Three-dimensional stacked ceramic packaging structure

Abstract

The invention relates to the technical field of three-dimensional packaging of radio frequency modules, and particularly discloses a three-dimensional stacked ceramic packaging structure which comprises an upper metal enclosure frame, an upper carrier plate, a lower metal enclosure frame and a lower carrier plate which are sequentially arranged from top to bottom. A radio frequency chip I is arranged on the upper carrier plate and located in the upper metal enclosure frame; a radio frequency chip II is arranged on the lower carrier plate and is positioned in the lower metal enclosure frame; a plurality of groups of independent copper columns are arranged in the lower metal enclosure frame; the first radio frequency chip and the second radio frequency chip are installed in an inverted buckling mode. According to the invention, the application requirements of high integration level, low transmission loss, high channel consistency, high reliability of efficient heat dissipation, rapid production and the like can be met at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional packaging of radio frequency modules, and more specifically, to a three-dimensional stacked ceramic packaging structure. Background Art

[0002] In cutting-edge applications such as 5G / 6G communications, millimeter-wave radar, and satellite communications, RF components are required to achieve low insertion loss, high bandwidth, and low latency at high frequencies. Traditional two-dimensional packaging, due to inherent limitations in signal transmission efficiency, is no longer able to meet the stringent requirements of these applications. In consumer electronics and military equipment, the demand for system integration continues to rise. This creates an urgent need to integrate diverse components, such as RF front-end modules, baseband chips, and antennas, into ever-more compact spaces.

[0003] Due to the physical bottlenecks of traditional planar processes, three-dimensional integration technology has emerged and is becoming a key path for continuously advancing RF device performance. By adopting a vertically stacked architecture, this innovative development model, "Beyond Moore's Law," has been achieved. This 3D stacking architecture significantly shortens interconnect traces, effectively suppressing parasitic effects, significantly increasing signal transmission rates while also reducing overall system power consumption.

[0004] The existing three-dimensional stacked packages include: silicon-based three-dimensional stacked packages, ceramic double-sided groove three-dimensional packages, and ceramic multi-substrate three-dimensional packages; silicon-based three-dimensional stacked packages have high costs, long cycles, poor airtightness, small package size, low thermal expansion coefficient, and poor PCB board integration reliability, and are prone to thermal stress fatigue failure under temperature cycles; ceramic double-sided groove three-dimensional packages have low integration, and high-frequency multi-channel and multi-functional applications are difficult; ceramic multi-substrate three-dimensional packages have poor isolation, poor heat dissipation, complex assembly processes, and low batch production efficiency; in addition, all of the above packaging structure RF chips use a bare chip plus gold wire bonding structure, so they also require complicated micro-assembly processes, and the performance consistency of the assembled RF channels is poor and the assembly cycle is long.

[0005] Therefore, there is an urgent need to propose a three-dimensional stacked packaging structure suitable for RF modules that can simultaneously take into account application requirements such as high integration, low transmission loss, high channel consistency, high reliability with efficient heat dissipation, and rapid production. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a three-dimensional stacked ceramic packaging structure;

[0007] The solution adopted by the present invention to solve the technical problem is:

[0008] A three-dimensional stacked ceramic packaging structure includes an upper metal frame, an upper loading board, a lower metal frame, and a lower loading board arranged in sequence from top to bottom;

[0009] A radio frequency chip 1 is provided on the upper carrier board and within the upper metal frame;

[0010] A second radio frequency chip is provided on the download board and located in the lower metal frame;

[0011] Several groups of independent copper columns are arranged in the lower metal frame;

[0012] The RF chip 1 and the RF chip 2 are respectively installed in a flip-down manner.

[0013] In some possible implementations, a first underfill is filled between the first RF chip and the upper loading board; a second underfill is filled between the second RF chip and the lower loading board;

[0014] The RF chip is electrically interconnected with the upper board through an internal connection point, and the digital and analog signals are then led out to the lower surface of the upper board through the fan-out function of the upper board;

[0015] The RF chip 2 is electrically interconnected with the download board through the internal connection point 2, and then the digital and analog signals are respectively led out to the independent copper pillars and the external connection points set on the back of the download board through the fan-out function of the download board.

