In mobile phone repair, when using a hot air blower to heat the chip, a series of standardized operations must be followed. The following are the specific methods:
Pre-preparation and component protection:
Observe the layout of components around the chip and place water-soaked cotton balls on the adjacent IC to prevent damage from high temperatures. For components such as plastic power amplifiers and soft-packaged font libraries that have poor high-temperature resistance, special attention should be paid to controlling the blow-soldering temperature.
Evenly apply an appropriate amount of flux on the surface of the chip to be disassembled, ensuring that the flux fully penetrates to the bottom of the chip to help the solder joints melt evenly.
Hot air blower parameter adjustment
Set the temperature (300-400℃) and air volume (2-3 levels) according to the chip type, and keep the air nozzle 2.5-3cm away from the chip surface.
When heating, rotate the air nozzle evenly in a clockwise or counterclockwise direction to avoid local overheating of the chip caused by concentrated heating.
Chip disassembly operation
Continue heating until the tin ball at the bottom of the chip is completely melted (about 30 seconds to 1 minute), during which use tweezers to gently touch the edge of the chip to confirm the solder state.
When the chip starts to shake, keep the hot air gun heating continuously and simultaneously lift the chip vertically upward with tweezers to avoid the solder re-solidifying due to pauses.
Pad processing and cleaning:
Immediately after disassembly, use an anti-static soldering iron to remove the residual solder on the circuit board pads and replenish an appropriate amount of solder to make the solder joints smooth and round.
Thoroughly clean the flux residue on the surface of the chip and circuit board with thinner to prevent the corrosion of the solder pads.
Processing of chips with sealant
For potting compound chips, first cover the chips with a cotton cloth dipped in the de-potting solution and soak until the potting compound softens (3-4 hours).
Adjust the hot air gun to a medium air volume of 300℃, and gently lift the sealing glue with the tip of the needle. After the tin ball at the bottom melts, separate the chip with a blade.
Welding process control
Apply flux to the solder toe surface of the chip and preheat and position it by using the “tin ball reset” process.
When soldering, keep the hot air gun vertically aimed at the center of the chip, and slowly shake it to heat until the chip sinks and the flux overflows. Stop heating after confirming that the solder joint is fused.
