Radio frequency power device with variable packaging capacitor

Abstract

The invention discloses a radio frequency power device with a variable packaging capacitor, which comprises a flange and an internal matching radio frequency power chip circuit, the flange is made of a metal material, the upper surface of the flange is provided with a dielectric layer at the periphery of the internal matching radio frequency power chip circuit, and the dielectric layer is covered with a plurality of discrete metal sheets. The flanges, the dielectric layers and the metal sheets form a plurality of packaging capacitors, the flanges and the metal sheets serve as polar plates of the packaging capacitors, the dielectric layers serve as dielectric media of the packaging capacitors, and the different metal sheets are connected through the bonding wires. The input internal matching chip capacitor, the packaging capacitor arranged at the input end and the input end of the active transistor are connected through bonding wires to form a harmonic modulation circuit, and the output internal matching chip capacitor, the packaging capacitor arranged at the output end and the output end of the active transistor are connected through bonding wires to form a broadband matching circuit. The design is more flexible, the frequency range of harmonic modulation can be better expanded, the harmonic amplitude can be improved, and the performance of the device is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency power packaging, and in particular relates to a radio frequency power device with variable packaging capacitance. Background Art

[0002] RF power devices are devices used to amplify and adjust the power of RF signals. Their main function is to amplify low-power RF signals into high-power signals to meet the requirements for signal transmission distance and quality in fields such as communications and broadcasting, as well as the requirements for RF signal energy in the fields of industrial medical science. RF power devices are widely used in mobile phones, televisions, radios, radars, satellite communications, radio frequency identification, industrial heating, plasma excitation, nuclear magnetic resonance, particle accelerators and other fields.

[0003] Existing RF power devices are mostly packaged in cavity ceramic or cavity plastic, which contains internal matching RF power chip circuits, including capacitors, inductors and active transistors. Since the original impedance of the active transistors of high-power devices is very low, in order to obtain good performance, the impedance of the active transistors must be increased to a certain level through internal matching circuits. Figure 1 As shown, the input terminal g of the active transistor D increases the input impedance to a specific range through a low-pass matching network and the package capacitor C1 of the input pin, making it easier for the input terminal to obtain a good standing wave under 50Ohm conditions. This low-pass network includes bonding wire groups L1, L2 and capacitor Ci. Since the capacitance and number of the package capacitors are fixed, the frequency range and harmonic amplitude of the harmonic modulation are limited, which in turn affects the performance of the device. At the same time, in the existing RF power devices, the output terminal d of the active transistor D forms a high-pass network with the bonding wire group L4 and the first output-to-ground capacitor Co1 to balance the source-drain parasitic parameters of the active transistor. The internal matching network formed by the output terminal d of the active transistor D and the bonding wire groups L3, L5 and the second output-to-ground capacitor Co2 and the output capacitor C2 can further increase the impedance and improve the quality factor of the circuit, which is a very necessary means for high-power devices. However, due to the limitation of physical space, the second output ground capacitor Co2 can only be placed between the first ground capacitor Co1 and the output package capacitor C2, which will make the length of the output bonding wire group L3 too long, which will theoretically lead to a poor quality factor of the circuit. This will affect the bandwidth frequency response characteristics of the final amplifier. On the other hand, such a layout will cause the bonding wire groups L3 and L4 to generate mutual inductance M1, and the bonding wire groups L3 and L5 to generate mutual inductance M2, such as Figure 2 As shown, it will also affect the performance of the circuit, such as bandwidth and efficiency. Summary of the invention

[0004] In view of the above-mentioned technical problems, the present invention aims to provide a radio frequency power device with variable package capacitance, which adopts a package with variable capacitance and an internal matching radio frequency power chip circuit. The variable package capacitance at the input end is connected to the input part of the internal matching radio frequency power chip circuit through a bonding wire group to form a harmonic modulation circuit, thereby improving the efficiency of the device. The variable package capacitance at the output end is connected to the output part of the internal matching radio frequency power chip circuit through a bonding wire group to form a broadband matching circuit, and the output impedance of the device is improved, thereby improving the performance of the device.

