A radio frequency coaxial connector and chip interconnect structure and T / R module

Abstract

The application discloses a radio frequency coaxial connector and chip interconnection structure and T / R assembly, relates to the technical field of microwave transceiver assembly, and solves the problem of how to reduce the size of the T / R assembly; the application comprises an assembly shell, a radio frequency coaxial connector, an MMIC chip and a gold wire; three sections of air coaxial matching structures and a ground bonding surface are arranged on the assembly shell; the inner conductor bonding end of the radio frequency connector is thickened and horizontally cut to form a step plane for bonding; the inner conductor of the radio frequency connector and the ground bonding surface are connected with the MMIC chip through the gold wire in a three-wire transmission mode of GSG to realize radio frequency interconnection; the application omits the traditional transition microstrip board between the radio frequency coaxial connector and the MMIC chip, effectively reduces the length of the T / R assembly, improves the reliability of the bonding point, optimizes the radio frequency transmission performance of the interconnection structure, and is more suitable for the application scene of the wideband T / R assembly.

Description

Technical Field

[0001] This invention relates to the field of microwave transceiver module (T / R module) technology, and more specifically to an interconnection structure between an RF coaxial connector and a chip, and a T / R module. Background Technology

[0002] The Transmission / Redirect (T / R) module is a core component of active phased array radar systems. Internally, it comprises multiple bare chips for microwave, control, and power management, housed in a hermetically sealed environment via metal or ceramic encapsulation. As missile-borne and spaceborne radar systems place increasingly stringent demands on the profile height of active antennas, the length of the T / R module in the transmission direction needs to be minimized. To meet the requirements of integration and miniaturization, the RF interface of the T / R module often employs miniaturized blind-matching RF coaxial connectors, such as SMP, SSMP, and CSMP connectors. The core microwave function within the T / R module is typically handled by a monolithic microwave integrated circuit (MMIC). The MMIC chip and the RF coaxial connector are generally interconnected via a transition microstrip board. This requires first connecting the RF coaxial connector to the microstrip line, and then the microstrip line interconnects with the MMIC chip.

[0003] This interconnection structure has the following three drawbacks.

[0004] Firstly, in this type of interconnect structure, the inner conductor of the RF coaxial connector is bonded to the microstrip line with conductive adhesive or soldered. The drawback of this method is the presence of mechanical stress, which can easily lead to breakage of the connection surface during temperature shock or vibration tests of the T / R assembly, resulting in low reliability. However, using a flexible connection with gold wire bonding can significantly improve its environmental adaptability. For example, document CN110429395A discloses a connection structure and method between a coaxial connector and a substrate microstrip. This structure includes a coaxial connector and a substrate microstrip; wherein one end of the inner conductor of the coaxial connector is bonded to the substrate microstrip via gold wire. This structure improves the reliability and stability of the connection between the coaxial connector and the substrate microstrip.

[0005] Secondly, based on engineering design experience, the length of this transition microstrip board is generally over 4mm, limiting further reduction in the length of the T / R assembly. Eliminating this transition microstrip board and designing a structure where the RF coaxial connector and MMIC chip are directly interconnected with gold wires would significantly improve the miniaturization of the T / R assembly. However, impedance discontinuities exist between the RF coaxial connector and the gold wires, and between the gold wires and the MMIC chip, which degrades RF performance such as return loss and transmission loss, and this effect becomes particularly pronounced with increasing frequency.

