Multi-layer circuit board structure based on AMB technology and preparation technology

Abstract

The invention discloses a multi-layer circuit board structure based on an AMB technology and a preparation technology, and relates to the field of circuit board preparation, and the preparation technology comprises the following steps: providing a plurality of substrates with coating surfaces, and scanning the coating surfaces through a second laser beam to preheat the substrates, spraying welding flux on the coating surface through a spray head with a first ultrasonic generation module to form a welding flux layer; the surface of the solder layer is scanned through a third laser beam, so that the surface of the solder layer is softened, the solder layer is automatically spread and leveled, and a semi-solid solder layer is formed after cooling; and a plurality of substrates are stacked and fixed through a positioning clamp, then each solder layer is scanned through a fourth laser beam, the solder layers are vibrated by a second ultrasonic generation module, and after the solder layers are cooled and solidified to form welding spots, the multilayer circuit board structure is obtained. Through combination of laser and ultrasonic waves, the thickness of the solder layer is uniform, and the surface is smooth; bubbles and impurities in the solder layer are eliminated through laser and ultrasonic combined melting, and the problems of uneven coating and accumulation and bubbling are avoided.

Description

Technical Field

[0001] The present invention relates to the field of circuit board preparation, and in particular to a multi-layer circuit board structure and preparation process based on an AMB process. Background Art

[0002] The AMB (Active Metal Brazing) process is a key technology for manufacturing high-performance multi-layer circuit boards. By using a brazing material containing active elements such as titanium in a vacuum or protective atmosphere, copper foil and ceramic substrates are bonded at high temperature to form a composite substrate with conductive, insulating and heat dissipating functions. This process is suitable for multi-layer stacked structures. After each layer of ceramic substrate is treated with AMB, precise alignment and secondary brazing are used to achieve interlayer interconnection to form a three-dimensional circuit layout. Its advantages lie in high interface bonding strength, excellent thermal conductivity, and matching thermal expansion coefficients.

[0003] In the traditional multi-layer circuit board manufacturing process, the solder coating process faces the problem of solder accumulation and difficulty in precise control of thickness. Traditional coating methods such as brushing and template printing cannot ensure that the solder forms an extremely thin and uniform bridge between the pad and the copper layer, which often leads to welding defects such as cold solder joints, micro-voids or solder accumulation and blistering. These problems not only affect the quality of the solder joints, but may also cause functional failure of the circuit board and affect the reliability and performance of the product. Specifically, the thickness difference that is difficult to control during the solder coating process can lead to too much or too little solder, resulting in local uneven thermal resistance, signal distortion or insufficient mechanical strength.

[0004] Therefore, a multi-layer circuit board structure and preparation process based on the AMB process is proposed to solve the above-mentioned problems of solder accumulation and difficulty in precise thickness control. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-layer circuit board structure and preparation process based on the AMB process to solve the above-mentioned problems of solder accumulation and difficulty in precise thickness control.

[0006] To achieve this object, the present invention adopts the following technical solutions: A multi-layer circuit board structure and preparation process based on the AMB process, the preparation process comprising the following steps: Step S1, providing a plurality of substrates with coated surfaces, scanning the coated surfaces with a second laser beam to preheat the substrates, and spraying solder onto the coated surfaces through a nozzle equipped with a first ultrasonic generating module to form a solder layer; Step S2: Scanning the surface of the solder layer with a third laser beam to soften the surface of the solder layer, causing it to spread and level itself, and forming a semi-solid solder layer after cooling; Step S3: Stack and fix several substrates using a positioning fixture, then scan each solder layer with a fourth laser beam, and vibrate the solder layer with a second ultrasonic generating module. After the solder layer cools and solidifies to form solder joints, a multi-layer circuit board structure is obtained.

[0007] The substrate is obtained according to the following steps: Step S11: ultrasonically clean the FR4 substrate using an ultrasonic cleaning machine and dry it; Step S12: activating the surface of the FR4 substrate by using atmospheric cold plasma; Step S13: Use the first laser beam to scan the portion of the FR4 substrate surface corresponding to the solder pad to increase the surface temperature, and then use an atomizing nozzle to spray atomized particles of the mercaptosilane solution on the portion to form a substrate with a coated surface.

