1. Surface treatment of weldment
The weldments encountered in manual soldering are various electronic parts and wires. Unless the electronic components within the "insurance period" are used under large-scale 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. In manual operation, simple and easy methods such as mechanical scraping and alcohol and acetone scrubbing are commonly used.
2. Pre-soldering
Pre-soldering is to wet the component leads or conductive welding parts to be soldered with solder in advance, 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 soldered part, and after the bonding layer is formed by the diffusion of the metal, the surface of the soldered part is "plated" with a layer of solder.
Pre-soldering is not an indispensable operation for soldering, but it is almost indispensable for manual soldering, especially maintenance, debugging, and development.
3. Do not use excessive flux
The right amount of flux is essential, but don't think more is better. Excessive rosin not only causes the workload of cleaning around the solder joints after welding, but also prolongs the heating time (the rosin melts, volatilizes and takes away heat), reducing the 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 switch components, excess flux easily flows to the contacts, resulting in poor contact.
The appropriate amount of solder should be that the rosin water can only wet the solder joints to be formed, and do not let the rosin water flow through the printed board to the component surface or socket holes (such as IC sockets). For wires with rosin cores, no additional flux is required.
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 comes into contact with substances decomposed by heat such as flux, its surface is easily oxidized to form a layer of black impurities. These impurities almost form a thermal insulation layer, which makes the soldering iron tip lose its heating effect. Therefore, it is necessary to rub the impurities on the soldering iron stand at any time. Wiping the tip of the soldering iron at any time with a damp cloth or sponge is also a common method.
5. The amount of solder should be appropriate
Excessive solder not only consumes the more expensive tin unnecessarily, but also increases the soldering time and reduces the working speed accordingly. What's more serious is that in high-density circuits, excess 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.
6. The weldment 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 solidification process of solder is a crystallization process. According to the crystallization theory, external force (movement of the weldment) during crystallization 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, it is necessary to keep the weldment stationary before the solder solidifies. In actual operation, various suitable methods can be used to fix the weldment, or reliable clamping measures can be used.
7. The evacuation of the soldering iron is exquisite
Soldering iron should be handled in time, and the angle and direction of evacuation have a certain relationship with the formation of solder joints.
Gently rotate the soldering iron when removing it to keep the solder joints properly soldered, which needs to be experienced in practice.
