JP7305948B2 - Piezoelectric vibrating piece and piezoelectric device using the piezoelectric vibrating piece - Google Patents

Description

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

In recent years, piezoelectric devices such as crystal resonators and crystal oscillators have been miniaturized. For example, the external dimensions of surface-mounted crystal oscillators, which are substantially rectangular in plan view, are 1.6 mm or less in the long side and 1.2 mm or less in the short side.

To give a representative example of the crystal oscillator, the crystal oscillator includes a package (container) made of an insulating material having a recess opening upward, and a cantilever at one end of the package (container) inside the recess with a conductive adhesive interposed therebetween. It is composed of a bonded crystal vibrating piece and a lid bonded to the opening end of the package so as to cover the concave portion of the package in which the crystal vibrating piece is accommodated. As the crystal vibrating piece becomes ultra-miniature, its outer shape is formed using photolithography technology or wet etching (etching by chemical dissolution by immersing a crystal wafer in an etching solution). . A method for manufacturing such a crystal vibrating piece is disclosed in Patent Documents 1 and 2, for example.

A piezoelectric device is measured for reflow resistance in its environmental performance test. This reflow resistance characteristic is determined by whether or not the amount of change in the oscillation frequency of the piezoelectric device after passing the piezoelectric device through a reflow oven set to predetermined temperature conditions a predetermined number of times satisfies a predetermined criterion. It is a test to judge.

For example, in the case of crystal vibrating pieces having conventional external dimensions, the reflow resistance has not been regarded as a problem until now. However, in the case of an ultra-compact crystal vibrating piece, the amount of change in the oscillation frequency of the crystal vibrator did not meet the criteria, and was rejected. This change in 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 the oscillation frequency also increases.

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

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piezoelectric device having excellent reflow resistance even when the piezoelectric vibrating reed is extremely small.

In order to achieve the above object, the invention of claim 1 has a crystal vibrating piece that is approximately rectangular in plan view and cantilever bonded to an electrode pad provided inside a container via a conductive adhesive, and a lid is attached to the container. The quartz crystal oscillation device is hermetically sealed by joining the crystal oscillation device, the crystal oscillation device is substantially rectangular in plan view, and has external dimensions of 1.6 mm in the vertical direction and 1.2 mm in the horizontal direction, The conductive adhesive is made of a silicone-based resin adhesive , and the crystal vibrating piece is a flat plate having a rectangular shape in a plan view, and the length of the short side is 0.45 mm. At both ends of at least one short side of the plane, a pair of connection electrodes to be connected to the outside are provided separately from each other, and the connection electrodes have a film structure in which an upper layer is laminated on a base layer, and the upper layer is gold. In each region of the pair of connection electrodes, there is provided an exposed portion where the base material of the crystal vibrating piece is exposed, and in one of the connection electrodes, the opening area of the exposed portion is the connection It is characterized by being 1.9% or more and 7.7% or less with respect to the area of the electrode in plan view.

According to the above invention, it is possible to suppress the amount of change in the oscillation frequency of the crystal oscillation device. This is because an exposed portion is provided in the region of the connection electrode, which has better adhesion to the conductive adhesive than the metal forming the connection electrode. In other words , the exposed part where the base material of the crystal vibrating piece is exposed improves the adhesion between the crystal vibrating piece and the conductive adhesive, and the bonding is strong. This is because the stress can be made difficult to change.

Further, according to the above invention, in one of the connection electrodes, the open 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 a plan view . While improving the adhesion between the vibrating piece and the conductive adhesive, it is possible to suppress variations in the frequency deviation in the reflow resistance characteristics of the crystal oscillation device.

In order to achieve the above object, the invention according to claim 2 is characterized in that, on the side surface of one short side of the crystal vibrating piece on which the pair of connection electrodes are formed, a pair of electrodes continuous with each of the pair of connection electrodes is provided. The first side electrodes are formed and the fracture traces of the crystal vibrating piece are exposed, and the conductive adhesive covers at least the pair of connection electrodes and the pair of first side electrodes so as to cover the exposed portions. and the crystal vibrating piece is bonded to the electrode pad in a state where the break mark is reached.

