Elastic wave device

Abstract

To provide an elastic wave device having a CSP structure, having a new structure capable of reasonably improving heat dissipation.SOLUTION: Each of a plurality of sealing bodies 3 includes a wall part 3a made of an insulating resin surrounding a predetermined number of resonators 9 and a roof part 3b made of an insulating resin formed on the wall part 3a to form a sealing space 14 of the resonators 9. A distance L2 between a functional surface 2a and an upper surface 7a of a second metal layer 7 is larger than a distance L1 between a functional surface 2a and an upper surface 6a of a first metal layer 6, and a distance L3 between the functional surface 2a and an upper end 3ab of the wall part 3a is larger than the distance L2 between the functional surface 2a and the upper surface 7a of the second metal layer 7. At least a part of the plurality of sealing bodies 3 is configured to support a part of the roof part 3b by the second metal layer 7 in the sealing space 14.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] An acoustic wave device with a CSP (Chip Size Package) structure has the structure shown in Fig. 8. In the figure, reference numeral 100 denotes a device chip having at least one functional surface made of a piezoelectric material, reference numeral 101 denotes a resonator made of a metal film formed on the surface of the device chip 100, and reference numeral 103 denotes a package substrate. The device chip 100 is mounted on a package substrate 103 via bumps 104. A gap is formed between the device chip 100 and the package substrate 103 by the bumps 104. A sealing resin 105 is formed on the side of the package substrate 103 on which the device chip 100 is mounted, covering the other surface opposite to the one surface of the device chip 100 and its side surface. This sealing resin 105 provides the acoustic wave device with an internal space 106 between the one surface of the device chip 100 and the package substrate 103, and the resonator 101 is positioned within this internal space 106. Here, in this type of acoustic wave device, there is a strong demand for improved heat dissipation. Summary of the Invention [Problem to be solved by the invention]

[0003] The main problem to be solved by the present invention is to provide a new structure that can rationally improve heat dissipation in this type of CSP structure acoustic wave device. [Means for solving the problem]

[0004] In order to achieve the above object, the present invention provides an acoustic wave device comprising: a device chip; a plurality of sealing bodies for sealing a required number of the plurality of resonators formed on the functional surface of the device chip; a package substrate on which the device chip is mounted with a gap between the functional surface of the device chip and the package substrate; a filling portion made of a high heat dissipation resin filled in the gap, a first metal layer including the resonator and first-layer wiring, and a second metal layer including second-layer wiring, are formed on the functional surface of the device chip; each of the plurality of sealing bodies includes a wall portion made of insulating resin surrounding a required number of the resonators, and a roof portion formed on the wall portion and forming a sealing space for the resonators in cooperation with the functional surface and the wall portion; a distance between the functional surface and the upper surface of the second metal layer is larger than a distance between the functional surface and the upper surface of the first metal layer, and a distance between the functional surface and the upper end of the wall portion is larger than a distance between the functional surface and the upper surface of the second metal layer, Moreover, at least some of the sealing bodies are configured so that a portion of the roof portion is supported by the second metal layer within the sealed space.

[0005] One aspect of the present invention is that a wall gap is formed between the wall portions of adjacent sealing bodies, and both or either of the first layer wiring and the second layer wiring are in contact with the filling portion in this wall gap.

[0006] In addition, one aspect of the present invention is that at least some of the multiple sealing bodies house the resonator divided into two or more split resonators in series, and a part of the roof portion is supported by the second metal layer between adjacent split resonators.

[0007] Furthermore, one aspect of the present invention is to form the roof portion constituting the sealing body in a curved shape so that the central portion supported by the second metal layer is closer to the functional surface and the outer edge portion supported by the wall portion is farther away from the functional surface. [Effects of the Invention]

[0008] According to this invention, heat generated by applying a signal to the device chip is efficiently dissipated to the outside through the sealing bodies and the filling portion formed in the functional surface of the device chip. The resonators formed on the functional surface are sealed in sealing bodies in groups of a required number, and multiple small chambers containing the resonators are formed on the functional surface. In this way, the sealing body is less likely to be crushed when the filling portion is formed, compared to when the resonators formed on the functional surface are sealed in a single sealing body. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of an acoustic wave device according to one embodiment of the present invention taken along line BB in FIG. [Figure 2] FIG. 2 is a cross-sectional view of the acoustic wave device taken along line AA in FIG. 1, and does not include the sealant. [Figure 3] FIG. 3 is an enlarged view of the C portion in FIG. 2, and the roof portion that constitutes the sealing body is indicated by a two-dot chain line. [Figure 4] FIG. 4 is a cross-sectional view taken along line DD in FIG. [Figure 5] FIG. 5 is an enlarged view of the main part of FIG. 4, and the filling part is omitted. [Figure 6] FIG. 6 is a diagram showing an example of a configuration of a resonator formed on the functional surface of a device chip that constitutes the acoustic wave device. [Figure 7] FIG. 7 is a configuration diagram showing an example of a circuit formed on the functional surface of the device chip. [Figure 8] FIG. 8 is a cross-sectional view of a conventional acoustic wave device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Exemplary embodiments of the present invention will now be described with reference to Figures 1 to 7. An acoustic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices and the like.

