Elastic wave device

Abstract

The invention discloses an elastic wave device. The elastic wave device includes: a package substrate; a device chip mounted on one surface of the package substrate; the sealing part comprises a first part and a second part, the first part covers the non-functional surface of the device chip, and the second part extends from the first part and covers the side surface in the thickness direction between the functional surface and the non-functional surface of the device chip until reaching one surface of the packaging substrate; an internal space is formed between the functional surface of the device chip and one surface of the packaging substrate; and a plurality of metal pillars provided on the package substrate, protruding from the one surface, and embedded in the second portion of the sealing portion. According to the elastic wave device, high mechanical integrity between the sealing part and the packaging substrate can be ensured, and meanwhile, heat generated by the device chip can be effectively dissipated to the outside.

Description

Technical Field

[0001] The present invention relates to an improved elastic wave device, which is suitable for frequency filters in mobile communication devices and the like. Background Art

[0002] As an electronic component including a surface acoustic wave (SAW) element having a chip scale package (CSP) structure, there is a technology described in Patent Document 1, for example.

[0003] The structure described in Patent Document 1 is as follows: The SAW element (device chip) is mounted on a support substrate (package substrate) through an opposed space, and the SAW element is covered in a sealing portion formed on the support substrate, so that the opposed space becomes an internal space.

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-197921. Summary of the Invention

[0005] An object of the present invention is to provide an elastic wave device having a CSP structure, which can ensure high mechanical integration between a sealing portion and a package substrate, and can effectively conduct heat generated on a device chip due to an input signal to the outside.

[0006] To achieve the above object, the present invention provides an elastic wave device, including: A package substrate; A device chip, mounted on one surface of the package substrate, having opposite functional surfaces and non-functional surfaces, the functional surface facing the package substrate, and a functional element including an IDT electrode is provided on the functional surface; A sealing portion, including a first portion and a second portion, wherein the first portion covers the non-functional surface of the aforementioned device chip, and the second portion extends from the first portion to cover the side surface in the thickness direction between the functional surface and the non-functional surface of the aforementioned device chip until reaching one surface of the aforementioned package substrate, so as to form an internal space between the functional surface of the aforementioned device chip and one surface of the aforementioned package substrate; A plurality of metal column portions, provided on the aforementioned package substrate and protruding from the aforementioned one surface, and built in the second portion of the aforementioned sealing portion.

[0007] In some embodiments, the area of contact between the column portion and the sealing portion is preferably more than 3 times the area of contact between the column portion and the package substrate.

[0008] In some embodiments, all or part of the surface of the column portion is a rough surface.

[0009] In some embodiments, the column portion gradually thickens in a portion near its protruding end.

[0010] In some embodiments, the protruding end of the column portion forms a head shape.

[0011] In some embodiments, the column portion is electrically connected to a ground pattern formed on the package substrate.

[0012] In some embodiments, when observing the elastic wave device in a direction perpendicular to one surface of the package substrate, a plurality of column portions are arranged around the device chip at intervals, and a gap is maintained between adjacent column portions.

[0013] In some embodiments, the height of the column portion is preferably greater than the distance between the functional surface of the device chip and the surface of the package substrate.

[0014] In some embodiments, a gap is provided between the column portion and the side surface of the device chip, and a gap is also provided between the column portion and the outer edge of the package substrate.

[0015] In some embodiments, the column portion has a columnar structure, having a base portion and a protruding end portion opposite to the base portion, and the protruding end portion is positioned at a height level between the functional surface and the non-functional surface of the device chip.

[0016] Through the elastic wave device of the present invention, while ensuring the mechanical integrity between the sealing portion and the package substrate in height, the heat generated in the device chip can be effectively transferred to the package substrate and dissipated to the outside. Description of the Drawings

[0017] Figure 1 is a plan schematic view of an elastic wave device (the first example) according to an embodiment of the present invention.

[0018] Figure 2 is Figure 1 a sectional structure diagram at the position of line A-A in

[0019] Figure 3 is Figure 1 a sectional structure diagram at the position of line B-B in

[0020] Figure 4 is a structural diagram of an example of a resonator formed on a device chip constituting the above-mentioned first example.

[0021] Figure 5 is a structural diagram of an example of a circuit formed on a device chip constituting the above-mentioned first example.

[0022] Figure 6It is a main sectional view showing an example of the formation process of the column part constituting the above-mentioned first example, and the process is carried out in the order of FIGS. (a), (b), and (c).

