Microwave and millimeter wave low-cost compact radio frequency digital integrated front-end module

Abstract

The invention discloses a microwave and millimeter wave low-cost compact radio frequency digital integrated front-end module, and relates to the technical field of microwave and millimeter wave devices. The front-end module comprises a substrate layer, a preceding-stage compound bare chip and a silicon-based chip group are arranged on the upper surface of the substrate layer, a first group of BGA solder balls located on the lower surface of the substrate layer are connected with a first metal cushion block on one side of the preceding-stage compound bare chip through a first quasi-coaxial structure penetrating through the substrate layer up and down, and a second group of BGA solder balls located on the lower surface of the substrate layer are connected with a second metal cushion block on one side of the preceding-stage compound bare chip through a second quasi-coaxial structure penetrating through the substrate layer up and down. The second metal cushion block is connected with a BGA solder ball on one side of the BGA packaging chip through a second similar coaxial structure vertically penetrating through the substrate layer, and the BGA packaging chip is connected with a third metal cushion block on one side of the silicon-based chip set through a third similar coaxial structure vertically penetrating through the substrate layer. And the fourth metal cushion block is connected with a second group of BGA solder balls positioned on the lower surface of the substrate layer through a fourth quasi-coaxial structure which vertically penetrates through the substrate layer. The front-end module can realize extremely low-loss transmission, and the interconnection flexibility is higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave and millimeter-wave devices, and particularly relates to a low-cost and compact radio frequency and digital integrated front-end module for microwave and millimeter-wave. Background Art

[0002] The ceramic DPC (Dielectric Polymer Composite) thin film process is an advanced technology that combines the advantages of ceramic materials and polymer materials and is used to prepare system modules that require low dielectric constants and good mechanical properties. The low dielectric constant, due to the low dielectric constant of the dielectric PI, can effectively enhance the uniform distribution of the electric field and reduce the phenomenon of excessive local electric field concentration, thereby improving the stability of the thin film under high voltage. The ceramic material itself has good thermal stability, while the polymer provides a certain thermal buffering effect in the composite material, enabling the DPC thin film to still maintain excellent electrical and mechanical properties at higher temperatures. Its advantages of high reliability and compact design are commonly used in the design of modules such as antennas, radio frequencies, and passive devices.

[0003] Various highly controllable metallization patterns can be formed on the surface of the DPC substrate through local sputtering, providing new ideas and solutions for microwave radio frequency design. The integration technology of millimeter-wave radio frequency front-ends is the key to modern wireless communication (such as 5G / 6G) and radar systems, but there are still some significant technical challenges and disadvantages.

[0004] 1) High-frequency loss problem: In the millimeter-wave band, the losses of materials such as wires, dielectrics, and interconnections increase significantly. The loss of transmission lines is large, especially during long-distance transmission. Parasitic effects and coupling effects are more obvious in high-frequency circuits, resulting in performance degradation. Impact: Reduces the efficiency of power amplifiers. Has a negative impact on the overall system performance (such as gain and sensitivity).

[0005] 2) Heat dissipation problem: The power density of millimeter-wave front-end integrated circuits is relatively high, and the thermal conductivity of the materials is limited, making heat dissipation design difficult. Impact: An increase in temperature will affect the performance stability of devices, especially power amplifiers (PAs) and low-noise amplifiers (LNAs). Insufficient thermal management may lead to device failure or shortened lifespan.

[0006] 3) Complex and expensive manufacturing process: The millimeter-wave band has extremely high requirements for the manufacturing process, requiring high-precision process technologies (such as CMOS, GaAs, GaN, SiGe, etc.). The sizes of antennas, transmission lines, and filters are smaller in the millimeter-wave band, and higher manufacturing precision is required. Process non-uniformity will lead to performance differences. Impact: The integrated manufacturing cost is relatively high, especially during large-scale production. Process errors may lead to performance deviations or even circuit failures.

[0007] 4) High layout and design difficulty: The design of the millimeter-wave RF front-end needs to meet the requirements of high-frequency signal transmission, thermal management, interconnection density, etc. simultaneously. High-frequency signals are vulnerable to interference, and special processing is required in the design to reduce parasitic effects and signal coupling. The device size and circuit spacing are extremely small, increasing the design complexity. Impact: The design cycle is relatively long, and the product iteration speed is limited. Signal integrity and electromagnetic compatibility problems are likely to be introduced in the design.