[0011] The acoustic wave device 1 includes a device chip 2, a plurality of sealing bodies 3, a package substrate 4, and a filling portion 5.

[0012] (Device Chip 2) The device chip 2 has the function of propagating elastic waves. The surface of the device chip 2 that has the function of propagating elastic waves (the surface made of a piezoelectric material) is the functional surface 2a of the device chip 2. Typically, lithium tantalate or lithium niobate is used as the piezoelectric material in the device chip 2, and the device chip 2 may also be configured by laminating sapphire, silicon, alumina, spinel, quartz, glass, or the like on top of these.

[0013] Typically, the device chip 2 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. Therefore, when the device chip 2 is viewed from a direction perpendicular to the functional surface 2 a, the outline of the functional surface 2 a has a rectangular shape.

[0014] 2, a desired conductive pattern 8 made of a first metal layer 6 and a second metal layer 7 (described later) is formed on the functional surface 2a of the device chip 2. Typically, the pattern 8 is formed on the functional surface 2a by a conductive metal film formed on a wafer that will become the device chip 2 by photolithography and etching.

[0015] In the manufacturing process of the acoustic wave device 1, the first metal layer 6 is formed prior to the creation of the second metal layer 7. As shown in Figures 4 and 5, the first metal layer 6 forms a resonator 9 and a first-layer wiring 10. In the manufacturing process of the acoustic wave device 1, the second metal layer 7 is formed after the first metal layer 6 is formed. As shown in Figures 4 and 5, the second metal layer 7 forms second-layer wiring 11.

[0016] 5, the pattern 8 includes a two-layer portion 8a in which the first metal layer 6 and the second metal layer 7 overlap each other, and in this two-layer portion 8a, the second metal layer 7 is positioned on the first metal layer 6. The pattern 8 may include a single-layer portion in which only the first metal layer 6 is present on the functional surface 2a, or may include a single-layer portion in which only the second metal layer 7 is present on the functional surface 2a. The resonators 9 are connected to each other by either or both of the first layer wiring 10 and the second layer wiring 11, and the resonators 9 are connected to pads 13 for bumps indicated by reference numeral 12 in the figure (see FIG. 1).

[0017] (Sealing body 3) The sealing body 3 seals each required number of the plurality of resonators 9 formed on the functional surface 2a of the device chip 2. A plurality of sealing bodies 3 are formed on the functional surface 2a of the device chip 2. As shown in Fig. 1, a plurality of sealing bodies 3 are formed on the functional surface 2a of the device chip 2. The following description will focus on the two sealing bodies 3 (see Fig. 3) formed in the lower left corner of Fig. 2. The configurations of the sealing bodies 3 other than these two sealing bodies 3 are substantially the same as the configurations of these two sealing bodies 2, so the description thereof will be omitted.

[0018] In the illustrated example, one of the two sealing bodies 3 (see FIG. 3) located at the lower left of the device chip 2 shown in FIG. 2 seals two split resonators 9a, and the other seals three split resonators 9a (see FIG. 4).

[0019] Each of the plurality of sealing bodies 3 is composed of a wall portion 3a (support layer) and a roof portion 3b (cover layer).

[0020] The wall portion 3a is made of insulating resin and surrounds a required number of the resonators 9. In the illustrated example, the wall portion 3a is formed in the shape of a quadrangular frame when the functional surface 2a is viewed in a direction perpendicular to the functional surface 2a (see FIG. 3). In the manufacturing process of the acoustic wave device 1, the wall portions 3a are formed after the second metal layer 7 is formed. Typically, the wall portions 3a are formed by overlaying a film made of a resin material that will form the wall portions 3a on a wafer that will become the device chip 2, or by applying the resin material, and then using photolithography and etching.

