A W-band packaging structure

Abstract

The present invention discloses a W-band packaging structure, comprising: a packaging shell and a chip; the packaging shell comprises a packaging substrate and a plastic packaging shell; the packaging substrate comprises an upper surface metal circuit layer and a lower surface metal circuit layer, the upper surface metal circuit layer comprises a substrate integrated waveguide structure, a substrate integrated waveguide to microstrip structure and a connector; the lower surface metal circuit layer comprises a substrate integrated waveguide to air waveguide structure; the chip is arranged on the upper surface metal circuit layer and connected to the connector; the plastic packaging shell is arranged on the packaging substrate, and the chip is packaged in the plastic housing. Through this special structural design, the present invention proposes a new solution for W-band chip packaging. Compared with the traditional transmission line structure transmission, it not only reduces the loss between signal transmission, but also meets the index requirements of the radio frequency chip, while improving the production efficiency and reducing the production cost.

Description

Technical Field

[0001] The invention relates to the technical field of microwave packaging, and in particular to a W-band packaging structure. Background Art

[0002] The invention patent with publication number CN112563237A involves an impedance matching design for compound GaAs (gallium arsenide) chips, which adopts a "two-step" form of "coplanar waveguide-quasi-coaxial-stripline-quasi-coaxial-coplanar waveguide". However, this design will cause great losses at ultra-high frequencies, especially when it rises to the W band.

[0003] The invention patent with publication number CN114334919A involves a waveguide transition structure specifically for the CMOS (complementary metal compound) process and a wafer packaging process. This patent processes the loss of RF transmission at the wafer level and shortens the transmission line length and reduces transmission loss through RDL (rewiring) design. This patent directly designs the waveguide on the wafer, which solves the COMS packaging problem to a certain extent. However, this patent requires RDL on both sides, the chip needs to be thinned, a waveguide antenna structure design is used on the front side, and the back RDL needs to be designed with a through hole to connect to the front side. The process steps are more complicated, the cost is higher, the efficiency will be greatly reduced, and it is not applicable to GaAs chip packaging.

[0004] The foreign manufacturer Gotmic has a suitable SMD packaging structure design for W-band compound GaAs chips. However, due to the direct use of microstrip probe to air waveguide form, the inside of the package is in direct contact with the outside world, lacks airtightness, and has defects in reliability.

[0005] The invention patent with publication number CN 113871368 A adopts the form of microwave probe to waveguide for W-band compound GaAs chips, and on this basis, adopts ceramic sealing packaging. The waveguide conversion adopts dielectric waveguide conversion, which ensures the transmission of RF signals while taking into account airtightness. However, the development cycle is long and the manufacturing process requirements are complex, resulting in high economic costs. Summary of the invention

[0006] The purpose of the present invention is to propose a W-band packaging structure to reduce the loss between signal transmissions and take into account both efficient development cycle and relatively low economic cost while ensuring airtightness.

[0007] In order to achieve the above object, the present invention provides a W-band packaging structure, including: a packaging shell and a chip;

[0008] The packaging shell comprises a packaging substrate and a plastic packaging shell;

[0009] The packaging substrate comprises an upper surface metal circuit layer and a lower surface metal circuit layer, wherein the upper surface metal circuit layer comprises a substrate integrated waveguide structure, a substrate integrated waveguide-to-microstrip structure and a connector; and the lower surface metal circuit layer comprises a substrate integrated waveguide-to-air waveguide structure;

[0010] The chip is arranged on the upper surface metal circuit layer and connected to the connecting member;

[0011] The plastic package shell is arranged on the packaging substrate, and the chip is packaged in the plastic package shell.

[0012] Optionally, the connecting component includes a microstrip matching structure and a bonding structure, the microstrip matching structure is connected to the substrate integrated waveguide to microstrip structure, and the bonding structure connects the microstrip matching structure and the chip.

[0013] Optionally, the chip is a GaAs chip, and the bonding structure is a gold wire bonding structure.

[0014] Optionally, the chip is a CMOS chip, and the bonding structure is a ball-planting welding structure.

[0015] Optionally, the packaging substrate further includes an organic medium substrate, and the organic medium substrate is an organic composite substrate with a low dielectric constant and a low tangent loss angle.

[0016] Optionally, the upper surface metal circuit layer and the lower surface metal circuit layer are both made of pure copper with a gold-plated structure.