[0023] Figure 7 It is a main sectional view of the second example in which the column structure of the above-mentioned first example is modified.

[0024] Figure 8 It is a main sectional view of the third example in which the column structure of the above-mentioned first example is modified.

[0025] Figure 9 It is a main sectional view showing an example of the formation process of the column part constituting the above-mentioned third example, and the process is carried out in the order of FIGS. (a), (b), and (c).

[0026] Figure 10 It is a main sectional view of the fourth example in which the column structure of the above-mentioned first example is modified.

[0027] Figure 11 It is a main sectional view showing an example of the formation process of the column part constituting the above-mentioned fourth example, and the process is carried out in the order of FIGS. (a), (b), (c), (d), and (e).

[0028]

Symbol Explanation

[0029] The embodiments will be described below with reference to the accompanying drawings. In each figure, the same or corresponding parts are marked with the same reference signs. The repeated description of the corresponding parts is appropriately simplified or omitted.

[0030] Unless otherwise defined, the technical terms or scientific terms involved in this disclosure shall have the general meaning understood by those with ordinary skills in the technical field to which this disclosure belongs. In this disclosure, words such as "a", "an", "one kind", "the", "these", etc. do not indicate a limitation in quantity, and they can be singular or plural. The terms "including", "comprising", "having" and any variants thereof involved in this disclosure are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The terms "connected", "coupled", etc. involved in this disclosure do not limit to physical or mechanical connections, but may include electrical connections, whether directly or indirectly connected. The term "plurality" involved in this disclosure means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this disclosure only distinguish similar objects and do not represent a specific order for the objects.

[0031] The following is combined with Figures 1 to 11A detailed description is given of typical embodiments of the present invention. The surface acoustic wave device 1 in this embodiment is applicable to uses such as frequency filters in mobile communication devices.

[0032] The surface acoustic wave device 1 includes a package substrate 2 and a device chip 3 mounted on one surface 2a of the package substrate 2, and the functional surface 3a of the device chip 3 faces the one surface 2a. A resonator 7a serving as a functional element 7 is formed on the functional surface 3a of the device chip 3, and the resonator 7a includes an IDT electrode 7b (see Figure 4 ).

[0033] In some embodiments, the side length of the device chip 3 is 0.5 mm to 1 mm, the thickness is 0.15 mm to 0.2 mm, and it forms a rectangular plate-like structure. The side length of the package substrate 2 is 0.7 mm to 3 mm, the thickness is 0.15 mm to 0.2 mm, and it is also a rectangular plate-like structure. The thickness of the surface acoustic wave device 1 is approximately 0.4 mm to 0.6 mm. In some embodiments, the surface acoustic wave device 1 presents a hexahedron structure, which is composed of two rectangular surfaces and four side surfaces in the thickness direction.

[0034] The cross-sectional structure of the surface acoustic wave device 1 is as shown in Figure 2 and Figure 3 . In the figure, the symbol 3 represents the device chip, the symbol 3a represents its functional surface, the symbol 3b represents the non-functional surface opposite to the functional surface 3a, and the symbol 7a represents the resonator.

[0035] A protruding electrode 10 (bump) is provided between the device chip 3 and the package substrate 2 for electrically connecting the wiring 8 on the device chip 3, and thus a gap 5 is formed between the protruding electrodes 10 in this part.

[0036] In the package substrate 2, external connection terminals 2d for connecting to a main board (not shown) are formed on the other surface 2c opposite to the one surface 2a on the mounting side of the device chip 3 to connect the surface acoustic wave device 1.

[0037] As described above, in a state where the device chip 3 is mounted on the one surface 2a of the package substrate 2, a sealing portion 4 is formed on the one surface 2a of the package substrate 2. The sealing portion 4 is made of an insulating resin.

[0038] The sealing portion 4 is usually formed by coating the resin with a predetermined thickness on the mounting side of the assembly substrate 13 (see Figure 6 ) after mounting the device chip 3 on the assembly substrate 13 serving as the package substrate 2 using the protruding electrode 10, and then hardening the resin by heating it to a specified temperature.

[0039] Alternatively, the sealing portion 4 is formed by laminating a sheet of a predetermined thickness made of the resin on the mounting side of the collective substrate 13 after mounting the device chip 3 to the collective substrate 13 serving as the package substrate 2 by using the protruding electrode 10, then heating the sheet to a predetermined temperature to temporarily melt it, and then hardening it.

