WLP package SAW filter and radio frequency module

Abstract

The utility model provides a kind of WLP package SAW filter and radio frequency module.In the WLP package SAW filter, retaining wall layer has first opening and defines several second openings in first opening, first opening surrounds interdigital transducer and first ground pad on substrate, second opening corresponds with the position of first ground pad, cover plate layer covers first opening to form cavity, third opening in cover plate layer and second opening are communicated to become first through-hole, and mold pressing barrier area terminal fills first through-hole and is connected with first ground pad, and mold pressing barrier area terminal extends from first through-hole to cover at least part of the surface of cover plate layer above cavity from outside;Wherein, mold pressing barrier area terminal is welded with substrate, and plastic package body is wrapped WLP package SAW filter and is filled in the side of mold pressing barrier area terminal. Thus the ability of cavity in SAW filter can be improved to resist plastic package high pressure, and the electrical performance of SAW filter will not be affected. Radio frequency module includes the WLP package SAW filter described above.

Description

Technical Field

[0001] This utility model relates to the field of filter technology, and in particular to a WLP-packaged SAW filter and RF module. Background Technology

[0002] Surface Acoustic Wave (SAW) filters are filters that propagate sound waves along a solid surface and consist of piezoelectric materials and interdigital transducers (IDTs). To protect the IDT from damage, a sealed cavity needs to be formed on its surface, and electrodes need to be brought out to the device surface. Currently, the cavity is typically constructed using two layers of PI film or resin-based thin film through photolithography, with one layer acting as a wall and the other as a roof. However, during module molding, the high molding temperature of such SAW filters can reduce the mechanical strength of the roof material, making the cavity unable to withstand the high pressure during molding. This allows the roof material to easily come into contact with the IDT, causing the entire SAW filter to malfunction and ultimately leading to module failure.

[0003] Currently, to withstand the high pressure during molding, the thickness of the cover layer is often increased. However, this increases the thickness of the device, which is not conducive to further miniaturization of the device. Utility Model Content

[0004] This invention provides a WLP-packaged SAW filter and RF module, which can improve the ability of the cavity in the SAW filter to withstand high pressure from the plastic encapsulation, help avoid cavity collapse, improve the reliability of the SAW filter and RF module, and does not affect the electrical performance of the SAW filter.

[0005] To achieve the above objectives, this utility model provides a WLP-packaged SAW filter. The WLP-packaged SAW filter includes: a substrate, the surface of which has interdigital transducers and a plurality of pads located on the sides of the interdigital transducers, the plurality of pads including several first ground pads; a barrier layer, located on the substrate, the barrier layer having a first opening and defining several second openings within the first opening, the first opening surrounding the interdigital transducers and the first ground pads, the second openings corresponding to the positions of the first ground pads; and a cover layer, located on the barrier layer, the cover layer covering the first opening and forming a cavity with the barrier layer, the cover layer having several third openings. A third opening is located on and communicates with a second opening to form a first through-hole; a solder layer, a portion of which serves as a molded blocking region terminal, the molded blocking region terminal filling the first through-hole and connected to the first ground pad, and the molded blocking region terminal extending outward from the first through-hole to cover at least a portion of the surface of the cover layer directly above the cavity; wherein the WLP-packaged SAW filter is mounted on a substrate, and the molded blocking region terminal is soldered to the substrate, and a molding compound on the substrate encapsulates the WLP-packaged SAW filter and fills the sides of the molded blocking region terminal.

[0006] Optionally, the plurality of pads further include a plurality of signal pads and a plurality of second ground pads located outside the first opening; the baffle layer has a plurality of fourth openings and a plurality of sixth openings, one of the fourth openings corresponding to one of the signal pads; the cover plate layer has a plurality of fifth openings, one of the fifth openings being located on one of the fourth openings and communicating with one of the fourth openings to form a second through hole; one of the sixth openings corresponding to one of the second ground pads; the cover plate layer has a plurality of seventh openings, one of the seventh openings being located on one of the sixth openings and communicating with one of the sixth openings to form a third through hole; a portion of the solder layer serves as a signal terminal and a portion serves as a ground terminal; the signal terminal fills the second through hole and is connected to the signal pad; the ground terminal fills the third through hole and is connected to the second ground pad.

[0007] Optionally, the solder layer includes a bottom metal layer, an intermediate metal layer on the bottom metal layer, and a tin-containing metal layer on the intermediate metal layer; the bottom metal layer fills the first through-hole and extends outward to cover at least a portion of the surface of the cover layer directly above the cavity.

[0008] Optionally, the bottom metal layer is a redistribution layer that covers at least a portion of the surface of the signal pad and extends along the sidewall of the second via to the top surface of the cover plate layer, and the redistribution layer covers at least a portion of the surface of the second ground pad and extends along the sidewall of the third via to the top surface of the cover plate layer, with the intermediate metal layer and the tin-containing metal layer located on the redistribution layer on the cover plate layer.

[0009] Optionally, the redistribution layer of the grounding terminal and the redistribution layer of the molded blocking area terminal are connected on the cover plate layer.