[0021] In the portion where the second metal layer 7 exists, the wall portion 3a is located on the second metal layer 7. That is, the lower end 3aa (the end on the functional surface 2a side) of the wall portion 3a is fixed to the upper surface 7a (the surface opposite to the functional surface 2a side) of the second metal layer 7. In the portion where the second metal layer 7 is not present, the wall portion 3a is located on the functional surface 2a or the first metal layer 6. In other words, the lower end 3aa of the wall portion 3a is fixed to the functional surface 2a or the upper surface 6a of the first metal layer 6.

[0022] The roof portion 3b is typically made of insulating resin. The roof portion 3b is formed on the wall portion 3a and cooperates with the functional surface 2a and the wall portion 3a to form the sealed space 14 of the resonator 9 (see FIG. 5). The roof portion 3b is plate-shaped with its lower surface 3ba (the surface on the functional surface 2a side) facing the functional surface 2a. The roof portion 3b is supported on the wall portion 3a by fixing its outer edge portion 3bc to the upper end 3ab of the wall portion 3a. The roof portion 3b is integrated with the wall portion 3a so as to close the open area formed by the upper end 3ab of the wall portion 3a without any gaps.

[0023] The roof portion 3b is formed after the wall portion 3a is generated in the manufacturing process of the acoustic wave device 1. Typically, the roof portion 3b is formed by photolithography and etching after a film made of a resin material that forms the roof portion 3b is laid on a wafer that becomes the device chip 2.

[0024] In addition, in this embodiment, as shown in Figure 5, the distance L2 between the functional surface 2a and the upper surface 7a of the second metal layer 7 is made larger than the distance L1 between the functional surface 2a and the upper surface 6a of the first metal layer 6. At the same time, the distance L3 between the functional surface 2a and the upper end 3ab of the wall portion 3a is set to be larger than the distance L2 between the functional surface 2a and the upper surface 7a of the second metal layer 7. In this embodiment, at least some of the sealing bodies 3 are configured so that part of the roof portion 3b is supported by the second metal layer 7 within the sealing space .

[0025] As a result, in this embodiment, the second metal layer 7, which becomes the second-layer wiring 11 connecting the resonators 9 or the split resonators 9a, is used to support the roof portion 3b that constitutes the sealed space 14 between the resonators 9 or the split resonators 9a, thereby preventing the collapse of the sealed space 14. In particular, the second metal layer 7, which becomes the second-layer wiring 11, can be easily formed to have a width of about 2 to 3 μm in the direction parallel to the functional surface 2a. Therefore, even if a portion of the roof portion 3b in the sealed space 14 is supported by the second metal layer 7, the size of the sealing body 3 in the direction parallel to the functional surface 2a is not unnecessarily increased, and the support structure can be realized without increasing the number of manufacturing processes for the acoustic wave device 1.

[0026] 3, when the functional surface 2a is viewed from a direction perpendicular thereto, between two opposing sides 3ac of the wall portion 3a forming a rectangular frame, rib-like support portions 7b parallel to the sides 3ac are formed by the second metal layer 7 that becomes the second-layer wiring 11, with a gap between the two opposing sides 3ac, and the support portions 7b support the roof portion 3b between the two sides 3ac. The lower ends of the support portions 7b are fixed to the upper surface 6a of the first metal layer 6 that becomes the first-layer wiring 10, and the upper ends of the support portions 7b are fixed to the lower surface 3ba of the roof portion 3b (see FIG. 5).

[0027] In the illustrated example, at least some of the multiple sealing bodies house the resonator 9, which is divided in series into two or more split resonators 9a, and support a portion of the roof portion 3b between adjacent split resonators 9a by the second metal layer 7. In the illustrated example, the sealing body 3 located on the left side of Figures 3 to 5 houses the resonator 9 divided in series into two split resonators 9a, and between the two split resonators 9a, a part of the roof portion 3b is supported by the second metal layer 7 (support portion 7b). Furthermore, the sealing body 3 located on the right side of Figures 3 and 4 houses the resonator 9 divided in series into three split resonators 9a, and a support portion 7b is located between each of the adjacent split resonators 9a, so that the sealing body 3 has two support portions 7b between the two opposing side portions 3ac of the wall portion 3a.

[0028] In addition, in the illustrated example, the roof portion 3b constituting the sealing body 3 is formed in a curved shape so that the central portion 3bb supported by the second metal layer 7 (support portion 7b) is closer to the functional surface 2a and the outer edge portion 3bc supported by the wall portion 3a is farther away from the functional surface 2a (see Figure 5).

