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What does the process of physically removing the wifi/bluetooth module look like for a Raspberry Pi 4? How hard it is for a beginner & for someone experienced with soldering? And how likely it is to damage some neighbouring component?

I don't care to save the module for re-use later on, just want to get it off even if that means damaging it.

This is for an air-gapped device, so physically unavailable hardware is much better than hardware disabled by software. I read this answer on a similar question but the one of RPi4 looks bigger, not sure how it looks under that metal shield. Couldn't find a guide on the same.

Evaluating RPi4 over other models which lack WiFi/Bluetooth capabilities purely on the basis of performance. CPU even though is only a little better, but memory seems to be a lot faster than any other models.

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    @Milliways So everyone who has ever done anything had the equipment for it beforehand?
    – Ashfame
    Jul 24, 2020 at 0:06
  • It seems unlikely that you'll find a "tutorial" on this :) The old phrase "Just do it" comes to mind. A few days ago I might have suggested that you consider a device like the "pocket beagle" - but my short experience suggests it sucks.
    – Seamus
    Jul 24, 2020 at 0:24
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    If you try it and it goes wrong your experiment will have cost USD$50 as you'll need a new RPi. If the WiFi chip is SMD use a sharp Xacto knife to cut the pins close to the chip and leave it mounted otherwise. If it's a BGA chip you'll need to use a hot air gun.
    – Dougie
    Jul 24, 2020 at 7:02
  • Thanks Dougie! As per cypress.com/file/348636/download it seems to be 140-ball WLBGA I am going to attempt Dmitry's short-circuit method below. Thanks Seamus!
    – Ashfame
    Jul 24, 2020 at 10:03
  • Before you go nuts attacking your Pi have you tried putting the Pi in a metal enclosure? That might be enough to block any wireless signals. As has been mentioned you will be lucky to find a tutorial specifically on the process of removing the Wi-Fi/Bluetooth module. Having a look it appears to be all surface mount components. So any tutorial covering the removal of those would be a starting point.
    – Darth Vader
    Jul 24, 2020 at 12:45

2 Answers 2

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If you want to physically disable Wifi/BT, the easiest way is to disconnect the antenna, or short the antenna output to ground via a 1nF capacitor.

enter image description here

The capacitor is there to avoid having an actual short to ground, which could blow the chip up. 1nF is only 0.06 Ohm at 2.5GHz, so for RF purposes it's as good as a short. A typical antenna impedance is 50 Ohm. Having a 0.06 Ohm path to ground means that only about 0.1% of the transmitter signal will reach the antenna, while 99.9% will be lost. That's about 60 dB attenuation.

Considering the WiFi signal already starts at about -30dBm, attenuation by another 60 will bring the signal down to -90 dBm, which is barely above the thermal noise. This means a few meters away from the device (another -10 dB), you won't be able to receive the signal even theoretically.

Removing the WiFi/BT module is trivial with the right equipment (heat up the board and lift the shield and the IC up with a vacuum pen), but without a schematic I would not give you any guarantees that the rest of the Pi will work once the WiFi chip is gone. And even if the schematic is released, it would be quite a task to analyse it and create a modified device tree for the kernel to correctly understand the new hardware configuration.

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  • I was trying hard to find that antenna on RPi 4, was about to ask you if you are sure the image is right :)
    – Ashfame
    Jul 24, 2020 at 8:26
  • This is 2-fold problem, as this being an open source project, I am not just doing it for myself but also asking others to do it as well. So whatever is the easiest and gets the job done with certainty is preferred. But how can removing a component without physically damaging nearby components even affect the rest of the board?
    – Ashfame
    Jul 24, 2020 at 8:28
  • Hopefully it gets clear with the right picture. I bet cutting that trace with an exacto knife is by far the easiest way. And yes, removing components can affect the rest of the board, electronic is not really like Lego but rather a bunch of loops in which current is flowing, and removing parts breaks those loops, so the current has to stop or go elsewhere. Jul 24, 2020 at 8:33
  • OK, I trust you to know this a lot better than I do. So cutting with an exacto knife or shorting antenna output seems like 2 easy choices. In your screenshot, are you red arrows pointing towards those blobs of solder or the path?
    – Ashfame
    Jul 24, 2020 at 8:36
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    Thanks a lot for your guidance! I will circle back in a couple of weeks when I would have received my order & attempt to do this :)
    – Ashfame
    Jul 24, 2020 at 9:59
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I desoldered the wifi chip with hot air gun and Rpi seems to be working just fine. Also disabled wifi and BT in /boot/config.txt (maybe not necessary).

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  • Can you be a bit more clear on how you did that? A normal soldering iron probably won't work.
    – PMF
    Nov 4, 2021 at 7:30

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