[0016] In some possible implementations, the thermal expansion coefficients of the RF chip 1 and the RF chip 2 are both a, the thermal expansion coefficients of the upper loading board and the lower loading board are both b, and the thermal expansion coefficients of the underfill 1 and the underfill 2 are both c; wherein a<c<15 and a<b.

[0017] In some possible implementations, the upper loading plate and the lower loading plate are both made of aluminum oxide or aluminum nitride ceramics.

[0018] In some possible implementations, the upload board and the download board are both multi-layer structures and are provided with RF strip lines therein, and the RF signals of the RF chip 1 or the RF chip 2 are fanned out through the RF strip lines.

[0019] In some possible implementations, the upper metal frame and the lower metal frame are both made of oxygen-free copper and / or molybdenum; the height of the upper metal frame is A, the height of the RF chip 1 is B, 0 < AB ≤ 50 μm, the height of the upper metal frame is C, the height of the RF chip 2 is D, 0 < CD ≤ 50 μm, and the upper and lower metal frames enhance structural strength while increasing heat dissipation capacity;

[0020] In some possible implementations, the lower metal frame has multiple shielding cavities, the RF chip 2 and the independent copper pillar are respectively located in each shielding cavity, and openings corresponding to and connected to the shielding cavities are also provided on the lower metal frame.

[0021] In some possible implementations, passive components are provided at the bottom of the upper carrier board and within the lower metal frame.

[0022] In some possible implementations, the first internal connection point and the second internal connection point are BGA balls or copper pillars, respectively.

[0023] In some possible implementations, a dielectric material is further disposed on the outside of the independent copper column.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention has low radio frequency transmission loss and can realize low-loss interconnection of radio frequency modules;

[0026] The present invention adopts a flip-flop RF chip solution, utilizing the internal connection points (internal connection point 1, internal connection point 2) of the RF chips (RF chip 1, RF chip 2) and the grounded metal layer on the carrier board (upper carrier board, lower carrier board) to achieve good electromagnetic shielding between highly integrated chip channels.

[0027] Compared with the original radio frequency module bare chip adhesive bonding solution, the present invention adopts a chip flip-flop solution, which is simple to process, has a short processing cycle, and low packaging cost. In combination with high thermal conductivity molybdenum and copper materials, efficient heat dissipation of the package can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 This is a schematic structural diagram of the upper metal frame, upper carrier board, and radio frequency chip 1 of the present invention;

[0030] Figure 3 This is a structural diagram of the lower metal frame, download board, RF chip 2, independent copper pillars, and openings of the present invention;

[0031] Among them: 1. Upper metal frame; 2. RF chip 1; 3. Underfill 1; 4. Internal connection point 1; 5. Upper loading board; 6. Lower metal frame; 7. Independent copper pillar; 8. Download board; 9. External connection point; 10. Passive components; 11. RF chip 2; 12. Internal connection point 2; 13. Underfill 2; 14. Opening. DETAILED DESCRIPTION

[0032] In this application, unless otherwise specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integration; they can refer to direct connections or indirect connections through an intermediary; they can refer to internal communication between two components or interactions between two components. The terms "first," "second," and similar terms mentioned in this application do not denote any order, quantity, or importance; they are simply used to distinguish between different components. Similarly, terms such as "one" or "a" do not indicate a quantitative limitation; rather, they indicate the presence of at least one. In the implementation of this application, "and / or" describes an association relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. In the description of the embodiments of this application, unless otherwise specified, "plurality" means two or more. For example, "plurality" refers to two or more positioning posts. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0033] The present invention is described in detail below.

