Improved photoelectric coupler packaging electroplating process

Abstract

The invention relates to an improved photoelectric coupler packaging electroplating technology which comprises the following steps that S10, self-repairing microcapsules are dispersed into electroplating liquid, the microcapsules comprise wall materials and core materials, and the core materials comprise vinyl siloxane and chloroplatinic acid catalysts; s20, sequentially forming a nano gradient composite coating structure on the surface of the substrate, wherein the composite coating structure comprises a substrate layer, a transition layer, a main functional layer and a packaging layer; and S30, carrying out micro-area deposition by adopting a light-induced selective electroplating process, wherein the micro-area deposition comprises laser micro-area activation, pulse electroplating deposition and in-situ ultraviolet curing. According to the electroplating process, through the nanometer gradient composite coating structure, the interface stress concentration is reduced through layer-by-layer transition of the material and the thickness, the thermal cycle resistance of the coating is improved, and meanwhile the balance among conductivity, mechanical strength and thermal stability is achieved.

Description

Technical Field

[0001] This application relates to the field of electroplating technology, and particularly to an improved electroplating process for optocoupler packaging. Background Art

[0002] The packaging electroplating process of optocouplers directly affects the reliability of devices in high-frequency signal transmission and harsh environments. Although the traditional nickel / gold (Ni / Au) electroplating system can provide basic protection, in high-frequency application scenarios, there is a significant negative correlation between the porosity of the coating and signal loss: reducing the porosity requires increasing the coating thickness, but this results in a signal loss of more than 3 dB above 10 MHz; while thinning the coating can suppress the loss, it will increase the pore density to more than 5 pores / cm², accelerating the penetration of environmental media. Existing improvement schemes mostly adopt composite coatings or adjust electroplating parameters, but the non-uniform dispersion of nanoparticles easily causes interfacial stress concentration, resulting in microcracks in the coating during thermal cycling (-55°C to 150°C). In addition, the precise deposition of micron-scale pin spacings relies on physical masks, and the edge diffusion effect causes the coating morphology to get out of control, making it difficult to meet the requirements of ±2 μm accuracy for 5G communication devices. More prominently, due to oxidation and microcrack propagation in the existing coatings in a high-temperature and high-humidity (85°C / 85%RH) environment, the contact resistance increases by more than 30% within 1000 hours, and a single structural optimization or process adjustment cannot simultaneously solve the complex technical problems of high-frequency performance, micro-area deposition accuracy, and long-term reliability degradation. Summary of the Invention

[0003] This application provides an improved electroplating process for optocoupler packaging, including the following steps: S10. Dispersing self-healing microcapsules into the electroplating solution, the microcapsules comprising a wall material and a core material, and the core material comprising vinyl siloxane and chloroplatinic acid catalyst; S20. Sequentially forming a nano-gradient composite coating structure on the surface of the substrate, the composite coating structure including a base layer, a transition layer, a main functional layer, and a packaging layer; S30. Performing micro-area deposition using a photoinduced selective electroplating process, including laser micro-area activation, pulse electroplating deposition, and in-situ ultraviolet curing.

[0004] In some embodiments, the base layer in step S20 is a silver deposition layer with a thickness of 1.0 ± 0.2 μm and a purity of ≥99.9%; the transition layer is a composite layer of Ni-SiO 2 and BN with a thickness of 0.5 μm, where the total volume of SiO 2 and BN in the transition layer accounts for 15 - 25% of the transition layer, and the volume ratio of SiO 2 to BN in the transition layer is 3:1.

[0005] In some embodiments, SiO 2The particle size of is 5 nm, the thickness of the BN layer is 50 nm, and the transition layer is formed by an electrophoresis-electroplating collaborative process.

[0006] In some embodiments, the main functional layer in step S20 is obtained by electroplating based on a nickel sulfamate electroplating solution, the thickness of the main functional layer is 3.0±0.5 μm, and the Vickers hardness of the main functional layer is HV 520±30.

[0007] In some embodiments, the encapsulation layer in step S20 is a composite layer of siloxane and BN, with a thickness of 20±5 μm and a thermal conductivity of ≥1.8 W / (m·K).

[0008] In some embodiments, in step S30, the area of ​​micro-area deposition is the pin area of ​​the optocoupler, and the laser micro-area activation uses an ultraviolet laser with a wavelength of 355nm, a power density of 8J / cm², and a frequency of 20kHz.

[0009] In some embodiments, the current density of the forward current of the pulse electroplating deposition in step S30 is 5A / dm² and the pulse width is 10ms, and the current density of the reverse current is 1A / dm² and the pulse width is 2ms.

[0010] In some embodiments, the in-situ UV curing in step S30 is performed in a nitrogen atmosphere with an oxygen content of <50 ppm, using a 365 nm LED array light source with a light intensity of 50 mW / cm².

[0011] In some embodiments, the volume proportion of the self-healing microcapsules in step S10 is 15±2%, the wall material is polyurea formaldehyde, the thickness of the wall material is 200±50 nm, and the glass transition temperature of the wall material is 85°C.

[0012] In some embodiments, the molecular weight of the vinyl siloxane in the core material is 5000, the vinyl content is 0.1 mol %, and the amount of chloroplatinic acid catalyst added is 0.05 wt %.