[0017] Optionally, the chip and the upper surface metal circuit layer are fixed by bonding with conductive adhesive or by physical pressing.

[0018] Optionally, the plastic package shell is made of epoxy resin material.

[0019] Optionally, a metal connector is further included, which is arranged in the packaging substrate and connects the upper surface metal circuit layer and the lower surface metal circuit layer.

[0020] Optionally, the metal connector at least surrounds the substrate integrated waveguide to air waveguide structure, the substrate integrated waveguide to microstrip structure and the microstrip matching structure.

[0021] Compared with the prior art, in the present invention, the microwave signal is input from the substrate integrated waveguide to the air waveguide structure, and then the signal is transmitted inside the packaging substrate through the dielectric waveguide to the substrate integrated waveguide, and the radio frequency signal input from the standard waveguide port is converted into a substrate integrated waveguide transmission signal, which is transmitted in the substrate integrated waveguide structure, and the signal is converted into a microstrip signal through the substrate integrated waveguide to microstrip structure, and then transmitted to the chip through the connector, and the signal is processed inside the chip; through this special structural design, the present invention proposes a new solution for W-band chip packaging. Compared with the traditional transmission line structure transmission, it not only reduces the loss between signal transmission, but also meets the index requirements of the radio frequency chip, while improving the production efficiency and reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a side view of the W-band packaging structure in the first embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the upper surface metal circuit layer in the first embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the metal circuit layer on the lower surface in the first embodiment of the present invention;

[0025] Figure 4 is a cross-sectional view of the W-band packaging structure in the first embodiment of the present invention;

[0026] Figure 5 This is a W-band packaging simulation data diagram in Embodiment 1 of the present invention;

[0027] Figure 6 It is a cross-sectional view of the W-band packaging structure in the second embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in more detail below in conjunction with the schematic diagram, wherein the preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein, and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art, and not as a limitation of the present invention.

[0029] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0030] Please refer to Figure 1 , in the present invention, a W-band packaging structure is proposed, comprising: a packaging shell and a chip 1;

[0031] The packaging shell includes a packaging substrate 2 and a plastic packaging shell 5;

[0032] The packaging substrate 2 includes an upper surface metal circuit layer 21 and a lower surface metal circuit layer 23, wherein the upper surface metal circuit layer 21 includes a substrate integrated waveguide structure 211, a substrate integrated waveguide to microstrip structure 212 and a connector; the lower surface metal circuit layer 23 includes a substrate integrated waveguide to air waveguide structure 231;

[0033] The chip 1 is disposed on the upper surface metal circuit layer 21 and connected to the connecting member;

[0034] The plastic package shell 5 is disposed on the packaging substrate 2 , and the chip 1 is packaged in the plastic package shell 5 .

[0035] In the present invention, the external microwave signal enters through the air waveguide 6, the microwave signal is input through the substrate integrated waveguide to air waveguide structure 231, and then the signal is transmitted inside the packaging substrate 2 through the dielectric waveguide to substrate integrated waveguide, the radio frequency signal input from the standard waveguide port is converted into a substrate integrated waveguide transmission signal, and transmitted in the substrate integrated waveguide structure 211, the signal is converted into a microstrip signal through the substrate integrated waveguide to microstrip structure 212, the signal is transmitted to the chip 1 through the connector, the signal is processed in the chip 1, and finally output from the output end (not shown); the structural design of the present invention has high production efficiency, low production cost, excellent sealing, and reduced signal transmission loss.

[0036] Embodiment 1

[0037] For details, please refer to Figure 1-4 In one embodiment, the present invention proposes a W-band packaging structure, including a packaging shell, a compound GaAs (gallium arsenide) chip 1;

[0038] The packaging shell includes a packaging substrate 2 and a plastic packaging shell 5;

[0039] The plastic package shell adopts a plastic package material with high frequency performance, such as epoxy resin.

[0040] The packaging substrate 2 includes an organic medium substrate 22, an upper surface metal circuit layer 21, a lower surface metal circuit layer 23 and a metal connector 4; the organic medium substrate 22 adopts an organic composite substrate with a low dielectric constant (Dk≤3.7) and a low tangent loss angle (Df≤0.003), the upper surface metal circuit layer 21 and the lower surface metal circuit layer 23 are both made of pure copper with a thickness range of 15-18μm, and a layer of gold with a thickness range of 0.05-0.1μm is plated on the surface of the circuit layer.