[0040] The sealing portion 4 thus formed includes a first portion 4a covering the non-functional surface 3b of the device chip 3, immediately covering the thickness side surface 3c of the device chip 3 between the functional surface 3a and the non-functional surface 3b, and extending to a second portion 4b on one surface 2a of the package substrate 2. By the sealing portion 4 thus formed, an internal space 6 (also referred to as a hollow structure portion or an air cavity) is formed between the functional surface 3a of the device chip 3 and one surface 2a of the package substrate 2.

[0041] That is to say, the sealing portion 4 hermetically seals the gap 5 around the entire periphery 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.

[0042] During the manufacturing process of the elastic wave device 1, the sealing portion 4 is formed after the subsequent column portion 2e is formed. The column portion 2e is built into the sealing portion 4, the entire surface of the column portion 2e is covered by the sealing portion 4, and the column portion 2e and the sealing portion 4 are tightly combined in this state to form an inseparable whole.

[0043] Thus, the collective substrate 13 after the device chip 3 is mounted and the sealing portion 4 is formed is divided into regions for each elastic wave device 1 by a cutting process, thereby generating a plurality of elastic wave devices 1.

[0044] On the portion of the device chip 3 where the functional surface 3a faces the internal space 6, a functional element 7 including an IDT electrode 7b (see Figure 4 ) is provided. In the illustrated example, it is a resonator 7a.

[0045] The device chip 3 has a function of transmitting elastic waves. Typically, the device chip 3 is made of a piezoelectric body such as lithium tantalate or lithium niobate. In addition, the device chip 3 can also be formed by laminating these piezoelectric bodies on a support such as sapphire, silicon, alumina, spinel, quartz, or glass.

[0046] Figure 4Shows an example of the resonator 7a as a SAW filter. The resonator 7a has an IDT electrode 7b and reflectors 7c formed on both sides of the IDT electrode 7b. The IDT electrode 7b is composed of electrode pairs, each electrode pair being formed by arranging a plurality of electrode fingers 7d in parallel. The length direction of these electrode fingers 7d intersects the propagation direction x of the elastic wave and is connected at one end by a bus bar 7e. The reflector 7c is formed by arranging a plurality of electrode fingers 7f in parallel. The length direction of these electrode fingers 7f intersects the propagation direction x of the elastic wave and is connected at both ends by a bus bar 7g.

[0047] This resonator 7a is generally composed of a conductive metal film formed by lithography and etching.

[0048] In the illustrated example, a plurality of such resonators 7a are formed on a device chip 3.

[0049] Figure 5 Shows a conceptual example of the circuit 11 provided on a device chip 3. The symbol 7aa represents the resonator 7a connected in series between the input and output ports 9, the symbol 7ab represents the resonator 7a connected in parallel between the input and output ports 9, the symbol 12 represents the ground, and the symbol 8 represents the wiring. The number and arrangement of the resonators 7a can be adjusted as needed. That is, Figure 5 the circuit 11 in

[0050] In this embodiment, as shown in Figure 2 and Figure 3 a plurality of metal column parts 2e protruding from the one surface 2a of the package substrate 2 are built in the second part 4b of the sealing part 4.

[0051] The column part 2e is typically preferably composed of a metal with high thermal conductivity such as copper or a copper alloy.

[0052] The base of the column part 2e is fixed on the one surface 2a of the package substrate 2 and protrudes in a direction perpendicular to the surface 2a.

[0053] In the illustrated example, the base 2ea of the column part 2e is formed by the end of the internal wiring 2ba in the package substrate 2 on the one surface 2a of the package substrate 2. In the illustrated example, the internal wiring 2ba is connected to the external connection terminal 2d on the other surface 2c side of the package substrate 2.

[0054] The column part 2e is provided at a position between the outer edge of the package substrate 2 and the side surface 3c of the device chip 3. There is a gap between the column part 2e and the side surface 3c of the device chip 3, and there is also a gap between the column part 2e and the outer edge of the package substrate 2. When observing the elastic wave device 1 in a direction perpendicular to the one surface 2a of the package substrate 2, in the direction y around the device chip 3 (see Figure 1), intervals are also formed between adjacent column portions 2e.

[0055] In the illustrated example, the column portions 2e are built into the second part 4b, and three column portions are built into each of the four side portions 1a of the elastic wave device 1 respectively.

[0056] However, the number of the column portions 2e built into the second part 4b, the intervals between two adjacent column portions 2e, the formation positions and arrangements of the column portions 2e, etc. can be appropriately changed as needed.

