MMIC surface-mounted packaging structure for micro coaxial switching and preparation method thereof

Abstract

The invention discloses a micro coaxial switching MMIC surface-mount packaging structure and a preparation method, a packaging tool comprises a packaging chamber enclosed by an upper cover plate and a lower cover plate, and the side wall of the packaging chamber is provided with a radio frequency switching port; an MMIC chip and a micro coaxial switching assembly are arranged in the packaging cavity, one end of the micro coaxial switching assembly is connected with a radio frequency interface of the MMIC chip, and the other end of the micro coaxial switching assembly extends to a radio frequency switching port. The packaging difficulty of a millimeter wave frequency band level MMIC chip is greatly simplified, meanwhile, the micro coaxial energy form can be easily changed into a standard surface-mounted interface through impedance conversion and vertical switching without causing signal loss, and lower insertion loss is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of MMIC surface mount packaging structures, and in particular to a micro-coaxial switching MMIC surface mount packaging structure and a preparation method thereof. Background Art

[0002] MMIC, or Monolithic Microwave Integrated Circuit, is a functional circuit chip used in microwave or even millimeter wave frequency bands that is made of passive and active devices manufactured using semiconductor substrates and process methods and connected together. It has the advantages of good circuit performance, high reliability, small size, and light weight, and has been widely used in modern communications, radar, electronic countermeasures and other fields.

[0003] Millimeter wave frequency is 30GHz ~ 300GHz, wavelength range is 1mm ~ 10mm, with short wavelength, wide bandwidth, large information capacity and other characteristics, widely used in communication, radar, guidance, electronic countermeasures and other fields. The input and output structure of millimeter wave monolithic circuit is generally GSG, that is, ground-signal-ground pin structure, which is essentially equivalent to a very short coplanar waveguide. MMIC packaging technology is the key technology to achieve the connection between on-chip circuit and other modules.

[0004] The existing packaging solutions mainly use gold wire bonding or flip chip welding to connect MMIC with microstrip lines, coplanar waveguides, etc., and then use microstrip probes to connect the monolithic circuit to the waveguide cavity to achieve signal conversion from monolithic circuit to transition structure to waveguide. Since the MMIC flip chip welding method requires the production of separate bumps in the chip welding area, and the chip is generally small, it is impossible to visually inspect it after flip chip welding, and the chip is installed face down, which makes the process operation difficult, and the grounding is also prone to welding short circuits and other problems. Therefore, gold wire bonding is generally used for packaging transition.

[0005] Gold wire bonding packaging generally requires specially designed microstrip lines or coplanar waveguide transitions. If the transitional microstrip lines or coplanar waveguides are too long, it is easy to cause additional losses or poor matching, especially in the millimeter wave band, where the frequency is higher and is easily affected by parasitic capacitance and parasitic inductance. Although gold wire leads have important applications in the packaging of millimeter wave MMIC chips, in actual application scenarios, if the chip is directly mounted on the circuit board and then gold wire bonded, or the existing form of gold wire bonding is used to transfer the transition lead-out technical solution, it is impossible to effectively provide an efficient and low-loss interconnection solution for millimeter wave MMIC. Summary of the invention

[0006] The present invention aims to solve at least one of the problems in the related art to a certain extent. To this end, one of the purposes of the present invention is to provide a micro-coaxial transfer MMIC surface mount packaging structure, which simplifies the packaging difficulty of the millimeter wave band level MMIC chip and reduces the loss of the quotation mark.

[0007] In order to achieve the above purpose, this application adopts the following technical solutions: A micro-coaxial transfer MMIC surface mount packaging structure, comprising: A packaging chamber surrounded by an upper cover plate and a lower cover plate, wherein a radio frequency switching port is provided on a side wall of the packaging chamber; An MMIC chip and a micro-coaxial adapter component are arranged inside the packaging chamber. One end of the micro-coaxial adapter component is connected to the radio frequency interface of the MMIC chip, and the other end extends to the radio frequency adapter port.

[0008] Furthermore, the RF adapter port is located on a side of the lower cover plate away from the upper cover plate, and the micro-coaxial adapter assembly is a vertical structure, which vertically transfers the MMIC chip located inside the packaging cavity to the RF adapter port.