[0008] 5) Power consumption and efficiency issues: The amplifiers and mixers in the millimeter-wave band have low efficiency. The low efficiency of power amplifiers leads to high overall power consumption. There is a contradiction between the requirement for low-power design and the demand for high performance. Impact: It limits the battery life of battery-powered devices (such as mobile terminals). The high power consumption poses higher requirements for the heat dissipation design.

[0009] 6) Electromagnetic interference and shielding issues: The wavelength of millimeter-wave signals is very short, making it easy to generate electromagnetic interference (EMI), especially in a high-density integration environment. The electromagnetic coupling and intermodulation effects between devices are more significant. Impact: It reduces the signal integrity of the system. It increases the complexity and cost of the shielding design. Summary of the Invention

[0010] The technical problem to be solved by the present invention is how to provide a radio frequency and digital integrated front-end module that can achieve extremely low-loss transmission and has stronger interconnection flexibility.

[0011] To solve the above technical problem, the technical solution adopted by the present invention is: a low-cost compact radio frequency and digital integrated front-end module for microwave and millimeter-wave, including a substrate layer. On the upper surface of the substrate layer, a pre-stage compound bare chip and a silicon-based chip group are respectively arranged. An airtight isolation frame and a cover plate are provided outside the pre-stage compound bare chip and the silicon-based chip group. On the lower surface of the substrate layer between the pre-stage compound bare chip and the silicon-based chip group, a BGA package chip is formed. The first group of BGA solder balls on the lower surface of the substrate layer is connected to the first metal pad on one side of the pre-stage compound bare chip through a first type of coaxial structure that penetrates the substrate layer up and down. On the upper surface of the substrate layer on the other side of the pre-stage compound bare chip, a second metal pad is formed. The second metal pad is connected to the BGA solder ball on one side of the BGA package chip through a second type of coaxial structure that penetrates the substrate layer up and down. The BGA solder ball on the other side of the BGA package chip is connected to the third metal pad on one side of the silicon-based chip group through a third type of coaxial structure that penetrates the substrate layer up and down. On the upper surface of the substrate layer on the other side of the silicon-based chip group, a fourth metal pad is formed. The fourth metal pad is connected to the second group of BGA solder balls on the lower surface of the substrate layer through a fourth type of coaxial structure that penetrates the substrate layer up and down. The pre-stage compound bare chip is connected to the first metal pad and the second metal pad, and the silicon-based chip group is connected to the third metal pad and the fourth metal pad through gold wire bonding wires.

[0012] The beneficial effects of adopting the above technical solutions are as follows: The front-end module includes a pre-stage compound bare chip, a silicon-based chipset, and a BGA packaged chip, and adopts a back-to-back structure to achieve point-to-point low-loss interconnection of radio frequency signals and a compact module design; the good thermal conductivity of the DPC substrate can effectively lead out the heat of the chip, and the advanced thin-film process is used to realize the RDL of high-density silicon-based chips; the placement of the front and back sides of the chip can ensure the electromagnetic compatibility effect between the front amplifier bare chips of different channels at the same time, and the airtightness of the bare chip can be ensured through the sealing cover plate. The processing of the DPC substrate can realize local thick copper to realize the metal pads integrated with the substrate, making various interconnections more flexible and eliminating the need for additional assembly processes.

[0013] In this application, some connections between the chip and the substrate adopt BGA solder balls, and BGA transmission can achieve low-loss and low-cost interconnection between boards within a relatively wide frequency band of microwave and millimeter wave. The interconnection method of die bonding (connected to the metal pads through gold wire bonding wires) realizes millimeter wave transmission. By using the metal pads of the DPC substrate itself to compensate for the bonding height, and the signal path adopts the shortest transmission path of BGA - quasi-coaxial - metal pad - bonding wire, extremely low-loss transmission effects can be achieved. Description of the Drawings

[0014] Figure 1 is a schematic cross-sectional structure diagram of the front-end module according to an embodiment of the present invention;

[0015] Figure 2 is a schematic structure diagram of the connection between the front-end module according to an embodiment of the present invention and the motherboard;

[0016] Figure 3 is a simulation result diagram in an embodiment of the present invention;

[0017] Among them: 1. Pre-stage compound bare chip; 2. Silicon-based chipset; 2-1. Silicon-based chip module; 2-1-1. Carrier board; 2-1-2. Silicon-based chip; 3. Isolation frame; 4. Cover plate; 5. BGA packaged chip; 6. First group of BGA solder balls; 7. First type of coaxial structure; 8. First metal pad; 9. Second metal pad; 10. Second type of coaxial structure; 11. Third type of coaxial structure; 12. Third metal pad; 13. Fourth metal pad; 14. Fourth type of coaxial structure; 15. Second group of BGA solder balls; 16. Gold wire bonding wire; 17. First substrate metal layer; 18. First substrate film layer; 19. Second substrate metal layer; 20. Second substrate film layer; 21. Third substrate metal layer; 22. First substrate core layer; 23. Fourth substrate metal layer; 24. First metallized via; 25. Second metallized via; 26. Motherboard. Detailed Embodiments