According to the above invention, the crystal vibrating piece is not only connected to the connection electrode so that the conductive adhesive covers the exposed portion, but also extends to the first side electrode and the fracture mark on the electrode pad. Since they are bonded, the adhesion between the crystal vibrating piece and the conductive adhesive can be further improved. This is because the conductive adhesive extends not only to the exposed portion, which has excellent adhesion to the conductive adhesive, but also to the rupture trace, which has a rougher surface than the exposed portion. This is because the adhesion between the crystal vibrating piece and the conductive adhesive is further improved.

A pair of second side electrodes may be formed on a set of side surfaces of the long sides of the crystal vibrating piece having a rectangular shape in plan view, the pair being continuous with the pair of connection electrodes. Then, in a state where the conductive adhesive covers all of the pair of connection electrodes, the pair of first side electrodes, the fracture marks, and the pair of second side electrodes so as to cover the exposed portions, the crystal vibrating piece may be joined to the electrode pads. In this configuration, the conductive adhesive extends to the second side electrode in addition to the connection electrode including the exposed portion, the first side electrode, and the fracture trace, so that the short side of the crystal vibrating piece and the short side adjacent to the short side The conductive adhesive is arranged so as to straddle the long sides. As a result, the adhesion between the crystal vibrating piece and the conductive adhesive is enhanced, and the bonding strength 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-compact piezoelectric vibrating reed.

Schematic cross-sectional view of a crystal oscillator according to an embodiment of the present invention FIG. 2 is a schematic top view of the quartz oscillator according to the embodiment of the present invention, excluding the lid; FIG. 2 is a schematic top view of the crystal vibrating piece before breaking off according to the embodiment of the present invention; FIG. 2 is a schematic top view of the crystal vibrating piece after breaking off according to the embodiment of the present invention; Enlarged perspective view of B part of FIG. Reflow resistance characteristics of conventional crystal oscillators Reflow Resistance Characteristics of Crystal Oscillators According to Embodiments of the Present Invention Reflow Resistance Characteristics of Crystal Oscillators According to Embodiments of the Present Invention Reflow Resistance Characteristics of Crystal Oscillators According to Embodiments of the Present Invention Reflow Resistance Characteristics of Crystal Oscillators According to Embodiments of the Present Invention FIG. 2 is an enlarged perspective view of a crystal vibrating piece according to another embodiment of the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS A temperature-compensated crystal oscillator will be described below as an example of a piezoelectric device according to an embodiment of the present invention with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a crystal oscillator according to an embodiment of the present invention taken along line AA in FIG. First, the outline of each member constituting the crystal oscillator will be described, and then the crystal vibrating piece will be described in detail.

In FIG. 1, a crystal oscillator 1 has 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, etc. are integrated into one chip is used. The outer 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. Note that the outer dimensions of the crystal oscillator in a plan view are an example, and dimensions other than the outer dimensions may be used.

In FIG. 1, the container 2, which is substantially rectangular in plan view, includes a flat substrate portion 20, an upper frame portion 21 extending upward from the outer peripheral edge of one main surface 201 that is the upper surface of the substrate portion 20, and a lower surface of the substrate portion 20. and a 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 having a predetermined shape is formed between the layers of these three sheets.

A space formed by the upper frame portion 21 and one main surface 201 of the substrate portion 20 is an upper concave portion E1, which is substantially rectangular in plan view. As shown in FIG. 2, a pair of electrode pads (crystal vibrating piece mounting pads) 6, 6 are spaced apart from each other on one short side of the inner bottom surface (one main surface 201) of the upper recess E1. are formed in parallel. The pair of electrode pads 6, 6 are pads to which a connection electrode (described later) on one end side 3A of the crystal vibrating piece 3 is cantilevered with conductive adhesives S, S interposed therebetween. In this embodiment, the pair of electrode pads 6, 6 has a laminated structure in which an electrolytic nickel plating layer is formed on a tungsten metallization layer, and an electrolytic gold plating layer is further formed thereon. A metal film (not shown) is formed in the shape of a frame 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 concave portion E2, which is substantially rectangular in plan view. Six electronic component element mounting pads (hereinafter abbreviated as IC mounting pads) electrically connected to the electronic component element 4 are formed on the inner bottom surface (the other main surface 202) of the lower recess E2. Six functional terminals provided on the active surface side of the IC are electrically connected one-to-one to each of these six IC mounting pads via six metal bumps (not shown). An insulating resin (underfill) 8 is arranged in the gap between the inner bottom surface of the lower recess E2 in which six IC mounting pads are formed 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 connected to a pair of crystal terminals via internal wiring (not shown) and castellations (not shown; conductors formed on the outer surface of the substrate portion 20). They are electrically connected to electrode pads 6, 6, respectively. Temperature information of the crystal vibrating piece 3 is detected by a temperature sensor incorporated 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 , via lands and solder of the external substrate. spliced. These external connection terminals 7, 7, 7, 7 and the metal film of the upper surface 210 of the upper frame portion 21 are also configured such that a nickel plating layer and a gold plating layer are laminated in this order on the metallized layer of tungsten. It has become. Molybdenum (Mo) or titanium (Ti) may be used for the metallized layer other than tungsten.

