Low-cavity packaging method of microelectronic component and microelectronic component

Abstract

The invention relates to the technical field of packaging, and discloses a low-cavity packaging method of a microelectronic component and the microelectronic component, and the method comprises the steps: S1, providing a packaging substrate; s2, preparing solder paste with a first activity grade; s3, uniformly coating the prepared solder paste on an interconnection bonding pad of a packaging substrate; s4, mounting an electronic component on the internal interconnection bonding pad of the packaging substrate; s5, reflow soldering is carried out, welding of the electronic component and the packaging substrate is completed, meanwhile, the solder paste at the external interconnection bonding pad is made to be formed into a plane grid array welding spot structure, reflow soldering is carried out according to a preset temperature curve, the peak temperature of the preset temperature curve is set to range from 240 DEG C to 260 DEG C, and the duration time of a uniform temperature section of the preset temperature curve ranges from 60 seconds to 90 seconds; s6, quality monitoring is conducted through a micron focal spot system, the resolution ratio of the system is smaller than or equal to 5 microns, and the scanning frequency is 10 frames per second. The LGA welding spot void rate can be reduced, and the reliability of the microelectronic assembly is improved.

Description

Technical Field

[0001] This application relates to the field of packaging technology, and in particular to a low-void packaging method for microelectronic components and a microelectronic component. Background Technology

[0002] In fields with extremely high reliability requirements, such as embedded systems, automotive electronics, and aerospace, microelectronic components are the core of the system. LGA (Land Grid Array) packaging has become the mainstream choice due to its high pin density and good electrical performance. However, during the surface mount technology (SMT) soldering process of LGA components, the formation of voids inside the solder joints has been a long-standing and difficult-to-eradicate technical problem.

[0003] These voids primarily originate from flux volatiles and residual solvents within the solder paste that failed to completely escape during the soldering process, or from contaminants present on the solder pad surface. The presence of voids can lead to a series of serious consequences: First, voids are poor conductors of heat, severely hindering the downward conduction of heat generated by the component core to the PCB board, causing a sharp rise in local temperature and affecting component performance and lifespan; second, voids reduce the effective load-bearing capacity and conductive cross-sectional area of ​​the solder joint, lowering its mechanical strength and current carrying capacity. When subjected to temperature cycling, vibration, or impact, stress will concentrate at the edge of the void, easily inducing cracks and leading to open-circuit failure of the solder joint.

[0004] Traditional packaging processes attempt to improve voiding issues by adjusting reflow soldering temperature profiles, but with limited effectiveness, typically controlling the void rate within the range of 10%-20%, which is far from sufficient for high-reliability applications. Therefore, the industry urgently needs a packaging method that can stably control the void rate of LGA solder joints at extremely low levels to improve the long-term reliability of microelectronic components. Summary of the Invention

[0005] To address the reliability issues of microelectronic components caused by solder joint voids in the LGA packaging process, this application provides a low-void packaging method for microelectronic components and a microelectronic component.

[0006] In a first aspect, this application provides a low-void packaging method for microelectronic components, employing the following technical solution: A low-void packaging method for microelectronic components includes the following steps: S1, providing a packaging substrate, the packaging substrate including internal interconnect pads and external interconnect pads; S2, mixing a solder alloy matrix and an active flux in a proportion, controlling the mass percentage of the active flux in the solder paste to be 3% to 5%, to prepare a solder paste with a first activity level; S3, uniformly coating the prepared solder paste with the first activity level onto the internal interconnect pads and external interconnect pads of the packaging substrate to perform solder paste printing on the packaging substrate; S4, mounting electronic components onto the internal interconnect pads of the packaging substrate printed with solder paste; S5, mounting the components onto the internal interconnect pads of the packaging substrate printed with solder paste. The packaging substrate containing the electronic components is reflow soldered, which melts the solder paste at the internal interconnect pads to complete the soldering of the electronic components to the packaging substrate. At the same time, the solder paste at the external interconnect pads is formed into a planar grid array solder joint structure. The planar grid array solder joint structure is used to solder the microelectronic components to an external circuit board. The reflow soldering is performed according to a preset temperature profile. The peak temperature of the preset temperature profile is set between 240°C and 260°C, and the duration of the uniform temperature section of the preset temperature profile is 60 to 90 seconds. S6. The planar grid array solder joint structure is quality monitored by a micron focal spot X-ray system. The resolution of the X-ray system is less than or equal to 5μm, and the scanning frequency is 10 frames / second.