[0009] Furthermore, the micro-coaxial adapter assembly includes an intermediate transmission conductor and a shielding cavity located outside the intermediate transmission conductor.

[0010] Furthermore, the RF switching port is located on a side of the lower cover away from the upper cover, and the intermediate transmission conductor includes a first lead-out portion and a second lead-out portion that are perpendicular to each other, the first lead-out portion is parallel to the plane where the lower cover is located, and one end of the first lead-out portion is connected to the RF interface of the MMIC chip, and the other end of the first lead-out portion is connected to the second lead-out portion; the second lead-out portion is perpendicular to the plane where the lower cover is located, and the other end of the second lead-out portion is flush with the RF switching port at the bottom of the lower cover.

[0011] Furthermore, the radio frequency interface and the intermediate transmission conductor are interconnected via a gold wire lead.

[0012] Furthermore, the micro-coaxial adapter component is a micro-coaxial adapter component in an impedance conversion form.

[0013] Furthermore, the number of the micro-coaxial adapter components corresponds one-to-one to the number of radio frequency interfaces in the MMIC chip.

[0014] Furthermore, a DC transfer port is provided on the side wall of the packaging chamber, a DC interface is provided in the MMIC chip, and the DC interface and the DC transfer port are directly interconnected through gold wire leads.

[0015] Furthermore, the DC switching port and the RF switching port are located on a side of the lower cover plate away from the upper cover plate.

[0016] The second object of the present application is to provide a method for preparing a micro-coaxial transfer MMIC surface mount packaging structure, comprising: A groove for placing the MMIC chip is machined on the top of the lower cover plate, and a radio frequency transfer port is machined on the bottom of the lower cover plate; A micro-coaxial adapter component is prepared on the top of the upper cover plate by using a micro-machining process; one end of the micro-coaxial adapter component is connected to the radio frequency interface of the MMIC chip, and the other end extends to the radio frequency adapter port and is flush with the radio frequency adapter port at the bottom of the lower cover plate; The upper cover plate covers the top of the lower cover plate, and the assembly forms a MMIC surface mount packaging structure of a micro-coaxial transfer.

[0017] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: The packaging chamber surrounded by the upper cover plate and the lower cover plate of the present application has a side wall provided with a radio frequency transfer port; an MMIC chip and a micro-coaxial transfer component are arranged inside the packaging chamber, one end of the micro-coaxial transfer component is connected to the radio frequency interface of the MMIC chip, and the other end extends to the radio frequency transfer port. Since the radio frequency interface of the MMIC chip is led out to the radio frequency transfer port by the micro-coaxial transfer component, the micro-coaxial transfer component can be structurally designed and changed according to the specific position of the radio frequency transfer port, avoiding the traditional form of gold wire lead to waveguide interface, and not requiring the MMIC chip to adopt the bump process to form the flip-chip, buried and other forms, thus greatly simplifying the packaging difficulty of the millimeter wave band level MMIC chip, and at the same time, the micro-coaxial energy form can be easily transformed into a standard surface mount interface through impedance transformation and vertical transfer without causing signal loss, so this packaging structure is an efficient millimeter wave MMIC packaging form.

[0018] Since the micro-coaxial adapter is used as the transition lead of the MMIC chip, a shorter gold wire lead structure can be used at the MMIC chip end to form a coplanar waveguide with the ground-signal-ground pins on the chip and the micro-coaxial adapter. In this form, the length of the gold wire lead is very short, and the micro-coaxial adapter can transmit signals in TEM mode at a frequency of 0~450GHz. The insertion loss of the micro-coaxial adapter can be maintained at 0.2dB / cm, and the output port can be easily converted into a standard SMT RF interface through impedance transformation. Therefore, using micro-coaxial form as the signal transmission form of the package can have lower insertion loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0021] In the attached figure: Figure 1 This is a schematic diagram of the overall effect of the interior of the packaging chamber of this application; Figure 2 This is a schematic diagram of the structure of the top of the lower cover plate of this application; Figure 3 This is a schematic diagram of the structure of the upper cover plate of this application; Figure 4 is a schematic diagram of a DC transfer port in the lower cover; Figure 5 It is a schematic diagram of the micro-coaxial adapter assembly and the internal adapter structure; Figure 6 A schematic diagram of the micro-coaxial adapter assembly and the internal adapter structure for the impedance conversion port size; Figure 7 It is a schematic diagram of the assembly of the lower cover plate and the micro-coaxial adapter assembly; Figure 8 This is a schematic diagram of the internal effect of the coaxial line after the lower cover plate and the micro-coaxial adapter assembly are assembled; Fig. 9 A schematic diagram of a packaging structure formed by assembling an upper cover plate and a lower cover plate; Fig.10 This is a schematic diagram of the packaging structure after the upper cover and the lower cover are finally assembled.