[0041] The upper surface metal circuit layer 21 includes a substrate integrated waveguide structure 211 and a substrate integrated waveguide to microstrip structure 212 ; the lower surface metal circuit layer 23 includes a substrate integrated waveguide to air waveguide structure 231 .

[0042] The chip 1 is fixed on the upper surface metal circuit layer 21; the two are fixedly connected by conductive glue.

[0043] The plastic package housing 5 is fixed on the organic medium substrate 22 , and the chip 1 and the organic medium substrate 22 are both packaged in the plastic package housing 5 .

[0044] In this embodiment, a microstrip matching structure 213 and a bonding structure 3 are also included. The microstrip matching structure 213 is connected to the substrate integrated waveguide to microstrip structure 212. The bonding structure 3 connects the microstrip matching structure 213 and the chip 1. The signal is transmitted to the chip 1 through the microstrip matching structure 213 and the bonding structure 3.

[0045] As an example, the bonding structure 3 is a gold wire, and the gold wire bonding material is a high-purity gold wire (the gold content is not less than 999.9‰). For example, the gold wire is connected to the pad 11 of the chip 1.

[0046] In this embodiment, to realize the function of the present invention, it is necessary to design an opening on the metal circuit layer 23 on the lower surface of the dielectric substrate, that is, the substrate integrated waveguide to air waveguide structure 231, as a channel for signals from the outside to the inside of the package.

[0047] A substrate integrated waveguide design is performed on the metal circuit layer on the upper surface of the medium and the metal circuit layer on the lower surface, and the input signal is transmitted in this structural design.

[0048] A microstrip circuit is designed on the metal circuit layer on the upper surface of the medium, and the signal in the substrate integrated waveguide is transmitted in this structural design.

[0049] A gold wire bonding design is performed between the microstrip line of the metal circuit layer on the upper surface of the medium and the compound chip, and the signal in the microstrip line is transmitted to the compound chip for processing through the gold wire.

[0050] Specifically, in this embodiment, Figure 3 The substrate integrated waveguide to air waveguide structure 231 serves as the signal input port of the entire packaging structure, and converts the radio frequency signal from the standard waveguide structure to the substrate integrated waveguide structure through the opening design.

[0051] Furthermore, in the embodiment of the present invention, a metal connector 4 is further included, which is disposed in the packaging substrate 2 and connects the upper surface metal circuit layer 21 and the lower surface metal circuit layer 23. The ground of the chip is connected to the ground of the organic medium substrate through the metal connector 4, and at the same time, the signal is shielded to ensure that the signal is transmitted only within the structure formed by the metal connector 4.

[0052] For example, the metal connector 4 at least surrounds the substrate integrated waveguide to air waveguide structure 231 , the substrate integrated waveguide to microstrip structure 212 , and the microstrip matching structure 213 .

[0053] During transmission, the microwave signal is input from the substrate integrated waveguide to air waveguide structure 231, and then transmitted inside the packaging substrate 2 through the dielectric waveguide to substrate integrated waveguide, and the radio frequency signal input from the standard waveguide port is converted into a substrate integrated waveguide transmission signal, which is transmitted in the substrate integrated waveguide structure. The signal is converted into a microstrip signal through the substrate integrated waveguide to microstrip structure 212, and the metal connector 4 shields the radio frequency signal of the entire transmission process in the designed structure. The signal is transmitted to the chip 1 through the microstrip matching structure 213 and the gold wire 3, and the signal is processed in the compound GaAs chip 1. The processed signal is then transmitted through the mirror structure (not shown), and finally output from the microwave conversion opening (not shown) at the output end.

[0054] The signal input port in this embodiment adopts the structural design of substrate integrated waveguide to air waveguide structure 231, and performs input matching with the standard waveguide port. The opening size of the substrate integrated waveguide to air waveguide structure obtained by this design is 1mm-3mm long and 0.3mm-0.7mm wide. In this embodiment, preferably, the opening size is 2mm long and 0.5mm wide. Compared with the traditional coaxial line transmission structure, the loss of RF signal is greatly reduced, and the design of different frequency bands requires simulation modification of the waveguide port opening size.

[0055] This embodiment uses a substrate integrated waveguide structure 211 in signal transmission, which greatly reduces the loss in the RF signal transmission process compared with microstrip line and microstrip probe transmission methods, and simplifies the structural design.

