Filter, method of improving out-of-band rejection of filter, and electronic device

Abstract

The application discloses a filter, a method for improving out-of-band suppression of the filter and electronic equipment. The filter comprises a superimposed upper wafer and lower wafer, and has an input pad, an output pad and a metal sealing ring between the upper wafer and the lower wafer. The upper wafer and the lower wafer further have a metal strip led out from the metal sealing ring, and the metal strip and a part of the metal sealing ring jointly form a first groove body or / and a second groove body with an opening. The first groove body can accommodate the input pad, and the second groove body can accommodate the output pad. The lead-out wire of a resonator in the filter passes through the opening of the groove body and is then connected to the input pad or the output pad. The application leads out the metal strip from the metal sealing ring, and makes the metal strip and a part of the metal sealing ring jointly form the groove body with the opening to accommodate the input pad or / and the output pad, so that the coupling between the input and output ports of the filter is effectively suppressed, the out-of-band suppression is improved, and the method has the advantages of simplicity and the like.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and in particular to a filter, a method for improving out-of-band rejection of a filter, and an electronic device. Background Technology

[0002] Wireless communication technology is rapidly developing towards multi-band and multi-mode operation. Filters, duplexers, and multiplexers, as key components of the radio frequency front-end, have received widespread attention, especially in the rapidly growing field of personal mobile communications. Currently, most filters and duplexers widely used in personal mobile communications are made from surface acoustic wave (SAW) resonators or bulk acoustic wave (BAW) resonators. Compared to SAW resonators, BAW resonators offer superior performance, featuring high Q-values, wide frequency coverage, and excellent heat dissipation, making them more suitable for the future development needs of 5G communication. Because the resonance of a BAW resonator is generated by mechanical waves, rather than electromagnetic waves, and the wavelength of mechanical waves is much shorter than that of electromagnetic waves, the size of BAW resonators and the filters they form are significantly smaller than that of traditional electromagnetic filters.

[0003] Although bulk acoustic wave (BAW) filters have been widely used in mobile communications, 5G communication now gives mobile terminals more functions, which poses greater challenges to radio frequency (RF) devices. These devices need to perform more complex functions while also requiring further miniaturization. As an indispensable component of RF devices, filters must adapt to market needs and become smaller. However, as filter sizes decrease, their out-of-band rejection, especially adjacent-band rejection, deteriorates, affecting their usability.

[0004] Therefore, in order to meet the needs of filter miniaturization, it is urgent to find out the reasons for the deterioration of out-of-band suppression and propose solutions when the filter size is further reduced. Summary of the Invention

[0005] In view of this, the present invention proposes a filter, a method for improving the out-of-band suppression of the filter, and an electronic device, in order to achieve the inventive objective of improving the isolation characteristics of the device.

[0006] The first aspect of the present invention provides a filter comprising an upper wafer and a lower wafer stacked together, wherein an input pad, an output pad, and a metal sealing ring are provided between the upper wafer and the lower wafer, wherein a metal strip extending from the metal sealing ring is further provided between the upper wafer and the lower wafer, the metal strip and a portion thereof forming a first groove and / or a second groove having an opening, the first groove being capable of accommodating the input pad, and the second groove being capable of accommodating the output pad, wherein the lead wire of the resonator in the filter passes through the opening and is connected to the input pad or the output pad.

[0007] Optionally, the vertical projection of the metal strip is polygonal.

[0008] Optionally, the first end of the metal strip is connected to the metal sealing ring, and the second end is left unattended or grounded through a via.

[0009] Optionally, the distance between the metal strip and the input pad is greater than 30 micrometers and less than 70 micrometers.

[0010] Optionally, the height of the metal strip forming the first groove is higher than the height of the input pad, and the height of the metal strip forming the second groove is higher than the height of the output pad.

[0011] Optionally, the width of the metal strip forming the first groove is 35% to 65% of the width of the input pad, and the width of the metal strip forming the second groove is 35% to 65% of the width of the output pad.

[0012] Optionally, the metal strip is derived from the metal sealing ring of the upper wafer; or, the metal strip is derived from the metal sealing ring of the lower wafer; or, the metal strip comprises two corresponding parts derived from the metal sealing rings of the upper wafer and the lower wafer, and the two parts are bonded together.

[0013] Optionally, the filter is a bulk acoustic wave filter.