[0010] Optionally, the WLP-packaged SAW filter further includes an insulating passivation layer that covers a portion of the surface of the bottom metal layer above the cover plate layer. The insulating passivation layer has a solder layer opening located on the cover plate layer, the solder layer opening corresponding to a portion of the surface of the bottom metal layer on the cover plate layer, and the intermediate metal layer and the tin-containing metal layer located within the solder layer opening.

[0011] Optionally, the widths of the second through hole and the third through hole are both greater than the width of the first through hole; the bottom metal layer does not fill the second through hole and the third through hole but fills the first through hole.

[0012] Optionally, the bottom metal layer fills the first through hole, the second through hole, and the third through hole and extends outward from the first through hole, the second through hole, and the third through hole to cover a portion of the top surface of the cover plate layer, and the intermediate metal layer and the tin-containing metal layer at least cover a portion of the bottom metal layer.

[0013] Optionally, the bottom metal layer is a copper layer, the middle metal layer is a nickel layer, and the tin-containing metal layer is a tin-silver layer.

[0014] This utility model also provides an RF module. The RF module includes: the aforementioned WLP-packaged SAW filter; a substrate, wherein the WLP-packaged SAW filter is mounted on the front side of the substrate, and the molded blocking region terminal, signal terminal, and ground terminal of the WLP-packaged SAW filter are all soldered to the substrate; electronic components, wherein the electronic components are mounted on the front side of the substrate; and a molding compound, wherein the molding compound is located on the front side of the substrate and encapsulates the WLP-packaged SAW filter and the electronic components, and the molding compound fills the sides of the molded blocking region terminal, the signal terminal, and the ground terminal.

[0015] In the WLP-packaged SAW filter and RF module provided by this utility model, since the molding barrier terminals on the cavity are directly welded to the substrate, the area where the molding barrier terminals are located is not filled with molding compound during injection molding. This reduces the impact area and force on the cover plate and cavity during molding compound filling, improving the cavity's ability to withstand high molding pressure, preventing cavity collapse, and enhancing the reliability of the WLP-packaged SAW filter and RF module. Furthermore, this design eliminates the need to increase the cover plate thickness or reduce the cavity size to improve the cavity's pressure resistance, facilitating larger cavity designs and reducing the size of the WLP-packaged SAW filter. The size of the packaged SAW filter increases the design flexibility of the WLP-packaged SAW filter. Since the molded blocking region terminal fills the first through-hole and connects to the first ground pad, and is soldered to the substrate, the molded blocking region terminal can be connected to the ground pad of the substrate after soldering. This allows the molded blocking region terminal to be completely grounded. There is no induced potential between the molded blocking region terminal and the interdigital transducer located below the molded blocking region terminal and within the cavity, overcoming the parasitic effects of the molded blocking region terminal. This facilitates complete isolation between signal terminals and does not affect the electrical performance of the WLP-packaged SAW filter. Furthermore, compared to the technical solution where the molded blocking region terminal on the cavity is only connected to the cover plate layer, the molded blocking region terminal in this application fills the first through-hole and connects to the first ground pad instead of being suspended on the cavity. This helps reduce deformation and cracking of the cover plate layer at the connection point, reducing the probability of cover plate layer collapse leading to WLP-packaged SAW filter failure. Simultaneously, the molded blocking region terminal can also assist in dissipating heat from the substrate, improving the heat dissipation effect of the WLP-packaged SAW filter. Attached Figure Description

[0016] Figure 1 This is a top view of a WLP-packaged SAW filter provided in an embodiment of the present invention.

[0017] Figure 2 For along Figure 1 A cross-sectional view of the location indicated by line AB.

[0018] Figure 3 For along Figure 1 A cross-sectional view of the location indicated by line CD.

[0019] Figure 4 This is a cross-sectional schematic diagram of a radio frequency module provided in an embodiment of the present invention.

[0020] Figure 5 This is a top view of a WLP-packaged SAW filter provided in another embodiment of the present invention.

[0021] Figure 6This is a top view of a WLP-packaged SAW filter according to another embodiment of the present invention.

[0022] Figure 7 This is a top view of a WLP-packaged SAW filter according to another embodiment of the present invention.

[0023] Figure 8 For along Figure 6 A cross-sectional view of the location indicated by line AB.

[0024] Figure 9 For along Figure 6 A cross-sectional view of the location indicated by line CD.

[0025] Figure 10 This is a cross-sectional schematic diagram of a radio frequency module provided in another embodiment of the present invention.

[0026] Figures 11 to 15 This is a schematic diagram illustrating the fabrication process of a WLP-packaged SAW filter according to an embodiment of the present invention.

[0027] Figures 16 to 20 A schematic diagram illustrating the fabrication process of a WLP-packaged SAW filter according to another embodiment of this utility model.

[0028] Explanation of reference numerals in the attached figures: 10-substrate; 101-interdigital transducer; 102-first ground pad; 103-signal pad; 104-second ground pad; 11-barrier layer; 111-first opening; 112-second opening; 113-fourth opening; 12-cover layer; 121-third opening; 122-fifth opening; 13-cavity; 14-soldering layer; 141-bottom metal layer; 142-intermediate metal layer; 143-tin-containing metal layer; 14a-molded barrier terminal; 14b-signal terminal; 14c-ground terminal; 15-insulating passivation layer; 20-substrate; 21-electronic component; 22-molded enclosure. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0030] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the terms “multiple” and “at least two” are generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature, unless otherwise expressly indicated.