[0013] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: 1. Through the nano-gradient composite coating structure, the layer-by-layer transition of materials and thickness reduces the interface stress concentration, improves the coating's resistance to thermal cycling, and achieves a balance between conductivity, mechanical strength and thermal stability.

[0014] 2. Through the light-induced selective electroplating process, the time-space control characteristics realize selective plating, avoiding the edge effect of the traditional mask process and forming a high-density, low-stress functional coating.

[0015] 3. Through the self-healing microcapsule system, a dynamic repair network is formed inside the coating, significantly delaying the deterioration of electrical conductivity caused by environmental erosion, and filling defects through cross-linking reactions when microcracks occur.

[0016] 4. By controlling the purity and thickness of the silver-based bottom layer, the interfacial contact resistance is reduced and the current distribution uniformity is improved, providing a flat surface for the subsequent coating.

[0017] 5. Through the volume ratio of SiO 2 to BN of 3:1 in the transition layer and the electrophoretic-electroplating synergistic process, the thermal cycle shear stress is dissipated synergistically by the slip of BN lamellae and the pinning effect of SiO 2 particles, inhibiting the initiation of interfacial cracks, and at the same time forming a multi-scale reinforcement structure to improve the density.

[0018] 6. By controlling the thickness of the nickel main functional layer and the Vickers hardness (HV 520±30), the coating resists mechanical wear and relieves thermal expansion stress, while maintaining low resistance characteristics and long-term dynamic stability.

[0019] 7. Through the silicone oxide and BN composite layer of the encapsulation layer, heat is rapidly diffused along the BN plane direction, blocking the penetration of water and oxygen, and reducing the thermal mismatch stress between the coating and the external material.

[0020] 8. Through the laser micro-area activation parameters of the pin area of the optoelectronic coupler, a nanoscale rough structure is formed on the surface and the distribution of active sites is precisely regulated, avoiding thermal damage to the substrate.

[0021] 9. Through the asymmetric parameters of pulse electroplating, the pores and grain boundary defects of the coating are reduced, the surface roughness is decreased, and at the same time the purity and bonding strength are improved.

[0022] 10. Through the in-situ ultraviolet curing nitrogen atmosphere and light parameters, the cross-linking density of the encapsulation layer is increased, the interfacial bonding is tight, and the environmental moisture and corrosive media are effectively blocked.

[0023] 11. By controlling the volume fraction, wall thickness and glass transition temperature of the self-healing microcapsules, the repair function is activated only at the high-temperature working limit, ensuring effective repair coverage and process controllability.

[0024] 12. Through the molecular weight, vinyl content and chloroplatinic acid addition amount of vinylsiloxane in the core material, the microcracks are quickly sealed and the mechanical properties are restored, while avoiding the risk of electrochemical corrosion caused by catalyst residues. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings herein are incorporated into the specification and form a part of the specification, showing embodiments in accordance with the present invention, and are used together with the specification to explain the principles of the present invention.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of an improved electroplating process for an opto - coupler package provided by an embodiment of the present application. Specific embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0029] Figure 1 It shows a flowchart of an improved electroplating process for an opto - coupler package provided by an embodiment of the present application.

[0030] As Figure 1 shown, the present application provides an improved electroplating process for an opto - coupler package, including the following steps: S10. Disperse self - healing microcapsules into the electroplating solution. The microcapsules include a wall material and a core material, and the core material includes vinyl siloxane and chloroplatinic acid catalyst. S20. Sequentially form a nano - gradient composite coating structure on the surface of the substrate. The composite coating structure includes a base layer, a transition layer, a main functional layer, and a packaging layer. S30. Adopt a photo - induced selective electroplating process for micro - area deposition, including laser micro - area activation, pulse electroplating deposition, and in - situ ultraviolet curing.

[0031] In some embodiments, the transition layer and the main functional layer are electroplated from an electroplating solution containing self - healing microcapsules, and the area of the micro - area deposition is the pin area of the opto - coupler.

[0032] The self - healing microcapsules are uniformly dispersed in the coating during the electroplating processes of the transition layer, the main functional layer, and the micro - area deposition. When micro - cracks occur in the coating, mechanical stress causes the microcapsules to rupture and release the core material, and vinyl siloxane undergoes a cross - linking reaction under the catalysis of chloroplatinic acid to fill the defects. The self - healing system forms a dynamic repair network inside the coating, significantly delaying the deterioration of the electrical conductivity caused by environmental erosion.

[0033] The base layer provides a highly conductive substrate. The transition layer alleviates the thermal stress mismatch through the design of the heterogeneous material interface. The main functional layer undertakes the main functions of conduction and mechanical support. The encapsulation layer realizes environmental isolation and thermal management. The nano-gradient structure reduces the interfacial stress concentration through the gradual transition of materials and thickness, and improves the thermal cycle resistance of the coating.

[0034] In step S30, the ultraviolet laser selectively activates the surface of the micro-region pin area. First, the ultraviolet laser is used to selectively activate key areas such as pins, cleaning the surface and enhancing the electrochemical activity through the photothermal effect. Subsequently, a nickel layer containing self-healing microcapsules is preferentially deposited on the activated area by pulse electroplating, using asymmetric current to inhibit dendrite growth and embed the microcapsules. Finally, the encapsulation layer is in-situ cured by ultraviolet light to form a dense protective structure. It realizes high-precision plating, the construction of a dynamic repair network, and rapid encapsulation and shaping, significantly improving the conductive stability, environmental erosion resistance, and long-term reliability of the coating, and avoiding the edge effect of the traditional masking process.

