W-band waveguide sealing structure

Abstract

The application discloses a novel W-waveband waveguide sealing structure, which adopts a three-dimensional stacked structure and is divided into four layers, wherein the two outer layers are clamps and the two middle layers are sealing modules; a dielectric substrate is welded in a cavity in the middle of the sealing modules by adopting a three-layer welding structure. The novel W-waveband waveguide sealing structure can be directly used for the connection of a real measurement or radio frequency transmission system without other conversion and transition structures; meanwhile, the operability of the process is fully considered, and the assembly error is less than 5 microns. The novel W-waveband waveguide sealing structure can realize the performance of air-tight packaging, wide bandwidth and low insertion loss.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and particularly to a W-band waveguide sealing structure. Background Technology

[0002] The W-band covers a frequency range of 75-110 GHz. Although it is on the edge of the terahertz band, it is still an important window frequency in the millimeter wave and terahertz bands.

[0003] Currently, the development of RF components for the W-band is rapid. Traditional RF components, due to the openness of their waveguide ports to the external environment, are susceptible to external impurities entering the cavity during prolonged operation, affecting module reliability. Therefore, sealing of the waveguide ports is necessary. Conventional waveguide port sealing methods include using waveguide windows, multilayer circuit boards such as LTCC, or waveguide-microstrip conversion structures. However, in the terahertz band, high dimensional accuracy is required, and assembly is difficult. Waveguide window sealing structures achieve narrow bandwidth, are significantly affected by processing and assembly, and generate substantial insertion loss. Glass beads are mainly used for sealing low-frequency devices, and it is difficult to guarantee assembly accuracy in the W-band. LTCC is complex and expensive to process, and introduces additional losses. Furthermore, existing W-band dielectric sealing structures use LCP substrate ULTRALAM3850 and Sn... 62 Pb 36 The lower cavity seal was completed by reflow soldering with Ag2 at 180℃, and the insertion loss was less than 3dB and the leakage rate was less than 1×10⁻⁶. -9 Pa·m 3 / s, the liquid polymer sheet ULTRALAM3850 will melt at 330℃ and is not heat-resistant. Sn 62 Pb 36 Ag2 solder is prone to migration and has poor reliability. Under high temperature and high humidity conditions, the solder is prone to oxidation and degeneration, and the insertion loss is relatively large. Summary of the Invention

[0004] In view of this, the present invention proposes a W-band waveguide sealing structure based on a waveguide-microstrip conversion structure. This structure uses a back-to-back method to achieve sealing of the waveguide port. The structure is simple. By designing solderable and solder-resistant areas in the microstrip structure and using Au alloy solder for double-sided welding, it achieves a wider bandwidth and lower loss while ensuring airtightness.

[0005] To achieve this objective, a W-band waveguide sealing structure is provided, the structure comprising: a clamp, a sealing module located in the middle of the clamp, and a dielectric substrate located in the middle cavity of the sealing module;

[0006] The clamp is a two-layered, segmented clamp, with a wave guide port hole provided on the side of the lower segment clamp.

[0007] The sealing module includes upper and lower sealing blocks, and cavities are opened on the opposite surfaces of the upper and lower sealing blocks. The lower sealing block cavity is provided with a waveguide through hole, and the upper sealing block cavity is provided with a solder groove.

[0008] The dielectric substrate is an H-plane probe, with its dielectric surface perpendicular to the waveguide transmission direction and centrally welded and fixed in the cavity of the lower sealing block. The dielectric substrate covers the waveguide port introduced from the waveguide through hole of the sealing block.

[0009] The dielectric substrate is provided with a signal transmission area, a solderable area and a solder resist area. The gold-plated microstrip line in the middle of the dielectric substrate serves as the signal transmission area, connecting the input waveguide port and the output waveguide port introduced from the waveguide through-hole of the sealing block. The gold-plated area at the edge of the dielectric substrate serves as the solderable area, and the bare die between the signal transmission area and the solderable area serves as the solder resist area.

[0010] The sealing module and the dielectric substrate adopt a three-layer welding structure. The bottom layer of solder connects the lower sealing block cavity to the dielectric substrate, the middle layer of solder positions the dielectric substrate, and the top layer of solder seals the dielectric substrate and the upper sealing block.

[0011] Preferably, the distance between the edge of the dielectric substrate and the edge of the sealing structure is 75 μm.

[0012] Preferably, the dielectric substrate is a quartz substrate, and both the front and back sides of the dielectric substrate are gold-plated.

[0013] Preferably, the cavity material of both the upper and lower sealing blocks is aluminum alloy, and the inner surface of the cavity is electroplated with nickel-gold.

[0014] Preferably, metal pillars are provided around the upper and lower sealing blocks.

[0015] Preferably, all right angles within the cavities of the upper and lower sealing blocks are rounded with a radius of 0.2 mm.

[0016] Preferably, the bottom layer solder and the intermediate layer solder are welded simultaneously.

[0017] Preferably, the lower sealing block and the upper sealing block are aligned with pins and gas-tightly sealed by vacuum sintering.

