Soldering is an important part of working with electronic components. In order for the necessary components to be firmly connected and for a current to flow smoothly, not only must you have the essential equipment but the right techniques are crucial. In our handy how-to guide, we explain everything you need to get the best results.
Preparation before soldering
The first step in any case is to create a clean, dust-free work enviroment. Make sure that the soldering tip and the item you are going to solder are completely clean and that there is no residue on them.
If any excess material is found on the component, gently grind it with abrasive paper and then thoroughly clean it with compressed KONTAKT 33299 AA or alcohol.
Place a small vice in position so that the part to be soldered is held securely and does not slip during heating or cooling.
In order to be able to solder very small parts precisely, a soldering aid with a magnifying glass can help you out a lot.
Reheat your appliance and bring it to an appropriate operating temperature for your solder (see below).
It is best to ensure suitable ventilation for your workplace. The fluid contains acids which, upon heating, can cause harmful vapours and should not be inhaled.
Extraction units with intergrated filters are available in a range of sizes to provide optimum protection against toxins in the air.
Put all the utensils you need within easy reach whilst working.
Using a soldering station instead of a soldering iron
A soldering station is much more comfortable than using a soldering iron. Soldering stations can keep an exact temperature pre-setting, ensuring it doesn’t change during the whole soldering process.
The stations usually have clear displays and offer numerous other helpful functions.
Soldering stations are available with different settings and price points, depending on the application area and your preference.
Weller’s GENERATION WT stations are particularly user-friendly for working with several soldering points without any problems. If you prefer soldering with hot air, we’d recommend the WTHA hot air station from Weller, which can be used to solder even the smallest components.
If you work with sensitive SMD and BGA components, this is best done with an infra-red soldering system. The advantage of this device is that the heat on the tool is generated by concentrating light exactly where it is needed, therefore not overheating the components.
Thanks to the larger workspace, it is even possible to work on motherboards without any issues with soldering stations.
Using the right tool
Helpful soldering tools should be ready and within reach at all times to avoid uneccessary interruptions. Important tools include a stripping tool, a high quality tweezer set, a side cutter, a board assistant with a magnifying glass, a circuit board and a dry sponge for cleaning.
This type of cleaning (also referred to as “dry clean“) puts less strain on the soldering tip as it doesn’t experience a temperature shock. For high-quality soldering stations, such as the WT1010H from Weller, a dry sponge is already integrated.
Once you’re up and running with soldering
The cable ends which are to be connected, should first be stripped and twisted into one another. The work to be carried out depends on whether the cables are thin cables of up to 1.5 square meters or thicker cables.
For thin cables, it is sufficient to apply a little solder to the soldering tip and hold it to the soldering point. The strands will be sucked in together by capillary forces.
In the case of thicker cables, the larger amount of copper leads to cooling of the soldered joint – do not hold the soldering tip any longer. Since copper is very conductive, the insulation could melt – use a larger amount of solder to avoid this.
Although most varieties of solder already contain flux, a thicker solder joint may be helpful. However, you should pay attention to the ventilation of your workplace; the flux which bonds the materials together generates toxic fumes.
Solder wires are available in various alloys, depending on the application area. Although lead-bearing solder is still available, from environmental and health points of view, the heavy metal should be avoided.
In the industrial electronics industry, lead-alloy soldering has been completely banned since 2006/2007.
Lead has a lower melting temperature and better flux properties than other metals, and therefore can sometimes be suitable for hobbyists.
Soldering through plug-in power
Since connectors require a stable connection to the circuit board, wired versions are usually used due to their stability.
Due to the through-hole technology (THT), they are so rigidly connected to the component that both plugging and pulling forces have no influence on them.
For this purpose, the wired components are inserted through the existing contact holes of the circuit board and then soldered. To make sure you are not using any damaged parts, make sure you test them with an LCR component tester beforehand.
Soldering of SMD components
Clean the circuit board first with a suitable cleaning agent, then wet both pads with flux. For such small parts, a flux pen is particularly helpful.
Align the two parts correctly and fix them with two diagonally set soldering points.
If the parts are not perfectly aligned, re-adjust them after heating the two soldering points, now the pins are soldered.
In order to be able to remove the excess tin from a soldering wire, pull the soldering tip to one side. Be careful not to overheat the part during the entire process, and try not to apply too much pressure to it.
In this case, superfluous solder, so-called solder bridges, is most easily removed by means of a de-soldering strand. You can find out how to do this under the heading ‘De-soldering’.
The optimal temperature
There is a difference between soft and hard soldering.
Soft solder melts at less than 450 degrees Celsius, whereas the liquid temperature of Hartoten is between 450 and 900 degrees Celsius.
Since electronic components are very sensitive, only soft soldering can be used here.
The temperature your work depends on the components you are using. Check the melting temperature of your soldering tin, as well as the working temperature of your flux. It should in any case be above the two minimum values, but it must not exceed the maximum operating temperature of the flux, as this will then evaporate.
The soldering temperature for electronic components is 300 to 320 degrees Celsius. When fine wires are used, a temperature of less than 300 degrees and a thin soldering tip is used.
If the temperature is too low, the solder will not be shiny and will be drop-shaped. In this case, you should adjust the temperature, and then continue to work.
Beware of electrostatic discharge (ESD)
Many electronic components are very sensitive and they can be damaged by voltage surges, even at low currents or voltages. This can lead to a failure of the entire device later on.
In order to prevent such currents, make sure you have the right set for your needs. For example: an ESD working mat, ESD gloves, ESD brushes and a wrist strap with an ESD lead-out cable.
If you are using a soldering station, you should regularly check the leakage voltage and the grounding resistance of the soldering tip to the power plug of the device.
De-soldering
If you have used too much tin or parts are wrongly soldered, a de-soldering process is necessary. Depending on the equipment and skill level, either a brazing wire or a de-soldering station can be used.
If a wire is chosen, place it on the spot to be soldered and heat with the soldering tip until the superfluous tin is sucked in as described above by capillary forces. Soldering / desoldering stations make this much easier, which also include a desoldering iron. Excess material is sucked off directly afterwards. When vacuuming, be sure to work at a steep angle so that no tin residues are distributed.
Checking over your solder work
To ensure that all components have been soldered correctly, the soldering work should be checked before commissioning.
First of all, examine the component. Are there any defective soldered joints, bent IC legs or even incorrectly used components?
If all looks good here, a test should then be carried out with a multimeter.
This allows you to measure the throughput, voltage, current consumption and resistance of each individual connection, thus identifying short circuits and disruptions.
All accessories are supplied with Atlas models. Through the oscilloscope function and Bluetooth capability, the data from the Atlas Multimeter can be transferred to a smartphone or tablet.
Only when you‘ve made sure there is no fault in your soldering work should the component be installed and subjected to a functional test.
Cover image: Fotolia, 124209586, silver-john
