JPWO2015190166A1 - Surface acoustic wave device - Google Patents

Abstract

Provided is a surface acoustic wave device capable of effectively improving heat dissipation. The support layer provided on the piezoelectric substrate 2 so as to have the piezoelectric substrate 2, the functional electrode 3 including the connection wiring provided on the piezoelectric substrate 2, and the opening 4A exposing the functional electrode 3 to the inside. 4, the cover member 5 provided on the upper surface of the support layer 4 so as to seal the opening 4A of the support layer 4, and the support layer 4 and the cover member 5 are penetrated in the thickness direction of the piezoelectric substrate 2. The via hole electrode 7 electrically connected to the connection wiring of the functional electrode 3 and the heat conduction having a higher thermal conductivity than the support layer 4 and penetrating the support layer 4 in the thickness direction of the piezoelectric substrate 2 A surface acoustic wave device 1 including a body 10.

Description

  The present invention relates to a surface acoustic wave device having a WLP (Wafer Level Package) structure.

  Conventionally, surface acoustic wave devices having a WLP structure have been widely used.

  In a surface acoustic wave device having a WLP structure, a support layer is provided so as to surround an acoustic wave resonator formed on a piezoelectric substrate. A cover member is provided on the support layer so as to seal a portion surrounded by the support layer. A hollow portion is formed by the piezoelectric substrate, the support layer, and the cover member. A via hole conductor is provided so as to penetrate the support layer and the cover member. The via-hole conductor is electrically connected to the outside through bumps.

  Patent Document 1 below discloses an example of a surface acoustic wave device having a WLP structure. In the surface acoustic wave device described in Patent Document 1, a raised layer is provided on a piezoelectric substrate. A metal film is continuously formed from the inter-terminal wiring to the raised layer. The metal film is in contact with the lower surface of the cover member. Thereby, it is said that heat dissipation can be improved.

  On the other hand, in the surface acoustic wave device having the WLP structure described in Patent Document 2 below, a structure for preventing the hollow portion from being crushed is described. A columnar member is provided in a region surrounded by the support layer. The upper end of the columnar member is in contact with the cover member. Thereby, crushing of the hollow portion is suppressed. A via-hole conductor is provided so as to penetrate the columnar member. The via hole conductor is joined to the connection wiring. Thereby, it is said that heat dissipation can be improved.

JP 2008-5241 A WO2012 / 120968

  However, in the surface acoustic wave device described in Patent Document 1, although the metal film is in contact with the cover member, the metal film does not directly radiate heat to the outside. Therefore, there has been a problem that heat dissipation cannot be sufficiently improved. Also, the raised layer must be provided separately from the support layer. For this reason, there is a problem that the manufacturing process becomes complicated. In the surface acoustic wave device described in Patent Document 2, the columnar member and the via-hole conductor are provided mainly for the purpose of suppressing the collapse of the hollow portion. Therefore, it was insufficient to improve heat dissipation.

  An object of the present invention is to provide a surface acoustic wave device that can further improve heat dissipation.

  The surface acoustic wave device according to the present invention includes the piezoelectric substrate, the connection wiring, the functional electrode provided on the piezoelectric substrate, and the opening that exposes the functional electrode to the inside. A support layer provided on the cover layer; a cover member provided on an upper surface of the support layer so as to seal the opening of the support layer; and the support layer and the cover in the thickness direction of the piezoelectric substrate. A via hole electrode that penetrates the member and is electrically connected to the connection wiring of the functional electrode, and has a higher thermal conductivity than the support layer, and penetrates the support layer in the thickness direction of the piezoelectric substrate A thermal conductor.

  In a specific aspect of the surface acoustic wave device according to the present invention, the support layer is disposed in a region surrounded by the opening, joined to the cover member, and provided on the piezoelectric substrate. including. The heat conductor is provided through the partition wall in the thickness direction of the piezoelectric substrate.

  In another specific aspect of the surface acoustic wave device according to the present invention, the thermal conductor is a conductor.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the thermal conductor is joined to the connection wiring sandwiched between the piezoelectric substrate and the support layer.

  In another specific aspect of the surface acoustic wave device according to the present invention, the thermal conductor is bonded to the surface of the piezoelectric substrate.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the thermal conductor continuously penetrates from the support layer to the cover member in the thickness direction of the piezoelectric substrate.