[0018] Combined with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0019] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0020] As shown in Figure 1 the embodiments of the present invention disclose a low-cost compact radio frequency and digital integrated front-end module for microwave and millimeter wave, including a substrate layer, and the substrate layer includes a first substrate metal layer 17, a first substrate film layer 18, a second substrate metal layer 19, a second substrate film layer 20, a third substrate metal layer 21, a first substrate core layer 22, and a fourth substrate metal layer 23 arranged from bottom to top. Preferably, the first substrate core layer 22 is made of DPC ceramic medium. Using DPC ceramic medium can effectively improve the heat conduction efficiency of the front-end compound die 1, and enable the heat of the entire module to be effectively transferred to the substrate BGA solder balls.

[0021] As the core layer of the basic layer, it consists of Figure 1 It can be seen that the thickness of the first substrate core layer 22 is greater than the thicknesses of the first substrate metal layer 17, the first substrate film layer 18, the second substrate metal layer 19, the second substrate film layer 20, the third substrate metal layer 21, and the fourth substrate metal layer 23. The thicknesses of the first substrate metal layer 17 to the fourth substrate metal layer 23 are the same, and the thicknesses of the first substrate film layer 18 and the second substrate film layer 20 are the same.

[0022] As shown in Figure 1As shown, a pre-stage compound bare chip 1 and a silicon-based chipset 2 are respectively disposed on the upper surface of the fourth substrate metal layer 23. An airtight isolation frame 3 and a cover plate 4 are disposed outside the pre-stage compound bare chip 1 and the silicon-based chipset 2. The upper surface of the substrate layer is isolated into two regions by the isolation frame 3 and the cover plate 4. One region is used to seal the pre-stage compound bare chip 1 and the first metal spacer 8 and the second metal spacer 9 supporting it, and the other region is used to seal the silicon-based chipset 2 and the third metal spacer 12 and the fourth metal spacer 13 supporting it. The airtight isolation frame 3 and the cover plate 4 can ensure the electromagnetic isolation and airtightness of the chipset formed by the pre-stage compound bare chip 1 and the silicon-based chipset 2 above the substrate core layer, and improve the reliability of the overall design.

[0023] Further, as Figure 1 shown, a BGA packaged chip 5 is formed on the lower surface of the first substrate metal layer 17 between the pre-stage compound bare chip 1 and the silicon-based chipset 2. The first group of BGA solder balls 6 on the lower surface of the substrate layer are connected to the first metal spacer 8 on the upper surface of the fourth substrate metal layer 23 on one side of the pre-stage compound bare chip 1 through a first type of coaxial structure 7 that penetrates the substrate layer up and down. A second metal spacer 9 is formed on the upper surface of the fourth substrate metal layer 23 on the other side of the pre-stage compound bare chip 1. The second metal spacer 9 is connected to the BGA solder ball on one side of the BGA packaged chip 5 through a second type of coaxial structure 10 that penetrates the substrate layer up and down. The BGA packaged chip 5 on the back can achieve electromagnetic isolation through the surrounding structure formed by the peripheral BGA solder balls.

[0024] The BGA solder ball on the other side of the BGA packaged chip 5 is connected to the third metal spacer 12 on the upper surface of the fourth substrate metal layer 23 on one side of the silicon-based chipset 2 through a third type of coaxial structure 11 that penetrates the substrate layer up and down. A fourth metal spacer 13 is formed on the upper surface of the fourth substrate metal layer 23 on the other side of the silicon-based chipset 2. The fourth metal spacer 13 is connected to the second group of BGA solder balls 15 on the lower surface of the first substrate metal layer 17 through a fourth type of coaxial structure 14 that penetrates the substrate layer up and down. The pre-stage compound bare chip 1 is connected to the first metal spacer 8 and the second metal spacer 9, and the silicon-based chipset 2 is connected to the third metal spacer 12 and the fourth metal spacer 13 through gold wire bonding wires 16.