[0031] In the embodiments of this application, "upper", "lower", "left" and "right" are not limited to the orientation of the components in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0032] Figure 1 This is a top view of a WLP-packaged SAW filter provided in an embodiment of the present invention. Figure 2 For along Figure 1 A cross-sectional view of the location indicated by line AB. Figure 3 For along Figure 1 A cross-sectional view of the location indicated by line CD. Figure 4 This is a cross-sectional schematic diagram of a radio frequency module provided in an embodiment of the present invention.

[0033] refer to Figures 1 to 4As shown, the WLP-packaged SAW filter provided in this embodiment includes a substrate 10, a barrier layer 11, a cover layer 12, and a solder layer 14. The substrate 10 has an interdigital transducer 101 on its surface and multiple solder pads located on the sides of the interdigital transducer 101. The multiple solder pads include several first ground pads 102. The barrier layer 11 is located on the substrate 10. The barrier layer 11 has a first opening 111 and defines several second openings 112 within the first opening 111. The first opening 111 surrounds the interdigital transducer 101 and the first ground pads 102, and the second openings 112 correspond to the positions of the first ground pads 102. The cover layer 12 is located on the barrier layer 11. The cover layer 12 covers the first opening 111 and forms a cavity 1 with the barrier layer 11. 3. The cover layer 12 has a plurality of third openings 121, one third opening 121 being located on a second opening 112 and communicating with the second opening 112 to form a first through hole; a portion of the solder layer 14 serves as a molding barrier terminal 14a, the molding barrier terminal 14a filling the first through hole and connecting to the first ground pad 102, and the molding barrier terminal 14a extending outward from the first through hole to cover at least a portion of the surface of the cover layer 12 directly above the cavity 13; wherein, the WLP packaged SAW filter is mounted on the substrate 20, and the molding barrier terminal 14a is soldered to the substrate 20, and the encapsulation 22 on the substrate 20 encapsulates the WLP packaged SAW filter and fills the side of the molding barrier terminal 14a.

[0034] Specifically, the substrate 10 can be made of a piezoelectric material, i.e., the substrate 10 is a piezoelectric substrate; or, the substrate 10 can be a composite wafer (POI), which includes a semiconductor wafer and a piezoelectric layer located on the surface of the semiconductor wafer. The materials of the piezoelectric material and the piezoelectric layer can include, but are not limited to, lithium niobate or lithium tantalate. The materials of the semiconductor wafer can include silicon, germanium, or silicon-germanium, etc.

[0035] The substrate 10 has an interdigital transducer 101 and a plurality of pads (i.e. electrodes) located on the side of the interdigital transducer 101.

[0036] For example, refer to Figure 1 As shown, the pads located below the cover plate layer 12 are represented by dashed lines. The multiple pads may include multiple first ground pads 102, multiple signal pads 103, and multiple second ground pads 104. The number of first ground pads 102 can be one, and the number of second ground pads 104 can also be one.

[0037] For example, the material of the interdigital transducer 101 may include metallic materials such as aluminum (Al), copper (Cu), gold (Au), silver (Ag), chromium (Cr), titanium (Ti), or tungsten (W), and may also include alloys of the above metallic materials. The material of the pads may be the same as, but is not limited to, the material of the interdigital transducer 101.

[0038] refer to Figure 2 and Figure 3 As shown, the barrier layer 11 is located on the substrate 10. The barrier layer 11 has a first opening 111 and defines a plurality of second openings 112 within the first opening 111. The first opening 111 surrounds the interdigital transducer 101 and the first ground pad 102. The second openings 112 are located above the first ground pad 102 and correspond to the position of the first ground pad 102.

[0039] It should be noted that in this application, the first grounding pad 102 is located inside the first opening 111, and the signal pad 103 and the second grounding pad 104 are located outside the first opening 111. The shape of the first opening 111 can be designed as needed.

[0040] refer to Figure 2 and Figure 3 As shown, the retaining wall layer 11 may have multiple fourth openings 113 and several sixth openings (not shown). A fourth opening 113 is located on a signal pad 103 and corresponds to the position of a signal pad 103. A sixth opening is located on a second ground pad 104 and corresponds to the position of a second ground pad 104.

[0041] For example, the material of the barrier layer 11 may be a polyimide (PI) or resin-based material with exposure properties, but is not limited thereto. For example, the material of the barrier layer 11 may be a dry film, but is not limited thereto. For example, the thickness of the barrier layer 11 may be greater than or equal to 5 µm and less than or equal to 15 µm, but is not limited thereto.

[0042] refer to Figure 2 and Figure 3 As shown, the cover plate layer 12 is located on the retaining wall layer 11. The cover plate layer 12 covers the first opening 111 to form a cavity 13 with the retaining wall layer 11. The cover plate layer 12 has a plurality of third openings 121. One third opening 121 is located on a second opening 112 and communicates with a second opening 112 to form a first through hole.

