JP7508083B2 - Acoustic wave device package and module including an acoustic wave device - Google Patents

Description

This invention relates to improvements to acoustic wave device packages and modules including acoustic wave devices.

The acoustic wave devices used in mobile communication devices are generally configured to function as frequency filters such as bandpass filters by forming an interdigital transducer (IDT) on a piezoelectric substrate such as lithium tantalate or lithium niobate. In the case of a bandpass filter function, the center frequency is determined by the acoustic wave propagation speed of the piezoelectric substrate used and the electrode finger pitch and electrode finger length of the interdigital electrode. As the frequency band used in mobile communication in recent years becomes higher, the electrode finger pitch of the interdigital electrodes that make up the acoustic wave device tends to become finer. For this reason, when the interdigital electrodes are charged, the difference in the amount of charge between the opposing interdigital electrodes becomes a larger electric field (potential difference) between the interdigital electrodes than before, making it easier for breakdown and damage due to discharge between the interdigital electrodes, generally known as ESD (Electro-Static Discharge) breakdown, to occur.

However, in recent years, manufacturing lines for acoustic wave devices have become increasingly automated, and as a result, there are fewer opportunities for humans to touch devices during the manufacturing process, so ESD damage in HBM (Human Body Model) mode is on the decline.

On the other hand, acoustic wave devices in automated equipment can become charged due to friction or electrostatic induction, making it more likely that ESD damage will occur when the charged acoustic wave device comes into contact with metal.

This type of ESD damage is called CDM (Charged Device Model) mode, and until now, no effective structural countermeasures have been taken for acoustic wave devices. For this reason, when manufacturing acoustic wave devices, it has become necessary to take countermeasures such as installing static electricity removal equipment (ionizers) in locations on the production line where static electricity is likely to be generated. It has also become necessary to manage static electricity in the mounting process of acoustic wave devices, and the increased capital investment and labor required to achieve this has led to increased costs for acoustic wave devices and the parts and equipment that comprise them.

In addition, as the functions of acoustic wave devices become more diverse, some acoustic wave devices have ten or more comb electrodes. Some of these have floating electrode patterns that are not connected to the external terminals of the acoustic wave device and the potential is not fixed externally. Once charge accumulates in such a floating electrode pattern, it is difficult for the charge to escape, which can easily cause ESD damage.

In addition, in order to prevent pyroelectric breakdown during the manufacturing process of an elastic wave device, a technique is shown in Patent Document 1 in which a conductive member is brought into contact with the electrode pattern of the elastic wave device constituting the elastic wave device during the manufacturing process. For the same purpose, Patent Documents 2 and 3 show techniques in which the electrode pattern forming surface of the elastic wave device is covered with a protective film containing a conductive polymer during the manufacturing process of the elastic wave device, and then the protective film is removed. However, Patent Documents 1 to 3 do not aim to prevent ESD breakdown, and do not provide the elastic wave device itself with a structure that contributes to preventing ESD breakdown. In addition, the conductive resin layer constituting Patent Document 4 is required to be connected to the grounding conductor pattern, which is different from the basic configuration of the present application. In addition, the conductive resin in Patent Document 4 is required to have a thickness of about 1 mm or less and a resistance value of 10 Ω·cm or less in order to function as an electromagnetic shielding layer, and a low resistance value is preferable. Regarding the objective of this application, which is to improve ESD resistance, there is no need to reduce the resistance of the conductive resin to the same level as a metal film, for reasons described below, and the objectives and configuration are different.

JP 2006-33053 A Japanese Patent Application Laid-Open No. 9-172349 Japanese Patent Application Laid-Open No. 9-116364 Patent No. 3439975

The main problem that this invention aims to solve is to provide an acoustic wave device package and a module including an acoustic wave device with a structure that can prevent the ESD damage, i.e., a structure that improves ESD resistance, in an appropriate and rational manner.

