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I often wipe the back cover of my phone with a wet napkin, and I often see that the rear camera will fog up. I didn’t take this seriously, but the phone camera suddenly couldn’t be turned on the other day. I thought it was a system update problem. Until today, my mobile phone suddenly couldn’t be turned on in the morning. I tried to charge the mobile phone, but the mobile phone did not respond. I also tried various key combinations and it didn’t work. What surprised me was that I was able to manually open the back cover of this phone without a heated back cover. I see a little water inside, so I suspect that the phone’s waterproof failure is causing this problem. What I want to ask is how to detect what is wrong with the phone? Is the motherboard broken or the battery broken so that I can further repair my phone. Thanks!—————————————UPDATED-V2—————————————————After I further disassembled the phone, I found that the motherboard had water in several places, as shown in the figure:

Several parts of the motherboard are obviously corroded and turned green. Can the motherboard be repaired in this situation? What should I do?—————————————UPDATED-V3—————————————————Unfortunately, I still cant’t turn on my phone after cleaning the motherboard.What should I do now?

@device_owner this “rear camera will fog up” and obviously this “a little water inside” would make me treat it as a water damaged phone. For now stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse.This may further damage your phone. The next thing to do is to clean it. Disassemble your phone using these guides Samsung Galaxy S10 Repair . You must remove all EMI shields from the circuit board. If you do not remove those, you might as well not do anything. After you removed those, clean the whole board, connectors and all with +90% isopropyl alcohol. Follow this guide , and even so it was written for a 3G all the points are still pertinent to your phone. While you clean your board, check for any obvious damage, like burned or missing components, corrosion on the board etc. When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Do not forget to replace the battery. This is a must and not an option. It will fail if you do not take care of it now. Once all this is done, reassemble your phone and reevaluate. Until it is cleaned, everything will only be a guess. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try. Change your cleaning habit and stay way from using “wet napkin” to clean your devices. Update 11/22/2021 @device_owner now it could be time to check out the function of the board. You did get all the components on the board properly cleaned and you do have a new battery? Start by following the flowchart

The PCB Layout will let you search for the components, like L8026, that need to be checked. Just use the search function of your PDF reader.