Voltage-controlled oscillator, packaging structure and communication equipment

Abstract

The utility model relates to a voltage-controlled oscillator, a packaging structure and communication equipment. The piezoelectric oscillator comprises a bulk acoustic wave resonator and other circuit modules; the bulk acoustic wave resonator is arranged on the first substrate and is provided with a structural functional layer, the other circuit modules are arranged on the second substrate, the first substrate and the second substrate are stacked, and a first gap is formed between the structural functional layer and the first surface of the second substrate; the bulk acoustic wave resonator on the first substrate is electrically connected with the other circuit modules on the second substrate through the electric connection assembly in the three-dimensional direction; and the sealing assembly comprises a first sealing assembly, and the first sealing assembly wraps the first gap.

Description

Technical Field

[0001] The utility model relates to electronic technology, and more specifically to a voltage-controlled oscillator, a packaging structure and communication equipment. Background Art

[0002] Voltage controlled oscillator (VCO) is a basic component in application circuits based on controllable signals with varying frequencies. It is an oscillator controlled by input voltage. Adjusting the tuning voltage within the entire adjustable range can proportionally change the output RF signal of the voltage controlled oscillator. Voltage controlled oscillators are widely used in the fields of communications, electronics, aerospace, and medical equipment.

[0003] In order to improve the stability of the voltage-controlled oscillator in its design, one technology is to provide the voltage-controlled oscillator circuit with a bulk acoustic wave resonator, such as a film bulk acoustic wave resonator (FBAR) type, to meet the high constraints of stability, phase noise and power consumption at high frequencies, so as to be compatible with current mobile communication systems.

[0004] The existing packaging structure of the voltage-controlled oscillator is to form a thin film bulk acoustic wave resonator separately on a chip substrate, and other circuit elements in the voltage-controlled oscillator circuit (such as a CMOS amplifier) ​​are formed on another chip substrate. The two chips are placed on a printed circuit board, and electrical signals are transmitted between the two chips through wires. However, the packaging structure of the above-mentioned voltage-controlled oscillator is large in size, and the packaging method using wire bonding is costly and complex in process. Therefore, the industry expects to develop a packaging structure of a voltage-controlled oscillator with small size, low cost and simple process. Utility Model Content

[0005] The utility model has carefully designed the packaging structure of the voltage-controlled oscillator and successfully developed a packaging structure of the voltage-controlled oscillator that can solve the above-mentioned technical problems.

[0006] A brief overview of the present invention will be given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is simply to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0007] According to one aspect of the utility model, a packaging structure of a voltage-controlled oscillator is provided, wherein the piezoelectric oscillator includes a bulk acoustic wave resonator and other circuit modules; the bulk acoustic wave resonator is arranged on a first substrate and has a structural functional layer, and the other circuit modules are arranged on a second substrate, the first substrate and the second substrate are stacked, and a first gap is provided between the structural functional layer and the first surface of the second substrate; an electrical connection component in a three-dimensional direction, the bulk acoustic wave resonator on the first substrate and the other circuit modules on the second substrate are electrically connected through the electrical connection component; a sealing component, the sealing component includes a first sealing component, and the first sealing component covers the first gap.

[0008] Furthermore, a second sealing component is further included between the first surface of the first substrate and the first surface of the second substrate.

[0009] Further, the lead terminals in the electrical connection assembly are led out from the first substrate side and / or the lead terminals in the electrical connection assembly are led out from the second substrate side.

[0010] Furthermore, a first gap between the structural functional layer and the first surface of the second substrate is constructed by combining the first bump and the second bump in the electrical connection assembly.

[0011] Furthermore, the sealing component covering the first gap has a flat surface, and the sealing component includes a first sealing layer or a second sealing layer.

[0012] Furthermore, the sealing component covering the first gap has a flat surface, and the sealing component includes a first sealing layer and a second sealing layer.

[0013] Furthermore, the BAW resonator is a thin film BAW resonator, the structural functional layer includes a first electrode, a piezoelectric layer and a second electrode stacked on the first surface of the first substrate, and the thin film BAW resonator also includes a sound reflection area formed in the first substrate or on the first surface of the first substrate.

