Design method of laminated antenna printed board assembly and welding method thereof

Abstract

The application discloses a design method of a laminated antenna printed board assembly and a welding method thereof, and relates to the technical field of laminated antenna printed board assemblies. The design method is used to solve the problems of large cavity, poor grounding and warping deformation when a double-layer antenna printed board is directly welded, and the problem of forced adoption of high-cost lamination. The design method comprises the following steps: selecting a low-dielectric and low-loss base material; symmetrically designing deformation prevention and using a clamp; providing exhaust through holes and windows on an upper layer board; etching a fish scale-shaped structure gas guide on a welding surface of a lower layer board; positioning with a pin; and optimizing a welding temperature curve. The welding method comprises the following steps: screen printing solder paste and detecting; overall reflow soldering after the clamp is locked; and cooling and removing. The application cooperatively reduces the cavity and improves the grounding through the fish scale-shaped solder pad and the exhaust through hole, controls warping through the clamp, and substitutes the traditional total pressure combination of lamination with low-cost and high-reliability reflow soldering, so that the manufacturing cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board (PCB) assembly technology for multilayer antennas, and more particularly to a design method and soldering method for a multilayer antenna PCB assembly. Background Technology

[0002] With the rapid development of modern wireless communication, satellite navigation, and phased array radar technologies, various airborne, missile-borne, and portable terminal devices have placed comprehensive performance requirements on antennas, including low profile, miniaturization, wide bandwidth, low axial ratio, and wide-angle scanning. However, traditional single-layer microstrip antennas suffer from narrow bandwidth, low gain, single polarization, and poor scanning capability, making them unable to meet these requirements.

[0003] Therefore, a double-layer stacked antenna printed circuit board assembly, comprising an upper radiating structure and a lower feeding structure, which aims to achieve low-cost interconnection through soldering, has become an important antenna form due to its relatively simple structure and ability to effectively extend bandwidth. However, when using conventional soldering methods to directly interconnect the upper and lower printed circuit boards over a large area, problems such as severe voids caused by poor exhaust of solder paste volatiles and warping of the board material at high temperatures commonly occur, making it impossible to meet the stringent requirements of antennas for good grounding and high reliability in terms of soldering quality. Therefore, in actual production, to ensure component performance, it is often necessary to abandon the lower-cost soldering solution and instead adopt a high-cost, high-risk multi-lamination process to achieve reliable interconnection.

[0004] Conventional lamination manufacturing processes require the final bonding of the upper radiating plate and the lower feeding plate using prepreg. This process not only increases processing costs by approximately 25%-30% on top of the total cost, but also, due to the difficulty of bonding, is highly prone to interlayer misalignment or delamination, resulting in long production cycles and low yield rates. Against this backdrop, how to overcome the technical bottlenecks of direct welding through design innovation, thereby completely replacing the high-cost lamination process with a low-cost, high-efficiency welding technology, is a pressing issue in the field.

[0005] Specifically, existing double-layer stacked antenna printed circuit board assemblies present the following prominent technical problems when attempting direct soldering: 1. Large voids and poor grounding between boards. Traditional printed circuit boards (PCBs) typically have a full-surface metal pad design for soldering. During reflow soldering, flux volatiles cannot escape smoothly from the interface between these large pads, resulting in numerous voids remaining between the boards after soldering. These voids not only reduce the mechanical strength of the solder joints but also severely affect the electrical connection quality between the ground layers of the upper and lower PCBs, causing poor grounding and consequently deteriorating antenna radiation performance.

[0006] 2. Ineffective gas release during soldering. In the soldering of double-layer stacked antenna printed circuit board assemblies, the upper and lower printed circuit boards are tightly bonded, and the gas emitted from the solder paste can only escape from the edges between the boards. When the area between the boards is large, the gas escape path is long and the resistance is high, easily leading to gas pressure buildup between the boards. This hinders the full spread of the solder and may also cause localized incomplete solder joints or poor solder bridging.