In order to achieve the above object, from a first aspect, the present invention provides an acoustic wave device package comprising:
an acoustic wave device having a surface on which a comb-shaped electrode is formed on a surface of a piezoelectric substrate;
a package substrate on which the acoustic wave device is mounted with a gap formed between the package substrate and the one surface of the acoustic wave device;
a sealing resin formed on the package substrate on a side where the acoustic wave device is mounted, and forming a hollow portion between the package substrate and the acoustic wave device and surrounding the comb-shaped electrodes;
a conductive resin layer is formed between the sealing resin and the acoustic wave device so as to cover the entire other surface of the acoustic wave device opposite to the one surface and an end surface of the acoustic wave device ;
Moreover, the conductive resin layer is made of the same type of resin as the sealing resin, and the sheet resistance of the conductive resin layer is in the range of 1 kΩ/□ to 3 MΩ/□.

In another aspect of the present invention, the conductive resin layer is provided with an extension that is continuous with the portion that covers the end face of the acoustic wave device and covers at least a portion of the mounting side surface of the package substrate.

In addition, one aspect of the present invention is to electrically connect the extension portion to an electrode connected to an external connection terminal formed on the mounting side of the package substrate.

In order to achieve the above object, from a second viewpoint, the present invention provides a module including an acoustic wave device, comprising:
1. A module including at least one acoustic wave device, comprising:
an acoustic wave device having a surface on which a comb-shaped electrode is formed on a surface of a piezoelectric substrate;
Module components other than the acoustic wave device;
a module substrate on which the acoustic wave device is mounted with a gap formed between the surface of the acoustic wave device and the module substrate, and on which the components are mounted;
a sealing resin formed on the module substrate on a side where the acoustic wave device is mounted, and forming a hollow portion between the module substrate and the acoustic wave device and surrounding the comb-shaped electrodes;
a conductive resin layer is formed between the sealing resin and the acoustic wave device, the conductive resin layer covering at least a part of the other surface of the acoustic wave device opposite to the one surface ;
Moreover, the conductive resin layer is made of the same type of resin as the sealing resin, and the sheet resistance of the conductive resin layer is in the range of 1 kΩ/□ to 3 MΩ/□.

According to this invention, the conductive resin layer can be used to appropriately and rationally provide an acoustic wave device package and a module including an acoustic wave device with a structure that can prevent ESD damage, i.e., a structure that improves ESD resistance.

FIG. 1 is a perspective view of an acoustic wave device package (first example) according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the first example. FIG. 3 is a plan view of a main portion of an interdigital electrode formed in the acoustic wave device package of the first embodiment. FIG. 4 is a cross-sectional view of an acoustic wave device package (second example) according to one embodiment of the present invention. FIG. 5 is a cross-sectional view of an acoustic wave device package (third example) according to one embodiment of the present invention. FIG. 6 is a plan view of a module (fourth example) including an acoustic wave device according to an embodiment of the present invention. FIG. 7 is a cross-sectional view taken along line AA in FIG.

A typical embodiment of the present invention will be described below with reference to Figures 1 to 7. The acoustic wave device package D according to this embodiment comprises an acoustic wave device 1 (chip), a package substrate 2, a sealing resin 3 (mold resin), and a conductive resin layer 4.

(Acoustic Wave Device 1)
The acoustic wave device 1 has a piezoelectric substrate and an interdigital transducer 1b (IDT) formed on a surface 1a of the piezoelectric substrate 1. That is, the acoustic wave device 1 has a plate shape, and the surface 1a of the piezoelectric substrate 1 is used as the surface on which the interdigital transducer 1b is formed.

The acoustic wave device 1 also has a surface 1c opposite to the surface on which the comb-shaped electrode 1b is formed, and an end surface 1d along its thickness direction.

Figure 3 shows a plan view of the main part of an example of the comb electrode 1b. In Figure 3, which constitutes the comb electrode 1b, the length of the long electrode finger 1e indicated by the symbol L1 is, for example, 70 μm, the distance L2 between adjacent long electrode fingers 1e is, for example, 2.2 μm, and the distance L3 between the floating comb electrode 1g formed with a gap L3 between the tip of the short electrode finger 1f and the short electrode finger 1f is, for example, 0.4 μm.

(Package Substrate 2)
The package substrate 2 is configured to mount the acoustic wave device 1 thereon with a gap formed between the package substrate 2 and the surface 1 a of the acoustic wave device 1 .