[0007] By adopting the above technical solutions, firstly, by customizing the solder paste formula and controlling the proportion of active flux within a reasonable range of 3%-5%, the activity and soldering stability of the solder paste can be guaranteed, the wetting effect between the solder paste and the pads can be improved, and the generation of bubbles during the soldering process can be reduced. Secondly, the preset reflow soldering temperature profile, with a peak temperature of 240-260℃ and a constant temperature (isothermal) for 60-90 seconds, can ensure that the solder paste is fully melted to achieve reliable interconnection, and can also avoid excessive solvent evaporation in the solder paste due to excessive temperature or excessive isothermal time, which would lead to voids. Finally, a high-resolution micron focal spot X-ray system is used for soldering quality monitoring, which can capture the internal state of the solder joint in real time and strictly control the void rate of the solder joint to below 5%. This effectively solves the problems of low heat conduction efficiency and unstable electrical performance caused by high void rate in traditional LGA packaging process, and significantly improves the reliability of microelectronic component packaging.

[0008] Optionally, the material of the encapsulation substrate is glass fiber reinforced epoxy resin, and the glass transition temperature (Tg) of the glass fiber reinforced epoxy resin is greater than or equal to 180°C.

[0009] By adopting the above technical solutions, the glass fiber reinforced epoxy resin encapsulation substrate with a high Tg value (≥180℃) has better high temperature resistance and structural stability. Under the high temperature conditions of reflow soldering process and subsequent long-term operation of components, the substrate is not prone to deformation or delamination. It can provide stable support and protection for solder joints and electronic components, further ensuring the overall reliability of the encapsulation structure and meeting the needs of industrial-grade wide-temperature working environment.

[0010] Optionally, the active flux includes rosin resin, an organic activator, a thixotropic agent, and a solvent, wherein the mass percentages of the rosin resin, the organic activator, the thixotropic agent, and the solvent are 60%-70%, 8%-12%, 5%-8%, and 15%-20%, respectively.

[0011] By adopting the above technical solution, in this ratio of active flux, rosin resin, as the main film-forming substance, can ensure the wettability and film-forming properties of the solder paste; organic activator can effectively remove the oxide layer of the pads and electronic component leads; thixotropic agent can improve the printability of the solder paste and avoid problems such as collapse and stringing after printing; and solvent can ensure the fluidity and workability of the solder paste. The synergistic effect of each component further optimizes the soldering performance of the solder paste, reduces the generation of solder voids, and improves the connection quality of the solder joints.

[0012] Optionally, step S2 further includes: mixing nano-sized nickel powder into the solder alloy matrix, so that the nano-sized nickel powder is uniformly dispersed in the solder alloy matrix to obtain a modified solder alloy matrix, and controlling the mass ratio of the nano-sized nickel powder to keep the liquidus temperature of the modified solder alloy matrix within a range of 15°C-45°C lower than the peak temperature of the preset temperature curve.

[0013] By adopting the above technical solution, nano-sized nickel powder is mixed into the solder alloy matrix to form a modified solder. The nano-nickel powder, as a heterogeneous nucleation point, can refine the solder grains and improve the mechanical properties of the solder joint. At the same time, by optimizing the wetting and spreading kinetics in the molten state, a channel is provided for gas escape, thereby reducing the void ratio and further improving the connection reliability and service life of the solder joint.

[0014] Optionally, the nano-sized nickel powder accounts for 0.8%-1.5% of the mass of the solder alloy matrix.

[0015] By adopting the above technical solution, the addition ratio of nano-grade nickel powder is controlled within the range of 0.8%-1.5%, which can ensure the melting characteristics and welding performance of the solder, while avoiding problems such as increased brittleness and decreased conductivity of the solder alloy due to excessive addition of nickel powder, thus achieving a balanced optimization of solder performance.

[0016] Optionally, in step S3, the electronic components are mounted using a fully automatic mounting device, wherein the positioning accuracy of the fully automatic mounting device is greater than or equal to ±0.02mm.

[0017] By adopting the above technical solutions, the fully automatic placement equipment with a high precision of ±0.02mm can ensure that electronic components are accurately placed in the preset pad positions, avoiding uneven stress on the solder joints, insufficient or excessive solder in some areas due to component misalignment, reducing defects such as voids and cold solder joints caused by placement deviations, and ensuring the electrical connection stability and structural consistency of the packaged components.

[0018] Secondly, the microelectronic component provided in this application adopts the following technical solution: A microelectronic component includes: a packaging substrate including internal interconnect pads and external interconnect pads; an electronic component soldered onto the internal interconnect pads of the packaging substrate; and a planar grid array solder joint structure formed on the external interconnect pads of the packaging substrate for soldering the microelectronic component to an external circuit board. The planar grid array solder joint structure is formed by a reflow soldering process of solder paste with a peak temperature between 240°C and 260°C and a temperature uniformity period of 60 to 90 seconds. The solder paste includes a solder alloy matrix and an active flux, wherein the active flux accounts for 3% to 5% of the total mass.