[0007] 3. Severe warping and deformation of printed circuit board (PCB) components. During the high-temperature reflow soldering process, the PCB substrate is prone to irreversible warping and deformation due to the thermal expansion characteristics of the substrate itself and uneven heat distribution on the component. This deformation not only affects the assembly accuracy and structural reliability of the antenna components, but may also lead to uneven stress at the solder interfaces between boards, further increasing the risk of poor grounding or solder joint fatigue failure.

[0008] In this context, how to design and weld double-layer stacked antenna printed circuit board assemblies, while ensuring tight connections between boards, significantly reducing welding voids, ensuring good grounding, and effectively controlling welding warpage, so as to replace the traditional lamination process with a low-cost, high-reliability welding process, has become an urgent problem to be solved. Summary of the Invention

[0009] The first objective of this invention is to provide a design method for a stacked antenna printed circuit board assembly, which can effectively reduce soldering voids between the upper and lower printed circuit boards, improve grounding performance, and control warping deformation during the soldering process, thereby replacing the traditional high-cost lamination bonding process with a low-cost, high-reliability soldering process.

[0010] The second objective of this invention is to provide a welding method for a stacked antenna printed circuit board assembly, which enables rapid and reliable assembly and welding between the upper and lower printed circuit boards, ensuring tight connections between the boards, further reducing the welding void rate, and improving the manufacturability and electrical performance of the antenna assembly.

[0011] The technical solution of this invention to solve the first technical problem is: a design method for a stacked antenna printed circuit board assembly, wherein the printed circuit board assembly only includes an adjacent upper printed circuit board and a lower printed circuit board, comprising the following steps: S1. Selection of printed circuit board substrate: Select a substrate that meets the following requirements: relative permittivity ≤3, dielectric loss factor ≤0.0014, X / Y thermal expansion coefficient ≤16ppm / ℃, Z thermal expansion coefficient ≤25ppm / ℃, and glass transition temperature Tg ≥170℃. S2. Anti-deformation design of printed circuit board assembly: The printed circuit board stack-up structure and stack-up materials are symmetrically arranged, the circuit patterns on the printed circuit board assembly are evenly distributed, the aspect ratio of the printed circuit board is ≤2:1, and the thickness of the printed circuit board is ≥1mm; and an anti-deformation welding fixture is used to control welding warpage deformation. The anti-deformation welding fixture includes a welding base plate and a welding pressure plate. S3. Venting hole design of upper printed circuit board: An even number of venting holes are set on the non-soldering parts of the upper printed circuit board that do not affect the radiation effect. S4. Window design of the upper printed circuit board: The upper printed circuit board is made of two printed circuit board substrates laminated together. The shape of the printed circuit board substrate remains unchanged on the radiating surface, and a rectangular window is opened on the printed circuit board substrate on the soldering surface. S5. Pad design of the lower printed circuit board: The soldering surface of the lower printed circuit board is uniformly etched with a width of 0.1mm-0.15mm, leaving uniform square pads with a side length of 0.35mm-0.4mm, thereby forming a fish scale structure with a trench depth of 0.035mm. S6. Positioning design between upper and lower printed circuit boards: Positioning pin holes are set at corresponding positions on the upper and lower printed circuit boards. Through the cooperation of the positioning pin holes and the positioning pins on the welding base plate, the upper and lower printed circuit boards can be quickly aligned and installed. S7. Welding process parameter design: Reflow soldering is selected; the heating rate during preheating and welding and the cooling rate during cooling are both ≤3℃ / s; at the end of preheating and welding, the temperature difference between the maximum heat capacity and the minimum heat capacity on the printed circuit board assembly is ≤5℃; the difference between the welding setting temperature and the actual temperature of the printed circuit board assembly is ≤10℃.

[0012] As a further improvement of the present invention, in step S2, the internal circuitry of the printed circuit board should be kept symmetrical and evenly distributed.

[0013] As a further improvement of the present invention, in step S3, the exhaust holes are an even number of symmetrically arranged non-metallized holes.

[0014] As a further improvement of the present invention, in step S4, the welding surface of the upper printed circuit board is the ground layer, and the window size of the rectangular window is 13.5mm×13.5mm.

