I had to create a printed circuit board for a project, using the home method (PCB developer solution, iron chloride.) At first, after the PCB was etched, I cleaned it very well using paper towels and isopropyl alcohol.
The PCB looked like this:
Then, I applied a thin layer of flux, hoping the soldering process will be better and the board will be protected a little. I used a flux dispensing pen because I didn't have any other kind of flux.
Here's the flux dispenser pen type I used:
Here's how the board looked after I applied the thin layer of flux:
I let it dry over night.
The next day, when I wanted to solder the components, I noticed that the soldering material wouldn't stick to copper, so I applied some more flux. Apparently, it worked, but some minutes later, the copper surface where I applied the flux turned green, with a dirty aspect:
Can someone help me with an answer, why did this happen? I assume it's the flux, but I'm not sure why.
Will the board be affected and in the end the traces will be destroyed?
Is there a solution to clean the dirt and protect the existing board?
Later edit: I tried to fix the damage already done by cleaning the PCB with isopropyl alcohol as well as I could, and it turned out pretty well, in my opinion. Here's a photo of the cleaned PCB:
It's been over a month and the board works well, I had no problem with the connections. The project I used the PCB for is an UV exposure box. I've put the PCB inside a plastic case, and the plastic case is inside a bigger wood case, also protected with extruded polystyrene. I hope this way the PCB will be protected from humidity. Also, the humidity in the laboratory where the PCB is located is controlled, always under 40%.
Thank you for all your help and good advice, I learned a lot from your answers.