Mobile phone PCR shell and processing method thereof

Abstract

The invention discloses a mobile phone PCR shell and a processing method thereof.The processing method comprises the steps that polycarbonate, boron nitride nanosheets and carbon fibers are mixed according to a preset proportion, gradient dispersion blending and directional shearing are conducted through a double-screw extruder, and composite material master batches with a three-dimensional heat conduction network are prepared; injecting into a mold in which a soluble salt core mold is preset, and carrying out injection molding to form a shell base body containing the bionic micro-channel; a hexagonal honeycomb bulge array is processed on the outer surface of a shell substrate by adopting a laser etching process, a branch angle of a micro-channel is optimized through heat-flow coupling simulation based on heat source distribution data of a heating element, a corrected micro-channel path design is generated, and the layout of a core mold is adjusted according to the corrected micro-channel path design. According to the invention, the heat conductivity coefficient of the shell is increased, the heat dissipation area is increased, the surface temperature is effectively reduced, and the double advantages of heat dissipation efficiency and process stability of the PCR shell are realized.

Description

Technical Field

[0001] The present invention relates to the field of mobile phone accessories, and particularly to a mobile phone PCR housing and a processing method thereof. Background Art

[0002] With the popularization of 5G communication technology and the rapid development of folding screen mobile phones, mobile devices have put forward higher requirements for housing materials, which need to meet the requirements of lightweight, impact resistance and efficient heat dissipation at the same time. Polycarbonate resin (PCR) housing has become the mainstream mobile phone shell material due to its excellent mechanical properties and cost advantages. However, in high-power consumption scenarios of 5G chips (such as games and video rendering), its inherent low thermal conductivity leads to heat accumulation, causing serious problems such as device frequency reduction and accelerated battery aging, which restricts the performance release of high-end intelligent terminals and the improvement of user experience.

[0003] Existing technologies and defects: Most of the existing PCR housing processing adopts single filler blending modification (such as adding alumina or graphene flakes). Although the thermal conductivity of the matrix can be increased to 0.5-0.8 W / m·K, due to the uneven dispersion and random orientation of the fillers, a continuous heat conduction path cannot be formed, resulting in the heat conduction efficiency still being difficult to match the heat source requirements above 5W. In addition, some solutions attempt to externally attach metal heat sinks or add fans, but sacrifice the thin and light characteristics of the housing.

[0004] The core pain point lies in that the traditional process only relies on the adjustment of material components, lacks the active control of the design of the heat conduction network structure and the heat flow path, resulting in the bottleneck of improving the thermal conductivity and being unable to fundamentally solve the problem of housing heat dissipation failure in high-power consumption scenarios. Summary of the Invention

[0005] The purpose of the present invention is to provide a mobile phone PCR housing and a processing method thereof to solve the above technical problems.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: A processing method for a mobile phone PCR housing includes the following steps: S1, mixing polycarbonate, boron nitride nanosheets and carbon fibers in a preset ratio, and performing gradient dispersion blending and directional shearing through a twin-screw extruder to prepare a composite masterbatch with a three-dimensional heat conduction network; S2, injecting the composite masterbatch into a mold with a pre-set soluble salt core mold for injection molding, and forming a housing matrix with bionic microchannels inside after dissolving and removing the salt core; S3, using a laser etching process to process a hexagonal honeycomb protrusion array on the outer surface of the housing matrix, and realizing the formation of microstructures with a predetermined depth by controlling the laser power and scanning speed; S4, based on the heat source distribution data of the heating element, optimizing the branch angle of the microchannel through thermal-fluid coupling simulation to generate a revised microchannel path design; S5, adjusting the layout of the soluble salt core mold according to the modified microchannel path design, and re-injection molding to form an optimized shell microchannel structure to obtain a PCR shell finished product.

[0007] Optionally, the ratio of the polycarbonate, the boron nitride nanosheets and the carbon fiber is 70:20:10, wherein the carbon fiber is chopped carbon fiber.

[0008] Optionally, step S1 includes the following steps: S11, placing the polycarbonate particles in a vacuum drying oven and performing a dehydration treatment at 100° C. for 4 hours to obtain a dry polycarbonate base material; S12, mixing boron nitride nanosheets and carbon fiber chopped strands in a mass ratio of 2:1, adding them to anhydrous ethanol for ultrasonic dispersion for 30 minutes to form a uniform BNNS-CF suspension, and then preparing a composite thermal conductive filler powder by centrifugal spray drying; S13, feeding the dried polycarbonate base material and the composite thermal conductive filler powder into a segmented temperature-controlled hopper of a twin-screw extruder at a mass ratio of 70:30, wherein the temperature of the front screw zone is set to 180° C., and the temperature gradient of the rear screw zone is increased to 210° C.; S14, during the twin-screw extrusion process, the front section uses a low shear rate to melt the polycarbonate and initially wrap the filler, and the rear section switches to a high shear rate and a combination of reverse screw elements to force the boron nitride nanosheets to be oriented along the extrusion direction. At the same time, the carbon fibers are induced by the shear force to form a cross-layer overlapping network to construct a three-dimensional thermal conductive network; S15, the extruded composite material melt is subjected to water-cooling and strand-cutting to obtain a composite material masterbatch having a three-dimensional thermal conductive network and a target axial thermal conductivity coefficient.

[0009] Optionally, step S2 includes the following steps: S21, presetting the soluble salt core mold into a bionic leaf vein-like branch structure, wherein the soluble salt core mold is formed into a continuous network skeleton of a preset size by 3D printing from NaCl powder, and fixed to the inner surface of the mold cavity by a water-soluble adhesive; S22, heating the composite masterbatch to a molten state and then injecting it into a mold, using a segmented pressure-maintaining injection molding strategy: in the initial stage, the cavity gap is filled with a low pressure of 50 MPa, and then switched to a high pressure of 80 MPa to compact the contact interface between the molten body and the soluble salt core mold, and after cooling and solidification, a shell preform covering the salt core is formed; S23, taking the shell preform out of the mold, immersing it in 40° C. deionized water, and oscillating it with 120 kHz ultrasonic waves for 30 minutes to dissolve and discharge the soluble salt core mold to form a through-type bionic leaf vein microchannel; S24. Perform vacuum drying treatment on the housing substrate after removing the salt core to control the residual moisture and complete the preparation of the housing substrate with a three-dimensional heat dissipation path.

