Place the PCB board into the jaws of a vice. The vice supports the PCB and gives you the ability to keep both hands free.
Place a small amount of eutectic solder flux onto the PCB where you plan to install the BGA chip and reflow a BGA solder ball.
Place the BGA chip onto the solder flux. The solder ball is attached to the top of the BGA chip.
Position an infrared camera with built in thermometer so you can see a horizontal view of the BGA chip.
Turn on the butane torches and hold the torches in front of the camera. Adjust each torch until its heat output reads approximately 300 degrees Celsius.
Hold one torch above the BGA chip, then hold the other torch under the PCB board, below the BGA chip.
Watch the surface temperature of the PCB board and BGA chip until it reaches 300 degrees Celsius. You will see the solder become molten, which melts the solder onto the PCB board.
Turn off the butane torches and allow time for the PCB board to cool.