[0008] In step S11, the frequency of the ultrasonic cleaning machine is 40-60 kHz, the power is 100-120 W, and the ultrasonic cleaning time is 3-5 minutes; In step S12, the atmospheric cold plasma is argon plasma, the energy density of the atmospheric cold plasma is 50-100W, the temperature is <60°C, and the activation treatment time is 30-90s; In the step S13, the power of the first laser beam is 0.5-3W, the surface temperature is 40-90°C, and the particle size of the atomized particles is 1-10 μm.

[0009] The step S1 specifically includes the following steps: Step S14: Scanning the coated surface of the substrate with a second laser beam to preheat the copper surface temperature at the coated surface to a preheating temperature; Step S15: The spraying system sprays the solder onto the coating surface through the nozzle, and atomizes the solder through the first ultrasonic generating module, and finally the solder forms a semi-liquid solder layer on the coating surface.

[0010] In step S14, the power of the second laser beam is 2-5W, and the preheating temperature is 100-150°C; In step S15, the solder is Sn-Ag-Cu solder, the thickness of the solder layer is 30-50 μm, the frequency of the first ultrasonic generating module is 20-40 kHz, and the power is 2-5 W.

[0011] In step S2, the surface of the solder layer is scanned by a third laser beam. After the surface of the solder layer is heated, the solder layer is transformed from a semi-liquid state to a semi-paste state and is completely adhered to the coating surface. The surface of the solder layer is transformed from an uneven surface to a microscopically flat, continuous surface without obvious steps. After the scanning is completed, the solder layer is transformed from a semi-paste state to a semi-solid state.

[0012] In step S2, the power of the third laser beam is 2-5 W, the scanning time is 10-100 ms, and the heating temperature of the solder layer is 100-160°C.

[0013] The step S3 specifically includes the following steps: Step S31, stacking a plurality of substrates with solder layers coated on their coating surfaces, and fixing the stacked substrates with a positioning fixture; Step S32: Scanning the solder layer with a fourth laser beam to melt the solder layer; Step S33: while the fourth laser beam is scanning, the second ultrasonic wave generating module is operated synchronously to vibrate the melted solder layer; Step S34: After the solder layer is completely melted, the solder layer is cooled to form solder joints, and finally a multi-layer circuit board structure is obtained.

[0014] In step S32, the power of the fourth laser beam is 30-50W, and the melting temperature is 250-270°C; In step S33, the frequency of the first ultrasonic generating module is 20-40kHz, the power is 10-50W, and the first ultrasonic generating module is set on the positioning fixture; In the step S34, the cooling rate is 5-10°C / min.

[0015] A multi-layer circuit board structure based on an AMB process is manufactured using the multi-layer circuit board structure manufacturing process based on an AMB process as described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a multi-layer circuit board structure and preparation process based on the AMB process. The structure can achieve precise coating of the solder layer by combining laser and ultrasound. The precise laser heating and ultrasonic assisted micro-vibration ensure uniform distribution of the solder, avoiding the problems of uneven coating and accumulation and blistering in traditional processes. Secondly, the method can achieve automatic leveling of the solder layer by laser irradiation after solder coating, making the solder layer thickness more uniform and the surface smoother, greatly improving the quality and reliability of the solder joints. In addition, the combined laser and ultrasonic melting process further optimizes the fluidity of the solder, eliminates bubbles and impurities in the solder, ensures the high density and mechanical strength of the solder joints, and improves the overall performance of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0019] Figure 1 It is a flow chart of the preparation process of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0022] Example 1: See also Figure 1 In this embodiment, a multi-layer circuit board structure preparation process based on the AMB process includes the following steps: Step S1, providing a plurality of substrates with coated surfaces, scanning the coated surfaces with a second laser beam to preheat the substrates, and spraying solder onto the coated surfaces through a nozzle equipped with a first ultrasonic generating module to form a solder layer; The substrate is obtained according to the following steps: Step S11: ultrasonically clean the FR4 (Flame Retardant Level 4) substrate using an ultrasonic cleaning machine and then dry it; In step S11, the frequency of the ultrasonic cleaning machine is 40-60kHz, the power is 100-120W, and the ultrasonic cleaning time is 3-5min; preferably, the frequency of the ultrasonic cleaning machine is 40kHz, the power is 120W, and the ultrasonic cleaning time is 4min; It should be noted that ultrasonic cleaning of the FR4 substrate can remove coarse impurities, oil stains and dust on its surface, preparing for subsequent processing; it is known that the FR4 substrate is a glass fiber reinforced epoxy resin laminate, which includes electronic grade alkali-free glass fiber cloth, flame-retardant epoxy resin and electrolytic copper foil.

