Acoustic wave device

Abstract

To rationally provide an acoustic wave device with a form, which stabilizes suction by a suction nozzle, while including additional functions.SOLUTION: Regarding at least one of a plurality of device chips 3, at least a part of functional elements is defined as an IDT electrode 7c. An interval Sa is formed between the device chips 3 adjacent to each other, and an encapsulation resin film 5 of the device chip 3 is formed while including a space A formed from the interval Sa on a package substrate 2. At least at a central side 2d of the package substrate 2, the space A is filled by a conductive filler 9, and the conductive filler 9 and an electrode of a potential of a ground 8 formed on one face 2a of the package substrate 2 are connected via a penetration part 5a formed in the encapsulation resin film 5. The acoustic wave device comprises a conductive metal film 11 covering the encapsulation resin film 5 and the conductive filler 9 at the side of the one face 2a of the package substrate 2.SELECTED DRAWING: Figure 1

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 used as a frequency filter in a mobile communication device or the like includes a package substrate 100 on which a plurality of device chips 101 are mounted with a gap S between adjacent device chips 101 (see FIG. 12).

[0003] 12, reference numeral 100 denotes a package substrate, reference numeral 101 denotes a device chip, reference numeral 102 denotes bumps, reference numeral 103 denotes electrode pads formed on the package substrate side, and reference numeral 104 denotes external electrode pads for connecting the acoustic wave device to a motherboard. A gap 105 equal to the thickness of the bumps 102 and electrode pads 103 is formed between the device chip 101 and the package substrate 100. A sealing resin film 106 is formed on one surface of the package substrate 100 to hermetically seal the gap 105. At the interval S between adjacent device chips 101, the sealing resin film 106 is in close contact with one surface of the package substrate 100, and a space 107 is formed between the adjacent device chips 101.

[0004] When mounting such an acoustic wave device on a motherboard, it is common to transfer the acoustic wave device by suctioning it with a suction nozzle of a mounter, but the void 107 described above makes this suction unstable. Summary of the Invention [Problem to be solved by the invention]

[0005] The main problem that the present invention is to solve is to rationally provide this type of acoustic wave device with a configuration that stabilizes suction by a suction nozzle while providing additional functions. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides an acoustic wave device comprising a plurality of device chips mounted on a package substrate with their main surfaces, each having a functional element on one surface of the package substrate, facing each other, and at least one of the plurality of device chips having at least a part of the functional element as an IDT electrode, a gap is formed between the adjacent device chips, and a sealing resin film for the device chips is formed on the one surface side of the package substrate, including in the space formed by the gap; the space at least on the central side of the package substrate is filled with a conductive filler, and the conductive filler and a ground potential electrode formed on the one surface of the package substrate are connected to each other through a penetration portion formed in the sealing resin film, Moreover, the package substrate is provided with a conductive metal film that covers the sealing resin film and the conductive filler on the one surface side thereof.

[0007] In one aspect of the present invention, the thickness of the sealing resin film on the back surface opposite to the main surface of the device chip is made smaller than the thickness of the sealing resin film on one surface of the package substrate.

[0008] In one aspect of the present invention, the conductive filler is filled into the space to a position where it is flush with the sealing resin film that covers the back surface opposite the main surface of the device chip. [Effects of the Invention]

