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Manual patch proofing welding steps and precautions
- 2020-07-14-

Manual patch proofing welding steps and precautions

inManual patch proofingBefore soldering, be sure to test the PCB to clean the dirt and oxides on the board, otherwise it will be difficult to solder. After cleaning the PCB board, you can start soldering. Pay attention to the soldering sequence when soldering. The general order is to follow the height and volume of the electronic components, from short to high and from small to large. SMD proofing welding usually first solder the chip resistors and capacitors, then solder the chip diodes and transistors, and then solder the chips.

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1. Soldering of chip resistors and capacitors

First, tin on one of the pads to play a fixed role. Then hold the patch with tweezers in the left hand, and heat the solder with the soldering iron in the right hand. While the solder is melting, place the component to complete the soldering of one pin, and then solder the other pin after the patch is fixed. This manual SMD proofing welding method is suitable for the tip of the sharp cone type soldering iron, and the speed is slightly slower due to the two welding. To increase the soldering speed, you can solder both pins at the same time. First tin the two pads, then hold the components with the tweezers in your left hand, and heat the pads with the soldering iron in your right hand. Place the components while the solder is melting. The components must be placed upright. To prevent the component from moving, you can use tweezers to press on the upper part, and after full contact and infiltration, first remove the soldering iron, and then remove the tweezers. This manual patch proofing soldering method is suitable for using a knife-shaped soldering iron tip, because of its large volume, it can heat two pads at the same time to make it evenly heated, which not only improves the welding speed, but also ensures the welding quality.

2. Welding of SMD diodes and triodes

The soldering method of the SMD diode is the same as the soldering method of the SMD resistor. The difference is that it needs to pay attention to the polarity when performing manual SMD proof welding. Generally speaking, there is a green dot on the SMD LED or one side of the bevel is missing. When soldering the negative electrode and the SMD transistor, first apply the tin and place the components. Because the pad is relatively large, and the pin of the SMD transistor is relatively small, so when doing manual SMD proofing, the pins must be placed on the pad. Otherwise, there will be poor contact of individual pins, which will affect the normal operation of the circuit.

Three, the welding of the chip

1. Chip soldering with a slightly larger lead pitch: When doing manual placement and proofing, you must first tin the pad on the side of the chip pad, and then use tweezers to align the chip to the pad. At this time, there are The pin of the tin is pushed up a little bit, find the position, align the chip, and then use a soldering iron to open the solder on the pad, press the chip's finger to apply a little force, so that the chip can be closely attached PCB, even if this pin is soldered. Be careful not to use too much force when pressing down, especially before the solder is completely melted away, otherwise the pins will bend. Next, use the same manual SMD proofing method to solder the pin at the other end of the diagonal of the chip, then fix the chip, and solder the remaining pins one by one.

2. Welding of pin-intensive chips: soldering of pin-intensive chips is suitable for drag welding. First, clamp the chip with tweezers and align the pads, then press the chip with your thumb to confirm that the chip is aligned with the pads, then use tweezers to take a small piece of rosin and place it next to the chip pins, and then use a soldering iron to When the rosin is melted, the rosin should be melted as much as possible and evened. Evenly distribute the rosin on a row of pads. Use the same method to fix the pins on the other side of the chip. After this step, the chip is firmly fixed on the PCB. Next, cut a small cut of solder and place it on the pad on one side. Then use a soldering iron to melt the solder, and then drag the soldering iron back along the contact point of the pin and the pad until the end of the pin, so that the pins on one side of the chip are all soldered. The pins on the other sides are made in the same way. At this point, the soldering of the manual patch proofing components is complete.

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