Gradient Flux indium sheet-based packaging device and processing technology

Abstract

The invention discloses a packaging device based on a gradient Flux indium sheet and a processing technology, and belongs to the technical field of semiconductor packaging. According to the scheme, an indium matrix with the purity larger than or equal to 99.99% is adopted, gradient Flux distribution of 10-15 wt% of a surface layer / 3-5 wt% of an inner layer and 1-3% of a fumed silica thixotropic agent are matched, and material performance optimization is achieved. According to the technology innovation, double-stage Flux spraying and three-step thermal compression welding are adopted, closed-loop control is formed in combination with five AOI detection positions, and the mounting precision reaches + / -3 microns. The device integrates a vacuum-static composite grabbing module, a plasma activation module and the like. The technical effects are remarkable: the welding void rate is lt; according to the present invention, the prepared high-power electronic device thermal management material has characteristics of high thermal resistance of 0.5%, interface thermal resistance of 0.02-0.04 K.cm < 2 > / W, shear strength of more than or equal to 20 MPa and yield of 99.2%, can perfectly solve the thermal management problem of the high-power electronic device, and is especially suitable for the fields of 5G communication, new energy vehicles and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of chip packaging, and in particular relates to a packaging device and a processing technology based on a gradient Flux indium sheet. Background Art

[0002] With the rapid development of technologies such as 5G communications, artificial intelligence, and new energy vehicles, electronic devices are rapidly evolving toward higher power density and smaller form factors. This trend poses unprecedented challenges to chip packaging technology, particularly in thermal management. Traditional packaging techniques are unable to meet the stringent heat dissipation and reliability requirements of today's high-end electronic devices, necessitating the development of a new generation of thermal interface materials and supporting packaging processes.

[0003] In previous indium sheet heat dissipation packaging process equipment, the indium sheet was 100% In and required a Flux spray coating to ensure melting during the subsequent soldering process. However, the Flux-type indium sheet material itself contains Flux, eliminating the need for Flux coating during the process, which reduces the process difficulty. However, it is necessary to ensure that the Flux indium sheet does not shift due to movement and vibration, and a cleaning process is required after the packaging is completed, which adds additional costs. Secondly, the difference in thermal expansion coefficient between indium and the substrate can cause stress concentration during thermal cycling, causing the interface shear strength to rapidly decay. Furthermore, the existing packaging process requires extremely high equipment precision (alignment error must be <1μm), resulting in high production costs.

[0004] The industry has made various attempts to address these issues. Patented silver-coated indium sheets have been proposed, which slightly improve thermal resistance but triple the cost. Other existing technologies have also developed pre-mixed indium sheets, but uneven distribution of the active material can lead to soldering defects. None of these solutions has fundamentally resolved the trade-off between reliability and process feasibility. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a packaging device and processing technology based on gradient Flux indium sheets, which solves the above-mentioned technical problems existing in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A packaging device based on gradient Flux indium sheet, including a loading unit, a plasma processing unit, a glue coating and detection unit, a UV curing unit, a FLUX spraying and AOI detection unit, an indium sheet pasting unit, a heat dissipation cover pasting unit, a hot pressing unit, and a blanking unit; First, the loading unit is used to grab the Flux type indium sheet and substrate through the vacuum suction cup; The plasma treatment unit uses Ar / O2 mixed gas plasma to treat the substrate surface to reduce the contact angle to <10°; The glue coating and detection unit coats the interface material AD glue on the substrate surface and simultaneously determines the coating quality through an optical detection method; The UV curing unit uses a 365nm+395nm dual-band ultraviolet light source with an energy density of 80-120mJ / cm 2 , curing time 10–30s, synchronously control surface temperature ≤ 65°C; The spray FLUX and AOI inspection unit evenly applies flux on the substrate surface after the coating glue is cured, and simultaneously uses the AOI system to ensure the quality of the Flux coating; The indium sheet applying unit presses the indium sheet onto the substrate by electrostatic adsorption, with a bonding force of 10–20N; The heat dissipation cover applying unit completes the heat dissipation cover assembly through visual alignment and stepped pressure; The hot pressing unit performs hot pressing and forming in a step-by-step temperature increase manner, and monitors the contact resistance in real time until it reaches a stable value of <0.01Ω; The unloading unit performs sorting based on the X-ray detection results.

