PIEZOELECTRIC VIBRATING PIECE AND PIEZOELECTRIC DEVICE

A piezoelectric vibrating piece includes a vibrator, a framing portion, a connecting portion, and an extraction electrode. The vibrator includes excitation electrodes formed on both principal surfaces. The framing portion includes an inner peripheral side facing the vibrator and an outer peripheral side on an opposite side of the inner peripheral side. The framing portion has a predetermined width from the inner peripheral side to the outer peripheral side. The connecting portion connects the vibrator and the framing portion. The extraction electrode is extracted from the excitation electrode to the framing portion via the connecting portion. The extraction electrode contacts the inner peripheral side and the outer peripheral side of the framing portion. The extraction electrode includes an end side that connects the inner peripheral side and the outer peripheral side of the extraction electrode. All of the end side is longer than the predetermined width.

DETAILED DESCRIPTION

The preferred embodiments of this disclosure will be described with reference to the attached drawings. It will be understood that the scope of the disclosure is not limited to the described embodiments, unless otherwise stated.

Constitution Of A Piezoelectric Device100According To A First Embodiment

FIG. 1is an exploded perspective view of the piezoelectric device100. The piezoelectric device100includes a lid plate110, a base plate120, and a piezoelectric vibrating piece130. For example, an AT-cut quartz-crystal vibrating piece is used for the piezoelectric vibrating piece130, the lid plate110, and the base plate120. The AT-cut quartz-crystal vibrating piece has a principal surface (in the Y-Z plane) that is tilted by 35° 15′ about the Y-axis of crystallographic axes (XYZ) in the direction from the Z-axis to the Y-axis around the X-axis. In the following description, the new axes tilted with reference to the axis directions of the AT-cut quartz-crystal vibrating piece are denoted as the Y′-axis and the Z′-axis. This disclosure defines the long side direction of the piezoelectric device100as the X-axis direction, the height direction of the piezoelectric device100as the Y′-axis direction, and the direction perpendicular to the X and Y′-axis directions as the Z′-axis direction.

The piezoelectric vibrating piece130includes a vibrator131vibrating at a predetermined vibration frequency, a framing portion132surrounding the vibrator131, and a connecting portion133connecting the vibrator131and the framing portion132. An excitation electrode134aand an excitation electrode134bare formed on the surface at the +Y′-axis side and on the surface at the −Y′-axis side of the vibrator131, respectively. An extraction electrode135aand an extraction electrode135bare respectively extracted from the excitation electrode134aand the excitation electrode134bto the −X-axis side at the +Z′-axis side and the +X-axis side at the −Z′-axis side on the surface at the −Y′-axis side of the framing portion132via the connecting portion133. A through groove136is formed between the vibrator131and the framing portion132. The through groove136passes through the piezoelectric vibrating piece130in the Y′-axis direction.

The base plate120includes a depressed portion121depressed at the −Y′-axis side, a bonding surface122, and connecting electrodes123on the surface at the +Y′-axis side. The bonding surface122surrounds the depressed portion121. The connecting electrodes123are disposed at the corner of the +X-axis side and the −Z′-axis side and at the corner of the −X-axis side and the +Z′-axis side of the bonding surface122. The bonding surface122is to be bonded on the surface at the −Y′-axis side of the framing portion132of the piezoelectric vibrating piece130via a bonding material140(seeFIG. 2A). Additionally, a pair of mounting terminals124is formed on the surface at the −Y′-axis side of the base plate120. Furthermore, castellations126are formed at four corners of the side surfaces of the base plate120. Castellation electrodes125are formed at the side surface at the +X-axis side at the −Z′-axis side and the side surface at the −X-axis side at the +Z′-axis side of the castellations126. The castellation electrode125electrically connects the connecting electrode123and the mounting terminal124. The connecting electrode123, which is formed at the corner at the −X-axis side and the +Z′-axis side, electrically connects to the extraction electrode135aextracted to the corner at the −X-axis side and the +Z′-axis side on the surface at the −Y′-axis side of the piezoelectric vibrating piece130. The connecting electrode123, which is formed at the corner at the +X-axis side and the −Z′-axis side, electrically connects to the extraction electrode135bextracted to the corner at the +X-axis side and the −Z′-axis side on the surface at the −Y′-axis side of the piezoelectric vibrating piece130.