[0015] As a further improvement of the present invention, in step S5, a fish-scale structure is provided on the ground layer soldering surface of the lower printed circuit board, and ink solder resist treatment is performed on the non-soldering parts of the lower printed circuit board.

[0016] As a further improvement of the present invention, in step S6, the positioning pin hole is a non-metallized hole, and the design reference of the positioning pin hole of the upper printed circuit board and the lower printed circuit board is the same.

[0017] As a further improvement of the present invention, in step S1, the substrate is selected as TSM-DS3 substrate, which has a relative permittivity of 3.0, a dielectric loss factor of 0.0011, and thermal expansion coefficients in the X, Y, and Z directions of 10ppm / ℃, 16ppm / ℃, and 23ppm / ℃, respectively.

[0018] The technical solution of this invention to solve the second technical problem is: a welding method for a stacked antenna printed circuit board assembly, wherein the printed circuit board assembly includes an upper printed circuit board and a lower printed circuit board, the upper printed circuit board is provided with vent holes and rectangular openings, the welding surface of the lower printed circuit board is provided with a fish scale structure, and the upper and lower printed circuit boards are provided with corresponding positioning pin holes. The method includes the following steps: Step 1: Based on the size of the pads on the lower printed circuit board, pre-fabricate the stencil for solder paste printing; Step 2: Use a fully automatic printing machine with a stencil to print solder paste on the soldering surface of the lower printed circuit board, and use solder paste testing equipment to check the thickness, uniformity, integrity and accuracy of the solder paste printing to ensure that the solder paste covers 100% of the solder pads. Step 3: Using the positioning pins on the anti-deformation welding fixture, and in conjunction with the positioning pin holes on the upper and lower printed circuit boards, position and mount the upper and lower printed circuit boards. After mounting, check the tightness of the fit and lock the upper and lower printed circuit boards together using the anti-deformation welding fixture. Step 4: Reflow soldering the locked anti-deformation welding fixture together with the printed circuit board assembly; Step 5: After the printed circuit board assembly has cooled to room temperature, remove the anti-deformation welding fixture.

[0019] As a further improvement of the present invention, the anti-deformation welding fixture includes a welding base plate and a welding pressure plate. The welding base plate is provided with a positioning pin corresponding to the positioning pin hole, and the welding pressure plate is provided with a clearance pin hole corresponding to the positioning pin. The edge of the welding base plate is also provided with a screw hole, and the welding pressure plate is also provided with a locking screw that is threadedly engaged with the screw hole.

[0020] As a further improvement of the present invention, the welding temperature in step 4 is set to 235°C.

[0021] Beneficial effects Compared with the prior art, the advantages of the design method and soldering method of the stacked antenna printed circuit board assembly of the present invention are as follows: 1. By employing a fish-scale design on the soldering surface of the lower printed circuit board, a microgroove channel network with ultra-high gas conductivity is pre-installed at the bottom interface of the solder spread. During soldering, the gas volatilized from the solder paste can smoothly escape from the edge of the pad along these low-resistance grooves, significantly reducing inter-board soldering voids and greatly improving the soldering strength and grounding effect between printed circuit boards. Simultaneously, the venting hole design on the upper printed circuit board further provides a vertical release path for the gas, solving the problem of ineffective gas release during large-area inter-board soldering. 2. Through the combined use of anti-deformation design and anti-deformation welding fixtures, the warping deformation of the printed circuit board assembly under the high temperature of reflow soldering is effectively controlled, ensuring tight fit and uniform stress between the upper and lower printed circuit boards during the welding process, thus ensuring the consistency and reliability of the welding. Simultaneously, the cooperation of the locating pin holes and locating pins enables rapid alignment and installation of the upper and lower printed circuit boards, improving assembly accuracy and efficiency. 3. By carefully designing the welding process parameters and strictly controlling the heating and cooling rates and component temperature differences, the welding stress and deformation of the printed circuit board components are reduced, ensuring the stability and reliability of the welding quality between boards. 4. Through the synergistic effect of the above design and welding methods, the traditional high-cost, high-risk, and long-cycle lamination and bonding process has been successfully replaced by a low-cost, high-efficiency, and high-reliability reflow soldering process. This significantly reduces the interconnection cost in the component assembly stage from hundreds to thousands of yuan to about tens of yuan, greatly shortens the production cycle, and realizes low-cost, high-quality manufacturing of multilayer antenna printed circuit board components.