[0010] Optionally, step S3 includes the following steps: S31. Perform plasma cleaning treatment on the outer surface of the housing substrate. Treat the surface with argon plasma for 60 seconds to remove residual contaminants and improve the laser absorption rate. S32. Import the hexagonal honeycomb array design parameters into the laser galvanometer control system to generate a spiral progressive scanning path that matches the honeycomb cell size, and match the pulse interval and the focused spot diameter. S33. Start etching with a fiber laser at a base power of 20W. Increase the power to 25W and reduce the scanning speed to 400mm / s in the edge area of the honeycomb cell to form a reinforcing groove with a first depth, and maintain the power at 18W and the speed at 600mm / s in the central area to form a shallow concave surface with a second depth. S34. Synchronously introduce a nitrogen curtain during the laser etching process. The gas flow rate is 15L / min, and it blows the molten products at an angle of 45° to the laser beam to inhibit surface carbonization and improve the perpendicularity of the side walls of the hexagonal protrusions.

[0011] Optionally, after step S34, the following steps are further included: S35. Real-time monitor the forming depth of the honeycomb structure through a confocal microscope. When the height deviation of the detection unit exceeds the allowable threshold, dynamically adjust the laser power compensation coefficient for secondary precision etching. S36. Anneal the etched housing in an incubator at 120°C for 2 hours to eliminate the local residual stress caused by laser processing and obtain a preliminary housing.

[0012] Optionally, step S4 includes the following steps: S41. Integrate the target main board with the preliminary housing. Collect the real-time temperature field distribution data of the target main board under the preset standard power consumption through an infrared thermal imager, and extract the peak coordinates of the heat flux density in the projection area of the heating element by combining current density analysis. S42. Establish a three-dimensional thermal-fluid coupling simulation model of the housing based on the peak coordinates of the heat flux density. Set the microchannel branch angle as the initial variable, and set the chip junction temperature ≤ 85°C and the housing surface temperature ≤ 45°C as the constraint conditions. S43. Use a hybrid iteration of the genetic algorithm and the finite element method to calculate the thermal resistance gradient distribution at different branch angles, and screen the optimized angle range that improves the uniformity of heat flow diffusion. S44. Reconstruct the bionic vein-like microchannel topological structure according to the optimized angle range to generate a corrected path data packet with a gradient branch density, where the channel spacing in the high heat flux area is reduced to the first width and that in the low heat flux area is expanded to the second width. S45. Import the corrected path data packet into the hydrodynamic verification module to simulate the flow velocity field and temperature field under transient thermal shock (greater than the preset standard power consumption). When the detected local temperature difference > 2 °C, reverse correct the channel branch curvature radius to the preset range to generate the corrected microchannel path design.

[0013] Optionally, step S4 includes the following steps: S51. According to the corrected microchannel path design data, adjust the structural parameters of the 3D printed soluble salt core mold, lock the branch angle to the optimized angle range, update the channel spacing to between the first width and the second width according to the heat flux density gradient, and increase the density of the support skeleton of the salt core mold in the high heat area. S52. Assemble the optimized salt core mold into the injection mold, adopt a segmented pressure holding injection strategy, and ultrasonically dissolve the salt core mold residue on the shell preform after injection to remove the salt core mold residue on the shell to form an optimized shell matrix by injection molding. S53. Integrate a hexagonal honeycomb protrusion array and micro-structure forming on the optimized shell matrix to obtain the finished shell.

[0014] Optionally, after step S53, it further includes: S54. Scan the surface temperature field of the shell with an infrared thermal imager, detect the heat flux uniformity in the microchannel area under the preset standard power consumption simulation heat source. If the local temperature difference > 1.5 °C, mark it as a defective area and trigger the secondary compensation algorithm for the support density of the salt core mold. S55. Perform a coating and film covering treatment on the qualified finished shell, spray a graphene heat conduction layer on the inner wall of the microchannel, and deposit a surface film layer on the outer surface to complete the preparation of the PCR shell finished product.

[0015] The present invention also provides a mobile phone PCR shell, which is obtained by using the above-mentioned processing method for the mobile phone PCR shell. The PCR shell includes: A shell matrix, the inside of which is uniformly provided with a three-dimensional heat conduction network formed by polycarbonate base material dispersed with boron nitride nanosheets and carbon fibers. A bionic microchannel layer, embedded inside the shell matrix, including continuous flow channels with a preset branch angle, where the channel spacing in the high heat flux area is the first width. A protrusion array, formed on the outer surface of the matrix, and the protrusion array is correspondingly provided with micro-structures. A graphene heat conduction coating, covering the inner wall of the microchannel.

[0016] Compared with the prior art, the present invention has the following beneficial effects: First, polycarbonate, boron nitride nanosheets and carbon fibers are mixed in a preset ratio, and a three-dimensional thermally conductive network composite masterbatch is prepared by gradient dispersion blending and directional shearing; then the masterbatch is injected into a mold containing a soluble salt core mold for injection molding, and the salt core is dissolved to form a bionic microchannel shell matrix; then a hexagonal honeycomb array is machined on the surface of the matrix by laser etching to expand the heat dissipation area; based on the heat source distribution data of the heating element, the microchannel branch angle is optimized by thermal-fluid coupling simulation and a corrected path design is generated; after adjusting the layout of the salt core mold and re-injecting, a finished shell with an optimized microchannel structure is obtained; this method constructs a three-dimensional thermally conductive network through gradient dispersion and directional shearing, improves the thermal conductivity of the shell, and the synergistic design of the bionic microchannel and the honeycomb array increases the heat dissipation area and effectively reduces the surface temperature; the simulation optimization based on the heat source data realizes precise thermal path control, combined with the closed-loop adjustment process of the soluble salt core mold, solving the dual problems of low heat dissipation efficiency and poor process stability of traditional PCR shells. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] The structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have technical substance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0019] Figure 1 One of the flow diagrams of the processing method of the mobile phone PCR shell in Embodiment 1; Figure 2 Another flow diagram of the processing method of the mobile phone PCR shell in Embodiment 1; Figure 3 One of the schematic diagrams of the PCR shell in Embodiment 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the object, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be intermediate components present at the same time.