[0035] In some embodiments, in step S20, the base layer is a silver deposition layer with a thickness of 1.0 ± 0.2 μm and a purity ≥ 99.9%; the transition layer is a composite layer of Ni-SiO 2 and BN with a thickness of 0.5 μm, where the total volume of SiO 2 and BN in the transition layer accounts for 15 - 25% of the transition layer, and the volume ratio of SiO 2 to BN in the transition layer is 3:1.

[0036] The silver deposition layer serves as the substrate. Its high purity (≥ 99.9%) and precise thickness (1.0 ± 0.2 μm) provide a low-resistance conductive path and a flat surface for the subsequent coatings. In the transition layer, Ni-SiO 2 and BN are compounded at a volume ratio of 3:1. Utilizing the rigid support of SiO 2 nanoparticles and the lubricating characteristics of BN lamellae, the thermal expansion coefficient of the coating is adjusted through the synergistic effect of the two phases. Among them, the Ni matrix serves as the continuous phase to achieve metallurgical bonding with the base layer, while the SiO 2 / BN composite phase is dispersed in the Ni matrix to form a stress buffer network, thereby realizing a gradual transition of mechanical properties within a thickness range of 0.5 μm.

[0037] By controlling the high purity and thickness of the silver substrate, the interfacial contact resistance is reduced and the current distribution uniformity is improved. The 3:1 volume ratio of SiO 2 to BN in the transition layer optimizes the internal stress distribution of the coating, enabling the shear stress generated during the thermal cycle of the composite layer to be dissipated by the slip of BN lamellae and SiO 2The grain pinning effect synergistically dissipates energy, thereby inhibiting the initiation of interfacial cracks; at the same time, the thickness of the transition layer is precisely controlled within the range of 0.5 μm, which not only ensures the stress buffering function but also avoids the increase in coating brittleness caused by excessive thickness, ultimately achieving the balance of the coating structure among conductivity, mechanical strength, and thermal stability.

[0038] In some embodiments, the SiO in the transition layer 2 has a particle size of 5 nm, and the BN sheet has a thickness of 50 nm. The transition layer is formed by an electrophoretic-electroplating synergistic process.

[0039] The transition layer is formed by an electrophoretic-electroplating synergistic process. The core lies in using the electrophoretic effect to drive the directional migration of nano-SiO 2 particles (particle size 5 nm) and BN sheets (thickness 50 nm) to the surface of the base layer, and then embedding the nanoparticles into the metal matrix through the deposition process of electroplated nickel. During the electrophoretic stage, the charged SiO 2 and BN form a stable dispersion system in the solution by regulating the electric field strength, while during the electroplating stage, a continuous metal phase is formed through the reduction deposition of nickel ions, uniformly coating the nanoparticles at a volume ratio of 3:1, and finally forming a composite transition layer with a nanoscale heterogeneous structure.

[0040] By precisely controlling the size and composite ratio of the SiO 2 nanoparticles and BN sheets, combined with the electrophoretic-electroplating synergistic effect, a multi-scale reinforcement structure is formed inside the transition layer: 5-nm SiO 2 particles fill the gaps between BN sheets to reduce porosity, 50-nm-thick BN sheets enhance the interlayer bonding force through in-plane oriented arrangement, and the synergistic effect between the nickel matrix and nanoparticles can effectively alleviate the thermal expansion mismatch problem. This structural design enables the transition layer to have both high density and stress buffering ability, providing stable interfacial support for the subsequent main functional layer, and at the same time optimizing the overall mechanical properties of the coating through the gradient distribution of nanoparticles.

[0041] In some embodiments, the main functional layer in step S20 is electroplated from a nickel sulfamate plating solution. The thickness of the main functional layer is 3.0 ± 0.5 μm, and the Vickers hardness of the main functional layer is HV 520 ± 30.

[0042] The nickel sulfamate plating solution forms a low-stress nickel coating during the deposition process. By controlling the current density and plating solution temperature, the nickel grains preferentially grow along the (220) crystal plane. The setting of the thickness of 3.0 ± 0.5 μm not only ensures the mechanical protection requirement of the coating for the substrate but also avoids the accumulation of internal stress caused by excessive thickness.

[0043] The nickel plating forms a dense crystal structure within the thickness range of 3.0 ± 0.5 μm. Its hardness value of HV 520 ± 30 can not only resist mechanical wear during pin insertion and extraction, but also relieve thermal expansion stress through the slip mechanism of nano-equiaxed crystals. The precise thickness control enables the plating to maintain low-resistance characteristics while providing a flat interface basis for the subsequent encapsulation layer. The low-stress characteristic can avoid microcracks caused by lattice distortion of the plating in a high-temperature environment, thus ensuring the long-term stability of the electroplated layer under dynamic working conditions.

[0044] In some embodiments, the encapsulation layer described in step S20 is a composite layer of silicone and BN, with a thickness of 20 ± 5 μm and a thermal conductivity ≥ 1.8 W / (m·K).