[0019] By adopting the above technical solution, the planar grid array solder joints of this microelectronic component are formed by a specific formula solder paste and a precise reflow soldering process. The 3%-5% active flux ensures the activity of the solder paste during the soldering process. The reflow soldering process with a peak temperature of 240-260℃ and a constant temperature of 60-90 seconds ensures that the solder paste is fully melted and spread evenly, reducing the formation of voids inside the solder joints. This gives the solder joints excellent electrical and thermal conductivity, solves the problem of high void rate in traditional LGA package solder joints, improves the overall operational stability and reliability of the component, and adapts to the complex working requirements of embedded devices.

[0020] Optionally, the active flux includes rosin resin, an organic activator, a thixotropic agent, and a solvent, wherein the mass percentages of the rosin resin, the organic activator, the thixotropic agent, and the solvent are 60%-70%, 8%-12%, 5%-8%, and 15%-20%, respectively.

[0021] By adopting the above technical solution, the active flux with this ratio can achieve comprehensive optimization of solder paste performance. It can not only ensure the formability and flowability of the solder paste in the printing stage, but also effectively remove the oxide layer, promote solder wetting, and reduce solder bubbles and voids in the soldering stage, thereby improving the connection quality of the planar grid array solder joints and ensuring the electrical performance and structural stability of microelectronic components.

[0022] Optionally, the material of the encapsulation substrate is glass fiber reinforced epoxy resin, and the glass transition temperature of the glass fiber reinforced epoxy resin is greater than or equal to 180°C.

[0023] By adopting the above technical solutions, the high Tg value glass fiber reinforced epoxy resin substrate has high temperature resistance and strong deformation resistance. In the high temperature welding process of component production and the wide temperature environment of subsequent use, the substrate structure can be kept stable, avoiding failures such as solder joint cracking and component displacement caused by substrate deformation, extending the service life of the component and meeting the stringent use requirements of industrial equipment.

[0024] Optionally, a heat dissipation module is also included, which is attached to the packaging substrate, and the heat dissipation area of ​​the heat dissipation module is greater than or equal to 2000 mm². 2 .

[0025] By adopting the above technical solution, the heat dissipation area is ≥2000mm². 2 The heat dissipation module can quickly conduct heat generated during the operation of microelectronic components. Combined with the excellent thermal conductivity of low-voidity solder joints, it can dissipate the heat of core components in a timely manner, avoiding performance degradation or failure of components due to local overheating. It ensures stable operation of components in a wide industrial temperature range of -40 to 85℃ and can also pass the high-temperature reliability verification of 95℃ for 10 minutes in rail transit scenarios.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. By adopting the above technical solution, firstly, by customizing the solder paste formula, the proportion of active flux is controlled within a reasonable range of 3%-5%, which ensures the activity and soldering stability of the solder paste, improves the wetting effect between the solder paste and the pads, and reduces the generation of bubbles during the soldering process. Secondly, the preset reflow soldering temperature profile, with a peak temperature of 240-260℃ and a holding temperature range of 60-90 seconds, ensures that the solder paste is fully melted to achieve reliable interconnection, while avoiding excessive solvent evaporation and void formation due to excessively high temperature or excessively long holding time. Finally, a high-resolution micron-focus X-ray system is used for soldering quality monitoring, which can capture the internal state of the solder joints in real time. By strictly controlling the solder joint void rate to below 5%, the problem of low thermal conductivity and unstable electrical performance caused by high void rate in traditional LGA packaging process is effectively solved, significantly improving the reliability of microelectronic component packaging; 2. In the active flux, rosin resin, as the main film-forming substance, can ensure the wettability and film-forming properties of solder paste, organic activator can effectively remove the oxide layer of pads and electronic component pins, thixotropic agent can improve the printability of solder paste and avoid problems such as collapse and stringing after printing, and solvent can ensure the fluidity and workability of solder paste. The synergistic effect of each component further optimizes the soldering performance of solder paste, reduces the generation of solder voids, and improves the connection quality of solder joints; 3. Nano-sized nickel powder is mixed into the solder alloy matrix to form modified solder. The nano-nickel powder can refine the solder grains, improve the mechanical properties and fatigue resistance of the solder joint, and at the same time, improve the wetting and spreading ability in the molten state, promote gas discharge, and further improve the connection reliability and service life of the solder joint. Attached Figure Description

[0027] Figure 1 This is a flowchart of a low-void packaging method for microelectronic components provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the microelectronic component provided in the embodiments of this application; Figure 3 This is the reflow soldering temperature profile corresponding to step S5 provided in the embodiments of this application.