[0006] Finally, in engineering implementation, the inner conductor diameter of the SMP RF coaxial connector is only 0.38mm, while the diameters of SSMP and CSMP are even smaller, at 0.3mm and 0.23mm respectively. When bonding gold wires onto the inner conductor of the RF coaxial connector, the inner conductor will vibrate or even resonate under the pressure of the bonding wedge, which seriously affects the quality and long-term reliability of the gold wire bonding. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to reduce the size of the T / R component.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A radio frequency coaxial connector and chip interconnection structure includes: a component housing (1), a radio frequency coaxial connector (2), an MMIC chip (3), and a gold wire (4); the component housing (1) has a first air coaxial (11), a second air coaxial (12), and a third air coaxial (13) at the connection point; grounding planes are processed on the component housing (1) on both sides of the third air coaxial (13), which are respectively a first ground bonding surface (14) and a second ground bonding surface (15); the first air coaxial (11) and the second air coaxial (12) are cylindrical cavities, and the third air coaxial (13) is a semi-cylindrical cavity with an open top; the first air coaxial (11), the second air coaxial (12), and the third air coaxial (13) All are concentric with the RF coaxial connector (2); the inner conductor (21) of the RF coaxial connector (2) is thickened in diameter at the end near the MMIC chip (3) and a stepped bonding surface (221) is locally horizontally cut; the stepped bonding surface (221) is interconnected with the RF signal pad (32) of the MMIC chip (3) through gold wire (4); the first ground bonding surface (14) and the second ground bonding surface (15) are interconnected with the first ground pad (31) and the second ground pad (33) of the MMIC chip (3) through gold wire (4); the first ground bonding surface (14), the second ground bonding surface (15) and the stepped bonding surface (221) constitute the three-wire RF transmission form of GSG.

[0010] The matching method between the RF coaxial connector and the chip interconnection structure is as follows: the radii of the first air coaxial (11), the second air coaxial (12), and the third air coaxial (13) are r1, r2, and r3 respectively, and the relationship between the three satisfies r1 > r2 and r2 > r3; the lengths of the first air coaxial (11), the second air coaxial (12), and the third air coaxial (13) are l1, l2, and l3 respectively, l1 + l2 is equal to the length of the thickened portion of the inner conductor (21) of the RF coaxial connector (2) without cutting the step, and l3 is greater than the length of the stepped bonding surface (221) of the RF coaxial connector (2), and a gap is formed between the stepped bonding surface (221) and the MMIC chip (3).

[0011] The outer conductor (22) of the radio frequency coaxial connector (2) is soldered to the connector of the component housing (1) through the first solder ring (51) and the second solder ring (52).

[0012] The MMIC chip (3) is soldered or bonded to the cavity of the component housing (1) by soldering or adhesive bonding.

[0013] The first ground bonding surface (14) and the second ground bonding surface (15) are both at the same height as the stepped bonding surface (221).

[0014] The first bonding surface (14) and the second bonding surface (15) are plated with gold.

[0015] The gap between the stepped bonding surface (221) and the MMIC chip (3) is between 0.05 mm and 0.2 mm.

[0016] The number of gold wires (4) on each of the pads is 2 or 3.

[0017] The component housing (1) is made of aluminum, Kovar, aluminum-silicon or titanium alloy.

[0018] A T / R component employs the aforementioned radio frequency coaxial connector and chip interconnection structure.

[0019] The beneficial effects of this invention are:

[0020] The compact RF coaxial connector and chip interconnection structure and matching method provided by this invention eliminates the microstrip transition plate, effectively shortening the length of the T / R assembly. It also provides a matching method for three-section air coaxial and GSG-type gold wire bonding interconnection. This matching structure is machined on a metal part, resulting in high machining precision, small matching parameter deviation, and ease of implementation. Furthermore, the thickening of the inner conductor portion of the RF coaxial connector ensures the quality of the gold wire solder joints, achieving high reliability and high-performance soft connection. This significantly reduces mechanical stress and minimizes connection breakage during temperature shock or vibration tests of the T / R assembly, resulting in high reliability. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of the radio frequency coaxial connector and chip interconnection structure according to an embodiment of the present invention;

[0022] Figure 2 This is a top view of the radio frequency coaxial connector and chip interconnection structure according to an embodiment of the present invention;

[0023] Figure 3 For the present invention Figure 1 A magnified view of part A and its parameter labels;

[0024] Figure 4 The figure shows the simulation optimization results of an embodiment of the present invention. Detailed Implementation

[0025] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0026] In this application, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0027] Example 1

[0028] This embodiment 1 discloses a compact radio frequency coaxial and chip interconnect structure, see reference. Figure 1 It includes component housing 1, RF coaxial connector 2, MMIC chip 3, and gold wire 4.

[0029] See Figure 1 and Figure 2The component housing 1 has a first air coaxial section 11, a second air coaxial section 12, and a third air coaxial section 13 at its connection point. Grounding planes are machined on both sides of the third air coaxial section 1, namely a first ground bonding surface 14 and a second ground bonding surface 15. Furthermore, the first air coaxial section 11 and the second air coaxial section 12 are cylindrical cavities, and the third air coaxial section 13 is a semi-cylindrical cavity open at the top. All three air coaxial sections 11, 12, and 13 are concentric with the RF coaxial connector 2.

