Apply some BGA Paste Flux to cylinders around the edge and get the upper layer in position.

Heat evenly with Hot Air Gun at 350℃, air flow 65. The soldering process is finished with the upper layer sinking and Paste Flux overflowing.

Wait for the motherboard to cool for 5 minutes. Now, let's assemble the phone and test. Go to Settings>Sounds&Haptics>Ringtone. Select a default ringtone, normal output sound this time.