[0022] In the figure: 11, lower cover; 12, upper cover; 13, MMIC chip; 14, micro-coaxial adapter assembly; 141, intermediate transmission conductor; 142, shielding cavity; 15, DC transfer port; 151, DC IO signal pin; 152, insulation seal; 16, RF transfer port; 161, surface mount port; 162, surface mount port for impedance transformation; 163, regular gap; 21, DC transfer reserved slot; 22, chip reserved slot; 23, micro-coaxial reserved slot. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings, are constructed and operated in a specific direction, and are only for the convenience of describing the present technical solution, rather than indicating that the mechanism or element referred to must have a specific direction, and therefore cannot be understood as a limitation to the present invention.

[0024] It should also be noted that, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intermediate elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0025] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, mechanisms, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0026] In view of the defects of gold wire bonding or flip chip welding in the prior art, this application adopts SMT (Surface Mount Technology) packaging technology and micro-coaxial adapter assembly packaging technology. SMT is a pinless surface assembly structure solution that can simultaneously achieve batch and efficient circuit interconnection through reflow soldering and other solutions. Therefore, the surface mount packaging structure suitable for millimeter wave band MMIC is the key to solving the above contradiction. Micro-coaxial adapter assembly has the advantages of small size, low loss and high isolation.

[0027] Example 1

[0028] See also Figure 1-Figure 10 The present application provides a micro-coaxial adapter MMIC surface-mount packaging structure, which is characterized by comprising: a packaging chamber surrounded by an upper cover plate 12 and a lower cover plate 11, and a RF adapter port 16 is opened on the side wall of the packaging chamber; an MMIC chip 13 and a micro-coaxial adapter component 14 are arranged inside the packaging chamber, and one end of the micro-coaxial adapter component 14 is connected to the RF interface of the MMIC chip 13, and the other end extends to the RF adapter port 16.

[0029] Since the present application adopts a micro-coaxial adapter component 14 to lead the RF interface of the MMIC chip 13 to the RF adapter port 16, the micro-coaxial adapter component 14 can be structurally designed and changed according to the specific position of the RF adapter port 16, avoiding the traditional form of gold wire lead to waveguide interface, and does not require the MMIC chip 13 to adopt a bump process to form a flip-chip, buried, etc. form, thereby greatly simplifying the packaging difficulty of the millimeter wave frequency band level MMIC chip 13. At the same time, the micro-coaxial form can be easily transformed into a standard surface-mount interface through impedance transformation and vertical transfer without causing signal loss. Therefore, this packaging structure is an efficient millimeter wave MMIC packaging form.

[0030] Since the present application adopts the micro-coaxial adapter component 14 as the transition lead of the MMIC chip 13, a shorter gold wire lead structure can be used at the end of the MMIC chip 13 to form a coplanar waveguide with the ground-signal-ground pins on the chip and the micro-coaxial adapter component 14. In this form, the length of the gold wire lead is very short, and the micro-coaxial adapter component 14 can transmit signals in TEM mode at a frequency of 0~450GHz, and the insertion loss of the micro-coaxial adapter component 14 itself can be maintained at 0.2dB / cm, and the output port can be easily converted into a standard SMT RF interface through impedance transformation. Therefore, the use of micro-coaxial form as the signal transmission form of the package can have lower insertion loss.

