Soldering Tips

Soldering, despite first appearing to be a magical and arcane process, is actually quite easy once you know how. Like most things, it’s even easier if you use a few tricks of the trade.

Holding things in place

  1. Blu-Tack

    Blu-Tack is the solderer's best friend. It’s heat resistant enough to hold a component or components in place while you solder them.

    If you ever have to solder more than one component to a PCB, you’ll quickly find the process of trimming the leads, bending them into place, pushing it through the PCB and soldering to be tedious. It’s much easier to simply prepare all of your components, carefully place them, apply a generous amount of Blu-Tack to keep them still and do all of your soldering in one go. This also means your PCB will warm up, and stay warm, making the process even quicker.

    Blu-Tack can also be used to prop a PCB up, or stop it rocking about during more delicate operations. Blu-Tack is also easy to remove afterwards, simply pull it off and dab away the excess.

  2. Breadboards

    If you don’t have a "helping hand" clamp handy, then you’ll find that a breadboard is useful for holding headers in place while you solder them. If you want to get your headers perfectly aligned, simply push them into your breadboard, drop the PCB on top and solder.

    If the PCB only has pins on one side, you can grab some Blu-Tack to prop it up. Apply a generous blob and then keep pressing down until the PCB is level and the headers are properly aligned. Don’t worry about your breadboard getting hot, the metal contacts inside will spread and disperse the heat- like tiny little heat sinks!

  3. Perfboard

    An alternative to using breadboards to align headers is the humble perfboard. Just drop your header into a sheet of perfboard, stick your PCB on top, keep everything secure with Blu-Tack and solder away. Perfboard is thin enough to keep in a little soldering essentials kit, and it wont matter if you accidentally burn it with the iron.

  4. Helping hands

    Don’t conscript someone to hold components for you, they get hot, really hot! A soldering "helping hand" is basically just a pair of crocodile clips and usually a magnifying glass on goose-neck arms. You can pick one up for about £8.

    Alternatively, if you’re an avid DIY-er, you can assemble your own set of helping hands out of heavy duty uninsulated crocodile clips and heavy gauge wire or re-purposed metal coat hanger. This is more of an academic exercise than anything I think would pan out to be useful, since a real Helping Hand is cheap and much more robust.

    The arms used in our helping hands are made from flexible water pipe - used for accurately positioning cooling jets at crucial places on an assembly line.

Splicing wires

  1. Multi-core wire

    Multi-core wire is wire that has lots of tiny wires inside it, all wrapped together in a little braid. If you want to join two multi-core wire ends together, then you’re going to need to start by "tinning" them.

    Tinning is the process of heating your wire end on the soldering iron tip, and applying a little solder. You want to get the solder to melt into the wire braid for both ends, so you can simply re-melt them together once they’re prepared.

    You can then either lay the wires one on top of the other, or twist them tightly together with pliers to form a strong mechanical join. Finally, fix everything in place by re-melting the solder to join the wires.

  2. Single-core wire

    Single-core wire isn’t quite so easy to twist together, and can result in bulky or messy joints. A simple way to join it, although it’s not necessarily as mechanically strong as it could be, is to tin both wires, lay one on top of the other, and melt the solder together.

    If you need an extremely strong joint, you could try twisting together a "Western Union Splice". This is a little bit like a reef-knot. Rather than crossing the strands into an X and twisting them together as you would multi-core wire, the Western Union Splice involves twisting the wires together once, and then wrapping the excess wire in a coil around the opposite wire.

    This joint is so strong that you won't even need to solder it, but a bit of solder applied afterwards and some heat-shrink over the top will give you a robust and tidy joint that should keep your robotics projects running reliably.

IC sockets

The usefulness of IC sockets cannot be overstated, and you probably shouldn’t ever solder an IC directly to a project unless it’s a final, mass production design. Not only does using an IC socket let you replace an IC if it blows up, but it also lets you use your less common and more expensive ICs across multiple projects.

For example, if you build a Shrimp, or Pico PiDuino (a compact, homemade Arduino-compatible circuit) on perfboard, then you’re going to want an IC socket so you can replace or re-use that costly microcontroller!

IC sockets will also never really have a problem with heat, since they have no delicate parts. You can mess up soldering on an IC socket with little to no ill effect. Do the same with the IC itself and you’re probably going to have a bad time.

Making good

Once you’ve finished soldering, you might want to apply various finishes to both make your project more robust, and electrically insulate it from any rogue wires or components you’ve let invade your experimentation area.

  1. Heat shrink

    Heat shrink is your best friend for keeping spliced wires in tip-top condition, insulating joints and generally making your giant blobs of malformed solder look presentable.

  2. Hot glue

    Another commonly used tool in the solderers armada is hot glue. This is great stuff for adding a bit of mechanical strength to joints and insulating surface mount components. You’ll even find it inside various electrical products, such as HDMI switchers. Electrical components are designed to withstand the heat of soldering, so a little hot glue won’t do them any harm.

  3. Project boxes

    Maplin stock a variety of little black, nondescript boxes that, when combined with a Dremel Rotary Tool and a little deft work milling out holes for your wires/sockets, make really great protective boxes for larger, more permanent projects. You can even fill smaller enclosures with hot glue, do this well enough and you’ll get a pretty good weatherproof result, but you’re never going to get it unglued again to repair any components you might blow.

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Raspberry Pi

Phil Howard
Phil is Pimoroni's software guru, instantly recognisable by his somewhat pirate-themed moustache growing attempts. Usually found buried neck deep in Python libraries, he's also been known to escape on occasion and turn out crazy new products. If you need a helping hand, he's a prolific Twitter user and rampages around the forums like a T-Rex. Ask him if you need help with Pimoroni's software libraries, or Propeller HAT.