Connector Shielding Can Stamping: Design and Process Guide

Shielding cans — the thin-metal enclosures that surround connector signal paths and electronic components — are essential for electromagnetic interference (EMI) suppression in modern electronic devices. Produced at rates of 300 – 800 parts per minute from 0.10 – 0.30 mm metal strip, these pressed components demand exceptional dimensional consistency across millions of cycles. This guide covers the materials, tooling, process controls, and finishing operations for high-volume shielding can stamping.

Material Selection for Shielding Cans

The shielding effectiveness of a metal can depends on material conductivity, thickness, and the frequency of the interfering signal. The most common materials for connector and electronics shielding include:

Material	Conductivity (%IACS)	Thickness Range (mm)	Shielding Effectiveness (30 MHz – 1 GHz)	Formability Rating
C2680 (Brass, H01 temper)	27 – 28	0.10 – 0.30	60 – 80 dB	Very good
C5210 (Phosphor bronze)	12 – 15	0.08 – 0.25	55 – 75 dB	Good
SPCC / SECC (Cold-rolled steel)	8 – 12	0.15 – 0.50	65 – 85 dB	Good
304 stainless steel	2.5 – 3.5	0.08 – 0.20	50 – 70 dB	Moderate
C1100 (Copper, soft annealed)	100 – 101	0.10 – 0.25	75 – 95 dB	Excellent
5052-H32 aluminum	25 – 30	0.20 – 0.50	50 – 70 dB	Very good

Brass C2680 in H01 (quarter-hard) temper is the most commonly specified shielding can material. It offers 27% IACS conductivity, sufficient for 60+ dB shielding up to 1 GHz, with excellent formability for deep-drawn shapes. When maximum shielding is required at frequencies above 1 GHz, copper C1100 provides 100% IACS conductivity and the lowest insertion loss, though at significantly higher material cost.

Progressive Die Design for Shielding Cans

Shielding can stamping uses progressive dies with 10 – 20 stations, with the specific sequence depending on the can geometry (flat, drawn, or combination). A typical sequence for a drawn shielding can includes:

Station 1 — Pilot Holes. Two pilot holes are pierced in the strip carrier (scrap area). Position tolerance is ±0.01 mm. Station 2 — Blanking. The blank outline is partially cut, leaving tabs connecting the blank to the strip carrier. Blank size is calculated as the developed surface area of the can plus 3 – 5% for material thinning during drawing. Station 3 — Drawing (Stage 1). First draw operation reduces the blank diameter to 60 – 70% of the original. Draw ratio (blank diameter ÷ punch diameter) is limited to 1.8 – 2.0 for brass and steel, 1.6 – 1.8 for stainless steel without intermediate annealing. Clearance between punch and die is 1.08 – 1.12× material thickness. Station 4 — Drawing (Stage 2). Second draw further reduces the can depth. Draw ratio is 1.2 – 1.4. The can wall starts to elongate; ironing may occur at this stage, reducing wall thickness by 5 – 15%. Station 5 — Piercing (Side Holes). Any side holes or slots for connector pin clearance are pierced using cam-driven punches. Punch diameter of 0.5 – 2.0 mm requires carbide punches at 88 – 90 HRA with clearance of 3 – 5% per side. Station 6 — Bottom Forming. The can bottom is flattened or embossed with dimples (0.1 – 0.3 mm height) for solder paste standoff. Bottom flatness is maintained within ±0.05 mm. Station 7 — Trim and Cutoff. The can bottom edge is trimmed to final height with a tolerance of ±0.05 mm. The connecting tabs are cut, releasing the finished can from the strip.

Draw Ratio and Annealing Control

The draw ratio — the ratio of initial blank diameter to punch diameter — is the single most important parameter in shielding can stamping. Exceeding the material's limiting draw ratio (LDR) causes splitting at the can wall:

Material	Temper	Limiting Draw Ratio (LDR)	Annealing Required Above	Annealing Temperature
C2680 brass	H01 (¼ hard)	1.9 – 2.0	2 stages	450 – 550°C
C2680 brass	O (soft annealed)	2.1 – 2.2	2 stages	450 – 550°C
C5210 phosphor bronze	H02 (½ hard)	1.7 – 1.9	1 stage	525 – 625°C
304 stainless steel	Annealed	1.9 – 2.1	1 stage	1,010 – 1,120°C
SPCC steel	Annealed	2.0 – 2.2	2 stages	680 – 760°C
C1100 copper	Annealed	2.2 – 2.4	3 stages	400 – 500°C

For deep-drawn shielding cans requiring more than two draw stages, in-line annealing becomes economical. Induction annealing stations between draw stages heat the partially formed can to the recrystallization temperature in 0.5 – 2.0 seconds, restoring ductility. The energy cost of induction annealing is approximately $0.003 – $0.008 per part, adding 5 – 10% to total processing cost but enabling draw depths that would otherwise require multiple press transfers.

