If you need to join two thermally or electrically conductive parts together, it’s time for soldering. In the private sector, the technique of soft soldering is used. This means that the temperature range is below 450 degrees, usually even below 250 degrees. As a beginner in soldering, you should pay attention to the following.
Safety first
Soldering equipment is not a toy. The soldering tip can become several hundred degrees hot, and even light contact with the skin can cause burns. Objects can quickly ignite accidentally. This is not the only reason why a holder is mandatory for work breaks, as is a fireproof base.
Also good to know: Soldering sometimes produces unhealthy substances that should not be inhaled or otherwise enter the body. For this reason, you should at least ensure adequate ventilation, and soldering fume extraction is even better. Food in the vicinity of the soldering point is taboo. Safety goggles are recommended for fine soldering work.
What you need
- Solder: The specialist speaks of solder. It consists mainly of copper and tin, but also contains other components such as flux. You can recognise the composition by the abbreviation: Sn96.5Ag3.0Cu0.5 stands for 96.5 percent tin, 3 percent silver and 0.5 percent copper. The numerical value therefore indicates the tin content. As these are alloys, the melting point of solder can vary. The diameter also varies. As a rule, thicknesses between 0.5 and 1.5 millimetres are suitable for work on electrical devices. Flux reduces the surface tension of the solder so that the solder can flow and spread better. Also important: The soldering device must reach the required temperature to melt the solder.
- Soldering equipment: You can choose between soldering irons, soldering guns and hammer soldering irons. The typical soldering iron with its metal soldering tip is well suited for working on printed circuits and in electrical engineering. Cordless models with rechargeable batteries offer better handling than corded devices. Soldering stations are more suitable for stationary use at the workplace and often offer more precise adjustment options and often have a higher output.
- Holding device: In addition to a fireproof base, a holding device that fixes the part to be soldered is practical. This prevents it from slipping during soldering and cooling and also protects against burns.
The preparation
A metallically clean surface is the prerequisite for an optimum soldering result. Thoroughly clean all parts that you want to solder. Utensils such as a file, sandpaper and alcohol are helpful here. The soldering tip must also be absolutely clean. Wiping the tip with a special sponge moistened with water or a special dry cleaner made of metal wool before soldering helps here.
Soldering
Bring the soldering device up to temperature. Use the solder to test whether the plunger is hot enough. The solder should melt immediately when you hold it to the soldering tip. Place the parts to be soldered in the desired position. This simplifies the soldering process enormously. Then touch the soldering point with the tip of the soldering iron and heat it up. Add the solder. It melts, melts and joins the two parts. Immediately remove the soldering tip and solder from the solder joint and allow it to cool. Do not move the soldered parts during the cooling phase. Movement can lead to a ‘cold solder joint’.
Cold solder joint problem
Sometimes the contact points do not connect properly. This is usually due to insufficiently heated solder or as described above: Movement during the solidification phase. You can recognise such a ‘cold solder joint’ by the lack of shine. It is best to tackle these areas again with the soldering tool. While a cold solder joint can usually be easily repaired, heat damage often causes an irreparable defect. In this case, the soldering device has been used for too long. Therefore, make sure that you only work on contact points with the soldering tip for a few seconds.
Images: Adobe Stock
Originally published on 10.10.2016, updated on 07.03.2025.