[0031] Example 2

[0032] See also Figure 1-Figure 10 The present application provides a micro-coaxial adapter MMIC surface-mount packaging structure, which is characterized by comprising: a packaging chamber surrounded by an upper cover plate 12 and a lower cover plate 11, and a RF adapter port 16 is opened on the side wall of the packaging chamber; an MMIC chip 13 and a micro-coaxial adapter component 14 are arranged inside the packaging chamber, and one end of the micro-coaxial adapter component 14 is connected to the RF interface of the MMIC chip 13, and the other end extends to the RF adapter port 16.

[0033] In the present application, the packaging chamber can be formed by assembling an upper cover plate 12 and a lower cover plate 11, or by assembling multiple cover plates. It is only necessary to form a packaging chamber between multiple cover plates to accommodate the MMIC chip 13, the micro-coaxial adapter assembly 14, etc. Similarly, the RF adapter port 16 is located on the side wall of the packaging chamber, that is, the RF adapter port 16 is an interface connecting the entire packaging chamber and the outside, and it needs to be set at the outer side wall of the packaging chamber to facilitate plugging with other external components.

[0034] This embodiment is described by taking the assembly of the upper cover plate 12 and the lower cover plate 11 to form a packaging chamber as an example: The RF adapter port 16 is located on a side of the lower cover plate 11 away from the upper cover plate 12 . The micro-coaxial adapter assembly 14 is a vertical structure, and vertically transfers the MMIC chip 13 located inside the packaging cavity to the RF adapter port 16 .

[0035] The present application defines the side of the lower cover 11 close to the upper cover 12 as the top of the lower cover 11, and defines the side of the lower cover 11 away from the upper cover 12 as the bottom of the lower cover 11, that is, the packaging chamber is formed by assembling the top of the lower cover 11 and the upper cover 12, and the MMIC chip 13 is located at the top of the lower cover 11. At the same time, the RF adapter port 16 is located at the bottom of the lower cover 11, and the function of the micro-coaxial adapter assembly 14 is to lead the RF interface in the MMIC chip 13 to the position of the RF adapter port 16.

[0036] The micro-coaxial adapter assembly 14 includes an intermediate transmission conductor 141 and a shielding cavity 142 located outside the intermediate transmission conductor 141. The RF adapter port 16 is located on the side of the lower cover 11 away from the upper cover 12. The intermediate transmission conductor 141 includes a first lead-out portion and a second lead-out portion perpendicular to each other. The first lead-out portion is parallel to the plane where the lower cover 11 is located, and one end of the first lead-out portion is connected to the RF interface of the MMIC chip 13, and the other end of the first lead-out portion is connected to the second lead-out portion; the second lead-out portion is perpendicular to the plane where the lower cover 11 is located, and the other end of the second lead-out portion is flush with the RF adapter port 16 at the bottom of the lower cover 11.

[0037] In this embodiment, the RF interface in the MMIC chip 13 is located in a horizontal plane parallel to the plane where the lower cover 11 is located, and the RF adapter port 16 is located at the bottom end of the lower cover 11 and needs to be vertically plugged with external components. Therefore, it is necessary to set a micro-coaxial adapter assembly 14 with a bending structure to realize RF signal connection in different planes.

[0038] The micro-coaxial adapter assembly 14 includes an intermediate transmission conductor 141 and an outer shielding cavity 142, wherein the intermediate transmission conductor 141 and the outer shielding cavity 142 are made of metal, the intermediate transmission conductor 141 is used to transmit radio frequency signals, and the shielding cavity 142 is used to shield radio frequency signals to ensure orderly transmission in the inner space of the shielding cavity 142. It should be noted that in the process of preparing and forming the micro-coaxial adapter assembly 14, a dielectric layer connecting the intermediate transmission conductor 141 and the shielding cavity 142 is required to realize the molding and etching of the intermediate transmission conductor 141. The dielectric layer is made of insulating material and will not play a role in signal transmission. It only exists and is used as a supporting layer.

