When soldering, please make sure that the temperature for Lead-Free/No Pb BGA chips is 245℃--260℃ (Maximum), Leaded/Pb BGA chips 180℃--205℃ (Maximum).
The soldering process is complicated. Soldering/replacing chips must be operated by engineers who have proficient skills.
As BGA chips are fragile, complicatedly structured, with numerous balls, any slightly faulty positioning, careless temperature-control, or incomplete cleaning PCB boards will result in insufficient soldering or missing soldering. The chips will, as a result, die.
BGA chips are easily get broken by improper soldering. Before buying, you should consider 3 points:
1) Have you bought the right chips?
2) Do you have the proper equipment?
3) Are you skilled enough to solder the chips?