JP2020088771A - Piezoelectric vibration piece and piezoelectric device using the piezoelectric vibration piece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device having a good reflow resistance property even if it is a microminiature piezoelectric vibrating piece.
In the crystal oscillator 1, a pair of connection electrodes 341 and 342 are formed at both ends of one short side on the front and back main surfaces of the crystal vibrating piece 3. In each region of the pair of connection electrodes 341 and 342, exposed portions 9 and 9 in which the base material of the crystal vibrating piece is exposed are provided. In one connection electrode, the ratio of the opening area S1 of the exposed portion 9 to the area S2 of the connection electrode in plan view is 1.9% or more and 7.7% or less. In the crystal vibrating piece 3, in a state in which the conductive adhesive S, S reaches the connection electrodes 341, 342, the first side surface electrodes 343, 344, and the break marks 38, 38 so as to cover the exposed portion 9, It is joined to the electrode pads 6 and 6.
[Selection diagram]

Description

The present invention relates to a piezoelectric device used as a timing device of various electronic devices and a piezoelectric vibrating piece used for the piezoelectric device.

In recent years, piezoelectric devices such as crystal oscillators and crystal oscillators have become ultra-miniaturized. For example, the external dimensions of a surface-mount type crystal oscillator having a substantially rectangular shape in plan view are such that the long side is 1.6 mm or less and the short side is 1.2 mm or less.

To give a representative example of the crystal unit, the crystal unit is a package (container) made of an insulating material having a recess opening upward, and one end of which is cantilevered through a conductive adhesive inside the recess. It is composed of a crystal vibrating piece to be joined and a lid which is joined to the open end of the package so as to cover the recess of the package containing the crystal vibrating piece. As the crystal vibrating piece becomes ultra-small, its outer shape is being formed by using photolithography technology or wet etching (etching by chemical dissolution by immersing a crystal wafer in an etching solution). .. A method of manufacturing such a crystal vibrating piece is disclosed in Patent Documents 1 and 2, for example.

The reflow resistance property of the piezoelectric device is measured in its environmental performance test. This anti-reflow property is judged by whether or not the amount of change in the oscillation frequency of the piezoelectric device after passing the piezoelectric device a predetermined number of times through a reflow furnace set to a predetermined temperature condition satisfies a predetermined criterion. It is a test to judge.

For example, in the case of a conventional quartz vibrating piece having an external dimension, the reflow resistance has not been a problematic level until now. However, in the case of an ultra-small crystal vibrating piece, the amount of change in the oscillation frequency of the crystal resonator did not satisfy the determination standard, and the crystal resonator sometimes failed. This change in the oscillation frequency is greatly affected by the stress applied to the portion of the crystal vibrating piece supported by the conductive adhesive. When the amount of change in the stress applied to the crystal vibrating piece increases, the amount of change in oscillation frequency also increases.

JP-A-53-139994 JP-A-5-315881

The present invention has been made in view of the above points, and an object of the present invention is to provide a piezoelectric device having excellent reflow resistance even with a microminiature piezoelectric vibrating piece.

In order to achieve the above object, the invention of claim 1 is a piezoelectric vibrating piece having a substantially rectangular shape in a plan view, and both ends of at least one short side on the front and back main surfaces of the piezoelectric vibrating piece are joined to the outside. A pair of connection electrodes are provided apart from each other, and an exposed portion in which the base material of the piezoelectric vibrating piece is exposed is provided in each region of the pair of connection electrodes. The opening area of the part is 1.9% or more and 7.7% or less of the area of the connection electrode in plan view.

According to the above invention, the amount of change in the oscillation frequency of the piezoelectric device can be suppressed. This is because there is provided an exposed portion in the area of the connection electrode, the adhesion of which to the conductive adhesive is superior to that of the metal forming the connection electrode. In other words, the exposed portion where the base of the piezoelectric vibrating piece is exposed improves the adhesion between the piezoelectric vibrating piece and the conductive adhesive and firmly bonds them, so that the piezoelectric vibrating piece supported by the conductive adhesive works. This is because it is possible to make it difficult to change the stress.

Further, according to the above invention, in one of the connection electrodes, the opening area of the exposed portion is 1.9% or more and 7.7% or less with respect to the area of the connection electrode in plan view. It is possible to suppress the variation in frequency deviation in the reflow resistance characteristics of the piezoelectric device while improving the adhesion between the vibrating piece and the conductive adhesive.

In order to achieve the above-mentioned object, the invention of claim 2 is characterized in that the piezoelectric vibrating piece according to claim 1 is bonded to an electrode pad provided inside the container via a conductive adhesive, and A piezoelectric device hermetically sealed by joining a lid, wherein one side of the piezoelectric vibrating piece on which one pair of connection electrodes is formed is continuous with each of the pair of connection electrodes. The pair of first side surface electrodes are formed and the breakage traces of the piezoelectric vibrating piece are exposed, and the conductive adhesive is formed so that the conductive adhesive covers at least the pair of connection electrodes and the pair of first side electrodes. It is characterized in that the piezoelectric vibrating piece is bonded to the electrode pad in a state of reaching one side surface electrode and the fracture mark.

According to the above invention, the piezoelectric vibrating piece is not only connected to the connection electrode so that the conductive adhesive covers the exposed portion, but also on the electrode pad in a state of reaching the first side surface electrode and the break mark. Since they are joined together, the adhesion between the piezoelectric vibrating piece and the conductive adhesive can be further improved. This is not only the exposed portion having excellent adhesion with the conductive adhesive, because the conductive adhesive also extends to the fracture marks whose surface is rougher than the exposed portion, so-called "anchor effect", This is because the adhesion between the piezoelectric vibrating piece and the conductive adhesive is further improved.