The lid plate110includes a depressed portion111and a bonding surface112on the surface at the −Y′-axis side. The bonding surface112surrounds the depressed portion111. The bonding surface112is to be bonded on the surface at the +Y′-axis side of the framing portion132of the piezoelectric vibrating piece130via the bonding material140(seeFIG. 2A).

FIG. 2Ais a cross-sectional view taken along the line A-A ofFIG. 1. The piezoelectric device100includes the lid plate110at the +Y′-axis side and the base plate120at the −Y′-axis side of the piezoelectric vibrating piece130. The piezoelectric device100includes a cavity141formed by the depressed portion111of the lid plate110and the depressed portion121of the base plate120. The vibrator131of the piezoelectric vibrating piece130is disposed in the cavity141. The cavity141is sealed by forming the non-conductive bonding materials140between the bonding surface112of the lid plate110and the surface at the +Y′-axis side of the framing portion132, and between the bonding surface122of the base plate120and the surface at the −Y′-axis side of the framing portion132. The extraction electrode135aand the extraction electrode135b,which are formed at the framing portion132, electrically connect to the connecting electrode123formed at the base plate120. This electrically connects the excitation electrode134aand the excitation electrode134bto a pair of mounting terminals124.

FIG. 2Bis an enlarged view of a dotted line161ofFIG. 2A. Each electrode formed in the piezoelectric vibrating piece130and at the base plate120includes a first metal layer151aand a second metal layer151b.The first metal layer151ais formed on the surface of a quartz-crystal material constituting the piezoelectric vibrating piece130and the base plate120. The second metal layer151bis formed on the surface of the first metal layer151a.The first metal layer151ahas a role in good adhesion for each electrode to the quartz-crystal material constituting the piezoelectric vibrating piece130or similar member. The second metal layer151bhas a role in protection for each electrode. The first metal layer151a,which is formed in the piezoelectric device100, for example, is made of a chromium (Cr) layer152aand a nickel tungsten (NiW) layer152b.The chromium (Cr) layer152ais formed on the surface of the quartz-crystal material. The nickel tungsten (NiW) layer152bis formed on the surface of the chromium (Cr) layer152a.Chromium (Cr) provides good adhesion to the quartz-crystal material. Hence, each electrode and the quartz-crystal material are strongly adhered together. This allows each electrode to be fixed to the quartz-crystal material. Additionally, nickel tungsten (NiW) prevents the weakness of the bonding between the quartz-crystal material and the chromium (Cr) layer152awhere chromium (Cr) diffuses into the second metal layer151b.The second metal layer151b,for example, can be made of gold (Au). Gold (Au) is chemically stable such that gold (Au) is capable of protecting each electrode from corrosion or similar problem. As illustrated inFIG. 2B, the extraction electrode135aand the extraction electrode135bformed in the piezoelectric vibrating piece130are formed as follows. The first metal layer151aand the second metal layer151bof the extraction electrode135aand the extraction electrode135bcontacting an outer peripheral side132b(seeFIG. 3A) of the framing portion132in the piezoelectric vibrating piece130are formed so as to contact the external environment of the piezoelectric device100.

FIG. 3Ais a plan view of the piezoelectric vibrating piece130. The vibrator131of the piezoelectric vibrating piece130has a rectangular shape with a long side parallel to the X-axis and a short side parallel to the Z′-axis. The framing portion132includes an inner peripheral side132afacing the vibrator131and the outer peripheral side132bon the opposite side of the inner peripheral side132a. The connecting portion133connects a center of the side at the −X-axis side of the vibrator131and the center of the inner peripheral side132aat the −X-axis side of the framing portion132. In the case where the piezoelectric vibrating piece130is formed as a part of the piezoelectric device100, the outer peripheral side132bcontacts the external environment of the piezoelectric device100. The extraction electrode135apasses across the connecting portion133and is extracted from the excitation electrode134ato the −X-axis side and the +Z′-axis side on the surface at the +Y′-axis side of the framing portion132. The excitation electrode134ais formed on the surface at the +Y′-axis side of the vibrator131. The extraction electrode135ais extracted to the surface at the −Y′-axis side via a side surface136aat the −X-axis side and the +Z′-axis side of the through groove136. The side surface136aof the through groove136where the extraction electrode135ais formed mainly includes the +Z′-axis side of the side at the −X-axis side of the vibrator131, the +Z′-axis side of the connecting portion133, and the −X-axis side and the +Z′-axis side of the inner peripheral side132aof the framing portion132.