[0007] Furthermore, the Flux type indium sheet is an indium-based composite material, including an indium matrix and a Flux active agent; The indium substrate is made of indium or indium-silver alloy with a purity of ≥99.999%; The indium matrix is ​​uniformly distributed with a Flux active agent, which is composed of rosin, organic amine and thixotropic agent, with a total content of 5-15wt%; The thickness of the indium sheet is 0.1-0.3 mm.

[0008] Furthermore, the Flux active agent on the Flux-type indium sheet is distributed in a gradient: the surface Flux content is 10–15wt%, and the inner layer Flux content is 3–5wt%; The thixotropic agent is fumed silica, and the added amount is 1–3% of the total weight of the Flux active agent.

[0009] The processing technology of the packaging device based on the gradient Flux indium sheet includes the following steps: S1. Transfer the substrate to the plasma station through the loading unit and treat it with Ar / O2 mixed gas at 300-500W radio frequency power for 30-60s until the surface contact angle drops to <10°, wherein: the flow ratio of Ar / O2 mixed gas is 4:1; S2: Apply interface material AD glue on the substrate surface and perform optical inspection, then use UV curing with an energy density of 80-120mJ / cm 2 , control the surface temperature ≤65℃; S3, use piezoelectric spray valve to spray Flux, spraying amount 0.8-1.2mg / cm 2 , film thickness 3-5μm, and simultaneous optical inspection, so that the multi-spectral AOI detection coverage ≥ 98%, characteristic peak intensity CV ≤ 5%; S4. Selectively re-spray according to the test results of the spray FLUX and AOI detection unit, and then spray the Flux again with the piezoelectric spray valve. When the position deviation of the indium sheet is detected by 3D line laser, the piezoelectric ceramic compensation is triggered when the deviation is greater than ±0.05mm. S5, using infrared optical marking to align and control the positioning accuracy, the hot pressing unit presses in stages; S6. After lamination is completed, the finished products are inspected and sorted.

[0010] Furthermore, the loading unit is transferred to the packaging station by a vacuum adsorption-electrostatic composite fixation method, wherein the vacuum adsorption pressure is 5-10N / cm 2 , the electrostatic voltage is 200–500V.

[0011] Furthermore, the step pressure adopted by the hot pressing unit specifically includes: preheating at 80-100℃ for 10-30s to activate Flux in the first stage, low-temperature soldering at 140-150℃ for 60-90s to melt the indium sheet in the second stage, slow cooling at 100-110℃ for 20-25s in the third stage, and controlling the pressure to a constant pressure of 20-30N.

[0012] Furthermore, the stepped pressure used in the hot pressing unit specifically includes: preheating at 80-100°C for 10-30s in the first stage to activate Flux, vacuum pressure oscillation welding at 150-210°C for 20-40s in the second stage to melt the Flux active agent of the indium sheet, slow cooling at 120-130°C for 20-25s in the third stage, and controlling the pressure oscillation in the second stage to 20-30N, with the vibration amplitude fluctuating at 2-3N.

[0013] Furthermore, in S5, when it is detected that the edge coverage is less than 95%, the edge spraying path density is increased by 20%.

[0014] Beneficial effects of the present invention: 1. This device has achieved significant technological breakthroughs through the synergistic optimization of innovative gradient Flux indium sheet materials and intelligent packaging processes. In terms of key performance indicators, the solder void rate has been reduced from 3-5% in traditional processes to below 0.5%, a reduction of 85%; the interface thermal resistance has been reduced from 0.08-0.12K·cm 2 / W is optimized to 0.02-0.04K·cm 2 / W, a 60% decrease; shear strength increased from 12-14MPa to over 20MPa, a 67% increase. In terms of process efficiency, the production cycle was shortened from 60 seconds per piece to 45 seconds per piece, a 25% increase in efficiency, and the yield rate increased from 85% to 99.2%, with the defective rate reduced by 84%.

[0015] 2. This device uses Flux indium sheet material, an indium matrix with a purity of ≥99.99% combined with a gradient-distributed Flux active agent (10-15wt% for the surface layer, 3-5wt% for the inner layer), and the addition of 1-3% fumed silica thixotropic agent, to achieve precise control of the active material and intelligent rheological properties; in terms of process, a multi-sensor closed-loop control system has been developed, integrating multiple AOI inspection points to achieve ±3μm placement accuracy and real-time process compensation.

[0016] 3. The step-pressure hot pressing method of the hot pressing unit adopted in this application can greatly shorten the hot pressing time. The step-pressure hot pressing method precisely controls the "temperature-pressure-time" multi-dimensional aspects, and comprehensively surpasses the traditional constant temperature and constant pressure process in terms of interface quality, production efficiency and long-term reliability. It is particularly suitable for the packaging needs of high power density devices. 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 describing the embodiments or the prior art.