[0039] The micro-coaxial adapter assembly 14 is prepared through semiconductor processes such as coating, photolithography, electroplating, polishing, wet etching and other micro-processing methods. For details, please refer to the existing technology; in the process of preparing the micro-coaxial adapter assembly 14, it is necessary to first use a sacrificial layer and a dielectric layer to form an intermediate transmission conductor 141 located inside the shielding cavity 142, and then remove the sacrificial layer. Since the micro-coaxial adapter assembly 14 has a certain length, if the sacrificial layer can only be removed through the two ends of the shielding cavity 142, the formation process of the micro-coaxial adapter assembly 14 will be increased. For the convenience of processing, when the frequency range of the radio frequency signal is determined, a regular gap 163 can be formed in the shielding cavity 142 to ensure that the radio frequency signal will not be reflected or act on the gap position when it is transmitted in the shielding cavity 142. This can ensure the orderly transmission of the radio frequency signal and ensure that the sacrificial layer can be removed from the regular gap 163, simplifying the difficulty of preparing the micro-coaxial adapter assembly 14. Figure 5 and 6 Regular gaps 163 are formed in the shielding layer, and the positions of the regular gaps 163 are determined according to the frequency range of the radio frequency signal to avoid interference or leakage to the transmission of the radio frequency signal.

[0040] The RF interface and the intermediate transmission conductor 141 described in the present application are interconnected by a gold wire lead. One end of the first lead-out portion in the intermediate transmission conductor 141 is located on the side of the MMIC chip 13, that is, it is arranged adjacent to the RF interface in the MMIC chip 13, and the distance between the two is small and located in the same plane. At this time, the RF interface in the MMIC chip 13 and the end of the first lead-out portion are connected by a gold wire lead, which can ensure that the ground-signal-ground RF signal in the MMIC chip 13 is led out to the micro-coaxial adapter component 14 by a shorter distance of gold wire lead; avoid the problem of additional loss or poor matching caused by the excessive length of the gold wire lead in the prior art, and for the higher frequency millimeter wave band, it can also try to avoid the influence of parasitic capacitance and parasitic inductance caused by the gold wire lead. The micro-coaxial adapter component 14 in the present application can transmit signals in TEM mode at a frequency of 0~450GHz, and its own insertion loss can be maintained at 0.2dB / cm. With a shorter gold wire lead, the insertion loss of the overall packaging structure can be reduced.

[0041] The specific structure of the micro-coaxial adapter assembly 14 in the present application can be set according to the specific positions of the MMIC chip 13 and the RF adapter port 16. When the MMIC chip 13 and the RF adapter port 16 are located in the same plane, the intermediate transmission wire 141 in the micro-coaxial adapter assembly 14 is a straight structure; when the MMIC chip 13 and the RF adapter port 16 are located in different planes, the intermediate transmission wire 141 in the micro-coaxial adapter assembly 14 is a bent structure. Specifically in this embodiment, the intermediate transmission wire 141 in the micro-coaxial adapter assembly 14 can be an L-shaped structure, that is, a vertical bending structure is provided. The bottom of the RF adapter port 16 in the present application is flush with the lower surface of the lower cover plate 11, which is the plug-in entrance of the packaging structure and the external components.

[0042] The micro-coaxial adapter component 14 described in the present application is a micro-coaxial adapter component 14 in the form of impedance transformation, such as Figure 6 As shown, the micro-coaxial transfer assembly in the form of impedance transformation can adapt to external components with different impedances, so that power transmission is maximized when the packaging structure is plugged into the external components.

[0043] The number of micro-coaxial adapter components 14 in the present application corresponds to the number of RF interfaces in the MMIC chip 13. When the corresponding RF interface needs to be connected and output, it is only necessary to connect the corresponding RF interface to the corresponding micro-coaxial adapter component 14 and lead it out to the RF adapter port 16.

[0044] In the present application, in addition to the RF signal, the MMIC chip 13 also needs to lead out a DC signal. A DC transfer port 15 is provided on the side wall of the packaging chamber, and a DC interface is provided in the MMIC chip 13. The DC interface and the DC transfer port 15 are directly interconnected through gold wire leads. The DC transfer port 15 and the RF transfer port 16 are located on the side of the lower cover plate 11 away from the upper cover plate 12.