A pair of second side surface electrodes continuous with each of the pair of connection electrodes may be formed on a pair of long side surfaces of the piezoelectric vibrating reed having a rectangular shape in plan view. Then, the piezoelectric vibrating piece with the conductive adhesive covering all of the pair of connection electrodes, the pair of first side surface electrodes, the breakage traces, and the pair of second side surface electrodes so as to cover the exposed portion. May be joined to the electrode pad. In the case of this configuration, the conductive adhesive extends to the second side surface electrode in addition to the connection electrode including the exposed portion, the first side surface electrode, and the rupture mark, so that the short side of the piezoelectric vibrating piece is adjacent to the short side. The conductive adhesive is arranged so as to extend over the long side. As a result, the adhesiveness between the piezoelectric vibrating piece and the conductive adhesive is further increased, and the bonding force can be improved.

As described above, according to the present invention, it is possible to provide a piezoelectric device having excellent reflow resistance even with an ultra-small piezoelectric vibrating piece.

Schematic cross-sectional view of a crystal unit according to an embodiment of the present invention A schematic top view of the crystal unit according to an embodiment of the present invention excluding a lid. A schematic top view of a crystal resonator element according to an embodiment of the present invention before being broken off. The upper surface schematic diagram after breaking off of the crystal vibrating piece which concerns on embodiment of this invention. The expansion perspective view of the B section of FIG. Reflow resistance of conventional crystal oscillator Reflow resistance characteristics of the crystal oscillator according to the embodiment of the present invention Reflow resistance characteristics of the crystal oscillator according to the embodiment of the present invention Reflow resistance characteristics of the crystal oscillator according to the embodiment of the present invention Reflow resistance characteristics of the crystal oscillator according to the embodiment of the present invention Enlarged perspective view of a crystal vibrating piece according to another embodiment of the present invention.

Hereinafter, as a piezoelectric device according to an embodiment of the present invention, a temperature-compensated crystal oscillator will be described as an example with reference to the drawings. FIG. 1 is a schematic sectional view taken along line AA of FIG. 2 of a crystal oscillator according to an embodiment of the present invention. First, an outline of each member constituting the crystal oscillator will be described, and then the crystal resonator element will be described in detail.

In FIG. 1, a crystal oscillator 1 includes a container 2, a crystal vibrating piece 3, an electronic component element 4, and a lid 5 as main constituent members. In this embodiment, as the electronic component element 4, an integrated circuit element (IC) in which an oscillation circuit, a temperature compensation circuit, a temperature sensor and the like are integrated into one chip is used. The external dimensions of the crystal oscillator 1 in the present embodiment in plan view are 1.6 mm in the vertical direction and 1.2 mm in the horizontal direction. The external dimensions of the crystal oscillator in plan view are examples, and dimensions other than the external dimensions may be used.

In FIG. 1, the container 2 having a substantially rectangular shape in a plan view includes a flat plate-shaped substrate portion 20, an upper frame portion 21 extending upward from an outer peripheral edge of a main surface 201 which is an upper surface of the substrate portion 20, and a lower surface of the substrate portion 20. And the lower frame portion 22 extending downward from the outer peripheral edge of the other main surface 202. Each of the substrate portion 20, the upper frame portion 21, and the lower frame portion 22 is a ceramic green sheet (alumina). The container 2 is integrally molded by firing these three sheets in a laminated state. Internal wiring of a predetermined shape is formed between the stacked layers of these three sheets.

A space formed by the upper frame portion 21 and the one main surface 201 of the substrate portion 20 is an upper recess E1, which is substantially rectangular in a plan view. Then, as shown in FIG. 2, a pair of electrode pads (pads for mounting a crystal vibrating piece) 6 are provided on one short side of the inner bottom surface (one main surface 201) of the upper recess E1 so as to be spaced apart from each other. They are formed in parallel in a state. The pair of electrode pads 6 and 6 are pads to which a connecting electrode (described later) on the one end side 3A of the crystal vibrating piece 3 is cantilevered via conductive adhesives S and S. In the present embodiment, the pair of electrode pads 6 and 6 has a laminated structure in which an electrolytic nickel plating layer is formed on a tungsten metallized layer, and an electrolytic gold plating layer is further formed thereon. A metal film (not shown) is formed in a frame shape on the upper surface 210 of the upper frame portion 21.

A space formed by the lower frame portion 22 and the other main surface 202 of the substrate portion 20 is a lower recess E2, which is substantially rectangular in a plan view. On the inner bottom surface (the other main surface 202) of the lower recess E2, six electronic component element mounting pads (not shown) which are conductively bonded to the electronic component element 4 (hereinafter, abbreviated as IC mounting pads) are formed. On each of these six IC mounting pads, six functional terminals provided on the active surface side of the IC are conductively bonded one-on-one via six metal bumps (not shown). An insulating resin (underfill) 8 is disposed in a gap between the inner bottom surface of the lower recess E2 having the six IC mounting pads formed therein and the active surface side of the electronic component element 4 (see FIG. 1). ..

Two of the six functional terminals of the electronic component element 4 are provided with a pair of crystal terminals via internal wiring (not shown) and castellation (not shown. Conductor formed on the outer surface of the substrate portion 20). It is electrically connected to the electrode pads 6 and 6, respectively. The temperature information of the crystal vibrating piece 3 is detected by a temperature sensor built in the electronic component element 4, and the oscillation frequency of the crystal vibrating piece is temperature-compensated.

Four external connection terminals 7, 7, 7, 7 are formed at the four corners of the lower surface (top surface) of the lower frame portion 22, which is the outer bottom surface of the container 2, and are connected to the land of the external substrate and the solder or the like. To be joined. A configuration in which these external connection terminals 7, 7, 7, 7 and the metal film on the upper surface 210 of the above-described upper frame portion 21 are also laminated in this order on the metallization layer of tungsten, a nickel plating layer and a gold plating layer. Has become. In addition to tungsten, molybdenum (Mo) or titanium (Ti) may be used for the metallized layer.

The crystal vibrating piece 3 is a piezoelectric element in which various electrodes are formed on an AT-cut crystal vibrating plate. In the present embodiment, the crystal vibrating piece 3 is a rectangular flat plate in a plan view. The central portion of each of the front and back main surfaces of the crystal diaphragm may have a so-called “mesa shape” protruding in the thickness direction. In addition to the above mesa shape, for example, a so-called "inverse mesa shape" including an outer peripheral portion formed to be thicker than the vibrating portion on the center side of the crystal diaphragm may be used. Further, the structure may be such that only one main surface side of the crystal diaphragm is thinned. The outer shape of such a crystal diaphragm can be formed by using an AT-cut crystal wafer by photolithography and wet etching. The outer shape of the quartz crystal diaphragm according to the quartz crystal resonator element 3 of the present embodiment is formed by photolithography and wet etching.