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

Excitation electrodes for driving the crystal diaphragm are provided on the central sides of each of one principal surface (front surface in FIG. 1) of the crystal vibrating piece 3 and the other principal surface (back surface in FIG. 1) facing the one principal surface. 32a and 32b are formed as a pair so as to face each other. In the drawings, various electrodes on one main surface side of the quartz crystal diaphragm are denoted by a at the end of the reference numerals, and electrodes on the other main surface of the quartz oscillation plate are denoted by b at the end of the reference numerals. The electrodes on the front and back of the diaphragm are distinguished.

As shown in FIG. 2, the pair of excitation electrodes 32a and 32b are formed with extraction electrodes 33a and 33b that are extracted in the same direction. A pair of connection electrodes 341 and 342 are connected to the ends of the extraction electrodes 33a and 33b and conductively joined to the pair of electrode pads 6 and 6 of the container 2, respectively, on one end side 3A of the crystal vibrating piece 3. 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 deposited 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 deposited 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, 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 region of the connection electrodes 341 and 342 and have better adhesion to the conductive adhesive S than the metal forming the connection electrodes 341 and 342 . In other words, 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, so that the crystal vibrating piece 3 and the conductive adhesive S are firmly bonded. This is because the stress acting on the crystal vibrating piece 3 can be made difficult to change.

A part of one connection electrode 341 extends from the connection electrode 341b (see FIG. 1) on the other main surface of the crystal vibrating piece 3 to the one main surface 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 connection electrode 342 extends from the connection electrode 342a on one principal surface of the crystal vibrating piece 3 to the connection electrode 342a on the other principal surface via the short side surface of the one end side 3A of the crystal vibrating piece 3. It is connected to an electrode 342b (reference numerals are omitted in FIG. 2). The pair of connection electrodes 341 and 342 have opposite 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 a Kovar base material. A gold-tin alloy (AuSn) is coated in a frame shape on the outer peripheral portion of the surface of the lid 5 that is to be joined to the container 2 . This gold-tin alloy serves as a sealing material, and the gold-tin alloy and the metal film on the upper surface 210 of the upper frame portion 21 of the container 2 are heated to a predetermined temperature while being in contact with each other, thereby separating the container 2 and the lid. 5 are welded.

The electromechanical connection between the pair of electrode pads 6, 6 of the container 2 and the pair of connection electrodes 341, 342 of the crystal vibrating piece 3 is made through conductive adhesives S, S. The conductive adhesive S in this embodiment is an adhesive in which a metal filler is contained in a silicone resin, and after coating, is cured in a drying oven controlled with a predetermined temperature profile. The present invention is not limited to silicone-based resin adhesives, and other types of resin adhesives may be used. The conductive adhesive S has better adhesion to the base material of the crystal vibrating piece than to the metal film forming the connection electrodes.

Next, details of the crystal vibrating piece according to the embodiment of the present invention will be described. A large number of crystal vibrating pieces 3 are collectively obtained from one AT-cut crystal wafer (hereinafter, abbreviated as crystal wafer) by using photolithography and wet etching.

FIG. 3 is an enlarged schematic top view of a region including one unit of crystal vibrating piece 30 in a crystal wafer on which a large number of crystal vibrating pieces are molded. In FIGS. 3 to 5, the directions of crystal axes of AT-cut quartz are indicated by arrows. A pair of bridges (connecting portions) 35 protrude from both ends 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 a pair of bridges protruding from both ends of one short side of the crystal vibrating piece 30, the planar view shape of the crystal vibrating piece after wet etching can be approximated to a substantially rectangular shape.

