Module including elastic wave device

Abstract

To appropriately provide a structure that can efficiently clean residue of flux, for example, after implementation of a device chip to a module.SOLUTION: A module substrate 2 includes a solder resist layer 2b, which covers a region on a mount surface 2a that is required to be covered. Under one surface 4a of a device chip 4, a blank part 2ba in the solder resist layer 2b where the solder resist layer 2b is absent is formed. In the solder resist layer 2b in the vicinity of the blank part 2ba, two or more passages 14 are formed, each including a first part 14a existing under the one surface 4a of the device chip 4 continuing to the blank part 2ba and a second part 14b not existing under the one surface 4a of the device chip 4 on the outside of a side surface 4b corresponding to the thickness of the device chip 4.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an improvement of a module in which some of two or more electronic devices mounted on a module substrate are device chips that function as elastic wave devices.

Background Art

[0002] There is a module in which some of two or more electronic devices mounted on a module substrate are device chips that function as elastic wave devices. The main part thereof is shown in FIG. 10. The device chip 100 includes a functional element 101 including an IDT electrode on one surface thereof and a bump 102 composed of solder connected to the functional element 101 via wiring. On the other hand, a region to be coated on the mounting surface of the module substrate 200 for the electronic device is covered with a solder resist layer 300. The region on the mounting surface where the device chip 100 is mounted is a blank portion 301 without the solder resist layer 300. Bump pads 201 for the bumps 102 are arranged on the mounting surface in the blank portion 301. The device chip 100 is mounted on the module substrate 200 in a state where a gap corresponding to the protruding dimension of the bump 102 is opened between the one surface and the mounting surface located in the blank portion 301 by fixing the bump 102 to the bump pad 201 by reflow processing or the like. On the mounting surface of the device chip 100, a sealing resin 400 is formed so that the gap serves as an internal space. The functional element 101 of the device chip 100 is located in this internal space, whereby the function as an elastic wave device is exhibited.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, it is necessary to clean the blank portion 301, such as flux residue, after mounting the device chip 100. Therefore, there is a demand for appropriately providing this type of module with a structure that can efficiently perform such cleaning. Here, as shown in FIG. 10, when the blank portion 301 is formed such that the opening edge 301a of the blank portion 301 is positioned closer to the center side of the device chip 100 than the outer edge 103 on one surface of the device chip 100, as shown in FIG. 11, when the blank portion 301 is formed such that the opening edge 301a of the blank portion 301 is positioned outside the outer edge 103 on one surface of the device chip 100, the distance L between the outer edge 103 and the opening edge 301a can be increased. Therefore, the structure shown in FIG. 11 is more suitable for improving the cleaning efficiency. However, in this type of module, in order to surely form the internal space, a method of covering the device chip 100 with the film 500 together with the module substrate 200 before forming the sealing resin 400 is often adopted. Typically, such a film 500 is overlapped on the device chip 100 in a vacuum atmosphere after mounting the device chip 100, and then the device chip 100 and the module substrate 200 are brought into close contact by increasing the air pressure in the space above the film 500. However, if the structure shown in FIG. 11 is simply adopted, when the film 500 is brought into close contact in this way, it is assumed that the amount of the film 500 drawn into the blank portion 301 increases and breakage occurs at the drawn-in portion.

[0004] The main problem to be solved by the present invention is to appropriately provide this type of module with a structure that can efficiently perform cleaning of the blank portion, such as flux residue, after mounting the device chip.

Means for Solving the Problems

[0005] In order to achieve the above object, in the present invention, a module including an elastic wave device is A module in which two or more electronic devices are mounted on a module substrate, and a part of the two or more electronic devices is a device chip that functions as an elastic wave device. The device chip includes a functional element including an IDT electrode on one surface thereof and a bump composed of solder connected to the functional element, and is mounted on the module substrate so as to create a gap between the one surface of the device chip and the mounting surface of the module substrate by using the bump. The module substrate has a solder resist layer, and the solder resist layer covers a region to be coated on the mounting surface. Under the one surface of the device chip, a blank portion in the solder resist layer without the solder resist layer is formed. In the vicinity of the blank portion, two or more passages having a first location located under the one surface of the device chip communicating with the blank portion and a second location outside the side surface corresponding to the thickness of the device chip and not located under the one surface of the device chip are formed in the solder resist layer.

