The primary structural types of mobile phone shielding covers include integrated (fixed) units, two-piece assemblies (a base frame/shielding cage plus a cover plate), and detachable systems. The integrated structure is simple, low-cost, and offers excellent shielding effectiveness; however, it hinders the repair of internal components. The two-piece structure facilitates adhesive dispensing and repairs, though it entails higher costs and may result in increased overall height. Detachable systems typically consist of a base (shielding frame) soldered to the circuit board and a snap-on shielding cover, making them highly convenient for maintenance.
Materials used for shielding covers must possess good electrical and magnetic conductivity, as well as excellent mechanical strength, processability, and solderability. Common materials include nickel silver/cupronickel (e.g., C7521), stainless steel (e.g., SUS304), tinplate (tin-plated steel), and beryllium copper. Cupronickel offers slightly lower shielding effectiveness but is easy to solder; stainless steel provides superior shielding and high strength but is more difficult to solder; and tinplate is inexpensive but offers the lowest shielding effectiveness.
Shielding covers are primarily manufactured using stamping dies, which are categorized into single-stage dies and progressive dies. The manufacturing process typically involves multiple stages, including blanking, forming, punching, and the application of insulating tape.
Core design specifications include: a draft angle typically ranging from 2° to 4°; relief designs at corners to ensure a gap-free fit after assembly; the inclusion of a regularly shaped (e.g., square) suction pad area at the center of gravity-sized larger than the SMT pick-and-place machine's nozzle-to facilitate automated assembly; the provision of designated channels for adhesive dispensing around BGA chips, with a minimum dispensing clearance of 2 mm; and the incorporation of "postage stamp" perforations at shielding frame joints to facilitate cutting and removal during repairs. To prevent solder bridging during assembly, the soldering interface often employs a "Great Wall" foot structure-typically an alternating pattern of 2 mm contact points and 1 mm gaps.
Methods for mounting and securing shielding covers primarily include soldering, snap-fitting, and screw fastening. Soldering methods encompass direct soldering of single-piece units and the soldering of two-piece assemblies (base frame + cover); the former is low-cost but inconvenient for repairs, while the latter facilitates repairs but requires the fabrication of two separate sets of stamping dies. Snap-fit structures utilize the interlocking engagement of protrusions and corresponding holes to achieve secure fastening.
