Method for desoldering a chip integrated circuit

De-soldering chip-type integrated circuits under amateur conditions is a difficult task. The author summarized a set of methods for desoldering and chip-mounting integrated circuits in the maintenance practice, and introduced them to everyone for reference.

Disassembled chip integrated circuit

It is too cumbersome, time-consuming and laborious to remove the chip integrated circuit by picking the pins. It is possible to damage the pad with a slight carelessness, which causes difficulties in soldering the integrated circuit. When I removed the chip integrated circuit, I used a plastic welding torch to melt the solder by using the high temperature hot air blown out. I use the 700-watt electronic thermostat in Wenzhou, Zhejiang, which is sold in the electronics market. The market price is about 80 yuan. When disassembling the integrated circuit, first remove the board from the machine, apply the loose ion to the integrated circuit pin, then energize the torch, the temperature is turned to the maximum, and the right hand takes the torch to the pin of the integrated circuit to move quickly, so that the pins are alternately rotated. Heat, hold the pointed tweezers in the left hand and clamp a pin of the integrated circuit. When the solder is completely melted, the left hand quickly lifts the integrated circuit and disposes it in the alcohol prepared in advance, so that it can be reused after misjudgment.

Cleaning the pad

After the integrated circuit is removed, there is still a lot of residual tin on the pad, which will cause difficulties in re-welding the integrated circuit and must be cleaned up. Use a suction rope to pry the rosin and suck off the residual tin. Be sure to pay attention to the suction, the direction of movement of the suction tin rope should follow the direction of the pad, do not traverse, otherwise it will easily damage the pad. After the residual tin is cleaned, the residual rosin is cleaned with absorbent cotton and alcohol.

welding

SMD integrated circuits are characterized by thin pins and thin pads. The selection of suitable soldering irons and solder wires is the key to successful soldering. The author used the 35-watt internal heat-type long-life soldering iron produced by Guangzhou Huanghua Electronic Appliance Factory. The tip of the soldering iron is thin and not oxidized. After heating, the rosin is smashed and the soldering iron tip is very bright, which is suitable for the soldering of the chip components. The electronics market is available for sale, about twenty yuan. The solder wire I used was an unknown rosin-containing solder wire with a thickness of 6 mm and a tin content of 65% (Japanese, I don't understand). This solder wire has a suitable thickness and a moderate tin content. The solder wire is too thick to be soldered, and the tin content is too low to affect the soldering effect.

When soldering, first apply the loose ion to the pins of the integrated circuit, and then accurately position the integrated circuit pins and the pads on the board. Solder the four corners and check again to verify that each pin of the integrated circuit is correctly aligned with its own pad location. Then the motherboard is erected (need someone to help), the left hand takes the solder wire, the right hand takes the soldering iron, the soldering iron and the motherboard are at a 35 degree angle, from the top of the right side of the integrated circuit, the soldering iron moves down with the solder wire, using the flow Hot tin solders the leads to the pads. During the period from the last pin to the last pin, if two pins or pins are soldered together, repeat the above action and use the surface tension of the rosin to separate the adjacent legs. After soldering one side, remove the residual tin and rub the rosin to clean the tip to keep it clean. Turn the main board and repeat the above actions to solder all the pins. If individual pins are also soldered together, they can be sucked up with a suction cord and repaired separately. Clean the residual rosin on each pin of the integrated circuit with alcohol, dry or naturally air dry, and the entire desoldering work speed.

Precautions:

When the soldering iron is welded down, the force must be light, mainly by using gravity to make the hot solder flow to weld. It is too hard to bend the pins too much, causing trouble.

In addition, the solder flowing during soldering tends to fall on the board. After soldering, it is necessary to carefully check and clean the residual tin to prevent loss after power-on.

When practicing this welding method, it is recommended that you practice with the motherboard of the VCD machine (such as the Samsung 802 motherboard). The integrated circuit on the board has no discrete components around the back of the motherboard, and will not affect the movement of the soldering iron during the soldering process. The chip-type integrated circuit on the decoder board is on the same side as the discrete components, which will affect the movement of the soldering iron and cause inconvenience to the soldering. When soldering such a board, the discrete components that are in the way can be removed first, and the discrete components are restored after the integrated circuit is desoldered.

This method is generally only required to practice 3 to 5 times to master. After proficiency, the soldered integrated circuit is no different from the original soldering. This method is simple and easy to learn, saving time and effort, and high efficiency. Would you like to try it?