  In still another specific aspect of the surface acoustic wave device according to the present invention, a plurality of the heat conductors are provided. A heat radiator provided on the upper surface of the cover member so as to be joined to the plurality of heat conductors is further provided.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the heat radiator is a conductor.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the thermal conductor does not penetrate the cover member.

  In still another specific aspect of the surface acoustic wave device according to the present invention, no bump is bonded to the end of the heat conductor on the cover member side.

  ADVANTAGE OF THE INVENTION According to this invention, the surface acoustic wave apparatus which can improve heat dissipation further can be provided.

FIG. 1A is a plan view of a surface acoustic wave device according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA shown in FIG. FIG.1 (c) is sectional drawing which follows the BB line shown to Fig.1 (a). FIG. 2 is a cross-sectional view in a cross section passing through one of the side portions of the support layer of the surface acoustic wave device according to the second embodiment of the present invention. FIG. 3A is a plan view of the surface acoustic wave device according to the third embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along the line CC shown in FIG. is there. FIG. 4A is a plan view of a surface acoustic wave device according to a fourth embodiment of the present invention, and FIG. 4B is a cross-sectional view taken along the line DD shown in FIG. is there.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1A to FIG. 1C are a plan view of a surface acoustic wave device according to a first embodiment of the present invention, a step sectional view taken along line AA shown in FIG. It is sectional drawing which follows the BB line shown to (a).

The surface acoustic wave device 1 has a piezoelectric substrate 2. The piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiTaO ₃ . The piezoelectric substrate 2 may be made of piezoelectric ceramics.

  A plurality of functional electrodes 3 are formed on the piezoelectric substrate 2. In the present embodiment, the functional electrode 3 includes an IDT electrode. A surface acoustic wave can be excited by applying an AC voltage to the IDT electrode. The functional electrode 3 is made of an appropriate metal or alloy.

  The functional electrode 3 may have a reflector in addition to the IDT electrode. Alternatively, the functional electrode 3 may form a filter circuit including a plurality of IDT electrodes. Further, the number of functional electrodes 3 is arbitrary. The filter circuit can constitute a demultiplexing circuit including a transmission circuit and a reception circuit.

  Although not particularly illustrated, the functional electrode 3 further includes a connection wiring formed on the piezoelectric substrate 2.

  On the piezoelectric substrate 2, a support layer 4 is provided so as to have an opening 4A that exposes the functional electrode 3 to the inside. The support layer 4 has a rectangular frame shape. The support layer 4 is made of an appropriate resin. In addition, the shape of the support layer 4 is not specifically limited, What is necessary is just to have the opening part 4A.

  A cover member 5 is provided on the upper surface of the support layer 4 so as to seal the opening 4A of the support layer 4. A hollow portion is formed by the piezoelectric substrate 2, the support layer 4 and the cover member 5. The functional electrode 3 is provided so as to face the hollow portion. In the present embodiment, the cover member 5 is made of a photosensitive resin. The cover member 5 may be made of a resin other than the photosensitive resin.

  In the region surrounded by the opening 4A of the support layer 4 on the piezoelectric substrate 2, a plurality of partition walls 4B that are a part of the support layer 4 are provided. The plurality of functional electrodes 3 are provided with the respective partition walls 4B interposed therebetween. The partition wall 4 </ b> B is joined to the cover member 5. The cover member 5 is supported by the support layer 4, but is also supported by the partition wall 4B. By providing the partition part 4B, it is reinforced with respect to the pressure from the outside. The partition wall 4B is made of an appropriate resin. A plurality of partition walls 4B may not be provided.

  A plurality of via holes 6 penetrating the support layer 4 and the cover member 5 in the thickness direction of the piezoelectric substrate 2 are formed. Each via hole 6 is formed in a corner portion of the support layer 4. The via hole 6 may be formed in an appropriate portion other than the corner portion of the support layer 4. The thickness direction of the piezoelectric substrate 2 is a direction parallel to the normal line of the main surface of the piezoelectric substrate 2.

  Each via hole 6 is filled with a conductor, thereby forming a via hole electrode 7. Although not shown, each of the via hole electrodes 7 is electrically connected to the functional electrode 3. The via-hole electrode 7 is made of an appropriate metal or alloy.

  Bumps 8 are joined to the end of the via hole electrode 7 on the cover member 5 side. The via hole electrode 7 is electrically connected to the bump 8. The bump 8 is made of a bonding member having appropriate conductivity such as a solder or a resin containing a conductive filler. The surface acoustic wave device 1 is mounted on a circuit board or the like using bumps 8.