[0030] Furthermore, the outer conductor 22 of the RF coaxial connector 2 is soldered to the connector seat of the component housing 1 through the first solder ring 51 and the second solder ring 52. This can achieve the airtightness of the component on the one hand, and ensure a good connection between the RF coaxial connector 2 and the reference ground of the component housing 1 on the other hand.

[0031] Furthermore, the MMIC chip 3 is bonded to the cavity of the component housing 1 by soldering or adhesive bonding.

[0032] Furthermore, the inner conductor 21 of the RF coaxial connector 2 has a thickened diameter at the end near the MMIC chip 3 and a stepped bonding surface 221 is locally horizontally cut.

[0033] Furthermore, both the first ground bonding surface 14 and the second ground bonding surface 15 are at the same height as the stepped bonding surface 221. To accommodate the needs of gold wire bonding, the first ground bonding surface 14 and the second ground bonding surface 15 need to be gold-plated.

[0034] See Figure 2 The stepped bonding surface 221 is interconnected with the radio frequency signal pad 32 of the MMIC chip 3 through gold wires 4. The first ground bonding surface 14 and the second ground bonding surface 15 are interconnected with the first ground pad 31 and the second ground pad 33 of the MMIC chip 3 through gold wires 4, respectively. The first ground bonding surface 14, the second ground bonding surface 15 and the stepped bonding surface 221 constitute a three-wire radio frequency transmission form of GSG (ground-signal-ground). The number of gold wires 4 on each pad can be 2 or 3.

[0035] In a preferred embodiment of the present invention, the component housing 1 is a metal or alloy material that is a good conductor and suitable for hermetically sealed packaging, such as aluminum, Kovar, aluminum-silicon, titanium alloy, etc.

[0036] The matching method between the radio frequency coaxial cable and the chip interconnect structure:

[0037] The change in the diameter of the inner conductor of the RF coaxial connector will affect the characteristic impedance of the coaxial cable. The gold wire interconnect has a large parasitic inductance in the high frequency band, which will affect the transmission performance. The impedance is changed sequentially by adjusting the radius of the first air coaxial cable 11, the second air coaxial cable 12, and the third air coaxial cable 13, so as to improve the transmission performance degradation caused by the impedance mismatch caused by the interconnection of the RF coaxial connector 2, the gold wire 4, and the MMIC chip 3.

[0038] See Figure 3 The radii of the first air coaxial cable 11, the second air coaxial cable 12, and the third air coaxial cable 13 are r1, r2, and r3 respectively, and the relationship between the three satisfies r1 > r2 and r2 > r3. The size of r1, r2, and r3 is determined by full-wave simulation optimization based on the type of RF coaxial connector 2 selected.

[0039] See Figure 3 The lengths of the first air coaxial cable 11, the second air coaxial cable 12, and the third air coaxial cable 13 are l1, l2, and l3, respectively. l1 + l2 is equal to the length of the thickened portion of the inner conductor 21 of the RF coaxial connector 2 without cutting the step. l3 is slightly larger than the length of the stepped bonding surface 221 of the RF coaxial connector 2 to ensure that the gap between the stepped bonding surface 221 and the MMIC chip 3 is between 0.05 mm and 0.2 mm.

[0040] Without loss of generality, this invention uses an SMP connector as a typical example to further illustrate the optimized selection of matching parameters.

[0041] See Figure 1 The standard inner conductor 21 of the radio frequency coaxial connector 2 has a diameter of 0.38 mm, the thickened inner conductor 21 has a diameter of 0.5 mm, and the length of the stepped bonding surface 221 is generally between 0.5 mm and 1 mm.

[0042] The interconnect structure of this invention was modeled in full-wave simulation software, and parameters r1, r2, r3, l1, and l2 were scanned to determine the optimal parameter combination for return loss. In the preferred embodiment of this invention, r1, r2, and r3 are 0.45mm, 0.25mm, and 0.225mm, respectively, and l1 and l2 are 0.35mm and 0.15mm, respectively. Under this parameter combination, the interconnect structure of this invention exhibits good RF performance in the frequency band below 40GHz, with return loss below -21dB. Figure 4 .

