Elastic wave device package

Abstract

An elastic wave device package in which electrostatic breakdown is prevented as much as possible and as reasonably as possible. The elastic wave device package includes an elastic wave device, a package substrate, and a package resin. An electrode pattern of the elastic wave device has an extension portion that extends toward an outer edge of the elastic wave device. The package resin has a detouring entry portion that enters between the elastic wave device and the package substrate on the outer edge side of the elastic wave device and is electrically connected to the extension portion, and the package resin has electrical conductivity with a volume resistivity of 100 Ω·cm or more and 10 7 Ω·cm or less.

Description

Technical Field

[0001] The present invention relates to an elastic wave device package having a hollow structure encapsulated by an encapsulating resin, and particularly to an elastic wave device package having a structure that can reduce electrostatic damage. Background Technology

[0002] Surface elastic wave (SEL) filters are widely used in the transmitting / receiving circuits of mobile phones. The basic structure, as described in many specifications, is a resonator with comb-shaped electrodes formed on a piezoelectric substrate such as lithium tantalate or lithium niobate. This resonator has a narrow electrode pitch of approximately 0.7–2 μm. Because of the high impedance of the piezoelectric substrate, high potential differences caused by charge accumulation due to charging or discharging effects can easily lead to electrostatic discharge (ESD) damage. This ESD damage is most likely to occur during the packaging process—where the SEL is mounted on a packaging substrate, encapsulated with a packaging resin to form an SEL package—and the soldering process—where the SEL package is soldered onto a printed circuit board.

[0003] On the other hand, elastic wave devices must have a hollow structure. In the past, ceramic encapsulation was generally used to achieve such a hollow structure, but recently, in order to reduce costs, there has been an increasing trend of using molded resin encapsulation.

[0004] Regarding methods to prevent electrostatic discharge (ESD) damage to elastic wave devices, methods such as making the lithium tantalate or lithium niobate constituting the piezoelectric substrate conductive are well known in the industry. These methods include, for example, reduction treatment or iron doping (Japanese Patent Application Publication Nos. 2004-254114 and 2005-206444). However, while these methods are effective in preventing electrostatic discharge during wafer fabrication, they are insufficient for packaging and soldering processes, which operate in more intensely charged environments.

[0005] In addition, methods such as coating the surface with conductive resin as a static electricity countermeasure have been proposed, but they have the disadvantage of increasing the number of steps (Japanese Patent Application Publication No. 2006-033053, Japanese Patent Application Publication No. 9-116364, Japanese Patent Application Publication No. 9-172349). Summary of the Invention

[0006] The main problem that this invention aims to solve is to enable elastic wave devices to have a structure that can reasonably and as much as possible prevent electrostatic damage between the packaging process and the process of soldering the elastic wave device onto the printed circuit board.

[0007] To achieve the aforementioned goal, the present invention provides an elastic wave device package comprising: an elastic wave device having an electrode pattern comprising comb-shaped electrodes on one side of a piezoelectric substrate; a packaging substrate mounted on the elastic wave device, with a gap formed between the substrate and the side of the elastic wave device; and an encapsulating resin for the elastic wave device formed on the mounting side of the packaging substrate, wherein the electrode pattern has a plurality of independent potential points and a plurality of extensions connecting the independent potential points and extending toward the outer edge of the elastic wave device, the encapsulating resin having a meandering entry portion that enters between the elastic wave device and the packaging substrate on the outer edge side of the elastic wave device and is electrically connected to the extensions, and the encapsulating resin is coated with a volume resistivity of 100 Ω·cm or higher and 10 7 Conductivity below Ω·cm.

[0008] In one embodiment of the invention, the extension portion allows all the individual potential points in the electrode pattern to be electrically connected to the encapsulating resin.

[0009] In another embodiment of the invention, the extension portion is used to electrically connect a portion of the independent potential points in the electrode pattern to the encapsulating resin, while preventing other independent potential points from being electrically connected to the encapsulating resin.