[0057] The height of the column portion 2e is greater than the distance between the functional surface 3a of the device chip 3 and one surface 2a of the package substrate 2.

[0058] The typical size range of the column portion 2e is a height of 50 - 200 μm and a diameter of 30 - 80 μm.

[0059] In the illustrated example, the column portion 2e has a columnar structure, has a base portion 2ea and a protruding end portion 2eb opposite to the base portion 2ea, and the protruding end portion 2eb is positioned at a height level between the functional surface 3a and the non-functional surface 3b of the device chip 3.

[0060] In the illustrated example, the cross-section of the column portion 2e is substantially circular at each position in its height direction. However, the cross-sectional shape of the column portion 2e can also be appropriately modified to other shapes such as polygons as needed.

[0061] In addition, the area of contact between the column portion 2e and the sealing portion 4 is more than three times the area of contact between the column portion 2e and the package substrate 2.

[0062] That is to say, the surface area of the column portion 2e from the base portion 2ea to the protruding end portion 2eb is more than three times the area of contact between the base portion 2ea of the column portion 2e and one surface 2a of the package substrate 2.

[0063] In addition, in the illustrated example, the column portion 2e is preferably electrically connected to the ground pattern formed on the package substrate 2. In the illustrated example, the base portion 2ea of the column portion 2e serves as an end portion, and the internal wiring 2ba of the package substrate 2 becomes all or part of the ground pattern and is connected to the ground pattern. In this way, the heat transferred to the column portion 2e can be effectively dissipated to the outside by using the ground pattern that is usually vertically arranged and widened in the signal transmission direction.

[0064] Figures 1 to 5 The elastic wave device 1 in the first example shown can be reasonably and appropriately formed by the following process: Step 1: On the collective substrate 13 serving as the package substrate 2, the device chip 3 is mounted in the area of each elastic wave device 1 in the above-mentioned manner.

[0065] Step 2: In each region, form a required number of column portions 2e on the side of the installed device chip 3 (see Figure 6 ).

[0066] Specifically, first, form a photoresist layer 14 on the assembly substrate 13.

[0067] Next, form holes 15 having a complementary shape to the column portions 2e in the photoresist layer 14. In the illustrated example, the holes 15 open on the surface of the photoresist layer 14, and the bottom of the holes 15 is positioned at the end of the internal wiring 2ba. The holes 15 can generally be formed by photolithography and etching, or by laser processing (see Figure 6 Figure (a)).

[0068] Next, fill the holes 15 with the metal constituting the column portions 2e by a hole filling plating process, and fill the holes 15 with the metal to form the column portions 2e (see Figure 6 Figure (b)). Thereafter, remove the photoresist layer 14 using a chemical solution ( Figure 6 Figure (c)).

[0069] Step 3: On one surface of the assembly substrate 13 on which the column portions 2e are formed, form the sealing portion 4 in the above-described manner so that the column portions 2e are built in the sealing portion 4.

[0070] Step 4: Divide the assembly substrate 13 on which the sealing portion 4 is formed into each region by cutting.

[0071] Since the surface acoustic wave device 1 in the present embodiment has the above structure, through the column portions 2e, while ensuring a high mechanical integrity between the sealing portion 4 and the package substrate 2, the heat generated by the device chip 3 can be efficiently conducted to the package substrate 2 and dissipated to the outside.

[0072] Figure 7 A second example is shown in which all or part of the surface of the column portions 2e included in the surface acoustic wave device 1 is processed into a rough surface 2ec. In this way, since the contact area between the column portions 2e and the sealing portion 4 increases, the mechanical integrity between the sealing portion 4 and the package substrate 2 can be further improved. The surface of the column portions 2e can be processed into a rough surface 2ec by wet etching or the like.

[0073] In addition, the other structures of the second example are substantially the same as those of the first example, and thus the related descriptions are omitted.

[0074] Figure 8FIG. 0 shows a third example in which the thickness of the protruding end portion 2eb of the column portion 2e in the elastic wave device 1 gradually increases. In this way, due to the shape of the column portion 2e, it is possible to better resist the force in the direction of separating the package substrate 2 from the sealing portion 4, thereby further improving the mechanical integrity between the sealing portion 4 and the package substrate 2.