[0029] (Package substrate 4) The device chip 2 is mounted on the package substrate 4 with a gap 15 between the package substrate 4 and the functional surface 2 a of the device chip 2 . In the illustrated example, as shown in FIG. 1, bumps 12 made of a conductive material such as solder are fixed to pads 13 formed on the functional surface 2a of the device chip 2, and are welded to pads 4a formed on the mounting side surface 4b of the package substrate 4 of the device chip 2, thereby connecting the circuit of the device chip 2 to the circuit of the package substrate 4. A gap 15 including the thickness of the bumps 12 is formed between the functional surface 2 a of the device chip 2 and the mounting surface 4 b of the package substrate 4 . Specifically, in a direction perpendicular to the functional surface 2a, the gap 15 is larger than the thickness of the sealing body 3, and a gap is formed between the sealing body 3 and the mounting side surface 4b of the package substrate 4.

[0030] Typically, a device chip 2 obtained by dicing a wafer that has gone through the steps of generating the first metal layer 6, the second metal layer 7, the wall portion 3a, and the roof portion 3b is flip-chip mounted to an aggregate substrate (not shown) that becomes the package substrate 4.

[0031] In the figure, symbol 4c indicates internal wiring of the package substrate 4, symbol 4d indicates an external input / output pad formed on the surface opposite to the mounting surface 4b, and the acoustic wave device 1 is mounted on a main board or the like using the external input / output pad 4d of the package substrate 4.

[0032] (Filling section 5) The filling portion 5 is made of a highly heat-dissipating resin and is filled into the gap 15 . In the illustrated example, a part of the molding part 16 made of a high heat dissipation resin serves as the filling part 5. As shown in Fig. 1, the molding part 16 covers the surface 2b opposite to the functional surface 2a of the device chip 2 and the side surface 2c (thickness side surface) of the device chip 2, and is filled to fill the gap 15, thereby forming the filling part 5. The entire outer surface of each of the plurality of sealing bodies 3 within the gap 15 is covered with the high heat dissipation resin that forms the filling portion 5.

[0033] Such molding portion 16 is typically formed by placing a workpiece in which the device chip 2 is mounted on the package substrate 4 in a mold and then performing compression molding.

[0034] Heat generated by applying a signal to the device chip 2 is efficiently dissipated to the outside through the sealing bodies 3 and the filling portion 5 formed on the functional surface 2a of the device chip 2. The required number of resonators 9 formed on the functional surface 2a are sealed in the sealing bodies 3, and multiple small chambers containing the resonators 9 are formed on the functional surface 2a. In this way, the sealing body 3 is less likely to be crushed when the filling portion 5 is formed, compared to when the resonators 9 formed on the functional surface 2a are sealed in a single sealing body 3.

[0035] 1, 3, and 4, in this embodiment, the plurality of sealing bodies 3 formed as described above are each configured to form a wall gap 17 between the wall portions 3a of the adjacent sealing bodies 3. In the wall gap 17, both or either one of the first-layer wiring 10 and the second-layer wiring 11 is in contact with the filling portion 5 (in FIG. 4, both the first-layer wiring 10 and the second-layer wiring 11 are in contact with the filling portion 5). As a result, in areas on the functional surface 2a other than the region where the resonator 9 is formed, both or either one of the first-layer wiring 10 and the second-layer wiring 11 is in direct contact with the filling portion 5, thereby ensuring efficient heat dissipation.

[0036] The highly heat-dissipating resin used to make up the filling portion 5 contains filler made of a substance with high thermal conductivity in a range of 70 wt% to 90 wt% relative to the base resin. Such filler is typically formed as granules with a diameter of about 2 to 10 μm. Specifically, the high heat dissipation resin may be an epoxy resin containing a filler or a phenolic resin containing a filler, and the filler may typically be alumina, aluminum nitride, or diamond powder.

[0037] Typically, the first metal layer 6 constituting the resonator 93 and the first layer wiring 10 is made of a metal film having a thickness of 0.15 to 0.4 μm in the direction perpendicular to the functional surface 2 a of the device chip 2 . Typically, the second metal layer 7 constituting the second layer wiring 11 is made of a metal film having a thickness of 2 to 5 μm in the direction perpendicular to the functional surface 2 a of the device chip 2 . Furthermore, the wall portion 3a is typically configured to have a thickness in a direction perpendicular to the functional surface 2a of the device chip 2 (the height of the wall portion 3a body b based on the functional surface 2a) of 5 to 10 μm. The roof portion 3b is typically configured to have a thickness of 5 to 10 μm. Furthermore, the package substrate 4 is typically configured to have a thickness of 100 to 200 μm. The acoustic wave device 1 configured in this manner typically has a thickness of about 0.35 to 0.45 mm. In each drawing, the thickness of the components of the acoustic wave device 1 is exaggerated to make it easier to understand the configuration of the device.