Excitation electrodes for driving the crystal diaphragm are provided on the center sides of one main surface (front surface in FIG. 1) of the crystal vibrating piece 3 and the other main surface (back surface in FIG. 1) facing the one main surface. A pair of 32a and 32b are formed so as to face each other. In the drawings, various electrodes on the one main surface side of the crystal diaphragm are suffixed with a, and various electrodes on the other main surface side of the crystal diaphragm are suffixed with b to the crystal. The electrodes on the front and back of the diaphragm are distinguished.

As shown in FIG. 2, extraction electrodes 33a and 33b that are extracted in the same direction are formed from each of the pair of excitation electrodes 32a and 32b. A pair of connection electrodes 341, 342 connected to the respective ends of the extraction electrodes 33a, 33b and conductively joined to the pair of electrode pads 6, 6 of the container 2 described above are provided on one end side 3A of the crystal vibrating piece 3. Has been formed. The pair of excitation electrodes 32a and 32b, the extraction electrodes 33a and 33b, and the pair of connection electrodes 341 and 342 are collectively formed by sputtering. Specifically, these electrodes have a film structure in which chromium (Cr) or titanium (Ti) is used as a base layer and gold (Au) is formed thereon.

One exposed portion 9 is provided in each formation region of the pair of connection electrodes 341 and 342. The pair of exposed portions 9 and 9 are portions where the base material of the crystal vibrating piece is exposed, and are circular in plan view. Details of the exposed portion 9 will be described later.

According to the above configuration, the amount of change in the oscillation frequency of the crystal oscillator 1 can be suppressed. This is because the exposed portions 9 and 9 are provided in the regions of the connection electrodes 341 and 342, the adhesion of which with the conductive adhesive S is superior to that of the metal forming the connection electrodes 341 and 342. That is, the exposed portion 9 where the base material of the crystal vibrating piece 3 is exposed improves the adhesion between the crystal vibrating piece 3 and the conductive adhesive S and firmly bonds them, so that the conductive material S is supported by the conductive adhesive S. This is because it is possible to make it difficult to change the stress acting on the crystal vibrating piece 3.

One of the connection electrodes 341 has a part of the one main surface from the connection electrode 341b (see FIG. 1) on the other main surface of the crystal vibrating piece 3 via the short side surface of the one end side 3A of the crystal vibrating piece 3. It is connected to the connection electrode 341a. Similarly, a part of the other connecting electrode 342 is connected to the other main surface from the connecting electrode 342a on one main surface of the crystal vibrating piece 3 via the short side surface of the one end side 3A of the crystal vibrating piece 3. It is connected to the electrode 342b (not shown in FIG. 2). The pair of connection electrodes 341 and 342 have different polarities.

The lid 5 shown in FIG. 1 has a structure in which a nickel plating layer and a gold plating layer are laminated in this order on the outer peripheral surface of Kovar as a base material. A gold-tin alloy (AuSn) is applied in a frame shape on the outer peripheral portion of the surface of the lid 5 that is joined to the container 2. The gold-tin alloy serves as a sealing material, and is heated to a predetermined temperature in a state where the gold-tin alloy is in contact with the metal film on the upper surface 210 of the upper frame portion 21 of the container 2 and the container 2 and the lid. And 5 are welded together.

The electromechanical connection between the pair of electrode pads 6 and 6 of the container 2 and the pair of connection electrodes 341 and 342 of the crystal vibrating piece 3 is performed through the conductive adhesives S and S. The conductive adhesive S in the present embodiment is an adhesive containing a metal filler in a silicone resin, and after application, curing treatment is performed in a drying oven controlled by a predetermined temperature profile. The present invention is not limited to silicone resin adhesives, and other types of resin adhesives may be used. The conductive adhesive S has better adhesion to the substrate of the quartz crystal resonator element than to the metal film forming the connection electrode.

Next, details of the quartz crystal resonator element according to the embodiment of the present invention will be described. A large number of crystal vibrating pieces 3 can be obtained at once from one AT-cut crystal wafer (hereinafter abbreviated as a crystal wafer) by using photolithography technology and wet etching.

FIG. 3 is an enlarged schematic top view of a region including one unit of the crystal vibrating piece 30 in the crystal wafer on which a large number of crystal vibrating pieces are formed. 3 to 5, the direction of the crystal axis of AT-cut quartz is indicated by an arrow. A pair of bridges (coupling portions) 35, 35 project from both end portions of one short side of the crystal vibrating piece 30 of one unit toward a linear support portion 39 in the crystal wafer. In this way, by forming the pair of bridges so as to project from both ends of one short side of the crystal vibrating piece 30, it is possible to make the plan view shape of the crystal vibrating piece after wet etching close to a substantially rectangular shape.

When the bridge is formed on one short side of the quartz crystal vibrating piece and at a position not including both ends of the one short side (for example, a central portion of the one short side), wet etching is performed due to crystal anisotropy of AT-cut quartz. The shape of the later quartz crystal vibrating piece may not be rectangular. This is a phenomenon in which the width (short side length) of the crystal vibrating piece gradually narrows in the X-axis direction (long side direction) of the AT-cut crystal as it approaches the end on the side where the bridge is formed (so-called " Side etching”). On the other hand, by forming the bridge so as to project from both ends of one short side of the crystal vibrating piece, the shape of the crystal vibrating piece in plan view can be approximated to a substantially rectangular shape. Although the number of bridges formed is two in the embodiment of the present invention, only one may be formed.

The outer shape of the crystal vibrating piece 30 including the bridge 35 and the support portion 39 is obtained by immersing (wet etching) a crystal wafer in which a predetermined area is masked with a metal film in an etching solution to form the masked area of the crystal wafer. It is molded by penetrating other regions.