[0045] The present application arranges the DC transfer port 15 and the RF transfer port 16 on the same side, which can ensure that when the packaging structure is plugged into an external component, only the side with the transfer port needs to be exposed.

[0046] The present application uses a low-temperature sintered sealed glass insulator and a Kovar alloy pin to complete the sintering of the IO pin in the lower cover 11. During sintering, the end surface for surface mounting is kept at the same level as the shell surface, and the sintering temperature is 650°C to form a DC transfer port 15. The DC transfer port 15 is used to lead out the DC signal in the MMIC chip 13, and the RF transfer port 16 is used to lead out the RF signal in the MMIC chip 13. The DC signal and the RF signal can be led out to the bottom port position of the lower cover 11, which is convenient for plugging with external components.

[0047] Example 3

[0048] A method for preparing a micro-coaxial transfer MMIC surface mount packaging structure, wherein in this embodiment, the upper cover plate 12 and the lower cover plate 11 form a packaging chamber, such as Figure 1 As shown, the packaging chamber is provided with an MMIC chip 13, a micro-coaxial adapter component 14, a radio frequency adapter port 16 and a DC adapter port 15. Specifically, it includes: S1: a chip reserved groove 22 is processed on the top of the lower cover plate 11 , and a radio frequency switching port 16 is processed on the bottom of the lower cover plate 11 .

[0049] The upper cover plate 12 and the lower cover plate 11 serve as the main body for mounting and supporting the MMIC chip 13 and shielding the interior of the packaging chamber, so the upper cover plate 12 and the lower cover plate 11 are metal shells. The DC adapter port 15 serves as the DC signal pin in the packaging structure, the RF adapter port 16 serves as the RF signal pin in the packaging structure, and the micro-coaxial adapter component 14 serves as a transition structure for converting the gold wire bonding lead interface of the MMIC chip 13 to the RF adapter port 16 of the flip-chip surface mount.

[0050] Specifically include: S11: Prepare the lower cover plate 11 and the upper cover plate 12, such as Figure 2 and Figure 3As shown, the processing material is Kovar alloy, and the processing method is precision machining. A DC transfer reserved slot 21, a radio frequency transfer reserved slot, a chip reserved slot 22 and a micro coaxial reserved slot 23 are reserved in the lower cover plate 11. The DC transfer reserved slot 21 is located at the bottom of the lower cover plate 11 and is a through-hole structure with a diameter of generally 0.8 mm. The radio frequency transfer reserved slot can be further modified by laser processing.

[0051] S12: After the upper cover plate 12 and the lower cover plate 11 are processed, their surfaces are subjected to gold plating.

[0052] S2: Prepare a DC IO signal pin 151 at the DC transfer reserved slot 21 in the lower cover 11 by means of insulation sealing 152 .

[0053] S21: Figure 4 As shown, a Kovar alloy wire with a flat bottom, a diameter of 0.2 mm, and a length of 0.3 mm is selected as the IO pin, and the surface is chemically gold-plated.

[0054] S22: A low-temperature sintered sealed glass insulator is then used in conjunction with a Kovar alloy pin at the DC transfer reserved slot 21 of the lower cover plate 11 to complete the sintering of 12 DC IO signal pins 151. During sintering, the end face used for the surface mounting is kept at the same level as the shell surface, and the sintering temperature is 650°C.

[0055] S3: Prepare a micro-coaxial adapter component 14 on the top of the upper cover plate 12 by using a micro-machining process; one end of the micro-coaxial adapter component 14 is connected to the RF interface of the MMIC chip 13, and the other end extends to the RF adapter port 16 and is flush with the RF adapter port 16 at the bottom of the lower cover plate 11. Specifically including: S31: Figure 5 As shown, the micro-coaxial transfer structure is designed using HFSS according to the operating frequency, chip size, loss and other requirements of the selected MMIC chip 13. One end of the micro-coaxial transfer structure adopts a form similar to a coplanar waveguide, which is used to interconnect with the MMIC chip 13 through a gold wire lead, and the other port, i.e., the end close to the RF transfer port 16, adopts a micro-coaxial form and turns downward (in the surface mounting direction) into a vertical interconnection form to form a surface mounting GSG interface. At this time, the surface mounting port 161 is an opening located on the lower surface of the lower cover plate 11.

