Packaging structure of surface acoustic wave device

Abstract

The utility model provides a package structure of surface acoustic wave device relates to device package technical field, this package structure of surface acoustic wave device includes glass substrate, piezoelectric wafer and film layer, one side of glass substrate forms substrate recess, the bottom wall of substrate recess is provided with glass via, the conductive column is formed in glass via, piezoelectric wafer is attached on glass substrate, and solder ball is contained in substrate recess, and is connected to the conductive column correspondingly, film is set up on glass substrate, and is covered in piezoelectric wafer, the edge of piezoelectric wafer and the circumference of substrate recess interval correspond and form reserved gap. Compared with prior art, the utility model can reduce the package thickness. At the same time through setting up reserved gap, can avoid piezoelectric wafer directly lapping on glass substrate and causes solder ball welding when contact bad, slows down the welding bad phenomenon, reduces the process requirement.

Description

Technical Field

[0001] This utility model relates to the field of device packaging technology, and more specifically, to a packaging structure for a surface acoustic wave device. Background Technology

[0002] A filter is a device or circuit that processes signals, primarily filtering signals of a specific frequency range, allowing signals within that range to pass while blocking signals of other frequencies. A surface acoustic wave (SAW) filter is a filter that utilizes the propagation of surface acoustic waves on a crystal structure. Currently, the main packaging technologies for SAW filters include wire bonding of ceramic, metal, and plastic packages, leadless surface mounting, and flip-chip bonding. With the continuous development of communication technology, the performance requirements for filters are becoming increasingly demanding. Future filters need to have higher frequency selectivity, lower insertion loss, and greater power capacity. Simultaneously, filters also need to evolve towards smaller sizes and higher integration levels.

[0003] Existing filter packaging and structures of this type have the following drawbacks:

[0004] 1. The packaging substrate is too large and does not meet the current requirements for miniaturization.

[0005] 2. Some packaging methods have a relatively thick package thickness, which does not meet the requirements of current RF modules.

[0006] 3. Poor welding is prone to occur in the sealed cavity structure formed by the surrounding lifting. Utility Model Content

[0007] The purpose of this invention is to provide a packaging structure for surface acoustic wave devices that can reduce the packaging size to meet the requirements of miniaturization, while also reducing the packaging thickness and effectively mitigating soldering defects.

[0008] In a first aspect, this utility model provides a packaging structure for a surface acoustic wave device, comprising:

[0009] A glass substrate, wherein a substrate groove is formed on one side of the glass substrate, and a conductive through hole is provided on the bottom wall of the substrate groove, extending to the other side of the glass substrate, and a conductive pillar is filled in the conductive through hole.

[0010] A piezoelectric wafer is mounted on a glass substrate, and solder balls are provided on the side of the piezoelectric wafer close to the glass substrate. The solder balls are accommodated in the substrate groove and are correspondingly connected to the conductive post.

[0011] A coating layer is disposed on the glass substrate and covers the sidewalls of the piezoelectric wafer and the surface away from the glass substrate;

[0012] Wherein, the edge of the side surface of the piezoelectric wafer near the glass substrate is spaced with the periphery of the substrate groove to form a reserved gap, and the coating layer seals and covers the reserved gap so that a closed inner cavity is formed between the piezoelectric wafer and the glass substrate.

[0013] In an optional implementation, the reserved gap is between 10-30 mm.

[0014] In an optional embodiment, the coating layer extends into the reserved gap, and the portion of the coating layer extending into the reserved gap is in contact with both the glass substrate and the piezoelectric wafer.

[0015] In an optional embodiment, the piezoelectric wafer has a first pad and an interdigitated structure on the side near the glass substrate. The interdigitated structure and the first pad both correspond to the substrate groove, and the first pad and the interdigitated structure are spaced apart. The solder ball is disposed on the first pad.

[0016] In an optional embodiment, a second pad is provided at one end of the conductive post near the piezoelectric wafer, the second pad being disposed on the bottom wall of the substrate groove, and the solder ball being connected to the second pad accordingly; a third pad is also provided at one end of the conductive post away from the piezoelectric wafer, the third pad being disposed on the surface of the glass substrate.

[0017] In an optional embodiment, the solder ball includes a solder core ball and a solder layer, the solder core ball being disposed on the first pad, the solder layer covering the solder core ball and configured to bond to the second pad, and the melting point of the solder layer being lower than the melting point of the solder core ball.