[0005] In order to solve these problems in the prior art, the technical solution provided by the present invention is: A radio frequency power device with variable package capacitance comprises a flange and an internal matching radio frequency power chip circuit arranged on the flange, the internal matching radio frequency power chip circuit comprises an input internal matching chip capacitor, an output internal matching chip capacitor and an active transistor, the flange is made of metal material, a dielectric layer is arranged on the upper surface of the flange at the periphery of the internal matching radio frequency power chip circuit, the dielectric layer is covered with a plurality of discrete metal sheets, the flange, the dielectric layer and the plurality of metal sheets constitute a plurality of package capacitors, the flange and the plurality of metal sheets serve as plates of the package capacitors, the dielectric layer serves as a dielectric of the package capacitors, different metal sheets are connected by bonding wires to form package capacitors with different capacitance values, the input internal matching chip capacitor, the package capacitor arranged at the input end and the input end of the active transistor are connected by bonding wires to form a harmonic modulation circuit, the output internal matching chip capacitor, the package capacitor arranged at the output end and the output end of the active transistor are connected by bonding wires to form a broadband matching circuit.

[0006] In a preferred technical solution, the internal matching RF power chip circuit is arranged in the middle of the flange, and the multiple metal sheets are arranged on the edge of the flange and distributed at the input and output ends of the active transistor.

[0007] In a preferred technical solution, the dielectric layer includes a first dielectric layer and a second dielectric layer, the first dielectric layer is arranged at the input end of the active transistor, and the second dielectric layer is arranged at the output end of the active transistor.

[0008] In a preferred technical solution, the first dielectric layer and the second dielectric layer have different thicknesses and dielectric constants to form package capacitors with different capacitance values.

[0009] In the preferred technical solution, the inductance and capacitance values ​​required for the harmonic modulation circuit are calculated according to the frequency of the harmonics, and the calculation formula is as follows:

[0010] Among them, f h is the frequency of the second harmonic, L evinis the equivalent inductance of the bond wire from the input of the active transistor to the package capacitance, C pin is the equivalent input package capacitance.

[0011] In the preferred technical solution, the number of connected metal sheets, the size of the metal sheets, the thickness of the dielectric layer and the dielectric constant are obtained based on the calculated inductance and capacitance values ​​required by the harmonic modulation circuit.

[0012] In a preferred technical solution, the output internal matching chip capacitor and the bonding wire connected between the output end of the active transistor and the output internal matching chip capacitor form a high-pass network to balance the source-drain parasitic parameters of the active device.

[0013] In a preferred technical solution, the material of the metal sheet is an iron-nickel alloy.

[0014] In a preferred technical solution, the material of the dielectric layer is calcium zirconate or barium titanate.

[0015] Compared with the solutions in the prior art, the advantages of the present invention are: 1. The variable package capacitance of the RF power device can obtain different capacitance values ​​by changing the thickness and dielectric constant of the dielectric layer, the number of metal sheet connections and the size of the metal sheet. According to the frequency selection needs of the harmonics, the appropriate capacitance value can be selected to obtain the most suitable harmonic modulation circuit, that is, the input impedance of the active chip input end is increased to a specific range through a low-pass matching network and input package capacitance. Since the input package capacitance is variable and can be connected through bonding wires, an accurate harmonic modulation circuit can be formed, which can better expand the frequency range of harmonic modulation and improve the harmonic amplitude, greatly improving the performance of the device.

