SMD component manual hot air soldering station welding steps
SMD component manual hot air soldering station welding steps
1. Preparation
1. Turn on the hot air gun, adjust the air volume and temperature to the appropriate position: feel the air volume and temperature of the air duct with your hands; observe whether the air volume and temperature of the air duct are unstable.
2. Observe that the inside of the air duct is reddish. Prevent overheating inside the blower.
3. Observe the heat distribution with paper. Find the temperature center.
4. Use the lowest temperature to blow a resistor, and remember the position of the lowest temperature knob that can best blow down the resistor.
5. Adjust the air volume knob so that the steel ball indicating the air volume is in the middle position.
6. Adjust the temperature control so that the temperature indication is around 380°C.
Note: When the heat gun is not used for a short period of time, make it sleep Turn off the heat gun when not working for 5 minutes.
2. Use a hot air gun to desolder the flat package IC:
1): Disassemble the flat package IC steps:
1. Before removing the components, check the direction of the IC, and do not put it backwards when reinstalling.
2. Observe whether there are heat-resistant devices (such as liquid crystals, plastic components, BGA ICs with sealant, etc.) next to the IC and on the front and back. If there are, cover them with shielding covers and the like.
3. Add appropriate rosin to the IC pins to be removed to make the PCB pads smooth after the components are removed, otherwise there will be burrs and it will not be easy to align when re-welding.
4. Preheat the adjusted hot air gun evenly in an area about 20 square centimeters away from the component (the air nozzle is about 1CM away from the PCB board, move at a relatively fast speed at the preheating position, and the temperature on the PCB board does not exceed 130-160°C )
1) Remove the moisture on the PCB to avoid "bubbling" during rework.
2) Avoid stress warping and deformation between PCB pads caused by the excessive temperature difference between the upper and lower sides of the PCB board due to rapid heating on one side (upper side).
3) Reduce the thermal shock of parts in the welding area due to heating above the PCB board.
4) Avoid the adjacent IC from desoldering and lifting due to uneven heating
5) Circuit board and component heating: The heat gun nozzle is about 1CM away from the IC, moving slowly and evenly along the edge of the IC, and gently clamping the diagonal part of the IC with tweezers.
6) If the solder joint has been heated to the melting point, the hand holding the tweezers will feel it at the first time, must wait until all the solder on the IC pin is melted, and then carefully lift the component vertically from the board through "zero force" Lift it up, so as to avoid damage to the PCB or IC, and also avoid short circuiting of the solder left on the PCB. Heating control is a key factor in rework, and the solder must be completely melted to avoid damage to the pad when the component is removed. At the same time, it is necessary to prevent the board from being overheated, and the board should not be distorted due to heating.
(For example: if possible, you can choose 140°C-160°C for preheating and heating at the lower part. The whole process of removing the IC does not exceed 250 seconds)
7) After removing the IC, observe whether the solder joints on the PCB are short-circuited. If there is a short-circuit, use a hot air gun to heat it again. separate. Try not to use a soldering iron, because the soldering iron will take away the solder on the PCB, and the less solder on the PCB will increase the possibility of false soldering. It is not easy to fill tin pads with small pins.
2) Install flat IC steps
1. Observe whether the pins of the IC to be installed are flat. If there is a solder short circuit on the IC pins, use a tin-absorbing wire to deal with it; If the pin is not correct, the crooked part can be corrected with a scalpel.
2. Put an appropriate amount of flux on the solder pad. If it is heated too much, the IC will float away. If it is too little, it will not work. And cover and protect the surrounding heat-resistant components.
3. Put the flat IC on the pad in the original direction, and align the IC pins with the PCB board pins. When aligning, the eyes should look vertically downward, and the four sides of the pins must be aligned. Visually feel the four sides of the pins The length is the same, the pins are straight and there is no skew. The sticking phenomenon of rosin when heated can be used to stick IC.
4. Use a hot air gun to preheat and heat the IC. Note that the hot air gun cannot stop moving during the whole process (if it stops moving, it will cause excessive local temperature rise and damage). Observe the IC while heating. If there is any movement, gently adjust it with tweezers without stopping the heating. If there is no displacement phenomenon, as long as the solder under the IC pins is melted, it should be found at the first time (if the solder is melted, you will find that the IC has a slight sinking, the rosin has light smoke, the solder is shiny, etc., you can also use tweezers to gently Lightly touch the small components next to the IC, if the small components next to it move, it means that the solder under the IC pins is also about to melt.) and stop heating immediately. Because the temperature set by the heat gun is relatively high, the temperature on the IC and PCB board continues to increase. If the temperature rise is not detected early, the IC or PCB board will be damaged if the temperature rise is too high. So the heating time must not be too long.
5. After the PCB board is cooled, clean and dry the solder joints with thinner water (or board washing water). Check for solder joints and short circuits.
6. If there is a false soldering situation, you can use a soldering iron to solder one by one or remove the IC with a heat gun and re-solder; if there is a short circuit, you can use a damp heat-resistant sponge to wipe the tip of the soldering iron, and dip it in Put some rosin along the pins at the short circuit and gently draw it to take away the solder at the short circuit. Or use tin-absorbing wires: use tweezers to pick out four tin-absorbing wires dipped in a small amount of rosin, place them on the short circuit, and gently press them with a soldering iron on the tin-absorbing wires, the solder at the short-circuit will melt and stick to the tin-absorbing wires. Clear the short circuit.
Another: You can also use an electric soldering iron to solder the IC. After aligning the IC and the pad, dip the soldering iron in rosin and gently stroke along the edges of the IC pins one by one. If the IC pin spacing is large, you can also add Rosin, use a soldering iron to roll a tin ball over all the pins for soldering.