[0018] In an optional embodiment, the thickness of the glass substrate is between 200-300 μm, the depth of the substrate groove is between 40-70 μm, and the protrusion height of the solder ball relative to the piezoelectric wafer is between 50-100 μm.

[0019] In an optional embodiment, the substrate groove includes a first stepped groove and a second stepped groove, the second stepped groove is disposed in the middle of the bottom wall of the first stepped groove, and the width of the second stepped groove is smaller than the width of the first stepped groove, and the interdigitated structure corresponds to the second stepped groove.

[0020] In an optional embodiment, the conductive via is disposed on the bottom wall of the second stepped groove, and the edge of the second stepped groove is correspondingly engaged with the solder ball.

[0021] In an optional embodiment, the diameter of the conductive via is between 30 and 100 μm.

[0022] The beneficial effects of this utility model embodiment include:

[0023] The surface acoustic wave (SAW) device packaging structure provided in this embodiment of the invention features a substrate groove formed on one side of a glass substrate. A glass through-hole is formed on the bottom wall of the substrate groove, penetrating the glass substrate. Conductive pillars are electroplated into the glass through-hole. A piezoelectric wafer is mounted on the glass substrate, with solder balls of the piezoelectric wafer housed in the substrate groove and correspondingly connected to the conductive pillars. A coating layer is disposed on the glass substrate and covers the sidewalls and top surface of the piezoelectric wafer. A pre-reserved gap is formed between the piezoelectric wafer and the periphery of the substrate groove, and the coating layer seals within this gap, creating a closed cavity between the piezoelectric wafer and the glass substrate. Compared to existing technologies, this embodiment of the invention reduces the packaging thickness by providing a substrate groove, and achieves electrical connection of the piezoelectric wafer through the glass through-hole and conductive pillars, avoiding conventional wire bonding structures. This ensures low in-band insertion loss and high out-of-band rejection while maintaining a small size. This significantly reduces substrate loss and parasitic effects, ensuring the integrity of the transmitted signal. Meanwhile, by setting a reserved gap, it is possible to avoid the piezoelectric wafer directly overlapping on the glass substrate, which would cause poor contact during solder ball welding, thus mitigating welding defects and reducing process requirements. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the packaging structure of the first surface acoustic wave device provided in this embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the packaging structure of the second surface acoustic wave device provided in this embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the packaging structure of the third surface acoustic wave device provided in this embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the packaging structure of the fourth surface acoustic wave device provided in this embodiment of the present invention;

[0029] Figures 5 to 11 A process flow diagram of the packaging method for the fourth surface acoustic wave device provided in this embodiment of the present invention.

[0030] Icons: 100 - Packaging structure of surface acoustic wave device; 110 - Glass substrate; 111 - Substrate groove; 113 - Glass via; 115 - First stepped groove; 117 - Second stepped groove; 130 - Piezoelectric wafer; 131 - Reserved gap; 133 - First pad; 135 - Interdigitated structure; 150 - Coating layer; 170 - Conductive pillar; 171 - Second pad; 173 - Third pad; 190 - Solder ball; 191 - Solder core ball; 193 - Solder layer; 200 - Seed layer; 300 - Photoresist layer; 310 - Opening. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of this utility model, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the utility model product is usually placed during use, they are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0035] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0036] As disclosed in the background section, existing SAW filter packaging technologies typically use wire-bonded ceramic, metal, or plastic packages, leadless surface mount and flip-chip bonding, etc. This results in excessively large package sizes and makes it difficult to control package thickness, which is not conducive to device miniaturization.

[0037] Furthermore, existing technologies have also developed recessed structures to accommodate filter packaging. However, if the recess is too large and completely encloses the filter, the package size will be excessively large. If the recess is too small, the filter edge overlaps with the recess edge, which places higher demands on the size of the solder balls. Moreover, the solder balls melt and deform during soldering, which can easily lead to poor contact between the solder balls and the solder pads, affecting the soldering effect.

[0038] To address the aforementioned problems, the packaging structure and method for surface acoustic wave (SAW) devices provided in this embodiment of the invention can reduce the packaging size, meeting miniaturization requirements, while simultaneously reducing the packaging thickness and effectively mitigating soldering defects. It should be noted that, where there is no conflict, the features in the embodiments of this invention can be combined with each other.