Lubrication and Coolant Strategy for Shielding Can Stamping

The high surface area of shielding can stamping generates significant friction at the draw interface. Lubrication directly affects draw quality and tool life.

Draw Oil (Chlorinated). For draw ratios above 1.8, chlorinated paraffin-based oils provide the highest extreme-pressure performance. Applied at 1 – 5 g/m² by roller coating. Chlorinated oils leave residues that require alkaline cleaning before plating — surface cleanliness of 0.01 mg/m² per IPC-CH-65A. Emulsion Lubricants. For moderate draw ratios (1.4 – 1.8), water-emulsion lubricants at 5 – 15% concentration provide adequate lubrication with lower cleaning cost. pH maintained at 7.5 – 9.0 prevents corrosion between operations. Dry Film Lubricants. Wax-based coatings are increasingly used for shielding can stamping due to zero cleaning requirement. Coating thickness of 0.5 – 2.0 µm is applied by the coil supplier before stamping. Cost premium of $0.01 – $0.03 per kg of coil is offset by elimination of post-stamping cleaning.

Burr Control and Edge Quality

Burr on shielding can edges causes assembly problems (difficulty inserting into connector housing slots) and creates loose particles that can cause short circuits. Key burr control measures include:

Die Clearance Optimization. For materials under 0.20 mm thickness, optimal die clearance is 3 – 5% of material thickness per side. Clearance maintained within ±0.005 mm across all 20+ die stations requires CNC-ground die plates with positional accuracy of ±0.002 mm. Punch Condition Monitoring. Burr height increases with punch wear. For most shielding can applications, acceptable burr is under 0.03 mm. Punches for pierce stations are replaced when burr exceeds 0.05 mm. Carbide punches typically achieve 200,000 – 500,000 strokes between replacements. Deburring. For cans requiring burr under 0.01 mm — typical for pick-and-place applications — centrifugal disc deburring with 3 – 5 mm ceramic media for 5 – 15 minutes removes residual burr. Process cost is $0.002 – $0.005 per part.

Surface Finishing and Plating

Shielding cans are typically plated after stamping to enhance corrosion resistance and solderability:

Tin Plating. Matte tin at 3 – 8 µm is the standard finish for shielding cans requiring solderability. Pure tin without nickel underplate is preferred for RoHS compliance. Pin-hole density must be below 5 per cm² to prevent corrosion.

Process Capability	Brass (C2680 H01)	SPCC Steel	304 Stainless Steel
Max draw depth (single stage)	8 – 12 mm	10 – 15 mm	5 – 8 mm
Min corner radius (bottom)	0.15 mm	0.20 mm	0.30 mm
Min wall thickness (after ironing)	0.08 mm	0.10 mm	0.06 mm
Flatness over 20 mm length	±0.05 mm	±0.08 mm	±0.10 mm
Burr height (piercing)	≤ 0.03 mm	≤ 0.04 mm	≤ 0.05 mm
Shielding effectiveness at 1 GHz	65 – 80 dB	70 – 85 dB	55 – 70 dB
Relative material cost	1.0× (baseline)	0.5 – 0.7×	1.8 – 2.5×

Tin-Silver Plating. For applications requiring extended salt spray resistance (>72 hours), tin-silver alloy plating (97Sn/3Ag) at 3 – 6 µm provides superior corrosion performance. Cost is 15 – 30% higher than pure tin. Passivation (Stainless Steel). For 304 stainless steel cans, nitric acid passivation provides corrosion resistance. No thickness buildup, cost of $0.001 – $0.003 per part.

Conclusion

Shielding can stamping demands precision in material selection, die design, and process control. Brass C2680 in H01 temper remains the workhorse material, balancing conductivity, formability, and cost. The critical challenges are draw ratio management to prevent splits, burr control to ensure clean assembly, and plating adhesion for reliable solder connections. With well-designed progressive tooling and in-line process monitoring, shielding can defect rates below 10 PPM are achievable in high-volume production.