[0045] Through the synergistic effect of BN lamellae and silicone, the encapsulation layer achieves a balance of high thermal conductivity and mechanical flexibility at a thickness of 20 ± 5 μm. The oriented arrangement of BN enables heat to rapidly diffuse along the plane direction, avoiding local heat accumulation. The elastic modulus adaptability of silicone reduces the thermal mismatch stress between the plating and the external encapsulation material. At the same time, its dense network structure effectively blocks the penetration of water and oxygen. The precise control of the thickness range not only ensures the heat dissipation efficiency but also avoids the increase in process cost or the decrease in interfacial bonding force caused by excessive thickness, ultimately achieving a comprehensive improvement in the thermal management, environmental protection, and mechanical reliability of the encapsulation layer.

[0046] In some embodiments, the laser micro-area activation described in step S30 uses ultraviolet laser with a wavelength of 355 nm, a power density of 8 J / cm², and a frequency of 20 kHz.

[0047] The laser micro-area activation uses ultraviolet laser with a wavelength of 355 nm. Its photon energy (about 3.5 eV) is sufficient to break the chemical bonds of the metal surface oxide, forming a micron-level activation area on the surface of the pin area of the optoelectronic coupler through the photothermal effect. The setting of the power density of 8 J / cm² enables the laser energy to generate instantaneous high temperature (>1500 °C) per unit area, selectively removing surface contaminants and forming a nano-level rough structure. At the same time, the high-frequency pulse of 20 kHz restricts the depth of heat diffusion through fast on-off control (single-pulse action time ≤ 50 ns), avoiding thermal damage to the substrate material, thereby precisely regulating the distribution of surface active sites within the micro-area range.

[0048] In some embodiments, the current density of the forward current in the pulse electroplating deposition described in step S30 is 5 A / dm², the pulse width is 10 ms, the current density of the reverse current is 1 A / dm², and the pulse width is 2 ms.

[0049] By setting the alternating parameters of the forward current of 5 A / dm² (pulse width 10 ms) and the reverse current of 1 A / dm² (pulse width 2 ms) for pulse electroplating deposition, the metal deposition process is regulated by utilizing the kinetic characteristics of asymmetric pulses. In the forward high-current stage, nickel ions are rapidly migrated to the cathode surface to form dense crystal nuclei, and the 10-ms pulse width ensures that the crystal nuclei fully grow into a continuous coating; in the reverse low-current stage, through short-term anodic dissolution (1 A / dm², 2 ms), the dendritic tips and adsorbed hydrogen bubbles generated during the deposition process are selectively removed, while maintaining the dynamic balance of the ion concentration in the plating solution, thereby realizing the periodic optimization of the coating structure at the microscale.

[0050] Through the synergistic effect of forward deposition and reverse micro-etching, the pulse parameters inhibit the common pore and grain boundary defects in traditional DC electroplating: the forward current density and pulse width match the diffusion rate of nickel ions, avoiding the looseness of the coating caused by concentration polarization; the reverse short-pulse-width micro-etching precisely removes the surface protrusions, significantly reducing the surface roughness of the coating. At the same time, the weak anodic effect of the reverse current can remove adsorbed impurities, improving the purity and bonding strength of the coating, and finally forming a functional coating with both high density and low stress.

[0051] In some embodiments, the in-situ ultraviolet curing described in step S30 is carried out in a nitrogen atmosphere with an oxygen content < 50 ppm, using a 365-nm LED array light source with a light intensity of 50 mW / cm².

[0052] The nitrogen atmosphere eliminates the quenching effect of oxygen molecules on the free radical polymerization reaction by displacing oxygen in the reaction zone, enabling ultraviolet light energy to fully excite the activity of the photoinitiator; the 365-nm wavelength matches the absorption peak of common photoinitiators (such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), ensuring the efficient conversion of light energy into chemical energy; the 50-mW / cm² light intensity setting ensures the curing rate while avoiding the thermal deformation of the coating caused by the photothermal effect, and the continuous nitrogen purge maintains a low-oxygen environment, blocking the secondary pollution of oxygen to the curing interface.

[0053] Through the synergistic effect of nitrogen protection and light parameters, the curing crosslinking density is significantly improved: the low-oxygen environment reduces the residual unreacted double bonds, increasing the density of the encapsulation layer; the high photon energy of the 365-nm light source ensures the uniformity of deep curing, avoiding the multi-wavelength interference of traditional mercury lamps; the 50-mW / cm² light intensity maintains the stability of the coating structure by controlling the photothermal input while ensuring the curing efficiency, and finally forms an encapsulation layer without oxygen defects and with a tightly bonded interface, effectively blocking the penetration of environmental moisture and corrosive media.

[0054] In some embodiments, the volume ratio of the self-healing microcapsules described in step S10 is 15 ± 2%, the wall material is polyurea formaldehyde, the thickness of the wall material is 200 ± 50 nm, and the glass transition temperature of the wall material is 85 °C.

[0055] Self-healing microcapsules are uniformly dispersed in the electroplating solution at a volume ratio of 15 ± 2%. The thickness of the polyurea formaldehyde wall material of 200 ± 50 nm is precisely controlled by interfacial polymerization reaction, and its glass transition temperature (Tg = 85 °C) matches the working temperature threshold of the optoelectronic coupler. When microcracks occur in the coating due to mechanical stress or thermal cycling, when the local temperature approaches or exceeds 85 °C, the molecular chain segment mobility of the polyurea formaldehyde wall material increases, resulting in the softening of the microcapsule wall material and preferential rupture in the stress concentration area, releasing the core material to the defect, and the volume ratio of 15 ± 2% ensures that there is sufficient microcapsule distribution density per unit area to achieve effective repair coverage.