[0018] The beneficial effects of this invention are as follows: The W-band waveguide sealing structure proposed in this application achieves waveguide port sealing based on a waveguide-microstrip conversion structure design. In this conversion structure, the microwave signal is converted from the rectangular waveguide to the microstrip line through probe coupling, and the sealing structure is a back-to-back structure of the waveguide-microstrip conversion structure. This structure has the following advantages:

[0019] (1) The structure adopts a three-dimensional stacked structure, which is divided into four layers. The sealing module is mainly concentrated in the middle two layers, which can be taken out and assembled separately. The other two layers are fixtures used for integrating flanges. The main structure of the sealing module is concentrated in the middle two layers for easy assembly. The fixtures are part of the entire sealing module. The integrated flange can be directly used for connection to the test or radio frequency transmission system without other conversion transition structures. At the same time, the operability of the process is fully considered, which makes it easy to assemble and the assembly error is less than 5μm.

[0020] (2) The dielectric substrate and the sealing module adopt a three-layer welding structure. The upper and lower surfaces of the dielectric substrate are welded to the cavity of the sealing structure on both sides. Solder is set in the middle layer to precisely fix the position of the dielectric substrate and assist the waveguide port alignment. Secondly, the middle solder layer provides space between the substrate and the structure to prevent the structure and substrate from deforming due to thermal expansion during welding reflow, which could cause the substrate to break due to compression.

[0021] The W-band waveguide sealing structure provided in this application was tested, and the results show that within a bandwidth range of 76-96.5 GHz, the insertion loss of this structure is less than 1 dB, the return loss is less than -15 dB, and the leakage rate is 2.2 × 10⁻⁶. -11 Pa·m 3 / s, lower than the rejection rate limit of 5×10⁻⁶ specified in GJB548B method 1014.2. -9 Pa·m 3 / s, enabling structural hermetically sealed packaging, wide bandwidth and low insertion loss performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the W-band waveguide sealing structure in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the front side of the dielectric substrate of the W-band waveguide sealing structure in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the back side of the dielectric substrate of the W-band waveguide sealing structure in an embodiment of the present invention;

[0025] Figure 4 This is a partial schematic diagram of the solder and dielectric substrate in the W-band waveguide sealing structure of this invention embodiment;

[0026] In the figure: 1. Fixture 2. Sealing module 1.1. Upper lobe fixture 1.2. Lower lobe fixture 1.3. Waveguide inlet hole 2.1. Upper sealing block 2.2. Lower sealing block 2.3. Waveguide through hole 2.4. Solder groove 3. Dielectric substrate 3.1. Gold layer; 4. Solder. Detailed Implementation

[0027] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

[0028] This application presents a W-band waveguide sealing structure that achieves waveguide port sealing through soldering using a back-to-back structure of H-plane dielectric substrates (the dielectric substrate is inserted from the wide side of the waveguide, and the probe is perpendicular to the narrow wall of the waveguide). The sealing structure is fabricated using CNC technology and a three-dimensional stacked structure. The entire module consists of four layers, with the middle two layers being the sealing module and the other two layers being the fixture. No other conversion or transition structures are required, and it can be directly used for connection in experimental or RF transmission systems.

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] like Figures 1-3 The W-band waveguide sealing structure shown includes: a clamp 1, a sealing module 2 located in the middle of the clamp 1, and a dielectric substrate 3 located in the middle cavity of the sealing module;

[0031] Among them, the clamp 1 is a split upper and lower layer, and the lower plate clamp 1.2 is provided with a wave guide port hole 1.3 on the side. The waveguide is introduced into the sealing module 2 through the wave guide port hole 1.3 for sealing.

[0032] The sealing module 2 includes upper and lower sealing blocks. Cavities are formed on the opposing surfaces of the upper and lower sealing blocks. The lower sealing block 2.2 has a waveguide through hole 2.3 in its cavity for introducing the waveguide port to be sealed. The upper sealing block 2.1 has a solder groove 2.4 in its cavity for providing space to accommodate solder for welding the dielectric substrate.

[0033] like Figures 2-3 As shown, the dielectric substrate 3 is centrally welded and fixed in the cavity of the lower sealing block 2.2, covering the waveguide port introduced from the waveguide through-hole 2.3 of the sealing block. Both the front and back sides of the dielectric substrate 3 are plated with gold layers 3.1. A gold microstrip line connecting the input waveguide port and the output waveguide port is plated in the middle of its front side as a signal transmission area to realize waveguide-microstrip conversion. The edges are plated with gold layers as solderable areas, and the remaining bare die is a solder resist area.

[0034] like Figure 4As shown, the sealing module 2 and the dielectric substrate 3 are achieved through CNC machining, employing a three-layer welded structure. The bottom layer solder connects the lower sealing block 2.2 cavity to the dielectric substrate 3; the middle layer solder positions the dielectric substrate 3; and the top layer solder seals the dielectric substrate 3 to the upper sealing block 2.1. In this embodiment, the bottom layer solder is 50 μm thick, the dielectric substrate is 127 μm thick, the middle solder is 100 μm thick, and the top layer is 50 μm thick. The upper sealing block 2.1 and the lower sealing block 2.2 are aligned using pins.

