Elastic wave device

Abstract

To improve the heat dissipation of an elastic wave device 1 rationally.SOLUTION: A device chip 3 includes a transmission side external connection terminal 9a near one corner 3fa thereof. A package substrate 2 includes a heat dissipation wire 2g connected to the transmission side external connection terminal 9a through a bump 10. At any position in a direction going around a center 3c of the device chip 3, there is a space S between an outer edge 3d of the device chip 3 and an outer edge 2e of the package substrate 2. The space S is wide at a first side 3ga forming the corner 3fa of the device chip 3 near the transmission side external connection terminal 9a and at a second side 3gb orthogonal to the first side, and is narrow at a third side 3gc opposite to the first side 3ga and at a fourth side 3gd opposite to the second side 3gb.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an improvement in an acoustic wave device suitable for use as a duplexer in a mobile communication device or the like. [Background technology]

[0002] An acoustic wave device 100 used as a duplexer in a mobile communication device or the like has a structure shown in FIGS. In this acoustic wave device, a rectangular plate-shaped device chip 103 is mounted on a rectangular plate-shaped package substrate 101 via bumps 102, and a gap between the package substrate 101 and the device chip 103 formed by the bumps 102 is hermetically sealed with a resin sealing part 104 to form an internal space 105. On one surface of the device chip 103 located on the internal space 105 side, a circuit 106 including a plurality of IDT electrodes 106a is formed of a metal film, and external connection terminals 107 for connecting the circuit 106 to the package substrate 101 side are formed.

[0003] In this type of acoustic wave device 100, a large amount of heat is likely to be generated near the transmitting external connection terminal (Tx) among the external connection terminals 107, for example, the external connection terminal 107a in the upper left corner in Fig. 7. Such heat can cause damage to the IDT electrodes, so it is necessary to effectively release the heat to the outside. The heat spreads concentrically around the transmitting side external connection terminal 107a and is transmitted to the sealing portion 104 and package substrate 100. If the transmitting side external connection terminal 107a is provided near one corner 108 on the one surface of the device chip 103, a wide heat transmission area can be secured on the central side of the device chip 103, but the heat transmission area becomes narrow on the opposite side. Summary of the Invention [Problem to be solved by the invention]

[0004] A main problem to be solved by the present invention is to provide a new structure for rationally improving the heat dissipation of this type of acoustic wave device. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides an acoustic wave device comprising: a package substrate having a rectangular plate shape; a device chip having a rectangular plate shape smaller in area than the package substrate and mounted on the package substrate with a functional surface thereof facing the package substrate and having a functional element including an IDT electrode on one surface of the package substrate; a sealing portion formed on the one surface side of the package substrate to form an internal space between the functional surface of the device chip and the one surface of the package substrate, the device chip has a transmitting side external connection terminal on the functional surface in the vicinity of one of four corners of the functional surface, the package substrate has heat dissipation wiring connected to the transmission-side external connection terminal via a bump, a gap is formed between an outer edge of the device chip and an outer edge of the package substrate at any position in a direction around the center of the device chip; The device chip is positioned on the package substrate with the center of the package substrate not coinciding with the center of the device chip so that the gap is wider on the sides of a first side and a second side perpendicular to the first side of the device chip that constitute the corner near the transmitting side external connection terminal of the device chip, and narrower on the sides of a third side opposite the first side and a fourth side opposite the second side.

[0006] In one aspect of the present invention, the heat dissipation wiring has a first portion connected to the transmitting side external connection terminal under the device chip, and a second portion positioned within the gap, and is configured to contact the sealing portion at the second portion.

[0007] In one aspect of the present invention, the device chip is a duplexer having a transmitting filter and a receiving filter as the functional elements, and the transmitting external connection terminal is connected to the transmitting filter. Effect of the Invention

[0008] According to the acoustic wave device of the present invention, by positioning the device chip on the package substrate without the center of the package substrate and the center of the device chip being aligned, the heat transfer area generated near the transmitting side external connection terminal formed in the vicinity of one corner of the device chip can be secured widely in the entire circumferential direction around this transmitting side external connection terminal, and the heat can be effectively dissipated to the outside. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of an acoustic wave device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the acoustic wave device, and the sealing portion is omitted. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB in FIG. [Diagram 5] FIG. 5 is a configuration diagram showing an example of a circuit formed on a device chip constituting the acoustic wave device. [Figure 6] FIG. 6 is a configuration diagram showing an example of a resonator formed in a device chip constituting the acoustic wave device. [Figure 7] FIG. 7 is a plan view showing an example of a conventional acoustic wave device. [Figure 8] FIG. 8 is a cross-sectional view taken along line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present invention will be described with reference to Figures 1 to 6. An acoustic wave device 1 according to this embodiment is suitable for use as a duplexer in a mobile communication device or the like.

