Hi, friends.
I received my brand new Arduino Nano RP2040 Connect and noticed there was flux residue on the board, so I decided to clean it with rubbing alcohol.
After that, the microphone stopped working.
I read the documentation and didn't find any warning against alcohol use.
Can the damaged microphone be changed for a new one?
Any help?
Thanks in advance,
Alexandre
Confusing post because you cleaned a Nano board and have failed microphone. What did you actually do? and to what?
Rubbing alcohol is a solution of IPA, isopropol alcohol, and water. Unless you have the microphone attached firmly to the board and put the whole thing in a container of alcohol, there is nothing that can affect the microphone. How did alcohol get into the microphone?
Unless your Nano has been soldered after it was manufactured, by someone using resin flux, there is nothing alcohol can clean. The Nano was made using lead-free solder paste with an organic flux that leaves a water soluble residue. It is cleaned with hot water, only.
Your microphone should NEVER be cleaned.
None of my Nanos have a microphone. How did yours get one?
Paul
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As indicated in the post title, I'm talking about the Arduino Nano RP2040 Connect, which has a MP34DT05 microphone on it.
Isopropyl alcohol is commonly used to clean the flux off circuit boards. I found out the hard way that this shouldn't be done with the Arduino Nano RP2040 Connect.
If anybody knows how to fix it, or where to buy a replecement MP34DT05, please let me know.
Usually when boards have components like microphones or buzzers that are designed to be washed after soldering, they are made with a removable sealing sticker to keep water out. That seal is removed after manufacturing.
So that probably explains how alcohol got into it.
As a general rule, you shouldn't need to wash any commercially produced board. It's either already been cleaned or it doesn't need to be. As you found out the hard way, doing that can cause problems. The microphone probably isn't rated for exposure to alcohol.
[edit]
That mic is MSL3 moisture sensitive according to the datasheet, so it's not designed to be washed after reflow. They're most likely using a no-clean paste.
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I use 90% IPA for cleaning boards and I've found you have to either blot the board or use a lot of alcohol to get the flux off the board (as opposed to remaining in the alcohol and landing on a different part of the board)
Assuming alcohol got into the MEMS mic I would leave it somewhere warm and hope whatever got in the mic evaporates out.
As for buying a replacement MP34DT05 I would try to get samples from ST. However physically replacing the part is not for the faint of heart.
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I don't like flux left on my board(s). I realize it is probably a low activity flux (aka no clean) but still I like to see clean boards.
If the board has no at risk parts (like the mentioned microphone) I was in denatured alcohol (ethyl alcohol) from Home Depot. I blot them dry with Kim wipes (less lint than paper towels). Sometimes I clean them in hot water with dish soap. Then rinse them real well.
I have also "spot" cleaned areas of the board that has had some hand soldered larger parts.
This is especially true if I plan to conformally coat the board.
FWIW I've been working in electronics for decades. And feel comfortable cleaning as described. I will agree that it is unnecessary for most folks who are using the board(s) indoors. And unless you are comfortable cleaning like this the you should probably leave the boards as received.
And I was wondering why it came sealed with coloured moisture indicator pads inside
There's an idea! allow the board to sit in a container full of rice (keep rice dust from the mic opening).
Digikey
Mouser
https://www.mouser.com/Sensors/Audio-Sensors/MEMS-Microphones/_/N-98yda?Keyword=MP34DT05&FS=True
Might have to wait a while.
99.9% ISOPROPYL ALCOHOL for cleaning.
I use MG Chemicals brand, my "local" electronics store (45 minute drive) has it in gallon bottles. I refill my little cleaner bottle with a pop-up lid from it, so the gallon is closed most of the time and not absorbing water from the air.
At that concentration, it is extremely flamable.
Paul
Not really familiar with 99.9% Isopropyl. I was guessing the OP likely used 70% but may have had 90%. Very few hobbyists bother to get 99+%. I personally have (in an unscientific manner) had better results with ethanol. I also sometimes blow the still wet ethanol+flux off the board with my compressor. I can already hear folks screaming about ESD. I've had no issues to date and I have 7 devices (soon to be 8) running in my home 24/7 for a couple of years with no issues to date.
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The rice bath didn't work. I guess I'll have to change de microphone.
Or just use it as one with a dead mic and get a replacement for a lot less frustration.
I don't have open flames, or a hot iron, around when I clean boards.
And if warm enough out, an open window.
11 years so far with no issues.
I've just ordered a new board. This time I'll live with the flux residue.
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Flux can be effectively removed locally with a ‘Q Tip’ and IPA.
I routinely use Acetone on stubborn areas (test on surfaces first) with a Q Tip.
Sparingly of course.
If submersion is needed, components that can be damaged should be removed or sealed prior to cleaning, use appropriate tape like Kapton etc.
Drying could take some time. Not sure it will actually help but longer is better.
If I had a Nano RP2040 and was unhappy with the flux on some of the solder joints I would put a piece of scotch tape over the hole. Being very careful not to change the temperature too much, so as to not stress the Mic with pressure changes.
Then I would clean it locally being sure not to get the scotch tape wet with cleaner. I would purchase some stiff bristle tooth brushes and use them to scrub the offending area.
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