[0014] Furthermore, the first substrate and the second substrate form a first intermediate structure through an electrically connected component structure, in which the first surface of the first substrate and the first surface of the second substrate are arranged relative to each other, and the first gap, the structural functional layer, the sound reflection area and other circuit modules have at least overlapping projection areas on the first surface of the first substrate, the first sealing layer conformally covers the first intermediate structure, and the second sealing layer covers the first sealing layer and has a flat surface.

[0015] According to another aspect of the present invention, a voltage-controlled oscillator is provided, and the voltage-controlled oscillator includes the aforementioned packaging structure.

[0016] According to another aspect of the present invention, a communication device is provided, wherein the communication device comprises the packaging structure of any one of the voltage-controlled oscillators described above.

[0017] The utility model can meet the high constraints of stability, phase noise and power consumption at high frequencies in terms of electrical performance through the design of the packaging structure of the voltage-controlled oscillator, conforms to the development trend of device miniaturization in terms of structure, and has low cost and simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The specific contents of the utility model are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the utility model. The accompanying drawings are only for illustrating the principles of the utility model. The sizes and relative positions of the units in the accompanying drawings do not need to be drawn in proportion.

[0019] Figure 1 A schematic diagram of the circuit structure of the voltage-controlled oscillator provided by the utility model is shown;

[0020] Figure 2 The present invention shows a packaging structure of a voltage-controlled oscillator;

[0021] Figure 3 The first variation of the voltage-controlled oscillator packaging structure of the utility model is shown;

[0022] Figure 4 A second variation of the voltage-controlled oscillator packaging structure of the present invention is shown. DETAILED DESCRIPTION

[0023] Below, exemplary disclosures of the present invention will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of implementing the present invention are described in the specification. However, it should be understood that many decisions specific to the present invention may be made in the process of developing any such implementation of the present invention in order to achieve the specific goals of the developer, and these decisions may vary from one utility model to another.

[0024] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure closely related to the solution according to the present invention is shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0025] It should be understood that the present invention is not limited to the described embodiments due to the following description with reference to the accompanying drawings. In the present invention, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment, if feasible.

[0026] <Voltage Controlled Oscillator Circuit Structure>

[0027] See also Figure 1 , Figure 1 The circuit structure diagram of the voltage-controlled oscillator provided by the utility model is shown.

[0028] like Figure 1 As shown, the voltage-controlled oscillator includes a bulk acoustic wave resonator and other circuit modules. The other circuit modules include a first module, a second module, a bulk acoustic wave resonator, a third module and a fourth module.

[0029] The first module is composed of a first resistor R1 and a second resistor R2 connected in series. It can be understood that the first resistor R1 and the second resistor R2 can also be replaced by components such as varactor diodes. The first module is connected in parallel with the bulk acoustic wave resonator B1. The control voltage can be input to the connection node between the second end of the first resistor R1 and the second end of the second resistor R2.

[0030] The second module is coupled in parallel with the first module, and the power supply voltage is applied to the second module.

[0031] The second module includes two identical first current sources CU1 and second current sources CU2, wherein a first end of the first current source CU1 is connected to a power supply voltage VDD, and a second end of the first current source CU1 is connected to a first end of a first resistor R1. A first end of the second current source CU2 is connected to a power supply voltage VDD, and a second end of the second current source CU2 is connected to a first end of a second resistor R2.

[0032] The third module is connected in parallel with the bulk acoustic wave resonator B1. The third module includes a first differential transistor T1, a second differential transistor T2, a capacitor Cs, a third transistor T3 and a fourth transistor T4. The first differential transistor T1, the second differential transistor T2, the third transistor T3 and the fourth transistor T4 can be exemplarily field effect transistors. The gate of the first differential transistor T1 is connected to the source of the second differential transistor T2, and the source of the first differential transistor T1 is connected to the first end of the bulk acoustic wave resonator B1. The gate of the second differential transistor T2 is connected to the source of the first differential transistor T1, and the source of the second differential transistor T2 is connected to the second end of the bulk acoustic wave resonator B1. The first end of the capacitor Cs is connected to the drain of the first differential transistor T1, and the second end of the capacitor Cs is connected to the drain of the second differential transistor T2. The capacitor Cs can be used to avoid blocking the first differential transistor T1 and the second differential transistor T2. The source end of the third transistor T3 is connected to the first end of the capacitor Cs, and the source end of the fourth transistor T4 is connected to the second end of the capacitor Cs. The drain of the third transistor T3 is grounded, the drain of the third transistor T3 is grounded, and the gate of the third transistor T3 is connected to the gate of the fourth transistor T4.

