Stamped Metal Shields and Enclosures: RF Performance and Cost
Short answer: a well-made stamped metal shield delivers roughly 30–60 dB of shielding effectiveness from 30 MHz to 1 GHz, and the number is set far more by apertures, seams and grounding than by the metal itself. A two-piece tin-plated steel can with a continuous solder seam can hold 60 dB and more; the same steel with an open cover seam can fall below 20 dB. Stamping is the cheapest route to that can — tooling typically runs $3,000–$20,000 and volume parts land at $0.02–$0.15 each — which is why most board-level shields you have ever seen are stamped parts.
Board-level shields protect an IC or a small module from radiated interference, and they stop that IC from radiating into its neighbours. The standard construction is a fence or frame soldered to the PCB ground plane plus a lid that clips on, or a one-piece can that is soldered directly over the circuit. Both are stamped from thin strip on progressive dies at hundreds of strokes per minute, then plated or used pre-plated. Understanding what actually buys you decibels keeps you from paying for copper where steel would do, and keeps your compliance test from failing on a detail no one drew.
What Actually Sets Shielding Effectiveness
Shielding works by reflection and absorption of the electromagnetic wave, and at board level the metal is rarely the weak link. A slot or an opening acts as an antenna: at 1 GHz the wavelength is 300 mm, and any aperture approaching a twentieth of a wavelength leaks energy you paid to contain. Seams between cover and frame are the same story — an open, ungrounded seam is effectively a long slot. Practical shielding performance is therefore decided by aperture size, seam continuity and how many contact points tie the shield to ground.
| Shield configuration | Typical SE, 30 MHz–1 GHz | Dominant loss factor |
|---|---|---|
| Open circuit, no shield | 0 dB (reference) | — |
| Solid continuous metal, soldered all around | 60–90 dB | Apertures and material |
| Production can, small vents + continuous seam | 40–60 dB | Seam and vent leakage |
| Production can, poor cover fit, large apertures | 10–25 dB | Cover seam, slots |
| Can with stamped grounding fingers, closed | 40–70 dB | Finger contact resistance |
The takeaway is not to chase exotic metals: first close the slots and the seams, then ground the can at short intervals. Cutting worst-case openings below roughly 1 mm at several GHz, and spacing ground contacts every few millimetres, does more for your margin than switching from steel to copper.
Materials: What the Can Is Made Of
Nearly every standard shield is tin-plated steel (SPTE): the steel gives stiffness and cost, the tin gives solderability and corrosion resistance. Brass and copper alloys appear where formability, thermal path or a specific soldering process matters; stainless appears when you need spring temper for integral fingers or a hard, corrosion-resistant surface.
| Material | Typical thickness | Why it is chosen | Relative cost vs SPTE |
|---|---|---|---|
| SPTE (tin-plated steel) | 0.15–0.40 mm | Solderable, stiff, cheap | 1.0× (baseline) |
| Brass C260 | 0.15–0.30 mm | Forms well, solderable | 1.5–2.5× |
| Copper and copper alloys | 0.10–0.30 mm | Highest conductivity | 2–3× |
| Stainless 304/301 | 0.15–0.30 mm | Corrosion, spring fingers | 2–3× |
| Nickel-silver / pre-plated alloys | 0.15–0.30 mm | Plating carried on strip | 2–4× |
Thickness above 0.2 mm is mostly for stiffness and handling, not RF. Skin depth in steel at 1 GHz is a few micrometres, so a 0.2 mm wall is electrically thick at every frequency you will shield in a product. Pre-plated strip also removes a whole finishing operation and its handling risk — a topic covered in our guide to stamped contact plating when the plating has to survive forming without cracking.
Frame and Cover, or One-Piece Can?
Two-piece construction — a frame soldered in reflow, then a lid clipped or laser-welded on — dominates production because it gives test and rework access: the lid comes off, the circuit is probed or reworked, the lid goes back. One-piece drawn or bent cans are cheaper to assemble and give a cleaner seam, but once soldered the component inside is sealed. Depth is also a real limit: drawn cups over roughly 5–8 mm depth at 0.2 mm wall start thinning corners, and that is where designers switch from one-piece draws to frame-and-cover.
| Construction | Access for rework | Assembly cost | Seam quality | Typical use |
|---|---|---|---|---|
| Frame + clip-on cover | Full | Low–medium | Depends on fit | Modules, general ICs |
| Frame + laser-welded cover | None | Medium | Best | Sealed modules, RF cans |
| One-piece drawn/bent can | None | Lowest | Good | Simple low-cost shields |
When a cover must stay shut under vibration or must contact the frame around the whole perimeter, the lid gets stamped spring fingers or the frame gets dimples. That contact-force engineering is shared with grounding clips and contact springs — see our EMI shielding contacts guide for the finger geometry side of the same problem.