[0022] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments.

[0023] Embodiment 1: Combined with Figure 1 and Figure 2 As shown, the embodiment of the present invention provides a processing method for a mobile phone PCR housing, including the following steps: S1, mixing polycarbonate, boron nitride nanosheets, and carbon fibers in a preset ratio, and performing gradient dispersion blending and orientation shearing through a twin-screw extruder to prepare a composite masterbatch with a three-dimensional heat conduction network; Through the compound combination of polycarbonate, boron nitride nanosheets, and carbon fibers, the interlayer heat conduction advantage of boron nitride and the high axial heat conduction characteristics of carbon fibers are complementary. The gradient dispersion process (gradually adjusting the shear rate and temperature) of the twin-screw extruder can improve the agglomeration problem caused by the density difference of traditional single fillers, and the orientation shearing promotes the orderly arrangement of carbon fibers along the extrusion direction, and cooperates with the planar distribution of boron nitride nanosheets to form a longitudinal-transverse cross-linked three-dimensional heat conduction network. This structure breaks through the isotropic heat conduction limitation of traditional randomly dispersed fillers and provides a physical channel for directional heat conduction.

[0024] S2, injecting the composite masterbatch into a mold with a preset soluble salt core mold for injection molding, and dissolving and removing the salt core to form a housing matrix with bionic microchannels inside; A soluble salt core mold is used to replace the traditional metal insert. After dissolution and removal, a through-type microchannel network is formed. The bionic design mimics the branching structure of plant veins. Its multi-level fractal characteristics can reduce the fluid flow resistance and enhance the convective heat dissipation by increasing the specific surface area. On the premise of ensuring the overall thinness of the shell, this process realizes the integrated molding of the active heat dissipation structure and the shell, avoiding the extra volume brought by external heat sinks.

[0025] S3. An array of hexagonal honeycomb protrusions is machined on the outer surface of the shell substrate by laser etching. The microstructures with a predetermined depth are formed by controlling the laser power and scanning speed. The hexagonal honeycomb structure has the optimal space filling efficiency and mechanical properties in nature. Its periodic arrangement enhances air turbulence through boundary layer perturbation. Laser etching realizes the formation of micron-scale structures by precisely controlling the energy density (power) and action time (scanning speed), avoiding the mechanical stress damage to the substrate caused by traditional stamping processes. The surface protrusion array and the internal microchannels form a "three-dimensional heat dissipation" synergy, improving the heat exchange efficiency by increasing the effective heat dissipation area and optimizing the air flow path.

[0026] S4. Based on the heat source distribution data of the heating element, the branching angles of the microchannels are optimized through thermal-fluid coupling simulation to generate a corrected microchannel path design. A three-dimensional heat transfer model is established based on a specific heat source distribution (such as the heat concentration area of the semiconductor module of a PCR instrument). The flow characteristics and temperature field distribution of the cooling medium (air / liquid) in the microchannels are simulated by computational fluid dynamics (CFD). The branching angles are mainly optimized to balance the pressure drop loss and heat exchange efficiency, making the microchannel topology structure adapt to the actual heat flux density distribution and breaking through the blindness of empirical design. This data-driven method realizes the transformation from homogeneous heat dissipation to targeted guidance of local hot spots.

[0027] S5. According to the corrected microchannel path design, the layout of the soluble salt core mold is adjusted, and re-injection molding is carried out to form an optimized microchannel structure of the shell, so as to obtain the finished PCR shell.

[0028] The simulation results are fed back to the topological reconstruction of the soluble salt core mold, and the structural parameters are accurately corrected through secondary injection molding. This closed-loop adjustment mechanism solves the problems of long cycle and high cost of the traditional trial-and-error method, ensuring the spatial matching of parameters such as the microchannel branch density and pipe diameter with the heat source distribution. At the same time, through process stability verification (such as the correlation analysis of injection pressure - core mold deformation), the risk of microchannel molding defects caused by the disturbance of the melt flow front is reduced.

[0029] The working principle of the present invention is as follows: First, polycarbonate, boron nitride nanosheets, and carbon fibers are mixed in a preset ratio, and a three-dimensional thermally conductive network composite masterbatch is prepared by gradient dispersion blending and directional shearing; then the masterbatch is injected into a mold containing a soluble salt core mold for injection molding, and the salt core is dissolved to form a bionic microchannel shell matrix; then a hexagonal honeycomb array is machined on the surface of the matrix by laser etching to expand the heat dissipation area; based on the heat source distribution data of the heating element, the microchannel branch angle is optimized by thermal-fluid coupling simulation and a corrected path design is generated; after adjusting the layout of the salt core mold and re-injecting, a finished shell with an optimized microchannel structure is obtained; this method constructs a three-dimensional thermally conductive network through gradient dispersion and directional shearing to improve the thermal conductivity of the shell, and the collaborative design of the bionic microchannel and the honeycomb array increases the heat dissipation area and effectively reduces the surface temperature; the simulation optimization based on the heat source data realizes precise thermal path control, combined with the closed-loop adjustment process of the soluble salt core mold, solving the double problems of low heat dissipation efficiency and poor process stability of traditional PCR shells.

[0030] In this embodiment, specifically, the ratio of polycarbonate, boron nitride nanosheets, and carbon fibers is 70:20:10, and the carbon fiber is short carbon fiber filaments.

