The chip components on PCB are new micro-miniature components with no leads or short leads. It is directly mounted on PCB and is a special device for SMT. Chip components has the advantages of small size, light weight, high installation density, high reliability, strong vibration resistance, good high-frequency characteristics, and strong anti-interference ability. At present, it has been widely used in computer equipment, mobile communication equipment, video camera, color TV tuner, VCD and other products, with rapid development.
Commonly used chip components are:
(1) chip resistors
(2) chip capacitors
(3) chip inductors
(4) chip diodes
(5) chip transistors
(6) chip small integrated circuits.
These chip components are very small in size and are fragile to heat and conflict. Some IC lead pins are many and difficult to disassemble, which brings great difficulties to maintenance. Therefore, scientific disassembly methods are very important.
Common disassembly methods are as follows:
1. Dedicated soldering iron tip disassembly method
Purchase a dedicated "∏-shaped" soldering iron tip. The width and length of the notch of the "∏-shaped" head can be determined according to the size of the part to be disassembled. The special soldering iron tip can melt the solder of the lead pins on both sides of the disassembled part at the same time, so the disassembled components can be easily removed. It can also use a self-made soldering iron tip to disassemble.
Self-made method:
Choose a section of red copper tube whose inner diameter matches the outer diameter of the soldering iron tip, clamp one end flat with a vise or hammer flat, and drill small holes. Then use two red copper boards or red copper tubes to be longitudinally dissected, and flattened for machining into the same size as the length of the disassembled part, and drill small holes. Flatten the end face, polish it clean, and finally assemble it into the shape, cover it on the tip of the soldering iron, heat it and dip it in tin, and then set it aside.
For rectangular chip components with two solder joints, as long as the soldering iron tip is tapped into a flat shape so that the width of the end face is equal to the length of the component, the two solder joints can be heated and melted at the same time to remove the chip component.
2. Tin-absorbing copper mesh method
The tin-absorbing copper mesh is a mesh belt woven with fine copper wires. The fine copper wires can also be replaced by metal shielded wires or multi-strand flexible wires. When in use, cover the wires on the multiple pins, apply rosin alcohol flux, heat it with a soldering iron, and pull the wires, the solder on each pin will be absorbed by the wires. Cut off the wires that have been soldered, repeat it several times, and the solder on the pins will gradually decrease until the pins are separated from PCB.
3. Tin-melting cleaning method
When the multi-pin components are melted by heating the solder with an anti-static soldering iron, clean the solder with a toothbrush, oil painting brush, paint brush, etc., and the components can also be quickly disassembled. After the components are disassembled, the printed board should be cleaned in time to prevent residual tin from causing short circuits in other parts.
4. Lead pull and disassembly method
This method applies to the disassembly of chip-mounted integrated circuits. Use an enameled wire of appropriate thickness and certain strength to pass through the gap inside the pin of the integrated circuit, fix one end of the enameled wire at a certain position, and hold the other end by hand. When the solder melts, pull the enameled wire to "cut" the solder joints, and the integrated circuit pins are separated from PCB.
5. Solder suction device disassembly method
There are two types of solder suckers:
ordinary solder suckers and
electric soldering irons.
When the ordinary solder sucker is in use, press down the piston rod of the solder sucker. When the soldering joint of the disassembled part is melted by the electric soldering iron, put the suction nozzle of the solder sucker close to the melting point, press the release button of the solder sucker, and suck away the molten tin at the time of the piston rod of the device bounces back. Repeat the operation several times, and the disassembled parts will be made to separate from PCB.
Tin-absorbing soldering iron is a special suction tool that assembles an ordinary solder sucker and an electric soldering iron, and its usage is the same as that of an ordinary solder sucker.
It should be noted that, it requires preventing static electricity in the process of local heating, and the power of the soldering iron and the size of the soldering iron tip should be appropriate.