[0028] Figure 4 This is a schematic diagram of the structure of another microelectronic component provided in the embodiments of this application.

[0029] Explanation of reference numerals in the attached figures: 1. Packaging substrate; 2. Electronic components; 3. Planar grid array solder joint structure; 4. Heat dissipation module. Detailed Implementation

[0030] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0031] This application discloses a low-void packaging method for microelectronic components. (Refer to...) Figure 1 and Figure 2 As shown, the low-void packaging method for microelectronic components includes the following steps: S1. Provide a packaging substrate 1, which includes internal interconnect pads and external interconnect pads (not shown separately in the figure); S2. Mix the solder alloy matrix and active flux in proportion, and control the mass ratio of active flux in the solder paste to 3% to 5% to prepare solder paste with the first activity level. S3. The prepared solder paste with the first activity level is uniformly coated on the internal interconnect pads and external interconnect pads of the packaging substrate 1 to perform solder paste printing on the packaging substrate 1. S4. Mount the electronic component 2 onto the internal interconnect pads of the packaging substrate 1 printed with solder paste; S5. Reflow soldering is performed on the package substrate 1 on which electronic components 2 are mounted, so that the solder paste at the internal interconnect pads melts to complete the soldering of electronic components 2 to the package substrate 1. At the same time, the solder paste at the external interconnect pads is formed into a planar grid array solder joint structure 3. The planar grid array solder joint structure 3 is used to solder microelectronic components to external circuit boards. The reflow soldering is performed according to a preset temperature profile, such as... Figure 3As shown, the peak temperature of the preset temperature curve is set between 240℃ and 260℃, and the duration of the average temperature section of the preset temperature curve is 60 to 90 seconds; S6, the quality of the planar grid array solder joint structure 3 is monitored by a micron focal spot X-ray system. The resolution of the X-ray system is less than or equal to 5μm, and the scanning frequency is 10 frames / second.

[0032] Specifically, in one embodiment, the substrate type that can be selected for the packaging substrate 1 includes glass fiber reinforced epoxy resin substrate, ceramic substrate, metal matrix composite substrate, flexible polyimide substrate, etc. Different substrates can be flexibly selected according to the application scenario of the component (such as industrial wide-temperature scenario, consumer thin and light scenario). Preferably, the material of the packaging substrate 1 is glass fiber reinforced epoxy resin, and the glass transition temperature (Tg) of the glass fiber reinforced epoxy resin is greater than or equal to 180°C. The glass fiber reinforced epoxy resin packaging substrate 1 with a high Tg value (≥180°C) has better high temperature resistance and structural stability. Under the high temperature conditions of reflow soldering process and subsequent long-term operation of the component, the substrate is not prone to deformation, delamination and other problems. It can provide stable support and protection for solder joints and electronic components 2, further ensuring the overall reliability of the packaging structure and adapting to the needs of industrial wide-temperature working environment.

[0033] In one embodiment, during the solder paste preparation stage, the solder alloy matrix can be selected from tin-lead alloy matrix, lead-free tin-silver-copper alloy matrix, tin-bismuth alloy matrix, tin-zinc alloy matrix, etc. Among them, lead-free tin-silver-copper alloy matrix is ​​suitable for environmentally friendly packaging requirements, while tin-bismuth alloy matrix is ​​suitable for low-temperature packaging scenarios. The active flux can be selected from rosin-based flux, water-soluble flux, no-clean flux, synthetic resin flux, etc. 3% to 5% by mass can be mixed into the solder alloy matrix as needed to form a first-level active solder paste suitable for low-void packaging.

[0034] It is understandable that conventional solder paste usually contains a high proportion of flux (10%). During reflow soldering, a large amount of solvent evaporates and is easily encapsulated by the molten solder, forming voids. In this application, the flux proportion is compressed to a limit of 3%-5%, which can reduce the amount of volatile gas generated from the source, thereby achieving low-void LGA packaging.