[0016] 2. In this structure, the bonding wire group L4 and the output ground capacitor Co form a high-pass network to balance the source-drain parasitic parameters of the active transistor and improve the quality factor of the circuit. In addition, the internal matching network formed by connecting the output end of the active chip and the variable package capacitor through the bonding wire group can further improve the impedance and improve the quality factor of the circuit. Due to the use of variable package capacitors, the second output ground capacitor is omitted, saving physical space, thus greatly shortening the length of the output bonding wire group, improving the quality factor of the circuit, and thus improving the bandwidth frequency response characteristics of the amplifier. On the other hand, such a layout will not have the bonding wire group required for the additional connection of the second output ground capacitor, so there is no mutual inductance between them, further improving the bandwidth and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the structure of an existing radio frequency high-power packaging device; Figure 2 It is a schematic diagram of an equivalent circuit of an existing radio frequency high-power packaging device; Figure 3 A schematic diagram of the structure of a radio frequency high-power packaging device according to an embodiment; Figure 4 Schematic diagram of the equivalent circuit of the radio frequency high-power packaged device of this embodiment; Figure 5 This is a schematic diagram of the layered structure of the radio frequency high-power packaging device package of this embodiment; Figure 6 It is a side view schematic diagram of the radio frequency high-power packaged device package of this embodiment; Figure 7 A schematic structural diagram of a radio frequency high-power packaging device according to another embodiment; Figure 8 A schematic structural diagram of a radio frequency high-power packaging device according to another embodiment; Fig. 9 A schematic structural diagram of a radio frequency high-power packaging device according to yet another embodiment; Fig.10 This is a diagram showing the simulation results of the output impedance of the RF high-power packaged device of this embodiment; Fig.11 This is a diagram showing the simulation results of the Q value of the internal matching circuit output of the RF high-power packaged device in this embodiment. DETAILED DESCRIPTION

[0018] The above scheme is further described below in conjunction with specific examples. It should be understood that these examples are used to illustrate the present invention and are not limited to the scope of the present invention. The implementation conditions adopted in the examples can be further adjusted according to the conditions of the specific manufacturer, and the unspecified implementation conditions are usually the conditions in conventional experiments.

[0019] Example

[0020] like Figure 3As shown, a radio frequency power device with variable package capacitance includes a flange F and an internal matching radio frequency power chip circuit arranged on the flange F, the internal matching radio frequency power chip circuit includes an input internal matching chip capacitor Ci, an output internal matching chip capacitor Co and an active transistor D, the flange F is made of metal material, a dielectric layer is arranged on the upper surface of the flange F outside the internal matching radio frequency power chip circuit, the dielectric layer is annular, and a plurality of discrete metal sheets are covered on the dielectric layer, the flange F, the dielectric layer and the plurality of metal sheets form a plurality of package capacitors (C1, C2, C3, C4, C5, C6), the flange F and the plurality of metal sheets serve as plates of the package capacitor, the dielectric layer serves as a dielectric of the package capacitor, different metal sheets are connected by bonding wires to form package capacitors with different capacitance values, the input internal matching chip capacitor Ci, the package capacitor arranged at the input end and the input end g of the active transistor are connected by bonding wires to form a harmonic modulation circuit, and the output internal matching chip capacitor Co, the package capacitor arranged at the output end and the output end d of the active transistor are connected by bonding wires to form a broadband matching circuit.

[0021] In a preferred embodiment, the internal matching RF power chip circuit is arranged in the middle of the flange F, and a plurality of metal sheets are arranged on the edge of the flange and distributed at the input and output ends of the active transistor D.

[0022] In a preferred embodiment, the dielectric layer includes a first dielectric layer De1 and a second dielectric layer De2, the first dielectric layer De1 is disposed at the input end g of the active transistor, and the second dielectric layer De2 is disposed at the output end d of the active transistor.

[0023] In a preferred embodiment, the thickness and dielectric constant of the first dielectric layer De1 and the second dielectric layer De2 are different to form package capacitors with different capacitance values.

[0024] In a preferred embodiment, the inductance and capacitance values ​​required for the harmonic modulation circuit are calculated according to the frequency of the harmonics, and the calculation formula is as follows:

[0025] Among them, f h is the frequency of the second harmonic, L evin is the equivalent inductance of the bond wire from the input of the active transistor to the package capacitance, C pin is the equivalent input package capacitance.

[0026] In a preferred embodiment, the number of connected metal sheets, the size of the metal sheets, the thickness of the dielectric layer and the dielectric constant are obtained according to the calculated inductance and capacitance values ​​required by the harmonic modulation circuit.