  A plurality of through holes 9 penetrating the support layer 4 are formed in each side portion connecting the corner portions of the support layer 4 in the thickness direction of the piezoelectric substrate 2. Each partition wall 4B is also formed with a plurality of through holes 9 penetrating each partition wall 4B in the thickness direction of the piezoelectric substrate 2. Each through hole 9 is provided from each partition wall portion 4 </ b> B to the cover member 5, and continuously passes through each partition wall portion 4 </ b> B and the cover member 5. A thermal conductor 10 is formed in each through hole 9. The heat conductor 10 is formed to fill the through hole 9. In the present embodiment, the heat conductor 10 is made of an appropriate metal or alloy. The heat conductor 10 may be formed of an appropriate material having a thermal conductivity higher than that of the support layer 4 other than a metal or an alloy. In the branching circuit having the transmission circuit and the reception circuit provided on the piezoelectric substrate 2, the plurality of thermal conductors 10 provided in the partition wall portion 4B located between the transmission circuit and the reception circuit are conductors. It is preferable. By providing the plurality of heat conductors 10 between the transmission circuit and the reception circuit, an electromagnetic shielding effect between the transmission circuit and the reception circuit can be obtained.

  In the present embodiment, the heat conductor 10 has a circular planar shape. The heat conductor 10 may have a planar shape other than a circular shape. Alternatively, the heat conductor 10 may have a planar shape having a length direction in a direction in which the side portion of the support layer 4 on which the heat conductor 10 is formed extends.

  The heat conductor 10 is bonded to the connection wiring of the functional electrode 3. Thereby, the heat generated from the functional electrode 3 can be conducted to the outside through the heat conductor 10. More specifically, a part of the connection wiring is positioned so as to overlap the support layer 4 on the piezoelectric substrate 2 when the piezoelectric substrate 2 is viewed from the thickness direction. In the above position, the heat conductor 10 is connected to the connection wiring.

  In the present embodiment, a plurality of thermal conductors 10 are provided on each side portion of the support layer 4. A plurality of heat conductors 10 are also provided in the partition wall portion 4B. Therefore, heat dissipation can be further enhanced. Further, since the heat conductor 10 is formed so as to fill the through holes 9, the contact area with the cover member 5 can be increased, and the heat conductor 10 is exposed on the cover member 5. Can do. Therefore, heat dissipation can be further improved. Therefore, the stability of the temperature characteristics of the surface acoustic wave device 1 can be effectively increased.

  In addition, the heat conductor 10 should just be provided in the at least 1 side part of the side parts of the support layer 4 at least. But like this embodiment, it is preferable that the several heat conductor 10 is each provided in each edge part of the support layer 4, and the partition part 4B. Thereby, heat dissipation can be further improved.

  Further, the heat conductor 10 may not be formed so as to fill the through hole 9. However, it is preferable that the thermal conductor 10 is formed so as to fill the through hole 9 as in the present embodiment. Thereby, heat dissipation can be further improved.

  Further, the heat conductor 10 may be bonded to the surface of the piezoelectric substrate 2 instead of the connection wiring. Thereby, the heat of the piezoelectric substrate 2 can be conducted to the outside through the heat conductor 10. However, it is preferable that the thermal conductor 10 is bonded to the connection wiring as in the present embodiment. The main heat source of the surface acoustic wave device 1 is a functional electrode 3. The heat generated in the functional electrode 3 can be directly conducted to the outside through the heat conductor 10. Therefore, the heat dissipation can be further effectively improved.

  Moreover, the partition part 4B is not essential and may be omitted. If the heat conductor 10 is provided in the support layer 4, heat dissipation can be improved. In that case, the surface acoustic wave device can be downsized.

  Next, a method for manufacturing the surface acoustic wave device according to this embodiment will be described.

  First, a plurality of functional electrodes 3 including connection wirings are formed on the piezoelectric substrate 2. The functional electrode 3 can be formed by, for example, a CVD method or a sputtering method.

  Next, the support layer 4 is formed so as to have an opening 4 </ b> A surrounding the plurality of functional electrodes 3. Further, a partition wall 4B is formed between the functional electrodes 3 so as to separate the functional electrodes 3 from each other. The support layer 4 and the partition walls 4B can be formed by, for example, a photolithography method. In this embodiment, at this time, exposure and etching are performed so as to remove via holes 6 in the support layer 4 and portions corresponding to the through holes 9 in the support layer 4 and the partition walls 4B.

