Tips for soldering electronics

Everyone who does something with electronics at some point has to get started with the soldering iron. Based on examples on the internet, you can safely say that the soldering skills of the average tinkerer are not so good. It would be a shame if your soldered project didn't work properly because of minor soldering flaws. That can be better! We give 13 tips for soldering your own tech.

Thanks to the popularity of boards such as the Raspberry Pi and the Arduino, tinkering with electronics remains a popular activity for many. The components cost next to nothing, and diagrams and even complete project descriptions are eagerly exchanged on the internet. If you get stuck with something, there are countless forums with helpful types who are eager to share their knowledge and skills with you. In short, it's a great time for electronics hobbyists.

01 Invent or reuse it yourself?

At the start of such a project, you are immediately faced with the choice of whether you should devise the circuit yourself or whether someone has already invented it. In the vast majority of cases you can reuse someone else's work with some adjustments.

For the necessary adjustments and for projects that you have to build from scratch, the breadboard is an indispensable tool. Plug the components in, connect them with jumper wires and you'll have a first version of the circuit in a few minutes.

Because the code in many cases makes components superfluous – think of combinations of capacitors and resistors for oscillators and timers – circuits are becoming simpler and errors are more in the code than in the hardware. Once the stuff is on the breadboard, most of the time is spent debugging the code. And once the software works, the basics of the electronic part of the project are complete.

That's when the real work can begin: building in the circuit, so that your project can actually be used. Moving the components from the breadboard to a printed circuit board is the next step.

02 Experiment PCB

For most measurement and control circuits, an experimental printed circuit board (also known as a protoboard or stripboard) will suffice. Much cheaper and it saves designing a printed circuit board layout yourself, too difficult a step for the hobbyist. When choosing the most suitable plate, the dimensions are not even the most important: printed circuit board material is easy to cut to size with a hacksaw. Much more important is the way in which the copper paths are distributed on the printed circuit board. These vary from only single islands to continuous courses over the full length. A matter of taste, but we think pictures with groups of connected islands are ideal, for sale at, among others. Costs: depending on the size, less than one euro to about ten euros.

03 Fitting

For placing the components, a corruption of the German bestücken (provided with) is used: mounting. Unlike industrial series production, hobbyists usually involve components whose legs or pins pass through the printed circuit board to solder them to the underside. The industry has already switched to SMD (surface-mounted device) components in the 1990s, which are much smaller and are installed fully automatically (see box 'Surface-mounted devices').

With experimental printed circuit boards you have to think carefully about the location of the components when mounting. It is logically better to place parts with many connections close to each other.

The installation itself is a painstaking job. It is most efficient to apply all components first and only then to solder. That may seem difficult, because to solder you have to hold the circuit board upside down and without measures the components will fall off the circuit board. To prevent this, bend at least two protruding legs of each component that you apply, in the opposite direction. This way, that component will stick if you turn the circuit board over. Cut the ends of all (including the unbent) legs with small side cutters to a length of about two millimeters. Then place the next component and so on.

When placing each component, make sure that all legs or pins are on their own island, otherwise you will connect them with each other. Integrated circuits and controllers can therefore often only be installed in one way: across the width of the printed circuit board.

Surface mounted devices

A separate category of parts are the smd components. These surface-mounted devices have only tin-plated ends or very small legs and are soldered to the side they sit on the printed circuit board. This is therefore different from the traditional components whose legs go through the printed circuit board and which are soldered to the bottom.

Soldering SMD parts by hand is for advanced users, SMD components are not intended for that; one of the advantages is that they can be applied and soldered completely automatically by robots.

04 Which soldering iron?

The most important tool is of course the soldering iron. The price ranges from a tenner to hundreds of euros, with the latter group being absolutely too expensive to use for hobby projects. These are soldering stations that can be set accurately to the degree and that is greatly exaggerated for this manual work. It is easy to work with a soldering station of a few tens. At Conrad there are already nice models for around 25 euros. Such a station consists of a power supply, the temperature control and a holder for the soldering iron. A separate soldering iron is not recommended, unless you think it is a good idea to have a piece of metal of about 400 degrees loose on your desk. Always place it in a holder, which also offers space for a damp sponge, on which you can wipe the soldering tip.

05 Quality soldering tip

The soldering tip is the part with which you actually solder and that also determines the quality of the soldering iron. The composition and the associated hardness of the material determine the heat transfer of the post. And how long it will last, because corrosion is always lurking in a hostile environment of molten tin and widely fluctuating temperatures. The shape is also important: the coarse point of a typical hardware store bolt is of little use for fine electronics. For electronics there is a wide selection, ranging from chisel or screwdriver model to a cone-shaped point in various lengths. The choice of a marker depends on the specific application, a steady hand and personal preference.

Use a soldering iron of at least 30 watts, even for fine electronics.

06 Temperature

A second quality criterion is the heating element and specifically its power. To prevent the solder from melting properly or from solidifying too early, the temperature of the lead should not drop too much during soldering. Due to the much lower temperature of the parts to be soldered (room temperature), the temperature of the pin drops sharply as soon as you hold it against the parts and the heating element must be able to compensate for this immediately. For that reason, use a soldering iron of at least 30 watts, even for fine electronics. That is also the reason to choose a temperature-controlled soldering iron: above 400 degrees, most parts break quickly, so a heating element must be switched off when a certain temperature is reached. In practice, a temperature of just under 400 degrees works fine, even for lead-free alloys.

07 Soldering tin: lead or not?

Until just over a decade ago, everyone used an alloy of lead and tin to solder electronics. Lead-containing solder has been banned from use for equipment sold within the EU since 2006. For health reasons, it is recommended that you also work with lead-free solder, which consists of alloys of tin and copper and/or silver. The disadvantage of the lead-free alternatives is a higher melting point and dull joints. That means soldering at slightly (about 40 degrees) higher temperatures, so a slightly higher risk of damaging sensitive components. More importantly, it is more difficult to determine the quality of the connection, a dull connection with lead-tin solder is an indication of a bad weld. If you want to solder with lead-tin, you can still buy it.

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