[0056] like Figure 7 As shown, the micro-coaxial adapter 14 can also be an impedance-transformed micro-coaxial adapter 14, that is, the impedance-transformed form is used for the transfer. In this case, the impedance-transformed surface-mount port 162 is an opening located on the lower surface of the lower cover 11.

[0057] S32: The micro-coaxial transfer structure is prepared by using semiconductor processes such as coating, photolithography, electroplating, polishing, wet etching and other micro-processing methods.

[0058] The micro-coaxial adapter assembly 14 is prepared through semiconductor processes such as coating, photolithography, electroplating, polishing, wet etching and other micro-processing methods. For details, please refer to the existing technology; in the process of preparing the micro-coaxial adapter assembly 14, it is necessary to first use a sacrificial layer and a dielectric layer to form an intermediate transmission conductor 141 located inside the shielding cavity 142, and then remove the sacrificial layer. Since the micro-coaxial adapter assembly 14 has a certain length, if the sacrificial layer can only be removed through the two ends of the shielding cavity 142, the formation process of the micro-coaxial adapter assembly 14 will be increased. For the convenience of processing, when the frequency range of the radio frequency signal is determined, a regular gap 163 can be formed in the shielding cavity 142 to ensure that the radio frequency signal will not be reflected or act on the gap position when it is transmitted in the shielding cavity 142. This can ensure the orderly transmission of the radio frequency signal and ensure that the sacrificial layer can be removed from the regular gap 163, simplifying the difficulty of preparing the micro-coaxial adapter assembly 14. Figure 5 and 6 Regular gaps 163 are formed in the shielding layer, and the positions of the regular gaps 163 are determined according to the frequency range of the radio frequency signal to avoid interference or leakage to the transmission of the radio frequency signal.

[0059] S4: The upper cover plate 12 covers the top of the lower cover plate 11 to form a micro-coaxial transfer MMIC surface mount packaging structure. Specifically, two or more micro-coaxial transfer components 14 can be assembled with the processed lower cover plate 11 by welding or bonding. For example, two micro-coaxial transfer components 14 are connected by soldering sheets in a similar manner. Figure 7 The assembly form is welded at the RF adapter port 16 of the lower cover plate 11, and the welding surface is the upper surface of the lower cover plate 11 and the lower surface of the micro-coaxial external adapter component. At the same time, the contact position of the welding piece should avoid the surface mount port 161. This assembly method can more conveniently realize the transition of the gold wire lead of the RF interface of the MMIC chip 13 to the micro-coaxial coplanar waveguide, and then transition to the surface mount GSG port through the micro-coaxial line adapter component.

[0060] After assembly, the lower surface (surface mounting direction) of the lower cover plate 11 should be kept flush with the GSG port of the micro-coaxial surface mounting form, so as to facilitate the surface mounting of the packaged MMIC to be soldered to a carrier such as a circuit board. The internal effect of the micro-coaxial adapter assembly 14 is as follows Figure 8 .

[0061] Finally, the upper cover plate 12 and the lower cover plate 11 after the chip assembly are welded together by laser welding. Fig. 9 and Fig.10 The surface mount package structure shown.

[0062] The packaging chamber surrounded by the upper cover plate and the lower cover plate of the present application has a side wall provided with a radio frequency transfer port; an MMIC chip and a micro-coaxial transfer component are arranged inside the packaging chamber, one end of the micro-coaxial transfer component is connected to the radio frequency interface of the MMIC chip, and the other end extends to the radio frequency transfer port. Since the radio frequency interface of the MMIC chip is led out to the radio frequency transfer port by the micro-coaxial transfer component, the micro-coaxial transfer component can be structurally designed and changed according to the specific position of the radio frequency transfer port, avoiding the traditional form of gold wire lead to waveguide interface, and not requiring the MMIC chip to adopt the bump process to form the flip-chip, buried and other forms, thus greatly simplifying the packaging difficulty of the millimeter wave band level MMIC chip, and at the same time, the micro-coaxial energy form can be easily transformed into a standard surface mount interface through impedance transformation and vertical transfer without causing signal loss, so this packaging structure is an efficient millimeter wave MMIC packaging form.