[0006] In any position of the outer edge of the one surface of the device chip where the one surface is in contact with the side surface, when the device chip is viewed from a direction perpendicular to the one surface, the outer edge and the opening edge of the blank portion overlap, or the opening edge is located closer to the center of the device chip than the outer edge within a range of 20 to 50 μm. This is one aspect of the embodiment of the present invention.

[0007] Also, making the passage groove-shaped is one aspect of the embodiment of the present invention.

[0008] Also, one aspect of the embodiment of the present invention is that the module including the elastic wave device further includes a film covering the device chip together with the module substrate and a sealing resin formed on the film. In this case, it is one aspect of the present invention that the distance between the one surface of the device chip and the surface of the solder resist layer in the direction orthogonal to the one surface of the device chip is made to be less than 1.5 times the thickness of the film. Further, the passage is formed in a groove shape, and includes a film that covers the device chip together with the module substrate, and a sealing resin formed on the film. Moreover, it is one aspect of the present invention that the groove width of the passage is made to be less than 1.5 times the thickness of the film. In this case further, it is one aspect of the present invention that the groove width of the passage is made to be in the range of 30 to 75 μm.

Advantages of the Invention

[0009] According to the present invention, without unnecessarily widening the distance between the device chip and the solder resist layer constituting the module substrate in the vicinity of the blank portion, a structure capable of efficiently performing cleaning of residues of flux, etc. on the blank portion, which is performed after mounting the device chip, can be appropriately provided to this type of module by the passage.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, typical embodiments of the present invention will be described with reference to FIGS. 1 to 9.

[0012] The module 1 according to this embodiment is a device chip 4 that functions as an elastic wave device 3a for a part of two or more electronic devices 3 mounted on a module substrate 2 (see FIG. 1). Such an elastic wave device 3a is suitable for use as a frequency filter or the like in mobile communication devices and the like. The module 1 is typically used as a PAMiD (Power Amplifier Module integrated Duplexer) module or the like. Examples of the electronic devices 3 other than the device chip 4 that functions as the elastic wave device 3a typically include passive components that function as power amplifiers, low-noise amplifiers, semiconductor devices that function as switches, resistors, capacitors, coils, and the like.

[0013] The device chip 4 has a functional surface on one side 4a where functional elements including IDT electrodes are formed, typically resonators 5. Also, the device chip 4 is provided, on the one side 4a, with a circuit 7 including wiring 6 for connecting the resonators 5 to each other and wiring 6 for enabling connection of the resonators 5 to the outside (see FIG. 8). In FIGS. 3, 4, and 6, the description of the wiring 6 is omitted. Such resonators 5 and wiring 6 are typically composed of a conductive metal film formed by photolithography technology and etching.

[0014] The device chip 4 has a function of propagating elastic waves. Typically, a piezoelectric material such as lithium tantalate or lithium niobate is used for the device chip 4. Also, the device chip 4 may be configured by laminating these piezoelectric materials on a support such as sapphire, silicon, alumina, spinel, quartz, or glass. Typically, the device chip 4 is configured to be a square plate with a side length of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm.

[0015] FIG. 7 shows an example of a resonator 5 formed on one side 4a of the device chip 4. The resonator 5 has an IDT electrode 5a and a reflector 5b formed so as to sandwich the IDT electrode 5a. The IDT electrode 5a consists of electrode pairs, and each electrode pair is formed by connecting a plurality of electrode fingers 5c arranged in parallel so that their length directions cross the propagation direction x of the elastic wave at one end side with a bus bar 5d. The reflector 5b is formed by connecting between the ends of a plurality of electrode fingers 5e arranged in parallel so that their length directions cross the propagation direction x of the elastic wave with a bus bar 5f.

[0016] FIG. 8 shows a conceptual example of a circuit 7 provided on one device chip 4. Reference numeral 50 indicates a resonator 5 connected in series between signal input / output terminals 8, reference numeral 51 indicates a resonator 5 connected in parallel between signal input / output terminals 8, and reference numeral 9 indicates ground, respectively. The number and arrangement of the resonators 5 are changed as required. That is, a ladder-type filter is configured by the circuit 7 in FIG. 8.