[0034] like Figure 1-Figure 3 As shown, a three-dimensional stacked ceramic package structure includes an upper metal frame 1, an upper loading board 5, a lower metal frame 6, and a lower loading board 8 arranged in sequence from top to bottom. The upper metal frame 1 is formed by machining and welded to the front of the upper loading board 5 to provide a good heat dissipation path for the module;

[0035] The front of the upper board 5 is welded with a radio frequency chip 2, which is located in the shielding cavity formed by the upper metal frame. The radio frequency chip 2 is electrically interconnected with the upper board 5 through an internal connection point 4, and the digital and analog signals are then output to the back of the upper board 5 through the fan-out function of the upper board 5.

[0036] After the RF chip 1 and the upper carrier board 5 are interconnected, they are filled and reinforced by the bottom filler 3. The bottom surface of the upper carrier board 5 can be assembled with passive components 10 such as modulators, resistors, capacitors, and inductors.

[0037] The lower metal frame 6 is grown on the download board 8 by electroplating, or the lower metal frame 6 that has been formed is welded by silver-copper or gold-tin;

[0038] A second RF chip 11 is welded on the front of the download board 8 and is located in the shielding cavity of the lower metal frame 6;

[0039] The second RF chip 11 is electrically interconnected with the download board 8 via the second internal connection point 12, and the digital and analog signals are respectively led out to the independent copper pillars 7 and the external connection points 9 on the back of the download board 8 through the fan-out function of the download board 8; after the second RF chip 11 is interconnected with the download board 8, it is filled and reinforced by the second underfill 13;

[0040] The upper upload board 5 is used as a transition to reflow solder the assembled upper upload board 5 and the download board 8 together to realize the interconnection of digital and analog signals;

[0041] It should be noted that the front side is the top side and the back side is the bottom side.

[0042] As a preferred technical solution, the upper loading plate 5 and the lower loading plate 8 are made of alumina or aluminum nitride ceramics, which can be realized by using a DPC process or a HTCC process, which will not be described in detail here.

[0043] As a preferred technical solution, the upload board 5 and the download board 8 are both multi-layer structures and are provided with RF strip lines inside, and the RF signals of the RF chip 1 2 or the RF chip 2 11 are fanned out through the RF strip lines;

[0044] As a preferred technical solution, the upper metal enclosure 1 and the lower metal enclosure 6 are made of oxygen-free copper, molybdenum, or alloys or splices of these metals, and their thickness must ensure that the height difference with the corresponding RF chip (RF chip 1 2 or RF chip 2 11) after welding is within 50 μm, that is, the height of the upper metal enclosure is A, the height of the RF chip 1 is B, 0<AB≤50 μm, the height of the upper metal enclosure is C, the height of the RF chip 2 is D, 0<CD≤50 μm; thereby, the upper metal enclosure 1 and the lower metal enclosure 6 enhance structural strength while increasing heat dissipation capacity;

[0045] As a preferred technical solution, the internal connection points (internal connection point 14, internal connection point 2 12) under the RF chip (RF chip 12 or RF chip 2 11) can be implemented using BGA balls or copper pillars. When the RF chip 12 is soldered to the upper board 5, the internal connection point 14 and the grounding copper foil on the surface of the upper board 5 can form a complete shielding function to improve channel isolation.

[0046] As a preferred technical solution, the lower metal frame 6 can flexibly set the shape and number of sub-cavities of the shielding cavity according to actual use requirements, and in order to ensure that the excess flux is conveniently cleaned after the upper loading board 5 and the downloading board 8 are reflow soldered, an opening 14 is provided on the lower metal frame 6. The setting of the opening 14 makes the shielding cavity not a closed cavity. The size of the opening 14 needs to be selected according to the operating frequency, which can not only ensure the RF shielding effect but also quickly clean the solder resist.

[0047] As a preferred technical solution, the independent copper pillars 7 can be used alone to interconnect the upper upload board 5 and the lower download board 5, or can be used in combination with the lower metal frame 6 to form a quasi-coaxial structure for transmitting radio frequency signals;

[0048] Specifically, when the independent copper pillar 7 is used in RF coaxial configuration, the diameter can be changed in sections for RF impedance matching; dielectric materials with different dielectric constants can also be inserted into the independent copper pillar 7 of the coaxial-like structure to increase the RF matching method.