[0010] In another embodiment of the invention, at least a portion of the independent potential points in the electrode pattern are electrically connected to the encapsulating resin through a plurality of the extension portions.

[0011] In another embodiment of the invention, the extended front end of the extension portion is connected to the outer edge of the elastic wave device.

[0012] In another embodiment of the invention, the electrode pattern is covered with an insulating film, and the extension has an exposed portion from which the insulating film is removed, the exposed portion being connected to the outer edge of the elastic wave device.

[0013] In another embodiment of the invention, the electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed, the exposed portion terminating in front of the outer edge of the elastic wave device without contacting the outer edge of the elastic wave device.

[0014] In another embodiment of the invention, the extended front end of the extended portion is spaced apart from the outer edge of the elastic wave device.

[0015] In another embodiment of the invention, the electrode pattern is covered with an insulating film, and the extension has an exposed portion from which the insulating film is removed, the exposed portion extending to the extension tip.

[0016] In another embodiment of the invention, the electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed, the exposed portion terminating before the extension tip without contacting the extension tip.

[0017] The present invention enables the encapsulation of elastic wave devices between the encapsulation process and the process of soldering the elastic wave devices onto a printed circuit board to have a structure that reasonably and as much as possible prevents electrostatic damage from occurring. Attached Figure Description

[0018] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein:

[0019] Figure 1 This is a bottom view of an elastic wave device (first embodiment) that constitutes an elastic wave device package according to one embodiment of the present invention;

[0020] Figure 2 This is a partial bottom surface configuration diagram of the elastic wave device (first embodiment);

[0021] Figure 3 This is a longitudinal cross-sectional view of the packaged elastic wave device;

[0022] Figure 4 yes Figure 3 Cross-sectional diagram at the position of line AA in the middle;

[0023] Figure 5 This is a partial bottom view showing other configuration examples of the elastic surface wave device (second embodiment);

[0024] Figure 6 This is a partial bottom view showing another configuration example (third embodiment) of the elastic surface wave device;

[0025] Figure 7 This is a partial bottom view of another configuration example (fourth embodiment) of the elastic surface wave device; and

[0026] Figure 8 This is a partial bottom view of another configuration example (fifth embodiment) of an elastic surface wave device. Detailed Implementation

[0027] The following is based on Figures 1 to 8 This describes an embodiment of the present invention. The elastic wave device package D of this embodiment includes an elastic wave device 1 (chip), a packaging substrate 2, and a packaging resin 3 (molding resin).

[0028] (Elastic wave device 1)

[0029] The elastic wave device 1 has an electrode pattern 1j formed by a metal film and including comb-shaped electrodes 1k (IDT) on one side 1b of the piezoelectric substrate 1a. That is, the elastic wave device 1 is plate-shaped, and its one side 1b is the forming surface of the electrode pattern 1j.

[0030] In addition, the elastic wave device 1 has another side 1c opposite to the forming surface of the comb electrode 1k, and an end face 1d along its thickness direction.

[0031] The edge portion between the surface 1b and the end face 1d forms the outer edge 1e of the elastic wave device 1.

[0032] In addition, the electrode pattern 1j has an extension 1n extending toward the outer edge 1e of the elastic wave device 1.

[0033] Figure 1 This is an example of the configuration of this standard. The electrode pattern 1j has several comb-shaped electrodes 1k, several wirings 1m, and several extensions 1n. In each figure, for ease of explanation, the portions forming the comb-shaped electrodes 1k are shown with diagonal solid lines; the portions forming the wirings 1m are shown with diagonal dashed lines; the portions forming the pad electrodes 1p (described later) are shown with diagonal dotted lines; and the exposed portions 1o of the extensions 1n after the insulating film has been removed (described later) are shown with intersecting lines.

[0034] The elastic wave device 1 has a quadrilateral profile. Regardless of which side of the elastic wave device 1 ( Figure 1 The top 1f, bottom 1g, left 1h, and right 1i of the wiring 1m are all spaced at a predetermined distance L from the outer edge 1e of the elastic wave device 1 (refer to the reference). Figure 2 ).