[0009] According to this invention, this type of acoustic wave device can be rationally provided with a configuration that stabilizes suction by a suction nozzle using the conductive filler, while also providing the additional function of connecting the conductive metal film to an electrode of ground potential formed on a package substrate using the conductive resin material. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an acoustic wave device (first example) according to an embodiment of the present invention, taken along line II in FIG. [Figure 2] FIG. 2 is a plan view showing the first example as viewed from above in FIG. [Figure 3] FIG. 3 is a configuration diagram showing an example of a resonator formed on the device chip of the first example. [Figure 4] FIG. 4 is a configuration diagram showing an example of a circuit formed on the device chip of the first example. [Figure 5] FIG. 5 is a cross-sectional view showing the first example in which a suction nozzle is attached to the suction nozzle. [Figure 6] FIG. 6 is a plan view showing one step in the manufacturing process of the first example, illustrating the state of a part of an aggregate substrate on which device chips are mounted. [Figure 7] FIG. 7 is a cross-sectional view of a main part showing one of the steps in the manufacturing process of the first example. [Figure 8] FIG. 8 is a cross-sectional view of a main part showing one of the steps in the manufacturing process of the first example. [Figure 9] FIG. 9 is a cross-sectional view of a main part showing one of the steps in the manufacturing process of the first example. [Figure 10] FIG. 10 is a plan view of an acoustic wave device (second example) according to an embodiment of the present invention. [Figure 11] FIG. 11 is a plan view of an acoustic wave device (third example) according to an embodiment of the present invention. [Figure 12] FIG. 12 is a cross-sectional view showing the configuration of a conventional acoustic wave device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Exemplary embodiments of the present invention will now be described with reference to Figures 1 to 11. An acoustic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices and the like.

[0012] The acoustic wave device 1 includes a plurality of device chips 3 mounted on a package substrate 2 with their main surfaces 3a, each of which has functional elements (such as a circuit that becomes a SAW filter, a circuit that becomes a SAW resonator, an element that becomes a resistor, an element that becomes an inductor, an element that becomes a capacitance, etc.) facing each other on one surface 2a of the package substrate 2.

[0013] Additionally, in the acoustic wave device 1, at least one of the plurality of device chips 3 has at least a part of the functional element as an IDT electrode 7c.

[0014] Typically, the device chip 3 is configured as a rectangular plate with a side length of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm. The package substrate 2 is also configured as a rectangular plate with a side length of 1 to 3 mm and a thickness of 0.15 to 0.2 mm. The acoustic wave device 1 has a thickness of approximately 0.4 to 0.5 mm.

[0015] Its cross-sectional structure is shown in Figure 1. In the figure, reference numeral 3 denotes a device chip, reference numeral 2 denotes a package substrate, reference numeral 4 denotes a bump, reference numeral 2b denotes an electrode pad on the package substrate 2 side, and reference numeral 2c denotes an external electrode pad for connecting the acoustic wave device 1 to a motherboard. The device chip 3 and package substrate 2 are electrically connected by fixing the bumps 4 to the electrode pads 2b. A gap is formed between one surface 2a of the package substrate 2 (the surface on which the device chip 3 is mounted) and the main surface 3a of the device chip 3 facing this surface 2a, the gap being equal to the thickness of the bumps 4 and electrode pads 2b. By forming the sealing resin film 5 described below after the device chip 3 is mounted on one surface 2a of the package substrate 2 in this manner, the gap is hermetically sealed, and a hollow structure 6 (internal space or air cavity) is formed between the main surface 3a of the device chip 3 and the one surface 2a of the package substrate 2.

[0016] The device chip 3, in which at least a part of the functional element is an IDT electrode 7c, is provided with a circuit that serves as a SAW filter or a circuit that serves as a SAW resonator on the part of the main surface 3a facing the hollow structure portion 6.

[0017] The device chip 3 has a function of propagating elastic waves. Typically, lithium tantalate or lithium niobate is used for the device chip 3, and the device chip 3 may also be configured by laminating sapphire, silicon, alumina, spinel, quartz, glass, or the like on these.

[0018] FIG. 3 shows an example of a circuit that serves as a SAW resonator, i.e., a resonator 7. The resonator 7 has an IDT electrode 7c and a reflector 7d formed so as to sandwich the IDT electrode 7c. The IDT electrode 7c is composed of an electrode pair, and each electrode pair has multiple electrode fingers 7e arranged in parallel so that their length direction intersects with the propagation direction x of the acoustic wave, and each electrode pair has one end connected to the other by a busbar 7f. The reflector 7d has multiple electrode fingers 7e arranged in parallel so that their length direction intersects with the propagation direction x of the acoustic wave, and each electrode finger 7e has one end connected to the other by a busbar 7f. Such a resonator 7 is typically made of a conductive metal film formed by photolithography. Furthermore, a plurality of such resonators 7 may be formed on one device chip 3.