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

The external shape of the crystal vibrating piece 30, including the bridges 35 and the support portions 39, is obtained by immersing (wet etching) a crystal wafer masked with a metal film in predetermined areas in an etchant so that the masked areas of the crystal wafer are etched. It is molded by penetrating the area other than.

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

A pair of lead-out electrodes (reference numerals omitted) led out from each of the pair of connection electrodes 341 and 342 are formed on the front and back main surfaces of the bridge 35 . Terminals of the pair of lead-out electrodes are connected to a pair of measurement pads (not shown) formed on the front and back main surfaces of the support portion 39, respectively. This pair of measurement pads serves as electrodes for measuring the frequency of each crystal vibrating piece in the crystal wafer.

The lead-out electrodes and the pair of measurement pads are formed together with the pair of excitation electrodes 32a and 32b, the lead-out electrodes 33a and 33b, and the pair of connection electrodes 341 and 342 of the crystal vibrating piece 30 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 deposited thereon. Materials for the underlying layer and the upper layer of these electrodes are not limited to chromium and gold. During 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 films 37 (371, 372) are continuous with the pair of connection electrodes 341, 342. formed by

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 by separating the free end side of the crystal vibrating piece 30 (X-axis direction in FIG. This is done by applying a mechanical stress from the bottom to the top of the bottom surface of the (near the top end).

FIG. 5 is an enlarged perspective view of the B portion of FIG. 4, and is an enlarged perspective view of only the peripheral region including the connection electrodes 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 are opposed to each other on the front and back sides of the crystal vibrating piece and have the same size. For convenience of explanation of the application state of the conductive adhesive S, the application position of the conductive adhesive S is indicated by a dashed line (illustration of the electrode pads 6 of the container is omitted).

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

Breaking traces (fracture traces) 38, 38 of traces broken off from the bridges 35, 35 are rougher than the area where the bridges are not formed on the short side surface of the one end side 3A of the crystal vibrating piece. there is The portions other than the fracture marks 38 on the short side surfaces of the one end side 3A of the crystal vibrating piece 3 are the crystal planes of the AT-cut crystal exposed by wet etching, and the surfaces thereof are smoothed by chemical erosion. On the other hand, the fracture trace 38 is a cleaved surface where the bridge is fractured by mechanical stress. Therefore, the smoothness of the surface of the rupture mark 38 is relatively rough compared to the portion other than the rupture mark 38 on the short side surface of the one end side 3A.

As described above, a first side electrode 343 continuous with the connection electrode 341 and a connection electrode 342 A continuous first side electrode 344 is formed, and 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 this 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 of one exposed portion in plan view to the area of one connection electrode in which the exposed portion is formed in plan view. will be described with reference to. Table 1 shows the experimental results under eight conditions regarding the exposed portion. Conditions 1 to 5 are for keeping the position of the center of the exposed portion constant with respect to the connection electrode, and changing only the diameter of the exposed portion. On the other hand, Condition 6 to Condition 8 are those in which 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.

Conditions 1 to 5 specify that the pair of connection electrodes 341 and 342 be arranged at positions spaced apart by 0.05 mm outward from each inner edge in the direction of the short side of the crystal vibrating piece 3 (in the direction toward the corners of both ends of the short side). , and the centers O, O of the exposed portions 9, 9 (see FIG. 4). The distances from the inner edges of the pair of connection electrodes 341, 342 to the centers O, O of the exposed portions 9, 9 are denoted by symbol C in FIG. The diameter of the exposed portion 9, which is circular in plan view, is reduced 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 this embodiment, the connection electrodes 341 (the same applies to 342) are rectangular in plan view. The length Lt of the long side of the connection electrode 341 (342) is 0.175 mm, and the length Wt of the short side 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, under 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 a plan view (hereinafter, abbreviated as the area ratio S1/S2 of the exposed portion) is 1.9% to 17.3%.

The evaluation of the prototypes under conditions 1 to 8 was performed based on the reflow characteristics of the crystal oscillator. Specifically, a crystal oscillator is put into a reflow furnace controlled by a temperature profile that maintains a temperature of +160°C to +180°C for 120 seconds and holds a peak temperature of +220°C or higher for at least 65 seconds, and then reflows. The oscillation frequency of the crystal oscillator was measured each time it was put into the furnace. The oscillation frequency was measured after the prototype was taken out of the reflow furnace and left at room temperature for 2 hours.