[0043] refer to Figure 1 , Figure 2 and Figure 3 As shown, the cover plate layer 12 has a plurality of fifth openings 122. One fifth opening 122 is located on a fourth opening 113 and is connected to the fourth opening 113 to form a second through hole. The second through hole is located on the surface of the signal pad 103. The cover plate layer 12 also has a plurality of seventh openings (not shown). One seventh opening is located on a sixth opening and is connected to the sixth opening to form a third through hole. The third through hole is located on the second ground pad 104.

[0044] Among them, the first through hole, the second through hole and the third through hole can all be stepped through holes with a larger top and a smaller bottom. The width of the third opening 121 can be greater than the width of the second opening 112, the width of the fifth opening 122 can be greater than the width of the fourth opening 113, and the width of the seventh opening can be greater than the width of the sixth opening. This can improve the filling quality of the through holes.

[0045] For example, the material of the cover layer 12 may be a polyimide (PI) or resin-based material with exposure properties, but is not limited thereto. For example, the material of the cover layer 12 may be a dry film, but is not limited thereto. For example, the thickness of the cover layer 12 may be greater than or equal to 15 µm, but is not limited thereto.

[0046] refer to Figures 1 to 3 As shown, a portion of the solder layer 14 serves as a molding barrier terminal 14a, which fills the first through hole and is connected to the first grounding pad 102. The molding barrier terminal 14a extends outward from the first through hole and covers at least a portion of the surface of the cover layer 12 directly above the cavity 13.

[0047] Part of the solder layer 14 serves as a signal terminal 14b and part serves as a ground terminal 14c. The signal terminal 14b fills the second through-hole and is connected to the signal pad 103, while the ground terminal 14c fills the third through-hole and is connected to the second ground pad 104. Both the signal terminal 14b and the ground terminal 14c can extend outward from their respective through-holes to cover a portion of the surface of the cover layer 12. The signal terminal 14b and the ground terminal 14c are separate from each other, and the signal terminal 14b is separate from the molding blocking area terminal 14a.

[0048] refer to Figure 1 As shown, the top surface shape of the molding blocking area terminal 14a can be rectangular, and the top surface shape of the signal terminal 14b and the ground terminal 14c can be circular, but are not limited to this. Figure 5 A top view of a WLP-packaged SAW filter according to another embodiment of the present invention. (See reference) Figure 5 As shown, the top surface shape of the molding barrier terminal 14a can also be cross-shaped, and the top surface shape of the signal terminal 14b and the ground terminal 14c can be rectangular. The top shapes of the molding barrier terminal 14a, signal terminal 14b and ground terminal 14c can be designed as needed and are not limited to circular, rectangular or cross-shaped.

[0049] refer to Figure 2 and Figure 3As shown, the solder layer 14 may include a bottom metal layer 141, an intermediate metal layer 142 located on the bottom metal layer 141, and a tin-containing metal layer 143 located on the intermediate metal layer 142; the bottom metal layer 141 fills the first through-hole (including the second opening 112 and the third opening 121) and extends outward to cover at least a portion of the surface of the cover plate layer 12 directly above the cavity 13. The solder layer 14 is a patterned metal layer.

[0050] In one embodiment of this application, as Figure 2 and Figure 3 As shown, the bottom metal layer 141 fills the first through hole (including the second opening 112 and the third opening 121), the second through hole (including the fourth opening 113 and the fifth opening 122) and the third through hole to realize the connection between the bottom metal layer 141 and the first ground pad 102, the signal pad 103 and the second ground pad 104, and the bottom metal layer 141 extends outward from the first through hole, the second through hole and the third through hole to cover part of the top surface of the cover plate layer 12, and the intermediate metal layer 142 and the tin-containing metal layer 143 at least cover part of the bottom metal layer 141.

[0051] Figure 6 This is a top view of a WLP-packaged SAW filter according to another embodiment of the present invention. Figure 7 This is a top view of a WLP-packaged SAW filter according to another embodiment of the present invention. Figure 8 For along Figure 6 A cross-sectional view of the location indicated by line AB. Figure 9 For along Figure 6 A cross-sectional view of the location indicated by line CD. Figure 10 This is a cross-sectional schematic diagram of a radio frequency module provided in another embodiment of the present invention. Figure 6 and Figure 7 In the diagram, the pads and cavities located below the cover plate are represented by dashed lines.

[0052] In another embodiment of this application, reference is made to... Figures 6 to 9 As shown, the bottom metal layer 141 can be a redistribution layer (RDL). The redistribution layer covers at least a portion of the surface of the signal pad 103 and extends along the sidewall of the second via to the top surface of the cover layer 12 away from the barrier layer 11. The redistribution layer also covers at least a portion of the surface of the second ground pad 104 and extends along the sidewall of the third via to the top surface of the cover layer 12. In other words, the redistribution layer leads both the signal pad 103 and the second ground pad 104 to the top surface of the cover layer 12.