[0063] Since the micro-coaxial adapter is used as the transition lead of the MMIC chip, a shorter gold wire lead structure can be used at the MMIC chip end to form a coplanar waveguide with the ground-signal-ground pins on the chip and the micro-coaxial adapter. In this form, the length of the gold wire lead is very short, and the micro-coaxial adapter can transmit signals in TEM mode at a frequency of 0~450GHz. The insertion loss of the micro-coaxial adapter can be maintained at 0.2dB / cm, and the output port can be easily converted into a standard SMT RF interface through impedance transformation. Therefore, using micro-coaxial form as the signal transmission form of the package can have lower insertion loss.

[0064] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A micro-coaxial transfer MMIC surface mount packaging structure, characterized in that: include: A packaging chamber enclosed by an upper cover plate (12) and a lower cover plate (11), wherein a radio frequency switching port (16) is provided on a side wall of the packaging chamber; An MMIC chip (13) and a micro-coaxial adapter component (14) are arranged inside the packaging chamber, one end of the micro-coaxial adapter component (14) is connected to the radio frequency interface of the MMIC chip (13), and the other end extends to the radio frequency adapter port (16); The radio frequency transfer port (16) is located on a side of the lower cover plate (11) away from the upper cover plate (12); the micro-coaxial transfer component (14) is a vertical structure, and vertically transfers the MMIC chip (13) located inside the packaging cavity to the radio frequency transfer port (16); The micro-coaxial adapter assembly (14) comprises an intermediate transmission conductor (141) and a shielding cavity (142) located outside the intermediate transmission conductor (141).

2. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 1, characterized in that: The radio frequency switching port (16) is located on a side of the lower cover plate (11) away from the upper cover plate (12); the intermediate transmission conductor (141) comprises a first lead-out portion and a second lead-out portion which are perpendicular to each other; the first lead-out portion is parallel to the plane where the lower cover plate (11) is located, and one end of the first lead-out portion is connected to the radio frequency interface of the MMIC chip (13), and the other end of the first lead-out portion is connected to the second lead-out portion; the second lead-out portion is perpendicular to the plane where the lower cover plate (11) is located, and the other end of the second lead-out portion is flush with the radio frequency switching port (16) at the bottom of the lower cover plate (11).

3. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 1, characterized in that: The radio frequency interface and the intermediate transmission conductor (141) are interconnected via a gold wire lead.

4. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 1, characterized in that: The micro-coaxial adapter component (14) is a micro-coaxial adapter component (14) in an impedance conversion form.

5. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 1, characterized in that: The number of the micro-coaxial adapter components (14) corresponds one-to-one to the number of radio frequency interfaces in the MMIC chip (13).

6. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 1, characterized in that: A DC transfer port (15) is provided on the side wall of the packaging chamber, a DC interface is provided in the MMIC chip (13), and the DC interface and the DC transfer port (15) are directly interconnected via gold wire leads.

7. The MMIC surface mount packaging structure of micro-coaxial transfer according to claim 6, characterized in that: The DC switching port (15) and the radio frequency switching port (16) are located on a side of the lower cover plate (11) away from the upper cover plate (12).

8. A method for preparing a micro-coaxial transfer MMIC surface mount packaging structure, characterized in that: include: A chip reserved groove (22) is processed on the top of the lower cover plate (11), and a radio frequency switching port (16) is processed on the bottom of the lower cover plate (11); A micro-coaxial adapter component (14) is prepared on the top of the upper cover plate (12) by using a micro-machining process; one end of the micro-coaxial adapter component (14) is connected to the radio frequency interface of the MMIC chip (13), and the other end extends to the radio frequency adapter port (16) and is flush with the radio frequency adapter port (16) at the bottom of the lower cover plate (11); The upper cover plate (12) covers the top of the lower cover plate (11) and is assembled to form a micro-coaxial switching MMIC surface mount packaging structure.

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