[0011] Such an acoustic wave device 1 includes a device chip 3 mounted on one surface 2a of a package substrate 2, with a functional surface 3a on which a functional element 7 including an IDT electrode 7b, typically a resonator 7a, facing the package substrate 2.

[0012] Typically, the device chip 3 is configured to have a rectangular plate shape with a side of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm. The package substrate 2 is configured to have a rectangular plate shape with a side of 0.7 to 3 mm and a thickness of 0.15 to 0.2 mm. The acoustic wave device 1 has a thickness of about 0.4 to 0.6 mm.

[0013] Its cross-sectional structure is shown in Figures 3 and 4. In the figures, reference numeral 3 denotes a device chip, reference numeral 3a denotes its functional surface, reference numeral 3b denotes a non-functional surface opposite to the functional surface 3a, reference numeral 7 denotes a functional element, and reference numeral 9 denotes an external output terminal which is the end of wiring 8 (see Figure 5) formed on the functional surface 3a. Between the device chip 3 and the package substrate 2, there is interposed a bump 10 (protruding electrode) that electrically connects the external output terminal 9 and the wiring 2c formed on the package substrate 2 side, and a gap 5 equivalent to the height of this bump 10 is formed. On the other surface 2b of the package substrate 2 opposite to the surface 2a on which the device chip 3 is mounted, external connection terminals 2d are formed for connecting the acoustic wave device 1 to a module substrate (not shown) or the like.

[0014] In the illustrated example, the package substrate 2 has a flat hexahedral shape in which the surface 2a and the opposing surface 2b are both rectangular when viewed from a direction perpendicular to the surface 2a. In addition, when the device chip 3 is viewed in a direction perpendicular to its functional surface 3a, both the functional surface 3a and the opposing non-functional surface 3b form a flat hexahedron with a rectangular shape whose area is smaller than that of one surface 2a and the other surface 2b of the package substrate 2. The device chip 3 is mounted on the package substrate 2 such that a gap S is formed between the outer edge 3d of the device chip 3 (where the functional surface 3a of the device chip 3 and the side surface 3e forming the thickness thereof come into contact) and the outer edge 2e of the package substrate 2 (where one surface 2a of the package substrate 2 and the side surface forming the thickness thereof come into contact) at any position in the direction circumferentially around the center 3c of the device chip 3 (see FIG. 2).

[0015] In this manner, after the device chip 3 is mounted on the surface 2a of the package substrate 2, a sealing portion 4 is formed on the surface 2a of the package substrate 2. The sealing portion 4 is typically made of an insulating synthetic resin. The sealing portion 4 has a horizontal portion 4a covering the non-functional surface 3b of the device chip 3 facing the functional surface 3a of the device chip 3, and a vertical portion 4b that follows the horizontal portion 4a, covers the side surface 3e which is the thickness of the device chip 3 between the functional surface 3a and the non-functional surface 3b, and reaches the one surface 2a of the package substrate 2, thereby forming an internal space 6 (hollow structure or air cavity) between the functional surface 3a of the device chip 3 and the one surface 2a of the package substrate 2. The vertical portion 4a of the sealing portion 4 hermetically seals the gap 5 around the entire circumference of the device chip 3, thereby forming the internal space 6 between the functional surface 3a of the device chip 3 and one surface 2a of the package substrate 2. In the illustrated example, the sealing portion 4 thus formed gives the acoustic wave device 1 a hexahedral appearance.

[0016] The device chip 3 is provided with a functional element 7 including an IDT electrode 7b, a resonator 7a in the illustrated example, on the portion of the functional surface 3a facing the internal space 6.

[0017] The device chip 3 has a function of propagating elastic waves. A piezoelectric material such as lithium tantalate or lithium niobate is typically used for the device chip 3. The device chip 3 may also be configured by laminating the piezoelectric material on a support such as sapphire, silicon, alumina, spinel, quartz, or glass.

[0018] 5 shows the concept of an example of a circuit 11 provided on one device chip 3. Reference numeral 11a denotes a transmitting filter, reference numeral 11b denotes a receiving filter, reference numeral 9 denotes an external connection terminal, reference numeral 9a denotes a transmitting external connection terminal connected to the transmitting filter 11a in the external connection terminal 9, reference numeral 7aa denotes a resonator 7a connected in series between the external connection terminals 9, reference numeral 7ab denotes a resonator 7a connected in parallel between the external connection terminals 9, reference numeral 12 denotes a ground, and reference numeral 8 denotes a wiring. The number and arrangement of the resonators 7a may be changed as necessary.