[0053] In this embodiment, such as Figure 8 and Figure 9As shown, the widths of the second and third through holes can both be greater than the width of the first through hole. Here, the width refers to the maximum width of each through hole. The bottom metal layer 141 does not completely fill the second and third through holes but can fill the first through hole. In other embodiments, the bottom metal layer 141 may also not completely fill the first through hole but cover the bottom surface and sidewalls of the first through hole.

[0054] refer to Figures 6 to 9 As shown, the intermediate metal layer 142 and the tin-containing metal layer 143 are located on the redistribution layer on the cover plate layer 12. Specifically, the WLP-packaged SAW filter may also include an insulating passivation layer 15, which covers the redistribution layer and pad surfaces within the second and third vias, and partially covers the surface of the bottom metal layer 141 (i.e., the redistribution layer) above the cover plate layer 12. The insulating passivation layer 15 has a solder layer opening located on the cover plate layer 12, which corresponds to the position of a portion of the surface of the bottom metal layer 141 on the cover plate layer 12. The intermediate metal layer 142 and the tin-containing metal layer 143 are located within the solder layer opening, and the top surface of the tin-containing metal layer 143 protrudes from the insulating passivation layer 15 to facilitate soldering between the WLP-packaged SAW filter and the substrate.

[0055] The insulating passivation layer 15 restricts the free flow of the tin-containing metal layer 143 during the welding process. The material of the insulating passivation layer 15 can be an inorganic material such as silicon oxide or silicon nitride, or an insulating organic material such as polyimide or resin with exposure properties.

[0056] refer to Figure 6 and Figure 7 As shown, the redistribution layer of grounding terminal 14c and the redistribution layer of molded blocking area terminal 14a can be connected together on cover layer 12.

[0057] In this application, the thickness of the bottom metal layer 141 located on the cover plate layer 12 can be greater than or equal to 5µm, the thickness of the middle metal layer 142 can be greater than or equal to 2µm and less than or equal to 4µm, and the thickness of the tin-containing metal layer 143 can be greater than or equal to 5µm, but is not limited thereto.

[0058] For example, the bottom metal layer 141 can be a copper layer, the middle metal layer 142 can be a nickel layer, and the tin-containing metal layer 143 can be a tin-silver layer, but is not limited thereto.

[0059] refer to Figure 4 and Figure 10As shown, the WLP-packaged SAW filter is mounted on substrate 20. The surface of substrate 20 may have multiple pads corresponding to ground terminal 14c, signal terminal 14b, and molding barrier terminal 14a, respectively. Molding barrier terminal 14a is soldered to the corresponding pad on the surface of substrate 20, signal terminal 14b is soldered to the corresponding pad on the surface of substrate 20, and ground terminal 14c is soldered to the corresponding pad on the surface of substrate 20.

[0060] The substrate 20 may also have a molding compound 22, which encapsulates the WLP-packaged SAW filter and fills the side of the molding barrier terminal 14a. In this way, when the molding compound 22 is formed, the area where the molding barrier terminal 14a is located is not filled with molding compound, which can reduce the impact area and impact force on the cover layer 12 and cavity 13 when the molding compound is filled. This can improve the ability of the cavity 13 in the WLP-packaged SAW filter to resist high molding pressure, which helps to avoid the collapse of the cavity 13 and improve the reliability of the WLP-packaged SAW filter.

[0061] This utility model provides an radio frequency module. (Reference) Figure 4 and Figure 10 As shown, the RF module includes a substrate 20, electronic components 21, the aforementioned WLP-packaged SAW filter, and a molding compound 22. The WLP-packaged SAW filter is mounted on the front side of the substrate 20, and the molded blocking region terminal 14a, signal terminal 14b, and ground terminal 14c of the WLP-packaged SAW filter are all soldered to the substrate 20. The electronic components 21 are mounted on the front side of the substrate 20. The molding compound 22 is located on the front side of the substrate 20 and encapsulates the WLP-packaged SAW filter and the electronic components 21, and the molding compound 22 fills the sides of the molded blocking region terminal 14a, signal terminal 14b, and ground terminal 14c.

[0062] For example, substrate 20 may be a printed circuit board (PCB), but is not limited thereto.

[0063] Electronic component 21 can be a passive device or other chips. Passive devices can include capacitors, resistors, or inductors. The number of electronic components 21 can be one or more.

[0064] The materials of the molding compound 22 include, but are not limited to, epoxy molding compound.

[0065] This application also provides the fabrication process for WLP-packaged SAW filters and RF modules.

[0066] Figures 11 to 15 This is a schematic diagram illustrating the fabrication process of a WLP-packaged SAW filter according to an embodiment of the present invention. The following is in conjunction with... Figures 11 to 15 The fabrication process of a WLP-packaged SAW filter is explained.

[0067] refer to Figure 1 and Figure 11 As shown, a substrate 10 is provided, the surface of which has an interdigital transducer 101 and a plurality of pads located on the side of the interdigital transducer 101. The plurality of pads include a plurality of first ground pads 102, a plurality of signal pads 103 and a plurality of second ground pads 104.

[0068] refer to Figure 11 As shown, the substrate 10 may have multiple sets of interdigital transducers 101 and multiple sets of pads corresponding to the multiple sets of interdigital transducers 101.

