Quick answer: An EMI Shielding Case is not the default answer for every screening job. Above 80 dB, behind a service door, or at a 300 mm cavity with four-figure volumes, folded steel, die-cast aluminium or extruded frames usually win. The rotomoulded route pays off outdoors, in frequent handling, with odd cavity shapes and runs of 50 to 500.
Table of contents
- The Real Rival Is Not Another Plastic Box
- Four Routes, Four Territories
- Four Cases Where the Shielded Case Is Wrong
- Turning the Trade-Off Into One Ledger
- FAQ
1. The Real Rival Is Not Another Plastic Box
Buyers put an EMI Shielding Case next to a plain rotomoulded box and conclude the price is a rip-off. The comparison is wrong: a plain box has no conductive layer, no gasket and no ground point, so the two are not the same product. The real alternatives to an EMI Shielding Case are folded sheet metal, die-cast aluminium and extruded frame builds.
| Route | Typical screening | Unit weight | Sensible volume | Weak point |
|---|---|---|---|---|
| Rotomoulded, conductive coating | 40 to 60 dB | 5.8 kg | 50 to 500 units | Falls short at high frequency |
| Folded steel with gasket | 60 to 80 dB | 11.2 kg | from one unit | Heavy, slow to assemble |
| Die-cast aluminium | 70 dB and up | 8 kg | 1,000 units and up | Tooling cost, frozen shape |
| Extruded frame panels | 50 to 65 dB | 9 kg | from 10 units | Many seams to bond |
No route wins across the board. The rotomoulded type wins on impact resistance, non-metallic build and free cavity shape, and loses on high-frequency attenuation and serviceability. Steel is the mirror image.
2. Four Routes, Four Territories
A folded steel box in 1.2 mm cold-rolled sheet, closed with a conductive gasket and 24 screws, reaches 70 dB without much effort. The bill: six minutes of assembly per unit, plus sharp edges. This route holds the single-unit, cabinet-style job that needs a door for maintenance.
Die-cast aluminium holds high volume. Tooling is paid once and unit cost falls with quantity, which makes sense above a thousand units a year; change the cavity, cut a new die.
Extruded frames hold large sizes and knock-down shipping. Profiles are cut, corner blocks join them, and the box travels flat. The price is many seams, each needing its own bond.
The rotomoulded EMI Shielding Case holds the outdoors. One-piece moulding means no weld line, so drops, rain and salt fog are survivable, and the cavity can be any shape the tool allows. Fifty to 500 units is its comfortable band, with a 12-day sample turnaround.
3. Four Cases Where the Shielded Case Is Wrong
- Above 80 dB, or coverage to 10 GHz. Coating sheet resistance sets the ceiling; folded steel with a double gasket is cheaper.
- One unit, or three, with a service door. Two latches every time is fine in the field, painful on a bench.
- A cavity under 300 mm at four-figure volume. Die-cast lands near 60 percent of the unit price, and moulding offers nothing there.
- More than 40 open-close cycles a day. Gasket fatigue arrives early, and a year of spares costs more than a steel body.
- Heat load above 200 W in a sealed box. Waveguide vent area runs out and temperature drifts toward condensation.
The first four are cost arguments, the last is physics. When physics says no, changing the route is cheaper than redesigning the box.
4. Turning the Trade-Off Into One Ledger
The ledger is simple: volume times unit price, plus tooling, plus three years of maintenance, divided by service life. Most projects compare only the first term, which is why moulding looks expensive at 300 units.
| Item | EMI Shielding Case | Folded steel box |
|---|---|---|
| Unit price at 300 pcs | CNY 680 | CNY 520 |
| Tooling | CNY 45,000 | CNY 8,000 |
| Sample lead time | 12 days | 5 days |
| Unit weight | 5.8 kg | 11.2 kg |
| Assembly time | 40 seconds | 6 minutes |
| Screening at 1 GHz | 55 dB | 75 dB |
| Neutral salt spray | 240 h | 72 h |
Run the numbers and the gap closes: at 300 units totals differ by a bit over ten percent, and at 500 they level. The difference moves to the shop floor. Forty seconds against six minutes saves more than forty labour hours across 500 units. Five kilograms per unit changes freight and handling. A gasket set every three years at CNY 200 each is easy to forget. What the EMI Shielding Case sells is the process it removes, not the box.
Conclusion
An EMI Shielding Case is a trade, not a default: weight for impact tolerance, high-frequency margin for shape freedom. Above 80 dB, behind a door, past a thousand units or under a heavy heat load, the money belongs in steel or die-cast. Outdoors, in constant handling, with odd cavities and runs of 50 to 500 units, the ledger favours the EMI Shielding Case.
This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.
Related Reading
- Writing the specification sheet for a shielded case
- Industry requirements compared across the same box
- Hard shell case material comparison
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