[0056] The ratio of 15 ± 2% not only avoids the decrease in coating density caused by excessive addition but also ensures that there are enough microcapsules on the crack propagation path to trigger repair. The wall thickness of 200 ± 50 nm reduces the rupture energy barrier while maintaining mechanical stability, and the glass transition temperature of 85 °C enables the microcapsules to activate the repair function only when the device approaches the high-temperature working limit, avoiding mis-triggering during normal temperature storage or transportation, thus achieving an optimized balance between coating reliability and process controllability.

[0057] In some embodiments, the molecular weight of vinyl siloxane in the core material is 5000, the vinyl content is 0.1 mol%, and the addition amount of chloroplatinic acid catalyst is 0.05 wt%.

[0058] Vinyl siloxane with a molecular weight of 5000 has moderate chain segment mobility and can fully fill the crack gap after the microcapsules rupture. The vinyl content of 0.1 mol% provides a balance between crosslinking site density and material ductility, ensuring the viscosity controllability of the repair agent during diffusion. The loading amount of 0.05 wt% of chloroplatinic acid catalyst controls the crosslinking reaction rate through the number of catalytic active centers, matching the triggering condition with the glass transition temperature (85 °C) of the polyurea formaldehyde wall material, enabling the repair reaction to be efficiently initiated within the working temperature range of the coating.

[0059] Vinyl siloxane with a molecular weight of 5000 forms a low-viscosity mobile phase at the crack. The vinyl content of 0.1 mol% ensures that the crosslinking network density can cure quickly and avoid excessive embrittlement, while the amount of 0.05 wt% of chloroplatinic acid catalyst synchronizes the crosslinking reaction rate with the diffusion rate of the repair agent. The three work together to quickly seal microcracks and restore the mechanical properties when the coating is damaged, while avoiding the risk of electrochemical corrosion of the coating caused by excessive catalyst residues.

[0060] The method of the present invention will be described in detail below in combination with examples, comparative examples and experimental data.

[0061] Example 1

[0062] This embodiment provides an improved optocoupler packaging electroplating process, the method comprising the following steps: Step 1: Add 400 g / L sulfamate nickel plating solution at a volume ratio of 15% to microcapsules with a wall material of polyurea formaldehyde (thickness 200 nm, Tg = 85 ° C), a core material of vinyl siloxane with a molecular weight of 5000 (vinyl content 0.1 mol%) and 0.05 wt% chloroplatinic acid catalyst, and use ultrasonic dispersion for 30 minutes to evenly suspend the microcapsules to obtain an electroplating solution.

[0063] Step 2: First, a 1.0 μm thick silver base coating is deposited by magnetron sputtering process, with a purity of 99.92% and a surface roughness of Ra ≤ 0.1 μm. Then, a transition layer is formed on the surface of the silver layer by electrophoresis-electroplating synergistic process: SiO 2 Nanoparticles and BN with a thickness of 50 nm were dispersed in the electroplating solution obtained in step 1 at a volume ratio of 3:1. An electric field strength of 15 V / cm was applied for electrophoretic deposition for 30 seconds. Then, the electroplating mode was switched to deposit Ni-SiO with a thickness of 0.5 μm at a current density of 3 A / dm². 2 / BN composite layer, the transition layer contains SiO 2 The total volume of BN accounts for 20% of the transition layer. Then, a 3.0μm thick nickel main functional layer is electroplated on the transition layer, and the plating solution temperature is maintained at 50°C and the pH value is 4.2. Finally, a 20μm thick siloxane / BN encapsulation layer is formed on the surface by spraying, of which BN accounts for 40% by mass. After curing at 120°C, the encapsulation layer is prepared.

[0064] Step 3: Use a 355nm UV laser to micro-activate the pin area, set the power density to 8J / cm², the frequency to 20kHz, the spot diameter to 5μm, and the positioning accuracy to be controlled within the range of ±2μm. Immediately after activation, pulse electroplating deposition is performed using the electroplating solution obtained in step 1, alternating between a forward current of 5A / dm² (pulse width 10ms) and a reverse current of 1A / dm² (pulse width 2ms), with a total deposition time of 15 minutes. After deposition, the workpiece is transferred to a nitrogen protection chamber (oxygen content 45ppm), and in-situ UV curing is performed using a 365nm LED array light source with a light intensity of 50mW / cm², and irradiation is continued for 120 seconds.

[0065] Example 2

[0066] This embodiment provides an improved optocoupler packaging electroplating process, the method comprising the following steps: Step 1: Add 400 g / L sulfamate nickel plating solution at a volume ratio of 17% to microcapsules with a wall material of polyurea formaldehyde (thickness 200 nm, Tg = 85 ° C), a core material of vinyl siloxane with a molecular weight of 5000 (vinyl content 0.1 mol%) and 0.05 wt% chloroplatinic acid catalyst, and use ultrasonic dispersion for 30 minutes to evenly suspend the microcapsules to obtain an electroplating solution.

