[Lite] Need some advice, I can't have this happen again

I purchased a “for parts or repair” Nintendo Switch Lite board from ebay which has a ripped pad at the BQ area. Typically I tend to make some bridges when I use my solder tip with lead-based solder wire, and because that area is crowded with big and microscopically small caps, I decided to use a solder paste to make the job less complicated – only that it actually made it even more complicated because this happened:

I had solder paste well rested (sitting idle for almost 2h at room temp) before using it for this job, my soldering iron tip was set to >350C (around 400C), but as soon as I went over it with the tip, the solder almost immediately melted down deeply into the board and I cannot remove it using a wick. I cannot remove it at all.
So my question is this, which tool should I replace so that that doesn’t happen again? I’ve used this solder paste before, and that never happened, as far as I remember.
The one thing I changed was the flux. It’s now a Mechanic 559. Solder paste is a Mechanic XG-50. Soldering iron is over two years old, I do have some difficulties even when trying to wick the remaining solder off of the board. I do tin the soldering iron tip before using it for anything, but that doesn’t seem to be doing much in terms of performance, so what should I do? I could use your help. TIA

Hi, i think i saw a similar issue on a video posted by STS telecom from a repair on a iPhone board he was making and the previous repair shop used solder paste and it really did a mess more than it solved issue.
I guess you need to sort out the iron issue before thinking about the solder tweaking. I also have some issues with mine, i opened a thread in the tools/equipment section, might be interesting for you as well.

Those pads are meant to be joined. It looks like you may have removed the solder mask between them but it doesn’t really matter as they are the same pad.
Are you trying to do this just with a soldering iron?! You will need a hot air gun to get a chip like that on.

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It took me some time, as I’m entirely new when it comes to micro soldering, but I believe I’ve managed to get to know about the issue being discussed in this thread. According to this vid youtu.be/swls2yukYjs?t=14 dendrite has formed on the board because I had flux sitting on it for far too long and it could cause current leakage, not to mention the chance of a short.
I don’t feel like risking it, as I don’t have any other spares on me, so I’ll be using this board for parts. I just wanted to share this with whoever is watching this thread or unfortunately comes across this issue. Lesson here is do not leave flux sitting on the board, or this shall happen and there’s no restoring it - as far as I know.

Ignore this, for the most part it’s marketing wank, leaving a no clean fux on a board will not cause the issue you were seeing… flux activates at high temperature (read a no clean flux datasheet for more info) and while some more agressive fluxes can cause tarnishing or minor corrosion on copper/component endcaps, the results are minimal and would take a minimum of weeks to months to appear, non will cause errosion of a solder mask like in your case and flux is not conductive nor will it cause “current leakage” atleast not in any meaningful way… Listen to what @Insomniac has told you, I 100% agree

You stripped the solder mask off as a result of one or two things, your iron either wasn’t hot enough and/or you were to rough in the process (likely a combination of both) or you attempted to wick the pads, your iron wasn’t hot enough and/or you were too rough while wicking (likely a combination of both) and your wick has acted as a really great abrasive (think kitchen steel scouring ball) In future your wick should almost float over the surface and suck up the solder with minimial downward pressure, if it isn’t your not using enough flux and not enough heat, if your iron is struggling have your hot air help out at approx 140C while wicking/tinning the pads (for reinstallation with hot air after)

Again, as Insomniac suggested, you’ve only taken of the surface solder mask and the pads are supposed to be joined below… It’s completely unnecessary but if you wan’t it to look pretty you can apply UV solder mask over the over-exposed pads and cure… but again it’s not needed… it would be a shame to use this for parts given that there is nothing wrong with it.

Thank you for posting, I had no idea those pads were the same and meant to be joined. Before you posted, all I had was a mere commercial so I bought into that because it was my only reference that mentioned the exact problem I ran into.

I have used solder paste many times and have never used additional flux on the board. The paste is mode up of flux and solderballs so nothing extra is needed. Karl