[0035] Furthermore, to compensate for insufficient wettability due to low content, the active flux includes rosin resin, organic activator, thixotropic agent, and solvent. The mass percentages of rosin resin, organic activator, thixotropic agent, and solvent are 60%-70%, 8%-12%, 5%-8%, and 15%-20%, respectively. In this formulation, rosin resin, as the main film-forming substance, ensures the wettability and film-forming properties of the solder paste. The organic activator effectively removes the oxide layer from the pads and pins of electronic components. The thixotropic agent improves the printability of the solder paste, preventing problems such as collapse and stringing after printing. The solvent ensures the solder paste... The fluidity and operability of the flux, along with the synergistic effect of its components, further optimize the soldering performance of the solder paste, reduce the generation of solder voids, and improve the connection quality of the solder joints. Preferably, the mass proportions of rosin resin, organic activator, thixotropic agent, and solvent are 65%, 10%, 6%, and 19%, respectively. By using this preferred ratio of active flux, the components can achieve synergistic performance, ensuring both the printability and wettability of the solder paste, reducing residual bubbles during the soldering process, further reducing the solder void rate to below 5%, and simultaneously increasing the shear strength of the solder joint by more than 12%, thereby enhancing the connection stability and fatigue resistance of the solder joint.

[0036] In one embodiment, the solder paste preparation process further includes the following steps: first, nano-sized nickel powder is mixed into the solder alloy matrix at a mass ratio of 0.8%-1.5%, and the nano-sized nickel powder is uniformly dispersed in the grain boundaries and gaps of the solder alloy matrix using a high-speed stirring and dispersing device (e.g., stirring speed ≥3000r / min, stirring time 15-20min) to form a modified solder alloy matrix; then, the modified solder alloy matrix is ​​mixed with active flux at a mass ratio of 95%-97%:3%-5%, and after vacuum degassing treatment (e.g., vacuum degree ≤-0.09MPa, degassing time 10-15min), a first-level active solder paste suitable for low-void packaging is obtained. Under this ratio system, by strictly controlling the mass ratio of nano-sized nickel powder, the melting point of the modified solder alloy matrix can be adapted to the temperature window of the reflow soldering process.

[0037] Understandably, mixing in nano-sized nickel powder before adding active flux can prevent the nickel powder from reacting prematurely with the organic activators and solvents in the flux. This ensures both the uniform dispersion of nickel powder within the solder alloy matrix and the preservation of the chemical activity of the active flux, ensuring that the flux's deoxidation and wetting functions are not affected in subsequent soldering stages.

[0038] Nanoscale nickel powder, as a heterogeneous nucleation point, is mainly used to refine the grain size of solder alloys. In this application, the mass ratio of nanoscale nickel powder is preferably strictly controlled at 0.8%-1.5%. This ratio aims to maintain the melting point characteristics of the solder alloy matrix and keep its liquidus temperature stable within a process window of 15°C-45°C below the reflow soldering peak temperature.

[0039] At this suitable temperature, the molten solder has excellent fluidity and wetting and spreading ability, which can fully fill the gaps between the solder pads and provide a low-resistance channel and ample time for the escape of volatile gases in the solder paste, thereby avoiding gas retention and void formation. In addition, the participation of nickel in the interfacial reaction can improve the density and thermal stability of the intermetallic compound layer, thereby enhancing the shear resistance and fatigue resistance of the solder joint.

[0040] Table 1 Comparison of the effects of nano-grade nickel powder addition on solder paste formulation and solder joint core performance. As shown in Table 1, by strictly controlling the addition of 0.8%-1.5% nano-nickel powder, the liquidus temperature of the modified solder was kept stably within the reflow soldering process window (avoiding the deterioration of fluidity caused by excessive nickel forming high-melting-point compounds), while preventing the increase in alloy brittleness and decrease in conductivity caused by excessive doping. The 3%-5% ultra-low volatile flux ratio significantly reduced the total gas release during the soldering process from the source, and combined with a highly active formula, ensured wetting speed at low dosage, achieving a synergistic effect of 'low gas generation source control + excellent wetting and spreading'. Ultimately, the solder joint void ratio was strictly controlled below 5%, and the solder joint's creep resistance under high-temperature service (95℃ for 10 minutes) and thermal fatigue life over a wide temperature range (-40℃ to 85℃) were improved by more than 10% compared to conventional solder paste, adapting to the multi-scenario requirements of environmentally friendly packaging and high-reliability packaging.

[0041] Understandably, by employing the above-mentioned technical solution, nano-sized nickel powder is incorporated into the solder alloy matrix to form a modified solder. The dispersion strengthening and heterogeneous nucleation effect of the nano-nickel powder significantly refines the solder grains and induces the formation of (Cu,Ni)6Sn5 intermetallic compounds with superior thermal stability at the interface. This optimization of the microstructure not only improves the mechanical properties of the solder joint but also effectively suppresses the growth of interfacial microvoids (Kirkendall voids) caused by high-temperature atomic interdiffusion, thereby significantly enhancing the connection reliability and service life of the solder joint during long-term service.