Assume that the width in the Z′-axis direction of the framing portion132extending in the X-axis direction is a width W1. The framing portion132extending in the X-axis direction is disposed at the +Z′-axis side and the −Z′-axis side of the vibrator131. Assume that the width in the X-axis direction of the framing portion132extending in the Z′-axis direction is a width W2. The framing portion132extending in the Z′-axis direction is disposed at the +X-axis side and the −X-axis side of the vibrator131. In the piezoelectric vibrating piece130, the sizes of the width W1 and the width W2 are equally formed. The extraction electrode135ais formed across the full width of the framing portion132. The extraction electrode135ais formed on the surface at the +Y′-axis side of the framing portion132. Hence, the extraction electrode135a,which is formed on the surface at the +Y′-axis side of the framing portion132, includes a side contacting the inner peripheral side132aof the framing portion132, a side contacting the outer peripheral side132bof the framing portion132, and an end side138. The end side138does not contact the inner peripheral side132aand the outer peripheral side132band connects the inner peripheral side132aand the outer peripheral side132b. The extraction electrode135ais formed on the surface at the +Y′-axis side of the framing portion132. Each end side138of the extraction electrode135ais formed in an L shape to include a straight line extending in the X-axis direction and a straight line extending in the Z′-axis direction. Hence, the length of each end side138is formed longer compared with the width W1 and the width W2 of the framing portion132.

FIG. 3Bis a cross-sectional view of the piezoelectric vibrating piece130on the surface at the −Y′-axis side viewed from the +Y′-axis side. The excitation electrode134bis formed on the surface at the −Y′-axis side of the vibrator131. The extraction electrode135bextends in the −X-axis direction and is extracted from the excitation electrode134bto the +X-axis side and the −Z′-axis side on the surface at the −Y′-axis side of the framing portion132via the connecting portion133. The extraction electrode135ais extracted from the surface at the +Y′-axis side to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode135ais further extracted to the corner at the −X-axis side and the +Z′-axis side of the framing portion132on the surface at the −Y′-axis side of the piezoelectric vibrating piece130. The extraction electrode135aand the extraction electrode135bare formed at the −Y′-axis side of the framing portion132. The extraction electrode135aand the extraction electrode135bare formed across the full width of the framing portion132, similarly to the extraction electrode135aformed on the surface at the +Y′-axis side of the framing portion132. All of the end sides138are formed in an L shape.

As illustrated inFIG. 3AandFIG. 3B, in the piezoelectric vibrating piece130, the extraction electrode135aand the extraction electrode135bformed at the framing portion132are formed across the full widths of the width W1 and the width W2 of the framing portion132. Hence, in the piezoelectric vibrating piece130, the increase of electrical resistance caused by the extraction electrode135aand the extraction electrode135bis suppressed. The increase of a crystal impedance (CI) value of the piezoelectric vibrating piece130is suppressed.

FIG. 4is a plan view of a piezoelectric wafer W130. The method for forming the piezoelectric vibrating piece130will be described with reference toFIG. 4. A piezoelectric vibrating piece forms a large number of piezoelectric vibrating pieces on a piezoelectric wafer made of a piezoelectric material. This allows forming simultaneously a large number of piezoelectric vibrating pieces.FIG. 4illustrates the piezoelectric wafer W130where the plurality of piezoelectric vibrating pieces130is formed. The outline of the piezoelectric vibrating piece130is formed by etching the piezoelectric wafer W130. Furthermore, the excitation electrode134a,the excitation electrode134b,the extraction electrode135a,and the extraction electrode135bare formed by sputtering chromium (Cr), nickel tungsten (NiW), and gold (Au).