Why Stamping Wins on Cost
The economics are simple: a shield is a thin shell with a large surface-to-volume ratio, and stamping is the cheapest way to make thin metal shapes in volume. A 20 × 20 × 3 mm two-piece shield uses a few grams of 0.2 mm strip; the same box machined from solid would cost more in material and minutes than the stamped part costs in thousands. Progressive-die stamping runs these parts at 200–800 strokes per minute, and each stroke produces a finished shield or a finished half of one.
Indicative numbers help with budgeting: a simple one-piece shield die may run $2,000–$6,000; a two-piece frame-and-cover with drawn features, dimples and tight flatness typically runs $6,000–$20,000; large multi-station dies with in-die forming push higher. Piece prices of $0.02–$0.15 are normal at annual volumes above 100,000 per part number. Below that volume, hard tooling stops making sense and the parts are better folded from sheet or machined as prototypes — the crossover logic is the same as the general metal stamping process discussion.
What to Put on the Drawing
Die shops quote what they can measure, so the drawing decides both RF outcome and price. Give the material grade and temper, the exact strip thickness, plating (tin, tin-lead-free, nickel, or bare), and the maximum acceptable burr side and height. Tolerances of ±0.05 mm on blanked outline and ±0.1 mm on formed features are routine on our progressive-die lines; flatness on thin covers is worth calling out explicitly because 0.2 mm strip will not be dead flat without coining or stress relief. Mark which apertures are functional and which are decorative, state the seam or grounding requirement, and flag any surface that must stay plating-crack-free after forming.
That drawing is also the fastest way to a real number. Send it to sc@bquq.com or WhatsApp +86 13713157787 and you get a stamped-part quotation within 12 working hours — including a straight answer on whether the shield should be stamped at all, or whether a stamped enclosure is better folded, drawn or machined for your quantity.
Frequently Asked Questions
Q: How much shielding effectiveness does a stamped metal shield actually provide?
A: In production, expect 30–60 dB from 30 MHz to 1 GHz for a normal two-piece can with small apertures and a continuous seam, and 60–90 dB for a fully soldered continuous enclosure. Falls below 30 dB usually trace to open seams or large apertures, not the metal.
Q: What is the best material for a stamped RF shield?
A: Tin-plated steel (SPTE) at 0.15–0.4 mm is the default for most boards: it is stiff, solderable and cheap, and skin depth makes thickness irrelevant to RF. Use brass or copper for special solderability or thermal needs, and stainless only where spring fingers or corrosion resistance matter.
Q: Does shield thickness affect RF performance?
A: Almost never. Skin depth in steel is a few micrometres at 1 GHz, so any 0.1 mm-plus wall is electrically solid. Thickness is chosen for stiffness, handling and dent resistance, not decibels.
Q: How much does tooling for a custom stamped shield cost?
A: Indicatively $2,000–$6,000 for a simple one-piece shield die and $6,000–$20,000 for a two-piece frame-and-cover progressive die with forming. Part price then runs $0.02–$0.15 at high volume, which is why stamping beats machining or die casting for shields above roughly 100,000 pieces a year.
Q: When should I choose a one-piece can over a frame-and-cover design?
A: Choose a one-piece can when assembly cost and a clean seam matter more than access, and when depth is modest. Choose frame-and-cover when the circuit needs test or rework access after assembly — the lid unclips and the board stays usable.
Related Resources
- EMI shielding contacts guide — grounding clips, finger springs and contact cans that close the seam on stamped shields.
- Stamped sheet-metal enclosures — the shield cans, frames and enclosures BQUQ stamps on progressive and line dies.
- About BQUQ — ISO9001-certified source factory in Dongguan running stamping, CNC, springs and heat sinks under one roof.
- Contact us — send the drawing and receive a stamped-part quote within 12 working hours.
Authored by the BQUQ Engineering Team. BQUQ is an ISO9001-certified source factory in Dongguan, China, running CNC machining, metal stamping, custom springs, heat sink and collet lines under one roof. Send drawings to sc@bquq.com or WhatsApp +86 13713157787 for a quote within 12 working hours. www.bquq.com