[0018] Figure 1 is an overall process flow chart of an embodiment of the present invention; Figure 2 1 is a diagram showing the working principle of a thixotropic agent according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0020] like Figure 1 As shown, an embodiment of the present invention provides a packaging device based on gradient Flux indium sheet, including a loading unit, a plasma processing unit, a glue coating and detection unit, a UV curing unit, a spray FLUX and AOI detection unit, an indium sheet pasting unit, a heat dissipation cover pasting unit, a hot pressing unit, and a blanking unit.

[0021] This device achieves precise packaging of Flux-type indium sheets through the coordinated operation of nine functional units. Its core innovations are: The gradient Flux indium sheet and the dedicated equipment for the staged pressing process embody the trinity design of materials, processes and equipment; The integration of multiple AOI inspection points enables full-process quality traceability and achieves closed-loop quality control; the Flux gradient distribution synergistically improves welding reliability. See Table 1 below for details.

[0022] Table 1

[0023] First, the loading unit includes a six-axis robotic arm and a vacuum nozzle, and the adsorption force can reach 5-8N / cm 2 The electrostatic voltage is 200–500V and it is equipped with a dual CCD visual positioning system. The positioning accuracy can be controlled within ±5μm, which enables precise grasping of Flux-type indium sheets and substrates.

[0024] Flux type indium sheet is an indium-based composite material, including an indium matrix and a Flux active agent; The indium substrate uses indium or indium-silver alloy with a purity of ≥99.999%. This high-purity indium achieves an optimal balance between ductility (elongation at break ≥50%) and thermal conductivity (86 W / m·K). Impurity levels (such as Pb and Cd) of <50 ppm prevent problems such as grain boundary embrittlement and electromigration failure. At this purity, shear strength can reach 20.5 MPa and thermal cycle life can reach 1500 cycles.

[0025] The Flux active agent is evenly distributed inside the indium matrix. The Flux active agent is composed of rosin, organic amine and thixotropic agent, with a total content of 5-15wt%. The organic amine of the Flux active agent is diethylamine, which accounts for 2-4wt% in Flux and forms a chelating effect with rosin, reducing the activation energy of copper oxide reduction to 35kJ / mol.

[0026] The thickness of the indium sheet is 0.1–0.3 mm. According to experimental results, the thermal resistance of 0.2 mm thickness is only 0.0023 K·cm. 2 / W, can improve economic benefits while achieving the best stress distribution and optimal thermal resistance control (0.018K·cm 2 / W).

[0027] At the same time, the Flux active agent on the Flux-type indium sheet is distributed in a gradient: the surface Flux content is 10-15wt%, and the inner layer Flux content is 3-5wt%. This design method preferentially forms an active protective layer at the welding interface, and its inner layer continuously replenishes the consumed active material. Compared with the uniform distribution method, the gradient distribution can reduce the welding void rate to 0.4% (while the uniform distribution welding void rate is as high as 1.2%). In addition, the gradient distribution flux residue is reduced to 0.18mg / cm 2(The uniformly distributed welding void rate is as high as 0.35mg / cm 2 ).

[0028] The thixotropic agent is fumed silica (refer to Figure 2 As shown in the figure, Flux has static high viscosity (anti-flow) and dynamic low viscosity (easy to spray), which can increase the edge coverage from 89% to 98%; the addition amount is 1-3% of the total weight of the Flux active agent. When the addition amount is less than 1%, although it can bring a higher spray atomization effect, it is easy to cause flow in a high temperature environment, affecting its application effect. When the addition amount is greater than 3%, it will over-gel and easily cause nozzle clogging. Therefore, at an addition amount of 1-3%, it can be fully optimized. By precisely controlling the addition amount and dispersion state of gas-phase SiO2, the "smart rheology" characteristics of the Flux active agent are realized, and the welding process window is widened by 40%. This is the key material innovation point of the high reliability of the present invention.

[0029] The plasma treatment unit uses Ar / O2 mixed gas plasma with a radio frequency power of 300-500W (the radio frequency power can maintain a stable plasma density) and a treatment time of 30-60s (ensuring that the surface modification depth is ≥50nm), so that the contact angle of the substrate surface is reduced from 80° to <10°. The Ar / O2 mixed gas flow ratio is 4:1. This mixed gas can balance the physical bombardment and oxidation reaction.