[0033] The fourth module includes an operational amplifier A1, wherein the non-inverting input terminal of the operational amplifier A1 is connected to a connection node between the second end of the first resistor R1 and the second end of the second resistor R2, the inverting input terminal is connected to a reference power supply, and the output terminal is connected to the gate of the third transistor T3 and to the gate of the fourth transistor T4.

[0034] <Voltage Controlled Oscillator Package Structure>

[0035] See also Figure 2 , according to the circuit structure of the voltage-controlled oscillator, Figure 2 The invention shows a packaging structure of a voltage-controlled oscillator.

[0036] The packaging structure of the voltage-controlled oscillator includes a first substrate 1000, a second substrate 4000, an electrical connection component and a sealing component. The first substrate 1000 can be any substrate compatible with semiconductor technology, such as a bulk silicon substrate, glass, sapphire, SiGe, SiC, SiGeC, TnAs, GaAs, InP or other III-group and V-group compound semiconductors, and can also include a multilayer structure formed by these semiconductors, or silicon on insulator (SOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or can also be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or can also be a ceramic substrate such as alumina, a quartz or glass substrate, etc.

[0037] The bulk acoustic wave resonator in the voltage-controlled oscillator is arranged on the first substrate 1000. Specifically, the sound reflection region 1100 formed in or on the first substrate 1000 is exemplarily formed by a cavity. The first electrode 2100, the piezoelectric layer 2200, and the second electrode 2300 are sequentially stacked on the first substrate 1000 in a direction away from the first surface of the first substrate 1000. The first electrode 2100, the piezoelectric layer 2200, and the second electrode 2300 constitute the structural functional layers of the bulk acoustic wave resonator.

[0038] The material of the first electrode 2100 is a conductive material, which may be a metal material having conductive properties, such as one or more of Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo and W.

[0039] The material of the piezoelectric layer 2200 is a piezoelectric material. The piezoelectric material is a crystalline material that will generate a voltage between the two end faces when subjected to pressure. The piezoelectric effect of the piezoelectric material can realize the mutual conversion of mechanical vibration (sound wave) and alternating current, thereby realizing the conversion of sound energy and electrical energy. The material of the piezoelectric layer 2200 may include at least one of the following: piezoelectric materials with a wurtzite-type crystal structure such as ZnO, AlN, GaN, aluminum zirconate titanate or lead titanate; optionally, a certain proportion of rare earth element impurities such as scandium, erbium, yttrium, lanthanum, etc. may be doped into the above materials. Exemplarily, the material of the piezoelectric layer 2200 includes AlN doped with scandium.

[0040] The material of the second electrode 2300 is a conductive material. The conductive material may be a metal material having conductive properties, for example, one or more of Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo and W. The materials of the first electrode 2100 and the second electrode 2300 may be the same or different.

[0041] Further, an electrical connection component is formed on the first surface of the first substrate 1000 for transmitting the electrical signal of the bulk acoustic wave resonator. An exemplary electrical connection component includes a first pad 1200 for serving as an input port and an output port of the electrical signal. And a second pad 1300 in the electrical connection component is also formed on the upper surface of the first substrate 1000. The first surface of the first pad 1200, the first surface of the second pad 1300 and the first surface of the first electrode 2100 are flush, and the piezoelectric layer 2200 covers the first pad 1200, the second pad 1300 and the first electrode 2100. The materials of the first pad 1200 and the second pad 1300 may include Mo / Ni / Au or Mo / TiW / Au. Among them, Ni or TiW metal as a barrier layer can effectively prevent the diffusion of Au.

