer peripheral frame portion 3 with a protruding rod 3a interposed.

  The tuning fork crystal piece 2 has a length direction as a Y axis, a width direction as an X axis, and a thickness direction as a Z axis. The tuning fork arm 2b of the tuning fork crystal piece 2 is formed with a pair of excitation electrodes (not shown), and the first and second extraction electrodes 4 (ab) connected thereto are formed from the main surface of the tuning fork base 2a from the frame 3 The electrode pads 4 (xy) on both ends are extended through the surface.

  The second and third crystal plates 1 (bc) function as a cover for the vibrator body, and have a recess in a region facing the vibrator body (tuning fork-shaped crystal piece 2). And both main surfaces of the frame part 3 in the 1st crystal plate 1a and the opening end surface used as the outer peripheral part of the recessed part in the 2nd and 3rd crystal plate 1c are joined directly. In direct bonding, a mirror-polished bonding surface is made hydrophilic (OH group) and heated to form a Si—O—Si siloxane bond.

  For example, the outer periphery of the second crystal plate 1b has outer terminals 5 for surface mounting, and the first and second leads of the first crystal plate 1a are provided by the electrode through holes 6 provided on both ends. The electrode 4 (ab) is electrically connected to the extended electrode pad 4 (xy). The electrode through-hole 6 is formed by firing (sintering) by filling a previously formed through-hole with a conductive paste containing chromium (Cr), which is familiar with quartz. Thus, the electrode pad 4 (xy) and each external terminal 5 are electrically connected and the through hole is sealed (so-called via hole).

In such a structure, the number of parts is set to three points of the first to third crystal plates 1 (abc), thereby simplifying the structure and promoting the miniaturization of the crystal unit. For example, since the crystal axes (XYZ) of the first to third crystal plates 1 (abc) are in the same direction, the expansion coefficient is the same, and the time-dependent characteristics due to temperature changes are also good.
JP-A-8-204479 JP20000269775A Japanese Patent No. 3406845 JP 2001-119263 A

(Problems of conventional technology)
However, in the crystal resonator having the above-described configuration, the same electrode pad 4 (xy) of the first and second extraction electrodes 4 (ab) extending to the frame portion 3 of the first crystal plate 1a is formed on the second crystal plate 1b. It is led out by a via hole (electrode through hole 6) and connected to the external terminal 5 of the second crystal plate 1b. In this case, the frame 3 of the first crystal plate 1a is directly joined to the outer periphery of the second crystal plate 1b, but the first and second lead electrodes 4 (ab) and the electrode pads 4 (xy) are basically the same. It is not directly joined.

As a result, for example, as shown in FIG. 10 , the first and second electrode pads vary depending on the electrode film thickness of the electrode pad 4 (xy) including the first and second extraction electrodes 4 (ab) at the bonding interface. A gap corresponding to the electrode film thickness is generated around 4 (xy). Therefore, the airtightness of the crystal unit is basically maintained by the electrode through-hole 6 that is a via hole.

  However, since the via hole as the electrode through-hole 6 is sintered chromium and not an interatomic bond, it cannot be said that airtightness is necessarily ensured depending on manufacturing conditions and the like. And since the electrode through-hole 6 is provided only in the 2nd crystal plate 1b, a seal path | pass becomes short, so that the height reduction of a crystal oscillator progresses. Therefore, there is a problem that it is difficult to ensure airtightness.

(Object of invention)
SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated crystal resonator by direct bonding that ensures airtightness.

According to the present invention, a vibrator main body provided with an excitation electrode is connected to an outer peripheral frame portion, and a first crystal plate in which an extraction electrode extends to the frame portion, and a concave portion is provided in a region facing the vibrator main body. The opening end face is provided with second and third crystal plates that are directly joined to both main surfaces of the frame portion of the first crystal plate, and the extraction electrode is at least one of the second and third crystal plates. In the laminated crystal resonator, which is led out by an electrode through-hole formed in the outer surface of the frame portion by a via hole and connected to the external terminal of the outer surface, the electrode through-hole of the frame portion is an extension of the extraction electrode It was from the main surface of the frame portion Ri Do from the second electrode through hole formed in at least one of the second or third quartz plate and the first electrode through-hole which penetrates the frame portion, the first and second electrodes through The holes are at different positions on the first quartz plate and the second or third quartz plate. Made is by being a crank shape, further, wherein provided in the first quartz plate first electrode through-hole is a structure comprising the third and fourth electrodes through holes provided at different positions.