[0030] The first glue coating and detection unit includes a screw pump quantitative extrusion system and a 3D line laser scanner. The coating thickness is 15±2μm, the detection resolution is 0.5μm, and the coating quality is determined simultaneously by optical detection methods.

[0031] The UV curing unit adopts a 365nm+395nm dual-band UV light source with an energy density of 80-120mJ / cm 2 , curing time 10–30s, synchronously control surface temperature ≤ 65°C; The first injection FLUX and AOI inspection unit evenly applies flux on the substrate surface after the coating glue is cured, and the AOI system is used to ensure the quality of the Flux coating. It includes a piezoelectric spray valve and a multi-spectral imaging system. The minimum droplet is 5pL and the spraying amount is 0.8-1.2mg / cm 2 , film thickness 3-5μm, and simultaneous optical inspection, so that the multi-spectral AOI detection coverage ≥ 98%, characteristic peak intensity CV ≤ 5%; The indium sheet lamination unit presses the indium sheet onto the substrate through electrostatic adsorption, with a placement accuracy of ±3μm and a lamination force of 10–20N. The second spray FLUX and AOI inspection unit perform selective re-spraying based on the first spray inspection results, and then the piezoelectric spray valve sprays the Flux again. When a 3D line laser (resolution 5μm) is used to detect the position offset of the indium sheet, the piezoelectric ceramic compensation is triggered when the offset is >±0.05mm; when the edge coverage is detected to be <95%, the edge spray path density is increased by 20%.

[0032] The specific performance can be shown in Table 2 below: Table 2

[0033] The two-stage FLUX spraying method can ensure basic coverage in the first spraying, solve local defects in the second intelligent spraying, and realize quality traceability of the entire process from glue coating → FLUX → final inspection.

[0034] At the same time, the second coating glue coating + AOI inspection equipment 8 is used for heat dissipation interface material coating.

[0035] The heat sink cover application unit completes the heat sink cover assembly through visual alignment and stepped pressure; The hot pressing unit performs pressing operations with stepped pressure, and monitors the contact resistance in real time until it reaches a stable value of <0.01Ω; The hot pressing unit uses a step-by-step pressure system: the first stage is preheating at 80–100°C for 10–30 seconds to activate the Flux, the second stage is soldering at 140–150°C for 20–40 seconds to melt the indium sheet, and the third stage is slow cooling at 100–110°C for 20–25 seconds, with a pressure of 2–3 N. For specific performance information, see Table 3 below.

[0036] Table 3

[0037] Of course, the hot pressing unit can be further improved as needed.

[0038] The step-by-step pressure used in the hot pressing unit specifically includes: the first stage is preheating at 80-100℃ for 10-30s to activate Flux, the second stage is vacuum pressure oscillation welding at 150-210℃ for 20-40s to melt the Flux active agent of the indium sheet, and the third stage is slow cooling at 120-130℃ for 20-25s. The pressure oscillation in the second stage is controlled to 20-30N, and the vibration amplitude fluctuates within 2-3N.

[0039] Please refer to Table 4 below for specific performance.

[0040] Table 4

[0041] The second-stage soldering processes used in Tables 3 and 4 differ, primarily to address different chip packages (Table 3 primarily handles chips with an IMC thickness of 30-50nm, while the method in Table 4 can handle chip packages with an IMC thickness of 80-100nm). Compared to traditional constant temperature and constant pressure, the void rate can be reduced to ≤0.3% (compared to 0.8-1.5% for traditional constant temperature and constant pressure), a reduction of over 75%. Furthermore, the staged hot pressing method achieves shear strength ≥22MPa, while traditional constant pressure and constant temperature hot pressing achieves shear strength ≤15MPa.

[0042] The unloading unit performs sorting based on the X-ray inspection results.

[0043] Compared with the existing technical solutions, this application has the following economic benefits, as shown in Table 5: Table 5

[0044] Through system-level innovation, this technical solution has achieved simultaneous breakthroughs in thermal conductivity, mechanical strength, and production efficiency, solving the long-standing "high thermal conductivity-high reliability-low cost" problem in the field of high-power electronic chip packaging.

