Power amplifier package structure

Abstract

The application provides a power amplifier packaging structure. The power amplifier packaging structure comprises a power amplifier chip, a substrate, a wall, a transmission ceramic, a transmission lead and a cover plate; the power amplifier chip is arranged on the upper surface of the substrate; the wall is arranged around the power amplifier chip and is connected with the upper surface of the substrate; a plurality of through holes are arranged on the side surface of the wall and at the connection position of the upper surface of the substrate; one end of the transmission ceramic is arranged on the inner side of the side surface of the wall through the through holes and is connected with the corresponding pin on the power amplifier chip respectively, and the other end is arranged on the outer side of the side surface of the wall and is connected with the transmission lead respectively; the cover plate is arranged on the upper surface of the wall; and the cover plate is made of ceramic. The application can effectively eliminate the low-temperature self-excitation oscillation phenomenon of the power amplifier.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more particularly to a power amplifier packaging structure. Background Technology

[0002] As a core component of the radio frequency front-end, the power amplifier's main function is to amplify and output low-power microwave signals. During the production, assembly, and testing of power amplifiers, low-temperature self-oscillation frequently occurs, causing the device to malfunction. The causes of low-temperature self-oscillation are complex and typically related to factors such as the stability of the power amplifier itself, impedance mismatch in the external circuitry, packaging structure, and ambient temperature.

[0003] Currently, there are two main methods for eliminating low-temperature self-oscillation: First, adjusting the cavity size of the power amplifier. By adjusting the cavity size, the resonant frequency of the cavity can be adjusted, moving it away from the power amplifier's operating frequency band, thereby suppressing low-temperature self-oscillation. However, the cavity size requires comprehensive consideration of factors such as component size, location, shape, and performance, and often cannot be arbitrarily adjusted to achieve the desired effect of suppressing low-temperature self-oscillation. Second, attaching absorbing material to the packaging cover. This can effectively suppress the cavity's resonance intensity, but this method cannot fundamentally suppress the spatial microwave signal reflection caused by cavity resonance. It only solves part of the problem caused by cavity resonance, and the absorbing material has disadvantages such as strong water absorption and difficulty in cleaning, making it unsuitable for use in high-requirement hermetic packaging structures.

[0004] In summary, none of the above methods can effectively eliminate the low-temperature self-oscillation phenomenon in power amplifiers. Summary of the Invention

[0005] This invention provides a power amplifier packaging structure to solve the problem that existing technologies cannot effectively eliminate the low-temperature self-oscillation phenomenon in power amplifiers.

[0006] In a first aspect, embodiments of the present invention provide a power amplifier packaging structure, including: a power amplifier chip, a substrate, a wall, a transmission ceramic, transmission leads, and a cover plate;

[0007] The power amplifier chip is disposed on the upper surface of the substrate;

[0008] The wall surrounds the power amplifier chip and is connected to the upper surface of the substrate; multiple through holes are provided on the side surface of the wall at the connection position with the upper surface of the substrate; one end of the transmission ceramic passes through the through holes and is disposed on the inner side of the side surface of the wall, and is respectively connected to the corresponding pins on the power amplifier chip; the other end is disposed on the outer side of the side surface of the wall and is respectively connected to the transmission leads.

[0009] The cover plate is disposed on the upper surface of the wall; the cover plate is made of ceramic material.

[0010] In one possible implementation, the cover plate is made of a ceramic material containing Al2O3.

[0011] In one possible implementation, the Al2O3 content in the cover plate is greater than or equal to 92%.

[0012] In one possible implementation, the cover plate includes a first cover plate and a second cover plate;

[0013] The first cover plate is disposed on the upper surface of the wall;

[0014] The second cover plate is disposed on the upper surface of the first cover plate, and all edges of the second cover plate are on the first cover plate.

[0015] In one possible implementation, the second cover plate is disposed at the center of the upper surface of the first cover plate.

[0016] In one possible implementation, the substrate is made of an alloy; the wall is made of Kovar alloy.