[0031] In this embodiment, specifically, step S1 includes the following steps: S11, Place the polycarbonate particles in a vacuum drying oven and dehydrate them at 100 °C for 4 hours to obtain a dry polycarbonate base material with a water content < 0.02%; The polycarbonate particles are vacuum dried at 100 °C for 4 hours. By controlling the temperature below the glass transition temperature of polycarbonate (about 145 °C), thermal deformation is avoided, and at the same time, the vacuum environment is used to accelerate the evaporation of water. This step reduces the water content to < 0.02%, effectively eliminating the risk of melt foaming or hydrolysis degradation caused by residual water in subsequent processing, and ensuring the thermal stability and mechanical properties of the matrix material. Compared with the conventional drying process (such as 80 °C / 6 hours), this parameter achieves a balance between efficiency and safety.

[0032] S12, Mix the boron nitride nanosheets and short carbon fiber filaments in a mass ratio of 2:1, add them to anhydrous ethanol and ultrasonically disperse for 30 minutes to form a uniform BNNS-CF suspension, and then prepare composite thermally conductive filler powder by centrifugal spray drying; Boron nitride nanosheets (BNNS) and short carbon fiber shreds (CF) are mixed at a mass ratio of 2:1, and the low surface tension property of anhydrous ethanol is utilized to promote the wetting of the fillers. Ultrasonic dispersion for 30 minutes exfoliates the aggregated boron nitride sheets through cavitation effect while avoiding excessive breakage of carbon fibers. The centrifugal spray drying technique quickly converts the suspension into powder, preventing the re-aggregation of fillers due to gravitational sedimentation. This process breaks through the dispersion limit of traditional mechanical stirring, realizes the uniform composite of nano-micron scale fillers, and lays a foundation for the subsequent three-dimensional network construction.

[0033] S13, The dried polycarbonate base material and the composite thermal conductive filler powder are put into the segmented temperature-controlled hopper of the twin-screw extruder at a mass ratio of 70:30. The temperature of the front screw zone is set at 180 °C, and the temperature gradient of the rear screw zone rises to 210 °C. The polycarbonate base material and the composite filler are put into the twin-screw extruder at a ratio of 70:30. The front screw zone is set at 180 °C (slightly higher than the melting point of polycarbonate) to ensure that the matrix is fully melted and initially wraps the filler. The temperature is gradually increased to 210 °C in the rear section to reduce the melt viscosity and improve the filler fluidity. The segmented temperature control avoids the oxidation of carbon fibers or the thermal decomposition of polycarbonate caused by high temperature at one time. At the same time, the gradient change of the melt viscosity promotes the directional migration of the filler in the shear field and optimizes the dispersion uniformity.

[0034] S14, During the twin-screw extrusion process, the polycarbonate is melted and initially wraps the filler at a low shear rate (50 rpm) in the front section. In the rear section, it is switched to a high shear rate (200 rpm) combined with reverse-thread elements, forcing the boron nitride nanosheets to be oriented along the extrusion direction. At the same time, the carbon fibers are induced by the shear force to form an interlayer lap network to construct a three-dimensional thermal conductive network. The low shear rate (50 rpm) in the front section reduces the mechanical damage to the fillers and allows the melt to slowly infiltrate the filler surface. In the rear section, it is switched to a high shear rate (200 rpm) combined with reverse-thread elements. The strong shear flow field is used to force the boron nitride nanosheets to be oriented along the extrusion direction. At the same time, the tensile flow field generated by the reverse threads induces the carbon fibers to interlayer lap. This dynamic regulation strategy breaks through the limitations of traditional single-shear mode and realizes the three-dimensional interpenetrating structure of "plane orientation - axial bridging" of the fillers through the synergistic action of shear force and flow field, significantly improving the anisotropic thermal conductivity of the composite material.

[0035] S15, The extruded composite material melt is cooled by water, drawn into strands, and pelletized to obtain the composite material masterbatch with a three-dimensional thermal conductive network of the target axial thermal conductivity.

[0036] The extruded melt is pelletized by water-cooling and stranding, and the orientation structure formed by the filler in the molten state is locked by rapid cooling to prevent the filler from rebounding or re-agglomerating due to slow cooling. Compared with air cooling, the water cooling process can shorten the molding cycle, and at the same time, the crystallinity of the masterbatch can be adjusted by controlling the cooling rate (such as water temperature and pulling speed) to avoid brittle fracture caused by internal stress concentration. This step ensures the structural integrity of the three-dimensional thermal conductive network in the solid masterbatch, providing stable raw materials for subsequent injection molding.

[0037] In this embodiment, it is specifically described that step S2 includes the following steps: S21, presetting the soluble salt core mold into a bionic leaf vein-like branch structure, wherein the soluble salt core mold is formed by 3D printing from NaCl powder into a continuous network skeleton with a preset size of 0.2 mm in width and 0.5 mm in depth, and fixed to the inner surface of the mold cavity by a water-soluble adhesive; NaCl powder is molded into a bionic leaf vein-like branch structure (width 0.2mm, depth 0.5mm) through 3D printing technology, and its high water solubility and easy molding properties are used to achieve accurate replication of complex microchannels. The water-soluble binder fixes the core mold to the mold cavity surface to ensure that the salt core does not move or deform during the injection molding process.

[0038] S22, the composite masterbatch is heated to a molten state and then injected into the mold, and a segmented pressure-maintaining injection molding strategy is adopted: in the initial stage, the cavity gap is filled with a low pressure of 50MPa, and then the contact interface between the molten body and the soluble salt core mold is compacted with a high pressure of 80MPa, and after cooling and solidification, a shell preform covering the salt core is formed; In the initial stage, 50MPa low-pressure filling is used to avoid the fracture of the salt core skeleton caused by the impact of high-speed melt; after switching to 80MPa high-pressure compaction, the interface pressure between the melt and the salt core is increased, the interface porosity is reduced and the fidelity of the melt's replication of the salt core surface details is enhanced. The segmented pressure holding strategy combined with the shear-thinning characteristics of the polycarbonate melt ensures the integrity of the salt core structure while achieving full filling of the micron-level grooves by the melt to prevent channel collapse or local blockage.