[0067] Step 2: First, a 1.2μm thick silver base coating is deposited by magnetron sputtering process, with a purity of 99.92% and a surface roughness of Ra≤0.1μm. Then, a transition layer is formed on the surface of the silver layer by electrophoresis-electroplating synergistic process: SiO 2 Nanoparticles and BN with a thickness of 50 nm were dispersed in the electroplating solution obtained in step 1 at a volume ratio of 3.5:1. An electric field strength of 15 V / cm was applied for electrophoretic deposition for 30 seconds. Then, the electroplating mode was switched to deposit Ni-SiO with a thickness of 0.5 μm at a current density of 3 A / dm². 2 / BN composite layer, the transition layer contains SiO 2 The total volume of BN accounts for 20% of the transition layer. Then, a 3.5μm thick nickel main functional layer is electroplated on the transition layer, and the plating solution temperature is maintained at 50°C and the pH value is 4.2. Finally, a 25μm thick siloxane / BN encapsulation layer is formed on the surface by spraying, of which BN accounts for 40% by mass. After curing at 120°C, the encapsulation layer is prepared.

[0068] Step 3: Use a 355nm UV laser to micro-activate the pin area, set the power density to 7J / cm², the frequency to 20kHz, the spot diameter to 5μm, and the positioning accuracy to be controlled within the range of ±2μm. Immediately after activation, pulse electroplating deposition is performed based on the electroplating solution obtained in step 1, with a forward current of 5.5A / dm² (pulse width 10ms) and a reverse current of 1A / dm² (pulse width 2ms) alternating, with a total deposition time of 15 minutes. After deposition is completed, the workpiece is transferred to a nitrogen protection chamber (oxygen content 30ppm), and a 365nm LED array light source is used for in-situ UV curing at a light intensity of 50mW / cm², and the irradiation lasts for 120 seconds.

[0069] Example 3

[0070] This embodiment provides an improved electroplating process for photoelectric coupler packaging, the method comprising the following steps: Step 1: Add 400 g / L sulfamate nickel plating solution at a volume ratio of 13% to microcapsules with a wall material of polyurea formaldehyde (thickness 200 nm, Tg = 85 ° C), a core material of vinyl siloxane with a molecular weight of 5000 (vinyl content 0.1 mol%) and 0.05 wt% chloroplatinic acid catalyst, and use ultrasonic dispersion for 30 minutes to evenly suspend the microcapsules to obtain an electroplating solution.

[0071] Step 2: First, deposit a silver base coating with a thickness of 0.8 μm by magnetron sputtering process, control the purity to 99.92%, and the surface roughness Ra ≤ 0.1 μm. Subsequently, form a transition layer on the silver layer by electrophoresis-electroplating collaborative process: Disperse SiO 2 nanoparticles with a particle size of 5 nm and BN with a sheet thickness of 50 nm in the electroplating solution obtained in Step 1 at a volume ratio of 2.5:1, apply an electric field strength of 15 V / cm for electrophoresis deposition for 30 seconds, and then switch to the electroplating mode to deposit a Ni-SiO 2 / BN composite layer with a thickness of 0.5 μm at a current density of 3 A / dm². The total volume of SiO 2 and BN in this transition layer accounts for 20% of the transition layer. Then electroplate a nickel main functional layer with a thickness of 2.5 μm on the transition layer, maintain the plating solution temperature at 50 °C, and the pH value at 4.2. Finally, form a 15-μm-thick silicone / BN encapsulation layer on the surface by spraying process, where the mass ratio of BN is 40%, and complete the preparation of the encapsulation layer after curing at 120 °C.

[0072] Step 3: Use a 355-nm ultraviolet laser to perform micro-area activation on the pin area, set the power density at 9 J / cm², the frequency at 20 kHz, the spot diameter at 5 μm, and control the positioning accuracy within the range of ±2 μm. Immediately after activation, perform pulse electroplating deposition based on the electroplating solution obtained in Step 1, with the forward current of 4.5 A / dm² (pulse width 10 ms) and the reverse current of 1 A / dm² (pulse width 2 ms) alternating, and the total deposition time is 15 minutes. After completion of deposition, transfer the workpiece to a nitrogen protection chamber (oxygen content 48 ppm), and use a 365-nm LED array light source to perform in-situ ultraviolet curing at a light intensity of 50 mW / cm² for 120 seconds.

[0073] Comparative Example 1

[0074] This comparative example provides an improved electroplating process for optoelectronic coupler encapsulation. The method includes the following steps: Step 1: First, deposit a silver base coating with a thickness of 0.5 μm by magnetron sputtering process, control the purity to 99.92%, and the surface roughness Ra ≤ 0.1 μm. Subsequently, form a transition layer on the silver layer by electrophoresis-electroplating collaborative process: Disperse SiO 2 nanoparticles with a particle size of 5 nm in a nickel sulfamate plating solution with a concentration of 400 g / L (without setting BN sheets), apply an electric field strength of 15 V / cm for electrophoresis deposition for 30 seconds, and then switch to the electroplating mode to deposit a Ni-SiO 2Layer. Then, a nickel main functional layer with a thickness of 4.0 μm is electroplated on the transition layer, and the bath temperature is maintained at 50 °C and the pH value is 4.2. Finally, a silicone oxide encapsulation layer with a thickness of 20 μm is formed on the surface by spraying process, and the encapsulation layer preparation is completed after curing at 120 °C.