With such a configuration, since the first and second electrode through holes are formed in at least one of the first crystal plate and the second or third crystal plate, the seal path by the electrode through holes can be lengthened. Therefore, the airtightness of the crystal unit can be ensured , and the first and second electrode through holes are formed at different positions of the first crystal plate and the second or third crystal plate to form a crank shape. Alternatively, the airtightness can be ensured if the airtightness of at least one of the second electrode through holes is maintained. Further, the first electrode through-hole provided in the first crystal plate is composed of the third and fourth electrode through-holes provided at different positions, so that the third and fourth electrode through-holes and the above-mentioned second electrode through-hole are provided. Therefore, it is easier to ensure airtightness.

(First embodiment)
FIG. 1 and FIG. 2 (ab) are diagrams for explaining a first embodiment of the present invention. FIG. 1 is a cross-sectional view of a crystal resonator, FIG. 2 (a) is a plan view of a first crystal plate, FIG. 2B is a sectional view thereof. 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 crystal resonator is formed by directly bonding the first crystal plate 1a having the frame portion 3 as the resonator body and the second and third crystal plates 1 (bc) having the concave portions as the cover. The first crystal plate 1a as the vibrator body has a tuning fork crystal piece 2 as described above. The first and second lead electrodes 4 (ab) connected to the pair of excitation electrodes provided on the tuning fork arm 2b pass through one main surface of the tuning fork base portion 2a and the protruding rod 3a, and one end side of the frame portion 3 and the other. The electrode pad 4 (xy) extends to the end side.

The electrode pad 4 (xy) is connected to the electrode pad 7 (xy) on the other main surface by the first electrode through hole 6a by the via hole. The first electrode through-holes 6a are each close to the inner periphery of the frame portion. The electrode pad 7 (xy) is formed closer to the outer periphery than the first via hole 6a, and is connected to the external terminal 5 of the second crystal plate 1b by the second electrode through hole 6b by the via hole. The second electrode through hole 6b is formed in the outer peripheral portion (thick portion) on one end side and the other end side, and is separated from the first electrode through hole 6a and closer to the outer periphery.

  Both the first and second electrode through holes 6 (ab) are in the region of the bonding interface. In other words, the first and second electrode through holes 6 (ab) having a crank shape are provided in the region of the bonding interface. As a result, the first and second extraction electrodes 4 (ab) are formed by the crank-shaped first and second electrode through holes 6 (ab) provided in the first and second crystal plates 1 (ab). 2 Derived to the outer surface of the quartz plate 1b. The electrode through hole 6 (ab) is connected to each external terminal 5.

  For example, as shown in FIGS. 3A to 3F, first, an excitation electrode (not shown) on the first quartz plate 1a and first and second extraction electrodes 4 (ab ) Electrode pads (4xy) are formed on one end side and the other end side of the frame portion 3. These are integrally formed at the time of external shape processing from the crystal wafer by etching using the photolithographic technique of the first crystal plate 1a. Alternatively, it is formed by vapor deposition or sputtering after the outer shape processing. Each of these electrodes is gold (Au) plated with chromium (Cr) as a base electrode.

  Next, the third crystal plate 1c is directly joined to one main surface of the first crystal plate 1a (FIG. 3 (a)). Then, the first through-hole 6m is formed in the first quartz plate 1a by etching “FIG. 3 (b)”. In this case, the etching solution is hydrofluoric acid, and gold is not etched, and only the first through hole 6m is formed. Alternatively, the through hole 6m is formed using a known dry etching technique. Then, the first through hole 6m is filled with a conductive paste made of chromium and sintered to form a first electrode through hole 6a by a via hole (FIG. 3 (c)).

  Thereby, the 1st electrode through-hole 6a connects to each electrode pad 4 (xy) of the both ends in the one main surface of the 1st crystal plate 1a. Then, an electrode pad 7 (xy) near the outer periphery is formed by vapor deposition or the like connected to the first electrode through hole 6a exposed on the other main surface of the first crystal plate 1a (FIG. 3 (d)).

  Next, the second crystal plate 1b is directly joined to the other main surface of the first crystal plate 1a (FIG. 3 (e)). Here, the second through-hole 6n is formed in advance on both ends of the second crystal plate 1b by etching before direct bonding. Then, in the same manner as described above, the conductive paste is filled and sintered to form the second electrode through hole 6b (FIG. 3 (f)). Finally, the external terminal 5 made of gold plating is formed on the outer surface (outer bottom surface) of the second crystal plate 1b by vapor deposition or the like (FIG. 1).

  With such a configuration, the first and second electrode through-holes 6 (ab) of the first and second crystal plates 1 (ab) in the region of the bonding interface between the first and second crystal plates 1b. Then, the extraction electrode 4 (ab) of the first crystal plate 1 a is led out to the outer surface of the second crystal plate 1 b and connected to the external terminal 5. Therefore, the seal path of the electrode through-hole 6 is lengthened as compared with the case where it is formed only on the second crystal plate 1b of the conventional example, thereby preventing airtight leakage.