[0017] The device chip 4 configured as described above is provided with bumps 10 protruding from the one surface 4a thereof as shown in FIG. 3 on the one surface 4a. The bumps 10 are composed of solder and are typically formed by flux transfer or the like at the corners or edges of the one surface 4a of the device chip 4, and the base thereof is fixed to the wiring 6.

[0018] The module substrate 2 has a mounting surface 2a for mounting the electronic device 3 and supports the electronic device 3 mounted on this mounting surface 2a. Further, the module substrate 2 has a solder resist layer 2b and is configured to cover the area to be coated on the mounting surface 2a by this solder resist layer 2b. Typically, after forming wirings on the module substrate 2 side (not shown) and bump pads 2c (described later) on the mounting surface 2a of the module substrate 2 on the solder resist layer 2b, the solder resist layer 2b is formed on the mounting surface 2a so as to cover the area where the electronic device 3 is mounted and the area other than the area not requiring covering as the area to be coated. Below the one surface 4a of the device chip 4 on the module substrate 2, a blank portion 2ba in the solder resist layer 2b without such a solder resist layer 2b is formed. The mounting surface 2a is exposed in this blank portion 2ba.

[0019] In the illustrated example, as shown in FIG. 2, the device chip 4 has a rectangular plate shape as described above when viewed from a direction orthogonal to the one surface 4a thereof. On the other hand, the blank portion 2ba is configured such that, when the module substrate 2 is viewed from a direction orthogonal to the mounting surface 2a, the opening edge 2bb (the edge where the surface 2bd having the thickness of the solder resist layer 2b facing the blank portion 2ba and the surface 2bc of the solder resist layer 2b around the blank portion 2ba are in contact with each other; see FIGS. 3 and 4) follows the contour of a virtual rectangle.

[0020] In the first example shown in FIGS. 1 to 8, the contour of the opening edge 2bb of the blank portion 2ba is the same as the contour of one surface 4a of the device chip 4, and the area of the blank portion 2ba is made slightly smaller than the area of one surface 4a of the device chip 4. On the other hand, in the second example shown in FIG. 9, the contour of the opening edge 2bb of the blank portion 2ba is the same as the contour of one surface 4a of the device chip 4, and the area of the blank portion 2ba is made equal to the area of one surface 4a of the device chip 4.

[0021] Bump pads 2c for the bumps 10 are formed on the mounting surface 2a within the blank portion 2ba. In the illustrated example, the bumps are formed at the four corners of one surface 4a of the device chip 4, and correspondingly, the bump pads 2c are respectively formed at the four corners of the blank portion 2ba (see FIG. 2).

[0022] The device chip 4 is typically mounted on the module substrate 2 by fixing the protruding ends 10a of the bumps 10 to the bump pads 2c within such a blank portion 2ba, for example, by a reflow process. One surface 4a of the device chip 4 faces the mounting surface 2a of the module substrate 2 exposed in the blank portion 2ba, and a gap 11 corresponding to the protruding amount of the bumps 10 from the one surface 4a and the thickness of the bump pads 2c is formed between the one surface 4a and the mounting surface 2a within the blank portion 2ba. The gap 11 is sealed between the outer edge 4c (to be described later) surrounding the center 4d of the device chip 4 and the surface 2bc of the solder resist layer 2b at any position of the outer edge 4c by a sealing portion 12 formed as described later, and an internal space is formed under one surface 4a of the device chip 4, and the resonator 5 is located within this internal space. The solder resist layer 2b is typically formed to have a thickness in the range of 10 to 30 μm on the mounting surface 2a. However, the dimension 11a of the gap 11 (see FIG. 3) is larger than the thickness of the solder resist layer 2b. A gap L is formed in a direction orthogonal to one surface 4a of the mounted device chip 4 between the periphery of the device chip 4 surrounding the center 4d of the device chip 4, that is, at any position on the outer edge 4c, between one surface 4a of the device chip 4 and the surface 2bc of the solder resist layer 2b.

