In 5G telecom modules, automotive digital cockpits, and millimeter-wave radar boards, two-piece RF shield cans are secured via SMT shield clips, eliminating manual hand-soldering while ensuring 360° EMI shielding and low-impedance grounding. Ensuring contact springs maintain consistent normal force after 260°C reflow heat shock and repeated insertion cycles is the core objective of stamping DFM.
Three Core Spring Materials Compared: Beryllium Copper vs. Titanium Copper vs. SUS301
1. **Beryllium Copper (C17200)**: Yield strength of 1100~1350 MPa, conductivity 22%~28% IACS, and unmatched resistance to thermal stress relaxation. Retains > 95% spring force after 260°C reflow, making it the premier choice for high-reliability shield clips.
2. **Titanium Copper (C19900)**: Beryllium-free for strict environmental compliance, offering strength and elasticity close to beryllium copper with excellent bend formability.
3. **Stainless Steel (SUS301-CSP 1/2H / 3/4H)**: Low cost and high mechanical strength, but low electrical conductivity (3% IACS) and poor solderability require specialized nickel pre-plating prior to matte tin or gold plating.
Normal Contact Force & Low Contact Resistance (< 20 mΩ)
To prevent microsecond contact discontinuity under automotive vibration and thermal cycling, initial spring normal force is engineered between $0.5\text{ N} \sim 1.2\text{ N}$. Paired with 0.05μm~0.1μm selective gold plating, contact resistance stays strictly under 20 mΩ, delivering > 75 dB shielding effectiveness from 100MHz to 10GHz.
- Mating Fatigue Life: Normal force degradation < 15% across 5,000 to 10,000 insertion cycles
- Reflow Heat Resistance: Zero thermal creep relaxation after 260°C peak temperature exposure for 30s
- SMT Pad Retention: Solder foot peel and shear strength > 15 N
- Packaging Format: EIA-481 Tape & Reel with Kapton pick-up caps supporting 0.1s/part pick rates
Two-Piece Shielding vs. Traditional One-Piece Soldered Cans
Traditional one-piece metal cans must be hand-soldered directly to PCB ground perimeters, requiring heat guns for board rework that risk damaging adjacent passive components. SMT shield clips solder in the primary reflow pass, allowing shield cans to snap into place mechanically and be easily removed with tweezers for testing and service, slashing total production rework costs by over 70%.