[0035] exist Figure 1 In the example shown, the extension 1n extends between the wiring 1m and the outer edge 1e. That is, each extension 1n starts from the wiring 1m and extends to the outer edge 1e in a direction perpendicular to the periphery of the adjacent side of each wiring 1m. In this example, the extension tip 1n' of the extension 1n coincides with the cutting position in the cutting step.

[0036] In addition, such as Figure 5 As shown, the extended front end 1n' of the extension portion 1n is separated from the outer edge 1e by a gap distance.

[0037] Furthermore, in the illustrated example, the number of extensions 1n is the same as the number of independent potential nodes E in the electrode pattern 1j. That is, one extension 1n is connected to the wiring 1m that constitutes an independent potential node E.

[0038] However, sometimes it is not necessary for all independent potential points E to be connected to the extension 1n. Since the locations where charge easily accumulates and the locations of comb electrodes 1k that are easily damaged by electrostatic discharge due to charge accumulation vary with the design of each elastic wave device 1, it is difficult to generalize this situation. However, if the comb electrodes 1k that are not easily damaged by electrostatic discharge are identified by other methods, the extension 1n connecting the comb electrodes 1k that are not easily damaged by electrostatic discharge can be omitted.

[0039] However, sometimes it is not necessary for all independent potential points E to be connected to the extension 1n. Since the locations where charge easily accumulates and the locations of comb electrodes 1k that are easily damaged by electrostatic discharge due to charge accumulation vary with the design of each elastic wave device 1, it is difficult to generalize this situation. However, if the comb electrodes 1k that are not easily damaged by electrostatic discharge are identified by other methods, the extension 1n connecting the comb electrodes 1k that are not easily damaged by electrostatic discharge can be omitted.

[0040] Although not shown in the attached figures, in this situation, the elastic wave device package D, through the extension 1n, makes a portion of the independent potential points E in the electrode pattern 1j electrically connected to the encapsulation resin 3, while preventing other independent potential points E from being electrically connected to the encapsulation resin 3.

[0041] Similarly, if comb-shaped electrodes 1k that are prone to electrostatic discharge (ESD) damage are identified using other methods, the extension portion 1n connecting these ESD-prone comb-shaped electrodes 1k can be made wider, or as... Figure 6 As shown, by giving an independent potential point E several extensions 1n, its effect can be increased.

[0042] The other methods mentioned above can actually investigate the location of damage by applying high voltage to several elastic wave devices 1 to statistically determine whether the comb electrodes 1k are prone to or not prone to electrostatic damage. Alternatively, they can predict whether the comb electrodes 1k are prone to or not prone to electrostatic damage based on design information such as the distance between the electrodes of the comb electrodes 1k.

[0043] Here, the independent potential point E mentioned in this specification refers to the wiring portion that is separated from other wiring portions by the comb electrode 1k in the wiring 1m constituting the electrode pattern 1j.

[0044] The electrode pattern 1j is covered with an insulating film. By removing this insulating film from the extension tip 1n' side of the extension portion 1n, the metal film constituting the extension portion 1n is exposed. Figure 1 and Figure 2 In the embodiment shown, this exposed portion 1o is connected to the outer edge 1e of the elastic wave device 1.

[0045] In addition, such as Figure 7 As shown, the exposed portion 1o may also terminate slightly inward from the outer edge 1e of the elastic wave device 1.

[0046] In addition, such as Figure 8 As shown, the extended front end 1n' of the extended portion 1n may also be spaced apart from the outer edge 1e by a gap, and the exposed portion 1o may also terminate slightly inward in front of the extended front end 1n'.

[0047] (Packaging substrate 2)

[0048] The packaging substrate 2 is equipped with the elastic wave device 1 with a gap G formed between it and one side 1b of the elastic wave device 1.

[0049] The packaging substrate 2 is made of a plate-shaped material with insulating properties. The packaging substrate 2 has a mounting side for mounting the elastic wave device 1, a front side 2a located on the mounting side, a back side 2b located on the opposite side of the front side 2a of the mounting side, and an end face 2c along the thickness direction.