[0069] refer to Figure 1 , Figure 3 and Figure 12 As shown, a barrier layer 11 is formed on the substrate 10. The barrier layer 11 has a first opening 111 and defines a plurality of second openings 112 within the first opening 111. The first opening 111 surrounds the interdigital transducer 101 and the first ground pad 102. The second openings 112 correspond to the positions of the first ground pad 102. The barrier layer 11 may also have a plurality of fourth openings 113 and a plurality of sixth openings (not shown). One fourth opening 113 corresponds to the position of one signal pad 103, and one sixth opening corresponds to the position of one second ground pad 104.

[0070] A method for forming a barrier layer 11 on a substrate 10 may include: forming a barrier material layer on the substrate 10 by vacuum lamination or spin coating; exposing, pre-baking, and developing the barrier material layer to form the barrier layer 11. For example, the barrier material layer may include a PI or resin-based material with exposure properties.

[0071] refer to Figure 1 , Figure 3 and Figure 13 As shown, a cover plate layer 12 is formed on the retaining wall layer 11. The cover plate layer 12 covers the first opening 111 and forms a cavity 13 with the retaining wall layer 11. The cover plate layer 12 has a plurality of third openings 121. One third opening 121 is located on a second opening 112 and communicates with a second opening 112 to form a first through hole.

[0072] refer to Figure 1 and Figure 13 As shown, the cover plate layer 12 also has a plurality of fifth openings 122. One fifth opening 122 is located on a fourth opening 113 and is connected to the fourth opening 113 to form a second through hole. The second through hole is located on the surface of the signal pad 103. The cover plate layer 12 also has a plurality of seventh openings (not shown). One seventh opening is located on a sixth opening and is connected to the sixth opening to form a third through hole. The third through hole is located on the second ground pad 104.

[0073] The method for forming the cover layer 12 on the barrier layer 11 may include: laminating a cover material layer onto the barrier layer 11; and patterning the cover material layer by exposure and development or by laser ablation to form the cover layer 12. After patterning the cover material layer, the cover layer 12 may be baked and hardened if necessary. The cover material layer may include, but is not limited to, PI or resin-based materials with exposure properties.

[0074] refer to Figure 1 , Figure 3 and Figure 14 As shown, a solder layer 14 is formed on the substrate 10. A portion of the solder layer 14 serves as a molding barrier terminal 14a. The molding barrier terminal 14a fills the first through hole and is connected to the first ground pad 102. The molding barrier terminal 14a extends outward from the first through hole and covers at least a portion of the surface of the cover layer 12 directly above the cavity 13.

[0075] refer to Figure 14 and Figure 1 As shown, part of the solder layer 14 serves as a signal terminal 14b and part serves as a ground terminal 14c. The signal terminal 14b fills the second through hole and is connected to the signal pad 103, and the ground terminal 14c fills the third through hole and is connected to the second ground pad 104.

[0076] In one embodiment of this application, the method for forming a solder layer 14 on a substrate 10 may include: forming a seed layer on the substrate 10 by sputtering deposition, wherein the seed layer completely covers the substrate 10, the barrier layer 11, and the cover layer 12; coating the seed layer with photoresist to form a photoresist layer; exposing and developing the photoresist layer to form a patterned photoresist layer; generating the solder layer 14 by electroplating under the protection of the patterned photoresist layer; and then removing the patterned photoresist layer and removing excess seed layer from the sides of the solder layer 14. In this embodiment, the solder layer 14 may fill the first via, the second via, and the third via.

[0077] For example, the material of the seed layer may include titanium (Ti) and copper (Cu), but is not limited thereto. The solder layer 14 includes a bottom metal layer 141, an intermediate metal layer 142 and a tin-containing metal layer 143 stacked from bottom to top.

[0078] Figures 16 to 20 A schematic diagram illustrating the fabrication process of a WLP-packaged SAW filter according to another embodiment of this utility model.

[0079] In another embodiment of this application, such as Figure 16 As shown, after the barrier layer 11 and the capping layer 12 are formed on the substrate 10, reference Figure 6 , Figure 9 and Figure 17As shown, a bottom metal layer 141 is formed on the substrate 10 as a redistribution layer. The redistribution layer fills the first via and extends outward to cover at least a portion of the surface of the cover layer 12 directly above the cavity 13. The redistribution layer covers at least a portion of the surface of the signal pad 103 and extends along the sidewall of the second via to the top surface of the cover layer 12. The redistribution layer covers at least a portion of the surface of the second ground pad 104 and extends along the sidewall of the third via to the top surface of the cover layer 12. The redistribution layer leads the signal pad 103 and the second ground pad 104 to the cover layer 12 on the side of the via.

[0080] In this embodiment, the widths of the second and third through holes can both be greater than the width of the first through hole; the redistribution layer fills the first through hole but not the second and third through holes, resulting in better thermal conductivity for the molded blocking region terminal 14a. In other embodiments, the redistribution layer may not fill the first through hole.