[0019] Figure 4 shows the concept of an example of a circuit provided on one device chip 3. Reference numeral 7a denotes a resonator connected in series between the input and output ports, reference numeral 7b denotes a resonator connected in parallel between the input and output ports, and reference numeral 8 denotes a ground. In other words, a ladder-type filter is configured by the circuit in Figure 4.

[0020] A gap Sa is formed between adjacent device chips 3 constituting the acoustic wave device 1. In the illustrated example, four device chips 3 of the same size and shape are mounted on the package substrate 2 such that a gap Sb is formed between the edge 3d of each device chip 3 and the edge 2f of the package substrate 2, and the gap Sa is also formed between the facing edges 3d of adjacent device chips 3. In the illustrated example, when the package substrate 2 is viewed from a direction perpendicular to the one surface 2a, a cross-shaped space A is formed by the four device chips 3. In the illustrated example, the space A is groove-shaped, with the side surfaces 3c of the device chips 3 as groove walls and the one surface 2a of the package substrate 2 as groove bottom, and the groove width is constant at any position. The width of the gap Sa is preferably 25 μm to 100 μm.

[0021] Furthermore, a sealing resin film 5 for the device chip 3 is formed on the one surface 2a of the package substrate 2, including the inside of the space A. The sealing resin film 5 is made of an insulating material, and typically has thermosetting properties. In the illustrated example, after the device chip 3 is mounted on the package substrate 2 as described above, the sealing resin film 5 is placed on the one surface 2a of the package substrate 2 and heated, thereby adhering the sealing resin film 5 to the one surface 2a of the package substrate 2, the back surface 3b facing the main surface 3a of the device chip 3, and the side surface 3c of the device chip 3 along the thickness direction, thereby forming the hollow structure 6.

[0022] In the illustrated example, in order to reduce the height of the acoustic wave device 1, the sealing resin film 5 covering the back surface 3b of the device chip 3 is processed to be thinner after the bonding. As a result, the thickness of the sealing resin film 5 is smaller than the thickness of the sealing resin film 5 on the one surface 2a of the package substrate 2 and the thickness of the sealing resin film 5 on the side surface 3c of the device chip 3.

[0023] The thickness of the sealing resin film 5 disposed on the back surface 3 b of the device chip 3 is preferably one-fifth to one-third of the thickness of the sealing resin film 5 on one surface 2 a of the package substrate 2 .

[0024] Furthermore, the space A is filled with a conductive filler 9 at least on the central side 2d of the package substrate 2. In the illustrated example, the space A between adjacent device chips 3 is filled with the conductive filler 9 up to a position a certain distance from the center 2e between the center 2e (see FIG. 2) of the one surface 2a of the package substrate 2 and the edge portion 2f of the package substrate 2, with the conductive filler 9 defining a filled portion 9a between this position and the center 2e and a non-filled portion 10 between this position and the edge portion 2f. In the illustrated example, four non-filled portions 10 are formed to surround one filled portion 9a. Although not illustrated, the entire space A may be filled with the conductive filler 9.

[0025] As the conductive filler 9, it is preferable to use a conductive adhesive such as silver paste, or a conductive resin.