[0039] S23, taking out the mold of the shell preform, immersing it in 40° C. deionized water, and oscillating it with 120 kHz ultrasonic waves for 30 minutes to dissolve and discharge the soluble salt core mold to form a through-type bionic leaf vein microchannel; Deionized water at 40°C (close to the inflection point of the NaCl solubility curve) is used to accelerate the dissolution of the salt core, and the cavitation effect and microjet effect of 120kHz ultrasound are combined to completely remove the residual salt particles in the narrow microchannel with a depth-to-width ratio of 2.5:1. Compared with static immersion (usually taking several hours), ultrasound assistance compresses the dissolution time to 30 minutes, and high-frequency oscillation can peel off the attachments on the inner wall of the channel, ensuring the smoothness and penetration of the inner surface of the microchannel.

[0040] S24. Perform vacuum drying treatment on the housing substrate after removing the salt core, control the residual moisture, and complete the preparation of the housing substrate with a three-dimensional heat dissipation path.

[0041] Vacuum drying accelerates water evaporation through a negative pressure environment, avoiding the risk of substrate deformation caused by capillary tension formed by residual water molecules in the microchannels. This process maintains the dimensional stability of the housing substrate while removing moisture, preventing the microchannel structure from cracking due to water vaporization during subsequent high-temperature processing (such as laser etching), and ensuring the functional reliability of the three-dimensional heat dissipation path.

[0042] In this embodiment, specifically, step S3 includes the following steps: S31. Perform plasma cleaning treatment on the outer surface of the housing substrate. Treat the surface with argon plasma for 60 seconds to remove residual contaminants and improve the laser absorption rate. Treat the housing surface with argon plasma. Remove the residual mold release agent or organic contaminants by bombarding with high-energy particles, and at the same time make the surface slightly roughened. As an inert gas, argon can avoid oxidation side reactions. The active substances generated by its ionization can break the weak bonds at the ends of polycarbonate molecular chains, expose polar groups to increase the surface energy. This treatment improves the absorption rate of the incident light for subsequent laser etching, reduces energy loss caused by surface reflection or contaminant shielding, and ensures the consistency of micro-structure forming.

[0043] S32. Import the hexagonal honeycomb array design parameters into the laser galvanometer control system, generate a spiral progressive scanning path based on the side length of 1 mm and height of 0.3 mm that matches the honeycomb cell size, and match the pulse interval and the focused spot diameter. Design a spiral progressive scanning path based on the hexagonal honeycomb cell size (side length 1 mm, height 0.3 mm), and dynamically adjust the laser focus position through the galvanometer system. The spiral path can reduce the thermal deformation of the material caused by local heat accumulation compared with one-way scanning. At the same time, matching the pulse interval (associated with the spot diameter) ensures the continuity of the etching trajectory. This parameter combination (such as spot diameter ≤ 50 μm) achieves the balance between the sharpness of the honeycomb cell edge and the flatness of the central area, avoiding the "edge melting - central depression" phenomenon caused by traditional equal-parameter scanning.

[0044] S33. Start etching with a fiber laser at a base power of 20 W. Increase the power to 25 W and reduce the scanning speed to 400 mm / s in the edge area of the honeycomb cell to form a reinforced groove with a first depth of 0.35 mm, and maintain a power of 18 W and a speed of 600 mm / s in the central area to form a shallow concave surface with a second depth of 0.25 mm. At the edge area of the honeycomb cell, a combination of 25W high power and 400mm / s low scanning speed is adopted. By extending the laser residence time, the material removal amount is enhanced, and a 0.35mm deep strengthening groove is formed to improve the shear resistance of the structure; in the central area, the power is reduced to 18W and the speed is increased to 600mm / s to reduce heat input to avoid excessive matrix ablation, and a 0.25mm shallow concave surface is formed to maintain the overall stiffness of the shell. This dynamic energy distribution strategy breaks through the limitations of uniform etching and realizes the formation of functional gradient microstructures.

[0045] S34. During the laser etching process, a nitrogen curtain is synchronously introduced. The air flow velocity is 15L / min, and it blows the molten products at an angle of 45° with the laser beam to inhibit surface carbonization and improve the perpendicularity of the side walls of the hexagonal protrusions.

[0046] A 45° inclined nitrogen curtain is introduced at a flow rate of 15L / min. The inert gas is used to isolate oxygen to inhibit the high-temperature carbonization of polycarbonate, and at the same time, the high-speed air flow takes away the molten splashes. The 45° incident angle design enables the air flow to scour along the etching direction, reducing the secondary adhesion of the melt on the side walls, and controlling the perpendicularity deviation of the side walls of the honeycomb protrusions within ±2°. Compared with the gas-free protection process, this parameter combination effectively reduces the surface roughness and avoids the increase of the thermal resistance of the subsequent heat dissipation contact surface.

[0047] S35. The forming depth of the honeycomb structure is monitored in real time through a confocal microscope. When the height deviation of the detection unit exceeds the allowable threshold, the laser power compensation coefficient is dynamically adjusted for secondary fine etching. The height of the honeycomb cell is monitored in real time by a confocal microscope. When the detected depth deviation exceeds the preset threshold (such as ±0.02mm), the laser power compensation coefficient is dynamically adjusted through a feedback algorithm. This closed-loop control mechanism overcomes the problem of inconsistent forming caused by material batch differences or laser fluctuations in traditional open-loop processing, ensures the geometric accuracy of the hexagonal array and the spatial uniformity of the heat dissipation performance, and reduces the secondary trimming process.

[0048] S36. The etched shell is annealed, kept in an incubator at 120°C for 2 hours to eliminate the local residual stress caused by laser processing and obtain a preliminary shell.