[0014] A second aspect of the present invention provides a method for improving out-of-band rejection of a filter, the filter comprising an upper wafer and a lower wafer stacked together, wherein an input pad, an output pad, and a metal sealing ring are provided between the upper wafer and the lower wafer, the method comprising: providing a metal strip extending from the metal sealing ring and located between the upper wafer and the lower wafer, such that the metal strip and a portion of the metal sealing ring together form a first groove and / or a second groove having an opening, the first groove being capable of accommodating the input pad and the second groove being capable of accommodating the output pad, and passing a lead of a resonator in the filter through the opening of the groove and then connecting it to the input pad or the output pad.

[0015] Optionally, the filter is a bulk acoustic wave filter.

[0016] A third aspect of the present invention provides an electronic device including the filter of the present invention.

[0017] The technical solution of the present invention, by leading a metal strip out from the metal sealing ring and making the metal strip and a part of the metal sealing ring together form a groove with an opening to accommodate the input pad and / or output pad, helps to suppress the coupling between the input and output ports of the filter, thereby helping to improve out-of-band rejection, and has the advantages of being simple and easy to implement. Attached Figure Description

[0018] For illustrative and not limiting purposes, the invention will now be described with reference to preferred embodiments thereof, particularly the accompanying drawings, in which:

[0019] Figure 1 This is a schematic diagram of the layout and packaging of existing bulk acoustic wave filters.

[0020] Figure 2 for Figure 1 The diagram shows the electric field distribution of the input and output pads after an RF signal is applied to the input pads of the bulk acoustic wave filter.

[0021] Figure 3 for Figure 2 Further equivalent circuit diagram;

[0022] Figure 4 for Figure 1 The final equivalent circuit diagram of the layout;

[0023] Figure 5 For is Figure 4 Further equivalent circuit diagram;

[0024] Figure 6 This is a schematic diagram of the layout and packaging of a bulk acoustic wave filter according to a first embodiment of the present invention;

[0025] Figure 7 for Figure 6 The diagram shows the electric field distribution of the input and output pads after an RF signal is applied to the input pads of the bulk acoustic wave filter.

[0026] Figure 8 for Figure 7 Further equivalent circuit diagram;

[0027] Figure 9 for Figure 6 The final equivalent circuit diagram of the layout;

[0028] Figure 10 yes Figure 9 Further equivalent circuit diagram;

[0029] Figure 11 The graph shows a comparison of simulation test results between existing filters and the filter of this invention.

[0030] Figure 12 This is a schematic diagram of the layout and packaging of a bulk acoustic wave filter according to a second embodiment of the present invention. Detailed Implementation

[0031] The layout and packaging of existing bulk acoustic wave filters are as follows: Figure 1 In the diagram, 12 is the wafer on which the resonator is manufactured, and 11 is the packaging substrate. There is another wafer between wafer 12 and the packaging substrate 11, serving as a protective cover; this wafer is not shown for clarity. Figure 1 As shown, the lower surface of wafer 12 is fabricated with a metal sealing ring 13, series resonators S1, S2, S3, S4, and parallel resonators P1, P2, P3, as well as input pads int and output pads out, and ground pins G1, G2, G3. Series resonator S1 is connected to the input pad, series resonator S4 is connected to the output pad, and ground pins G1, G2, G3 are connected to parallel resonators P1, P2, P3 respectively. G3 is also connected to the metal sealing ring 13 and then to the ground of the substrate 11 through a metal via 14.

[0032] Figure 2 This is a diagram showing the electric field distribution of the input and output pads of a conventional bulk acoustic wave filter after an RF signal is applied to the input pads. For simplicity, all resonators are not shown. Since the metal sealing ring 23 is connected to the ground of the substrate 21 through the via 24, the metal sealing ring 23 has a partial ground function. The input pad will form an electric field distribution as shown in Figure 25 on both sides (top and left) near the metal sealing ring. The electric field distribution on the lower right side of the input pad is shown in Figure 26, with a large coverage area. This is mainly because there is no reference ground on the right side, and it can only refer to the ground on the substrate. Since the distance between the substrate and the wafer 22 is much greater than the distance between the input pad and the metal sealing ring 23, the electric field coverage area on the lower right side of the input pad is much greater than the electric field coverage area on the left and top sides of the input pad. Similarly, the same is true for the output pad. There is no reference ground on its upper left side, and it can only refer to the ground on the substrate. Therefore, the electric field distribution on the upper left side of the output pad is shown in Figure 28, with a large coverage area. As a result, the electric fields 26 and 28 between the input pad and the output pad will overlap, thus forming a capacitive coupling. This coupling capacitance seriously affects the out-of-band rejection of the filter. It should be noted that the strength of capacitive coupling between the input pad and the output pad is related to the distance between them. Currently, the trend is to reduce the size of the filter, so the distance between the input pad and the output pad will become smaller and smaller, and the coupling will inevitably become larger and larger.