[0022] The invention will become clearer from the following description, taken in conjunction with the accompanying drawings, which are used to explain embodiments of the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a side view of the printed circuit board assembly of the present invention; Figure 2 This is an exploded view of the printed circuit board assembly of the present invention; Figure 3 This is a top view of the soldering surface of the lower printed circuit board of the present invention; Figure 4 This is a schematic diagram illustrating the fit between the welding base plate and the printed circuit board assembly of the present invention; Figure 5This is a schematic diagram of the printed circuit board assembly of the present invention being fitted into the anti-deformation welding fixture.

[0025] Wherein: 1-Welding base plate; 11-Positioning pin; 12-Screw hole; 2-Welding pressure plate; 21-Allowing pin hole; 22-Locking screw; 3-Upper printed circuit board; 31-Ventilation hole; 32-Rectangular window; 4-Lower printed circuit board; 41-Fish scale structure; 5-Positioning pin hole. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; of course, they can also refer to a mechanical connection or an electrical connection; furthermore, they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0029] Example Specific embodiments of the present invention are as follows: Figure 1-5 The diagram illustrates a structure comprising two parts: a printed circuit board assembly and an anti-deformation welding fixture. The printed circuit board assembly consists only of two adjacent upper printed circuit boards 3 and 4. The upper printed circuit board 3 has a radial structure, while the lower printed circuit board 4 has a power-feeding structure. The upper printed circuit board 3 has vent holes 31 and rectangular openings 32, while the welding surface of the lower printed circuit board 4 has a fish-scale structure 41. Positioning pin holes 5 are correspondingly provided on both the upper and lower printed circuit boards 3 and 4. The anti-deformation welding fixture includes a welding base plate 1 and a welding pressure plate 2. The welding base plate 1 has positioning pins 11 corresponding to the positioning pin holes 5, and the welding pressure plate 2 has clearance pin holes 21 corresponding to the positioning pins 11. Screw holes 12 are also provided on the edge of the welding base plate 1, and locking screws 22 that thread into the screw holes 12 are also provided on the welding pressure plate 2.

[0030] A design method for a multilayer antenna printed circuit board assembly specifically includes the following steps: S1. Selection of printed circuit board substrate.

[0031] Select a substrate that meets the following performance requirements as the printed circuit board substrate: Relative permittivity ≤3, dielectric loss factor ≤0.0014; coefficient of thermal expansion in the X and Y directions ≤16ppm / ℃, coefficient of thermal expansion in the Z direction ≤25ppm / ℃; glass transition temperature Tg ≥170℃.

[0032] By selecting a substrate that meets the above requirements, the high-frequency signal transmission performance of the antenna can be guaranteed at the material level, and the risk of interlayer stress and warping caused by thermal expansion differences during the high-temperature welding process can be reduced.

[0033] As a preferred embodiment, this embodiment specifically selects TSM-DS3 substrate, which has a relative permittivity of 3.0, a dielectric loss factor of 0.0011, and thermal expansion coefficients in the X, Y, and Z directions of 10ppm / ℃, 16ppm / ℃, and 23ppm / ℃, respectively. The glass transition temperature Tg is greater than 170℃, which fully meets the above-mentioned index range and can better ensure the stability of the pad size and position during the soldering process.

[0034] S2, Printed circuit board assembly anti-deformation design.

[0035] The symmetrical arrangement of the printed circuit board (PCB) layer structure and layer materials ensures a uniform distribution of circuit patterns on the PCB assembly; the internal circuitry of the PCB also maintains a symmetrical and uniform distribution. This symmetrical design effectively reduces warping of the PCB caused by uneven thermal stress during processing and soldering.