[0045] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A packaging device based on gradient Flux indium sheet, characterized in that: It includes loading unit, plasma processing unit, glue coating and detection unit, UV curing unit, FLUX spraying and AOI detection unit, indium sheet pasting unit, heat dissipation cover pasting unit, hot pressing unit and unloading unit; First, the loading unit is used to grab the Flux type indium sheet and substrate through the vacuum suction cup; The plasma treatment unit uses Ar / O2 mixed gas plasma to treat the substrate surface to reduce the contact angle to <10°; The glue coating and detection unit coats the interface material AD glue on the substrate surface and simultaneously determines the coating quality through an optical detection method; The UV curing unit uses a 365nm+395nm dual-band ultraviolet light source with an energy density of 80-120mJ / cm 2 , curing time 10–30s, synchronously control surface temperature ≤ 65°C; The spray FLUX and AOI inspection unit evenly applies flux on the substrate surface after the coating glue is cured, and simultaneously uses the AOI system to ensure the quality of the Flux coating; The indium sheet applying unit presses the indium sheet onto the substrate by electrostatic adsorption, with a bonding force of 10–20N; The heat dissipation cover applying unit completes the heat dissipation cover assembly through visual alignment and stepped pressure; The hot pressing unit performs hot pressing and forming in a step-by-step temperature increase manner, and monitors the contact resistance in real time until it reaches a stable value of <0.01Ω; The unloading unit performs sorting based on the X-ray detection results.

2. The packaging device based on the gradient Flux indium sheet according to claim 1, characterized in that: The Flux type indium sheet is an indium-based composite material, including an indium matrix and a Flux active agent; The indium substrate is made of indium or indium-silver alloy with a purity of ≥99.999%; The indium matrix is ​​uniformly distributed with a Flux active agent, which is composed of rosin, organic amine and thixotropic agent, with a total content of 5-15wt%; The thickness of the indium sheet is 0.1-0.3 mm.

3. The packaging device based on the gradient Flux indium sheet according to claim 2, characterized in that: The Flux active agent on the Flux-type indium sheet is distributed in a gradient manner: the Flux content in the surface layer is 10–15 wt%, and the Flux content in the inner layer is 3–5 wt%; The thixotropic agent is fumed silica, and the added amount is 1–3% of the total weight of the Flux active agent.

4. The processing technology of the packaging device based on the gradient Flux indium sheet according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Transfer the substrate to the plasma station through the loading unit and treat it with Ar / O2 mixed gas at 300-500W radio frequency power for 30-60s until the surface contact angle drops to <10°, wherein: the flow ratio of Ar / O2 mixed gas is 4:1; S2: Apply interface material AD glue on the substrate surface and perform optical inspection, then use UV curing with an energy density of 80-120mJ / cm 2 , control the surface temperature ≤65℃; S3, use piezoelectric spray valve to spray Flux, spraying amount 0.8-1.2mg / cm 2 , film thickness 3-5μm, and simultaneous optical inspection, so that the multi-spectral AOI detection coverage ≥ 98%, characteristic peak intensity CV ≤ 5%; S4. Selectively re-spray according to the test results of the spray FLUX and AOI detection unit, and then spray the Flux again with the piezoelectric spray valve. When the position deviation of the indium sheet is detected by 3D line laser, the piezoelectric ceramic compensation is triggered when the deviation is greater than ±0.05mm. S5, using infrared optical marking to align and control the positioning accuracy, the hot pressing unit presses in stages; S6. After lamination is completed, the finished products are inspected and sorted.

5. The processing technology of the packaging device based on the gradient Flux indium sheet according to claim 4 is characterized in that: The loading unit is transferred to the packaging station by a vacuum adsorption-electrostatic composite fixation method, wherein the vacuum adsorption pressure is 5-10N / cm 2 , the electrostatic voltage is 200–500V.

6. The processing technology of the packaging device based on the gradient Flux indium sheet according to claim 4 is characterized in that: The step pressure used by the hot pressing unit specifically includes: the first stage is preheating at 80-100℃ for 10-30s to activate the Flux, the second stage is low-temperature soldering at 140-150℃ for 60-90s to melt the indium sheet, and the third stage is slow cooling at 100-110℃ for 20-25s, and the pressure is controlled to be a constant pressure of 20-30N.

7. The processing technology of the packaging device based on the gradient Flux indium sheet according to claim 4 is characterized in that: The step pressure used in the hot pressing unit specifically includes: preheating at 80-100°C for 10-30s to activate Flux in the first stage, vacuum pressure oscillation welding at 150-210°C for 20-40s to melt the Flux active agent of the indium sheet in the second stage, slow cooling at 120-130°C for 20-25s in the third stage, and controlling the pressure oscillation to 20-30N, with the vibration amplitude fluctuating at 2-3N.

8. The processing technology of the packaging device based on the gradient Flux indium sheet according to claim 4 is characterized in that: In S5, when it is detected that the edge coverage is less than 95%, the edge spraying path density is increased by 20%.

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