[0023] In the first example, the opening edge 2bb of the blank portion 2ba is positioned closer to the center 4d of the device chip 4 in the range of 20 to 50 μm than the outer edge 4c of one surface 4a of the device chip 4 that is in contact with the side surface 4b which is the thickness of the device chip 4, at any position on the periphery of the device chip 4 surrounding the center 4d of the device chip 4, that is, at any position on the outer edge 4c. In contrast, in the second example, the outer edge 4c of one surface 4a of the device chip 4 that is in contact with the side surface 4b which is the thickness of the device chip 4 and the opening edge 2bb of the blank portion 2ba overlap each other at any position on the periphery of the device chip 4 surrounding the center 4d of the device chip 4, that is, at any position on the outer edge 4c, when viewed from a direction orthogonal to the one surface. Therefore, in both the first example and the second example, the gap L formed between one surface 4a of the device chip 4 and the surface 2bc of the solder resist layer 2b is constant at any position in the direction around the center 4d of the device chip 4.

[0024] In this embodiment, in order to surely form the internal space, the device chip 4 is covered with a resin film 13 together with the module substrate 2 before forming the encapsulating resin. Such a film 13 has insulation and flexibility. Such film 13 is typically stacked on the device chip 4 in a vacuum atmosphere after the mounting of the device chip 4, and then adhered to the device chip 4 and the module substrate 2 by increasing the air pressure in the space above the film 13. The interval L formed between one surface 4a of the device chip 4 and the surface 2bc of the solder resist layer 2b is set to a dimension such that when the film 13 is adhered in this manner, the amount of the film 13 drawn into the blank portion 2ba increases and no breakage occurs at the drawn portion. The interval L is preferably set to a dimension less than 1.5 times the thickness of the film 13. Specifically, the dimension of such interval L is determined in consideration of the thickness and material of the film 13, etc. The thickness of the film 13 is typically in the range of 20 to 50 μm, and in this case, the dimension of the interval L is preferably set to 30 to 75 μm.

[0025] Also, in this embodiment, a passage 14 having a first location 14a located under the one surface 4a of the device chip 4 and communicating with the blank portion 2ba and a second location 14b located outside the side surface 4b corresponding to the thickness of the device chip 4 and not under the one surface 4a of the device chip 4 is formed in the solder resist layer 2b in the vicinity of the blank portion 2ba. The number, length, width, form, distance between the first location 14a and the second location 14b, etc. of such passage 14 can be changed as needed. In the illustrated example, such passage 14 is formed as a groove-shaped one formed in the solder resist layer 2b and penetrating through the solder resist layer 2b. That is, the bottom of the passage 14 is the mounting surface 2a of the module substrate 2. The length of such passage 14 is typically set such that the total length is 100 μm or more and the length of the portion located under the one surface 4a of the device chip 4 is 20 to 50 μm. Also, in the illustrated example, the width of the passage 14 is substantially equal at any position. When such a passage 14 is in a groove shape, it is preferable that the groove width is less than 1.5 times the thickness of the film 13. The thickness of the film 13 is typically in the range of 20 to 50 μm, and in this case, it is preferable that the groove width of the passage 14 is 30 to 75 μm. Two or more such passages 14 are formed in the solder resist layer 2b so as to change their formation positions. At least one of the two or more passages 14 is formed to be an inlet for a fluid such as a cleaning liquid described later, and at least one of the others of them is formed to be an outlet for the fluid. In the illustrated example, the blank portion 2ba has a form in which its opening edge 2bb follows the contour of the virtual rectangle. In this case, typically, when at least one of the two or more passages 14 is provided at one side portion of the rectangle, at least one of the other of the two or more passages 14 is provided at the side portion of the rectangle facing this side portion. Alternatively, when at least one of the two or more passages 14 is provided at one side portion of the rectangle, at least one of the other of the two or more passages 14 is provided at the side portion of the rectangle adjacent to this side portion. In the illustrated example, the passages 14 are respectively formed at positions in the middle between adjacent corners 2be (see FIG. 2) of the blank portion 2ba. Each passage 14 extends in a direction perpendicular to the opening edge 2bb connecting the adjacent corners 2be of the blank portion 2ba.