[0026] In this embodiment, the filled portion 9a of the conductive filler 9 and the ground potential electrode 2g formed on the one surface 2a of the package substrate 2 are connected through the through portion 5a formed in the sealing resin film 5. In the illustrated example, the ground potential electrode 2g is formed on the center 2e side of the package substrate 2. In the illustrated example, the through portion 5a is formed on this electrode 2g by processing after the sealing resin film 5 is adhered. When the conductive filler 9 is filled, the conductive filler 9 penetrates into the through portion 5a, so that the electrode 2g and the conductive filler 9 come into contact with each other. The through portion 5a is formed in the sealing resin film 5 covering the one surface 2a of the package substrate 2 within the gap Sa. Typically, the through portion 5a is formed in the shape of a hole having a diameter of 5 μm to 20 μm or a slit having a width of 5 μm to 20 μm. As a typical configuration example, when the distance between adjacent device chips 3 in Figure 2 is approximately 80 μm, the distance Sc between the sealing resin film 5 covering the side surface 3c of one device chip 3 and the sealing resin film 5 covering the side surface 3c of the other device chip 3 is approximately 40 μm, and the width of the through portion 5a is 5 μm to 20 μm.

[0027] In this embodiment, the acoustic wave device 1 also includes a conductive metal film 11 that covers the sealing resin film 5 and the conductive filler 9 on the one surface 2a of the package substrate 2. In the illustrated example, processing after the sealing resin film 5 is adhered removes the sealing resin film 5 on the edge 2f side of the package substrate 2 from a portion 2h of the circuit pattern that is connected to the electrode pads 2b on the package substrate 2 that are connected to the device chip 3 via bumps 4 and that is positioned outside the device chip 3. At the same time, the conductive metal film 11 also covers this portion 2h of the circuit pattern.

[0028] As a result, in this embodiment, firstly, the electrode 2g at the ground potential 8 of the package substrate 2 and the circuit formed on the device chip 3 can be rationally connected via the conductive metal film 11 and the conductive filler 9. This allows the acoustic wave device 1 to have an electromagnetic shielding structure. In addition, the conductive metal film 11 improves the heat dissipation of the acoustic wave device 1. Secondly, while multiple device chips 3 are provided with a gap Sa between adjacent device chips 3, the conductive filler 9 can be used to rationally form a continuous surface 13 on the acoustic wave device 1 at the center side 2d of the package substrate 2 so that the continuous surface 13 can be appropriately adsorbed by an adsorption nozzle 12 of a mounter (mounting machine) and spans the space between adjacent device chips 3.

[0029] In this embodiment, the conductive filler 9 is filled into the space A up to a position where it is flush with the sealing resin film 5 that covers the back surface 3b opposite the main surface 3a of the device chip 3. As a result, in the filled portion 9a, the continuous surface 13 is a flat surface that is substantially parallel to one surface 2a of the package substrate 2, and the suction nozzle 12 can be in close contact with the continuous surface 13 without any gaps.

[0030] 10, the acoustic wave device 1 may be configured such that two device chips 3 are adjacent to each other with a gap Sa therebetween on the central side 2d of the package substrate 2. Alternatively, as shown in FIG. 11, the acoustic wave device 1 may be configured such that three device chips 3 are adjacent to each other with a gap Sa therebetween on the central side 2d of the package substrate 2.

[0031] The acoustic wave device 1 described above can be manufactured appropriately and efficiently as follows.

[0032] 6 to 9 show the main steps of manufacturing the acoustic wave device 1 according to this embodiment. 7 to 9 are cross-sectional views taken along line II in FIG.

[0033] First, a plurality of device chips 3 are mounted in each region 16a constituting one acoustic wave device 1 on an aggregate substrate 16 that will become the package substrate 2, with a gap Sa formed between adjacent device chips 3 (step 1 / FIG. 6). The aggregate substrate 16 typically has a side length of 90 to 100 mm, and a maximum of approximately 1200 to 3000 package substrates 2, i.e., acoustic wave devices 1, can be produced from one aggregate substrate 16. FIG. 6 shows a portion of the aggregate substrate 16, and reference numeral 16b in the figure denotes a dicing line.

[0034] Next, in each of the regions 16a, a film that will become the sealing resin film 5 is placed on one surface 2a of the package substrate 2 (a part of the assembly substrate 16 before dicing, hereinafter simply referred to as the package substrate 2), and heated to adhere the sealing resin film 5 to one surface 2a of the package substrate 2 within the interval Sa except for the area where the device chip 3 is mounted, including the one surface 2a of the package substrate 2, the back surface 3b of the device chip 3, and the side surface 3c of the device chip 3 (step 2 / FIG. 7).