[0042] Furthermore, a passivation layer 2400 may be further disposed on the second electrode 2300. The passivation layer 2400 may be used to protect the second electrode 2300 and also has a certain frequency correction effect. The material of the passivation layer 2400 may be the same as that of the piezoelectric layer 2200.

[0043] Furthermore, a first bump 3100 in the electrical connection assembly is formed on the first substrate 1000, one end of the first bump 3100 contacts the first surface of the second pad 1300, and the other end of the first bump 3100 protrudes from the first surface of the piezoelectric layer 2200. The material of the first bump 3100 can be Cu.

[0044] The second substrate 4000 can be any suitable semiconductor substrate, such as a bulk silicon substrate. The first module, the second module, the third module and the fourth module of the other circuit modules 4100 in the voltage-controlled oscillator are arranged on the second substrate 4000. A second bump 3200 (Bump) in the electrical connection component is arranged on the first surface of the second substrate 4000. The material of the second bump 3200 can include but is not limited to Cu. Further, the second bump 3200 can further include a first spacer layer 3300, and the first spacer layer 3300 is selected to be a metal that plays a role of spacing protection, such as nickel.

[0045] The first surface of the first substrate 1000 and the first surface of the second substrate 4000 are arranged opposite to each other, and the first bump 3100 on the first substrate 1000 and the second bump 3200 on the second substrate 4000 are joined by the solder 3400 or the first bump 3100 and the second bump 3200 on the first substrate 1000 are joined by the solder 3400 and the spacer layer 3300, so that the second substrate 4000 is stacked on the first substrate 1000. The solder 3400 can be made of SnAg material. The first bump 3100 and the second bump 3200 in the joined electrical connection assembly can form a conductive connection between the first substrate 1000 and the second substrate 4000 on the one hand, and can construct a first gap 2500 between the structural functional layer and the first surface of the second substrate 4000 on the other hand, so as to provide a working space for the BAW resonator. The first gap 2500, the structural functional layer and the sound reflection area 1100 have at least overlapping projection areas on the first surface of the first substrate 1000, thereby forming a first intermediate structure of the voltage-controlled oscillator packaging structure, that is, in the first intermediate structure, the first surface of the first substrate and the first surface of the second substrate are arranged relatively to each other, and the first gap, the structural functional layer, the sound reflection area and other circuit modules have at least overlapping projection areas on the first surface of the first substrate.

[0046] The sealing assembly is formed on the first intermediate structure. The sealing assembly includes a first sealing assembly, which may include a first sealing layer 5100. The first sealing layer 5100 conformally covers the first intermediate structure and covers and seals the first gap 2500. The material of the first sealing layer 5100 may be a material with poor fluidity, which will not flow between the first substrate 1000 and the second substrate 4000 during the lamination process. Exemplarily, the first sealing layer 5100 may be a dry film. The first sealing layer 5100 covers a portion of the first surface of the first substrate 1000 and the second surface of the second substrate 4000 at the same time.

[0047] Further, the first sealing component also includes a second sealing layer 5200 further covered on the first sealing layer 5100. The second sealing layer 5200 can be made of a material that is not easily affected by water vapor, temperature, impurities, etc., and can achieve composite functions such as thermal conductivity, insulation, moisture resistance, pressure resistance, and support. Exemplarily, the second sealing layer 5200 can be made of epoxy resin molding compound EMC. The material thickness of the second sealing layer 5200 can be adjusted to form the surface of the second sealing layer 5200 away from the first surface of the second substrate 4000 into a flat surface.

[0048] A first through hole is formed in the first substrate 1000, and a first conductive column 3500 in the electrical connection component is formed in the first through hole, and the first conductive column 3500 is electrically connected to the first pad 1200. A redistribution layer (not shown in the figure) in the electrical connection component is arranged on the second surface of the first substrate 1000, and a third sealing layer 5300 in the sealing component is formed, and the third sealing layer 5300 covers the redistribution layer, and a second through hole is formed in the third sealing layer 5300, and a second conductive column 3600 in the electrical connection component is formed in the second through hole, and a third bump 3700 in the electrical connection component is formed on the second conductive column 3600 or a second conductive column 3600 is formed in the second through hole, and a second spacer layer 3800 and a third bump 3700 in the electrical connection component are formed on the second conductive column 3600, thereby completing the packaging structure of the voltage-controlled oscillator. Among them, the second conductive column 3600 is preferably a metal with excellent conductive properties, such as copper, so as to better transmit electrical signals. The third bump 3700 can be made of metal material with a low melting point, such as tin, lead (Pb) or aluminum, so as to facilitate melting and molding. The second spacer layer 3800 is made of a metal that plays a protective role, such as nickel, according to the materials of the second conductive column 3600 and the third bump 3700.