[0019] 6 shows an example of a resonator 7a constituting a duplexer. The resonator 7a has an IDT electrode 7b and a reflector 7c formed to sandwich the IDT electrode 7b. The IDT electrode 7b is composed of an electrode pair, and each electrode pair is formed by connecting a plurality of electrode fingers 7d arranged in parallel so that their length direction crosses the propagation direction x of the elastic wave with one end side of the electrode fingers by a bus bar 7e. The reflector 7c is formed by connecting ends of a plurality of electrode fingers 7f arranged in parallel so that their length direction crosses the propagation direction x of the elastic wave with a bus bar 7g. Such a resonator 7a is typically made of a conductive metal film formed by photolithography.

[0020] The device chip 3 has a transmission side external connection terminal 9a on its functional surface 3a in the vicinity of one corner 3fa out of four corners 3f on the functional surface 3a. In the illustrated example, a transmission side external connection terminal 9a is formed in the vicinity of a corner 3fa located in the upper left corner of the device chip 3 in FIG.

[0021] On the other hand, the package substrate 2 has heat dissipation wiring 2g connected to the transmission side external connection terminal 9a via a bump 10.

[0022] In addition, the device chip 3 and the package substrate 2 are combined so that at any position in the direction circumferentially around the center 3c of the device chip 3, there is a distance between the outer edge 3d of the device chip 3 and the outer edge 2e of the package substrate 2, forming a gap S. At the same time, the device chip 3 is positioned on the package substrate 2 with the center 2h of the package substrate 2 and the center 3c of the device chip 3 not coinciding so that the gap S is wider on the sides of the first side 3ga and the second side 3gb perpendicular to the first side 3ga, which constitute the corner 3fa at which the transmitting side external connection terminal 9a of the device chip 3 is located, and narrower on the sides of the third side 3gc opposite the first side 3ga and the fourth side 3gd opposite the second side 3gb.

[0023] In the illustrated example, the top and bottom sides of the device chip 3 that are located on the upper side of Figure 2 are referred to as the first side 3ga, the left and right sides of the device chip 3 that are located on the left side of Figure 2 are referred to as the second side 3gb, the bottom and top sides of the device chip 3 that are located on the lower side of Figure 2 are referred to as the third side 3gc, and the right and left sides of the device chip 3 that are located on the right side of Figure 2 are referred to as the fourth side 3gd. A distance S1 between the first side 3ga and an outer edge 2e of the package substrate 2 located above it in Fig. 2 is larger than a distance S2 between the third side 3gc and an outer edge 2e of the package substrate 2 located below it in Fig. 2. At the same time, a distance S3 between the second side 3gb and an outer edge 2e of the package substrate 2 located to the left of it in Fig. 2 is larger than a distance S4 between the fourth side 3gd and an outer edge 2e of the package substrate 2 located to the right of it in Fig. 2. More specifically, the first side 3ga and the outer edge 2e of the package substrate 2 on one side thereof are substantially parallel to each other, with the gap S1 formed between them along the entire length of the first side 3ga, and the second side 3gb and the outer edge 2e of the package substrate 2 on one side thereof are substantially parallel to each other, with the gap S3 formed between them along the entire length of the second side 3gb.

[0024] In this type of acoustic wave device 1, a large amount of heat is likely to be generated near the transmitting external connection terminal 9a (Tx) among the external connection terminals 9. Such heat can cause damage to the IDT electrodes, so it is necessary to effectively release the heat to the outside. When the acoustic wave device 1 is viewed in a direction perpendicular to the functional surface 3a, the heat is transmitted to the sealing portion 4 and the package substrate 2, spreading concentrically around the transmitting external connection terminal 9a. In this embodiment, by positioning the device chip 3 on the package substrate 2 in a state where the center 2h of the package substrate 2 and the center 3c of the device chip 3 are not aligned as described above, the transfer area of ​​the heat generated near the transmitting external connection terminal 9a formed near one corner 3fa of the device chip 3 can be secured widely in the entire circumferential direction centered on the transmitting external connection terminal 9a. That is, the transfer area can be secured with a required width not only on the center 3c side of the device chip 3 based on the transmitting external connection terminal 9a, but also between the corner 3fa, the first side 3ga, the second side 3gb, and the outer edge 2e of the package substrate 2 positioned outside of these with the intervals S1 and S3. This makes it possible to effectively release the heat to the outside. In other words, in the acoustic wave device 1 according to this embodiment, it is possible to ensure that the transmission area is as large as possible without changing the size thereof, that is, the size of the package substrate 2.

