this is something i didn't realized before but i think that this is my main problem: the placing of the ic in the perfect position. how do you do it? just with a microscope and tweezers? sometimes i lost even 5 minutes to put it in the right place and it isn't never 100% perfect
- If you get a chance to solder using a stereo microscope you will be astounded how good you can solder.
I use the solder paste that the OP mentioned, and a converted toaster oven (ControLeo2 control module and toaster oven mod kit, on the recommended toaster oven). Works great as long as I use stencils to apply the solder paste - I was never able to find solder paste that worked well from a syringe; I tried several. I use tweezers and good lighting to place the parts; I have not found part placement to be problematic when there's a nice even layer of solder paste from a stencil - I suspect your difficulty is partly because when solder paste is dispensed manually, you don't get an even layer of it.
the paste kind is not important I am using plumbers soldering paste is much cheaper for long time.
I only have a 90x scope,
I wouldn't suggest plumbers on anything unless you want the green rot. Use rosin core solder and flux, or formulas specific to electronics
this way you wouldn't need to move the base for every parts