[0049] The utility model firstly packages the voltage-controlled oscillator in three dimensions by stacking the first substrate 1000 and the second substrate 4000, thereby avoiding the packaging of multiple discrete devices of the voltage-controlled oscillator in two dimensions in the prior art, and effectively reducing the volume of the voltage-controlled oscillator; and by making the first substrate 1000 and the second substrate 4000 mutually sealed structures, it is not necessary to set a cover structure for each of the first substrate 1000 and the second substrate 4000, thereby further saving costs and simplifying the process flow compared with the prior art. By setting the electrical connection components in three dimensions, the first substrate and the second substrate are electrically connected. The transmission wiring on the subsequent package printed board can be reduced, and the area occupied by the voltage-controlled oscillator on the package printed board can be further reduced.

[0050] See also Figure 3 , Figure 3 FIG. 1 shows a first variation of the voltage-controlled oscillator packaging structure of the present utility model. Figure 3 As shown, in the packaging structure of the voltage-controlled oscillator, after the first intermediate structure is formed, a first sealing component is formed on the first intermediate structure, and the first sealing component may only include a first sealing layer 5100, and the thickness of the first sealing layer is adjusted, and the first sealing layer 5100 is formed into a flat surface on the surface of the first surface away from the second substrate 4000 by shaping, thereby completing the protection of the first intermediate structure, and then a first through hole is formed in the first sealing layer 5100 corresponding to the first pad 1200, and a first conductive column 3500 is formed in the first through hole, and the first end face of the first conductive column 3500 is electrically connected to the first pad 1200. A redistribution layer 3900 is also formed in the first sealing layer 5100, and the redistribution layer 3900 is electrically connected to the first conductive column 3500. A second through hole is also formed in the first sealing layer 5100, and a second conductive column 3600 is formed in the second through hole. A third bump 3700 is formed on the second conductive column 3600 or a second conductive column 3600 is formed in the second through hole, and a second spacer layer 3800 and a third bump 3700 are formed on the second conductive column 3600, thereby completing the packaging structure of the voltage-controlled oscillator.

[0051] See also Figure 4 , Figure 4 FIG. 2 shows a second variation of the voltage-controlled oscillator packaging structure of the present invention. Figure 4 As shown, the difference between the second variant and the aforementioned embodiment is that: in addition to the various structural features of the bulk acoustic wave resonator formed on the first substrate 1000, the first pad 1200 is formed on the first pad 1200, and the second sealing component in the sealing component is formed on the first pad 1200. The second sealing component includes an annular first sealing ring 5400. The material of the first sealing ring 5400 can be the same as the material of the first bump 3100. And a second sealing ring 5500 in the second sealing component is formed at a position opposite to the first sealing ring 5400 on the first surface of the second substrate 4000. Then the first substrate 1000 and the second substrate 4000 are joined by solder to form a second intermediate structure. The material of the second sealing ring 5500 can be the same as the material of the first sealing ring 5400. Through the combination of the first sealing ring 5400 and the second sealing ring 5500, the sealing component between the first substrate and the second substrate is obtained to cooperate with the sealing effect of the first substrate 1000 and the second substrate 4000, thereby protecting the various features of the voltage-controlled oscillator from being affected by water vapor, temperature, impurities, etc.

[0052] Then, a second sealing layer 5200 is formed on the second intermediate structure. The second sealing layer 5200 may be made of a material that is not easily affected by water vapor, temperature, impurities, etc., and has composite functions such as thermal conductivity, insulation, moisture resistance, pressure resistance, and support. Exemplarily, the second sealing layer 5200 may be made of epoxy molding compound EMC. The material thickness of the second sealing layer 5200 may be adjusted to form the second sealing layer 5200 into a flat surface.