[0049] Annealing treatment is carried out at 120°C for 2 hours. This temperature is lower than the glass transition temperature of polycarbonate (about 145°C) but higher than the glass transition temperature gradient of the locally heated area (generated by laser etching). The processing residual stress is released through the relaxation of molecular chain segments. Compared with natural aging (several days to several weeks), constant-temperature annealing can quickly eliminate the microcrack tendency formed at the root of the microstructure due to rapid cooling, restore the toughness of the matrix and improve the dimensional stability of the shell during long-term use.

[0050] In this embodiment, specifically, step S4 includes the following steps: S41. Integrate the target main board with the preliminary housing, collect the real-time temperature field distribution data of the target main board at the preset standard power consumption through an infrared thermal imager, and extract the peak coordinates of the heat flux density in the projection area of the heating element by combining current density analysis. Non-contact acquisition of the temperature field distribution of the target main board at the standard power consumption through an infrared thermal imager, and positioning the peak coordinates of the heat flux density in the projection area of the heating element by combining current density analysis. This data fusion method breaks through the limitations of traditional single temperature detection, eliminates environmental interference noise through the current-temperature mapping relationship, and accurately identifies the geometric boundaries and intensity gradients of key heat sources such as chip packages and power supply modules, providing high-fidelity input conditions for subsequent simulation modeling.

[0051] S42. Based on the peak coordinates of the heat flux density, establish a three-dimensional thermal-fluid coupling simulation model of the housing, set the microchannel branch angle as the initial variable (45° - 65°), and set the chip junction temperature ≤ 85°C and the housing surface temperature ≤ 45°C as the constraint conditions. Based on the peak coordinates of the heat flux density, establish a three-dimensional simulation model, set the initial variable of the microchannel branch angle as 45° - 65°, and this range covers the hydrodynamic optimization interval of typical bionic fractal structures (such as the vein branch angle). The constraint conditions (chip junction temperature ≤ 85°C, housing surface temperature ≤ 45°C) comprehensively consider the reliability of semiconductor devices (Tjmax is usually 100 - 125°C) and the human contact safety threshold, ensuring a balance between performance and safety in the heat dissipation design.

[0052] S43. Adopt a hybrid iteration of the genetic algorithm and the finite element method to calculate the heat resistance gradient distribution at different branch angles, and screen the optimized angle interval that improves the uniformity of heat flow diffusion. Combine the global search of the genetic algorithm with the local refined calculation of the finite element method, and screen the branch angle that equalizes the heat resistance gradient distribution through multiple generations of iteration. The parallel computing characteristics of the genetic algorithm accelerate the exploration of the solution space, while the finite element method accurately quantifies the pressure drop-heat transfer relationship at a specific angle. This hybrid strategy breaks through the local extreme value trap of traditional single-objective optimization and realizes the multi-objective collaborative optimization of heat dissipation efficiency (minimization of heat resistance) and energy consumption cost (pump power constraint).

[0053] S44. Reconstruct the bionic vein-like microchannel topology structure according to the optimized angle interval, generate a modified path data packet with a gradient branch density, where the channel spacing in the high heat flux area is reduced to the first width of 1.2 mm, and the low heat flux area is expanded to the second width of 2.5 mm. Reconstruct the microchannel network according to the optimized angle range, reduce the channel spacing in the high heat flux area to 1.2 mm (enhance the local heat dissipation intensity), and expand it to 2.5 mm in the low heat flux area (reduce the flow resistance). The gradient branch density design simulates the adaptive transport mechanism of biological tissues. By matching the cross-sectional area of the channel with the heat flux density, it avoids the "over-design" problem of traditional uniformly distributed channels, reduces the redundancy of the cooling medium flow while ensuring the heat dissipation requirements.

[0054] S45, import the corrected path data packet into the hydrodynamic verification module, simulate the flow velocity field and temperature field under transient thermal shock (greater than the preset standard power consumption). When the detected local temperature difference > 2 °C, reverse correct the curvature radius of the channel branch to the preset range of 0.8 - 1.5 mm to generate the corrected microchannel path design.

[0055] Simulate transient thermal shock (such as short-term overclocking conditions) through hydrodynamics, detect the area where the local temperature difference > 2 °C and reverse correct the curvature radius of the channel branch to 0.8 - 1.5 mm. This curvature range is set based on the critical condition of fluid boundary layer separation, which can suppress the flow instability phenomenon caused by sudden changes in turbulence. The corrected smooth transition curvature reduces the eddy current energy loss, improves the update efficiency of the cooling medium in the high heat flux area, and ensures the heat dissipation robustness under extreme conditions.

[0056] In this embodiment, specifically, step S4 includes the following steps: S51, according to the corrected microchannel path design data, adjust the structural parameters of the 3D printed soluble salt core mold, lock the branch angle to the optimized angle range, update the channel spacing to between the first width and the second width according to the heat flux density gradient, and encrypt the support skeleton density of the salt core mold in the high heat area; Based on the corrected microchannel path design data, adjust the branch angle of the 3D printed salt core mold to the optimized range (such as 50° - 60°), and update the channel spacing (1.2 mm - 2.5 mm) according to the heat flux density gradient. Encrypt the support skeleton density of the salt core mold in the high heat area (such as reducing the grid spacing to 0.8 mm). By enhancing the local structural stiffness to resist the injection melt pressure, avoid the collapse or deformation of the microchannel during the high-pressure injection stage. This parameter combination realizes the collaborative design of the bionic fractal structure and mechanical stability, ensuring the forming accuracy of complex topological microchannels.

[0057] S52, assemble the optimized salt core mold into the injection mold, adopt a segmented pressure-holding injection strategy. After injection, perform ultrasonic water dissolution on the shell preform to remove the residual salt core mold on the shell, and inject to form an optimized shell matrix; preferably, a 5-second high-frequency (150 kHz) / 5-second low-frequency (80 kHz) alternating oscillation mode can be adopted, and the total duration is shortened to 20 minutes.

