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On the assembly line of a new energy charging pile production base in North China, a batch of charging modules to be delivered is undergoing the final sealing test. pcb box build assembly services. Engineers holding a thermal imager swept across the surface of the aluminum alloy shell, the screen shows that the temperature difference between the heat dissipation area is no more than 3 ℃, the internal power device temperature is stable at 65 ℃. This seems to be an ordinary metal shell, in fact, is the core carrier of the PCBA protection system, behind the material science, structural design and process control involved in the complexity of far more than imagined.
PCBA shell is essentially an electronic system of “mechanical armor”, need to meet the electromagnetic shielding, environmental protection, heat conduction three core functions. 5G base station amplifier module, for example, its shell needs to be in -40 ℃ ~ 85 ℃ environment, to withstand 20G vibration impact, while the amplifier tube junction temperature control at 90 ℃ or less. Measured data from an equipment vendor shows that the optimized die-cast aluminum enclosure enables the module MTBF (Mean Time Between Failure) to increase from 50,000 hours to 80,000 hours.
1. Material classification
(1) ABS plastic: cost control in 8-15 yuan / kg, temperature resistance -20 ℃ ~ 80 ℃, in the field of smart home controller occupies 60% market share. A brand of sweeping robot using glass fiber reinforced ABS, wall thickness of 1.5mm can reach the IK08 impact rating.
(2) Aluminum alloy 6063: thermal conductivity 209W/(m-K), density 2.7g/cm³, the mainstream choice for new energy vehicle on-board charger (OBC) shell. Die-casting process can achieve 0.1mm wall thickness accuracy, with anodic oxidation treatment, salt spray test up to 1000 hours.
(3) Stainless steel 304: yield strength of 215MPa, the mandatory requirements of medical equipment shell material. The shell of a blood analyzer adopts 1.2mm deep-drawing process, with 0.5mm rounded corners at the right angle, and passes 100,000 times of opening and closing life test.
(4) PC+silicone composite: a breakthrough solution for smart wearable devices, realizing IP68 protection through two-color injection molding. A sports bracelet shell in 2 meters of water depth to maintain 72 hours without leakage, key force control at 1.2N ± 0.3N.
2. The manufacturing method
(1) precision mold development: automotive-grade connector shell molds are required to achieve Class-1 precision, mold hardness needs to be more than HRC52. A connector manufacturer's 64Pin shell mold, the use of mold flow analysis software optimization, injection cycle from 28 seconds to 19 seconds, flying edge control within 0.02mm.
(2) special molding process: deep cavity shell using gas-assisted injection molding, wall thickness difference from ± 0.3mm reduced to ± 0.1mm. an industrial PLC shell through this process, while maintaining a wall thickness of 2mm, the weight will be reduced by 35%. Ultra-thin metal shell using continuous stamping process, a Type-C interface shell of 0.3mm stainless steel strip, stamping and molding through 12 processes, flatness up to 0.05mm/m².
(3) surface treatment process: conductive oxidation treatment of military equipment shell, film thickness of 8-12μm, contact resistance <5mΩ. a radar shell after micro-arc oxidation, the surface hardness of HV800, arc abrasion resistance time to improve 3 times. The antibacterial coating of medical shell is plasma sprayed, and the killing rate of Staphylococcus aureus on the surface of the shell of an endoscope handle reaches 99.99%, and it passes 2000 times of alcohol wipe test. pcb box build assembly services
3. The production of necessary drawings and information
(1) 3D model files: a car controller shell STEP file contains a complete assembly relationship tree, 0.05mm fit tolerance labeling, and 16 EMI shrapnel mounting position of the shape and position tolerance requirements.
(2) Two-dimensional engineering drawings: precision connector housing drawings marked 32 key dimensions, including 5 positioning holes marked ± 0.01mm tolerance, and specifically indicated that the allowable range of ejector marks: non-appearance surface ≤ 0.1mm.
(3) Material specification: PC material requirements for an outdoor power supply housing: UL94 V-0 flame retardant grade, color difference ΔE <1.5, light transmittance > 88% (LED indicator window area).
(4) Process flow chart: die-casting aluminum shell production process contains 12 main processes, of which the T5 heat treatment process is clearly required: solid solution temperature of 530 ℃ ± 5 ℃, holding time of 2.5h, water quenching and transfer time <8 seconds.
(5) testing standards document: waterproof shell airtightness testing standards: apply 50kPa air pressure, holding pressure for 30 seconds, leakage <5Pa/min. an underwater equipment shell using helium mass spectrometry leak detection, detection sensitivity up to 5 × 10-⁹Pa-m³/s.
4. Test standards
Different use test standards are not the same, for example, in a certain type of armored vehicle communication system in the environmental test, PCBA shell need to withstand:
Vibration test: 10-2000Hz random vibration, PSD value 0.04g²/Hz, for 3 hours
Damp heat cycle: 40 ℃ / 95% RH conditions, 7 consecutive days of alternating test
Electromagnetic shielding: Shielding efficiency ≥80dB at 1GHz frequency.
Three-proof processing: anti-mold grade to GB/T2423.16-2008 level 1 standards
The magnesium alloy shell developed by a military unit reduces weight by 40% through topology optimization design under the premise of guaranteeing EMC performance, and it can resist the impact of 7.62mm bullets at a distance of 15 meters. pcb box build assembly services
In the clean workshop of a satellite R&D center in Beijing, engineers are doing the final thermal vacuum test on the starboard computer shell. This shaped shell made of carbon fiber composite material is controlled within 0.02mm of deformation under the extreme temperature difference of -180℃~+120℃. From consumer electronics to aerospace, the PCBA shell has evolved from a simple protective component to a systematic project that integrates materials, processes, and standards. With the popularization of micro-foam injection molding, metal 3D printing and other new processes, shell manufacturing is breaking through the traditional boundaries - the future of the electronic protection system, perhaps the device itself.