  Here, the first and second electrode through holes 6 (ab) are formed at different positions on the first and second crystal plates 1 (ab). Therefore, for example, even if there is an airtight leak in the first electrode through hole 6a or the second electrode through hole 6b, the airtightness can be reliably ensured if either one of the electrode through holes 6a or 6b is securely sealed. .

(Second Embodiment)
FIG. 4 is a cross-sectional view of the quartz resonator, particularly the both end sides, illustrating the second embodiment of the present invention. In addition, description of the same part as previous embodiment is abbreviate | omitted or simplified.

  In the second embodiment, the first electrode through-holes 6a on both ends from which the pair of extraction electrodes 4 (ab) on one main surface of the first crystal plate 1a (vibrator body) extend are connected to the third and The fourth electrode through hole 6 (cd) is formed. Then, the third and fourth electrode through holes 6 (cd) are electrically connected by the electrode pads 8 (xy) including conductive paths on the other main surface side of the first crystal plate 1a.

  Further, the fourth electrode through hole 6d is connected to the second electrode through hole 6b provided in the third crystal plate 1c through the electrode pad 9 (xy). The second electrode through hole 6b is connected to the external terminal 5 formed on the outer surface of the third crystal plate 1c.

  For example, first, after forming electrode pads to be connected to the third and fourth electrode through holes 6 (cd) on one main surface of the crystal plate, the third and fourth through holes are etched by the other main surface side. Form holes. Then, the conductive paste is filled and sintered to form third and fourth electrode through holes 6 (cd). Next, a metal film (chromium or the like) as an electrode pad 8 (xy) is provided by vapor deposition or the like on the third and fourth electrode through holes 6 (cd) exposed on the other main surface side of the first crystal plate 1a. Connect electrically.

  Next, the second and third crystal plates 1 (bc) are directly joined to both main surfaces of the first crystal plate 1a. Second through holes are formed in advance on both ends of the third crystal plate 1c. Thereby, the electrode pad 9x in the second through hole, which is provided on one main surface of the first crystal plate 1a and is electrically connected to the fourth electrode through hole 6d, is exposed. Then, the second through hole is filled with a conductive paste and sintered to form the second electrode through hole 6b. Finally, the external terminal 5 is formed on the second electrode through hole 6b exposed on the outer surface of the third crystal plate 1c by vapor deposition or the like.

  With such a configuration, the first electrode through hole 6a of the first crystal plate 1a is composed of the third and fourth electrode through holes 6 (cd), and each extraction electrode 4 (ab) has three electrode through holes. 6 (cdb) through the outer surface. Therefore, the seal path is made longer than that of the first embodiment, and if any of the second, third, and fourth electrode through holes 6 provided at different positions are sealed, the airtightness is ensured.

(Third embodiment)
FIG. 5 is a cross-sectional view of a crystal resonator illustrating a third embodiment of the present invention. In addition, description of the same part as previous embodiment is abbreviate | omitted or simplified.

  In the third embodiment, the first through hole 6a provided in the first crystal plate 1a and the second through hole 6b provided in the second crystal plate 1b, for example, are linear, and the extraction electrode is formed on the outer surface of the second crystal plate 1b. 4 (ab) is derived. And it connects with the external terminal 5 provided in the outer surface of the 2nd crystal plate 1a.

  These are, for example, a first crystal plate 1a and second and third crystals having an excitation electrode and an electrode pad 4 (xy) extending from the extraction electrode 4 (ab) on one end and the other end on one main surface. The plate 1 (bc) is directly joined. Then, through holes are formed by etching from both ends of the outer surface of the second crystal plate 1b to expose each electrode pad 4 (xy) of the first crystal plate 1a.

  Alternatively, first, the third crystal plate 1c is directly bonded to one main surface of the first crystal plate 1a where the electrode pads are formed. Then, a through hole is formed in the first crystal plate 1a from the other main surface, and the electrode pad 4 (xy) is exposed. Next, the second crystal plate 1b provided with the through-hole is directly joined to the other main surface of the first crystal plate 1a, and the first and second through-holes are linearly exposed to expose each electrode pad 4 (xy). To do.

  Finally, the first and second through holes that are linear are filled with a conductive paste and sintered to form linear first and second electrode through holes 6 (ab). Then, the external terminals 5 are formed on the second electrode through holes 6b exposed on the outer surface of the second crystal plate 1b by vapor deposition or the like.

  Even in this case, since the first electrode through hole 6a is formed in the first crystal plate 1a and the seal path of the electrode through hole is lengthened, airtightness can be ensured. Here, since the electrode through-holes 6 (ab) of the first and second quartz plates 1 (ab) are linear, the conductive paste is filled only once, which simplifies the manufacturing process.

(Fourth embodiment)
FIG. 6 is a cross-sectional view of a crystal resonator for explaining a fourth embodiment of the present invention. In addition, description of the same part as previous embodiment is abbreviate | omitted or simplified.