[0033] Figure 3 for Figure 2 A further equivalent circuit is provided, wherein the electric field effect between the input pad and the sealing ring 23 is equivalent to a capacitor C1, the electric field effect between the output pad and the sealing ring 23 is equivalent to a capacitor C2, the electric field effect between the input pad and the output pad is equivalent to a capacitor C3, and the sealing ring can be partially equivalent to inductors L1 and L2. Figure 4 for Figure 1 The final equivalent circuit diagram of the layout, such as Figure 4 As shown, circuit A in the diagram consists of parasitic inductance and capacitance introduced by the layout. It is connected in parallel between the input and output of the filter and comprises two parallel branches. One branch contains only capacitor C3, while the other branch contains C1, C2, and parasitic inductors L1 and L2. The physical meanings of the parasitic capacitors C1, C2, C3, and parasitic inductors L1 and L2 have been explained above and will not be elaborated further. Analysis reveals that capacitor C3 is the most significant factor contributing to the deterioration of the filter's out-of-band rejection because it directly bridges the input and output, thus having the greatest impact. The series branches composed of C1 and L1 and C2 and L2 are grounded through a common node O. In fact, from a grounding perspective, this common ground point can be divided into two independent grounding points; that is, the series branches of C1 and L1 and C2 and L2 can be grounded independently. Figure 5 yes Figure 4 Further equivalent circuit, from Figure 5 It can be seen that capacitor C3 is directly connected between the input and output, which is the main factor causing the filter's out-of-band rejection to deteriorate.

[0034] To eliminate the influence of capacitor C3 and improve out-of-band rejection, this invention proposes a filter that, based on existing filters, extends a metal strip from a metal sealing ring to form an open groove to accommodate the input pad and / or output pad, thereby effectively suppressing coupling between the filter's input and output ports and improving out-of-band rejection. The following examples provide a detailed description.

[0035] Example 1

[0036] Figure 6 This is a schematic diagram of the bulk acoustic wave filter layout and packaging form according to the first embodiment of the present invention. Figure 6 and Figure 1Compared to the previous version, the packaging form remains the same, but the layout has been improved. 32 is the wafer with the resonators, 31 is the packaging substrate, and there is another wafer between wafer 32 and the packaging substrate 31, serving as a protective cover; this wafer is not shown for clarity. The lower surface of wafer 32 has series resonators S1, S2, S3, S4 and parallel resonators P1, P2, P3, as well as input pads (int) and output pads (out). It also has ground pins G1, G2, G3, a metal sealing ring 33, and metal strips 35 and 36 extending from the sealing ring 33. The metal strips 35 and 36 and the metal sealing ring 33 form two open slots, labeled as slot 1 and slot 2, respectively. The input pad is placed in slot 1, and the output pad is placed in slot 2. It should be noted that in other embodiments of the present invention, it is not necessarily required to set two metal strips 35 and 36 at the same time to form two grooves. Instead, only metal strip 35 or metal strip 36 can be set to form only the first groove 1 or the second groove 2. However, the technical effect of suppressing coupling and improving out-of-band suppression is slightly weaker.

[0037] Metal strips 35 and 36 can be polygonal, but elongated strips are preferred. The distance between metal strips 35 and 36 and the edge of the input or output pad should be greater than 30µm and less than 70µm. If this distance is too large, the suppression effect will deteriorate; if the distance is too small, the introduced capacitance will increase, affecting matching. Additionally, the height of metal strips 35 and 36 should be higher than the corresponding pad height to ensure that the input or output pad is completely enclosed within the corresponding slot. In practice, the input and output pad heights are usually equal, and the heights of all metal strips and metal sealing rings are also equal. Therefore, it is sufficient that the heights of the metal strips and metal sealing rings are greater than the pad height. The width of metal strip 35 forming the first slot 1 can be 35% to 65% of the input pad width, and the width of metal strip forming the second slot 2 can be 35% to 65% of the output pad width. If the metal strip width is too large, it occupies too much area; if the width is too small, it deteriorates out-of-band suppression. Since the two slots are not completely closed, the lead wire of the series resonator S1 passes through the opening of the first slot 1 and connects to the input pad, and the lead wire of the series resonator S4 passes through the opening of the second slot 2 and connects to the output pad. The ground pins G1, G2, and G3 are connected to the parallel resonators P1, P2, and P3 respectively. At the same time, G3 is also connected to the metal sealing ring 33 and then connected to the ground of the substrate 31 through the metal via 34.