[0039] See Figure 1 The surface acoustic wave device packaging structure 100 provided in this embodiment of the present invention can reduce the packaging size, meet the requirements of miniaturization, and at the same time reduce the packaging thickness and process requirements, effectively mitigating the phenomenon of poor soldering.

[0040] The surface acoustic wave (SAW) device packaging structure 100 provided in this embodiment includes a glass substrate 110, a piezoelectric wafer 130, and a coating layer 150. A substrate groove 111 is formed on one side of the glass substrate 110, and a glass through-hole 113 extending to the other side of the glass substrate 110 is provided on the bottom wall of the substrate groove 111. Conductive pillars 170 are electroplated in the glass through-hole 113. The piezoelectric wafer 130 is mounted on the glass substrate 110, and solder balls 19 are provided on the side of the piezoelectric wafer 130 closest to the glass substrate 110. 0. Solder balls 190 are accommodated in the substrate groove 111 and are correspondingly connected to the conductive pillars 170. A coating is disposed on the glass substrate 110 and covers the sidewalls of the piezoelectric wafer 130 and the side surface away from the glass substrate 110. The edge of the side surface of the piezoelectric wafer 130 near the glass substrate 110 is spaced with the periphery of the substrate groove 111 to form a reserved gap 131. The coating layer 150 seals and covers the reserved gap 131 so that a closed inner cavity is formed between the piezoelectric wafer 130 and the glass substrate 110.

[0041] This embodiment of the invention, by providing a substrate groove 111, allows the solder balls 190 to be accommodated within the substrate groove 111, thereby reducing the package thickness. Electrical connection of the piezoelectric wafer 130 is achieved through the glass via 113 and conductive posts 170, avoiding conventional wire bonding structures. This ensures low in-band insertion loss and high out-of-band rejection while maintaining a small size. This significantly reduces substrate loss and parasitic effects, ensuring the integrity of the transmitted signal. Simultaneously, by providing a reserved gap 131, the piezoelectric wafer 130 is prevented from directly contacting the glass substrate 110, thus avoiding poor contact during soldering of the solder balls 190, mitigating soldering defects, and lowering process requirements.

[0042] It should be noted that the glass through-hole 113 here is a TGV through-hole, and the conductive pillar 170 can be a copper pillar formed by electroplating in the glass through-hole 113. That is, the conductive pillar 170 is formed by filling the glass through-hole 113 through electroplating process, and the connection between the conductive pillar 170 and the solder ball 190 is realized with the piezoelectric wafer 130.

[0043] In some embodiments, the reserved gap 131 is between 10-30 μm. Preferably, the reserved gap 131 can be 20 μm. By setting the reserved gap 131, the piezoelectric wafer 130 can be effectively prevented from directly overlapping the glass rib plate, ensuring sufficient contact between the solder ball 190 and the conductive post 170. Here, the coating layer 150 can cover the outer opening 310 of the reserved gap 131, thereby ensuring the uniformity of the coating layer 150 thickness and reducing process requirements.

[0044] See Figure 2 In some other embodiments, the coating layer 150 extends partially into the reserved gap 131, and the portion of the coating layer 150 extending into the reserved gap 131 simultaneously contacts the glass substrate 110 and the piezoelectric wafer 130. Specifically, the coating layer 150 can be formed by a molding process, during which the molding compound can flow into the reserved gap 131 and, after curing, partially remain in the reserved gap 131. The coating layer 150 retained in the reserved gap 131 can provide support, thereby supporting the piezoelectric wafer 130. At the same time, the partial embedding of the coating layer 150 into the reserved gap 131 can improve the bonding force between the coating layer 150, the piezoelectric wafer 130, and the glass substrate 110, effectively preventing delamination of the coating layer 150. Furthermore, the embedding of the coating layer 150 into the reserved gap 131 can improve the sealing effect, ensuring the formation of a sealed internal cavity.

[0045] Please see Figure 1 and Figure 2In some embodiments, the piezoelectric wafer 130 has a first pad 133 and an interdigitated structure 135 on the side near the glass substrate 110. Both the interdigitated structure 135 and the first pad 133 correspond to the substrate groove 111, and the first pad 133 and the interdigitated structure 135 are spaced apart. Solder balls 190 are disposed on the first pad 133. Specifically, the interdigitated structure 135 is an interdigitated electrode, which faces the bottom wall of the substrate groove and is spaced apart from the first pad 133, thus avoiding the welding structure from affecting the interdigitated electrode. Furthermore, there are multiple first pads 133, solder balls 190, and conductive pillars 170. Multiple solder balls 190 are respectively disposed on the first pad 133 and respectively soldered to the conductive pillars 170.