[0036] Simultaneously, the length, width, and thickness of the printed circuit board are coordinated and matched: the aspect ratio of the printed circuit board is ≤2:1, and the thickness of the printed circuit board is ≥1mm. In this embodiment, the planar dimensions of the upper printed circuit board 3 and the lower printed circuit board 4 are both designed to be 70.3mm×70.3mm, with an aspect ratio of 1:1; the thickness of each board is determined according to design requirements, and the final total thickness of the assembly is approximately 3.9mm, which is much greater than 1mm. The good dimensional matching helps to suppress welding deformation.

[0037] In addition, this step also includes using anti-deformation welding fixtures to control warping deformation during the welding process. For example... Figure 4 and Figure 5 As shown, the anti-deformation welding fixture includes a welding base plate 1 and a welding pressure plate 2. Four positioning pin holes 5 are evenly distributed around the perimeter of the printed circuit board assembly, which can be installed and locked in conjunction with the fixture, thereby applying uniform constraint to the printed circuit board assembly throughout the welding process to control deformation.

[0038] S3, the exhaust vent design of the upper printed circuit board 3.

[0039] An even number of venting holes 31 are provided on the non-soldering areas of the upper printed circuit board 3 that do not affect the radiation effect. These venting holes are symmetrically arranged non-metallized holes. In this embodiment, several venting holes 31 with a diameter of 0.3 mm are designed on the upper printed circuit board 3. Non-metallized holes can better ensure the accuracy of hole diameter and position. At the same time, the symmetrically designed venting holes 31 can provide a uniform vertical release path for the volatile gases of solder paste during the soldering process, so that the internal stress caused by gas emission can be released evenly and local pressure accumulation can be avoided.

[0040] S4, the window design of the upper printed circuit board 3.

[0041] The upper printed circuit board 3 is laminated from two printed circuit board substrates. The shape of the substrate remains unchanged on the radiating surface, while a rectangular window 32 is formed on the soldering surface. The soldering surface of the upper printed circuit board 3 is the ground plane, and the rectangular window 32 has dimensions of 13.5mm × 13.5mm. This window design reduces the metal coverage area on the soldering surface and, in conjunction with the venting hole 31, further enhances the ability of inter-board gas to escape. Simultaneously, reasonable simulation design ensures that the window will not adversely affect the antenna radiation effect.

[0042] S5, pad design of the lower printed circuit board 4.

[0043] Combination Figure 3 On the ground plane of the lower printed circuit board 4, uniform etching is performed with a width of 0.1mm-0.15mm, retaining uniform square pads with a side length of 0.35mm-0.4mm. The depth of the etched trench is 0.035mm, thus forming a fish-scale structure 41 on the soldering surface. Ink solder resist treatment is applied to non-soldering areas to prevent solder from flowing and causing short circuits.

[0044] The air-guiding principle and technical effects of the fish-scale structure 41 are detailed below: The microgrooves formed by etching pre-form a network of channels with ultra-high gas conductivity at the bottom interface of the solder spread. After solder paste printing, the solder paste powder covers the pads with a fish-scale structure. Since the cross-sectional size of the trench is much larger than the gaps between the solder paste powder particles, the trench becomes a low-resistance gas channel. A quantitative analysis of the gas conductivity is performed: assuming the trench cross-section is approximately a rectangle with width ω and depth h, the laminar flow of gas within the trench can be analogized to Poisson's flow, with a volumetric flow rate per unit width of: The permeability K of the surrounding solder powder layer can be estimated using the Kozeny-Carman formula, corresponding to a very small gas flow rate. When the two are connected in parallel, most of the volatile gas will preferentially flow laterally through the micro-groove and be discharged directly from the edge of the solder pad, without needing to escape upwards through the thick layer of solder powder. Taking the trench parameters used in this embodiment as an example, with a trench width ω = 0.15 mm and a depth h = 0.035 mm, assuming the flux volatile gas is approximately air, under a micro-pressure drive of 100 Pa, for a 1 mm long trench, at soldering temperatures of 160℃, 200℃, and 230℃, the amount of gas that can be discharged per second is approximately 2.22 mm. 3 2.08mm 3 2.00mm 3 Even when the groove width is reduced to the lower limit of 0.1mm, although its cross-sectional area decreases, it still constitutes a low-resistance, high-ventilation channel relative to the penetration capacity of the solder powder layer, and can still meet the requirement of rapid exhaust of volatile gases during the soldering process. It is evident that during the rise of the solder paste temperature, the fish-scale grooves consistently possess excellent venting capacity, significantly reducing large-area voids after soldering and substantially improving the solder joint strength and grounding effect between printed circuit boards.