[0023] Step S12: activating the surface of the FR4 substrate by using atmospheric cold plasma; In step S12, the atmospheric cold plasma is argon plasma, the energy density of the atmospheric cold plasma is 50-100W, the temperature is <60°C, and the activation treatment time is 30-90s; preferably, the energy density of the atmospheric cold plasma is 80W, the temperature is <60°C, and the activation treatment time is 60s; It should be noted that the atmospheric cold plasma generated by the atmospheric cold plasma processor bombards the surface of the FR4 substrate. When the bombardment occurs, the high-energy ions and active oxygen free radicals in the atmospheric cold plasma can remove the organic impurities and oil film remaining on the copper surface of the FR4 substrate, finely reduce the copper oxide layer, and generate polar functional groups such as hydroxyl and carbonyl on the copper surface. The copper surface after bombardment is extremely lyophilic, and the free energy of the copper surface is improved, so as to facilitate the subsequent spreading of solder.

[0024] It should also be noted that atmospheric cold plasma treatment of the FR4 substrate surface is liquid-free, residue-free, environmentally friendly and precise, which can improve the surface energy of the copper surface on the FR4 substrate, greatly promote the uniform spreading of solder, and prevent solder voids and accumulation. In addition, atmospheric cold plasma can modify the surface of the FR4 substrate without heating. The treatment process is simple, the operation is safe, and it will not cause thermal damage to the FR4 substrate.

[0025] Step S13: Use the first laser beam to scan the portion of the FR4 substrate surface corresponding to the solder pad to increase the surface temperature, and then use an atomizing nozzle to spray atomized particles of the mercaptosilane solution on the portion to form a substrate with a coated surface.

[0026] In step S13, the power of the first laser beam is 0.5-3W, the surface temperature is 40-90°C, and the particle size of the atomized particles is 1-10μm; the power of the first laser beam is 2W, the surface temperature is 75°C, and the particle size of the atomized particles is 6μm.

[0027] It should be noted that after the surface temperature of the corresponding part of the FR4 substrate surface is increased by scanning with the first laser beam, the atomized particles formed by spraying the mercaptosilane solution with the atomizing nozzle will be quickly and directionally adsorbed at the part and form a chemical connection, thereby forming a thin film at the part, and then forming a substrate with a coated surface.

[0028] It should also be noted that the thin film formed allows the subsequent solder to adhere to the coating surface by itself during coating, forming a precise coating. In this way, there is no need for expensive photolithography masks or physical baffles, which makes it easy to adapt to different parts and has strong adaptability.

[0029] It can be understood that after the mercaptosilane solution forms atomized particles and is sprayed on the surface of the FR4 substrate, the -SH mercapto groups in the mercaptosilane solution are strongly chemically anchored to the copper surface of the FR4 substrate, forming an orderly arranged thin film. Its exposed end groups can easily establish hydrogen bonds or van der Waals forces with subsequent solder or flux molecules, so that the solder can be accurately adsorbed on the coating surface during the subsequent solder spraying process.

[0030] Step S1 specifically includes the following steps: Step S14: Scanning the coated surface of the substrate with a second laser beam to preheat the copper surface temperature at the coated surface to a preheating temperature; In step S14, the power of the second laser beam is 2-5W, and the preheating temperature is 100-150°C; preferably, the power of the second laser beam is 4W, and the preheating temperature is 130°C; It should be noted that heating the coating surface with the first laser beam can not only provide a good temperature control environment for the subsequent coating process, but also effectively reduce the heat diffusion to the surrounding area, thereby avoiding thermal damage to other areas that do not need to be coated. Step S15: The spraying system sprays the solder onto the coating surface through the nozzle, and atomizes the solder through the first ultrasonic generating module, and finally the solder forms a semi-liquid solder layer on the coating surface.

[0031] In step S15, the solder is Sn-Ag-Cu solder, the thickness of the solder layer is 30-50 μm, the frequency of the first ultrasonic generating module is 20-40 kHz, and the power is 2-5 W; preferably, the thickness of the solder layer is 40 μm, the frequency of the first ultrasonic generating module is 30 kHz, and the power is 2 W.