[0046] Furthermore, a second pad 171 is provided at the end of the conductive post 170 near the piezoelectric wafer 130. The second pad 171 is disposed on the bottom wall of the substrate groove 111, and solder balls 190 are correspondingly connected to the second pad 171. A third pad 173 is also provided at the end of the conductive post 170 away from the piezoelectric wafer 130, and the third pad 173 is disposed on the surface of the glass substrate 110. The second pad 171 and the third pad 173 can be integrally formed with the conductive post 170, and both are made of copper, providing good conductivity. In addition, multiple first pads 133 correspond to multiple second pads 171 respectively. The third pad 173 can be connected to external conductive terminals, or solder balls can be implanted on the third pad 173 to form external solder balls.

[0047] In some embodiments, the thickness of the glass substrate 110 is between 200-300 μm, the depth of the substrate groove 111 is between 40-70 μm, the protrusion height of the solder ball 190 relative to the piezoelectric wafer 130 is between 50-100 μm, and the diameter of the glass via 113 is between 30-100 μm. Specifically, the thickness of the glass substrate 110 is approximately 250 μm, and the depth of the substrate groove 111 can be adjusted according to the protrusion height of the solder ball 190. Of course, the parameters here are merely illustrative and not intended to be limiting.

[0048] See Figure 3In some preferred embodiments, the solder ball 190 includes a solder core ball 191 and a solder layer 193. The solder core ball 191 is disposed on a first pad 133, and the solder layer 193 covers the solder core ball 191 and is configured to bond to a second pad 171. The melting point of the solder layer 193 is lower than that of the solder core ball 191. Specifically, the solder core ball 191 is a copper core ball, and the solder layer 193 is a tin alloy material. The copper core ball is directly connected to the first pad 133, and the solder layer 193 covers the outside of the copper core ball. In actual soldering, the solder layer 193 is first brought into contact with the second pad 171, and then a reflow soldering process is used to allow the solder layer 193 to partially melt and bond to the second pad 171, completing the soldering. Since the reflow soldering temperature does not reach the melting point of copper, the copper core ball maintains its structural integrity. By adopting a double-layer structure, on the one hand, the addition of copper can improve the electrical connection performance and ensure the efficiency of signal transmission; on the other hand, it can play a structural support role during welding and prevent welding collapse.

[0049] It should be noted that the design of the solder core ball 191 here also ensures that a reserved gap 131 is formed between the piezoelectric wafer 130 and the glass substrate 110. Preferably, the outer diameter of the solder core ball 191 is larger than the depth of the substrate groove 111, thereby further preventing the piezoelectric wafer 130 from directly overlapping on the glass substrate 110, ensuring that all solder balls 190 can fully contact the second pad 171. Of course, the solder balls 190 here can also be of conventional solder ball construction, which can be soldered to the second pad 171 by controlling the reflow soldering process parameters.

[0050] See Figure 4 In some other embodiments, the substrate groove 111 includes a first stepped groove 115 and a second stepped groove 117. The second stepped groove 117 is disposed in the middle of the bottom wall of the first stepped groove 115, and the width of the second stepped groove 117 is smaller than the width of the first stepped groove 115. The interdigitated structure 135 corresponds to the second stepped groove 117. Specifically, the first stepped groove 115 and the second stepped groove 117 can be formed on the glass substrate 110 sequentially, that is, the first stepped groove 115 is etched first, and then the second stepped groove 117 is etched again in the middle of the first stepped groove 115, which can reduce the difficulty of grooving. And the interdigitated structure 135 corresponds to the second stepped groove 117, so that the interdigitated structure 135 has a deeper capacity groove space.

[0051] Furthermore, the glass through-hole 113 is disposed on the bottom wall of the second stepped groove 117, and the edge of the second stepped groove 117 is correspondingly engaged with the solder ball 190. Specifically, the glass through-hole 113 is disposed within the second stepped groove 117, and the connection between the first stepped groove 115 and the second stepped groove 117 can be used as an alignment mark to ensure the opening accuracy of the glass through-hole 113. At the same time, some of the solder balls 190 can also be aligned and engaged with the edge of the second stepped groove 117, improving the alignment accuracy and bonding strength, and ensuring the welding strength.