The piezoelectric wafer W130illustrated inFIG. 4includes the plurality of piezoelectric vibrating pieces130aligned in the X-axis direction and the Z′-axis direction. Additionally,FIG. 4illustrates a scribe line171between each of the piezoelectric vibrating pieces130neighboring each other. The piezoelectric wafer W130is diced along the scribe line171. Thus, the piezoelectric vibrating pieces130are divided individually. The extraction electrode135aand the extraction electrode135bformed in the piezoelectric vibrating piece130are formed so as to overlap in this scribe line171. This allows forming the extraction electrode135aand the extraction electrode135bacross the full width of the framing portion132. The outer peripheral side132bof the framing portion132is formed by a trace diced by the scribe line171. Hence, as illustrated inFIG. 2B, the first metal layer151aand the second metal layer151bof the extraction electrode135aand the extraction electrode135bare formed so as to contact the external environment of the piezoelectric device100.

A piezoelectric device should be formed so that there is no characteristic deterioration. Hence, characteristic deterioration of the piezoelectric device is examined by performing a moisture resistance test, a salt spray test, or similar test. An electrode contacting this poor external environment corrodes and erodes. Especially, since the first metal layer151aforming an electrode is susceptible to corrosion or similar, the first metal layer151aexposed at the outer peripheral side132bmay pass along the end side138and reach the inner peripheral side132aof the extraction electrodes135aand135b.Therefore, when corrosion of the electrode reaches the inner peripheral side132afrom the outer peripheral side132b,sealing of the cavity141of the piezoelectric device100is dissolved.

The end side138of the piezoelectric vibrating piece130is formed in an L shape by the plurality of straight lines. Therefore, the length of the end side138is formed longer compared with the width W1 and the width W2 of the framing portion132. Hence, although the first metal layer151acontacting the external environment corrodes and erodes, the erosion hardly reaches the inner peripheral side132afrom the outer peripheral side132bof the framing portion132. This prevents the sealing of the cavity141of the piezoelectric device100from being dissolved.

Second Embodiment

The end side of the extraction electrode can be formed in various shapes. A description will be given of the modifications of the piezoelectric vibrating piece where the end side is formed in various shapes. Like reference numerals designate corresponding or identical elements throughout the first embodiment and the second embodiment, and therefore such elements will not be further elaborated here.

Constitution Of A Piezoelectric Vibrating Piece230

FIG. 5Ais a plan view of a piezoelectric vibrating piece230. The piezoelectric vibrating piece230includes the vibrator131, the framing portion132, and the connecting portion133. The excitation electrode134ais formed on the surface at the +Y′-axis side of the vibrator131. An extraction electrode235ais extracted from the excitation electrode134a.The extraction electrode235aextends in the −X-axis direction from the excitation electrode134a.The extraction electrode235apasses across the connecting portion133and is extracted to the −X-axis side and the +Z′-axis side of the framing portion132. The extraction electrode235ais extracted to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode235ais formed across the full width of the framing portion132. Hence, an end side238is formed in the extraction electrode235a.The end side238is formed with a fan-shape curved line expanding to the outside of the extraction electrode235a.

FIG. 5Bis a plan view of the piezoelectric vibrating piece230on the surface at the −Y′-axis side viewed from the surface at the +Y′-axis side. The excitation electrode134bis formed on the surface at the −Y′-axis side of the vibrator131. An extraction electrode235bis formed from the excitation electrode134bto the corner at the +X-axis side and the −Z′-axis side of the framing portion132via the connecting portion133. The extraction electrode235ais extracted from the surface at the +Y′-axis side to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode235ais formed to the corner at the −X-axis side and the +Z′-axis side of the framing portion132. The extraction electrode235aand the extraction electrode235b,which are formed on the surface at the −Y′-axis side of the framing portion132, are formed across the full width of the framing portion132and include the end side238.

All of the end sides238formed in the piezoelectric vibrating piece230are formed with a fan-shape curved line expanding to the outside of the extraction electrode235aor the extraction electrode235b.Therefore, the length of the end side238is formed longer compared with the width W1 and the width W2 of the framing portion132. Hence, even if the first metal layer151aexposed to the outer peripheral side132bcorrodes, the erosion hardly reaches within the cavity141. This prevents the sealing of the cavity141of the piezoelectric device100from being dissolved. In the piezoelectric vibrating piece230, the end sides238adjacent to the connecting portion133are formed with a fan-shape curved line expanding to the outsides of the extraction electrodes235aand235b.Accordingly, this configuration is preferred because the width of the extraction electrodes235aand235bnear the connecting portion133are not significantly narrowed.