[0032] It should be noted that preheating the coated surface through the second laser beam can increase the temperature of the copper surface at the coated surface, thereby improving the wettability of the solder subsequently sprayed on the coated surface, making the solder evenly coated and allowing the solder to adhere better. At the same time, the ultrasonic waves in the spraying can also ensure that the solder is evenly distributed, avoiding accumulation and achieving the effect of precision coating.

[0033] It should also be noted that under the action of the preheated copper surface, the sprayed solder begins to soften but is not completely melted. The surface of the metal particles in the solder is gradually activated, which enhances the affinity between the solder and the copper surface. At the same time, the metal particles in the solder are heated and form a preliminary solder layer on the copper surface, but have not yet completely melted into a liquid state. At this time, the physical bond between the solder and the substrate has been formed, ready to enter the subsequent melting step.

[0034] It should be emphasized that the ultrasound during solder spraying is to help the atomization and uniform spraying of the solder. Usually, lower-power ultrasound is required to finely control the distribution of solder particles. Therefore, the power of the first ultrasonic generating module is lower and the frequency is higher. In addition, the first ultrasonic generating module includes a first ultrasonic generator and a first ultrasonic transducer.

[0035] Step S2: Scanning the surface of the solder layer with a third laser beam to soften the surface of the solder layer, causing it to spread and level itself, and forming a semi-solid solder layer after cooling; In step S2, the surface of the solder layer is scanned by a third laser beam. After the surface of the solder layer is heated, the solder layer is transformed from a semi-liquid state to a semi-paste state and is completely adhered to the coating surface. The surface of the solder layer is transformed from an uneven surface to a microscopically flat, continuous state without obvious steps. After the scanning is completed, the solder layer is transformed from a semi-paste state to a semi-solid state.

[0036] In step S2, the power of the third laser beam is 2-5W, the scanning time is 10-100ms, and the heating temperature of the solder layer is 100-160°C; preferably, the power of the third laser beam is 3W, the scanning time is 60ms, and the heating temperature of the solder layer is 140°C.

[0037] It should be noted that after the surface of the solder layer is scanned by the third laser beam, its surface is subjected to short-term local laser heating to soften its surface, thereby eliminating the microscopic unevenness caused by spraying and promoting further interface bonding between the solder particles and the copper surface at the coating surface, providing a basis for the subsequent melting of the solder layer. At the same time, the softened solder layer will automatically spread along the surface tension, causing the thin areas to slightly increase and the thick areas to automatically dilute, thereby achieving micron-leveling and removing the air and micro impurities entrained in the solder layer due to spraying.

[0038] It can be known that the solder layer after laser irradiation is heated to 140°C, which is lower than the melting point of Sn-Ag-Cu solder of 217-227°C. At this time, the Sn-Ag-Cu solder undergoes solid-liquid interface softening, the flux between the particles becomes fluid, and the particles are relatively loose. The stress can be released under the action of surface tension and local flow, achieving automatic leveling.

[0039] It should also be noted that the thickness of each part of the solder layer after the surface is automatically leveled is consistent, so that the volume of the subsequent molten solder is uniform, to ensure that the height of the subsequent solder joints is consistent, to avoid the occurrence of processing defects such as bridging, cold solder joints, leaking solder joints or stress concentration after welding, and after the air and micro-impurities in the solder layer are removed, the gas is encapsulated in the solder joints during subsequent melting to form voids or pores, so as to obtain high-density solder joints and improve the mechanical strength and thermal conductivity of the solder joints. At the same time, the softened surface of the solder layer after being scanned by the second laser beam is tightly attached to the copper surface and covers the surface microstructure. On the one hand, this improves the physical adhesion, and on the other hand, it is easier to achieve chemical metallurgical reactions during the subsequent heating and melting, quickly establish an intermetallic compound layer, and improve the electrical and thermomechanical properties of the solder joints.

[0040] It should be emphasized that the solder layer with uniform thickness formed on the coated surface can improve the thermal conductivity and current carrying capacity of the subsequently formed solder joints, and achieve sufficient welding quality and reliability through thinner and less solder, reduce the waste of heavy metal solder, reduce the impact on the environment, and avoid the cost waste and increased difficulty of rework caused by the occurrence of cold solder joints or bubbles in the formed solder joints.