Slits 36, 36 for facilitating the breaking of the crystal vibrating piece from the bridge are formed at the connecting portions of the pair of bridges 35, 35 with the crystal vibrating piece 30. The pair of slits 36, 36 are provided in parallel with the short side direction (Z′ axis direction in FIG. 3) of the crystal vibrating piece 30 from the inner side surface to the outer side surface of the pair of bridges 35, 35 in a plan view. ing. The slit 36 is formed with a length that does not extend from the inner side surface to the outer side surface of the bridge 35 in the width direction (Z′ axis direction) of the bridge 35. Further, the slit 36 is thinned to a depth of about half the thickness of the bridge 35 in a sectional view. Although the slit is formed only on one side of the bridge in the embodiment of the present invention, the slit may be formed on both sides (both main surfaces) of the bridge.

On the front and back main surfaces of the bridge 35, a pair of lead-out electrodes (reference numeral omitted) drawn from each of the pair of connecting electrodes 341, 342 are formed. The terminal ends of the pair of lead-out electrodes are respectively connected to the pair of measurement pads (not shown) formed on the front and back main surfaces of the support portion 39. The pair of measurement pads serve as electrodes for measuring the frequency of each crystal vibrating piece in the crystal wafer.

The lead-out electrode and the pair of measurement pads are collectively formed by sputtering together with the pair of excitation electrodes 32a and 32b, the extraction electrodes 33a and 33b, and the pair of connection electrodes 341 and 342 of the quartz crystal vibrating piece 30 described above. Specifically, these electrodes have a film structure in which chromium (Cr) or titanium (Ti) is used as a base layer and gold (Au) is formed thereon. The material of the underlayer and the upper layer of these electrodes is not limited to chromium and gold. At the time of the sputtering, Cr and Au ejected from the target enter the inside of the pair of slits 36, 36, so that the in-slit metal film 37 (371, 372) continues to the pair of connection electrodes 341, 342. Formed.

FIG. 4 is a schematic top view showing a state after the crystal vibrating piece 30 shown in FIG. 3 is broken off from the pair of bridges 35, 35. The crystal vibrating piece 30 is divided from the pair of bridges 35, 35 with the surface on which the slits 36, 36 are formed facing down, on the free end side of the crystal vibrating piece 30 (X-axis direction in FIG. 3). It is performed by applying mechanical stress from the lower side to the upper side of the lower surface (near the upper end of).

FIG. 5 is an enlarged perspective view of the portion B of FIG. 4, and is an enlarged perspective view of only the peripheral region including the connection electrode 342 of the crystal vibrating piece 3 after being broken off from the bridge. As shown in FIG. 5, the pair of connection electrodes 342a and 342b forming the connection electrode 342 face each other on the front and back sides of the crystal vibrating piece and have the same size. For the convenience of explanation of the application state of the conductive adhesive S, the application position of the conductive adhesive S is indicated by a chain line (the electrode pad 6 of the container is not shown).

A pair of first side surface electrodes 343 and 344 is formed near both ends of the short side surface of the one end side 3A of the crystal vibrating piece 3 having a rectangular shape in plan view. The first side surface electrodes 343 and 344 extend over the entire thickness direction of the short side surface of the one end side 3A of the crystal vibrating piece 3. That is, the first side surface electrode 344 is formed continuously with the front and back connection electrodes 342 (342a, 342b). Similarly, the first side surface electrode 343 is continuously formed with the front and back connection electrodes 341 (341a, 341b) (not shown in FIG. 5).

The breaking traces (breaking traces) 38, 38 of the traces broken off from the bridges 35, 35 become rougher than the region on the short side surface of the one end side 3A of the quartz crystal vibrating piece where the bridge is not formed. There is. The portion other than the fracture mark 38 on the short side surface of the one end side 3A of the quartz crystal vibrating piece 3 is the crystal plane of AT-cut quartz that appears by wet etching, and its surface is a smooth surface due to chemical erosion. On the other hand, the fracture mark 38 is a cleavage plane where the bridge is fractured by mechanical stress. Therefore, the smoothness of the surface of the fracture mark 38 is relatively rougher than that of the portion other than the fracture mark 38 on the short side surface of the one end side 3A.

As described above, the first side surface electrode 343 that is continuous with the connection electrode 341 and the connection electrode 342 are provided on the side surface of the crystal vibrating piece 3 on the short side where the connection electrodes 341 and 342 are formed (the short side of the one end side 3A). The first side surface electrode 344 continuous with is formed, and the fracture marks 38, 38 of the crystal vibrating piece 3 are exposed.

Next, the pair of exposed portions 9, 9 formed on the connection electrodes 341, 342 of the crystal vibrating piece 3 will be described in detail. In the present embodiment, the diameter of one exposed portion 9 is 0.02 mm. The opening area of one exposed portion 9 is 1.9% of the area of one connection electrode (341 or 342) in plan view.

Next, Table 1 and FIGS. 6 to 8 show the ratio (area ratio) of the opening area in plan view of one exposed portion to the area in plan view of one connection electrode in which the exposed portion is formed. Will be described with reference to. Table 1 shows the trial production results under the eight conditions regarding the exposed portion. In Conditions 1 to 5, the center position of the exposed portion with respect to the connection electrode is fixed and only the diameter of the exposed portion is changed. On the other hand, in Conditions 6 to 8, the diameter of the exposed portion is constant and only the position of the exposed portion is changed. The number of samples under each condition is five.

The conditions 1 to 5 are the positions spaced 0.05 mm apart from each inner edge of the pair of connection electrodes 341 and 342 in the short side direction of the crystal vibrating piece 3 to the outside (direction toward the corners of both ends of the short side). , The center O of the exposed portions 9 and 9 is set (see FIG. 4). The distance from the inner edges of the pair of connection electrodes 341 and 342 to the centers O of the exposed portions 9 and 9 is represented by the symbol C in FIG. The diameter of the exposed portion 9 which is circular in a plan view is decreased by 0.01 mm from 0.06 mmΦ in condition 1 to condition 5 and is 0.02 mmΦ in condition 5.