[0042] In one embodiment, stencil printing can be used for solder paste printing. The thickness of the stencil can be selected from 0.1mm to 0.2mm, and the aperture size matches the pad size to ensure that the solder paste coating is uniform and without deviation, and the coating range accurately covers the internal interconnect pads and the external interconnect pads.

[0043] In one embodiment, the electronic component 2 mounting process can be completed using a fully automated mounting equipment. This equipment has a positioning accuracy of no less than ±0.02mm and can be adapted to the high-precision mounting of various microelectronic devices such as integrated circuit chips, passive resistors and capacitors, sensor components, and radio frequency modules. It can ensure that the electronic component 2 is accurately mounted on the preset pad position, avoiding uneven stress on the solder joints, insufficient or excessive solder in some areas due to component misalignment, reducing defects such as solder joint voids and cold solder joints caused by mounting deviations, and ensuring the electrical connection stability and structural consistency of the packaged components.

[0044] like Figure 3 As shown, in one embodiment, the preset temperature profile of the reflow soldering stage includes a preheating zone (0-t1), a homogenizing zone (t1-t2), a reflow zone (t2-t4), and a cooling zone (after t4). The temperature in the preheating zone gradually rises to 120°C-150°C, the homogenizing zone is maintained at 150°C-220°C for 60-90 seconds (t1-t2) to fully evaporate the solvent in the solder paste, the reflow zone is heated to a peak temperature of 240°C-260°C for 10-20 seconds (around t3), and the cooling zone is rapidly cooled to room temperature using air cooling or water cooling to ensure stable solder joint formation.

[0045] Understandably, temperature, as a core control parameter of the reflow soldering process, determines the solder paste wetting effect, bubble removal efficiency, and solder joint microstructure through its curve shape and numerical combination. The temperature parameters in this application are precisely designed to match the requirements of low-void packaging. The gradient temperature rise of 120℃-150℃ in the preheating zone avoids insufficient solvent evaporation due to low temperatures (residual solvent easily forms bubbles and voids in subsequent stages) and prevents solder paste splattering and premature flux decomposition caused by sudden temperature increases. The temperature range of 150℃-220℃ in the homogenization zone, combined with a duration of 60-90 seconds, allows the solvent in the solder paste to evaporate slowly and fully, while simultaneously activating the flux, removing the oxide layer from the pads and solder surfaces, establishing a good wetting foundation for subsequent soldering, and reducing soldering defects caused by oxide film obstruction. The peak temperature of 240℃-260℃ in the reflow zone precisely matches the solder alloy matrix (especially...). The addition of nano-level modified powder to the modified solder ensures that the solder is completely melted into a liquid state to achieve sufficient wetting and interconnection. The peak duration of 10-20 seconds is just right, avoiding both insufficient solder wetting and inability to expel air bubbles due to too short a duration, and excessive solder oxidation and high-temperature aging and deformation of the packaging substrate 1 due to excessive long a duration (especially suitable for glass fiber reinforced epoxy resin substrates with a glass transition temperature ≥180℃, avoiding high-temperature damage). The rapid cooling design of the cooling zone allows the liquid solder to solidify quickly, reducing the internal stress caused by uneven temperature gradients during solidification, and preventing air bubbles from re-aggregating before the solder solidifies. This results in a dense solder joint structure without obvious voids, which works synergistically with the 3%-5% active flux ratio to further control the solder joint void rate below 5%, ensuring the thermal conductivity efficiency and electrical performance stability of the microelectronic components.

[0046] In one embodiment, the welding quality monitoring process uses a micron focal spot X-ray system with a resolution of ≤5μm and a scanning frequency of 10 frames / second. Equipment such as a microfocal X-ray detector or a high-resolution X-ray real-time imaging detection system can be selected. During the inspection, each planar grid array weld point can be scanned point by point to identify defects such as voids and cracks inside the weld point.

[0047] Understandably, in this application, by customizing the solder paste formulation and controlling the proportion of active flux within a reasonable range of 3%-5%, the activity and soldering stability of the solder paste can be guaranteed, the wetting effect between the solder paste and the pads can be improved, and the generation of bubbles during the soldering process can be reduced. Secondly, the preset reflow soldering temperature profile, with a peak temperature of 240-260℃ and a temperature equalization (isothermal) time of 60-90 seconds, can ensure that the solder paste is fully melted to achieve reliable interconnection, and can also avoid the formation of voids due to excessive solvent evaporation in the solder paste caused by excessive temperature or excessive isothermal time. Finally, the use of a high-resolution micron focal spot X-ray system for soldering quality monitoring can capture the internal state of the solder joint in real time, strictly controlling the void rate of the solder joint to below 5%, effectively solving the problems of low heat conduction efficiency and unstable electrical performance caused by high void rate in traditional LGA packaging process, and significantly improving the reliability of microelectronic component packaging.