[0038] Figure 7 for Figure 6The diagram shows the electric field distribution of the input and output pads after an RF signal is applied to the input pads of the bulk acoustic wave filter. For simplicity, all resonators are not shown. Since the metal sealing ring 43 is connected to the ground of the substrate 41 through the via 44, it partially functions as a ground. Correspondingly, the metal strips 45 and 46, being connected to the metal sealing ring 43, also partially function as grounds. The input pads are located in the first groove 1, which consists of the two sides of the metal sealing ring 43 and the metal strip 45. Therefore, the electric field distribution of the input pads is as follows: Figure 7 As shown, an electric field distribution as shown in Figure 47 is formed near the upper and left sides of the metal sealing ring. The electric field distribution on the right side of the input pad is shown in Figure 48, with a smaller coverage area. This is mainly because the metal strip 45 on the right side serves as a reference ground, confining the electric field to a smaller region. Similarly, the same applies to the output pad. The electric field distribution near the lower and right sides of the metal sealing ring is shown in Figure 49, with a smaller coverage area on the left side of the output pad, as shown in Figure 50. This is mainly because the metal strip 46 on the left side serves as a reference ground, confining the electric field to a smaller region. Therefore, the electric fields 48 and 50 between the input and output pads do not overlap, thus eliminating coupling.

[0039] Figure 8 for Figure 7 A further equivalent circuit diagram is provided, in which the electric field effect between the input pad and the sealing ring 43 is equivalent to a capacitor C1, the electric field effect between the input pad and the metal strip 45 is equivalent to a capacitor C31, the electric field effect between the output pad and the sealing ring 43 is equivalent to a capacitor C2, the electric field effect between the output pad and the metal strip 46 is equivalent to a capacitor C32, and the sealing ring can be partially equivalent to inductors L1 and L2. Figure 9 for Figure 6 The final equivalent circuit diagram of the layout, as shown below. Figure 9 As shown, circuit B consists of parasitic inductance and capacitance introduced by the layout. It is connected in parallel between the input and output of the filter. Circuit B comprises two parts: the left part consists of capacitors C1 and C31 connected in parallel and in series with inductor L1, with one end connected to the filter input and the other end grounded through the common terminal O. Similarly, the right part consists of capacitors C2 and C32 connected in parallel and in series with inductor L2, with one end connected to the filter output and the other end grounded through the common terminal O. The physical meanings of the parasitic capacitors C1, C2, C31, and C32, as well as the parasitic inductors L1 and L2, have been explained above and will not be repeated here. In fact, from a grounding perspective, this common ground point O can be divided into two independent grounding points. Figure 10 yes Figure 9 A further equivalent circuit diagram is shown. For example... Figure 10As shown, the parasitic circuit E, composed of capacitors C1 and C31 and inductor L1, is only connected in parallel at the input port, and the parasitic circuit F, composed of capacitors C2 and C32 and inductor L2, is only connected in parallel at the output port. No capacitor is directly connected between the input and output ports. Therefore, theoretically speaking, Figure 6 The layout shown can effectively suppress coupling between the filter's input and output ports, improving out-of-band rejection.

[0040] To verify the effectiveness of the technology, the inventors designed a WIFI filter and conducted simulation comparison tests between existing filters and the filter using the technology of this invention. The results are as follows: Figure 11 As shown. Figure 11 The medium-thick solid lines represent the simulation results of the schematic diagram, i.e., the result with only the filter and no parasitic capacitance or inductance; the thin solid lines represent the results obtained using... Figure 6 The results of the filter embodiment with the layout method are shown in the figure. The dashed lines represent the layout method adopted. Figure 1 The results of the filter comparison based on the layout method. From Figure 11 As can be seen from the comparison example, the parasitic capacitor C3 is directly connected across the input and output terminals, which seriously affects the out-of-band rejection on the right side of the filter. However, the filter embodiment using the technical solution of this invention can effectively remove the influence of the parasitic capacitor C3, making its simulation results highly consistent with the simulation results of the schematic diagram.