[0050] The size of the packaging substrate 2 is sufficient to ensure that any position on the end face 2c of the packaging substrate 2 surrounding the center of the elastic wave device 1 is located outside the end face 1d of the elastic wave device 1.

[0051] The standard elastic wave device 1 is mounted on the front side 2a of the packaging substrate 2, with a pad electrode 1p formed on one side 1b of the elastic wave device 1 and a pad electrode 2d formed on the front side 2a of the packaging substrate 2, and integrated by a bump 4 pre-formed on the side of the packaging substrate 2.

[0052] The bump 4 is formed using a first bond technique, typically gold stud bumping. The bump 4 is fixedly bonded to the pad electrode 1p of the elastic wave device 1 using well-known methods such as ultrasonic welding.

[0053] The bump 4 located between one side 1b of the elastic wave device 1 and the front side 2a of the packaging substrate 2, and the gap G with a width equivalent to the thickness of the pad electrodes 1p and 2d, can be formed at any position on one side 1b of the elastic wave device 1.

[0054] An external terminal 2e is formed on the back side 2b of the packaging substrate 2. At least a portion of the comb-shaped electrodes 1k of the elastic wave device 1 mounted on the packaging substrate 2 in the manner described above are electrically connected to this external terminal 2e through the wiring 1m, and the elastic wave device package D is electrically connected to the outside through this external terminal 2e.

[0055] (Encapsulating Resin 3)

[0056] Encapsulating resin 3 is formed on the mounting side of the encapsulation substrate 2, and cooperates with the encapsulation substrate 2 to make the elastic wave device 1 hermetically sealed. Through this encapsulating resin 3, a hollow portion 5 is formed between the encapsulation substrate 2 and the elastic wave device 1, surrounding the comb-shaped electrode 1k and the wiring 1m.

[0057] The encapsulating resin 3 has an upper portion 3a located on the other side 1c of the elastic wave device 1, and a side portion 3b located outside the end face 1d of the elastic wave device 1 and flush with the outside of the end face 2c of the encapsulating substrate 2.

[0058] In addition, the encapsulating resin 3 has a detour entry portion 3c, which enters between the elastic wave device 1 and the encapsulation substrate 2 on the outer edge 1e side of the elastic wave device 1, and is electrically connected to the extension portion 1n.

[0059] That is, the side portion 3b of the encapsulating resin 3 covers the end face 1d of the elastic wave device 1, and its lower end is in close contact with the front face 2a of the encapsulating substrate 2, and its inner side has the meandering entry portion 3c.

[0060] In the illustrated embodiment, the detour entry portion 3c is formed within the predetermined distance L, contacts all of the extension portions 1n of the plurality of independent potential points E, and does not contact the wiring 1m (reference). Figure 4 Furthermore, the detour entry portion 3c should not come into contact with the protrusion 4.

[0061] Furthermore, the encapsulating resin 3 has a volume resistivity of 100 Ω·cm or higher and 10 7 Conductivity below Ω·cm.

[0062] The impedance between the independent potential points E must be sufficiently greater than the impedance of that part of the circuit; otherwise, high-frequency loss will occur. Specifically, when the circuit impedance is 100Ω, if the impedance between the independent potential points E is 100kΩ or more, that is, more than 1000 times the circuit impedance, it will have almost no impact on high-frequency characteristics. Moreover, the impedance between terminals in typical elastic wave filter products is often specified to be 1MΩ or more, or 10MΩ or more, so these conditions must also be taken into consideration.

[0063] Furthermore, if the impedance between the independent potential points E is too high, it will take too long to release the charge, thus losing its effect in preventing electrostatic discharge. Typically, the capacitance between the independent potential points E is around 0.1 to 1 picofarad (pF). Therefore, as long as the impedance is below 100 GΩ, the discharge time will be less than 100 milliseconds to release the charge.