The evaluation index for each condition includes the variation "ΔF/F_3σ" (3σ is three times the standard deviation σ) of the frequency deviation (ΔF/F) in each of the first, second, and third reflows, and The minimum value "ΔF/F_Min" of the frequency deviation (ΔF/F) in each of the first, second, 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 reflows. Similarly, "ΔF/F_3σ (maximum)" represents the maximum value of "ΔF/F_3σ" in each of the first to third reflows. Also, "ΔF/F_Min (minimum)" in Table 1 represents the minimum value of "ΔF/F_Min" in each of the first to third reflows. Similarly, "ΔF/F_Min (maximum)" represents the maximum value of "ΔF/F_Min" in each of the first to third reflows.

FIG. 7 is a graph showing the relationship between the area ratio S1/S2 of the exposed portion and the variation ΔF/F_3σ of the frequency deviation under conditions 1 to 5. In FIG. FIG. 8 shows a graph of the relationship between the area ratio S1/S2 of the exposed portion and the minimum value ΔF/F_Min of the frequency deviation under conditions 1 to 5. In FIG. As a reference for comparison with the present invention, FIG. 6 shows reflow resistance characteristics of a conventional crystal oscillator. In this conventional crystal oscillator, the connection electrodes of the crystal vibrating piece are not formed with an exposed portion. As shown in FIG. 6, in the conventional crystal oscillator in which the connection electrode is not formed with an exposed portion, all the data exceeds ±1 ppm, which is the pass/fail judgment criterion (standard value) for the frequency deviation ΔF/F. there is

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

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

Thus, under conditions 1 and 2, in which the diameter of the exposed portion is relatively large among 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 also small. . It is considered that this is because the larger the diameter of the exposed portion, the stronger the bonding strength of the exposed portion, and the more easily affected by the stress caused by the bonding.

In this embodiment, the acceptance/rejection criterion for the variation ΔF/F_3σ of the frequency deviation is within 0.5 ppm, and the acceptance/rejection criterion for the minimum value ΔF/F_Min of the frequency deviation is within ±1.0 ppm. Therefore, from FIGS. 7 and 8, "Condition 3 (diameter 0.04 mm) to Condition 5 (diameter 0.02 mm)" are the acceptance/rejection criteria for the variation ΔF/F_3σ of the frequency deviation and the minimum value ΔF/F_Min of the frequency deviation. and slowing down 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. "Condition 5" in which the width between the maximum and minimum values of the variation ΔF/F_3σ of the frequency deviation is the smallest and the minimum value ΔF/F_Min of the frequency deviation is the largest is preferable. The exposed portion 9 in this embodiment is formed under Condition 5. As shown in FIG.

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 doing 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 of the crystal oscillator 1 . This is for the following reasons. That is, when the opening area of one exposed portion 9 is 1.9% or less of the area in plan view of one connection electrode 341 (or 342) provided with the exposed portion, bonding by the exposed portion 9 Poor strength improvement effect. Conversely, 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 a plan view, the bonding force of the exposed portion 9 becomes too strong, resulting in stress caused by bonding. This is because it becomes susceptible to the influence of

As shown in FIG. 2, the pair of exposed portions 9, 9 which are circular in plan view are formed so that their centers O, O are aligned along one short side of the crystal vibrating piece 3. As shown in FIG. Also, the pair of exposed portions 9, 9 are arranged line-symmetrically with respect to an imaginary straight line VL passing through the centers of the two short sides of the crystal vibrating piece 3 facing each other.

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

FIG. 9 shows a graph of the relationship between the distance C (see FIG. 4) from the inner edge of the connection electrode to the center of the exposed portion under Conditions 3 and 6 to 8 in Table 1 and the frequency deviation variation ΔF/F_3σ. FIG. 10 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 and the minimum value ΔF/F_Min of the frequency deviation under Conditions 3 and 6 to 8. The length W of the short side of the crystal vibrating piece 3 in this embodiment is 0.45 mm, and the distance G between the inner edges of the pair of connection electrodes 341 and 342 in the direction of the short side of the crystal vibrating piece 3 (see FIG. 4). ) is 0.09 mm. Further, under 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 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 connection electrode to the center of the exposed portion is varied, the connection electrode As the distance C from the inner edge of the exposed portion to the center of the exposed portion increases, the variation ΔF/F_3σ of the frequency deviation tends to decrease. However, under condition 3 (C = 0.05 mm), condition 7 (C = 0.09 mm), and condition 8 (C = 0.13 mm), the decrease in frequency deviation variation ΔF/F_3σ slowed down, and the amount of change was small. A trend was observed.