[0052] This utility model embodiment also provides a packaging method for a surface acoustic wave (SAW) device, used to prepare a packaging structure 100 for the SAW device as described above. The packaging method includes the following steps:

[0053] S1: A substrate groove 111 is formed by etching on one side surface of the glass substrate 110.

[0054] See Figure 5 Specifically, a glass substrate 110 is first provided, and then a substrate groove 111 is etched on one side surface of the glass substrate 110. The depth of the substrate groove 111 can be between 40-70μm, and the width of the substrate groove 111 can be smaller than the width of the piezoelectric wafer 130 that is subsequently mounted.

[0055] S2: A glass through-hole 113 is formed by etching the bottom wall of the substrate groove 111.

[0056] See Figure 6 Specifically, a glass through-hole 113 is formed by laser induction and etching, and the glass through-hole 113 extends to the other side of the glass substrate 110.

[0057] S3: Electroplating is performed in the glass through-hole 113 to form a conductive pillar 170.

[0058] See Figures 7 to 10 Specifically, a conductive pillar 170 can be formed in the glass through-hole 113 by electroplating a copper layer, and a second pad 171 and a third pad 173 are formed on both sides of the conductive pillar 170.

[0059] In the actual electroplating of copper pillars, a seed layer 200 can first be sputtered to form on the surface of the glass substrate 110 and the inner wall of the glass through-hole 113. The seed layer 200 can be a metallic material such as a titanium layer or a copper layer, and the seed layer 200 can cover both sides of the glass substrate 110 and the inner sidewall of the glass through-hole 113, such as... Figure 7 Then, a photoresist film layer 300 is formed by coating the surface of the seed layer 200. The photoresist film layer 300 can cover both sides of the glass substrate 110 and cover the glass vias 113, such as... Figure 8Then, through laser direct writing and development, an opening 310 is formed on the photoresist film layer 300 to expose the glass through-hole 113. The size of the opening 310 is slightly larger than the size of the glass through-hole 113, such as... Figure 9 Then, a copper layer is electroplated in the opening 310 to form conductive pillars 170, and simultaneously, a second pad 171 and a third pad 173 are formed. Finally, the photoresist film layer 300 is peeled off, and the seed layer 200 on the surface of the glass substrate 110 is flash-etched away. Figure 10 .

[0060] S4: The piezoelectric wafer 130 is flip-chip bonded to the glass substrate 110, wherein a solder ball 190 is provided on one side of the piezoelectric wafer 130, the solder ball 190 is accommodated in the substrate groove 111, and is correspondingly bonded to the conductive post 170.

[0061] Figure 11 Specifically, solder balls 190 can be formed on the first pad 133 of the piezoelectric wafer 130 in advance, and then the piezoelectric wafer 130 can be mounted on the glass substrate 110 by flip-chip bonding process. The solder balls 190 are correspondingly soldered to the second pad 171. After soldering, a reserved gap 131 is formed between the piezoelectric wafer 130 and the glass substrate 110 around the substrate groove 111.

[0062] S5: A coating layer 150 is formed on the glass substrate 110 by molding, and the coating layer 150 covers the sidewall of the piezoelectric wafer 130 and the side surface away from the glass substrate 110.

[0063] Please continue reading Figure 1 Specifically, a coating layer 150 is formed on the glass substrate 110 through a molding process. The coating layer 150 can cover the piezoelectric wafer 130 and seal the reserved gap 131, thereby forming a sealed inner cavity between the glass substrate 110 and the piezoelectric wafer 130.