[0058] Adopt an alternating oscillation mode of 150 kHz high frequency and 80 kHz low frequency (with a 5-second alternation period). The high-frequency cavitation effect efficiently breaks the main structure of the salt core, and the low-frequency mechanical vibration removes the residual particles in the slit. Compared with the single-frequency mode, the alternating oscillation expands the action range through spectrum superposition, shortens the total duration to 20 minutes, and at the same time avoids the wear of the inner wall of the microchannel caused by long-term high-frequency ultrasound. This parameter setting balances the dissolution efficiency and the need for structural protection, ensuring the surface quality of the through-type microchannel.

[0059] S53, Integrate a hexagonal honeycomb protrusion array and microstructural forming on the optimized housing substrate to obtain the housing finished product.

[0060] S54, Scan the surface temperature field of the housing through an infrared thermal imager, detect the heat flux uniformity in the microchannel area under a preset standard power consumption simulation heat source. If the local temperature difference > 1.5 °C, it is marked as a defect area, and the secondary compensation algorithm for the support density of the salt core mold is triggered; Scan the surface temperature field of the housing through an infrared thermal imager. If a local temperature difference > 1.5 °C (corresponding to a flow dead zone or blockage defect in the microchannel) is detected, the secondary compensation algorithm for the support density is triggered. This algorithm reversely adjusts the support skeleton density of the salt core mold based on the coordinates of the defect area (such as locally increasing it to 1.2 times), and eliminates the forming deviation of the microchannel by enhancing the filling integrity of the melt in the defect area during the injection molding stage. This online detection - feedback correction mechanism improves the process yield rate to a controllable range.

[0061] S55, Perform coating and film - covering treatment on the qualified housing finished product. Spray a graphene heat - conducting layer on the inner wall of the microchannel and deposit a surface film layer on the outer surface to complete the preparation of the PCR housing finished product.

[0062] Spray a graphene heat - conducting layer (thickness ≈ 5 μm) on the inner wall of the microchannel. Utilize its in - plane ultra - high heat - conducting coefficient to enhance the radial heat diffusion ability and compensate for the anisotropic heat - conducting limitation of the polymer matrix. Deposit a hydrophobic and wear - resistant coating on the outer surface to reduce the long - term impact of dust accumulation on the heat dissipation performance by reducing the surface adhesion force. The step - by - step application process of the inner and outer functional coatings avoids cross - contamination and realizes the synchronous improvement of the heat dissipation efficiency and durability of the housing.

[0063] Example 2: Combined with Figure 3 As shown, it is a mobile phone PCR housing of one model, but not limited to this one housing. The present invention specifically provides a mobile phone PCR housing, prepared by using the processing method of the mobile phone PCR housing in Example 1. The PCR housing includes: A housing substrate 10, in which a three - dimensional heat - conducting network formed by polycarbonate base material uniformly dispersed with boron nitride nanosheets and carbon fibers is inside; A bionic microchannel layer 20, embedded inside the housing substrate, including continuous flow channels with a preset branch angle, where the channel spacing in the high - heat - flux area is the first width; The convex array 30 is formed on the outer surface of the base body, and microstructures are correspondingly arranged on the convex array; The graphene heat-conducting coating 40 covers the inner wall of the microchannel.

[0064] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A processing method for a mobile phone PCR housing, characterized in that, The following steps are involved: S1, mixing polycarbonate, boron nitride nanosheets and carbon fibers in a preset ratio, performing gradient dispersion blending and directional shearing through a twin-screw extruder to prepare a composite masterbatch having a three-dimensional thermal conductive network; S2, injecting the composite material masterbatch into a mold pre-set with a soluble salt core mold for injection molding, dissolving and removing the salt core to form a shell matrix containing a bionic microchannel; S3, using a laser etching process to process a hexagonal honeycomb protrusion array on the outer surface of the shell substrate, and realizing microstructure formation of a predetermined depth by controlling the laser power and scanning speed; S4, based on the heat source distribution data of the heating element, optimizing the branch angle of the microchannel through thermal-fluid coupling simulation to generate a revised microchannel path design; S5, adjusting the layout of the soluble salt core mold according to the modified microchannel path design, and re-injection molding to form an optimized shell microchannel structure to obtain a PCR shell finished product.

2. The processing method of the mobile phone PCR housing according to claim 1, wherein, The ratio of the polycarbonate, the boron nitride nanosheets and the carbon fiber is 70:20:10, wherein the carbon fiber is chopped carbon fiber.

3. The processing method of the mobile phone PCR housing according to claim 2, characterized in that, The step S1 comprises the following steps: S11, placing the polycarbonate particles in a vacuum drying oven and performing a dehydration treatment at 100° C. for 4 hours to obtain a dry polycarbonate base material; S12, mixing boron nitride nanosheets and carbon fiber chopped strands in a mass ratio of 2:1, adding them to anhydrous ethanol for ultrasonic dispersion for 30 minutes to form a uniform BNNS-CF suspension, and then preparing a composite thermal conductive filler powder by centrifugal spray drying; S13, feeding the dried polycarbonate base material and the composite thermal conductive filler powder into a segmented temperature-controlled hopper of a twin-screw extruder at a mass ratio of 70:30, wherein the temperature of the front screw zone is set to 180° C., and the temperature gradient of the rear screw zone is increased to 210° C.; S14, during the twin-screw extrusion process, the front section uses a low shear rate to melt the polycarbonate and initially wrap the filler, and the rear section switches to a high shear rate and a combination of reverse screw elements to force the boron nitride nanosheets to be oriented along the extrusion direction. At the same time, the carbon fibers are induced by the shear force to form a cross-layer overlapping network to construct a three-dimensional thermal conductive network; S15, the extruded composite material melt is subjected to water-cooling and strand-cutting to obtain a composite material masterbatch having a three-dimensional thermal conductive network and a target axial thermal conductivity coefficient.