[0081] An exemplary method for forming a bottom metal layer 141 of a redistribution layer on a substrate 10 may include: forming a first seed layer on the substrate 10, the first seed layer covering the substrate 10, the barrier layer 11, and the cover layer 12; forming a patterned first photoresist layer on the first seed layer; and forming the bottom metal layer 141 of the redistribution layer by electroplating under the protection of the patterned first photoresist layer; removing the patterned first photoresist layer; and etching away any excess of the first seed layer.

[0082] refer to Figure 6 , Figure 9 and 18 As shown, an insulating passivation layer 15 is formed on the substrate 10. The insulating passivation layer 15 covers the redistribution layer and the pad surface in the second and third vias, and covers a portion of the surface of the redistribution layer above the cover plate layer 12. The insulating passivation layer 15 has a solder layer opening on the cover plate layer 12, and the solder layer opening corresponds to the position of a portion of the surface of the redistribution layer on the cover plate layer 12.

[0083] refer to Figure 6 , Figure 9 and Figure 19 As shown, an intermediate metal layer 142 and a tin-containing metal layer 143 are formed on the bottom metal layer 141 (i.e., the redistribution layer), forming a solder layer 14 including the bottom metal layer 141, the intermediate metal layer 142 and the tin-containing metal layer 143.

[0084] Specifically, the intermediate metal layer 142 and the tin-containing metal layer 143 are located within the solder layer opening, and the top surface of the tin-containing metal layer 143 protrudes from the insulating passivation layer 15 to facilitate soldering between the WLP packaged SAW filter and the substrate.

[0085] An exemplary method for forming an intermediate metal layer 142 and a tin-containing metal layer 143 on a bottom metal layer 141 may include: forming a second seed layer on a substrate 10, the second seed layer entirely covering the substrate 10, the barrier layer 11, the cover layer 12, and the insulating passivation layer 15; forming a patterned second photoresist layer on the second seed layer; using the patterned second photoresist layer as a mask, electroplating to form the intermediate metal layer 142 and the tin-containing metal layer 143; removing the patterned second photoresist layer and etching to remove excess second seed layer, forming a solder layer 14. Thus, a first seed layer is present below the bottom metal layer 141, and a second seed layer is present between the intermediate metal layer 142 and the bottom metal layer 141. The materials of both the first seed layer and the second seed layer include, but are not limited to, copper and / or titanium.

[0086] After forming weld layer 14, refer to Figure 15 and Figure 20 As shown, substrate 10 is cut to obtain a single WLP-packaged SAW filter. Cutting can be performed after thinning the substrate 10. A single WLP-packaged SAW filter may include, but is not limited to, a set of interdigital transducers 101 and a set of pads corresponding to those interdigital transducers 101.

[0087] Next, refer to Figure 4 and Figure 10 As shown, a single WLP-packaged SAW filter and electronic component 21 are mounted on substrate 20. The molded blocking region terminal 14a of the WLP-packaged SAW filter is soldered to the substrate 20. The signal terminal 14b and ground terminal 14c of the WLP-packaged SAW filter can also be soldered to substrate 20.

[0088] A molding compound is filled on the substrate 20 to form a molding compound 22, which encapsulates the WLP packaged SAW filter and electronic component 21, and the molding compound of the molding compound 22 fills the sides of the molding barrier terminal 14a, signal terminal 14b and ground terminal 14c.

[0089] In the WLP-packaged SAW filter and RF module provided by this utility model, since the molding barrier terminal 14a on the cavity 13 is directly welded to the substrate 20, the area where the molding barrier terminal 14a is located is not filled with molding compound during the injection molding of the encapsulated body 22. This reduces the impact area and impact force on the cover layer 12 and the cavity 13 during molding compound filling, thereby improving the cavity's ability to withstand high molding pressure in the WLP-packaged SAW filter, helping to avoid cavity collapse and improving the reliability of the WLP-packaged SAW filter and RF module. At the same time, this eliminates the need to increase the thickness of the cover layer or reduce the size of the cavity to improve the cavity's pressure resistance, which is beneficial for achieving larger cavity designs and reducing the size of the WLP-packaged SAW filter. The size of the WLP-packaged SAW filter increases the design flexibility of the WLP-packaged SAW filter. Since the molded blocking region terminal 14a fills the first through-hole and connects to the first ground pad 102, and is soldered to the substrate 20, the molded blocking region terminal 14a can be connected to the ground pad of the substrate 20 after soldering. This allows the molded blocking region terminal 14a to be completely grounded. There is no induced potential between the molded blocking region terminal 14a and the interdigital transducer 101 located below the molded blocking region terminal 14a and within the cavity 13, overcoming the parasitic effects caused by the molded blocking region terminal 14a, which is advantageous. To achieve complete isolation between signal terminals, the electrical performance of the WLP-packaged SAW filter will not be affected. In addition, compared with the technical solution where the molded blocking region terminal on the cavity is only connected to the cover plate layer, the molded blocking region terminal 14a of this application fills the first through hole and is connected to the first ground pad 102 instead of being suspended on the cavity 13. This helps to reduce the deformation and cracking of the cover plate layer 12 at the connection, and helps to reduce the probability of the WLP-packaged SAW filter failing due to the collapse of the cover plate layer 12. At the same time, the molded blocking region terminal 14a can also help to conduct heat out of the substrate 10, which helps to improve the heat dissipation effect of the WLP-packaged SAW filter.

