Essentials of tin soldering operation:
1、Surface treatment of soldered parts
Manual soldering iron soldering encountered in the soldering is a variety of electronic parts and wires, unless in large-scale production conditions using the "insurance period" within the electronic components, generally encountered in the soldering often need to carry out surface cleaning work to remove the soldering surface of the rust, oil, dust and other impurities affecting the quality of soldering. Manual operation of commonly used mechanical scraping and grinding and alcohol, acetone scrubbing and other simple and easy methods.
2, pre-soldering
Pre-soldering is to be soldered component leads or conductive soldering parts pre-wetted with solder, generally also known as tin-plated, on the tin, tin-lined, etc.. Called pre-soldering is accurate, because the process is the whole process of the mechanism of tin soldering - solder to wet the surface of the weldment, relying on the diffusion of metal to form a bonding layer after the surface of the weldment and make the weldment "plated" on a layer of solder.
Pre-soldering is not an indispensable operation of tin soldering, but the manual soldering iron welding, especially maintenance, debugging, research and development work can be said to be almost indispensable.
3、Don't use too much flux
The right amount of flux is indispensable, but do not think the more the better. Excessive rosin not only caused by welding around the solder joints need to clean the workload, and extend the heating time (rosin melting, volatilization needs and take away the heat), reducing efficiency; and when the heating time is not enough time and easy to clip to the solder in the formation of "slag" defects.
For the soldering of switching components, excessive flux is likely to flow into the contacts, resulting in poor contact. The appropriate amount of flux should be the rosin can only wet the solder joints to be formed, do not let the rosin through the printed circuit board into the component surface or socket holes (such as IC sockets). For the use of rosin core wire, basically do not need to apply flux.
4, keep the soldering iron head clean
Because the soldering iron head welding in a high temperature state for a long time, and contact with flux and other heat decomposition of substances, its surface is easy to oxidize and form a layer of black impurities, these impurities almost form a heat insulation layer, so that the iron head to lose the role of heating. Therefore, it is necessary to rub the impurities on the soldering iron stand at any time. With a wet cloth or wet sponge at any time to wipe the iron head, is also a common method.
5, heating to rely on the solder bridge
Non-assembly line operation, a welding soldering point shape is a variety of different, we can not constantly change the soldering iron head. To improve the efficiency of the soldering iron tip heating, the need to form a heat transfer solder bridge. The so-called solder bridge is to rely on the soldering iron to retain a small amount of solder as a bridge for heat transfer between the soldering iron tip and the soldered part when heating.
Obviously due to the thermal conductivity of the liquid metal is much higher than the air, so that the solder is quickly heated to the soldering temperature. It should be noted that as a bridge of solder tin to retain the amount of tin is not too much.
6, the amount of solder to be appropriate
Excessive solder not only unnecessarily consume the more expensive tin, but also increase the welding time, the corresponding reduction in the speed of work. More seriously, in the high-density circuit, too much tin can easily cause an imperceptible short circuit. But too little solder can not form a solid bond, reducing the strength of the solder joints, especially when welding wires on the board, the lack of solder often causes the wire off.
7, the solder should be firm
Do not make the solder before the solidification of welding parts to move or vibration, especially the use of tweezers to clamp the welding parts must wait for the solidification of solder and then remove the tweezers. This is because the solder solidification process is the crystallization process, according to the crystallization theory, during the crystallization of external forces (welding pieces moving) will change the crystallization conditions, resulting in coarse crystals, resulting in the so-called "cold welding".
The appearance of the phenomenon is the surface of the luster of the dregs; solder joints within the structure of the loose, easy to have air gaps and cracks, resulting in a reduction in the strength of the solder joints, poor electrical conductivity. Therefore, before the solidification of the solder must keep the weldment stationary, the actual operation can be used in a variety of suitable methods to fix the weldment, or the use of reliable clamping measures.
8, soldering iron withdrawal is concerned
Soldering iron to withdraw in time, and the angle and direction of the withdrawal of the formation of a certain relationship to the soldering point. Withdrawal of the soldering iron when gently rotating a little, can keep the solder joints appropriate solder, which needs to be experienced in the actual operation.