The package substrate 2 is made of an insulating plate-shaped material. The package substrate 2 has a surface 2a on the mounting side of the acoustic wave device 1, a back surface 2b opposite the mounting surface 2a, and an end surface 2c along the thickness direction.

The package substrate 2 is sized so that the end face 2c of the package substrate 2 is positioned outside the end face 1d of the acoustic wave device 1 at any position around the center x of the acoustic wave device 1 (see Figures 1 and 2).

The acoustic wave device 1 is placed on the surface 2a of the package substrate 2 with the surface 1a in contact with the bumps 2d formed on the surface 2a of the package substrate 2. The bumps 2d and the acoustic wave device 1 are fixed by a known method such as ultrasonic welding. A typical example of the bumps 2d is a gold stud bump formed by the first bond of wire bonding.

A gap the size of the bump 2d is formed between the surface 1a of the acoustic wave device 1 and the surface 2a of the package substrate 2 at every location on the surface 1a of the acoustic wave device 1.

An external connection terminal 2e is formed on the back surface 2b of the package substrate 2. At least a portion of the interdigital electrode 1b of the acoustic wave device 1 mounted on the package substrate 2 as described above is electrically connected to the external connection terminal 2e, and the acoustic wave device package D is electrically connected to the outside through the external connection terminal 2e.

(Sealing resin 3)
The sealing resin 3 has insulating and hydrophobic properties, is formed on the mounting side of the package substrate 2, and cooperates with the package substrate 2 to hermetically seal the acoustic wave device 1. The sealing resin 3 forms a hollow portion 5 surrounding the comb-shaped electrode 1b between the package substrate 2 and the acoustic wave device 1, and also minimizes the intrusion of moisture from the outside of the package, making it possible to provide a highly reliable acoustic wave device package D with excellent moisture resistance.

The sealing resin 3 has an upper surface portion 3a located on the other surface 1c of the acoustic wave device 1, and an end surface portion 3b located outside the end surface 1d of the acoustic wave device 1 and flush with the end surface 2c of the package substrate 2. Due to the insulating and hydrophobic properties of the sealing resin 3, the acoustic wave device package D provided by applying the present invention can be inspected with an inspection device, packaged, stored, mounted on a board, and the like, in the same manner as existing standardized and normalized filter components.

(Conductive resin layer 4)
The conductive resin layer 4 is formed between the sealing resin 3 and the acoustic wave device 1 so as to cover at least 80% of the other surface 1 c of the acoustic wave device 1 .

In other words, the conductive resin layer 4 is formed before the sealing resin 3 is formed, after the acoustic wave device 1 is mounted on the surface 2a of the package substrate 2 as described above.

(First Example)
In the first example shown in Figures 1 and 2, the conductive resin layer 4 is formed so that the entire other surface 1c of the acoustic wave device 1 and the end surface 1d of the acoustic wave device 1 are covered by the conductive resin layer 4.

This makes it possible to prevent electrostatic charge from concentrating on the comb-shaped electrodes 1b that constitute the acoustic wave device 1, for example, when the acoustic wave device package D is placed in a high electric field (in an atmosphere that generates static electricity), when an electric charge is generated due to friction between the acoustic wave device packages D, or when the acoustic wave device package D is peeled off from a dicing tape after a dicing process.

In addition, the conductive resin layer 4 and the sealing resin 3 have high adhesion to each other, and the acoustic wave device package D can be constructed in a state where the two are firmly integrated. The conductive resin layer 4 can be formed with a thickness of 100 μm or less, and this thickness can be adjusted in the manufacturing conditions during the sealing resin part 3 formation process to eliminate the effect on the overall package size. Even if the conductive resin layer 4 is newly provided in this way, it is possible to fit it into the package size within the standardized specifications. It is desirable for the conductive resin layer 4 to have a sheet resistance of about 1 kΩ/□ to 3 MΩ/□. The charge movement speed in the conductive resin layer 4 with such a sheet resistance is significantly slower than that of a metal film. Therefore, the peak of the surrounding electric field generated by the movement of the charge when the conductive resin layer 4 is charged and the potential difference induced between the comb electrodes 1b, or between the comb electrode 1b and the floating comb electrode 1g, or between the floating comb electrodes 1g, which are induced on the opposite surfaces, can be suppressed as much as possible. The sheet resistance value of the conductive resin layer 4 can be adjusted by appropriately setting the particle size and density of the conductive filler uniformly dispersed in the resin base material, which is just one example. Typical resin base materials include epoxy, silicon, urethane, and polyimide resins, and from the viewpoint of improving adhesion with the sealing resin 3 after molding, it is desirable to use the same type of resin base material for the conductive resin layer 4 and the sealing resin 3. The conductive filler of the conductive resin layer 4 can be a carbon-based, metal-based, or conductive polymer-based filler.