[0056] In the signal transmission of this embodiment, a substrate integrated waveguide to microstrip structure 212 is adopted to facilitate gold wire bonding of the RF chip. By matching the impedance network, the substrate integrated waveguide to microstrip structure 212 is obtained as a trapezoid with an upper side length of 0.4mm-0.7mm, a lower side length of 0.1mm-0.3mm, and a width of 0.6mm-1.0mm. In this embodiment, preferably, the structure size is 0.6mm in upper side length, 0.2mm in lower side length, and 0.8mm in height. For designs of different frequency bands, the size of the substrate integrated waveguide to microstrip structure needs to be modified through simulation.

[0057] In the signal transmission of this embodiment, the microstrip line is bonded to the chip 1 through the gold wire 3, and the gold wire bonding matching structure 213 performs impedance matching on the signal transmission, so that the gold wire bonding matching structure 213 is a rectangle with a length of 0.2-0.3mm and a width of 0.4-0.5mm. In this embodiment, preferably, the structure size is 0.25mm long and 0.45mm wide, and for designs of different frequency bands, the size of the gold wire bonding matching structure needs to be modified through simulation.

[0058] Figure 5 This is the structural simulation result of this embodiment. The center frequency used in this structural design is 94G. As shown in the figure, in the range of 92.6GHz-97.6GHz, the insertion loss is less than 1dB, and the insertion loss at a frequency of 94GHz is only 0.6dB. The design structure is reasonable and the insertion loss meets the design requirements.

[0059] In the embodiment of the present invention, the signal is transmitted through the metal circuit layer on the upper surface of the dielectric substrate and the metal circuit layer on the lower surface of the substrate, and the path of microwave signal transmission is minimized. Compared with the microstrip probe to air waveguide structure, a waveguide reflection cavity is not required, and a very long microstrip line is not required, which greatly simplifies the structural design and reduces the transmission loss.

[0060] Embodiment 2

[0061] Specifically, in another embodiment, please refer to Figure 6 The present invention is directed to a packaging structure of a W-band radio frequency chip based on a CMOS process, comprising a packaging shell and a CMOS chip 10;

[0062] The packaging shell includes a packaging substrate 2 and a plastic packaging shell 5;

[0063] The plastic package shell 5 is made of a plastic package material with high frequency performance, such as epoxy resin.

[0064] The packaging substrate 2 includes an organic medium substrate 22, an upper surface metal circuit layer 21, a lower surface metal circuit layer 23 and a metal connector 4; the organic medium substrate 22 adopts an organic composite substrate with a low dielectric constant (Dk≤3.7) and a low tangent loss angle (Df≤0.003), the upper surface metal circuit layer 21 and the lower surface metal circuit layer 23 are both made of pure copper with a thickness range of 15-18μm, and a layer of gold with a thickness range of 0.05-0.1μm is plated on the surface of the circuit layer.

[0065] The upper surface metal circuit layer 21 includes a substrate integrated waveguide structure and a substrate integrated waveguide to microstrip structure; the lower surface metal circuit layer 23 includes a substrate integrated waveguide to air waveguide structure.

[0066] The CMOS chip 10 is fixed on the upper surface metal circuit layer 21 ; the two are welded via chip implantation 110 .

[0067] The plastic package housing 5 is fixed on the organic medium substrate 22 , and the CMOS chip 10 and the organic medium substrate 22 are both packaged in the plastic package housing 5 .

[0068] In this embodiment, a microstrip matching structure and a bonding structure are also included. The microstrip matching structure is connected to the substrate integrated waveguide to microstrip structure. The bonding structure connects the microstrip matching structure and the chip 10. The signal is transmitted to the chip 10 through the microstrip matching structure and the bonding structure.

[0069] As an example, the CMOS chip 10 is first packaged by Fanout (fan-out packaging) or CSP (chip-scale packaging), and the packaged chip is ball-planted. The chip ball planting adopts lead-free solder, and the transmission between the chip and the microstrip line is established through the ball planting on the chip.

[0070] In this embodiment, to realize the function of the present invention, it is necessary to design an opening in the metal circuit layer 23 on the lower surface of the dielectric substrate, that is, the substrate integrated waveguide to air waveguide structure serves as a channel for signals from the outside to the inside of the package.