On the other hand, in FIG. 10, it was observed that the minimum value ΔF/F_Min of the frequency deviation generally increased 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, under condition 3 (C=0.05 mm), condition 7 (C=0.09 mm), and condition 8 (C=0.13 mm), the increase in the minimum value ΔF/F_Min of the frequency deviation slows down, and the amount of change is A tendency to decrease was observed.

In FIG. 9, it can be judged that conditions 3 and 8 are practically acceptable levels in light of the acceptance/rejection criteria (within 0.5 ppm) of the variation ΔF/F_3σ of the frequency deviation. In addition, in FIG. 10, it can be judged that conditions 3 and 7 are at a practically acceptable level in light of the pass/fail judgment criteria (within ±1.0 ppm) of the minimum value ΔF/F_Min of the frequency deviation. Therefore, considering both the frequency deviation variation ΔF/F_3σ and the frequency deviation minimum value ΔF/F_Min, “Condition 3” is preferable among Conditions 3 and 6-8.

The ratio H/W between the distance H between the centers O, O of the pair of exposed portions 9, 9 and the short side dimension W of the crystal vibrating piece in this "Condition 3" is 42.2%. H/W is 42.2% even in the above-described "Conditions 3 to 5", which is the preferable range of the area ratio S1/S2 of the exposed portion. “H” in Conditions 3 to 5 is 0.19 mm, and considering the manufacturing error (±0.005 mm) of the short side dimension W of the crystal vibrating piece, the ratio H/W is 41.8%. ~42.7% is a preferable range.

When both ends (both corners) of one short side of the crystal vibrating piece are firmly bonded with a conductive adhesive, the oscillation frequency of the crystal oscillator tends to change due to the stress associated with bonding. On the other hand, the exposed portions 9, 9 provided one by one on each of the pair of connection electrodes 341, 342 as in the present invention extend along the imaginary straight line VL passing through the centers of the two short sides of the crystal vibrating piece 3. , and the length H of the line segment connecting the centers O of the pair of exposed portions 9, 9 is 41.8 with respect to the length W of the short side of the crystal vibrating piece 3. % or more and 42.7% or less. With such a configuration, the portion near the center of one short side of the crystal vibrating piece 3 is firmly bonded. As a result, compared to the configuration in which the exposed portions are provided near both ends of the short side of the crystal resonator element, the present invention does not firmly bond the vicinity of both ends of the short side, thereby reducing the effect of stress associated with bonding. be able to.

As shown in FIG. 2, each outer edge of the conductive adhesives S, S in the extension direction of the short side of the crystal vibrating piece 3 (vertical direction in FIG. It extends outside beyond both corners C1, C1 of the side. However, in the present invention, the outer edge of the conductive adhesive on the crystal vibrating piece in a plan view is not limited to extending outward beyond both corners of one short side of the crystal vibrating piece. That is, the outer edge of the conductive adhesive applied to the crystal vibrating piece in the present invention in a plan view may be located inside both corners C1, C1 of one short side of the crystal vibrating piece 3 . In this case, it is possible to suppress the influence of the stress transmitted from the container 2 bonded to the external substrate to the crystal vibrating piece 3 . 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 piece 3, as shown in FIG. is conductively bonded to Specifically, in the embodiment of the present invention, the crystal vibrating piece 3 is composed of the conductive adhesives S, S having fracture marks 38, 38, first side electrodes 343 (not shown in FIG. 5), 344, and slits. The inner metal films 371 (not shown in FIG. 5) and 372 are electrically connected to the electrode pads 6 and 6 . Further, the conductive adhesives S, S are in a state of reaching the substrate of the two long sides of the crystal vibrating piece 3 facing each other.