[0027] In a specific example, Figure 3-6As shown, a radio frequency high-power packaged device includes a package with a variable capacitor and an internally matched radio frequency power chip circuit, including a flange F, a first dielectric layer De1, a second dielectric layer De2, capacitor metal sheets C1, C2, C3, C4, C5, C6, an input pin in, and an output pin out. The first dielectric layer De1 and the second dielectric layer De2 are mounted on the flange F. The capacitor metal sheets C1, C3, C5 are mounted on the first dielectric layer De1, and the capacitor metal sheets C2, C4, C6 are mounted on the second dielectric layer De2, forming a MIM (metal-insulator-metal) capacitor with the first dielectric layer De1, the second dielectric layer De2, and the flange F below. The capacitor metal sheets C1, C2, C3, C4, C5, C6 are the upper plates of the capacitor, the flange F is the lower plate of the capacitor, and the first dielectric layer De1 and the second dielectric layer De2 are the capacitor dielectric layers between the plates.

[0028] The input pin in is directly connected to the capacitor metal sheet C3 as the input end of the signal, and the output pin out is directly connected to the capacitor metal sheet C4 as the output end of the signal.

[0029] The internal matching RF power chip circuit includes an input internal matching chip capacitor Ci, an output internal matching chip capacitor Co, an active transistor D, and bonding wire groups L1, L2, L3, L4, L5, L6, L7, and L8 connected therebetween.

[0030] like Figure 4 As shown, one end of the bonding wire group L1 is connected to the input internal matching chip capacitor Ci, one end of the bonding wire group L2 is connected to the input internal matching chip capacitor Ci, the other end of the bonding wire group L2 is connected to the input terminal g of the active transistor D, and the other end of the bonding wire group L1 is connected to the capacitor metal sheet C3. The capacitor metal sheet C3 is connected to the capacitor metal sheet C1 through the bonding wire group L8, and the capacitor metal sheet C3 can also be connected to the capacitor metal sheet C5 through the bonding wire group L5. The capacitor metal sheets C1, C3, and C5 together form an equivalent input package capacitor C pin , all the bonding wire groups L1, L2, L5, and L8 from the input terminal g of the active transistor to the package capacitor together form an equivalent inductance L evin , equivalent input package capacitance C pin and equivalent inductance L evin A harmonic modulation circuit is formed.

[0031] like Figure 4As shown, one end of the bonding wire group L4 is connected to the output terminal d of the transistor D, and the other end is connected to the output internal matching chip capacitor Co. One end of the bonding wire group L3 is connected to the output terminal d of the transistor D, and the other end is connected to the capacitor metal sheet C4. The capacitor metal sheet C4 is connected to the capacitor metal sheet C2 through the bonding wire group L7. The capacitor metal sheet C4 can also be connected to the capacitor metal sheet C6 through the bonding wire group L6. Since the distance between the bonding wire group L6 and the bonding wire group L7 is very short, the inductance formed can be ignored. Therefore, the broadband output matching circuit is composed of the drain-source parasitic capacitance Cds of the active transistor D, the bonding wire group L4, the output capacitor Co, and the equivalent output package capacitance C of the capacitor metal sheets C4, C2, and C6. pout Together formed.

[0032] Specifically, the capacitor metal sheets C1, C2, C3, C4, C5, and C6 are preferably made of iron-nickel alloy, but may also be made of other metal materials. The material of flange F is for LDMOS (laterally diffused metal oxide semiconductor) chips, and adopts CPC structure (copper-molybdenum-copper-copper), with a thermal conductivity of 220W / MK and a thermal expansion coefficient of 7.3-8.5 (10 -6 K). For GaN (gallium nitride) chips, an S-CMC structure (multilayer copper-molybdenum-copper) is used, with a thermal conductivity of 350W / MK and a thermal expansion coefficient of 12 (10 -6 K). The material of the dielectric layer is CaZrO3 (calcium zirconate) or BaTiO3 (barium titanate), or other low-loss dielectric materials.