[0048] This application also discloses a microelectronic component, such as... Figure 2 As shown, the microelectronic component includes a packaging substrate 1 and an electronic component 2. The packaging substrate 1 includes internal interconnect pads and external interconnect pads. The electronic component 2 is soldered onto the internal interconnect pads of the packaging substrate 1. A planar grid array solder joint structure 3 is formed on the external interconnect pads of the packaging substrate 1 for soldering the microelectronic component to an external circuit board. The planar grid array solder joint structure 3 is formed by a reflow soldering process of solder paste with a peak temperature between 240°C and 260°C and a temperature uniformity period of 60 to 90 seconds. The solder paste includes a solder alloy matrix and an active flux, wherein the active flux accounts for 3% to 5% of the mass.

[0049] Understandably, the planar grid array solder joints of the microelectronic components in this application are formed by a specific formula solder paste and a precise reflow soldering process. The 3%-5% active flux ensures the activity of the solder paste during the soldering process. The reflow soldering process with a peak temperature of 240-260℃ and a constant temperature of 60-90 seconds ensures that the solder paste is fully melted and spread evenly, reducing the formation of voids inside the solder joints. This gives the solder joints excellent electrical and thermal conductivity, solves the problem of high void rate in traditional LGA package solder joints, improves the overall operational stability and reliability of the components, and adapts to the complex working requirements of embedded devices.

[0050] In one embodiment, the active flux includes rosin resin, organic activator, thixotropic agent, and solvent. The mass percentages of rosin resin, organic activator, thixotropic agent, and solvent are 60%-70%, 8%-12%, 5%-8%, and 15%-20%, respectively. This ratio of active flux can achieve comprehensive optimization of solder paste performance, ensuring the formability and flowability of the solder paste during the printing stage, and effectively removing the oxide layer, promoting solder wetting, and reducing solder bubbles and voids during the soldering stage. This improves the connection quality of the planar grid array solder joints and ensures the electrical performance and structural stability of the microelectronic components.

[0051] Furthermore, the solder alloy matrix can also incorporate 0.8%-1.5% by mass of nano-grade nickel powder, which can prevent excessive nickel powder from increasing the brittleness and decreasing the conductivity of the solder alloy. By using 3%-5% active flux, the activity of the flux can be maintained while ensuring the mechanical properties of the solder, achieving a synergistic effect of "low gas generation source control + high activity to promote wetting", ensuring that the void rate of the solder joints of the microelectronic components in this application is controlled below 5%.

[0052] In one embodiment, the material of the encapsulation substrate 1 is glass fiber reinforced epoxy resin. The glass transition temperature of the glass fiber reinforced epoxy resin is greater than or equal to 180°C. The glass fiber reinforced epoxy resin substrate with a high Tg value is resistant to high temperature and has strong deformation resistance. In the high-temperature welding process of component production and the wide temperature environment of subsequent use, the substrate structure can be kept stable, avoiding failures such as solder joint cracking and component displacement caused by substrate deformation, extending the service life of the component and meeting the stringent use requirements of industrial equipment.

[0053] like Figure 4 As shown, in one embodiment, a heat dissipation module 4 is further included. The heat dissipation module 4 is attached to the packaging substrate 1, and the heat dissipation area of ​​the heat dissipation module 4 is greater than or equal to 2000 mm². 2 .

[0054] Specifically, the heat dissipation module 4 adopts an expandable integrated layered structure, which is fully adapted to the size of the packaging substrate 1. It is tightly bonded to the packaging substrate 1 with high thermal conductivity silicone with a thermal conductivity ≥3.0W / (m·K) to ensure smooth heat conduction. The basic heat dissipation layer of the module is a 0.8mm thick aluminum alloy fin array with a total of 20 fins. The size of a single fin is 45mm×12mm, and the fin spacing is 1.5mm. The heat dissipation area of ​​this passive heat dissipation layer alone can reach 2160mm². 2 Meanwhile, the heat dissipation module 4 has a pre-reserved snap-on mounting slot on the outside, which can be equipped with a 4010 specification silent fan (not shown in the figure) to form an active heat dissipation module 4, further improving the heat dissipation capacity under high load conditions.

