It is not a "googling" issue, but thank you for your time!
As you can see, me question above is "What is the liquid that we use to solder the processors and stuff on PCB (like the first video that i have in the first post)?"
I was asking if you could give me a name of this type of soldering paste.
Thank you
As
@(*steve*) noted, not everything labeled as "solder paste" (especially if it originates in China) actually has solder particles in it. And those that do contain solder particles vary widely in composition. In your first video, an excellent presentation of SMT re-work using a sub-heater under the PCB to heat-condition multi-layers, and a hot-air pencil to actually melt and re-flow the solder paste, there is no mention of the paste composition. Most SMT components are originally soldered using lead-free solder to comply with Euro RoHS standards. You can re-solder with a eutectic 63% Sn-37% Pb alloy or a 60% Sn-40% Pb (nearly eutectic) alloy that melts at a lower temperature and produces IMO a better joint. The problem is finding real solder paste with the desired composition.
Here is a website to get you started with a lead-free solder alloy paste you can apply from a syringe.
Beware of the Chinese solder flux shown in your second video. Who knows what its composition is? It could be highly active but leave a corrosive deposit. Some of this stuff was made for tin-smith soldering and has been re-packaged as "electronic solder flux". Unless you can verify that it contains pure rosin flux, it is best to avoid this stuff.
Not everything "made in China" is bad. Amtech is a multi-national firm that makes both flux and solder paste, leaded and lead-free, at factories in Asia and Europe.
Here is a link to their product line. Problem is, their target customers are large PCB fabricators who use the flux and solder paste in huge quantities. It can be difficult finding an
authorized distributor who will stock and sell in small quantities syringes of the Amtech product (if that is what you want) and guarantee it isn't an Asian counterfeit.
I really envy you if you can afford to purchase the
hot-air SMT re-work system shown in the first video. That's the cat's meow for SMT work! Most of us here use a pencil iron, tweezers, and a magnifying headset to solder a few pins at a time.