[0090] The above description is only a description of the preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model. Any person skilled in the art can make possible changes and modifications to the technical solution of the present utility model by using the methods and techniques disclosed above without departing from the spirit and scope of the present utility model. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the content of the technical solution of the present utility model shall fall within the protection scope of the technical solution of the present utility model.

Claims

1. A WLP-packaged SAW filter, characterized in that, include: A substrate having an interdigital transducer on its surface and a plurality of pads located on the side of the interdigital transducer, the plurality of pads including a plurality of first ground pads; A barrier layer is located on the substrate. The barrier layer has a first opening and defines a plurality of second openings within the first opening. The first opening surrounds the interdigital transducer and the first ground pad. The second openings correspond to the positions of the first ground pad. A cover plate layer is located on the retaining wall layer. The cover plate layer covers the first opening and forms a cavity with the retaining wall layer. The cover plate layer has a plurality of third openings. One of the third openings is located on a second opening and communicates with a second opening to form a first through hole. A welding layer, a portion of which serves as a molded blocking area terminal, the molded blocking area terminal filling the first through hole and connected to the first grounding pad, and the molded blocking area terminal extending outward from the first through hole to cover at least a portion of the surface of the cover plate layer directly above the cavity; The WLP-packaged SAW filter is mounted on a substrate, and the molded blocking region terminal is soldered to the substrate. The encapsulation on the substrate encapsulates the WLP-packaged SAW filter and fills the side of the molded blocking region terminal.

2. The WLP-packaged SAW filter as described in claim 1, characterized in that, The plurality of pads also include a plurality of signal pads and a plurality of second ground pads located outside the first opening; The retaining wall layer has multiple fourth openings and several sixth openings. One of the fourth openings corresponds to one of the signal pad positions. The cover plate layer has multiple fifth openings. One of the fifth openings is located on one of the fourth openings and is connected to one of the fourth openings to form a second through hole. One of the sixth openings corresponds to one of the second ground pad positions. The cover plate layer has several seventh openings. One of the seventh openings is located on one of the sixth openings and is connected to one of the sixth openings to form a third through hole. Part of the solder layer serves as a signal terminal and part serves as a ground terminal. The signal terminal fills the second through-hole and is connected to the signal pad. The ground terminal fills the third through-hole and is connected to the second ground pad.

3. The WLP-packaged SAW filter as described in claim 2, characterized in that, The welding layer includes a bottom metal layer, an intermediate metal layer on the bottom metal layer, and a tin-containing metal layer on the intermediate metal layer; the bottom metal layer fills the first through hole and extends outward to cover at least a portion of the surface of the cover plate layer directly above the cavity.

4. The WLP-packaged SAW filter as described in claim 3, characterized in that, The bottom metal layer is a redistribution layer that covers at least a portion of the surface of the signal pad and extends along the sidewall of the second via to the top surface of the cover plate layer. The redistribution layer also covers at least a portion of the surface of the second ground pad and extends along the sidewall of the third via to the top surface of the cover plate layer. The intermediate metal layer and the tin-containing metal layer are located on the redistribution layer on the cover plate layer.

5. The WLP-packaged SAW filter as described in claim 4, characterized in that, The redistribution layer of the grounding terminal and the redistribution layer of the molded blocking area terminal are connected on the cover plate layer.

6. The WLP-packaged SAW filter as described in claim 4, characterized in that, The WLP-packaged SAW filter further includes an insulating passivation layer that covers a portion of the surface of the bottom metal layer above the cover plate. The insulating passivation layer has a solder layer opening located on the cover plate, the solder layer opening corresponding to a portion of the surface of the bottom metal layer on the cover plate. The intermediate metal layer and the tin-containing metal layer are located within the solder layer opening.

7. The WLP-packaged SAW filter as described in claim 4, characterized in that, The widths of the second and third through holes are both greater than the width of the first through hole; the bottom metal layer does not fill the second and third through holes but fills the first through hole.

8. The WLP-packaged SAW filter as described in claim 3, characterized in that, The bottom metal layer fills the first through hole, the second through hole, and the third through hole and extends outward from the first through hole, the second through hole, and the third through hole to cover part of the top surface of the cover plate layer. The intermediate metal layer and the tin-containing metal layer at least cover part of the bottom metal layer.

9. The WLP-packaged SAW filter as described in claim 3, characterized in that, The bottom metal layer is a copper layer, the middle metal layer is a nickel layer, and the tin-containing metal layer is a tin-silver layer.

10. A radio frequency module, characterized in that, include: The WLP-packaged SAW filter as described in any one of claims 1 to 9; The substrate, wherein the WLP-packaged SAW filter is mounted on the front side of the substrate, and the molded blocking area terminal, signal terminal and ground terminal of the WLP-packaged SAW filter are all soldered to the substrate; Electronic components, which are mounted on the front side of the substrate; as well as A molding compound is located on the front side of the substrate and encapsulates the WLP-packaged SAW filter and the electronic components, and the molding compound fills the sides of the molding barrier terminal, the signal terminal and the ground terminal.

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