8 essentials for electric soldering iron soldering operation:
1. Surface treatment of weldments
The weldments encountered in manual soldering iron welding are various electronic parts and wires. Unless the electronic components within the "insurance period" are used under mass production conditions, the weldments encountered in general often require surface cleaning. Work, remove rust, oil, dust and other impurities that affect the welding quality on the welding surface. Mechanical scraping and alcohol, acetone scrubbing and other simple and easy methods are commonly used in manual operation.
2. Pre-welding
Pre-soldering is to pre-wet the component leads or conductive welding parts to be soldered with solder, generally also known as tinning, tinning, tinning, etc. It is accurate to call pre-soldering, because its process and mechanism are the whole process of soldering - the solder wets the surface of the weldment, and the surface of the weldment is "plated" with a layer of solder after the diffusion of the metal forms a bonding layer.
Pre-soldering is not an indispensable operation for soldering, but it is almost indispensable for manual soldering iron welding, especially maintenance, debugging, and research and development.
3. Do not use excessive flux
The right amount of flux is essential, but don't assume that more is better. Excessive rosin not only causes the workload of cleaning around the solder joints after soldering, but also prolongs the heating time (rosin melts, volatilizes and takes away the heat), reducing work efficiency; and when the heating time is insufficient, it is easy to be mixed into the solder to form "Slag inclusion" defect.
For the welding of switching elements, excessive flux is easy to flow to the contacts, resulting in poor contact. The proper amount of flux should be that the rosin perfume can only wet the solder joints to be formed, and do not let the rosin perfume flow through the printed board to the component surface or socket hole (such as IC socket). For wires using rosin cores, there is basically no need to reapply flux.
4. Keep the tip of the soldering iron clean
Because the soldering iron tip is in a high temperature state for a long time during soldering, and it is exposed to heat-decomposed substances such as flux, its surface is easily oxidized to form a layer of black impurities, which almost form a heat insulation layer, making the soldering iron tip lose its heating effect. Therefore, rub the impurities on the soldering iron frame at any time. It is also a common method to wipe the tip of the soldering iron with a damp cloth or damp sponge at any time.
5. Heating depends on solder bridge
In non-assembly line operations, the shapes of solder joints for one soldering are various, and it is impossible for us to constantly change the tip of the soldering iron. To improve the efficiency of soldering iron tip heating, it is necessary to form a solder bridge for heat transfer. The so-called solder bridge means that a small amount of solder is retained on the soldering iron as a bridge for heat transfer between the soldering iron tip and the weldment during heating.
Obviously, because the heat conduction efficiency of molten metal is much higher than that of air, the weldment is quickly heated to the welding temperature. Care should be taken not to retain too much tin as a solder bridge.
6. The amount of solder should be appropriate
Excessive solder not only consumes more expensive tin needlessly, but also increases soldering time and correspondingly reduces the working speed. What's more serious is that in high-density circuits, excessive tin can easily cause imperceptible short circuits. However, too little solder cannot form a firm bond and reduce the strength of the solder joints. Especially when soldering wires on the board, insufficient solder often causes the wires to fall off.
7. Welding parts should be firm
Do not move or vibrate the weldment before the solder solidifies, especially when using tweezers to clamp the weldment, be sure to wait for the solder to solidify before removing the tweezers. This is because the solder solidification process is a crystallization process. According to the crystallization theory, the external force (movement of the weldment) during the crystallization period will change the crystallization conditions, resulting in coarse crystals, resulting in the so-called "cold welding".
The appearance phenomenon is that the surface is dull and bean dregs-like; the internal structure of the solder joint is loose, and it is easy to have air gaps and cracks, resulting in a decrease in the strength of the solder joint and poor electrical conductivity. Therefore, the weldment must be kept still before the solder solidifies. In actual operation, various suitable methods can be used to fix the weldment, or reliable clamping measures can be used.
8. Pay attention to the evacuation of the soldering iron
The evacuation of the soldering iron should be timely, and the angle and direction of evacuation have a certain relationship with the formation of solder joints. Gently rotating the soldering iron when removing it can keep the solder joints properly soldered, which needs to be experienced in actual operation.