[0025] Further, as Figure 1As shown, the silicon-based chipset 2 includes two or more silicon-based chip modules 2-1 arranged in an upper and lower stacked manner, and the specific structures of the silicon-based chip modules 2-1 may be the same or different. In this application, two silicon-based chip modules 2-1 with the same structure are provided. Further, the silicon-based chip module 2-1 includes a carrier board 2-1-1 and a silicon-based chip 2-1-2 located on the carrier board 2-1-1. The two silicon-based chip modules 2-1 are connected by BGA solder balls between the carrier boards 2-1-1. As Figure 1 shown, since there is one pre-stage compound bare chip 1, and the heights of the upper surfaces of the pre-stage compound bare chips 1 are basically the same, the heights of the first metal pad 8 and the second metal pad 9 are basically the same as the height of the pre-stage compound bare chip 1; since the silicon-based chipset 2 adopts a stacked structure with multiple silicon-based chip modules 2-1, in order to connect the silicon-based chip module 2-1 located on the uppermost side, the height of the third metal pad 12 is basically the same as the height of the silicon-based chipset 2, and in order to connect the silicon-based chip module 2-1 located on the lowermost side, the height of the fourth metal pad 13 is basically the same as the height of the silicon-based chip module 2-1 located at the lowermost layer in the silicon-based chipset 2.

[0026] Further, as Figure 1 shown, the structures of the first coaxial structure 7 to the fourth coaxial structure 14 are the same, and all include a first metallized via 24. The upper end of the first metallized via 24 passes through the upper surface of the fourth substrate metal layer 23 and is connected to the metal pad, and the lower end of the first metallized via 24 passes through the lower surface of the first substrate metal layer 17 and is connected to the BGA solder ball. A plurality of second metallized vias 25 are arranged at intervals on the outer periphery of the first metallized via 24. The upper ends of the second metallized vias 25 extend to the lower surface of the fourth substrate metal layer 23, and the lower ends of the second metallized vias 25 extend to the upper surface of the first substrate metal layer 17. Further, in order to stably connect the metal pad and the BGA solder ball, an upper connection portion is formed at the upper end of the first metallized via 24. The diameter of the upper connection portion is larger than the diameter of the main body of the first metallized via, and it is adapted to the metal pad; a lower connection portion is formed at the lower end of the first metallized via 24. The diameter of the lower connection portion is larger than the diameter of the main body of the first metallized via, and it is adapted to the BGA solder ball.

[0027] Signal transmission process: Among them, the high-frequency signal circuit adopts a quasi-coaxial structure for vertical transmission within the substrate, and its transmission frequency can reach 40 GHz; the signal is input from the BGA balls for signal transmission in the first group of BGA balls 6 at the bottom end into the first type of coaxial structure 7 inside the substrate, and is transmitted to the front-end compound die 1 through the first type of coaxial structure 7 between layers. After being processed by the front-end compound die 1, the signal is vertically transmitted between layers again through the second type of coaxial structure 10 to the BGA packaged chip 5; the digital signal passes through the pins of the BGA packaged chip 5 and is bonded to the silicon-based chipset 2 through the third type of coaxial structure 11 inside the substrate and the third metal spacer 12. After being processed by the three-dimensionally stacked chipset of the silicon-based chipset 2, electrical connection is achieved through bonding to the fourth metal spacer 13, and finally is transmitted to the second group of BGA balls at the bottom layer of the substrate through the fourth type of coaxial structure 14.

[0028] Furthermore, as Figure 2 shown, the front-end module further includes a motherboard 26, and the motherboard 25 is connected to the BGA balls for signal transmission in the first group of BGA balls 6 through the microstrip line on its PCB. In this application, the front-end module enters the first group of BGA balls 6 of the substrate through the microstrip line on the PCB of the motherboard 26, and the first group of BGA balls 6 is used for feeding. Tap feeding is performed on the lower thin-film metal layer of the substrate, and is connected to the first metal spacer 8 by the first type of coaxial structure 7, and then electrical connection is achieved by connecting both ends of the gold wire bonding wire to the PAD on the front-end compound die 1 and the first metal spacer 8. A total of two layers of PI dielectric and one layer of DPC ceramic dielectric are used in the entire front-end package.

[0029] Appendix Figure 3 is a schematic diagram of the simulation result of the front-end module described in this application. It can be seen that the return loss in the 1 - 40 GHz band is within the available range, and the propagation path is short, so its loss is also very small. Therefore, a low-cost and compact design of the pre-stage compound die and the BGA phased array chip can be achieved without redundant wiring.