[0064] Here, the relationship between the actual electrical impedance value and the volume resistivity is derived. For a realistic comparison, let's assume, for example, that the contact area between the extension 1n and the encapsulating resin 3 is 10 μm × 10 μm, and the spacing between adjacent extensions 1n is 100 μm. After simplification, it can be considered approximately as a cuboid-shaped resistivity with a cross-sectional area of ​​10 μm × 10 μm and a length of 100 μm. In this case, an electrical impedance value of 1 MΩ becomes a volume resistivity of 100 Ω·cm. Similarly, an electrical impedance value of 100 GΩ becomes a volume resistivity of 10... 7 Volume resistivity in Ω·cm.

[0065] As described above, the encapsulating resin 3 has a volume resistivity of 100 Ω·cm or higher and 10 7 Conductivity below Ω·cm is more suitable.

[0066] This level of volume resistivity can be achieved by mixing carbon powder or conductive powder into the resin material constituting the encapsulating resin 3.

[0067] Regarding this volume resistivity value, it is not possible to achieve the same effect simply by being within the range of values ​​described above. Rather, the most appropriate value must be selected by taking into account factors such as the contact area between the extension and the conductive resin, the shape of the roundabout entry of the encapsulating resin, and the intensity of the charge generated during the manufacturing process.

[0068] In the elastic wave device package described above, the components such as forming an extension portion 1n as an additional pattern on the electrode pattern 1j of the elastic wave device 1 and making the encapsulating resin 3 conductive are no different from those in conventional elastic wave device packages. Therefore, no additional process is required during manufacturing. In other words, the elastic wave device package described above can be manufactured using conventional processes.

[0069] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A package for an elastic wave device, characterized in that: The elastic wave device package includes: an elastic wave device, an electrode pattern formed on one side of a piezoelectric substrate and including comb-shaped electrodes; a packaging substrate having a mounting side for mounting the elastic wave device and a gap formed between the packaging substrate and one side of the elastic wave device; and an encapsulating resin formed on the mounting side of the packaging substrate and capable of forming a hollow portion surrounding the comb-shaped electrodes between the packaging substrate and the elastic wave device; wherein the electrode pattern has a plurality of independent potential points and a plurality of extensions connecting the independent potential points and extending toward the outer edge of the elastic wave device, the electrode pattern is covered with an insulating film, and the insulating film at the extension tip of the extensions is removed, the encapsulating resin has a detour entry portion that enters between the elastic wave device and the packaging substrate at the outer edge of the elastic wave device and is electrically connected to the extensions, and the encapsulating resin has a volume resistivity of 100 Ω·cm or more and 10 7 Conductivity below Ω·cm.

2. The elastic wave device package according to claim 1, characterized in that: The extension portion allows all the individual potential points in the electrode pattern to be electrically connected to the encapsulating resin.

3. The elastic wave device package according to claim 1, characterized in that: The extension allows a portion of the independent potential points in the electrode pattern to be electrically connected to the encapsulating resin, while preventing other independent potential points from being electrically connected to the encapsulating resin.

4. The elastic wave device package according to claim 1, characterized in that: Through several of the aforementioned extensions, at least a portion of the independent potential points in the electrode pattern are electrically connected to the encapsulating resin.

5. The elastic wave device package according to claim 1, characterized in that: The extended front end of the extension is connected to the outer edge of the elastic wave device.

6. The elastic wave device package according to claim 5, characterized in that: The electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed, the exposed portion being connected to the outer edge of the elastic wave device.

7. The elastic wave device package according to claim 5, characterized in that: The electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed. The exposed portion terminates in front of the outer edge of the elastic wave device without contacting the outer edge of the elastic wave device.

8. The elastic wave device package according to claim 1, characterized in that: The extended front end of the extension portion is spaced apart from the outer edge of the elastic wave device.

9. The elastic wave device package according to claim 8, characterized in that: The electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed, the exposed portion extending to the extension tip.

10. The elastic wave device package according to claim 8, characterized in that: The electrode pattern is covered with an insulating film, and the extension has an exposed portion where the insulating film is removed, the exposed portion terminating before the extension tip without contacting the extension tip.

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