[0033] In the structure of the present invention, since the lower plate is a flange F which is a whole piece of large metal, the relative effective area of ​​the plate is determined by the area of ​​the capacitor metal sheets C1, C2, C3, C4, C5, and C6. The distance between the plates is determined by the thickness of the first dielectric layer De1 and the second dielectric layer De2. The capacitance of the packaged capacitor composed of each metal sheet is calculated by formula (1): C = ε r ε0A / d (1) Among them, ε r is the relative dielectric constant of the insulating material between the upper and lower plates, ε0 is the vacuum dielectric constant, A is the effective area of ​​the metal sheet, and d is the distance between the plates, that is, the thickness of the dielectric layer.

[0034] As an example, the capacitor metal sheets C1, C2, C5, and C6 are designed to have the same area of ​​1.0 mm x 2.0 mm. The material of the dielectric layer is CaZrO3 (calcium zirconate), and the dielectric constant is 10~100. The typical capacitance calculation is shown in the following table (1): Dielectric layer thickness (um) Dielectric constant Capacitor design value (pF) 300 10 1.176 300 20 2.352 300 30 3.528 300 40 4.704 300 50 5.88 300 60 7.056 300 70 8.232 300 80 9.408 300 90 10.584 300 100 11.76 500 10 0.7056 500 20 1.4112 500 30 2.1168 500 40 2.8224 500 50 3.528 500 60 4.2336 500 70 4.9392 500 80 5.6448 500 90 6.3504 500 100 7.056 Table (1) The thickness and dielectric constant of the first dielectric layer De1 can be changed to obtain different capacitance values. According to the frequency selection requirements of the harmonics, the appropriate capacitance value is selected to obtain the most suitable harmonic modulation circuit, which can improve the efficiency of the power amplifier. The inductance and capacitance values ​​required for the harmonic modulation circuit are calculated by formula (2): (2) Among them, f h is the frequency of the second harmonic, L evin is the equivalent inductance of the bonding wire group from the input terminal g of the active transistor D to the package capacitors C1, C3, and C5, C pin is the equivalent capacitance of package capacitors C1, C3, and C5.

[0035] For example, if the operating frequency of the designed device is 2.5 GHz, the corresponding second harmonic frequency is 5 GHz, and the device input equivalent inductance is 0.2 nH, according to the formula, C pin The package capacitor C1 is 1.4pF, the package capacitor C5 is 1.4pF, and the package capacitor C3 is 2.4pF (its area is 1.0mmX3.4mm). The package capacitor C1 is connected through the bonding wire group L8 and the package capacitor C5 is connected through the bonding wire group L5. Figure 3 As shown. pin =1.4pF+1.4pF+2.4=5.2pF.

[0036] If the design operating frequency is 2.9GHz, the corresponding second harmonic frequency is 5.8GHz, and the device input equivalent inductance is 0.2nH, according to the formula, C pin The package capacitor C1 is 1.4pF and the package capacitor C5 is 1.4pF. The package capacitor C3 is 2.4pF (its area is 1.0mmX3.4mm). The package capacitor C1 is connected by the bonding wire group L8, as shown in Figure 7 As shown, C pin =1.4pF+2.4pF=3.8pF. The package capacitor C5 can also be connected via the bonding wire group L5, thereby achieving the purpose of flexible design of the variable capacitor.

[0037] At the output end, the bonding wire group L4 and the output ground capacitor Co form a high-pass network to balance the source-drain parasitic parameters of the active transistor D and improve the quality factor of the circuit. According to the transistors of different power levels, the thickness and dielectric constant of the second dielectric layer De2 can be changed to obtain different capacitance values. For specific capacitance calculations, please refer to Table (1). The number of connected metal sheets can also be changed, such as Figure 8As shown, according to the required capacitance, the package capacitor C2 can be connected through the bonding wire group L7, and the package capacitor C6 can also be connected through the bonding wire group L6, thereby achieving the purpose of flexible design of the variable capacitor.