[0017] In one possible implementation, the power amplifier package structure further includes: at least one external capacitor;

[0018] The peripheral capacitor is disposed on the inner side of the side surface of the wall and is in contact with the upper surface of the substrate;

[0019] The external capacitor is connected to the power amplifier chip.

[0020] In one possible implementation, the peripheral capacitor is a combined capacitor comprising at least one capacitor element.

[0021] This invention provides a power amplifier packaging structure. By employing a ceramic cover plate, it reduces thermal stress mismatch between the cover plate, the wall, the transmission ceramic, and the substrate, thereby controlling the deformation direction and reducing the deformation amount of the packaging structure. This optimizes the cavity resonant field within the packaging structure, preventing low-temperature self-oscillation caused by the cavity resonant frequency overlapping with the operating frequency of the power amplifier chip. Furthermore, compared to a metal cover plate, a ceramic cover plate reduces the input and output capacitance of the power amplifier, preventing low-temperature self-oscillation caused by signals leaking from the power amplifier's output terminal coupling to its input terminal via the output and input capacitors. Moreover, reducing the input and output capacitance improves the impedance matching between the input and output terminals, preventing low-temperature self-oscillation caused by impedance mismatch at certain frequencies. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the power amplifier packaging structure provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the power amplifier packaging structure provided in an embodiment of the present invention;

[0025] Figure 3 This is an internal schematic diagram of a power amplifier package structure provided in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the thermal deformation of a power amplifier package structure provided in an embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the power amplifier packaging structure provided in another embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the cover plate provided in another embodiment of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0030] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0031] The ultimate application of power amplifiers is in packaged form, that is, the power amplifier chip is packaged in a compatible housing. This housing structure can exhibit resonance effects, and when the resonant frequency falls within the power amplifier's operating frequency band, low-temperature self-oscillation occurs. This low-temperature self-oscillation leads to strong coupling between the input and output signals, causing signal interference and severely affecting the transmission characteristics of microwave signals. To address this low-temperature self-oscillation phenomenon in power amplifiers, this invention provides a power amplifier packaging structure to effectively eliminate it. The implementation of this invention will be described in detail below with reference to the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of a power amplifier packaging structure provided in an embodiment of the present invention. (Refer to...) Figures 1 to 3 The power amplifier package structure includes: a power amplifier chip 11, a substrate 12, a wall 13, a transmission ceramic 14, a transmission lead 15, and a cover plate 16.

[0033] The power amplifier chip 11 is disposed on the upper surface of the substrate 12;

[0034] The wall 13 surrounds the power amplifier chip 11 and is connected to the upper surface of the substrate 12. Multiple through holes are provided on the side surface of the wall 13 and at the connection position with the upper surface of the substrate 12. One end of the transmission ceramic 14 passes through the through hole and is disposed on the inner side of the side surface of the wall 13, and is connected to the corresponding pin on the power amplifier chip 11. The other end is disposed on the outer side of the side surface of the wall 13 and is connected to the transmission lead 15 respectively.

[0035] The cover plate 16 is provided on the upper surface of the wall 13; the cover plate 16 is made of ceramic.

[0036] In this embodiment of the invention, the power amplifier chip 11 is a GaN power amplifier chip. Typically, to facilitate heat dissipation of the power amplifier chip 11, the substrate 12 is made of an alloy material with high thermal conductivity. The wall 13 is made of Kovar alloy. The cover plate 16 is made of Kovar nickel-plated material. Due to varying degrees of thermal stress mismatch between different materials, the power amplifier packaging structure will undergo thermal deformation when the application environment of the power amplifier changes from room temperature to low temperature. Figure 4 A schematic diagram of the thermal deformation of the power amplifier package structure is shown. See also... Figure 4 In low-temperature environments, the power amplifier packaging structure undergoes thermal deformation, and the size of the cavity formed by the substrate 12, the wall 13, and the cover plate 16 increases, which leads to changes in the resonant frequency and distributed parameters inside the cavity, resulting in low-temperature self-excited oscillation.