[0026] It is necessary to clean the blank portion 2ba, such as residue of flux, after mounting the device chip 4. According to the structure described above, without unnecessarily increasing the distance L between the device chip 4 and the solder resist layer 2b constituting the module substrate 2 in the vicinity of the blank portion 2ba, a structure capable of efficiently performing cleaning of the blank portion 2ba, such as residue of flux, after mounting the device chip 4 on this type of module 1 can be appropriately provided by the passage 14. That is, the passage 14 enlarges the cross-sectional area of the flow path for sending a fluid such as a cleaning liquid used in the cleaning into the blank portion 2ba and the cross-sectional area of the flow path for sending it out of the blank portion 2ba without arbitrarily increasing the interval L and without causing breakage of the film 13.

[0027] After mounting the device chip 4 and other electronic devices 3 as described above, a sealing portion 15 is formed on the mounting surface 2a of the module substrate 2. Such a sealing portion 15 is composed of a resin having insulating properties. Such a sealing portion 15 is typically formed by applying the resin with a predetermined thickness to the mounting side of the electronic device 3 on an assembly substrate (not shown) that becomes the module substrate 2, and then heating the resin to a predetermined temperature to cure it. After that, the assembly substrate is diced for each constituent region of each module 1 to generate a plurality of modules 1 with the device chip 4 mounted as a bare chip (see FIG. 1).

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

Explanation of Reference Numerals

[0029] 1 Module 2 Module Substrate 2a Mounting Surface 2b Solder Resist Layer 2ba Blank Portion 2bb Opening Edge 2bc Surface 2bd Thickness Surface 2be Corner 2c Bump Pad 3 Electronic Device 3a Elastic Wave Device 4 Device Chip 4a One Surface 4b Side Surface 4c Outer Edge 4d Center 5, 50, 51 Resonators 5a IDT Electrode 5b Reflector 5c Electrode Finger 5d Bus Bar 5e Electrode Finger 5f Bus Bar 6 Wiring 7 Circuit 8 Signal Input / Output Terminal 9 Ground 10 Bump 10a Protruding End 11 Gap 11a Dimension 12 Sealing Portion 13 Film 14 Passage 14a First Location 14b Second Location 15 Sealing Portion x Propagation Direction L Spacing

Claims

1. A module in which two or more electronic devices are mounted on a module substrate, and a part of the two or more electronic devices is a device chip that functions as an elastic wave device, wherein the device chip includes a functional element including an IDT electrode on one surface thereof and a bump composed of solder connected to the functional element, and is mounted on the module substrate so as to create a gap between the one surface of the device chip and the mounting surface of the module substrate using the bump, the module substrate has a solder resist layer, and the solder resist layer covers a region to be coated on the mounting surface, a blank portion in the solder resist layer without the solder resist layer is formed under the one surface of the device chip, and two or more passages having a first location that communicates with the blank portion and is located under the one surface of the device chip and a second location that is outside the side surface having the thickness of the device chip and is not located under the one surface of the device chip are formed in the solder resist layer in the vicinity of the blank portion, a module provided with an elastic wave device.

2. The module provided with the elastic wave device according to claim 1, wherein the outer edge of the one surface of the device chip that contacts the side surface and the opening edge of the blank portion overlap in a state where the device chip is viewed from a direction perpendicular to the one surface at any position of the outer edge surrounding the center of the device chip, or the opening edge is positioned closer to the center side of the device chip than the outer edge in a range of 20 to 50 μm.

3. The module provided with the elastic wave device according to claim 1, wherein the passage is formed in a groove shape.

4. The module provided with the elastic wave device according to claim 1, further comprising a film that covers the device chip together with the module substrate and a sealing resin formed on the film.

5. The module provided with the elastic wave device according to claim 4, wherein a distance between the one surface of the device chip and the surface of the solder resist layer in a direction perpendicular to the one surface of the device chip is set to a dimension less than 1.5 times the thickness of the film.

6. The passage is formed in a groove shape, and A film that covers the device chip together with the module substrate, and a sealing resin formed on this film. Moreover, a module provided with the elastic wave device according to claim 1, wherein the groove width of the passage is made to be less than 1.5 times the thickness of the film.

7. A module provided with the elastic wave device according to claim 6, wherein the groove width of the passage is made to be in the range of 30 to 75 μm.

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