[0064] In summary, the packaging structure 100 and packaging method of the surface acoustic wave device provided in this embodiment of the present invention have a substrate groove 111 formed on one side of a glass substrate 110. A glass through-hole 113 penetrating the glass substrate 110 is formed on the bottom wall of the substrate groove 111. A conductive pillar 170 is electroplated in the glass through-hole 113. Simultaneously, a piezoelectric wafer 130 is mounted on the glass substrate 110, and the solder balls 190 of the piezoelectric wafer 130 are accommodated in the substrate groove 111 and correspondingly connected to the conductive pillar 170. A coating layer 150 is disposed on the glass substrate 110 and covers the sidewalls and top surface of the piezoelectric wafer 130. The piezoelectric wafer 130 and the periphery of the substrate groove 111 are correspondingly spaced and a reserved gap 131 is formed. The coating layer 150 seals and covers the reserved gap 131, so that a closed inner cavity is formed between the piezoelectric wafer 130 and the glass substrate 110. Compared to existing technologies, this embodiment of the invention reduces package thickness by providing a substrate groove 111, and achieves electrical connection of the piezoelectric wafer 130 through glass vias 113 and conductive posts 170, avoiding conventional wire bonding structures. This ensures low in-band insertion loss and high out-of-band rejection while maintaining a small size. This significantly reduces substrate loss and parasitic effects, ensuring the integrity of transmitted signals. Simultaneously, by providing a reserved gap 131, it prevents the piezoelectric wafer 130 from directly overlapping the glass substrate 110, avoiding poor contact during soldering of the solder balls 190, mitigating soldering defects, and lowering process requirements.

[0065] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A packaging structure for a surface acoustic wave (SAW) device, characterized in that, include: A glass substrate, wherein a substrate groove is formed on one side of the glass substrate, and a conductive through hole is provided on the bottom wall of the substrate groove, extending to the other side of the glass substrate, and a conductive pillar is filled in the conductive through hole. A piezoelectric wafer is mounted on a glass substrate, and solder balls are provided on the side of the piezoelectric wafer close to the glass substrate. The solder balls are accommodated in the substrate groove and are correspondingly connected to the conductive post. A coating layer is disposed on the glass substrate and covers the sidewalls of the piezoelectric wafer and the surface away from the glass substrate; Wherein, the edge of the side surface of the piezoelectric wafer near the glass substrate is spaced with the periphery of the substrate groove to form a reserved gap, and the coating layer seals and covers the reserved gap so that a closed inner cavity is formed between the piezoelectric wafer and the glass substrate.

2. The packaging structure of the surface acoustic wave device according to claim 1, characterized in that, The reserved gap is between 10-30mm.

3. The packaging structure of the surface acoustic wave device according to claim 1 or 2, characterized in that, The coating layer extends into the reserved gap, and the portion of the coating layer extending into the reserved gap is in contact with both the glass substrate and the piezoelectric wafer.

4. The packaging structure of the surface acoustic wave device according to claim 1, characterized in that, The piezoelectric wafer has a first pad and an interdigitated structure on the side near the glass substrate. Both the interdigitated structure and the first pad correspond to the substrate groove, and the first pad and the interdigitated structure are spaced apart. The solder ball is disposed on the first pad.

5. The packaging structure of the surface acoustic wave device according to claim 4, characterized in that, A second pad is provided at one end of the conductive post near the piezoelectric wafer. The second pad is located on the bottom wall of the substrate groove, and the solder ball is connected to the second pad. A third pad is also provided at one end of the conductive post away from the piezoelectric wafer. The third pad is located on the surface of the glass substrate.

6. The packaging structure of the surface acoustic wave device according to claim 5, characterized in that, The solder ball includes a solder core ball and a solder layer. The solder core ball is disposed on the first pad, and the solder layer covers the solder core ball and is configured to bond to the second pad. The melting point of the solder layer is lower than that of the solder core ball.

7. The packaging structure of the surface acoustic wave device according to claim 4, characterized in that, The thickness of the glass substrate is between 200-300 μm, the depth of the substrate groove is between 40-70 μm, and the protrusion height of the solder ball relative to the piezoelectric wafer is between 50-100 μm.

8. The packaging structure of the surface acoustic wave device according to claim 4, characterized in that, The substrate groove includes a first stepped groove and a second stepped groove. The second stepped groove is disposed in the middle of the bottom wall of the first stepped groove, and the width of the second stepped groove is smaller than the width of the first stepped groove. The interdigitated structure corresponds to the second stepped groove.

9. The packaging structure of the surface acoustic wave device according to claim 8, characterized in that, The conductive through-hole is disposed on the bottom wall of the second stepped groove, and the edge of the second stepped groove is correspondingly engaged with the solder ball.

10. The packaging structure of the surface acoustic wave device according to claim 1, characterized in that, The diameter of the conductive via is between 30 and 100 μm.

Images