[0041] Step S3: Stack and fix several substrates using a positioning fixture, then scan each solder layer with a fourth laser beam, and vibrate the solder layer with a second ultrasonic generating module. After the solder layer cools and solidifies to form solder joints, a multi-layer circuit board structure is obtained.

[0042] Step S3 specifically includes the following steps: Step S31, stacking a plurality of substrates with solder layers coated on their coating surfaces, and fixing the stacked substrates with a positioning fixture; It can be seen that fixing the stacked substrates with a positioning fixture can improve the accuracy of welding and make the final product of welding better in quality, so as to avoid waste or rework due to low quality. In addition, the positioning fixture ensures that the gap between the substrates is uniform and keeps the position of the solder layer unchanged during welding to prevent misalignment or excessive gap between layers.

[0043] Step S32: Scanning the solder layer with a fourth laser beam to melt the solder layer; In step S32, the power of the fourth laser beam is 30-50W, and the melting temperature is 250-270°C; preferably, the power of the fourth laser beam is 40W, and the melting temperature is 260°C; Step S33: while the fourth laser beam is scanning, the second ultrasonic wave generating module is operated synchronously to vibrate the melted solder layer; In step S33, the frequency of the first ultrasonic generating module is 20-40kHz, the power is 10-50W, and the first ultrasonic generating module is set on the positioning fixture; preferably, the frequency of the first ultrasonic generating module is 30kHz, and the power is 35W; It should be noted that the high energy density of the fourth laser beam scanning causes the solder layer to quickly heat up to above the melting point. Ultrasonic vibration plays an auxiliary role in this process, which can promote the fluidity of the solder layer, remove bubbles in the solder layer, and improve the wettability between the solder layer and the substrate, ultimately forming a strong metallurgical bond. The role of the ultrasound is to make the flow of the molten solder more uniform through the microscopic vibration effect, and further remove defects in the solder joints.

[0044] It can be known that while the fourth laser beam is heating, the second ultrasonic generating module starts working, emitting high-frequency vibrations, making the molten solder layer flow more evenly and promoting the metallurgical bonding between the solder layer and the surface of the substrate. Under the synergistic action of the ultrasonic wave and the fourth laser beam, the solder layer completely fills the gap between the pads at the coating surface to form a dense intermetallic compound to ensure the strength and conductivity of the solder joint.

[0045] It is worth noting that after the solder layer begins to melt, it gradually softens from a semi-solid state and eventually melts completely into a liquid state. Through the combined action of the fourth laser beam and ultrasound, the molten solder layer flows and fills the space between adjacent substrates, forming a strong metallurgical bond. At the same time, during the subsequent cooling process, the solder layer transforms from liquid to solid, forming a solder joint with high mechanical strength and excellent conductivity.

[0046] It should also be noted that when the fourth laser beam scans the solder layer, the stacked substrates need to be placed in a vacuum chamber and evacuated to 10 -2 -10 -3 Pa or fill with nitrogen to reduce oxidation and provide a protective atmosphere to improve welding quality.

[0047] It can be understood that the second ultrasonic generating module includes a second ultrasonic generator and a second ultrasonic transducer. The ultrasonic waves emitted by the second ultrasonic generating module focus on promoting the fluidity of molten liquid solder, removing bubbles and improving the wettability of the solder. At this time, the power of the ultrasonic wave needs to be higher, usually 35W, and the frequency is between 30kHz, so as to be effectively transmitted to the solder layer and enhance the fluidity of the molten liquid solder.

[0048] Step S34: After the solder layer is completely melted, the solder layer is cooled to form solder joints, and finally a multi-layer circuit board structure is obtained.

[0049] In step S34, the cooling rate is 5-10°C / min, and the cooling rate is 8°C / min.

[0050] It should be noted that by controlling the cooling rate, it is possible to ensure that the formed solder joints are not affected by stress, allow the solder to crystallize evenly, and avoid cracks or thermal stress caused by rapid cooling.

[0051] It can be known that after the solder cools, all solder joints are completely solidified, and the welded multi-layer circuit board structure is formed. At this time, the electrical connections between the substrates have been firmly connected through metallurgical bonding, and the entire circuit board has high-strength mechanical connections and good thermoelectric properties.

[0052] Example 2: In this embodiment, a multi-layer circuit board structure based on an AMB process is manufactured using the multi-layer circuit board structure manufacturing process based on an AMB process as in Example 1.