As shown in FIG. 4, in the present embodiment, the connection electrode 341 (same for 342) is rectangular in plan view. The long side length Lt of the connection electrode 341 (342) is 0.175 mm, and the short side length Wt is 0.0935 mm. Therefore, the area S2 of one connection electrode 341 (342) in plan view is Lt×Wt=0.175 mm×0.0935 mm=16,363 mm ² . From this, in the conditions 1 to 8, the ratio S1/S2 of the opening area S1 of one exposed portion to the area S2 of one connection electrode in plan view (hereinafter, abbreviated as the exposed area ratio S1/S2) is: It is 1.9% to 17.3%.

The evaluation of the prototype under the conditions 1 to 8 was performed by the reflow characteristics of the crystal oscillator. Specifically, while holding the temperature of +160°C to +180°C for 120 seconds and putting the peak temperature of +220°C or higher for at least 65 seconds, the crystal oscillator is thrown into the reflow furnace 3 times and the reflow is performed. The oscillation frequency of the crystal oscillator was measured every time it was charged into the furnace. The oscillation frequency is measured after taking out the prototype from the reflow furnace and leaving it at room temperature for 2 hours.

The evaluation index of each condition includes the variation “ΔF/F_3σ” of frequency deviation (ΔF/F) at each of the first, second, and third reflows (3σ is a value three times the standard deviation σ), and the reflow 1 The minimum value “ΔF/F_Min” of the frequency deviation (ΔF/F) in each of the second, third and third times was used. Note that “ΔF/F_3σ (minimum)” in Table 1 represents the minimum value of “ΔF/F_3σ” in each of the first to third reflow processes. Similarly, “ΔF/F_3σ (maximum)” represents the maximum value of “ΔF/F_3σ” in each of the first to third reflow processes. Further, “ΔF/F_Min (minimum)” in Table 1 represents the minimum value of “ΔF/F_Min” in each of the first to third reflow processes. Similarly, “ΔF/F_Min (maximum)” represents the maximum value of “ΔF/F_Min” in each of the first to third reflow processes.

FIG. 7 shows a graph showing the relationship between the area ratio S1/S2 of the exposed portion under the conditions 1 to 5 and the variation ΔF/F_3σ of the frequency deviation. Further, FIG. 8 shows a graph showing the relationship between the area ratio S1/S2 of the exposed portion under the conditions 1 to 5 and the minimum value ΔF/F_Min of the frequency deviation. For comparison and comparison with the present invention, FIG. 6 shows the reflow resistance characteristics of the conventional crystal oscillator. In this conventional crystal oscillator, no exposed portion is formed on the connection electrode of the crystal vibrating piece. As shown in FIG. 6, in the conventional crystal oscillator in which the exposed portion is not formed in the connection electrode, all the data exceed ±1 ppm which is the quality determination standard (standard value) of the frequency deviation ΔF/F. There is.

As shown in FIG. 7, under the conditions 1 to 5 in which only the diameter of the exposed portion was varied, the variation ΔF/F_3σ in the frequency deviation tended to decrease as the diameter of the exposed portion decreased. However, under the conditions 3 (diameter 0.04 mm) to condition 5 (diameter 0.02 mm), the decrease of the frequency deviation ΔF/F was slowed down, and it was observed that the amount of change tended to be small.

On the other hand, in FIG. 8, the minimum value ΔF/F_Min of the frequency deviation tends to increase as the diameter of the exposed portion decreases. However, under the conditions 3 (diameter 0.04 mm) to condition 5 (diameter 0.02 mm), it was observed that the minimum value ΔF/F_Min of the frequency deviation slowed down and the amount of change tended to decrease.

As described above, under the conditions 1 and 2 in which the diameter of the exposed portion is relatively large among the conditions 1 to 5, there is a tendency that the variation ΔF/F_3σ of the frequency deviation is large and the minimum value ΔF/F_Min of the frequency deviation is small. .. It is considered that this is because as the diameter of the exposed portion is larger, the joining force by the exposed portion becomes too strong and is more susceptible to the stress caused by the joining.

In the present embodiment, the quality determination criterion of the frequency deviation variation ΔF/F_3σ is within 0.5 ppm, and the quality determination criterion of the minimum frequency deviation ΔF/F_Min is within ±1.0 ppm. Therefore, from FIGS. 7 and 8, “Condition 3 (diameter 0.04 mm) to Condition 5 (diameter 0.02 mm)” is the pass/fail judgment criterion of the variation ΔF/F_3σ of the frequency deviation and the minimum value ΔF/F_Min of the frequency deviation. In addition, it is preferable to take into consideration the blunting of each change amount. Therefore, the range of the area ratio S1/S2 of the exposed portion is preferably 1.9% or more and 7.7% or less corresponding to the conditions 3 to 5. Note that “condition 5” is preferable in which the range between the maximum value and the minimum value of the frequency deviation deviation ΔF/F_3σ is the smallest and the minimum value of the frequency deviation ΔF/F_Min is the largest. The exposed portion 9 in this embodiment is formed under the condition 5.

As described above, in one connection electrode 341 (or 342), the opening area of one exposed portion 9 is 1.9% or more and 7.7% of the area of the connection electrode 341 (or 342) in plan view. By the following, it is possible to improve the adhesion between the crystal vibrating piece 3 and the conductive adhesive S and suppress the variation in the frequency deviation in the reflow resistance characteristic of the crystal oscillator 1. This is for the following reason. That is, when the opening area of one exposed portion 9 is 1.9% or less of the area of one connection electrode 341 (or 342) provided with the exposed portion in plan view, the bonding by the exposed portion 9 The effect of improving power becomes poor. On the contrary, if the opening area of the exposed portion 9 is 7.7% or more of the area of the connection electrode 341 (or 342) in plan view, the bonding force of the exposed portion 9 becomes too strong and the stress caused by the bonding is increased. It becomes easy to be affected by.