[0075] Step 2: Use a 405 nm ultraviolet laser to micro-activate the pin area, set the power density at 8 J / cm², the frequency at 20 kHz, the spot diameter at 5 μm, and control the positioning accuracy within the range of ±2 μm. Immediately after activation, pulse electroplating deposition is carried out based on a nickel sulfamate bath with a concentration of 400 g / L, with the forward current of 3 A / dm² (pulse width 10 ms) and the reverse current of 1 A / dm² (pulse width 2 ms) alternating, and the total deposition time is 15 minutes. After the deposition is completed, the workpiece is transferred to a nitrogen protection chamber, and in an air environment, in-situ ultraviolet curing is carried out using a 365 nm LED array light source with a light intensity of 50 mW / cm² for 120 seconds.

[0076] Comparative Example 2

[0077] This comparative example provides an improved electroplating process for optoelectronic coupler packaging, and the method includes the following steps: Step 1: Microcapsules with a wall material of polyurea formaldehyde (thickness 300 nm, Tg = 85 °C) and a core material containing vinyl siloxane with a molecular weight of 5000 (vinyl content 0.1 mol%) and 0.2 wt% chloroplatinic acid catalyst are added to a nickel sulfate bath with a concentration of 400 g / L at a volume ratio of 15%, and ultrasonic dispersion is carried out for 30 minutes to make the microcapsules evenly suspended, obtaining an electroplating bath.

[0078] Step 2: First, deposit a silver base coating with a thickness of 1.0 μm by magnetron sputtering process, control the purity at 99.5%, and the surface roughness Ra ≤ 0.1 μm. Subsequently, a transition layer is formed on the silver layer by an electrophoresis-electroplating synergistic process: SiO 2 nanoparticles with a particle size of 5 nm and BN with a sheet thickness of 50 nm are dispersed in the electroplating bath obtained in Step 1 at a volume ratio of 1:1, an electric field intensity of 15 V / cm is applied for electrophoresis deposition for 30 seconds, and then switched to the electroplating mode to deposit a Ni-SiO 2 / BN composite layer with a thickness of 0.5 μm at a current density of 3 A / dm². The total volume of SiO 2 and BN in this transition layer accounts for 20% of the transition layer. Then, a nickel main functional layer with a thickness of 3.0 μm is electroplated on the transition layer, and the bath temperature is maintained at 50 °C and the pH value is 4.2. Finally, a silicone oxide / BN encapsulation layer with a thickness of 30 μm is formed on the surface by spraying process, where the mass ratio of BN is 40%, and the encapsulation layer preparation is completed after curing at 120 °C.

[0079] Step 3: Use a 355 nm ultraviolet laser to perform micro-area activation on the pin area, set the power density to 8 J / cm², the frequency to 20 kHz, and the spot diameter to 5 μm, without controlling the positioning accuracy. Immediately after activation, perform pulse electroplating deposition based on the electroplating solution obtained in Step 1, with only a forward current of 5 A / dm² (pulse width 10 ms) and no reverse current, and the total deposition time is 15 minutes. After completion of the deposition, transfer the workpiece to a nitrogen protection chamber (oxygen content 45 ppm), and use a 385 nm LED array light source to perform in-situ ultraviolet curing at a light intensity of 50 mW / cm² for 120 seconds.

[0080] Comparative Example 3

[0081] 1. Porosity test: According to ASTM B276 standard, use a metallurgical microscope (1000×) to count the number of pores on the surface of the coating within a unit area (1 cm²).

[0082] 2. High-frequency loss test: Use a vector network analyzer (Keysight N5227B) to measure the signal transmission loss (dB value) at a frequency of 10 GHz.

[0083] 3. Contact resistance test: Use the four-probe method (ASTM B539) to measure the resistance change rate after aging for 1000 hours in an 85°C / 85% RH environment.

[0084] 4. Repair rate evaluation: Measure the volume filling rate of a prefabricated scratch (depth 5 μm) after 24 hours of repair in an 85°C environment through a laser confocal microscope (Olympus LEXT OLS5000).

[0085] 5. Salt spray resistance test: Conduct a neutral salt spray test according to ISO 9227 standard, and observe the proportion of the corroded area after 3000 hours.

[0086] 6. Thermal cycle cracking detection: According to IPC-TM-650 2.6.8, the temperature cycle conditions are -55°C (30 min) → 150°C (30 min), and the heating and cooling rate is 10°C / min; after 1500 cycles, use a scanning acoustic microscope (SAM) to detect the proportion of the delaminated area at the interface between the coating and the substrate.

[0087] The experimental results are shown in Table 1: Table 1 Comparison table of key performance indicators of examples and comparative examples

[0088] Analysis of experimental results The test data of Examples 1-3 show that the nano-gradient composite coating structure has high purity (≥99.9%) of the silver substrate and SiO in the transition layer 2The 3:1 volume ratio design of SiO₂ / BN effectively reduces the interfacial contact resistance (change rate < 12%), and its porosity is controlled below 3 per cm², significantly better than 8.7 per cm² of Comparative Example 1. This result is due to the gradient distribution of nanoparticles formed by the electrophoresis-electroplating synergistic process in the transition layer. Through the filling effect of SiO₂ 2 nanoparticles and the slip mechanism of BN lamellae, the expansion of internal defects in the coating is inhibited. In the photoinduced selective electroplating process, the precise positioning of the 355 nm ultraviolet laser (±2 μm) and the asymmetric current parameters of pulse electroplating (forward 5 A / dm² / reverse 1 A / dm²) act synergistically to make the surface roughness Ra of the coating ≤ 0.2 μm, thereby reducing the high-frequency signal loss to below 0.85 dB. In Comparative Example 1, due to the absence of a BN transition layer and ordinary laser parameters, the loss is as high as 2.6 dB.