[0037] At low temperatures, power amplifiers experience increased gain due to device characteristics, leading to a corresponding increase in feedback and making them more susceptible to low-temperature self-oscillation. The low-temperature environment provides the conditions for low-temperature self-oscillation in power amplifiers. To effectively ensure the performance of power amplifiers, it is common practice to verify the presence of low-temperature self-oscillation under low-temperature conditions.

[0038] See Figure 3 The power amplifier package has a total of 6 ports. Ports 1 and 3 are gate power interfaces for connecting the gate power supply. Ports 4 and 6 are drain power interfaces for connecting the drain power supply. Port 2 is the signal input terminal. Port 5 is the signal output terminal. The signal input terminal has an input capacitor and an input impedance. The signal output terminal has an output capacitor and an output impedance.

[0039] In this embodiment of the invention, the cover plate 16 is made of ceramic. By using a ceramic cover plate, on the one hand, the thermal stress mismatch between the cover plate, the wall, the transmission ceramic, and the substrate can be reduced, thereby controlling the deformation direction of the packaging structure and reducing the deformation amount. This optimizes the cavity resonant field inside the packaging structure and avoids low-temperature self-oscillation caused by the overlap between the cavity resonant frequency and the operating frequency of the power amplifier chip. On the other hand, using a ceramic cover plate instead of a metal one can reduce the input and output capacitance of the packaging structure, preventing low-temperature self-oscillation caused by the signal leaked from the power amplifier output terminal coupling to its input terminal through the output and input capacitances. Furthermore, by reducing the input and output capacitance, the matching degree between the input and output impedances can be improved, preventing impedance mismatch at certain frequency points of the power amplifier chip from disrupting the original matching state and balance conditions, thus avoiding low-temperature self-oscillation.

[0040] Essentially, the enclosure can generate low-temperature self-oscillation within a certain frequency band, and using a ceramic cover can eliminate this low-temperature self-oscillation at its source.

[0041] In one possible implementation, the cover plate 16 is made of a ceramic material containing Al2O3.

[0042] In one possible implementation, the Al2O3 content in the cover plate 16 is greater than or equal to 92%.

[0043] The higher the Al2O3 content, the better the matching of thermal expansion coefficients among the cover plate, walls, transport ceramics, and substrate in the packaging structure. This effectively prevents the cover plate and walls from deforming outwards, reduces the deformation of the packaging structure, and thus optimizes the cavity resonance field of the packaging structure, thereby avoiding low-temperature self-excited oscillations caused by cavity resonance. Simultaneously, a high Al2O3 ceramic cover plate can make the packaging structure closer to an open state, thereby effectively weakening the shielding effect of the cavity and further improving self-excitement phenomena. For example, the Al2O3 content in the cover plate 16 can be 99%.

[0044] In one possible implementation, see Figure 5 and Figure 6 The cover plate 16 includes a first cover plate 161 and a second cover plate 162.

[0045] The first cover plate 161 is disposed on the upper surface of the wall 13.

[0046] The second cover plate 162 is disposed on the upper surface of the first cover plate 161, and all edges of the second cover plate 162 are on the first cover plate 161.

[0047] As described above, in low-temperature environments, the cavity undergoes thermal deformation, which causes a change in the resonant frequency inside the cavity, leading to self-excitation. However, this embodiment of the invention, by superimposing a second cover plate on the upper surface of the first cover plate, can effectively suppress the thermal deformation of the cavity, thereby further improving the self-excitation phenomenon.

[0048] In one possible implementation, the second cover plate 162 is disposed at the center of the upper surface of the first cover plate 161.

[0049] According to the above Figure 4 The thermal deformation is greatest at the center of the cover plate. Therefore, the second cover plate 162 can be set at the center of the upper surface of the first cover plate 161 to effectively reduce the thermal deformation.

[0050] In one possible implementation, the substrate is made of an alloy; the wall is made of Kovar alloy.

[0051] By using an alloy as the substrate material and Kovar alloy as the wall material, the heat dissipation of the power amplifier chip can be effectively improved, thereby extending the service life of the power amplifier chip.

