Remove the flat package IC step:
1) First clean the integrated block to be removed with the letter water or gasoline.
2) Before removing the components, you should see the direction of the IC, mark it properly, and do not reverse it when reinstalling. It is important to take photos to prevent the surrounding originals from being blown away for recovery.
3) Observe the presence or absence of thermal devices (such as plastic components) on the side of the IC and on the front and back. If there are items such as shields, cover them.
4) Add appropriate solder paste or rosin to the IC pin to be removed (I don't like it very much), so that the PCB board pad after removing the component is smooth and full of solder, otherwise it will be burr, it is not easy to re-solder Bit. (This step has little effect on soldering with soldering iron, but the effect on welding with hot air gun is big. The effect of air gun is big. The picture below is the picture taken by the integrated block. It is not treated with a soldering iron. The solder is very full, and it is not easy to have false soldering with air gun welding.
5) Evenly preheat the adjusted hot air gun in an area of ​​about 20 square centimeters around the component (the wind nozzle is about 1 cm away from the PCB board, and moves faster in the preheating position, and the temperature on the PCB board does not exceed 130-160 °C. )
6) If the solder joint has been heated to the melting point, the hand holding the tweezers will feel the first time, and the solder on the IC pin must be melted before passing through the “zero forceâ€. Carefully move the component vertically from the board. Pick up, this can avoid damage to the PCB or IC, and can also avoid solder short circuit left on the PCB.
7) For lead-free soldering boards, such as computer motherboards, the I/O manifold is very difficult to obtain. Because the lead-free solder temperature is relatively high,
It is very difficult for a hot air gun to blow it, so the best way is to use a low temperature solder to drag all the pins of the manifold block.
—— The above steps are the key to subsequent welding. If you do well, the welding will be very smooth. Otherwise, the welding will be very troublesome and even the work will be abandoned.
Flat IC step and soldering
1) According to the distance between the solder and the peripheral resistor and capacitor, the amount of solder left by the pad and the block of the integrated block is determined by air gun welding or drag welding.
2) Regardless of the type of soldering, the pads and pins should be leveled (convenient for pin and pad alignment), then wipe the pads with paper or the like to remove residual solder paste and dirt. Drop it.
3) Next, align the integrated block and the pad (alignment is a very critical step for soldering later). Before the chip is placed, apply the solder paste to the pad four feet, and then solder the solder paste with a soldering iron to make it evenly flat. Spread on the soldering foot, because the solder paste is sticky, it can prevent the right and left sliding of the integrated block, fix several feet with tin (prevent the integrated block from being blown), then use the heat gun to heat vertically, wait until the tin is turned When using a thin pointed steel pin, press the integrated block vertically (if tinned, you can feel the sinking action of the integrated block), so that the integrated block pins are attached to the pads.
4) After soldering the solder paste on the lead, perform blow welding or drag welding. When soldering the soldering iron, be sure to pay attention to the small capacitor resistance around the soldering iron.
5) In addition, before the soldering, the soldering iron head must be kept bright and tin-containing, so that the soldering iron tip is more likely to absorb the solder. When dragging down, the solder is carried by the soldering iron head to the rear of the soldering iron tip, which makes it easier to make tin. Separating from the pins, the smoothness of the drag has a lot to do with this.
6) If you want the soldering iron to keep the temperature of the soldering iron, the temperature should not be too high. If it is too high, it will easily oxidize the soldering iron, blackening, and it is not easy to hang tin. Therefore, the temperature control of the soldering iron must be controlled well. This is also very important.
7) Regarding the shape of the tip, the cutter head is not suitable for drag welding, and the horseshoe shape and the one-word type are more suitable for drag welding.
The above is my experience in the welding practice for many years, but also draws on the valuable experience of other forum users, if you can help beginners and learn from it, it will be my greatest wish!
The following is the document I made, there are pictures, there is no gold coins. Remove flat package IC step_welding patch IC.rar
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