[0089] The self-healing microcapsule system shows significant reliability advantages in the examples. The matching design of a volume ratio of 15 ± 2% and a wall thickness of 200 ± 50 nm enables the microcapsules to effectively release the repair agent when the coating is damaged, with a repair rate of over 87%. In Comparative Example 1, due to the complete absence of microcapsules, the repair rate is zero; while in Comparative Example 2, due to the wall thickness increasing to 300 nm and an excessive catalyst (0.2 wt%), the rupture threshold of the microcapsules increases, and the repair rate is only 35%. At the same time, the excessive catalyst causes local electrochemical corrosion, and the salt spray corrosion area reaches 5.8%.

[0090] In addition, the pure silicone oxide encapsulation layer of Comparative Example 1 (thermal conductivity 0.2 W / (m·K)) cannot effectively dissipate thermal stress, resulting in local temperature accumulation; at the same time, without adding a microcapsule system, the internal microcracks of the coating cannot self-heal, and finally, due to thermal stress concentration, complete cracking occurs after 100 thermal cycles. The coating of Comparative Example 2 electroplated with ordinary nickel sulfate (HV 300) results in too low hardness of the main functional layer to resist mechanical deformation during thermal cycling; the over-standard wall thickness of the microcapsules (300 nm) and excessive catalyst (0.2 wt%) further exacerbate interfacial corrosion, and finally, a cracking rate of 45% appears after 150 cycles.

[0091] Generally speaking, the process parameters defined in this application, through the synergistic effect of multi-scale structure design (nano-gradient coating), precise energy field regulation (photoinduced deposition), and dynamic repair mechanism (microcapsule system), systematically solve the technical contradiction that it is difficult to balance high-frequency loss, environmental aging, and mechanical reliability in traditional electroplating processes. The comparative example data verifies in reverse that the absence or out-of-range adjustment of any technical feature will lead to a significant deterioration in performance.

[0092] It should be noted that in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0093] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. An improved photoelectric coupler packaging electroplating process, characterized in that: The following steps are involved: S10, dispersing self-repairing microcapsules into an electroplating solution, wherein the microcapsules comprise a wall material and a core material, and the core material comprises vinyl siloxane and a chloroplatinic acid catalyst; S20, sequentially forming a nano-gradient composite coating structure on the surface of the substrate, wherein the composite coating structure includes a base layer, a transition layer, a main functional layer and an encapsulation layer; S30, using a light-induced selective electroplating process for micro-area deposition, including laser micro-area activation, pulse electroplating deposition and in-situ UV curing.

2. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: In the step S20, the base layer is a silver deposition layer with a thickness of 1.0±0.2 μm and a purity of ≥99.9%; the transition layer is a composite layer of Ni-SiO2 and BN with a thickness of 0.5 μm, wherein the total volume of SiO2 and BN accounts for 15-25% of the transition layer, and the volume ratio of SiO2 to BN in the transition layer is 3:

1.

3. The improved optocoupler packaging electroplating process according to claim 2, characterized in that: The particle size of SiO2 in the transition layer is 5 nm, the thickness of the BN layer is 50 nm, and the transition layer is formed by an electrophoresis-electroplating collaborative process.

4. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The main functional layer in step S20 is obtained by electroplating based on a nickel sulfamate electroplating solution, the thickness of the main functional layer is 3.0±0.5 μm, and the Vickers hardness of the main functional layer is HV 520±30.

5. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The encapsulation layer in step S20 is a composite layer of siloxane and BN, with a thickness of 20±5 μm and a thermal conductivity of ≥1.8 W / (m·K).

6. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: In step S30, the area of ​​the micro-area deposition is the pin area of ​​the photoelectric coupler, and the laser micro-area activation uses an ultraviolet laser with a wavelength of 355nm, a power density of 8J / cm², and a frequency of 20kHz.

7. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The current density of the forward current of the pulse electroplating deposition in step S30 is 5A / dm² and the pulse width is 10ms, and the current density of the reverse current is 1A / dm² and the pulse width is 2ms.

8. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The in-situ UV curing in step S30 is performed in a nitrogen atmosphere with an oxygen content of <50 ppm, using a 365 nm LED array light source with a light intensity of 50 mW / cm².

9. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The volume proportion of the self-repairing microcapsules in step S10 is 15±2%, the wall material is polyurea formaldehyde, the thickness of the wall material is 200±50 nm, and the glass transition temperature of the wall material is 85°C.

10. The improved optocoupler packaging electroplating process according to claim 1, characterized in that: The molecular weight of the vinyl siloxane in the core material is 5000, the vinyl content is 0.1 mol%, and the added amount of chloroplatinic acid catalyst is 0.05 wt%.

Images