Reballing BGA chips tends to need and have a good steady hand, since most cellphone technician applied it manually by hands. It also requires good practice and experimentation before proceeding to reball any chips in mobile phones, because there are chips in mobile phones that can be easily damaged if you are not so familiar of doing it as well. like the CPU's and the Application processor chips are very vulnerable and can be easily damaged when applying unrecommended heat on it. I advice that spending much time to practice it with non working PC board and chips is a good way to start. To put thing straight up, in real life there are technician that are good re-baller and some have poor skills on it. that is what I observe mostly when attending many forums on the Internet. The truth is by practicing doing it is the key to enhance re-balling chips skills.
Re-balling Chips Methods
. Prepare the proper Tools -You need to prepare also proper reballing kits and a cleaning kits for further cleaning the PC board.
. A good and controlled hot air temperature, You need to refer to manufacturers manual for proper temperature settings.
Reballing BGA chips manually by hand skill, this tutorial video courtesy of onadbballais
Some technician used IRDA or Infrared Reworks Station and other reballing kit available on the market today. Practice by doing it everyday I assure you can do it yourself within just a few days.