Flux for SMD components?

Question

Do it yourself

Since the DIY topic is so popular on Habré, I will try to find out the moment that has been tormenting me for a long time.
What is the best flux to solder SMD components (the problem is most acute for LGA cases, since the contacts are untinned - yellow in them)? I tried:
1. just rosin - nothing is soldered
2. TAGS (glycerin) - soldered ±, but it is conductive and can only be washed off with hot water. After that, obviously, nothing works. However, it is good for them to tinker.
3. TT indicator non-cleaning for soldering SMD components (on vaseline). The title is a lie. He, the bastard, is also conductive, I only realized this on the third killed board. Soldering them, however, is very convenient, but then nothing works. For example, CP2102, soldered with it, reset all the time, and I could not wash it to the end.
4. Solder paste "Tinol": 40/60 PbSn suspension in rosin. It seems to solder well, but it is very difficult to dose it; as a result - jumpers in hard-to-reach places (for example, under the case). Maybe I'm DOING IT WRONG, but it doesn't work very well.
In addition, all of the above tends to bubble and blow small things off the board.
Please share your experience.

Answer 1

ASAHI WF6033 was used as a flux for tinning the board and chip (it was thoroughly washed off afterwards), and ASAHI QF3110A non-cleaning was used for sealing.

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