What kind solder do you suggest me to sold BIOS chip to PCB? Hot fan gun of electric solder ? Watt ?

i haven't actually soldered a bios chip to a hard drive pcb but i do try my hand at electronic repairs and i can say i rather the hot air gun; you just have to get something(tweezers?) to hold the chip in place or the hot air might blow it away. also when using hot air you have to be careful of other nearby components. the solder iron is more precise i guess.

I suggest you to buy hot air soldering station.
You can find cheap one on ebay, see this for example:
http://www.ebay.com/itm/Aoyue-860-SMD-s ... 462410cf64

Search also for flux to get better soldering on SMD components.

_________________
My firmware database:
https://mega.nz/folder/O01DkBRI

I have an 862D based hot air/soldering station. actually over a year old and still works great.
one thing I did buy were some more very fine tips. with some research into them by measuring with vernies calipers and comparing to the fine ones on ebay, I got enough to last the next few years. I don't know how to gauge the quality of the tip but been using the same one for 2 months and as good as new. just use good tip maintenance, use flux liquid and buy the best fine 5 core solder. And practice if you need to.

A stereo microscope with 2x and 4x base and eyepieces such as WF10X/20, with a LED light ring will be a massive help.