(Second Example)
In the second example shown in Figure 4, the conductive resin layer 4 has an extension portion 4b that is continuous with a portion 4a covering the end face 1d of the acoustic wave device 1 and covers at least a portion of the mounting side surface 2a of the package substrate 2.

In the illustrated example, the extension portion 4b includes a first portion 4c that hangs down from the portion covering the end face 1d and abuts against the surface 2a, and a second portion 4d that continues outward from the bottom end of the first portion 4c and has a terminal located slightly inside the end face 2c of the package substrate 2. Also, in the illustrated example, the conductive resin layer 4 has a first portion 4c and a second portion 4d at every point around the center x of the acoustic wave device 1.

In this way, firstly, the area of the conductive resin layer 4 can be increased, which makes it easier to prevent electrostatic charge from concentrating on the comb-shaped electrodes 1b that constitute the acoustic wave device 1. Secondly, when forming the sealing resin 3, the extension portion 4b of the conductive resin layer 4 can prevent the resin that constitutes the sealing resin 3 from entering the gap, thereby forming the hollow portion 5.

In this second example, since the extension portion 4b can prevent the resin constituting the sealing resin 3 from entering the gap to create the hollow portion 5, there is no need to ensure a large distance y (see FIG. 4) between the end face 1d of the acoustic wave device 1 and the end face 2c of the package substrate 2 to minimize this intrusion, and the distance y can be reduced compared to the first example. Therefore, the structure of the second example contributes to reducing the size of the acoustic wave device package D. Furthermore, if the size is not reduced, the size of the acoustic wave device 1 can be maximized as much as possible, making it easier to provide room for forming the comb-shaped electrode 1b on the acoustic wave device 1 to add functions.

(Third Example)
In the third example shown in FIG. 5, the extension portion 4b is electrically connected to an electrode 2f connected to an external connection terminal 2e formed on the mounting side surface 2a of the package substrate 2.

In this case, the charge stored in the conductive resin layer 4 can be easily discharged using the external connection terminal 2e, thereby further improving the ESD resistance of the acoustic wave device package D. In this case, if the conductive resin layer 4 has the appropriate resistance value described above, the discharge is carried out slowly, suppressing the peak of the electric field and further improving the ESD resistance.

(Fourth Example)
The fourth example shown in FIG. 6 shows a module M including an acoustic wave device 1 and other module components 6 (resistor (R), inductor (L), capacitor (C), etc.). Representative examples of the front-end module components 6 are generally called chip resistors, chip inductors, chip capacitors, etc. These are components whose terminal metals are exposed on multiple surfaces and are surface-mounted on a module substrate 2'. The module substrate 2' has insulating properties like the package substrate 2.

A module M including such an acoustic wave device 1 includes at least one acoustic wave device 1 having a hollow portion 5 formed between the acoustic wave device 1 and a module substrate 2', which will be described later. The module M including such an acoustic wave device 1 includes an acoustic wave device 1 having a surface 1a on which a comb-shaped electrode 1b is formed, module components 6 other than the acoustic wave device 1, a module substrate 2' on which the acoustic wave device 1 is mounted and the components 6 are mounted with a gap formed between the surface 1a of the acoustic wave device 1, and a sealing resin 3 for the acoustic wave device 1 and the components 6 formed on the mounting side of the module substrate 2' with a hollow portion 5 surrounding the comb-shaped electrode 1b formed between the package substrate 2 and the acoustic wave device 1.

