Operating instructions for soldering with an electric soldering iron:
1. Surface treatment of welded components
The soldering components encountered in manual soldering with a soldering iron are various electronic parts and wires. Unless electronic components within the "warranty period" are used under large-scale production conditions, surface cleaning work is usually required to remove impurities such as rust, oil stains, dust, etc. that affect the welding quality on the soldering surface. Simple and easy methods such as mechanical scraping, alcohol and acetone scrubbing are commonly used in manual operations.
2. Pre welding
Pre soldering refers to pre wetting the leads or conductive soldering areas of the components to be soldered with solder, commonly known as tin plating, tinning, or tinning. Pre soldering is accurate because its process and mechanism involve the entire soldering process - the solder wets the surface of the workpiece, forms a bonding layer through metal diffusion, and then "coats" the surface of the workpiece with a layer of solder.
Pre soldering is not an indispensable operation for soldering, but it is almost essential for manual soldering with a soldering iron, especially for maintenance, debugging, and development work.
3. Do not use excessive soldering flux
An appropriate amount of soldering flux is essential, but don't think that more is better. Excessive rosin not only requires cleaning around the solder joint after welding, but also prolongs the heating time (rosin melts, evaporates and takes away heat), reducing work efficiency; And when the heating time is insufficient, it is easy to get mixed into the solder and form "slag inclusion" defects.
Excessive soldering flux can easily flow to the contacts during the soldering of switch components, resulting in poor contact. The proper amount of soldering flux should be that the loose perfume can only wet the solder joint to be formed, and the loose perfume should not flow into the component surface or socket hole (such as IC socket) through the printed board. For welding wire with rosin core, there is basically no need to apply flux again.
4. Keep the soldering iron tip clean
Because the soldering iron tip is in a high temperature state for a long time during welding and comes into contact with substances such as solder that undergo thermal decomposition, its surface is easily oxidized to form a layer of black impurities, which almost form a thermal insulation layer, causing the soldering iron tip to lose its heating effect. Therefore, it is necessary to constantly rub off impurities on the soldering iron holder. Using a damp cloth or sponge to wipe the soldering iron tip at any time is also a common method.
5. Heating relies on solder bridges
In non assembly line operations, there are various shapes of solder joints that can be welded at once, and we cannot constantly change the soldering iron tip. To improve the heating efficiency of the soldering iron tip, it is necessary to form a solder bridge for heat transfer. The so-called solder bridge is a bridge that uses a small amount of solder left on the soldering iron as a heat transfer bridge between the soldering iron tip and the solder piece during heating.
Obviously, due to the much higher thermal conductivity of the molten metal compared to air, the welded component is quickly heated to the welding temperature. It should be noted that the amount of tin retained as a solder bridge should not be too much.
6. The soldering amount should be appropriate
Excessive soldering not only unnecessarily consumes expensive tin, but also increases soldering time and correspondingly reduces work speed. More seriously, in high-density circuits, excessive tin can easily cause imperceptible short circuits. However, insufficient soldering cannot form a strong bond, reducing the strength of the solder joints, especially when soldering wires on the board. Insufficient soldering often leads to wire detachment.
7. The welded parts should be firm
Do not move or vibrate the solder before it solidifies, especially when using tweezers to clamp the solder, 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 forces (solder movement) during the crystallization process will change the crystallization conditions, causing the crystals to become coarse and resulting in the so-called "cold welding".