  In the fourth embodiment, the diameters of the first and second electrode through holes 6 (ab) formed in the first and second crystal plates 1 (ab) in the third embodiment are made different. For example, the second through hole 6b of the second crystal plate 1b is made larger than that of the first crystal plate 1a. If it does in this way, when the 1st and 2nd crystal plates 1 (ab) are joined directly, the position error of the 1st and 2nd through-holes can be absorbed, and it can be made straight.

(Other matters)
In the above embodiment, each electrode pad from which the pair of extraction electrodes 4 (ab) extends is formed on one main surface of the first crystal plate 1a. For example, each extraction electrode 4 (ab) is opposite to each other on both ends. Even if it is formed, it can be applied. In this case, for example, as shown in FIG. 7, the electrode through hole 6 is etched from the direction opposite to the surface on which each electrode pad is formed, so that the outside of the second and third crystal plates 1 (bc) is removed. The extraction electrode 4 (ab) is led out to the surface. And the external terminal 5 is provided in the perimeter of the outer peripheral surface of both sides | surfaces.

  In the first and second embodiments, the first and second electrode through-holes 6 (ab) are provided in the central regions on both ends of the first quartz plate 1a and arranged in the length direction. The two-electrode through-hole 6 (ab) may be arranged in the width direction to facilitate the formation of the via hole. In each embodiment, the first crystal plate 1a is the tuning fork crystal piece 2, but it may be a flat crystal piece made of AT cut, for example, which can be arbitrarily selected.

Further, for example, as shown in FIG. 8 (ab), the quartz crystal unit in which the first to third crystal plates 1 (abc) are laminated may be entirely resin-molded to prevent damage or the like. . For example, the external terminal 5 of the crystal resonator and the wire 7 by wire bonding are connected to a metal plate 8 as a mounting terminal and resin-molded “FIG. 8A”. In this case, an auxiliary plate 8a for raising the quartz resonator is provided on the bottom surface of the crystal unit. The metal plate 8 and the auxiliary plate 8a are connected in advance to a frame (not shown), and are cut out from the frame after resin molding.

Alternatively, the external terminal 5 of the crystal resonator is bonded to a metal plate 8 connected to a frame (not shown) by thermocompression bonding using a bump and resin-molded. And the metal plate 8 is cut out from a frame after resin molding. As a result, the entire crystal unit is resin-molded and the crystal itself is not exposed, so that the crystal is protected to prevent damage or the like.

It is sectional drawing of the crystal oscillator explaining 1st Embodiment of this invention. The top view and the figure (b) of the 1st quartz plate explaining a 1st embodiment of the present invention are sectional views. It is sectional drawing of the crystal oscillator explaining the manufacturing process of 1st Embodiment of this invention. It is sectional drawing of the crystal oscillator explaining 2nd Embodiment of this invention. It is sectional drawing of the crystal oscillator explaining 3rd Embodiment of this invention. It is sectional drawing of the crystal oscillator explaining 4th Embodiment of this invention. It is sectional drawing of the crystal oscillator explaining other embodiment of this invention. FIG. 6 is a cross-sectional view of a crystal resonator illustrating still another embodiment of the present invention. FIG. 4A is a cross-sectional view of the crystal resonator taken along the line AA of FIG. 2B, and FIG. 2B is a plan view of the first crystal plate. It is a partial expanded sectional view of the crystal oscillator explaining a prior art example.

Explanation of symbols

  1 (abc) 1st to 3rd crystal plate, 2 tuning fork crystal piece, 3 frame, 4 (ab) extraction electrode, 4 (xy), 7 (xy), 8 (xy), 9 (xy) electrode pad 5 External terminal 6 Electrode through hole 7 Conductor 8 Metal plate

Claims (1)

The vibrator main body provided with the excitation electrode is connected to the outer peripheral frame portion and has a first crystal plate in which a pair of extraction electrodes extends to the frame portion, and a concave portion in a region facing the vibrator main body. An opening end surface including second and third crystal plates directly bonded to both main surfaces of the frame portion of the first crystal plate, and the extraction electrode is an outer surface of at least one of the second and third crystal plates. In a laminated crystal resonator that is led out by an electrode through hole formed in the frame portion and connected to an external terminal on the outer surface,
The electrode through hole of the frame part is a first electrode through hole penetrating the frame part from the main surface of the frame part where the extraction electrode extends, and at least one of the second or third crystal plate. Ri Do from the through-hole,
The first and second electrode through holes are formed in different positions on the first crystal plate and the second or third crystal plate and are in a crank shape, and are further provided in the first crystal plate. The laminated crystal resonator, wherein the first electrode through hole is composed of third and fourth electrode through holes provided at different positions .