Key Considerations for Injection Molded Components in Automotive Electronics

Automotive electronic components, such as electrical boxes (ECU housings), connectors, and sensor housings, serve as critical carriers for vehicle electrical systems. Their injection molding production must balance electrical reliability, mechanical stability, environmental resistance, and production efficiency. This article analyzes key factors from four dimensions: material selection, mold design, process control, and quality validation.  

I. Material Selection: Balancing Electrical Properties and Environmental Resistance

1. High-Temperature Resistance

   - Components near engine compartments (e.g., ECU housings) must withstand long-term temperatures ≥150°C, with short-term peaks up to 200°C. Polyphenylene sulfide (PPS) is a preferred material due to its high heat resistance (continuous use temperature ≥200°C), low coefficient of thermal expansion, and flame retardancy (UL94 V-0).  

   - Components requiring soldering (e.g., connectors) must endure reflow soldering temperatures (260°C/10s), met by PPS or high-temperature nylons (PA6T/PA9T).  

2. Electrical Insulation and Stability  

   - High insulation resistance (≥10¹⁵ Ω·cm) and low dielectric loss (≤0.001) are crucial to prevent current leakage and signal interference. Materials like PPE+PS maintain electrical stability across a wide temperature range (-40°C to 140°C).  

   - Adding glass fibers (30%-40%) enhances mechanical strength but may cause anisotropic shrinkage due to fiber orientation, affecting dimensional accuracy.  

3. Chemical Corrosion Resistance

   - Components exposed to coolants or fuels (e.g., sensor housings) require resistance to chemical erosion. PPS exhibits excellent tolerance to most acids, alkalis, and solvents.  

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II. Mold Design: Precision and Efficiency Synergy

1. Runner and Gate Optimization  

   Hot Runner Systems: Reduce cold slug residue and improve material utilization (≥95%). Valve-gated systems prevent drooling, ideal for multi-cavity molds (e.g., 64-cavity connector molds).  

   Gate Design: Large parts like electrical boxes use fan gates (width ≥2x wall thickness) to reduce internal stress; precision parts like connectors use pin-point gates (diameter 0.1-0.3mm) to minimize shear heat.  

2. Cooling and Venting

   - Conformal Cooling Channels: 3D-printed stainless steel channels follow cavity contours, reducing cooling time by 20% and minimizing warpage.  

   - Nano-Scale Vents: Depth 0.01-0.025mm at melt flow ends, preventing air traps that cause burns or short shots.  

3. Ejection and Tolerance Control  

   - Draft angles ≥0.5° prevent ejection damage; ejector pins must avoid functional areas (e.g., connector pin slots).  

   - Dimensional tolerances must be tighter than general standards: electronic components typically require tolerances within ±0.2mm.  

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III. Injection Process: Ensuring Stability and Repeatability  

1. Process Parameter Windows  

   -Drying: Hygroscopic materials like PPS require drying at 120°C/4h, with moisture content ≤0.02% (to prevent hydrolysis).  

   - Melt Temperature: PPS processes at 280-320°C; excessive heat causes degradation. PPE+PS recommends 240-270°C.  

   - Holding Pressure: 80%-90% of injection pressure, with holding time calculated as 1 second/mm wall thickness, reducing sinks (e.g., OBD housing warpage optimization case).  

2. Process Monitoring and Adaptive Control  

   - In-mold pressure sensors (accuracy ±0.1bar) monitor fill status in real-time, enabling dynamic V/P switch adjustments.  

   - IoT technology logs parameters per cycle, facilitating abnormal batch tracing (e.g., Vitesco Technologies’ transmission control unit production line).  

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IV. Quality Validation: Comprehensive Testing from Lab to Road  

1. Electrical Performance Testing  

   - Dielectric strength tests (AC 500V/min, no breakdown), insulation resistance tests (DC 500V, ≥100MΩ).  

2. Environmental Reliability  

   - Thermal cycling tests (-40°C to 140°C, 1000 cycles) verify cracking or performance degradation.  

   - Chemical resistance tests: Immersion in engine oil/coolant (1.5h) with no cracking or swelling.  

3. Mechanical Performance

   - Vibration tests (frequency 10-200Hz, acceleration 5G) simulate road conditions; connector pin retention force decay must be ≤10%.  

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V. Industry Trends and Innovations

1. Material Innovations  

   - Carbon fiber-reinforced PPS (20% CF) enhances stiffness (elastic modulus ≥15GPa) and reduces weight (density 1.4g/cm³).

2. Process Integration  

   - Insert Molding: Metal terminals are directly overmolded, reducing assembly steps (e.g., Vitesco’s full injection technology).  

3. Digital Factories  

   - CAE moldflow analysis (e.g., Moldflow) predicts warpage early (e.g., OBD housing case with error ≤9.7%), reducing trial cycles.  

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Conclusion  

Automotive electronic injection molding is a systematic project involving materials, design, process, and validation. Core requirements include:  

- High heat and electrical insulation materials(e.g., PPS, PPE+PS);  

- Precision mold cooling and venting (conformal channels, nano-vents);  

- Process robustness(parameter window control, IoT monitoring);  

- Comprehensive validation (electrical, environmental, mechanical reliability).  

As electric vehicles adopt high-voltage platforms (800V), demands for insulation (CTI≥600V) and heat dissipation will further drive innovations toward multifunctional integration (e.g., combining heat dissipation structures with electrical isolation).