As shown in FIG. 2, the pair of exposed portions 9 and 9 having a circular shape in plan view are formed such that their centers O and O are aligned along one short side of the quartz crystal vibrating piece 3. The pair of exposed portions 9 and 9 are arranged in line symmetry with respect to the virtual straight line VL passing through the centers of the two opposing short sides of the crystal vibrating piece 3.

The length H of the line segment connecting the centers O and O of the pair of exposed portions 9 and 9 (distance between the centers O and O) is 42.2% with respect to the length W of the short side of the quartz crystal vibrating piece 3. (See FIG. 4). The relationship between the length H of the line connecting the centers O of the pair of exposed portions 9 and O and the short side dimension W of the quartz crystal vibrating piece will be described below.

FIG. 9 is a graph showing the relationship between the distance C from the inner edge of the connection electrode to the center of the exposed portion (see FIG. 4) and the frequency deviation variation ΔF/F_3σ under the conditions 3 and 6 to 8 in Table 1. FIG. 10 shows a graph of the relationship between the distance C from the inner edge of the connection electrode to the center of the exposed portion and the minimum frequency deviation value ΔF/F_Min under conditions 3 and 6 to 8. The length W of the short side of the crystal vibrating piece 3 in the present embodiment is 0.45 mm, and the distance G between the inner edges of the pair of connection electrodes 341 and 342 in the short side direction of the crystal vibrating piece 3 (see FIG. 4). ) Is 0.09 mm. Further, under the conditions 3 and 6 to 8 in Table 1, the diameter of the exposed portion is constant at 0.04 mm.

As shown in FIG. 9, under the conditions 3 and 6 to 8 in which the diameter of the exposed portion is constant and only the position of the exposed portion, that is, only the distance C from the inner edge of the connecting electrode to the center of the exposed portion is changed. It was observed that the variation ΔF/F_3σ in the frequency deviation tended to decrease as the distance C from the inner edge to the center of the exposed portion increased. However, in condition 3 (C=0.05 mm), condition 7 (C=0.09 mm), and condition 8 (C=0.13 mm), the variation ΔF/F_3σ in the frequency deviation slows down and the amount of change is small. Was observed.

On the other hand, in FIG. 10, the minimum value ΔF/F_Min of the frequency deviation tended to generally increase as the distance C from the inner edge of the connection electrode to the center of the exposed portion increased.
It could be confirmed. However, in the condition 3 (C=0.05 mm), the condition 7 (C=0.09 mm), and the condition 8 (C=0.13 mm), the increase of the minimum value ΔF/F_Min of the frequency deviation slows down, and the change amount is The tendency was to decrease.

In FIG. 9, it can be determined that the conditions 3 and 8 are levels that pose no practical problems in light of the quality determination criteria (within 0.5 ppm) of the frequency deviation variation ΔF/F_3σ. Further, in FIG. 10, it can be determined that the conditions 3 and 7 are at a level in which there is practically no problem in light of the quality determination criterion (within ±1.0 ppm) of the minimum value ΔF/F_Min of the frequency deviation. Therefore, in consideration of both the determination criteria of the variation ΔF/F_3σ of the frequency deviation and the minimum value ΔF/F_Min of the frequency deviation, “Condition 3” is preferable in Conditions 3 and 6 to 8.

In this “condition 3”, the ratio H/W between the distance H between the centers O of the pair of exposed portions 9, 9 and the short side dimension W of the quartz crystal vibrating piece is 42.2%. The H/W is also 42.2% under "Conditions 3 to 5", which is the preferable range of the area ratio S1/S2 of the exposed portion. “H” in the conditions 3 to 5 is 0.19 mm, and considering the manufacturing error (±0.005 mm) of the short side dimension W of the quartz crystal resonator element, the ratio H/W is 41.8%. The preferable range is ˜42.7%.

When both ends (both corners) of one short side of the crystal vibrating piece are firmly joined by the conductive adhesive, the oscillation frequency of the crystal oscillator tends to change easily due to the influence of the stress related to the joining. On the other hand, as in the present invention, the exposed portions 9 and 9 provided in each of the pair of connection electrodes 341 and 342 are imaginary straight lines VL passing through the centers of the two short sides of the crystal vibrating piece 3. The length H of the line segment connecting the centers O of the pair of exposed portions 9, 9 with respect to the short side length W of the quartz crystal vibrating piece 3 is 41.8. % To 42.7%. With such a structure, the portion of the crystal vibrating piece 3 near the center of one short side is firmly joined. With this, compared to the configuration in which the exposed portion is provided near both ends of the short side of the quartz crystal vibrating piece, in the present invention, since the vicinity of both ends of the short side is not firmly joined, the influence of stress related to joining is reduced. be able to.

As shown in FIG. 2, each outer edge of the conductive adhesives S, S in the extending direction of the short sides of the crystal vibrating piece 3 (vertical direction in FIG. 2) has a short length on one end side 3A of the crystal vibrating piece 3 in plan view. It extends outward beyond both corners C1 and C1 of the side. However, the outer edge of the conductive adhesive with respect to the quartz crystal vibrating piece in the present invention in plan view is not limited to only the outer edge beyond both corners of one short side of the quartz vibrating piece. That is, the outer edge of the conductive adhesive with respect to the crystal vibrating piece in the present invention in plan view may be located inside both corners C1 and C1 of one short side of the crystal vibrating piece 3. In this case, the influence of the stress transmitted from the container 2 joined to the external substrate to the crystal vibrating piece 3 can be suppressed. Thereby, the stability of the oscillation frequency of the crystal oscillator 1 can be improved.

In the embodiment of the present invention, the crystal vibrating reed 3 is placed on the electrode pad (not shown) in a state where the conductive adhesive S reaches both the break mark 38 and the first side surface electrode 344 as shown in FIG. Is electrically conductively bonded to. Specifically, in the embodiment of the present invention, in the quartz crystal vibrating piece 3, the conductive adhesives S, S have break marks 38, 38, first side surface electrodes 343 (not shown in FIG. 5), 344, and slits. The inner metal films 371 (not shown in FIG. 5) and 372 are conductively bonded onto the electrode pads 6 and 6 in a state of reaching the inner metal films 371 and 372. Further, the conductive adhesives S, S are in a state of reaching the base materials of the two long side surfaces of the crystal vibrating piece 3 which face each other.