According to the above configuration, the crystal vibrating piece 3 is attached to the pair of electrode pads 6, 6 in a state in which the conductive adhesives S, S reach not only the first side electrodes 343, 344 but also the fracture marks 38, 38. Since the crystal vibrating piece 3 and the conductive adhesive S are conductively bonded to each other, the adhesion between the crystal vibrating piece 3 and the conductive adhesive S can be improved. This is because the bonding strength can be supplemented by the base material of the crystal vibrating piece 3 having excellent adhesion to the conductive adhesive S. In addition to these, the conductive adhesive S also extends to the crystal substrate on the two long sides of the crystal vibrating piece 3 facing each other, so that 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. In addition, the same code|symbol is used about the structure similar to embodiment of this invention mentioned above, and the description is omitted. The following description focuses on differences from the above-described embodiment of the present invention.

In another embodiment of the present invention, the shape of the crystal vibrating piece and the form of application of the conductive adhesive are different from the above-described embodiments of the present invention. First, as for the shape of the crystal vibrating piece, as shown in FIG. 11, inclined surfaces 11 (11a, 11b) appear on each of a set of side surfaces on the long side of the crystal vibrating piece 10 . In addition, inclined surfaces 12 (12a, 12b) also appear on each of the pair of short-side side surfaces of the crystal vibrating piece 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 one main surface of the crystal vibrating piece 10 (lower main surface in FIG. 11). It's becoming Also, the angle β formed between the inclined surface 11a and the inclined surface 11b is an obtuse angle.

On the other hand, with regard to the inclined surface 12 on the side surface of the short side of the crystal vibrating piece 10, the angle γ between the inclined surface 12a and one main surface of the crystal vibrating piece 10 (lower main surface in FIG. 11), 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 Regarding each of the inclined surfaces on the long side and 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 therewith, and the angle between the plurality of inclined surfaces Since the formed angles change depending on the etching conditions, not all of these angles are obtuse angles, and obtuse and acute angles may be mixed.

The inclined planes 11a and 11b and the inclined planes 12a and 12b are crystal planes of the AT-cut crystal that appear by wet etching. can change shape. Therefore, the appearance of the inclined surfaces 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 appearances of the inclined surfaces of the crystal vibrating piece shown in FIG. 11 or the shape of the side surfaces. .

In addition, due to its anisotropy, the AT-cut crystal has a different cross-sectional shape at both ends in the long-side direction and both ends in the short-side direction of the crystal vibrating piece, which is rectangular in plan view. In particular, as shown in FIGS. 3 to 5, when the X-axis of the AT-cut crystal is set on the long side of the crystal vibrating piece and the Z′-axis of the AT-cut crystal is set on the short side, the long side direction The difference in cross-sectional shape at both ends of is large depending on the etching conditions. AT-cut crystal has such properties, but the application of the present invention is not limited to the crystal axis direction shown in FIGS. , 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 long-side side surfaces of the crystal vibrating piece 10 . Specifically, the second side electrode 141 is adjacent to the fracture trace 16 (one of the pair of fracture traces 16, 16) and is continuous with the connection electrode 131 (131a, 131b; not shown in FIG. 11). formed by Similarly, the second side electrode 142 is adjacent to the fracture trace 16 (the other of the pair of fracture traces 16, 16) and formed continuously with the connection electrodes 132 (132a, 132b). First side electrodes 133 (not shown in FIG. 11) and 134 are formed on the inclined surfaces 12 (12a and 12b) on one short side of the crystal vibrating piece 10 .

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

Next, regarding the form of application of the conductive adhesive, as shown in FIG. , the in-slit metal film 152 (same for 151) and the second side electrode 142 (same for 141). Although the second side electrodes 141 and 142 are formed in other embodiments of the present invention, the second side electrodes 141 and 142 may not be formed. That is, electrical connection between the front and back connection electrodes 131a (132a) and 131b (132b) of the crystal vibrating piece 10 may be ensured by the first side electrode 133 (134).

According to the configuration according to another embodiment of the present invention, the crystal vibrating piece 10 is not only 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 electrodes 133, 134 and the break marks 16, 16 are also joined to the electrode pads, 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, which has excellent adhesion to the conductive adhesive S, but also to the fracture trace 16, which has a rougher surface than the exposed portion 9, so that the so-called “anchor” is applied. This is because the adhesiveness between the crystal vibrating piece 10 and the conductive adhesive S is further improved due to the "effect".