[0052] In one possible implementation, see Figure 3 The power amplifier package structure also includes at least one external capacitor 17.

[0053] The peripheral capacitor 17 is disposed on the inner side of the side surface of the wall 13 and is in contact with the upper surface of the substrate 12.

[0054] External capacitor 17 is connected to power amplifier chip 11.

[0055] The peripheral capacitor 17 works in conjunction with the power amplifier chip 12 to amplify the signal. The peripheral capacitor 17 can be located inside the side surface of the wall 13, that is, inside the cavity formed by the substrate, the wall, and the cover plate. The connection between the peripheral capacitor 17 and the power amplifier chip 11 can be set by the user according to the circuit schematic. Alternatively, the user can connect the peripheral capacitor to the transmission ceramic or other locations based on the circuit schematic. This embodiment of the invention does not specifically limit this connection.

[0056] In one possible implementation, the peripheral capacitor 17 is a combined capacitor comprising at least one capacitor element.

[0057] Compared to discrete capacitors, this embodiment of the invention uses a combined capacitor that includes at least one capacitor, which can effectively reduce the circuit size inside the cavity, thereby reducing the size of the package structure. By reducing the size of the package structure, the self-oscillation phenomenon can also be improved to some extent.

[0058] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows:

[0059] This invention employs a ceramic cover plate. On one hand, this reduces thermal stress mismatch between the cover plate, the wall, the transmission ceramic, and the substrate, thereby controlling the deformation direction of the packaging structure and reducing the deformation amount. This optimizes the cavity resonant field within the packaging structure, preventing low-temperature self-oscillation caused by the cavity resonant frequency overlapping with the power amplifier chip's operating frequency. On the other hand, compared to a metal cover plate, a ceramic cover plate reduces the input and output capacitance of the power amplifier, preventing low-temperature self-oscillation caused by signals leaking from the power amplifier's output terminal coupling to its input terminal via the output and input capacitances. Furthermore, reducing the input and output capacitance improves the impedance matching between the input and output terminals, preventing low-temperature self-oscillation caused by impedance mismatch at certain frequencies.

[0060] In addition, by superimposing the second cover plate on the upper surface of the first cover plate in the embodiments of the present invention, the thermal deformation of the cavity can be effectively reduced, thereby further improving the low-temperature self-excited oscillation phenomenon.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power amplifier package structure, characterized by, The power amplifier package structure comprises: a power amplifier chip, a substrate, a wall, a transmission ceramic, a transmission lead and a cover plate; the power amplifier chip is arranged on the upper surface of the substrate; the wall is arranged around the power amplifier chip and is connected with the upper surface of the substrate; a plurality of through holes are arranged on the side surface of the wall and at the connection position of the upper surface of the substrate; one end of the transmission ceramic is arranged on the inner side of the side surface of the wall through the through hole and is connected with the corresponding pin on the power amplifier chip respectively, and the other end is arranged on the outer side of the side surface of the wall and is connected with the transmission lead respectively; the cover plate is arranged on the upper surface of the wall; the material of the cover plate is ceramic material containing Al2O3; the cover plate comprises a first cover plate and a second cover plate; the first cover plate is arranged on the upper surface of the wall; the second cover plate is arranged on the upper surface of the first cover plate, and all the edges of the second cover plate are on the first cover plate.

2. The power amplifier package structure of claim 1, wherein, The content of Al2O3 in the cover plate is greater than or equal to 92%.

3. The power amplifier package structure of claim 1, wherein, The second cover plate is arranged at the center position of the upper surface of the first cover plate.

4. The power amplifier package structure of claim 1, wherein, The material of the substrate is alloy; the material of the wall is Kovar alloy.

5. The power amplifier package structure of claim 1, wherein, The power amplifier package structure further comprises at least one peripheral capacitor; the peripheral capacitor is arranged on the inner side of the side surface of the wall and is in contact with the upper surface of the substrate; the peripheral capacitor is connected with the power amplifier chip.

6. The power amplifier package structure of claim 5, wherein, The peripheral capacitor is a combined capacitor comprising at least one capacitor device.

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