Dead iPhone 5S after water damage

Hi out there!

I just bought a water damaged iPhone 5S from a friend. He had the phone in a zip lock bag on a canoe trip and unfortunately condensation got into the bag. From what i heard from him, he tried to dry it somewhere warm, but the phone was completely dead.

I have taken the phone apart, and cleaned off any corrosion on the logicboard using 99% Iso alcohol, but still there is no life. I have now removed all EMI shields, and found a little corrosion under these too, which I have also cleaned, but there is still no life :(

Anyone have some tips for what i can try to revive the phone?