With the development of science and technology, basically most of the circuit board will use the chip this thing, chip resistor, because it is very small, light weight, the most important thing is the anti-interference, anti-vibration ability is very good, so it is generally used in high-end computers or medical equipment, etc., in fact, for those who do not understand the SMD, it is still quite afraid of it, because it will be welded up to it is a very difficult thing to do, without a certain experience skills can not be done. Certain experience skills can not be done, the next I will share with you the welding method of chip resistors, even if you are circuit whites, after reading you do not have to worry about welding it.
The advantages of SMD:
1, small size, do not need to go through the hole, thus reducing the stray electric field and stray magnetic field, which is very important for high-frequency analog circuits and digital circuits to tell the circuit;
2, lightweight; easy to save and mail
3, adapted to the re-flow soldering and wave soldering;
4, stable electrical performance, high reliability;
5, low assembly cost, and match with automatic mounting and labeling equipment;
6, high mechanical strength, high-frequency characteristics are superior.
7. Chip components are easier to weld and disassemble than inline components
Methods for Welding Chip Resistors
1. Note that the coated parts only a thin layer of rosin can be, not too much, otherwise it will leave flux residue, affecting the cleanliness, refused to pass. When the flux residue is too much can be used cotton swabs dipped in alcohol to wipe clean and reapply.
2, first preheat and then tin. The soldering iron and the welding surface should generally be tilted 45 degrees. Contact pressure: the soldering iron head and the soldered parts contact should be slightly pressure, heat conduction is proportional to the size of the pressure applied, but to the surface of the soldered parts do not cause damage to the principle.
Note: In the heating pad and solder wire supply between the time control within 1S, heating time should not be too long, so as not to cause the pad warping, damage to the pad.
3, add solder. In principle, the soldered part is warmed up to the melting temperature of the solder is immediately sent to the solder wire. Note: In the solder wire supply and heating between the time between the solder wire control within 1S, heating time should not be too long, in order to avoid damage to the pad. The action should be fast and consistent. If the heating time is too long, the surface of the solder joint is easy to aging or the formation of slag, the solder is easy to pull the tip of the solder, the solder joint has no luster. If the heating time is too short, the impact of the solder is not wetted, the surface is not smooth, bubbles, pinholes or cause cold welding.
4, de-soldering. When the solder and the pad fully in contact, draw off the solder wire, the action should be fast and consistent.
5, go to the soldering iron. Actions should be fast and consistent, to a soldering point 1S is appropriate, too long soldering surface is easy to aging or the formation of slag, solder is easy to pull the tip of the solder, soldering point has no luster.
Note: the amount of tin on the pad, not easy too much, in the case of patch welding is not skilled, can be regarded as a fixed point of its soldering. Therefore, the amount of tin on the solder joints is not easy to too much, the welding time is not easy to be too long. Should also avoid bridging and adjacent pads.
6. Apply flat mouth non-slip tweezers or anti-static tweezers to clip the chip resistors. To achieve this, use tweezers to hold the middle part of the component to be welded to one side of the pad, adjust the welding position, and adjust the welding direction of the chip resistor to follow the direction of the nominal value reading and silkscreen marking direction. Use tweezers to clamp the component with appropriate force,? Can not be too hard to prevent component damage or splash. Prepare for the next step in the process.
7. Melt the solder joints. When the solder joint is melted, the next step of the process at the same time. Heating the solder joints melting time is not too long, otherwise it will cause the solder joints aging or the formation of slag, solder is easy to pull the tip of the solder, the solder joints have no luster. If the heating time is too short, the impact of solder is not wetting, the surface is not smooth, bubbles, pinholes or cause cold welding.
8, quickly put the components tightly against the edge of the pad and inserted to weld it. Components into the pad must be close to the surface of the motherboard into the pad, and make the components in the middle of the entire installation position.
9, when the component and the pads between the solder completely fully wet, pull out the soldering iron. If the end of the soldering found that the solder joints aging or burrs, too much tin, too little can not be modified, such as the other side of the soldering is completed and then modified together.
10, welding components on the other side of the solder joints, operating procedures and attention to reference with 2-5 points
11, reference to IPC standards to check the solder joints. If the welding is completed and found to be tilted or high and low phenomenon, note that you can not use tweezers on the surface of the component, the resistor will be pressed down, and then use the soldering iron to melt the solder joints to the top of the component down; such an operation, it is easy to make the component is subject to uneven external forces under the fracture. The correct operation is to melt the soldering point and then use tweezers to hold the middle of the component to adjust.
12, refer to the IPC standards to check the solder joints, if any defects need to be repaired or replaced. Remove components method: add tin to the two ends of the solder joints, so that the two ends of the solder joints solder in a molten state, while the next step in the process. Note: The amount of tin should not be too much to prevent it from flowing into other pads.
Keep the molten state
13, in the molten state of the solder, use tweezers to pick up the components and remove the components to be replaced.
14. Remove the solder with a suction tape. Place the soldering tape on the solder joint, and then the soldering iron heats up the tape so that the solder melts and flows automatically to the tape to remove the solder.
15. Use the solder suction tape to clean up the solder. Note: Only need to remove the solder can be clean, heating time is not too long, too long will also damage the PCB or pads.
16, remove the solder, clean the pads, and then re-open the welding operation
The above is about the chip resistor welding method and step by step introduction, in fact, welding is not so difficult, as long as a step by step, and then more careful in the welding process, and patience, and can not be halfway, in addition to pay special attention to safety. In fact, SMD components are better than plug-in components, I believe that the use of children's shoes will not be used back to plug-in components. I hope the above content on the new contact chip resistor you help!