Constitution Of A Piezoelectric Vibrating Piece330

FIG. 6Ais a plan view of a piezoelectric vibrating piece330. The piezoelectric vibrating piece330includes the vibrator131, the framing portion132, and the connecting portion133. The excitation electrode134ais formed on the surface at the +Y′-axis side of the vibrator131. An extraction electrode335ais extracted from the excitation electrode134a.The extraction electrode335aextends in the −X-axis direction from the excitation electrode134a.The extraction electrode335apasses across the connecting portion133and is extracted to the −X-axis side and the +Z′-axis side of the framing portion132. The extraction electrode335ais extracted to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode335ais formed across the full width of the framing portion132. Hence, an end side338is formed in the extraction electrode335a.The end side338is formed to include a straight line that is not parallel to the X-axis and the Z′-axis. That is, the straight line has an angle with respect to the X-axis and the Z′-axis.

FIG. 6Bis a plan view of the piezoelectric vibrating piece330on the surface at the −Y′-axis side viewed from the surface at the +Y′-axis side. The excitation electrode134bis formed on the surface at the −Y′-axis side of the vibrator131. An extraction electrode335bis formed from the excitation electrode134bto the corner at the +X-axis side and the −Z′-axis side of the framing portion132via the connecting portion133. The extraction electrode335ais extracted from the surface at the +Y′-axis side to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode335ais formed to the corner at the −X-axis side and the +Z′-axis side of the framing portion132. The end side338is formed in the extraction electrode335aand the extraction electrode335b,which are formed on the surface at the −Y′-axis side of the framing portion132.

In the piezoelectric vibrating piece330, the end side338is formed to include the straight line that is not parallel to the X-axis and the Z′-axis. Therefore, the length of the end side338is formed longer compared with the width WI and the width W2 of the framing portion132. Hence, even if the first metal layer151aexposed to the outer peripheral side132bcorrodes, the erosion hardly reaches within the cavity141. This prevents the sealing of the cavity141of the piezoelectric device100from being dissolved.

Constitution Of A Piezoelectric Vibrating Piece430

FIG. 7Ais a plan view of a piezoelectric vibrating piece430. The piezoelectric vibrating piece430includes the vibrator131, the framing portion132, and the connecting portion133. The excitation electrode134ais formed on the surface at the +Y′-axis side of the vibrator131. An extraction electrode435ais extracted from the excitation electrode134a.The extraction electrode435aextends in the −X-axis direction from the excitation electrode134a.The extraction electrode435apasses across the connecting portion133and is extracted to the −X-axis side and the +Z′-axis side of the framing portion132. The extraction electrode435ais extracted on the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode435ais formed across the full width of the framing portion132. Hence, an end side438is formed in the extraction electrode435a.The end side438is formed in a comb shape where a plurality of straight lines is connected. In the extraction electrode435a,the end side438is not formed in a comb shape adjacent to the inner peripheral side132aclose to the connecting portion133.

FIG. 7Bis a plan view of the piezoelectric vibrating piece430on the surface at the −Y′-axis side viewed from the surface at the +Y′-axis side. The excitation electrode134bis formed on the surface at the −Y′-axis side of the vibrator131. An extraction electrode435bis formed from the excitation electrode134bto the corner at the +X-axis side and the −Z′-axis side on the surface at the −Y′-axis side of the framing portion132via the connecting portion133. The extraction electrode435ais extracted from the surface at the +Y′-axis side to the surface at the −Y′-axis side via the side surface136aof the through groove136. The extraction electrode435ais formed to the corner at the −X-axis side and the +Z′-axis side of the framing portion132. The end side438is formed in the extraction electrode435aand the extraction electrode435bformed on the surface at the −Y′-axis side of the framing portion132. In the extraction electrode435aand the extraction electrode435b,the end side438is not formed in a comb shape adjacent to the inner peripheral side132aclose to the connecting portion133.