[0041] Example 2:

[0042] Figure 12 This is a schematic diagram of the layout and packaging of a bulk acoustic wave filter according to a second embodiment of the present invention. Figure 12 and Figure 6 Compared to Example 1, the packaging form remains the same, but the layout is further improved. The main difference between Example 2 and Example 1 lies in the metal strips 55 and 56 extending from the metal sealing ring 53. One end of metal strip 55 is connected to the metal sealing ring 53, and the other end is connected to the ground of the substrate 51 through via 57. Similarly, one end of metal strip 56 is connected to the metal sealing ring 53, and the other end is connected to the ground of the substrate 51 through via 58. This further confines the electric field of the input and output pads within the two slots, further improving the out-of-band rejection of the filter. In addition, since one end of metal strips 55 and 56 is directly grounded, the heat dissipation capacity can be further improved, thereby increasing the power capacity of the filter.

[0043] It should be noted that although in Embodiments 1 and 2, the metal strip is derived from the metal sealing ring of the upper wafer, this is merely an example and not a limitation. In other embodiments of the present invention, the metal strip may also be derived from the metal sealing ring of the lower wafer. This metal strip does not contact the upper wafer, and there is a small gap between them. However, since the metal strip is still near the input or output pads, it can still function. In some other embodiments of the present invention, the metal strip includes two corresponding parts derived from the metal sealing rings of the upper and lower wafers, and these two parts are bonded together. After these two parts of the metal strip are joined, they form a silicon pillar and a metal "wall".

[0044] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A filter comprising an upper wafer and a lower wafer stacked together, wherein the upper wafer and the lower wafer have an input pad, an output pad, and a metal sealing ring between them, characterized in that, Between the upper wafer and the lower wafer, there is also a metal strip extending from the metal sealing ring. The metal strip and a portion of the metal sealing ring together form a first groove and / or a second groove with an opening. The first groove can accommodate the input pad, and the second groove can accommodate the output pad. The lead wire of the resonator in the filter passes through the opening and is then connected to the input pad or the output pad. The distance between the metal strip and the input pad is greater than 30 micrometers and less than 70 micrometers.

2. The filter according to claim 1, characterized in that, The vertical projection of the metal strip is polygonal.

3. The filter according to claim 1, characterized in that, The first end of the metal strip is connected to the metal sealing ring, and the second end is either left unattended or grounded through a via.

4. The filter according to claim 1, characterized in that, The height of the metal strip forming the first groove is higher than the height of the input pad, and the height of the metal strip forming the second groove is higher than the height of the output pad.

5. The filter according to claim 1, characterized in that, The width of the metal strip forming the first groove is 35% to 65% of the width of the input pad, and the width of the metal strip forming the second groove is 35% to 65% of the width of the output pad.

6. The filter according to claim 1, characterized in that, The metal strip is derived from the metal sealing ring of the upper wafer; or, The metal strip originates from the metal sealing ring of the lower wafer; or, The metal strip comprises two corresponding parts derived from the metal sealing rings of the upper wafer and the lower wafer, and the two parts are bonded together.

7. The filter according to any one of claims 1 to 6, characterized in that, The filter is a bulk acoustic wave filter.

8. A method for improving out-of-band rejection of a filter, the filter comprising a stacked upper wafer and a lower wafer, wherein the upper wafer and the lower wafer have input pads, output pads, and a metal sealing ring, characterized in that, The method includes: setting a metal strip extending from the metal sealing ring and located between the upper wafer and the lower wafer, such that the metal strip and a portion of the metal sealing ring together form a first groove and / or a second groove with an opening, the first groove being capable of accommodating the input pad and the second groove being capable of accommodating the output pad; passing the lead wire of the resonator in the filter through the opening of the groove and then connecting it to the input pad or the output pad; The metal strip is at a distance from the input. The distance between the pads is greater than 30 micrometers and less than 70 micrometers.

9. The method according to claim 8, characterized in that, The filter is a bulk acoustic wave filter.

10. An electronic device, characterized in that, The filter includes any one of claims 1 to 7.

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