[0075] The method of forming the column portion 2e into this shape is on the collective substrate 13 described in the process of the first example, as Figure 9 shown in (a), a hole 15 having a shape complementary to the column portion 2e is formed in the photoresist layer 14. Then, as Figure 9 shown in (b), the metal constituting the column portion 2e is filled into the hole 15 by a filling hole plating process, and the hole 15 is filled with this metal to form the column portion 2e. Subsequently, as Figure 9 shown in (c), the photoresist layer 14 is removed by a chemical solution, and finally the column portion 2e is formed.

[0076] In addition, the other structures of the third example are basically the same as those of the first example, so the related descriptions are omitted.

[0077] Figure 10 FIG. 16 shows a fourth example in which the protruding end portion 2eb side of the column portion 2e in the elastic wave device 1 is processed into a head shape. In this example, the side opposite to the base portion 2ea side of the column portion 2e has a surrounding stepped surface 2ed facing the base portion 2ea side, and the portion above the surrounding stepped surface 2ed is thicker than the portion below it, presenting a head shape. With this design, the shape of the column portion 2e can better resist the force in the direction of separating the package substrate 2 from the sealing portion 4, thereby further improving the mechanical integrity between the sealing portion 4 and the package substrate 2.

[0078] The method of forming the column portion 2e into this shape is on the collective substrate 13 described in the process of the first example, as Figure 11 shown in (a), a hole 15a having a shape complementary to the shape below the protruding end portion 2eb of the column portion 2e is formed in the first photoresist layer 14a. Then, as Figure 9 shown in (b), the hole 15a is filled with metal by a filling hole plating process to form the portion below the protruding end portion 2eb of the column portion 2e, and the hole 15a is filled with metal to form the portion below the protruding end portion 2eb of the column portion 2e. Then, as Figure 11 shown in (c), a second photoresist layer 14b is formed on the first photoresist layer 14a, and a hole 15b having a shape complementary to the protruding end portion 2eb side of the column portion 2e is formed in the second photoresist layer 14b. Then, as Figure 11 shown in (d), the hole 15b is filled with metal by a filling hole plating process to form the portion of the protruding end portion 2eb side of the column portion 2e, and the hole 15b is filled with metal. After that, as Figure 11As shown in (e), the first photoresist layer 14a and the second photoresist layer 14b are removed by a chemical solution, thereby forming the column portion 2e.

[0079] In addition, the other structures of the fourth example are substantially the same as those of the first example, and thus the related descriptions are omitted.

[0080] Of course, the present invention is not limited to the above-described embodiments, but includes all embodiments capable of achieving the object of the present invention.

Claims

1. An elastic wave device, characterized in that include: Package substrate; A device chip is mounted on one side of the packaging substrate, and has a functional surface and a non-functional surface facing each other, wherein the functional surface faces the packaging substrate, and a functional element including an IDT electrode is disposed on the functional surface; A sealing portion, comprising a first portion and a second portion, wherein the first portion covers the non-functional surface of the device chip, and the second portion extends from the first portion, covers the side surface between the functional surface and the non-functional surface of the device chip in the thickness direction, until reaching one side of the packaging substrate, thereby forming an internal space between the functional surface of the device chip and one side of the packaging substrate; A plurality of metal pillars are provided on the package substrate, protrude from the one surface, and are built into the second portion of the sealing portion.

2. The elastic wave device according to claim 1, wherein: An area where the pillar portion contacts the sealing portion is three times or more of an area where the pillar portion contacts the packaging substrate.

3. The elastic wave device according to claim 1, wherein: The entire or a part of the surface of the column part is a rough surface.

4. The elastic wave device according to claim 1, wherein: The column portion gradually becomes thicker near the protruding end thereof.

5. The elastic wave device according to claim 1, wherein: The protruding end of the column portion is formed into a head shape.

6. The elastic wave device according to claim 1, wherein: The pillar portion is electrically connected to a ground pattern formed on the package substrate.

7. The elastic wave device according to claim 1, characterized in that: When the elastic wave device is observed from a direction perpendicular to one surface of the package substrate, the plurality of pillars are arranged around the device chip in an interval manner, and intervals are maintained between adjacent pillars.

8. The elastic wave device according to claim 1, wherein: The height of the column portion is greater than the distance between the functional surface of the device chip and the surface of the packaging substrate.

9. The elastic wave device according to claim 1, wherein: A gap is provided between the column portion and the side surface of the device chip, and a gap is also provided between the column portion and the outer edge of the packaging substrate.

10. The elastic wave device according to claim 1, wherein: The column portion has a columnar structure and has a base portion and a protruding end portion opposite to the base portion, and the protruding end portion is positioned at a height level between the functional surface and the non-functional surface of the device chip.

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