In the piezoelectric vibrating piece430, the end side438is formed in a comb shape. Therefore, the length of the end side438is formed longer compared with the width W1 and the width W2 of the framing portion132. Hence, even if the first metal layer151aexposed to the outer peripheral side132bcorrodes, the erosion hardly reaches within the cavity141. This prevents the sealing of the cavity141of the piezoelectric device100from being dissolved. The end side438is not formed in a comb shape adjacent to the inner peripheral side132aclose to the connecting portion133. Accordingly, the widths of the extraction electrode435aand the extraction electrode435bare substantially decreased. This prevents a large increase in the electrical resistances of the extraction electrode435aand the extraction electrode435b.

Representative embodiments are described in detail above; however, as will be evident to those skilled in the relevant art, this disclosure may be changed or modified in various ways within its technical scope.

For example, the first metal layer151aincludes the chromium (Cr) layer152aand the nickel tungsten (NiW) layer152b.However, the first metal layer151amay be made of the chromium (Cr) layer152aalone. The first metal layer151amay be made as the chromium (Cr) layer152aand a nickel (Ni) layer by using the nickel (Ni) layer instead of the nickel tungsten (NiW) layer152b.At this time, for example, the extraction electrode135aincludes the first metal layer151aand the second metal layer151b.The first metal layer151ais made of the chromium (Cr) layer152aand the nickel (Ni) layer, which is formed on the surface of the chromium (Cr) layer152a.The second metal layer151bis formed as a gold (Au) layer on the surface of the nickel (Ni) layer.

The above-described embodiments disclose a case where the piezoelectric vibrating piece is an AT-cut quartz-crystal vibrating piece. A BT-cut quartz-crystal vibrating piece or similar member that similarly vibrates in the thickness-shear mode is similarly applicable. Further, the piezoelectric vibrating piece is basically applicable to a piezoelectric material that includes not only a quartz-crystal material but also lithium tantalate, lithium niobate, and piezoelectric ceramics.

A piezoelectric vibrating piece according to a first aspect includes a vibrator, a framing portion, a connecting portion, and an extraction electrode. The vibrator has a rectangular shape with a short side and a long side. The vibrator includes excitation electrodes formed on both principal surfaces. The vibrator vibrates at a predetermined vibration frequency. The framing portion surrounds the vibrator. The framing portion includes an inner peripheral side facing the vibrator and an outer peripheral side on an opposite side of the inner peripheral side. The framing portion has a predetermined width which intersects perpendicularly from the inner peripheral side to the outer peripheral side. The connecting portion connects the vibrator and the framing portion. The extraction electrode extracted from the excitation electrode to the framing portion via the connecting portion. The extraction electrode contacts the inner peripheral side and the outer peripheral side of the framing portion. The extraction electrode includes an end side that connects the inner peripheral side and the outer peripheral side of the extraction electrode. All of the end side is longer than the predetermined width.

In the first aspect of the disclosure, the piezoelectric vibrating piece according to a second aspect is configured as follows. The end side includes at least one of a plurality of straight lines, a curved line, and a straight line having an angle with respect to the long side and the short side.

In the second aspect of the disclosure, the piezoelectric vibrating piece according to a third aspect is configured as follows. The end side is formed in an L shape, a fan shape, a comb shape, or a shape in combination of the L shape, the fan shape, and the comb shape shapes.

In the first aspect to the third aspect of the disclosure, the piezoelectric vibrating piece according to a fourth aspect is configured as follows. The extraction electrode includes a first metal layer and a second metal layer formed on a surface of the first metal layer. The first metal layer is made of chromium (Cr), chromium (Cr) and nickel (Ni), or chromium (Cr) and nickel tungsten (NiW).

A piezoelectric device according to a fifth aspect includes the piezoelectric vibrating piece, a base plate, a lid plate, and a non-conductive bonding material.

The piezoelectric vibrating piece is according to the first aspect to the fourth aspect. The base plate is bonded on one principal surface of the framing portion. The lid plate is bonded on another principal surface of the framing portion to seal the vibrator. The non-conductive bonding material bonds the piezoelectric vibrating piece and the base plate and bonds the piezoelectric vibrating piece and the lid plate. The end side contacts the bonding material as viewed from the outer peripheral side.

With the piezoelectric vibrating piece and the piezoelectric device according to the embodiments, a leakage in a cavity can be reduced.