[0053] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-layer circuit board structure preparation process based on AMB process, characterized in that: The preparation process comprises the following steps: Step S1, providing a plurality of substrates with coated surfaces, scanning the coated surfaces with a second laser beam to preheat the substrates, and spraying solder onto the coated surfaces through a nozzle equipped with a first ultrasonic generating module to form a solder layer; Step S2: Scanning the surface of the solder layer with a third laser beam to soften the surface of the solder layer, causing it to spread and level itself, and forming a semi-solid solder layer after cooling; Step S3: Stack and fix several substrates using a positioning fixture, then scan each solder layer with a fourth laser beam, and vibrate the solder layer with a second ultrasonic generating module. After the solder layer cools and solidifies to form solder joints, a multi-layer circuit board structure is obtained.

2. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 1, characterized in that: The substrate is obtained according to the following steps: Step S11: ultrasonically clean the FR4 substrate using an ultrasonic cleaning machine and dry it; Step S12: activating the surface of the FR4 substrate by using atmospheric cold plasma; Step S13: Use the first laser beam to scan the portion of the FR4 substrate surface corresponding to the solder pad to increase the surface temperature, and then use an atomizing nozzle to spray atomized particles of the mercaptosilane solution on the portion to form a substrate with a coated surface.

3. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 2, characterized in that: In step S11, the frequency of the ultrasonic cleaning machine is 40-60 kHz, the power is 100-120 W, and the ultrasonic cleaning time is 3-5 minutes; In step S12, the atmospheric cold plasma is argon plasma, the energy density of the atmospheric cold plasma is 50-100W, the temperature is <60°C, and the activation treatment time is 30-90s; In the step S13, the power of the first laser beam is 0.5-3W, the surface temperature is 40-90°C, and the particle size of the atomized particles is 1-10 μm.

4. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 1, characterized in that: The step S1 specifically includes the following steps: Step S14: Scanning the coated surface of the substrate with a second laser beam to preheat the copper surface temperature at the coated surface to a preheating temperature; Step S15: The spraying system sprays the solder onto the coating surface through the nozzle, and atomizes the solder through the first ultrasonic generating module, and finally the solder forms a semi-liquid solder layer on the coating surface.

5. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 4, characterized in that: In step S14, the power of the second laser beam is 2-5W, and the preheating temperature is 100-150°C; In step S15, the solder is Sn-Ag-Cu solder, the thickness of the solder layer is 30-50 μm, the frequency of the first ultrasonic generating module is 20-40 kHz, and the power is 2-5 W.

6. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 1, characterized in that: In step S2, the surface of the solder layer is scanned by a third laser beam. After the surface of the solder layer is heated, the solder layer is transformed from a semi-liquid state to a semi-paste state and is completely adhered to the coating surface. The surface of the solder layer is transformed from an uneven surface to a microscopically flat, continuous surface without obvious steps. After the scanning is completed, the solder layer is transformed from a semi-paste state to a semi-solid state.

7. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 6, characterized in that: In step S2, the power of the third laser beam is 2-5 W, the scanning time is 10-100 ms, and the heating temperature of the solder layer is 100-160°C.

8. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 1, characterized in that: The step S3 specifically includes the following steps: Step S31, stacking a plurality of substrates with solder layers coated on their coating surfaces, and fixing the stacked substrates with a positioning fixture; Step S32: Scanning the solder layer with a fourth laser beam to melt the solder layer; Step S33: while the fourth laser beam is scanning, the second ultrasonic wave generating module is operated synchronously to vibrate the melted solder layer; Step S34: After the solder layer is completely melted, the solder layer is cooled to form solder joints, and finally a multi-layer circuit board structure is obtained.

9. The process for preparing a multi-layer circuit board structure based on the AMB process according to claim 8, characterized in that: In step S32, the power of the fourth laser beam is 30-50W, and the melting temperature is 250-270°C; In step S33, the frequency of the first ultrasonic generating module is 20-40kHz, the power is 10-50W, and the first ultrasonic generating module is set on the positioning fixture; In the step S34, the cooling rate is 5-10°C / min.

10. A multi-layer circuit board structure based on AMB process, characterized in that: The multi-layer circuit board structure is manufactured using the AMB process-based multi-layer circuit board structure manufacturing process as described in any one of claims 1 to 9.

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