4. The processing method of the mobile phone PCR housing according to claim 1, characterized in that, The step S2 comprises the following steps: S21, presetting the soluble salt core mold into a bionic leaf vein-like branch structure, wherein the soluble salt core mold is formed into a continuous network skeleton of a preset size by 3D printing from NaCl powder, and fixed to the inner surface of the mold cavity by a water-soluble adhesive; S22, heating the composite masterbatch to a molten state and then injecting it into a mold, using a segmented pressure-maintaining injection molding strategy: in the initial stage, the cavity gap is filled with a low pressure of 50 MPa, and then switched to a high pressure of 80 MPa to compact the contact interface between the molten body and the soluble salt core mold, and after cooling and solidification, a shell preform covering the salt core is formed; S23, taking the shell preform out of the mold, immersing it in 40° C. deionized water, and oscillating it with 120 kHz ultrasonic waves for 30 minutes to dissolve and discharge the soluble salt core mold to form a through-type bionic leaf vein microchannel; S24. Perform vacuum drying treatment on the housing substrate after removing the salt core to control the residual moisture and complete the preparation of the housing substrate with a three-dimensional heat dissipation path.

5. The method for processing the mobile phone PCR housing according to claim 1, characterized in that, The step S3 includes the following steps: S31. Perform plasma cleaning treatment on the outer surface of the housing substrate. Treat the surface with argon plasma for 60 seconds to remove residual contaminants and improve the laser absorption rate. S32. Import the hexagonal honeycomb array design parameters into the laser galvanometer control system to generate a spiral progressive scanning path matching the honeycomb cell size, and match the pulse interval and focal spot diameter. S33. Start etching with a fiber laser at a base power of 20W. Increase the power to 25W and reduce the scanning speed to 400mm / s in the edge area of the honeycomb cell to form a reinforced groove with a first depth, and maintain the power at 18W and the speed at 600mm / s in the central area to form a shallow concave surface with a second depth. S34. Synchronously introduce a nitrogen curtain during the laser etching process. The air flow rate is 15L / min, and it blows the molten products at an angle of 45° to the laser beam to inhibit surface carbonization and improve the verticality of the side walls of the hexagonal protrusions.

6. The method for processing a mobile phone PCR housing according to claim 5, wherein, After the step S34, the following steps are also included: S35. Real-time monitor the forming depth of the honeycomb structure through a confocal microscope. When the height deviation of the detection unit exceeds the allowable threshold, dynamically adjust the laser power compensation coefficient for secondary precision etching. S36. Anneal the etched housing in an incubator at 120°C for 2 hours to eliminate the local residual stress caused by laser processing and obtain a preliminary housing.

7. The method for processing a mobile phone PCR housing according to claim 6, wherein The step S4 includes the following steps: S41. Integrate the target main board with the preliminary housing. Collect the real-time temperature field distribution data of the target main board under the preset standard power consumption through an infrared thermal imager, and extract the peak coordinates of the heat flux density in the projection area of the heating elements by combining current density analysis. S42. Establish a three-dimensional thermal-fluid coupling simulation model of the housing based on the peak coordinates of the heat flux density. Set the microchannel branch angle as the initial variable, and set the chip junction temperature ≤ 85°C and the housing surface temperature ≤ 45°C as the constraint conditions. S43. Use a hybrid iteration of the genetic algorithm and the finite element method to calculate the thermal resistance gradient distribution at different branch angles, and screen the optimized angle range that can improve the uniformity of heat flow diffusion. S44. Reconstruct the bionic vein-like microchannel topology structure according to the optimized angle range to generate a corrected path data packet with a gradient branch density, where the channel spacing in the high heat flux area is reduced to the first width, and the low heat flux area is expanded to the second width. S45. Import the corrected path data packet into the fluid dynamics verification module to simulate the flow velocity field and temperature field under transient thermal shock (greater than the preset standard power consumption). When the detected local temperature difference > 2°C, reversely correct the channel branch curvature radius to the preset range to generate the corrected microchannel path design.

8. The mobile phone PCR housing processing method according to claim 7, characterized in that, The step S4 includes the following steps: S51. According to the corrected microchannel path design data, adjust the structural parameters of the 3D printed soluble salt core mold. Lock the branch angle to the optimized angle range, update the channel spacing from the first width to the second width according to the heat flux density gradient, and increase the density of the support skeleton of the salt core mold in the high heat area. S52. Assemble the optimized salt core mold into the injection mold, adopt a segmented pressure-holding injection strategy, and perform ultrasonic water dissolution on the shell preform after injection to remove the residual salt core mold on the shell, so as to injection-mold an optimized shell matrix; S53. Integrate a hexagonal honeycomb protrusion array and micro-structure forming on the optimized shell matrix to obtain a finished shell product.

9. The method for processing the mobile phone PCR housing according to claim 8, wherein After the step S53, it further includes: S54. Scan the surface temperature field of the shell through an infrared thermal imager, detect the heat flux uniformity in the micro-channel area under a preset standard power consumption simulation heat source. If the local temperature difference > 1.5 °C, mark it as a defective area and trigger the secondary compensation algorithm for the support density of the salt core mold; S55. Perform coating and film covering treatment on the qualified shell product, spray a graphene heat conduction layer on the inner wall of the micro-channel, and deposit a surface film layer on the outer surface to complete the preparation of the PCR shell product.

10. A mobile phone PCR housing, characterized in that, Obtained by using the mobile phone PCR shell processing method according to any one of claims 1 to 9, the PCR shell includes: A shell matrix, in which a three-dimensional heat conduction network formed by polycarbonate base material uniformly dispersed with boron nitride nanosheets and carbon fibers is arranged inside; A bionic micro-channel layer, embedded inside the shell matrix, including continuous flow channels with a preset branch angle, and the channel spacing in the high heat flux area is the first width; A protrusion array, formed on the outer surface of the matrix, and micro-structures are correspondingly arranged on the protrusion array; A graphene heat conduction coating, covering the inner wall of the micro-channel.

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