According to the above configuration, the quartz crystal vibrating piece 3 has the pair of electrode pads 6, 6 with the conductive adhesive S, S reaching not only the first side surface electrodes 343, 344 but also the break marks 38, 38. Since it is conductively bonded to the upper part, the adhesion between the crystal vibrating piece 3 and the conductive adhesive S can be improved. This is because the bonding force can be supplemented by the base material of the crystal vibrating reed 3 having excellent adhesion with the conductive adhesive S. Furthermore, since the conductive adhesive S extends to the crystal bases on the two opposing long side surfaces of the crystal vibrating piece 3 in addition to these, the bonding strength can be further improved.

-Other embodiments of the present invention-
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 11 is an enlarged perspective view of only the peripheral region including the connection electrode 132 of the crystal vibrating piece 10 after being broken off from the bridge. The same components as those in the embodiment of the present invention described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, differences from the above-described embodiment of the present invention will be mainly described.

In another embodiment of the present invention, the shape of the crystal vibrating piece and the application form of the conductive adhesive are different from the above-described embodiments of the present invention. First, regarding the shape of the crystal vibrating piece, as shown in FIG. 11, the inclined surfaces 11 (11 a, 11 b) appear on each of the long side surfaces of the set of crystal vibrating pieces 10. Further, the inclined surfaces 12 (12 a, 12 b) also appear on each of the short side surfaces of the pair of crystal vibrating pieces 10.

Regarding the inclined surface 11 on the long side of the crystal vibrating piece 10, the inclined surface 11a forms an obtuse angle α with the main surface of the crystal vibrating piece 10 (the lower main surface in FIG. 11). Is becoming The angle β formed between the inclined surface 11a and the inclined surface 11b is also an obtuse angle.

On the other hand, regarding the inclined surface 12 on the side surface on the short side of the crystal vibrating piece 10, an angle γ formed between the inclined surface 12a and one principal surface (the lower main surface in FIG. 11) of the crystal vibrating piece 10, The angle δ formed between the inclined surface 12a and the inclined surface 12b and the angle ε formed between the inclined surface 12b and the other main surface (upper main surface in FIG. 11) of the crystal vibrating piece 10 are all obtuse angles. There is. In addition, regarding each inclined surface of the side surface on the long side and the side surface on the short side of the crystal vibrating piece, the angle formed between the main surface of the crystal vibrating piece and the inclined surface continuous with the main surface of the crystal vibrating piece, and between the plurality of inclined surfaces Since the formed angle changes depending on the etching conditions, not all of these angles are obtuse angles, and obtuse angles and acute angles may coexist.

The inclined surfaces 11a and 11b and the inclined surfaces 12a and 12b are crystal planes of AT-cut quartz that appear by wet etching, and the number of appearances and the angle formed between the plurality of inclined planes change according to the etching conditions, so that the quartz vibrating reed is produced. The shape of can change. Therefore, the appearance of the inclined surface of the crystal vibrating piece shown in FIG. 11 is merely an example, and the application of the present invention is not limited to the number of appearance of the inclined surface of the crystal vibrating piece and the side surface shape shown in FIG. 11. ..

Further, due to the anisotropy of the AT-cut quartz crystal, the cross-sectional shape of the quartz crystal vibrating piece having a rectangular shape in plan view is different at both ends in the long side direction and both ends in the short side direction. In particular, when the X-axis of the AT-cut crystal is set on the long side of the rectangular quartz crystal vibrating piece in plan view and the Z′-axis of the AT-cut crystal is set on the short side as shown in FIGS. The cross-sectional shapes at both ends of the are greatly different depending on the etching conditions. Although the AT-cut quartz has such a property, the application of the present invention is not limited to the crystal axis direction shown in FIGS. 3 to 5, and the Z′ axis is on the long side of the crystal vibrating piece having a rectangular shape in plan view. The X axis may be set on the short side.

Second side surface electrodes 141 (not shown in FIG. 11) and 142 are formed on the inclined surfaces 11 and 11 of the pair of crystal vibrating reeds 10 on the long side surfaces. Specifically, the second side surface electrode 141 is adjacent to the fracture mark 16 (one of the pair of fracture marks 16, 16) and is continuous with the connection electrode 131 (131a, 131b, not shown in FIG. 11). Is formed. Similarly, the second side surface electrode 142 is adjacent to the breakage mark 16 (the other of the pair of breakage marks 16 and 16) and is formed continuously with the connection electrode 132 (132a, 132b). Further, first side surface electrodes 133 (not shown in FIG. 11) and 134 are formed on the inclined surfaces 12 (12 a, 12 b) on the side surface on the one short side of the crystal vibrating piece 10.

In another embodiment of the present invention, similarly to the above-described embodiments of the present invention, a slit is formed in each of the pair of bridges before the bridge is broken. Therefore, the in-slit metal film 15 (151 (not shown in FIG. 11), 152) is attached to the inside of each of the pair of slits. The in-slit metal films 15 (151, 152) are continuously formed on the pair of connection electrodes 131a, 132a, respectively, and also on the adjacent first side surface electrodes 133 (not shown in FIG. 11), 134. Each is formed continuously.

Next, regarding the application form of the conductive adhesive, as shown in FIG. 11, the conductive adhesive S includes the connection electrode 131b (132b is the same), the first side surface electrode 134 (133 is the same), and the break mark 16 And the in-slit metal film 152 (151 is also the same) and the second side surface electrode 142 (141 is the same). Although the second side surface electrodes 141 and 142 are formed in the other embodiment of the present invention, the second side surface electrodes may not be formed. That is, the first side surface electrode 133 (134) may secure the electrical connection between the front and back connection electrodes 131a (132a) and 131b (132b) of the crystal vibrating piece 10.