  Next, a cover member 5 made of a photosensitive resin is provided on the upper surface of the support layer 4 so as to seal the opening 4 </ b> A of the support layer 4. Next, exposure and etching are performed to remove portions corresponding to the via hole 6 and the through hole 9 of the cover member 5. Thereby, the via hole 6 and the through hole 9 are formed. The via hole 6 is formed in the corner portion of the support layer 4. The through holes 9 are formed in each side portion of the support layer 4 and the partition wall portion 4B.

  In addition, after providing the cover member 5 on the upper surface of the support layer 4, the via hole 6 and the through hole 9 may be formed by laser processing or the like. In that case, the cover member 5 may be made of a resin other than the photosensitive resin.

  Next, a via hole electrode 7 is formed in the via hole 6. Further, the heat conductor 10 is formed in the through hole 9. At this time, the via-hole electrode 7 and the functional electrode 3 are electrically connected. Further, the heat conductor 10 is bonded to the connection wiring. The via-hole electrode 7 and the thermal conductor 10 can be formed by, for example, filling the via-hole 6 and the through-hole 9 with metal by an electrolytic plating method or an electroless plating method. In addition to the step of filling the via hole 6 with metal, the through hole 9 may be filled with an appropriate material having high thermal conductivity to form the thermal conductor 10.

  Next, a bump 8 that is a bonding member having conductivity is bonded to the end of the via hole electrode 7 on the cover member 5 side. The bump 8 is made of solder.

  Hereinafter, surface acoustic wave devices according to second to fourth embodiments of the present invention will be described.

  FIG. 2 is a cross-sectional view in a cross section passing through one of the side portions of the support layer of the surface acoustic wave device according to the second embodiment of the present invention.

  The through hole 19 of the surface acoustic wave device 11 penetrates the support layer 4 but does not penetrate the cover member 15. A heat conductor 20 is formed in the through hole 19 so as to fill the through hole 19. Although not specifically shown, functional electrodes including connection wirings are formed on the piezoelectric substrate 2. The heat conductor 20 is joined to the connection wiring. Further, the heat conductor 20 is in contact with the lower surface of the cover member 15. Thereby, heat generated from the functional electrode can be effectively conducted to the cover member 15. Therefore, heat dissipation can be further enhanced.

  However, it is preferable that the heat conductor 10 is exposed on the cover member 5 as in the first embodiment shown in FIG. Thereby, heat dissipation can be further enhanced.

  FIG. 3A and FIG. 3B are a plan view of a surface acoustic wave device according to a third embodiment of the present invention and a cross-sectional view taken along the line CC shown in FIG.

  Bumps are not joined to the end portion of the via hole electrode 7 in the surface acoustic wave device 21 on the cover member 5 side, and electrode lands 28 are joined. Other structures are the same as those in the first embodiment. The surface acoustic wave device 21 is mounted on a circuit board or the like using the electrode land 28. Also in the present embodiment, the heat dissipation can be further improved, as in the first embodiment. As described above, as long as the heat conductor 10 is provided, the degree of freedom in design can be increased while improving heat dissipation.

  FIG. 4A and FIG. 4B are a plan view of a surface acoustic wave device according to a fourth embodiment of the present invention and a cross-sectional view taken along the line DD shown in FIG.

  On the upper surface of the cover member 5 of the surface acoustic wave device 31, a radiator 40A is provided at a position overlapping the first side portion 4a and the third side portion 4c of the support layer 4 in plan view. A plurality of heat conductors 10 are joined to each heat radiator 40A. The radiator 40A is provided so as not to contact the electrode land 28. Structures other than those described above are the same as in the third embodiment. In the present embodiment, the radiator 40A is made of an appropriate metal or alloy. When the heat radiator 40A and the plurality of heat conductors 10 are conductive, the heat sink 40A provided on the upper surface of the cover member 5 and the two adjacent heat conductors 10 are connected to form a ring-shaped coil. Can be configured. For example, by providing a plurality of ring-shaped coils so as to surround the transmission circuit or the branching circuit including the functional electrode 3, a ring-shaped coil is formed using the same manufacturing process as the via hole electrode 7 and the electrode land 28 of the WLP structure. Therefore, it is possible to provide the surface acoustic wave device 31 in which the electromagnetic shielding effect is enhanced by the inductance of the ring-shaped coil. The heat radiating body 40 </ b> A can be implemented by a modification provided between the support layer 4 and the cover member 5. In addition, 40 A of heat radiators may be formed with the appropriate material whose heat conductivity is higher than a support layer other than a metal or an alloy.