In addition, the module M including the acoustic wave device 1 is configured such that a conductive resin layer 4 is formed only between the sealing resin 3 and the acoustic wave device 1, covering at least a part of the other surface 1c of the acoustic wave device 1. In this configuration, the conductive resin layer 4 does not short-circuit the terminals of the components 6.

In this way, it is possible to configure a module M including an acoustic wave device 1 that ensures ESD resistance for the acoustic wave device 1 and prevents the conductive resin layer 4 from affecting the module components 6 that include other acoustic wave devices.

The following process is an example, and by doing so, the conductive resin layer 4 can be formed only on the acoustic wave device 1 on the module substrate 2'.
(1) A sheet made of a photosensitive conductive resin is prepared.
(2) Prior to the formation of the sealing resin 3, the sheet is patterned by photolithography so that when it is placed over a module substrate 2' carrying two acoustic wave devices 1 and two of the front module components 6, only the portions located over the two acoustic wave devices 1 remain on the module substrate 2'.

In this fourth example, the conductive resin portion is formed to cover the entire other surface 1c of the acoustic wave device 1 and the end surface 1d of the acoustic wave device 1, and is configured to include an extension portion 4b that continues from the portion 4a that covers the end surface 1d. However, there may be an embodiment in which there is no portion 4a that covers the end surface 1d, and there may also be an embodiment in which there is no extension portion 4b, as in the first example.

Naturally, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the object of the present invention.

D Acoustic wave device package M Module including acoustic wave device 1 Acoustic wave device 1a One surface 1b Comb-shaped electrode 1c Other surface 1d End surface 1e Long electrode fingers 1f Short electrode fingers 1g Floating comb-shaped electrode 2 Package substrate 2' Module substrate 2a Front surface 2b Back surface 2c End surface 2d Bump 2e External connection terminal 2f Electrode 3 Sealing resin 3a Top surface portion 3b End surface portion 4 Conductive resin layer 4a Portion covering end surface 4b Extension portion 4c First portion 4d Second portion 5 Hollow portion 6 Module components other than acoustic wave device

Claims (4)

an acoustic wave device having a surface on which a comb-shaped electrode is formed on a surface of a piezoelectric substrate;
a package substrate on which the acoustic wave device is mounted with a gap formed between the package substrate and the one surface of the acoustic wave device;
a sealing resin formed on the package substrate on a side where the acoustic wave device is mounted, and forming a hollow portion between the package substrate and the acoustic wave device and surrounding the comb-shaped electrodes;
a conductive resin layer is formed between the sealing resin and the acoustic wave device so as to cover the entire other surface of the acoustic wave device opposite to the one surface and an end surface of the acoustic wave device ;
Moreover, the elastic wave device package has a hollow structure, the conductive resin layer is made of the same type of resin as the sealing resin, and the sheet resistance of the conductive resin layer is in the range of 1 kΩ/□ to 3 MΩ/□. The acoustic wave device package having a hollow structure according to claim 1, wherein the conductive resin layer has an extension portion that is continuous with the portion that covers the end face of the acoustic wave device and covers at least a portion of the mounting side surface of the package substrate. The elastic wave device package having a hollow structure according to claim 2, in which the extension portion is electrically connected to an electrode connected to an external connection terminal formed on the mounting side surface of the package substrate. 1. A module including at least one acoustic wave device, comprising:
an acoustic wave device having a surface on which a comb-shaped electrode is formed on a surface of a piezoelectric substrate;
Module components other than the acoustic wave device;
a module substrate on which the acoustic wave device is mounted with a gap formed between the surface of the acoustic wave device and the module substrate, and on which the components are mounted;
a sealing resin formed on the module substrate on a side where the acoustic wave device is mounted, and forming a hollow portion between the module substrate and the acoustic wave device and surrounding the comb-shaped electrodes;
a conductive resin layer is formed between the sealing resin and the acoustic wave device, the conductive resin layer covering at least a part of the other surface of the acoustic wave device opposite to the one surface ;
Moreover, the module includes an acoustic wave device, and the conductive resin layer is made of the same type of resin as the sealing resin, and the sheet resistance of the conductive resin layer is in the range of 1 kΩ/□ to 3 MΩ/□.

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