[0038] This can improve the output impedance of the transistor to a suitable level, while further improving the quality factor of the circuit and the performance of the power amplifier, such as broadband, high efficiency, and high output power. According to impedance matching theory, when connecting the output capacitor metal sheet, the bonding wire group L6 and the bonding wire group L7 should be set to the shortest path to achieve the minimum inductance, which is more conducive to the broadband characteristics of impedance matching. Taking an example design as a reference, the saturation power is 360W and the operating frequency is 1.8GHz-2.2GHz. After simulation design, the results are as follows Fig.10 and Fig.11 As shown, it can be seen that the simulation results of the comprehensive impedance and Q value achieve the best effect when the output package capacitance is 11pF. A material with a dielectric thickness of 500um and a dielectric constant of 78 is used. The package capacitance C2 is 5.5pF, the package capacitance C6 is 5.5pF, and the package capacitance C2 is connected through the bonding wire group L7 and the package capacitance C6 is connected through the bonding wire group L6. The output package capacitance is 5.5pF+5.5pF=11pF.

[0039] Furthermore, if Fig. 9 As shown, more metal capacitor sheets C7, C8, C9, and C10 can be made above the dielectric layer. By connecting or disconnecting the metal capacitor sheets C7, C8, C9, and C10 through bonding wire groups L9, L10, L11, and L12, a larger capacitance and more combinations of capacitance values ​​can be obtained, which is more flexible for design.

[0040] Therefore, it can be seen from the design results that improving the package capacitance can greatly optimize the impedance and Q value of the device, thereby improving the power and efficiency of the device.

[0041] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A radio frequency power device with variable package capacitance, comprising a flange and an internal matching radio frequency power chip circuit arranged on the flange, wherein the internal matching radio frequency power chip circuit comprises an input internal matching chip capacitor, an output internal matching chip capacitor and an active transistor, characterized in that: The flange is made of metal material, and a dielectric layer is arranged on the upper surface of the flange at the periphery of the internal matching RF power chip circuit, and the dielectric layer is covered with multiple discrete metal sheets. The flange, the dielectric layer and the multiple metal sheets constitute multiple packaged capacitors, and the flange and the multiple metal sheets serve as plates of the packaged capacitors, and the dielectric layer serves as the dielectric of the packaged capacitors. Different metal sheets are connected by bonding wires to form packaged capacitors with different capacitance values. The input internal matching chip capacitor, the packaged capacitor arranged at the input end and the input end of the active transistor are connected by bonding wires to form a harmonic modulation circuit, and the output internal matching chip capacitor, the packaged capacitor arranged at the output end and the output end of the active transistor are connected by bonding wires to form a broadband matching circuit.

2. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The internal matching radio frequency power chip circuit is arranged in the middle of the flange, and the multiple metal sheets are arranged on the edge of the flange and distributed at the input and output ends of the active transistor.

3. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The dielectric layer includes a first dielectric layer and a second dielectric layer, the first dielectric layer is arranged at the input end of the active transistor, and the second dielectric layer is arranged at the output end of the active transistor.

4. The radio frequency power device with variable package capacitance according to claim 3, characterized in that: The first dielectric layer and the second dielectric layer have different thicknesses and dielectric constants to form package capacitors with different capacitance values.

5. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The inductance and capacitance values ​​required for the harmonic modulation circuit are calculated based on the harmonic frequency. The calculation formula is as follows: ； Among them, f h is the frequency of the second harmonic, L evin is the equivalent inductance of the bond wire from the input of the active transistor to the package capacitance, C pin is the equivalent input package capacitance.

6. The radio frequency power device with variable package capacitance according to claim 5, characterized in that: The number of connected metal sheets, the size of the metal sheets, the thickness of the dielectric layer and the dielectric constant are obtained according to the calculated inductance and capacitance values ​​required by the harmonic modulation circuit.

7. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The output internal matching chip capacitor and the bonding wire connected between the output end of the active transistor and the output internal matching chip capacitor form a high-pass network to balance the source-drain parasitic parameters of the active device.

8. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The material of the metal sheet is iron-nickel alloy.

9. The radio frequency power device with variable package capacitance according to claim 1, characterized in that: The material of the dielectric layer is calcium zirconate or barium titanate.

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