[0025] In addition, in this embodiment, the heat dissipation wiring 2g formed on the package substrate 2 has a first portion 2ga connected to the transmitting side external connection terminal 9a under the device chip 3, and a second portion 2gb positioned within the gap S, and is configured to contact the sealing portion 4 at this second portion 2gb. It is preferable that the heat dissipation wiring 2g is configured so that its width is wider than that of normal wiring. In the illustrated example, both the first portion 2ga and the second portion 2gb of the heat dissipation wiring 2g are formed on one surface 2a of the package substrate 2. The second portion 2gb is formed along an imaginary diagonal line y (see FIG. 2) passing through a center 2h of the package substrate 2 and a corner 2i of the one surface 2a of the package substrate 2. One end of the second portion 2gb is connected to the first portion 2ga, and the other end of the second portion 2gb extends outward from a corner 3fa of the device chip 3 located in the vicinity of the transmitting-side external connection terminal 9a and is positioned within the interval S. More specifically, of the two corners 2i of the package substrate 2 located on the diagonal y passing through the position where the transmitting side external connection terminal 9a is formed, the second portion 2gb is located between the corner 2i of the package substrate 2 that forms the space S between the corner 3fa of the device chip 3 near the transmitting side external connection terminal 9a and the corner 3fa of the device chip 3. The vertical portion 4b of the sealing portion 4 is adapted to be in contact with the second portion 2gb at the interval S. As a result, in this embodiment, heat generated near the transmission side external connection terminal 9a can be easily dissipated to the outside through the sealing portion 4.

[0026] In the illustrated example, the other end of the second portion 2gb of the heat dissipation wiring 2g is further connected to a third portion 2gc (internal wiring) formed in a via 2j penetrating the package substrate 2, and the acoustic wave device 1 has an external connection terminal 2da for heat dissipation on the other surface 2b of the package substrate 2 through the third portion 2gc. This allows the heat to be dissipated to the side of the module substrate (not shown) by connecting the external connection terminal 2da for heat dissipation to the module substrate (not shown).

[0027] In this embodiment, the sealing portion 4 is made of a resin having high thermal conductivity, thereby further improving the heat dissipation. For such a resin, a filler made of a material having high thermal conductivity is used in an amount of 70 wt% to 90 wt% relative to the base resin. Such a filler is typically made of granules having a diameter of about 10 μm. Specifically, the resin constituting the inner layer 4c may be an epoxy resin containing a filler or a phenolic resin containing a filler. As the filler, typically, alumina, aluminum nitride, or diamond powder may be used.

[0028] Of course, the present invention is not limited to the above-described embodiments, but includes all embodiments that can achieve the object of the present invention. [Explanation of symbols]

[0029] 1. Acoustic Wave Devices 2 Package substrate 2a one side 2b Other side 2c Wiring 2d, 2da external connection terminals 2e Outer edge 2f side 2g heat dissipation wiring 2ga 1st part 2gb 2nd part 2gc 3rd part 2h center 2i corner 2j via 3. Device Chip 3a Functional aspect 3b Non-functional aspects 3c center 3d Outer Border 3e side 3f, 3fa corner 3ga 1st side 3gb Side 2 3gc Third side 3gd 4th side 4 Sealing part 4a Horizontal part 4b Vertical part 5. Gap 6. Interior Space 7 Functional elements 7a, 7aa, 7ab resonators 7b IDT electrode 7c reflector 7d electrode finger 7e Busbar 7f electrode finger 7g busbar 8 Wiring 9 External connection terminal 9a Transmitter external connection terminal 10. Bump 11 Circuit 11a Sender Filter 11b Receiver Filter 12 Grand S, S1, S2, S3, S4 interval x Propagation direction y diagonal

Claims

1. A package substrate having a rectangular plate shape; a device chip having a rectangular plate shape smaller in area than the package substrate and mounted on the package substrate with a functional surface thereof facing the package substrate and having functional elements including an IDT electrode on one surface of the package substrate; a sealing portion formed on the one surface side of the package substrate to form an internal space between the functional surface of the device chip and the one surface of the package substrate, the device chip has a transmitting side external connection terminal on the functional surface in the vicinity of one of four corners of the functional surface, the package substrate has heat dissipation wiring connected to the transmission-side external connection terminal via a bump, a gap is formed between an outer edge of the device chip and an outer edge of the package substrate at any position in a direction around the center of the device chip; An elastic wave device, in which the device chip is positioned on the package substrate with the center of the package substrate not coinciding with the center of the device chip, so that the gap is wider on the sides of a first side and a second side perpendicular to the first side of the device chip that form the corner near the transmitting side external connection terminal of the device chip, and narrower on the sides of a third side opposite the first side and a fourth side opposite the second side.

2. 2. The acoustic wave device of claim 1, wherein the heat dissipation wiring has a first portion connected to the transmitting external connection terminal under the device chip and a second portion positioned within the gap, and the second portion is adapted to contact the sealing portion.

3. 2. The acoustic wave device according to claim 1, wherein the device chip is a duplexer including a transmitting filter and a receiving filter as the functional elements, and the transmitting external connection terminal is connected to the transmitting filter.

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