[0049] As a preferred technical solution, the RF chip (RF chip 1 2, RF chip 2 11) can be made of any one of GaAs, GaN, and Si. After being soldered to the upper loading board 5 or the lower loading board 8, it is necessary to use an underfill (underfill 1 3, underfill 2 13) with a compromise in thermal expansion coefficient and high temperature resistance for underfilling. The underfill cannot be connected to the metal frame (upper metal frame 1, lower metal frame 6);

[0050] The thermal expansion coefficient of the RF chip (RF chip 1 2, RF chip 2 11) is a, a = 3-5 ppm / K;

[0051] The thermal expansion coefficient of the upper loading board 5 and the lower loading board 5 is b, b = 6-7 ppm / K;

[0052] The thermal expansion coefficient of the bottom filler 1 3 and the bottom filler 2 13 is c, c=14.9;

[0053] Specifically, when the RF chip 2 is made of Si material and the upper carrier board 5 is made of AlN material, the underfill 3 is ST8202;

[0054] When the RF chip 2 is made of GaAs material and the upper carrier board 5 is made of Al2O3 material, the underfill 3 is ST8202.

[0055] As a preferred technical solution, the U-shaped basic structure composed of the download board 8, the lower metal frame 6, and the independent copper pillars 7 can be expanded to achieve stacking of 3-layer, 4-layer or even more layers of packaging.

[0056] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A three-dimensional stacked ceramic packaging structure, characterized in that: It includes an upper metal frame, an upper loading plate, a lower metal frame, and a downloading plate arranged in sequence from top to bottom; A radio frequency chip 1 is provided on the upper carrier board and within the upper metal frame; A second radio frequency chip is provided on the download board and located in the lower metal frame; Several groups of independent copper columns are arranged in the lower metal frame; The RF chip 1 and the RF chip 2 are respectively installed in a flip-down manner.

2. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: The space between the RF chip 1 and the upper loading board is filled with underfill glue 1; the space between the RF chip 2 and the lower loading board is filled with underfill glue 2; The RF chip is electrically interconnected with the upper board through an internal connection point, and the digital and analog signals are then led out to the lower surface of the upper board through the fan-out function of the upper board; The RF chip 2 is electrically interconnected with the download board through the internal connection point 2, and then the digital and analog signals are respectively led out to the independent copper pillars and the external connection points set on the back of the download board through the fan-out function of the download board.

3. The three-dimensional stacked ceramic packaging structure according to claim 2, characterized in that: The thermal expansion coefficients of the RF chip 1 and the RF chip 2 are both a, the thermal expansion coefficients of the upper loading board and the lower loading board are both b, and the thermal expansion coefficients of the underfill glue 1 and the underfill glue 2 are both c; wherein a<c<15 and a<b.

4. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: The upper loading plate and the downloading plate are both made of aluminum oxide or aluminum nitride ceramics.

5. The three-dimensional stacked ceramic packaging structure according to claim 4, characterized in that: The upload board and the download board are both multi-layer structures and are provided with radio frequency strip lines inside, and the radio frequency signals of the radio frequency chip 1 or the radio frequency chip 2 are fanned out through the radio frequency strip lines.

6. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: The upper metal frame and the lower metal frame are both made of oxygen-free copper and / or molybdenum; the height of the upper metal frame is A, the height of the RF chip one is B, 0<AB≤50um, the height of the upper metal frame is C, the height of the RF chip two is D, 0<CD≤50um.

7. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: The lower metal frame has multiple shielding cavities, and the RF chip 2 and the independent copper pillar are respectively located in each shielding cavity. Openings corresponding to and communicating with the shielding cavities are also provided on the lower metal frame.

8. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: Passive components are arranged at the bottom of the upper carrier board and within the lower metal frame.

9. The three-dimensional stacked ceramic packaging structure according to claim 2, characterized in that: The first internal connection point and the second internal connection point are respectively BGA balls or copper pillars.

10. The three-dimensional stacked ceramic packaging structure according to claim 1, characterized in that: A dielectric material is also provided on the outer side of the independent copper column.

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