According to the configuration of another embodiment of the present invention, not only is the crystal vibrating piece 10 connected to the connection electrodes 131 and 132 so that the conductive adhesives S and S cover the exposed portions 9 and 9, Since the first side surface electrodes 133 and 134 and the fracture marks 16 and 16 are bonded to the electrode pad in a state of reaching the fracture marks 16 and 16, the adhesion between the crystal vibrating piece 10 and the conductive adhesive S can be further improved. .. This is because the conductive adhesive S extends not only to the exposed portion 9 that has excellent adhesion to the conductive adhesive S, but also to the fracture mark 16 whose surface is rougher than the exposed portion 9, so-called "anchor". This is because the “advantage” further improves the adhesion between the crystal vibrating piece 10 and the conductive adhesive S.

Further, according to the configuration of another embodiment of the present invention, the quartz crystal vibrating piece 10 includes the conductive adhesive S as well as the connection electrodes 131 and 132, the first side surface electrodes 133 and 134, and the breakage mark 16 as well as the connection electrode. The second side surface electrodes 141 and 142 continuous with 131 and 132 are also connected to the electrode pads. That is, since the conductive adhesive S, S extends to the connection electrodes 131 and 132 including the exposed portions 9 and 9 and the break marks 16 and 16, as well as the second side surface electrodes 141 and 142, the crystal vibrating piece 10 of The conductive adhesive S is arranged so as to extend over the short side and the long side adjacent to the short side. Thereby, the adhesiveness between the crystal vibrating piece 10 and the conductive adhesive S is further enhanced, and the bonding force can be improved.

Further, according to the configuration of another embodiment of the present invention, it is possible to improve the connection reliability between the front and back main surfaces of the crystal vibrating piece 10. This will be described below. Inclined surfaces 11 and 11 are included in the side surface on the long side of the pair of crystal vibrating pieces 10. The second side surface electrode 141 is formed so as to extend from the connection electrode 131 (131a, 131b) to the inclined surface 11 (11a, 11b) (not shown in FIG. 11). Similarly, the second side surface electrode 142 is formed so as to extend from the connection electrode 132 (132a, 132b) to the inclined surface 11 (11a, 11b). With such a configuration, the angle formed by the plurality of surfaces can be made gentler than the configuration in which the side surface of the crystal vibrating piece is perpendicular to the main surface of the crystal vibrating piece. Thereby, disconnection of the side surface electrode can be prevented. The same effect can be applied to the first side surface electrodes 133 and 134 formed on the inclined surfaces 12 and 12 on the side surface on the one short side of the crystal vibrating piece 10.

In the above-described embodiments of the present invention and other embodiments, the crystal vibrating piece is conductively bonded on the electrode pad on the upper surface of the protruding portion in a cantilevered state, but the protruding portion or step is also formed on the free end side of the crystal vibrating piece. A part may be formed and conductively joined in a both-supported state.

In addition, in the embodiment of the present invention and other embodiments, the number of connections for conductively joining the crystal vibrating piece and the container is two, but the number of connections is not limited to two, and is two. It may be more than. Further, the number of bridges formed in one crystal vibrating piece is not limited to two, and one or more bridges may be formed.

Further, regarding the bonding of the crystal vibrating piece according to the present invention to the electrode pad via the conductive adhesive, even if the crystal vibrating piece of the form shown in FIG. 5 and FIG. Good.

Further, in the above-described embodiments of the present invention and other embodiments, the conductive adhesive was applied to the upper surfaces of the pair of electrode pads only once (so-called “undercoating”), but the conductive adhesive coated under such a condition was used. A conductive adhesive may be further applied over the conductive adhesive (so-called “overcoat”).

In the above-described embodiment of the present invention and the other embodiments, the crystal oscillator having a structure in which the cross-sectional shape of the container is the letter “H” is taken as an example, but the application of the present invention is applied to the crystal oscillator having the structure. Not limited to this, the present invention is also applicable to a crystal oscillator in which an electronic component element and a crystal vibrating piece are housed inside a recess that is open only above, and a lid is joined to the opening end of the recess.

Further, in the above-described embodiments of the present invention and other embodiments, the crystal oscillator is described as an example of the piezoelectric device, but the present invention is not limited to the crystal oscillator, and the crystal resonator in which only the crystal vibrating piece is housed in the container Alternatively, the present invention can be applied to a temperature sensor built-in type crystal resonator in which a crystal vibrating piece and a temperature sensor are built in a container.

The present invention can be embodied in various other forms without departing from the spirit or the main characteristics thereof. Therefore, the above-described embodiments are merely examples in all respects and should not be limitedly interpreted. The scope of the present invention is defined by the scope of the claims, and is not bound by the text of the specification. Furthermore, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

It can be applied to mass production of piezoelectric devices.

1 crystal oscillator 2 container 3, 10 crystal vibrating piece 4 IC
5 Lid 6 Electrode Pad 9 Exposed Part 16, 38 Break Trace 131, 132, 341, 342 Connection Electrode 133, 134, 343, 344 First Side Electrode 141, 142 Second Side Electrode S Conductive Adhesive

Claims (2)

A piezoelectric vibrating reed having a substantially rectangular shape in a plan view,
At both ends of at least one short side on the front and back main surfaces of the piezoelectric vibrating piece, a pair of connection electrodes to be joined to the outside are provided apart from each other,
In each of the regions of the pair of connection electrodes, an exposed portion in which the substrate of the piezoelectric vibrating piece is exposed is provided,
In one of the connection electrodes, an opening area of the exposed portion is 1.9% or more and 7.7% or less of an area of the connection electrode in plan view. A piezoelectric device in which the piezoelectric vibrating piece according to claim 1 is bonded to an electrode pad provided inside a container via a conductive adhesive, and a lid is bonded to the container to hermetically seal the piezoelectric device. There
A pair of first side surface electrodes that are continuous with each of the pair of connection electrodes are formed on the side surfaces of the one short side of the piezoelectric vibrating piece where the pair of connection electrodes are formed, and a break mark of the piezoelectric vibration piece is formed. Is exposed,
The piezoelectric vibrating piece is bonded to the electrode pad in a state where the conductive adhesive reaches at least the pair of connection electrodes, the pair of first side surface electrodes, and the breakage trace so as to cover the exposed portion. Piezoelectric device characterized in that.

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