[0053] A first through hole is formed in the first substrate 1000, a second conductive column 3600 is formed in the first through hole, and the second conductive column 3600 is electrically connected to the second pad 1300. A redistribution layer (not shown) is provided on the second surface of the first substrate 1000, and a third sealing layer 5300 is formed, the third sealing layer 5300 covers the redistribution layer, a second through hole is formed on the redistribution layer in the third sealing layer, a second conductive column 3600 is formed in the second through hole, a third bump 3700 is formed on the second conductive column 3600, or a second conductive column 3600 is formed in the second through hole, a second spacer layer 3800 and a third bump 3700 are formed on the second conductive column 3600, thereby completing the packaging structure of the voltage-controlled oscillator. Among them, the first conductive column 3500 and the second conductive column 3600 are preferably made of metal with excellent conductive properties, such as copper, so as to better transmit electrical signals. The bump can be selected from a metal material with a low melting point, such as tin, lead (Pb) or aluminum, so as to facilitate melting and molding. The spacer layer 3800 is made of a metal that plays a spacer protection role, such as nickel, according to the material of the second conductive pillar 3600 and the material of the third bump 3700 .

[0054] The filter resonant network and filter of the embodiments of the present invention can be widely used in electronic devices, and exemplary communication devices are mobile phones, personal digital assistants, electronic game devices, wearable terminals, etc.

[0055] The present invention is described above in conjunction with specific implementation schemes, but those skilled in the art should be aware that these descriptions are exemplary and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make various modifications and variations to the present invention based on the spirit and principles of the present invention, and these modifications and variations are also within the scope of the present invention.

Claims

1. A packaging structure of a voltage-controlled oscillator, characterized in that: The piezoelectric oscillator includes a bulk acoustic wave resonator and other circuit modules; The BAW resonator is arranged on a first substrate and has a structural functional layer, and other circuit modules are arranged on a second substrate, the first substrate and the second substrate are stacked, and a first gap is provided between the structural functional layer and the first surface of the second substrate; An electrical connection component in a three-dimensional direction, through which the BAW resonator on the first substrate and other circuit modules on the second substrate are electrically connected; A sealing assembly includes a first sealing assembly, wherein the first sealing assembly covers the first gap.

2. The packaging structure according to claim 1, wherein: A second sealing component is further included between the first surface of the first substrate and the first surface of the second substrate.

3. The packaging structure according to claim 1 or 2, characterized in that: The lead terminals in the electrical connection assembly are led out from the first substrate side and / or the lead terminals in the electrical connection assembly are led out from the second substrate side.

4. The packaging structure according to claim 3, characterized in that: By combining the first bump and the second bump in the electrical connection assembly, a first gap is constructed between the structural functional layer and the first surface of the second substrate.

5. The packaging structure according to claim 4, wherein: The sealing component covering the first gap has a flat surface, and the sealing component includes a first sealing layer or a second sealing layer.

6. The packaging structure according to claim 4, characterized in that: The sealing component covering the first gap has a flat surface, and the sealing component comprises a first sealing layer and a second sealing layer.

7. The packaging structure according to claim 6, wherein: The BAW resonator is a thin film BAW resonator, the structural functional layer includes a first electrode, a piezoelectric layer and a second electrode stacked on a first surface of a first substrate, and the thin film BAW resonator also includes a sound reflection area formed in the first substrate or on the first surface of the first substrate.

8. The packaging structure according to claim 7, wherein: The first substrate and the second substrate form a first intermediate structure through an electrically connected component structure, in which the first surface of the first substrate and the first surface of the second substrate are arranged opposite to each other, and the first gap, the structural functional layer, the sound reflection area and other circuit modules have at least overlapping projection areas on the first surface of the first substrate, the first sealing layer conformally covers the first intermediate structure, and the second sealing layer covers the first sealing layer and has a flat surface.

9. A voltage-controlled oscillator, characterized in that: The voltage-controlled oscillator comprises the packaging structure according to any one of claims 1 to 8.

10. A communication device, characterized in that: The communication device comprises the voltage controlled oscillator according to claim 9.

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