As key structural components of precision electronic equipment, the surface quality of electronic communication die castings directly affects signal transmission stability and equipment reliability. Surface microcracks primarily arise from hindered alloy solidification shrinkage, mold design defects, and uncontrolled process parameters, requiring systematic process optimization for crack prevention.
Balancing the mold temperature field is crucial for preventing microcracks. Electronic communication die castings often use high thermal conductivity aluminum alloys. If the temperature difference between the mold core and cavity exceeds 15°C, it can lead to excessively different solidification rates in localized areas. By embedding conformal cooling water channels in the mold's hot spots, the temperature difference between the core and cavity surfaces can be controlled within 5°C, creating a sequential solidification pattern from thin-walled to thick-walled sections. For example, after optimization of a certain type of 5G base station filter die casting, cracks originally located at the root of the reinforcing ribs were transferred to the overflow groove, and after removal, the product yield significantly improved.
Precise design of the gating system is essential for reducing microcracks. Traditional sprues easily cause molten metal to rush directly to the corners of the cavity, leading to localized overheating and stress concentration. By employing an arc-shaped runner combined with a multi-point ingate layout, molten metal can fill the mold cavity in a laminar flow state. One company reduced the internal shrinkage volume of the die-cast communication equipment casing by increasing the number of ingates and adjusting their cross-sectional area ratio, while essentially eliminating surface shrinkage defects. Furthermore, adding an annular overflow groove at the parting surface effectively removes cavity gas, preventing cracks caused by gas stagnation.
Dynamic control of injection process parameters must be matched to material properties. Electronic communication die castings commonly use ADC12 aluminum alloy, which has a high liquid shrinkage rate. Excessive injection speed can lead to gas entrapment in the cavity. By using three-stage injection speed control, reducing the flow rate before the molten metal reaches the hot spot zone, the amount of gas entrapment can be reduced. In the die casting of a certain type of router casing, adjusting the injection speed to a segmented variable speed mode reduced the occurrence of shrinkage cavities and increased tensile strength.
Mold structure optimization is a key measure to eliminate stress concentration. For thin-walled die-cast parts commonly used in communication equipment, rounded corners are employed at intersections. The radius of the rounded corner must be greater than 0.6 times the wall thickness to significantly reduce stress concentration. One company significantly reduced the maximum principal stress in filter brackets by changing the right-angle transition to a rounded corner, resulting in a more uniform stress distribution and eliminating stress concentration. Simultaneously, removing unnecessary core holes in the mold reduces the risk of cracking.
Fine-tuning of material composition can further improve cracking tendency. Adding titanium to aluminum alloys refines the grain structure and reduces solidification shrinkage stress. One company reduced the shrinkage cavity depth of die-cast communication base station antennas by adjusting the alloy composition, while significantly improving corrosion resistance. Furthermore, controlling silicon content within a specific range ensures fluidity while reducing the tendency for hot cracking.
The appropriate application of post-processing techniques can eliminate residual stress. Aging treatment of die-cast parts can eliminate internal stress. After aging treatment, the incidence of surface microcracks in a certain type of fiber optic connector die-cast part decreased, while dimensional stability was significantly improved.
Controlling surface microcracks in electronic communication die castings requires optimization across the entire process, from mold design and process parameters to material selection and post-processing. By balancing the mold temperature field, optimizing the gating system, controlling the injection process, improving the mold structure, fine-tuning the material composition, and implementing post-processing, the surface quality of die castings can be significantly improved, meeting the stringent requirements of high-precision electronic equipment for structural reliability.