[0055] It is understandable that the heat dissipation area is ≥2000mm². 2 The heat dissipation module 4 can quickly conduct heat generated during the operation of microelectronic components. Combined with the excellent heat conduction performance of low-voidity solder joints, it can dissipate the heat of core components in a timely manner, avoid performance degradation or failure of components due to local overheating, ensure stable operation of components in a wide industrial temperature range of -40 to 85℃, and can also pass the high-temperature reliability verification of 95℃ for 10 minutes in rail transit scenarios.

[0056] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A low-void packaging method for microelectronic components, characterized in that, Including the following steps: S1. Provide a packaging substrate (1), the packaging substrate (1) including internal interconnect pads and external interconnect pads; S2. Mix the solder alloy matrix and active flux in a certain proportion, and control the mass ratio of the active flux in the solder paste to 3% to 5% to prepare solder paste with the first activity level. S3. The prepared solder paste with the first activity level is uniformly coated on the internal interconnect pads and external interconnect pads of the packaging substrate (1) to perform solder paste printing on the packaging substrate (1). S4. The electronic component (2) is mounted on the internal interconnect pads of the package substrate (1) printed with solder paste; S5. Reflow soldering is performed on the packaging substrate (1) on which the electronic component (2) is mounted, so that the solder paste at the internal interconnect pads melts to complete the welding of the electronic component (2) and the packaging substrate (1), and at the same time, the solder paste at the external interconnect pads is formed into a planar grid array solder joint structure (3). The planar grid array solder joint structure (3) is used to weld the microelectronic components to the external circuit board. The reflow soldering is performed according to a preset temperature curve. The peak temperature of the preset temperature curve is set between 240°C and 260°C, and the duration of the uniform temperature section of the preset temperature curve is 60 to 90 seconds. S6. The quality of the planar grid array solder joint structure (3) is monitored by a micron focal spot X-ray system. The resolution of the X-ray system is less than or equal to 5 μm and the scanning frequency is 10 frames / second.

2. The low-void encapsulation method according to claim 1, characterized in that, The material of the encapsulation substrate (1) is glass fiber reinforced epoxy resin, and the glass transition temperature of the glass fiber reinforced epoxy resin is greater than or equal to 180°C.

3. The low-void encapsulation method according to claim 1, characterized in that, The active flux comprises rosin resin, organic activator, thixotropic agent and solvent, wherein the mass percentages of the rosin resin, organic activator, thixotropic agent and solvent are 60%-70%, 8%-12%, 5%-8% and 15%-20%, respectively.

4. The low-void encapsulation method according to claim 1, characterized in that, Step S2 further includes: mixing nano-sized nickel powder into the solder alloy matrix, so that the nano-sized nickel powder is uniformly dispersed in the solder alloy matrix to obtain a modified solder alloy matrix, controlling the mass ratio of the nano-sized nickel powder, so that the liquidus temperature of the modified solder alloy matrix is ​​maintained in the range of 15℃-45℃ lower than the peak temperature of the preset temperature curve.

5. The low-void encapsulation method according to claim 4, characterized in that, The nano-sized nickel powder accounts for 0.8%-1.5% of the mass of the solder alloy matrix.

6. The low-void encapsulation method according to claim 1, characterized in that, In step S3, the electronic component (2) is mounted using a fully automatic mounting device, and the positioning accuracy of the fully automatic mounting device is greater than or equal to ±0.02mm.

7. A microelectronic component, characterized in that, include: The packaging substrate (1) includes internal interconnect pads and external interconnect pads; Electronic components (2) are soldered onto the internal interconnect pads of the package substrate (1); A planar grid array solder joint structure (3) is formed on the external interconnect pads of the packaging substrate (1) for soldering microelectronic components to an external circuit board. The planar grid array solder joint structure (3) is formed by a reflow soldering curing process of solder paste with a peak temperature between 240°C and 260°C and a temperature uniformity period of 60 to 90 seconds. The solder paste includes a solder alloy matrix and an active flux, and the active flux accounts for 3% to 5% of the mass.

8. The microelectronic component according to claim 7, characterized in that, The active flux comprises rosin resin, organic activator, thixotropic agent and solvent, wherein the mass percentages of the rosin resin, organic activator, thixotropic agent and solvent are 60%-70%, 8%-12%, 5%-8% and 15%-20%, respectively.

9. The microelectronic component according to claim 7, characterized in that, The material of the encapsulation substrate (1) is glass fiber reinforced epoxy resin, and the glass transition temperature of the glass fiber reinforced epoxy resin is greater than or equal to 180°C.

10. The microelectronic component according to claim 7, characterized in that, It also includes a heat dissipation module (4), which is attached to the packaging substrate (1) and the heat dissipation area of ​​the heat dissipation module (4) is greater than or equal to 2000 mm².

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