[0071] The substrate integrated waveguide design is performed on the upper surface metal circuit layer 21 and the lower surface metal circuit layer 23 of the medium, and the input signal is transmitted in this structural design.

[0072] A microstrip circuit design is performed on the metal circuit layer 21 on the upper surface of the medium, and the signal in the substrate integrated waveguide is transmitted in this structural design.

[0073] The CMOS chip 10 is first packaged by Fanout (fan-out packaging) or CSP (chip-scale packaging), and the packaged chip is ball-planted. Through the ball planting on the chip, the transmission between the chip and the transmission line is established.

[0074] Specifically, in this embodiment, the substrate integrated waveguide to air waveguide structure serves as the signal input port of the entire packaging structure, and the radio frequency signal is converted from the standard waveguide structure to the substrate integrated waveguide structure through the opening design.

[0075] Furthermore, in the embodiment of the present invention, a metal connector 4 is also included. The metal connector 4 is disposed in the packaging substrate and connects the upper surface metal circuit layer 21 and the lower surface metal circuit layer 23 .

[0076] During transmission, the microwave signal is input from the substrate integrated waveguide to the air waveguide structure, and then transmitted inside the packaging substrate through the dielectric waveguide to the substrate integrated waveguide. The RF signal input from the standard waveguide port is converted into a substrate integrated waveguide transmission signal and transmitted in the substrate integrated waveguide structure. The signal is converted into a microstrip signal through the substrate integrated waveguide to microstrip structure. The metal connector 4 shields the RF signal of the entire transmission process in the designed structure. The signal is transmitted to the CMOS chip 10 through the pads on the microstrip line (not shown) and the chip implant 110. The signal is processed in the CMOS chip 10 and finally output from the output end.

[0077] To sum up, in the implementation of the present invention, the signal is transmitted through the metal circuit layer on the upper surface of the dielectric substrate and the metal circuit layer on the lower surface of the substrate, and the path of microwave signal transmission is minimized. Compared with the microstrip probe to air waveguide structure, no waveguide reflection cavity is required, and no long microstrip line is required, which greatly simplifies the structural design and reduces transmission loss; the dielectric substrate adopts an organic composite substrate, which has cheap materials, simple processes and short processing time; the packaging shell is made of plastic material, which has cheap materials and short processing time compared with metal packaging.

[0078] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A W-band packaging structure, characterized in that: include: Packaging shell and chip; The packaging shell includes a packaging substrate and a plastic packaging shell; The packaging substrate comprises an upper surface metal circuit layer and a lower surface metal circuit layer, wherein: The upper surface metal circuit layer includes a substrate integrated waveguide structure, a substrate integrated waveguide-to-microstrip structure, and a connector; the connector includes a microstrip matching structure and a bonding structure, the microstrip matching structure is connected to the substrate integrated waveguide-to-microstrip structure, and the microwave signal is transmitted in the upper surface metal circuit layer through the substrate integrated waveguide structure; The lower surface metal circuit layer includes a substrate integrated waveguide to air waveguide structure; The upper surface metal circuit layer is electrically connected to the lower surface metal circuit layer through a metal connector, and the metal connector at least surrounds the substrate integrated waveguide to air waveguide structure, the substrate integrated waveguide to microstrip structure and the microstrip matching structure; The chip is arranged on the upper surface metal circuit layer, and the bonding structure connects the microstrip matching structure and the chip; the chip and the upper surface metal circuit layer are fixed by conductive adhesive bonding or physical pressing; The plastic package shell is arranged on the packaging substrate, and the chip is packaged in the plastic package shell.

2. The W-band packaging structure according to claim 1, characterized in that: The chip is a GaAs chip, and the bonding structure is a gold wire bonding structure.

3. The W-band packaging structure according to claim 1, characterized in that: The chip is a CMOS chip, and the bonding structure is a ball-planting welding structure.

4. The W-band packaging structure according to claim 1, characterized in that: The packaging substrate also includes an organic medium substrate, and the organic medium substrate is an organic composite substrate with low dielectric constant and low tangent loss angle.

5. The W-band packaging structure according to claim 1, characterized in that: The upper surface metal circuit layer and the lower surface metal circuit layer are both made of pure copper with a gold-plated surface structure.

6. The W-band packaging structure according to claim 1, characterized in that: The plastic-sealed shell is made of epoxy resin material.

7. The W-band packaging structure according to claim 1, characterized in that: The metal connector is disposed in the packaging substrate.

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