  Note that the heat radiating body 40 </ b> A only needs to be joined to at least one heat conductor 10. Further, the heat radiator 40 </ b> A only needs to be provided at a position overlapping at least one of the side portions of the support layer 4 on the upper surface of the cover member 5. Further, the radiator 40A may be provided in a position other than the positions of the sides of the support layer 4 on the upper surface of the cover member 5, and the radiator 40A may be joined to the thermal conductor 10 provided in the partition wall 4B. Furthermore, the radiator 40 </ b> A may be provided at a position sandwiched between the cover member 5 and the support layer 4.

  As described above, each heat radiator 40 </ b> A is joined to the plurality of heat conductors 10. The planar area of the heat radiator 40A is larger than the total planar area of the plurality of thermal conductors 10 connected to the radiator 40A. Therefore, the area where heat can be efficiently radiated to the outside can be further increased. Therefore, heat dissipation can be improved more effectively.

  Next, an example of a mounting structure on which the surface acoustic wave device according to the first embodiment of the present invention is mounted is shown below.

  The mounting structure of the surface acoustic wave device has a circuit board. The circuit board has a ground terminal. The thermal conductor of the surface acoustic wave device is joined to the ground terminal. Thereby, the heat generated from the surface acoustic wave device can be effectively conducted to the circuit board side. Therefore, the heat dissipation of the surface acoustic wave device can be effectively enhanced. When the surface acoustic wave device of the present invention is applied to a duplexer including a transmission filter and a reception filter, the number of heat conductors provided in the transmission filter having a larger applied power than the reception filter is equal to that of the reception filter. More than the number of thermal conductors is preferable.

DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave apparatus 2 ... Piezoelectric substrate 3 ... Functional electrode 4 ... Support layer 4A ... Opening 4B ... Partition part 4a ... 1st edge part 4c ... 3rd edge part 5 ... Cover member 6 ... Via hole 7 ... Via hole Electrode 8 ... Bump 9 ... Through hole 10 ... Thermal conductor 11 ... Surface acoustic wave device 15 ... Cover member 19 ... Through hole 20 ... Thermal conductor 21 ... Surface acoustic wave device 28 ... Electrode land 31 ... Surface acoustic wave device 40A ... Radiator

Claims (10)

A piezoelectric substrate;
Functional electrodes including connection wiring, provided on the piezoelectric substrate;
A support layer provided on the piezoelectric substrate so as to have an opening that exposes the functional electrode to the inside;
A cover member provided on the upper surface of the support layer so as to seal the opening of the support layer;
A via-hole electrode that penetrates the support layer and the cover member in the thickness direction of the piezoelectric substrate and is electrically connected to the connection wiring of the functional electrode;
A surface acoustic wave device comprising: a thermal conductor having a higher thermal conductivity than the support layer and penetrating the support layer in a thickness direction of the piezoelectric substrate. The support layer is disposed in a region surrounded by the opening, joined to the cover member, and includes a partition wall provided on the piezoelectric substrate,
The surface acoustic wave device according to claim 1, wherein the thermal conductor is provided so as to penetrate the partition wall portion in a thickness direction of the piezoelectric substrate.   The surface acoustic wave device according to claim 1, wherein the heat conductor is a conductor.   The surface acoustic wave device according to claim 1, wherein the thermal conductor is bonded to the connection wiring sandwiched between the piezoelectric substrate and the support layer.   The surface acoustic wave device according to claim 1, wherein the thermal conductor is bonded to a surface of the piezoelectric substrate.   The surface acoustic wave device according to any one of claims 1 to 5, wherein the thermal conductor continuously penetrates from the support layer to the cover member in a thickness direction of the piezoelectric substrate.   The surface acoustic wave device according to claim 6, further comprising a heat dissipating member provided on a top surface of the cover member so as to be provided with a plurality of the heat conductors and joined to the plurality of heat conductors.   The surface acoustic wave device according to claim 7, wherein the radiator is a conductor.   The surface acoustic wave device according to claim 1, wherein the heat conductor does not penetrate the cover member.   The surface acoustic wave device according to any one of claims 1 to 9, wherein a bump is not bonded to an end portion of the thermal conductor on the cover member side.

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