Claims

1. A microwave and millimeter wave low-cost compact radio frequency digital integrated front-end module, characterized in that: The invention comprises a substrate layer, wherein a precursor compound bare chip (1) and a silicon-based chip group (2) are respectively arranged on the upper surface of the substrate layer, and the outer covers of the precursor compound bare chip (1) and the silicon-based chip group (2) are provided with an airtight isolation frame (3) and a cover plate (4), and a BGA packaged chip (5) is formed on the lower surface of the substrate layer between the precursor compound bare chip (1) and the silicon-based chip group (2), and a first group of BGA solder balls (6) located on the lower surface of the substrate layer are connected to a first metal pad (8) on one side of the precursor compound bare chip (1) through a first type of coaxial structure (7) penetrating the substrate layer from top to bottom, and a second metal pad (9) is formed on the upper surface of the substrate layer on the other side of the precursor compound bare chip (1), and the second metal pad (9) is connected to a second type of coaxial structure (10) penetrating the substrate layer from top to bottom. The BGA solder balls on one side of the BGA packaged chip (5) are connected, and the BGA solder balls on the other side of the BGA packaged chip (5) are connected to the third metal pad (12) on one side of the silicon-based chip group (2) via a third type of coaxial structure (11) that penetrates the substrate layer from top to bottom. A fourth metal pad (13) is formed on the upper surface of the substrate layer on the other side of the silicon-based chip group (2), and the fourth metal pad (13) is connected to the second group of BGA solder balls (15) located on the lower surface of the substrate layer via a fourth type of coaxial structure (14) that penetrates the substrate layer from top to bottom. The previous compound bare chip (1) and the first metal pad (8) and the second metal pad (9) as well as the silicon-based chip group (2) and the third metal pad (12) and the fourth metal pad (13) are connected via gold wire bonding wires (16).

2. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 1, characterized in that: The substrate layers include, arranged from bottom to top, a first substrate metal layer (17), a first substrate film layer (18), a second substrate metal layer (19), a second substrate film layer (20), a third substrate metal layer (21), a first substrate core layer (22), and a fourth substrate metal layer (23).

3. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 2, characterized in that: The first substrate core layer (22) is made of DPC ceramic medium.

4. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 2, characterized in that: The thickness of the first substrate core layer (22) is greater than the thickness of the first substrate metal layer (17), the first substrate film layer (18), the second substrate metal layer (19), the second substrate film layer (20), the third substrate metal layer (21) and the fourth substrate metal layer (23).

5. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 2, characterized in that: The structures of the first type of coaxial structure (7) to the fourth type of coaxial structure (14) are the same, including a first metallized via (24), the upper end of the first metallized via (24) passes through the upper surface of the fourth substrate metal layer (23) to be connected to the metal pad, the lower end of the first metallized via (24) passes through the lower surface of the first substrate metal layer (17) to be connected to the BGA solder ball, and a plurality of second metallized vias (25) are arranged at intervals on the periphery of the first metallized via (24), the upper end of the second metallized via (25) extends to the lower surface of the fourth substrate metal layer (23), and the lower end of the second metallized via (25) extends to the upper surface of the first substrate metal layer (17).

6. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 5, characterized in that: An upper connecting portion is formed at the upper end of the first metallized via (24), the diameter of which is greater than the diameter of the first metallized via body and is compatible with the metal pad; a lower connecting portion is formed at the lower end of the first metallized via (24), the diameter of which is greater than the diameter of the first metallized via body and is compatible with the BGA solder ball.

7. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 1, characterized in that: The upper surface of the substrate layer is isolated into two areas by the isolation frame (3) and the cover plate (4), one of which is used to seal the previous compound bare chip (1) and the first metal pad (8) and the second metal pad (9) matched therewith, and the other is used to seal the silicon-based chip group (2) and the third metal pad (12) and the fourth metal pad (13) matched therewith.

8. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 1, characterized in that: The silicon-based chip group (2) comprises a plurality of silicon-based chip modules (2-1) stacked in an upper and lower layer, the silicon-based chip module (2-1) comprising a carrier board (2-1-1) and a silicon-based chip (2-1-2) located on the carrier board (2-1-1), and two silicon-based chip modules (2-1) are connected via BGA solder balls between the carrier boards (2-1-1).

9. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 1, characterized in that: The front-end module also includes a motherboard (26), and the motherboard (25) is connected to the BGA solder balls in the first group of BGA solder balls (6) for signal transmission via microstrip lines on the PCB.

10. The microwave-millimeter-wave low-cost compact radio frequency digital integrated front-end module according to claim 1, characterized in that: The heights of the first metal pad (8) and the second metal pad (9) are adapted to the height of the previous compound bare chip (1); the height of the third metal pad (12) is adapted to the height of the silicon-based chip group (2); and the height of the fourth metal pad (13) is adapted to the height of the silicon-based chip module (2-1) located at the bottom layer of the silicon-based chip group (2).

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