[0043] Example 2

[0044] This embodiment provides a T / R component that adopts the RF coaxial and chip interconnect structure of Embodiment 1.

[0045] This invention eliminates the need for a traditional transition microstrip board between the RF coaxial connector and the MMIC chip, effectively reducing the length of the T / R assembly. By locally thickening the bonding end of the inner conductor of the RF coaxial connector, it effectively reduces the vibration or resonance caused by the thin inner conductor during gold wire bonding, improving the stability of the bonding point. Utilizing the GSG pad design of the MMIC chip, a three-wire gold wire transmission method is adopted, employing a soft connection to greatly reduce mechanical stress. This also reduces the likelihood of connection breakage during temperature shock or vibration tests of the T / R assembly, significantly avoiding ground plane discontinuities and ensuring high reliability. By designing a three-section air coaxial matching structure on the assembly housing, excellent RF performance in the sub-40GHz frequency band is achieved, making it suitable for broadband T / R assembly applications.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0047] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A radio frequency coaxial connector and chip interconnection structure, characterized in that, include: The component housing (1), RF coaxial connector (2), MMIC chip (3), and gold wire (4) are provided at the connection points of the component housing (1). A first air coaxial connector (11), a second air coaxial connector (12), and a third air coaxial connector (13) are provided at the connection points of the component housing (1). Grounding planes are machined on the component housing (1) on both sides of the third air coaxial connector (13), which are respectively a first ground bonding surface (14) and a second ground bonding surface (15). The first air coaxial connector (11) and the second air coaxial connector (12) are cylindrical cavities, and the third air coaxial connector (13) is a semi-cylindrical cavity with an open top. The first air coaxial connector (11), the second air coaxial connector (12), and the third air coaxial connector (13) are all connected to the RF coaxial connector. The connector (2) is kept concentric; the inner conductor (21) of the RF coaxial connector (2) is thickened in diameter at the end near the MMIC chip (3) and a stepped bonding surface (221) is locally horizontally cut; the stepped bonding surface (221) is interconnected with the RF signal pad (32) of the MMIC chip (3) through gold wire (4); the first ground bonding surface (14) and the second ground bonding surface (15) are interconnected with the first ground pad (31) and the second ground pad (33) of the MMIC chip (3) through gold wire (4); the first ground bonding surface (14), the second ground bonding surface (15) and the stepped bonding surface (221) constitute the three-wire RF transmission form of GSG; The matching method between the radio frequency coaxial connector and the chip interconnection structure is as follows: the radii of the first air coaxial (11), the second air coaxial (12), and the third air coaxial (13) are r1, r2, and r3 respectively, and the relationship between the three satisfies r1 > r2 and r2 > r3; the lengths of the first air coaxial (11), the second air coaxial (12), and the third air coaxial (13) are l1, l2, and l3 respectively, l1 + l2 is equal to the length of the inner conductor (21) of the radio frequency coaxial connector (2) with thickened diameter and without cut steps, and l3 is greater than the length of the stepped bonding surface (221) of the radio frequency coaxial connector (2), and the stepped bonding surface (221) and the MMIC chip (3) form a gap.

2. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The outer conductor (22) of the radio frequency coaxial connector (2) is soldered to the connector of the component housing (1) through the first solder ring (51) and the second solder ring (52).

3. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The MMIC chip (3) is soldered or bonded to the cavity of the component housing (1) by soldering or adhesive bonding.

4. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The first ground bonding surface (14) and the second ground bonding surface (15) are both at the same height as the stepped bonding surface (221).

5. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The first bonding surface (14) and the second bonding surface (15) are plated with gold.

6. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The gap between the stepped bonding surface (221) and the MMIC chip (3) is between 0.05 mm and 0.2 mm.

7. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The number of gold wires (4) on each of the pads is 2 or 3.

8. The RF coaxial connector and chip interconnection structure according to claim 1, characterized in that, The component housing (1) is made of aluminum, Kovar, aluminum-silicon or titanium alloy.

9. A T / R component, characterized in that, The radio frequency coaxial connector and chip interconnection structure described in any one of claims 1-8 are adopted.

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