[0035] As an example, solder 4 is selected from Au alloy solder, which is a common lead-free solder. Currently, AuSn, AuGe, AuSi and other types are mainly used. Au alloy solder has good wettability at the metal interface, high welding strength, and does not require the addition of flux. The material has high stability, corrosion resistance and wettability. In the field of electronic packaging, it is a commonly used high-reliability solder.

[0036] During the assembly of the above structure, the bottom layer solder and the middle layer solder are welded simultaneously to achieve precise alignment of the dielectric substrate and hermetically sealed assembly of the lower sealing block 2.2. After the dielectric substrate 3 is welded, the lower sealing block 2.2 is reversed, the upper layer solder is assembled, and the upper and lower sealing blocks are aligned by pins. Then, the hermetically sealed assembly of the upper sealing block 2.1 is completed by vacuum sintering.

[0037] As an example, in order to avoid resonance, it is necessary to control the assembly accuracy between the dielectric substrate 3 and the waveguide port. The distance between the edge of the dielectric substrate 3 and the edge of the structure is 75μm±5μm, and the assembly accuracy is controlled within 5μm.

[0038] As an example, the dielectric substrate 3 is a quartz substrate with a dielectric constant of 3.78 and a thickness of 0.127 mm, and both the front and back sides of the dielectric substrate 3 are gold-plated.

[0039] As an example, the cavity material of the upper sealing block 2.1 and the lower sealing block 2.2 is aluminum alloy, and the inner surface of the cavity is electroplated with nickel gold; in addition to the space for placing the quartz substrate, the cavity of the sealing block also needs to reserve space for solder; as an example, in order to control the position of the quartz substrate, metal pillars are set around the sealing block to prevent the quartz substrate from sliding too far and affecting the sealing performance; all right angles in the cavities of the upper and lower sealing blocks are rounded with a radius of 0.2mm to fit the drill bit size in the CNC process.

[0040] The W-band waveguide sealing structure proposed in this invention can replace common waveguide windows, LTCC and other multi-layer circuit board waveguide port sealing structures, and can also replace complex waveguide-microstrip conversion structures with multiple stepped waveguide transitions.

Claims

1. A W-band waveguide sealing structure, characterized in that, The structure includes: a clamp, a sealing module located in the middle of the clamp, and a dielectric substrate located in the middle cavity of the sealing module; The clamp is a two-layered, segmented clamp, with a wave guide port hole provided on the side of the lower segment clamp. The sealing module includes upper and lower sealing blocks, and cavities are opened on the opposite surfaces of the upper and lower sealing blocks. The lower sealing block cavity is provided with a waveguide through hole, and the upper sealing block cavity is provided with a solder groove. The dielectric substrate is an H-plane probe, with its dielectric surface perpendicular to the waveguide transmission direction and centrally welded and fixed in the cavity of the lower sealing block. The dielectric substrate covers the waveguide port introduced from the waveguide through hole of the sealing block. The dielectric substrate is provided with a signal transmission area, a solderable area and a solder resist area. The gold-plated microstrip line in the middle of the dielectric substrate serves as the signal transmission area, connecting the input waveguide port and the output waveguide port introduced from the waveguide through-hole of the sealing block. The gold-plated area at the edge of the dielectric substrate serves as the solderable area, and the bare die between the signal transmission area and the solderable area serves as the solder resist area. The sealing module and the dielectric substrate adopt a three-layer welding structure. The bottom layer of solder connects the lower sealing block cavity to the dielectric substrate, the middle layer of solder positions the dielectric substrate, and the top layer of solder seals the dielectric substrate and the upper sealing block.

2. The W-band waveguide sealing structure according to claim 1, characterized in that, The distance between the edge of the dielectric substrate and the edge of the sealing structure is 75 μm.

3. The W-band waveguide sealing structure according to claim 1, characterized in that, The dielectric substrate is a quartz substrate, and both the front and back sides of the dielectric substrate are gold-plated.

4. The W-band waveguide sealing structure according to claim 1, characterized in that, The cavities of both the upper and lower sealing blocks are made of aluminum alloy, with nickel-gold electroplated on the inner surface of the cavities.

5. The W-band waveguide sealing structure according to claim 1, characterized in that, Metal pillars are arranged around the upper and lower sealing blocks.

6. The W-band waveguide sealing structure according to claim 1, characterized in that, All right angles within the cavities of the upper and lower sealing blocks are rounded with a radius of 0.2 mm.

7. The W-band waveguide sealing structure according to claim 1, characterized in that, The bottom layer solder and the middle layer solder are welded simultaneously.

8. The W-band waveguide sealing structure according to claim 1, characterized in that, The lower sealing block and the upper sealing block are aligned with pins and gas-tightly sealed by vacuum sintering.

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