Soldering Tips

Soldering is a great skill for anyone wanting to work with electronics - and it can be fun! Whether you’re a beginner at soldering or not quite sure how to even get started, this quick guide will get you up and soldering in no time. I’ve included the tools I use for soldering and a list of some basic kits to play with for practice. I’ve also outlined some tips and tricks to get those good, solid connections.

Types of Soldering

Before we jump into the materials, let’s discuss the different types of soldering. In this post I share tips for doing through-hole soldering, sometimes called plated through-hole (PTH) soldering. This involves a printed circuit board (PCB) where electrical components, such as LEDs and resistors, can be inserted through the hole connectors and soldered.

Bottom and top of a PCB with some soldered components

The other type of soldering, surface mount, doesn’t have holes in the PCB. This type of soldering involves soldering paste. We won’t get into that here.

Solder

The word “solder” can refer to either the action of joining two pieces of metal or the metallic material used to do the soldering. Solder, the alloy material, originally contained lead, tin, and other metals. While leaded solder makes a great electrical connection and has a low melting point, as we now know, lead is also dangerous to our health.

Lead-free solder has now become the commonly used alloy in the production of electronics. Keep in mind when using lead-free solder that it contains a variety of other metals along with tin that require a higher melting point than leaded solder. Because of this requirement, most lead-free solder also include a chemical agent known as a flux core that assists with the melting and flowing.

When you choose solder for your project, consider these other options:

• leaded or lead-free - I suggest lead-free for the safety of your target users, such as kids.
• spool or tube - I use a tube for smaller projects, but if you plan to do a lot of soldering you might consider a spool.)
• gauge (diameter) - Solder comes in different gauges. Smaller gauges would be beneficial for small connections.

For this tutorial I chose to use a lead-free solder with a water soluble resin core. The gauge is 0.031” and comes in a 15 gram tube. The alloy is a mixture of 96.5% tin, 3.0% silver, and 0.5% copper.

Soldering Irons

The primary tool for soldering is the soldering iron. There are a variety of soldering irons, and they vary in price as well. Many believe that soldering irons transfer solder to the metal being joined together. It’s important to remember that the soldering iron only provides heat to melt the solder and start the flow. The iron doesn’t actually do the transferring of solder.

Some soldering iron wands, the handle where the iron is held, plug into a control box where the temperature of the iron’s tip can be adjusted. Others plug directly into an outlet and are set to one temperature. These less-expensive soldering irons may take longer to heat up, but are great for the traveling or small work areas.

Many soldering irons come with a standard conical or pointed tip, but you can purchase replacements as well as additional tip types and sizes. Bevel and chisel tips are two other common soldering iron tips.

For this tutorial I used a 30-watt Radio Shack soldering iron with a basic stand.

Tools

From left to right: solder, third hand, flush cutters, brass sponge, soldering iron conical tip in stand

There are several other tools that can help you have the best soldering experience. Here’s a complete list of my recommended tools and materials with links to these products on Sparkfun’s website:

• soldering iron - I recommend a 30- or 60-watt basic iron for beginners.
• soldering iron stand - A basic stand for low-end soldering irons with a cleaning sponge.
• brass sponge - These are helpful for cleaning off solder residue stuck on the soldering iron and should be used each time before you solder to keep your iron tips in good condition.
• solder vacuum (or sucker) - This tool is extremely helpful for removing solder mistakes from a PCB.
• flush cutters - You want a good wire cutting tool that will cut extra wire after soldering, preferably as flush to the PCB as possible.
• third hand or helping hands - Not required for soldering, but these are great for holding your PCB in place while using your hands to do the soldering.
• lead-free solder tube - Don’t forget the solder!

Soldering Process

CAUTION: When soldering, it’s always important to remember to hold the soldering iron by the wand rather than the metal part or tip. The soldering iron gets extremely hot and caution should be used when handling it. Also, it’s a good idea to solder in a well-ventilated area to keep yourself from breathing any stinky fumes.

1. Insert the leg(s) or wire(s) of your electrical component through the corresponding holes of your PCB.
2. Hold the soldering iron by the wand in one hand and the end of your solder in the other.
3. Place the edge of the soldering iron’s tip on one side of a leg so that it touches the leg and the copper contact that surrounds the PCB hole. (Never use the point of the soldering iron tip.)
4. Heat the leg and copper contact with the soldering iron on one side of the leg while touching the end of the solder to the leg and copper contact on the opposite side of the leg.
5. With the leg and copper contact heated, the solder will begin to flow around the through hole - solidifying the connection between the leg and the copper contact on the PCB.
6. Be sure to wash your hands when all the soldering is finished.

Soldering Tips

Diagram from Sparkfun (click on image to enlarge)

Soldering Practice Kits

Sparkfun’s Simon Says Through-Hole Soldering Kit - Featured in the video at the beginning of this post, this kit is great fun for everyone to play. For those more advanced coders and makers, you can reprogram the integrated chip included in this kit using an FTDI breakout board connection. Sparkfun provides the sample game code and full design files on GitHub.

Velleman’s Shaking Dice Kit - This kit is just fun to play with once assembled. Using a roller ball switch, the die is triggered by simple shaking it. The integrated circuit is programmed to randomized the number and sequence of the LEDs lit on the top PCB.