Short answer: leave the can on. It is a soldered RF shield worth on the order of 20 to 40 dB of board-level isolation, and a WROOM-class module keeps transmitting without it — on a quiet bench. In a real panel the same removal costs you receive margin and sprays the module's own noise onto your traces. It also takes the module's FCC approval, because that approval covers the radio exactly as the maker shipped it. When height or probing is the problem, the same radio is sold without the can. When weak signal inside a metal box is the problem, the box is the part to change.
What the can is doing under there
The can is a thin metal lid soldered down to a ring of ground pads around the module's perimeter. It covers the radio die, the flash memory and the power converter, while the antenna section on most canned modules sits outside it, in the open. Bonded to ground, the lid works as a small Faraday cage with two jobs. It keeps the hash from your drives, switching supplies and relays off the module's receive path. It also keeps the module's own harmonics inside, off your board and out of the emissions measurements the maker had to pass.
What 20 to 40 dB of shielding is worth
Decibels are a power ratio, so the numbers compound fast: 10 dB of shielding cuts coupled energy to a tenth, 20 dB to a hundredth, 30 dB to a thousandth.
| Isolation the can gives | Interference energy still coupled |
|---|---|
| 10 dB | 1/10 |
| 20 dB | 1/100 |
| 30 dB | 1/1,000 |
| 40 dB | 1/10,000 |
A soldered lid over a 2.4 GHz module holds roughly 20 to 40 dB against board-level coupling — typical figures for this kind of shield. That coupling is near-field: magnetic pickup into the loop areas of your traces, the same physics that sets a 134 kHz reader coil apart from a classical antenna; near-field physics versus classical antenna theory covers it in depth. Shield vendors also offer absorber-lined lids, where the absorber damps the cavity instead of only reflecting. That lowers the cavity's Q factor and cuts resonance risk at the top of the band.
What changes when the can comes off
- On a quiet bench, almost nothing. The antenna lives outside the can, so transmit power and pattern barely move, and the link still comes up.
- In a real panel, receive margin shrinks. The noise the lid was rejecting lands on the receive path, and effective sensitivity drops by whatever that noise is worth. The module never reports a worse sensitivity figure; packets just start retrying.
- Your board gets noisier. The module's clock, flash bus and regulator harmonics now couple straight into the nearest traces, usually the analog ones you were protecting.
- The removal is its own risk. The seam is soldered at the perimeter, and prying under the edge lifts the passives beside it. If a part is already dead and you want the view, lift the seam with hot air rather than a blade.
The certification line
A modular radio is approved as a complete assembly. The FCC grant that lets a product ship with that module inside covers the radio exactly as the maker built it, can included. Unsolder the can and you are running an uncertified transmitter, which is fine at your bench and nowhere past it. The clean route already exists: the same radio is sold as an uncanned variant, with its own approval and its own mechanical drawing. Buy that variant when you need the height or the access, and the certification question never comes up.
Where your enclosure fits
The can is the second shield in a stack of two, and yours is the first. A sealed metal enclosure stops 2.4 GHz almost entirely, so weak signal inside one is the box's doing, not the can's. Fix the RF path instead: a pigtail to a bulkhead antenna outside, or the module behind a plastic face or window. Planning the antenna path out of a metal enclosure covers the first option, and radio signal through a metal enclosure compares the approaches. For the window route, a WiFi antenna behind a plastic enclosure face and what plastic does to an RF signal give you the placement and loss numbers.
Keep the wall rating in mind when you cut that hole: the enclosure's type is only as good as the weakest part in the wall, so the gland or window carries the same rating as the box. Our enclosures are rated NEMA 4X / IP66 by the manufacturer; not UL listed. The cutouts, glands and HMI windows guide shows the hole sizes that match standard glands.
A worked example with the numbers
Weak-signal levels quoted in RF shield testing sit around -92 to -93 dBm, so call your received signal -92 dBm. Now put a switching supply in the same panel and assume its hash couples -75 dBm onto the receive path with the can off. That -75 dBm is an assumption for a nearby supply; replace it with your own measurement.
Without the can, the noise sits 17 dB above the signal (-75 dBm against -92 dBm), about 50 times more noise power than signal. The link is dead. With the can's 30 dB — mid-range for a soldered lid — the coupled noise falls to -105 dBm, which is 13 dB below your signal, roughly 20 times more signal than noise. Same radio, same distance, same noise source: 17 dB underwater, or 13 dB clear. That lid is the difference between a link that retries all day and one you forget about.
The decision, case by case
| Why you want the can off | What to do instead |
|---|---|
| Probe test points, watch the LEDs | Order the uncanned variant of the same radio |
| The lid will not close over the can | Use the uncanned variant; its drawing gives the lower height |
| Weak WiFi inside a metal box | Keep the can; change the box — bulkhead antenna or plastic face |
| The board needs conformal coating | Keep the can and mask it, per masking a shielded module for coating |
| The module is dead and you want to look | Lift the can with hot air, at the bench, and keep that part off any job |
What to specify when you order the box
Send the module outline with your enclosure drawing: window or cutout position, antenna keep-out, and the face material across the RF region. A stainless box with a plastic-faced window over the module keeps the can on and still lets 2.4 GHz out. A metal face with a bulkhead antenna does the same with the whole radio inside. Both start in the custom enclosure builder, where you set material, size and every cutout, with delivery in 10 business days anywhere in the world, counted from your approval of the drawing. If the box choice is still open, the enclosure selector walks it by environment and inside dimensions. Either way, the can stays where the maker soldered it.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 10 × 8 × 6 in | 304 stainless | 10 x 8 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Will the WiFi still work if I remove the shield can?
At the bench, yes: the antenna sits outside the can on most modules, so transmit power and pattern barely move. What you lose is the 20 to 40 dB of isolation the lid gave you, so in a panel with drives or switching supplies the receive margin shrinks by whatever that noise is worth — often the whole link.
How much isolation does a shield can actually give?
On the order of 20 to 40 dB against board-level coupling at 2.4 GHz — typical figures for a soldered shield lid. Because decibels are logarithmic, 30 dB means about 1,000 times less coupled energy and 20 dB about 100 times less. What it mostly fights is near-field pickup into your trace loops, not distant radio signals.
Does taking the can off void the module's FCC approval?
Yes. A modular radio carries its FCC approval as the maker built it, can included, and a module you have modified no longer matches that approval. Keep modified radios on the bench. For anything that ships, use the module as bought or order the maker's uncanned variant, which carries its own approval.
Is the shield can connected to ground?
Yes. The lid is soldered to a ring of ground pads around the module's perimeter, and that bond is what turns a piece of metal into a shield. It is also why prying it off is rough on the board: the seam holds at every pad, and the parts beside the can come up with it.
Can I conformal coat the module with the can on?
Yes, and that is the right way round. The can is a sealed metal lid over the RF section, so coat the board with the can in place and mask its seam so nothing wicks under the edge. Keep the antenna section clear of coating, because a film over the antenna can detune it.