[0045] To support the numerical ranges in the claims, it should be understood that the etching width can be adjusted within the range of 0.1mm-0.15mm depending on the specific board size and solder paste characteristics, for example, 0.10mm, 0.12mm, or 0.15mm respectively. The corresponding side length of the retained square pads will be within the range of 0.35mm-0.40mm, such as 0.35mm, 0.38mm, or 0.40mm. All of these effectively form the fish-scale-like air-guiding structure, achieving the effect of reducing solder voids. In this embodiment, the preferred etching width is 0.12mm, and the retained pad side length is 0.38mm.

[0046] S6. Positioning design between the upper printed circuit board 3 and the lower printed circuit board 4.

[0047] Positioning pin holes 5 are provided at corresponding positions on the upper printed circuit board 3 and the lower printed circuit board 4. Through the cooperation of the positioning pin holes 5 and the positioning pins 11 on the welding base plate 1, rapid alignment and installation of the upper printed circuit board 3 and the lower printed circuit board 4 are achieved. The positioning pin holes 5 are non-metallic holes, and the design datum of the positioning pin holes 5 on the upper printed circuit board 3 and the lower printed circuit board 4 is unified. Non-metallic holes can better ensure the accuracy of hole diameter and position, and the unified datum avoids the accumulation of positioning errors. In this embodiment, the diameter of the positioning pin hole 5 is 2mm, and the hole diameter tolerance is +0.02mm to +0.05mm.

[0048] S7. Welding process parameter design.

[0049] Due to differences in the materials and dimensions of printed circuit board components, their heat capacities vary. Furthermore, the anti-deformation welding fixture also possesses a certain heat capacity. Therefore, it is necessary to test and optimize the welding temperature profile using a test board to obtain reasonable process parameters. This step designs the following process requirements: Reflow soldering, preferably vacuum reflow soldering, is selected to further reduce the void ratio. The heating rate during preheating and soldering, as well as the cooling rate during cooling, are both ≤3℃ / s; at the end of preheating and soldering, the temperature difference between the maximum and minimum heat capacity points on the printed circuit board assembly is ≤5℃; the difference between the soldering setting temperature and the actual temperature of the printed circuit board assembly is ≤10℃. Strict control of the heating and cooling rates and temperature differences effectively reduces soldering thermal stress, prevents board warping and solder joint defects caused by thermal shock, thereby ensuring the reliability and consistency of inter-board soldering quality.

[0050] The soldering method for a multilayer antenna printed circuit board assembly specifically includes the following steps: Step 1: Based on the size of the pads on the lower printed circuit board 4, prefabricate the stencil for solder paste printing.

[0051] Step 2: Using a fully automatic printing machine and stencil, solder paste is printed onto the soldering surface of the lower printed circuit board 4. Solder paste inspection equipment is used to check the thickness, uniformity, integrity, and accuracy of the solder paste printing, ensuring 100% coverage of the solder pads. In this embodiment, SAC305 solder paste is used.

[0052] Step 3: Use anti-deformation welding fixtures for mounting and locking. For example... Figure 4 and Figure 5 As shown, the lower printed circuit board 4 is mounted onto the positioning pin 11 of the soldering base plate 1 through the positioning pin hole 5. Then, the upper printed circuit board 3 is also positioned and stacked on the lower printed circuit board 4 through the positioning pin hole 5. After mounting, check whether the upper printed circuit board 3 and the lower printed circuit board 4 are tightly fitted. Then, the soldering pressure plate 2 is inserted into the positioning pin 11 through the clearance pin hole 21, and the clamp is locked using the screw hole 12 on the edge of the soldering base plate 1 and the corresponding locking screw 22 on the soldering pressure plate 2, thereby preventing the printed circuit board assembly from deforming or becoming loosely connected during the soldering process.

