This is probably not "new" but has been soldered into some pcb in the past from where it has been removed with hot air or in a solder bath.
We don´t know if it has survived this procedure and if it´s still workin at all.

I´m afraid just using a soldering iron and a good flux (plus spending some considerable time) will not remove the solder completely enough so you can insert it into a regular socket.
My first idea was to use some acid that dissolves the tin but leaves gold undamaged, but it would probably damage the ceramic CPU-body as soon as it gets in contact.

I am surprised as it's certainly socketed CPU. Were they also soldered?

I don't need to clean every pin, so I'll try desoldering wire. There is nothing to lose anyway.

I also have a TI 486dx-2 that was once directly soldered in a PCB. Must have been in a laptop or something.
Unfortunately it is very difficult to get rid of the solder remnants on the pins.
Trying to "clean" it with some solder wire and flux is the best you can do, afaik. But don't heat up the individual pins too much.

Yes, Good solderwick will be a way to remove the too much of solder left on the pins.

Will try. Do I need additional flux or there is enough one that is on wick?

depends on the wick,
Good solder wick tends to have some flux and is a braid made from very thin wires, like hair thin.
I once bought a few rolls of wick from china and they were horrible, thick wire, no flux.

rkurbatov@gmail.com wrote on 2022-01-17, 16:55:

Will try. Do I need additional flux or there is enough one that is on wick?

If you are lucky the flux on the wick is sufficient. Flux also acts as thermal transfer agent (like heatsink compound), helping to get the pins hot enough so the solder melts faster and flows into the wick. So even if you happen to have good and fresh wick with enough flux it readily takes molten solder, extra flux might help melting the solder. If you have extra flux at hand, give it a try. Make sure you are using electronic grade resin-based ("acid free") flux, preferably no-clean flux. While amonium-chloride based flux is chemically very effective, you get hydroscopic residues that tend to get conducting. Don't use flux like this on electronics unless you plan very thourough cleaning of everything touched by the flux.

Thank you, guys!

That's a fairly common CPU, IMO it's not worth the risk of screwing up the motherboard CPU socket if some solder remains on the pins.

Yeah, I gave up in a while and ordered another one.

I've bought a desoldering tool (not the manual one but one with heater and a small pump) - and it worked. Despite I treated it so badly, I managed to remove most of the solder and straighten the pins. Will test it, for sure, but to my surprise the system booted with it.