[0038] 6 shows an example of a split resonator 9a constituting the resonator 9. The split resonator 9a has an IDT electrode 9b and a reflector 9c formed on either side of the IDT electrode 9b. The IDT electrode 9b is composed of an electrode pair, and each electrode pair has multiple electrode fingers 9d arranged in parallel so that their length direction intersects the propagation direction x of the acoustic wave, and each electrode pair is connected by a busbar 9e at one end of the electrode fingers. The reflector 9c has multiple electrode fingers 9f arranged in parallel so that their length direction intersects the propagation direction x of the acoustic wave, and each electrode finger 9d is connected by a busbar 9g at the ends thereof.

[0039] FIG. 7 shows the concept of an example of a circuit 18 provided on one device chip 2. Reference numeral 90 denotes a resonator 9 connected in series between input / output ports 18a, reference numeral 91 denotes a resonator 9 connected in parallel between input / output ports 18a, and reference numeral 18b denotes a ground. In FIG. 7, each resonator 90, 91 sealed in one sealing body 3 is enclosed by a dotted line, and each resonator 90, 91 is composed of two or more split resonators 9a. The resonator 91 designated by reference numeral E in FIG. 7 corresponds to the resonator 9 on the left side in FIG. 4, and the resonator 91 designated by reference numeral F in FIG. 7 corresponds to the resonator 9 on the right side in FIG. 4. The number and arrangement of the resonators 9 can be changed as necessary. In the example shown in FIG. 7, a ladder-type filter is configured.

[0040] It should be noted that 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]

[0041] 1. Acoustic wave devices 2. Device chip 2a Functional aspect 2b side 2c side 3 Sealing body 3a Wall section 3aa bottom end 3ab top edge 3ac side part 3b Roof section 3ba bottom 3bb central part 3bc outer edge 4 Package substrate 4a pad 4b Mounting side 4c internal wiring 4d External input / output pad 5 Filling section 6 1st metal layer 6a Top side 7 Second metal layer 7a Top side 7b Support part 8 patterns 8a 2 layer part 9, 90, 91 resonator 9a split resonator 9b IDT electrode 9c reflector 9d electrode finger 9e Busbar 9f electrode finger 9g busbar 10 1st layer wiring 11 2nd layer wiring 12 Bump 13 Pad 14 Sealed space 15 Gap 16 Molding section 17 Wall gap 18 circuits 18a I / O port 18b Grand x Propagation direction

Claims

1. A device chip; a plurality of sealing bodies for sealing a required number of the plurality of resonators formed on the functional surface of the device chip; a package substrate on which the device chip is mounted with a gap between the functional surface of the device chip and the package substrate; a filling portion made of a high heat dissipation resin filled in the gap, a first metal layer including the resonator and first-layer wiring, and a second metal layer including second-layer wiring, are formed on the functional surface of the device chip; each of the plurality of sealing bodies includes a wall portion made of insulating resin surrounding a required number of the resonators, and a roof portion formed on the wall portion and forming a sealing space for the resonators in cooperation with the functional surface and the wall portion; a distance between the functional surface and the upper surface of the second metal layer is larger than a distance between the functional surface and the upper surface of the first metal layer, and a distance between the functional surface and the upper end of the wall portion is larger than a distance between the functional surface and the upper surface of the second metal layer, Moreover, in the acoustic wave device, at least some of the sealing bodies are configured such that a portion of the roof portion is supported by the second metal layer within the sealing space.

2. 2. The acoustic wave device of claim 1, wherein a wall gap is formed between the wall portions of adjacent sealing bodies, and both or either one of the first layer wiring and the second layer wiring contacts the filling portion in this wall gap.

3. 2. The acoustic wave device according to claim 1, wherein at least some of the sealing bodies house the resonator divided into two or more split resonators in series, and a portion of the roof portion is supported by the second metal layer between adjacent split resonators.

4. 2. The acoustic wave device according to claim 1, wherein the roof portion constituting the sealing body is curved so that the central portion supported by the second metal layer is closer to the functional surface and the outer edge portion supported by the wall portion is farther away from the functional surface.

Images