[0035] Next, in each of the regions 16a, a processing step is performed to form a through-hole 5a in the sealing resin film 5 that is adhered to one surface 2a of the package substrate 2 on the central side 2d of the package substrate 2 and within the space A formed by the spacing Sa between the multiple device chips 3 (step 3 / Figure 8).

[0036] In the illustrated example, together with step 3, or prior to step 3, or after step 3, a process is performed to thin the sealing resin film 5 adhered to the back surface 3b of the device chip 3 (Figure 8).

[0037] In the illustrated example, together with step 3, or prior to step 3, or after step 3, a process is performed to remove the sealing resin film 5 adhered to a portion 2h of the electrode pattern on one surface 2a of the package substrate 2 formed between the edge 3d of the device chip 3 and the edge 2f of the package substrate 2 (Figure 8).

[0038] The processing in step 3 is preferably performed by laser processing.

[0039] Next, in each of the regions 16a, the conductive filler 9 is filled into the space A between adjacent device chips 3 at least on the central side 2d of the package substrate 2 (step 4 / FIG. 9). The illustrated example shows an example in which the conductive filler 9 is filled into the space A by a screen printing technique. In FIG. 9, reference numeral 14 denotes a screen, reference numeral 14a denotes a passage for the conductive filler 9 formed on the screen, and reference numeral 15 denotes a squeegee that pushes the conductive filler 9 into the gap Sa from this passage. Although not shown in the figure, the conductive filler 9 may also be filled into the space A by a dispenser.

[0040] Finally, in each of the regions 16a, a conductive metal film 11 is formed on the surface 2a of the package substrate 2 to cover the sealing resin film 5 and the conductive filler 9 (step 5 / FIG. 1). The conductive metal film 11 is preferably formed by electroless plating or electrolytic plating.

[0041] 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]

[0042] 1. Acoustic wave devices 2 Package substrate 2a one side 2b Electrode pad 2c External electrode pad 2d Center side 2e center 2F edge 2g electrode (ground potential) 2h section (part of the circuit pattern) 3 Device chip 3a Main surface 3b Back 3c side 3d edges 4. Bump 5 Sealing resin film 5a Penetration 6 Hollow structure 7, 7a, 7b resonator 7c IDT electrode 7d reflector 7e electrode finger 7F bus bar 8 grand 9. Conductive filler 9a Filling section 10 Unfilled area 11 Conductive metal film 12 Suction nozzle 13 Continuous Surfaces 14 screens 14a Passage section 15 Squeegee 16 Collective board 16a area 16b dicing line A Space Sa, Sb, Sc intervals

Claims

1. An acoustic wave device comprising: a plurality of device chips mounted on a package substrate with their main surfaces, each having a functional element on one surface thereof, facing each other; and at least one of the plurality of device chips having an IDT electrode as at least a part of the functional element, a gap is formed between the adjacent device chips, and a sealing resin film for the device chips is formed on the one surface side of the package substrate, including in the space formed by the gap; the space at least on the central side of the package substrate is filled with a conductive filler, and the conductive filler and a ground potential electrode formed on the one surface of the package substrate are connected to each other through a penetration portion formed in the sealing resin film, Moreover, the acoustic wave device further comprises a conductive metal film that covers the sealing resin film and the conductive filler on the one surface side of the package substrate.

2. 2. The acoustic wave device according to claim 1, wherein the thickness of the sealing resin film on a back surface of the device chip opposite the main surface is smaller than the thickness of the sealing resin film on one surface of the package substrate.

3. 2. The acoustic wave device according to claim 1, wherein the conductive filler is filled into the space to a position flush with the sealing resin film covering a back surface of the device chip opposite the main surface.

Images