Further, according to the configuration according to another embodiment of the present invention, the crystal vibrating piece 10 is configured such that the conductive adhesive S is not only the connection electrodes 131 and 132, the first side electrodes 133 and 134, and the fracture marks 16, but also the connection electrodes. The second side electrodes 141 and 142 that are continuous with 131 and 132 are also joined to the electrode pads. That is, since the conductive adhesives S, S reach not only the connection electrodes 131, 132 including the exposed portions 9, 9 and the fracture marks 16, 16 but also the second side electrodes 141, 142, the crystal vibrating piece 10 is The conductive adhesive S is arranged so as to straddle the short side and the long side adjacent to the short side. As a result, the adhesion between the crystal vibrating piece 10 and the conductive adhesive S is further enhanced, and the bonding strength can be improved.

Furthermore, according to the configuration according to 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 explained next. A pair of long side surfaces of the crystal vibrating piece 10 includes inclined surfaces 11 , 11 . The second side 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 electrode 142 is formed to extend from the connection electrode 132 (132a, 132b) to the inclined surface 11 (11a, 11b). With such a configuration, the angles formed by the plurality of surfaces can be made gentler than in a configuration in which the side surfaces of the crystal vibrating piece are perpendicular to the main surface of the crystal vibrating piece. This can prevent disconnection of the side electrodes. The same effect can be said for the first side electrodes 133 and 134 formed on the inclined surfaces 12 and 12 of the side surfaces on one short side of the crystal vibrating piece 10 .

In the above-described embodiments and other embodiments of the present invention, the crystal vibrating piece is conductively joined to the electrode pads on the upper surface of the projection in a cantilevered state. A portion may be formed so as to be electrically conductively joined in a state of being supported on both sides.

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

Further, regarding bonding of the crystal vibrating piece according to the present invention to the electrode pads via the conductive adhesive, even if the crystal vibrating piece having the configuration shown in FIGS. good.

Also, in the above-described embodiments and other embodiments of the present invention, the conductive adhesive was applied only once to the upper surfaces of the pair of electrode pads (so-called "priming"), but such a primed conductive adhesive A conductive adhesive may be overcoated on top of the conductive adhesive (so-called “topcoat”).

In the above-described embodiments and other embodiments of the present invention, examples were given of crystal oscillators having a structure in which the cross-sectional shape of the container is the letter "H", but the present invention is applicable to crystal oscillators having such a structure. However, the present invention can also be applied to a crystal oscillator in which an electronic component element and a crystal vibrating piece are accommodated inside a concave portion that is open only at the top, and a lid is bonded to the open end of the concave portion.

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

The invention can be embodied in many other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiments are merely examples in every respect and should not be construed in a restrictive manner. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Furthermore, all modifications and changes within the equivalent scope of 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 Portion 16, 38 Fracture 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 crystal vibrating piece that is approximately rectangular in plan view is cantilever bonded to an electrode pad provided inside a container via a conductive adhesive, and is airtightly sealed by bonding a lid to the container. a device,
The crystal vibration device has a substantially rectangular shape in a plan view, and has outer dimensions of 1.6 mm in the vertical direction and 1.2 mm in the horizontal direction, and the conductive adhesive is made of a silicone-based resin adhesive,
The crystal vibrating piece is a flat plate having a rectangular shape in plan view, and the length of the short side is 0.45 mm,
A pair of connection electrodes to be connected to the outside are provided separately from each other on both ends of at least one short side of the front and back main surfaces of the crystal vibrating piece,
The connection electrode has a film structure in which an upper layer is laminated on a base layer, the upper layer is gold,
In each region of the pair of connection electrodes, an exposed portion where the base of the crystal vibrating piece is exposed is provided,
A crystal oscillation device, wherein, 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 a plan view. A pair of first side electrodes continuous with each of the pair of connection electrodes are formed on the side surface of one short side of the crystal vibrating piece on which the pair of connection electrodes are formed, and a fracture trace of the crystal vibrating piece. is exposed and
The crystal vibrating piece is joined to the electrode pads in a state in which the conductive adhesive reaches at least the pair of connection electrodes, the pair of first side electrodes, and the fracture marks so as to cover the exposed portions. 2. The crystal oscillation device according to claim 1, wherein:

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