[0053] Step 4: Place the locked anti-deformation welding fixture along with the printed circuit board assembly into the reflow oven for reflow soldering. The preferred soldering temperature is 235℃. Through the constraint of the fixture and the control of the aforementioned process parameters, the deformation and void ratio during the soldering process are effectively suppressed.

[0054] Step 5: After the printed circuit board assembly cools to room temperature, remove the anti-deformation welding fixture to complete the welding of the stacked antenna printed circuit board assembly.

[0055] Compared to existing technologies, the advantages of this embodiment are as follows: The fish-scale structure 41 on the welding surface of the lower printed circuit board 4 provides a low-resistance channel for the volatile gases of solder paste to be discharged laterally along the micro-grooves. At the same time, the venting holes 31 and rectangular openings 32 of the upper printed circuit board 3 provide a vertical gas release path. The two work together to fundamentally solve the problem of gas discharge in large-area inter-board welding, significantly reduce the welding void rate, and significantly improve the inter-board grounding effect and welding strength.

[0056] The anti-deformation design of printed circuit boards, such as symmetrical stacking, uniform layout, and matching aspect ratio and thickness, combined with the use of anti-deformation welding fixtures, effectively controls warping deformation under the high temperature of reflow soldering, ensuring uniform stress and tight fit between boards, and ensuring the consistency and reliability of welding quality.

[0057] Strict design of welding process parameters such as heating and cooling rates and temperature difference control further reduces welding thermal stress and residual deformation, ensuring the reliability of weld joints and the long-term operational stability of components.

[0058] Through the above technical solution, a low-cost, high-efficiency, and high-reliability reflow soldering process has been successfully used to completely replace the traditional high-cost, long-cycle, and high-scraping-risk multi-layer lamination and bonding process. Taking a conventional multilayer antenna assembly as an example, the traditional lamination method involves laminating the upper and lower printed circuit boards separately before performing a final bonding, which costs several hundred to several thousand yuan. The final bonding cost will also increase the total price by about 25%-30%. However, using the method of this invention, the cost of the interconnection process can be reduced to about tens of yuan, and the production cycle is also significantly shortened, significantly achieving low-cost, high-quality manufacturing of multilayer antenna printed circuit board assemblies.

[0059] The present invention has been described above in conjunction with the preferred embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations made in accordance with the essence of the present invention.

Claims

1. A design method for a multilayer antenna printed circuit board assembly, wherein, The printed circuit board assembly comprises only adjacent upper printed circuit board (3) and lower printed circuit board (4), characterized by including the following steps: S1. Selection of printed circuit board substrate: Select a substrate that meets the following requirements: relative permittivity ≤3, dielectric loss factor ≤0.0014, X / Y thermal expansion coefficient ≤16ppm / ℃, Z thermal expansion coefficient ≤25ppm / ℃, and glass transition temperature Tg ≥170℃. S2. Anti-deformation design of printed circuit board assembly: The printed circuit board stack-up structure and stack-up materials are symmetrically arranged, the circuit patterns on the printed circuit board assembly are evenly distributed, the length-to-width ratio of the printed circuit board is ≤2:1, and the thickness of the printed circuit board is ≥1mm; and anti-deformation welding fixtures are used to control welding warping deformation. The anti-deformation welding fixtures include a welding base plate (1) and a welding pressure plate (2). S3. Venting hole design of upper printed circuit board (3): An even number of venting holes (31) are provided on the non-soldering parts of the upper printed circuit board (3) that do not affect the radiation effect. S4. Window design of upper printed circuit board (3): The upper printed circuit board (3) is made of two printed circuit board substrates laminated together. The shape of the printed circuit board substrate remains unchanged on the radiating surface, and a rectangular window (32) is opened on the printed circuit board substrate on the welding surface. S5. Pad design of the lower printed circuit board (4): The soldering surface of the lower printed circuit board (4) is uniformly etched with a width of 0.1mm-0.15mm, and a uniform square pad with a side length of 0.35mm-0.4mm is retained, thereby forming a fish scale structure (41) with a trench depth of 0.035mm. S6. Positioning design between upper printed circuit board (3) and lower printed circuit board (4): Positioning pin holes (5) are set at corresponding positions on upper printed circuit board (3) and lower printed circuit board (4). Through the cooperation of positioning pin holes (5) and positioning pins (11) on welding base plate (1), the upper printed circuit board (3) and lower printed circuit board (4) can be quickly aligned and installed. S7. Welding process parameter design: Reflow soldering is selected; the heating rate during preheating and welding and the cooling rate during cooling are both ≤3℃ / s; at the end of preheating and welding, the temperature difference between the maximum heat capacity and the minimum heat capacity on the printed circuit board assembly is ≤5℃; the difference between the welding setting temperature and the actual temperature of the printed circuit board assembly is ≤10℃.

2. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S2, the internal circuitry of the printed circuit board should be kept symmetrical and evenly distributed.

3. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S3, the exhaust vent (31) consists of an even number of symmetrically arranged non-metallized vents.

4. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S4, the welding surface of the upper printed circuit board (3) is the ground layer, and the window size of the rectangular window (32) is 13.5mm×13.5mm.

5. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S5, the fish-scale structure (41) is set on the ground layer soldering surface of the lower printed circuit board (4), and ink solder resist treatment is performed on the non-soldering parts of the lower printed circuit board (4).

6. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S6, the positioning pin hole (5) is a non-metallized hole, and the design benchmarks of the positioning pin holes (5) of the upper printed circuit board (3) and the lower printed circuit board (4) are the same.

7. The design method for the stacked antenna printed circuit board assembly according to claim 1, characterized in that, In step S1, the substrate selected is TSM-DS3 substrate, which has a relative permittivity of 3.0, a dielectric loss factor of 0.0011, and thermal expansion coefficients in the X, Y, and Z directions of 10ppm / ℃, 16ppm / ℃, and 23ppm / ℃, respectively.

8. A method for soldering a multilayer antenna printed circuit board assembly, wherein, The printed circuit board assembly includes an upper printed circuit board (3) and a lower printed circuit board (4). The upper printed circuit board (3) is provided with a vent hole (31) and a rectangular window (32). The soldering surface of the lower printed circuit board (4) is provided with a fish-scale structure (41). The upper printed circuit board (3) and the lower printed circuit board (4) are respectively provided with positioning pin holes (5). The method is characterized by the following steps: Step 1: Based on the size of the pads on the lower printed circuit board (4), prepare a stencil for solder paste printing in advance; Step 2: Use a fully automatic printing machine with a screen to print solder paste on the soldering surface of the lower printed circuit board (4), and use solder paste testing equipment to check the thickness, uniformity, integrity and accuracy of the solder paste printing to ensure that the solder paste covers 100% of the solder pads. Step 3: Using the positioning pins (11) on the anti-deformation welding fixture, and in conjunction with the positioning pin holes (5) on the upper printed circuit board (3) and the lower printed circuit board (4), position and mount the upper printed circuit board (3) and the lower printed circuit board (4). After mounting, check the tightness of the bonding and lock the upper printed circuit board (3) and the lower printed circuit board (4) using the anti-deformation welding fixture. Step 4: Reflow soldering the locked anti-deformation welding fixture together with the printed circuit board assembly; Step 5: After the printed circuit board assembly has cooled to room temperature, remove the anti-deformation welding fixture.

9. The welding method for the multilayer antenna printed circuit board assembly according to claim 8, characterized in that, The anti-deformation welding fixture includes a welding base plate (1) and a welding pressure plate (2). The welding base plate (1) is provided with a positioning pin (11) corresponding to the positioning pin hole (5), and the welding pressure plate (2) is provided with a clearance pin hole (21) corresponding to the positioning pin (11). The edge of the welding base plate (1) is also provided with a screw hole (12), and the welding pressure plate (2) is also provided with a locking screw (22) that is threadedly engaged with the screw hole (12).

10. The welding method for the multilayer antenna printed circuit board assembly according to claim 8, characterized in that, The welding temperature in step 4 is set to 235℃.

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