Introduction

You can’t imagine entering the world of DIY electronics without working on your soldering skills. Learning how to solder with proper soldering techniques is a fundamental skill that anyone can acquire.

Soldering isn’t as hard as it seems. With the right tools, some simple techniques, and a lot of practice you will be soon able to assemble or fix any piece of electronics. Of course, your first solder won’t be perfect but with time they will get better and better.

In this article, we outlined the basics of through-hole soldering and give you some tips and tricks for proper soldering and desoldering. But first, let’s make sure we’ve got the right equipment.

What is a Soldering Iron

A soldering Iron is the instrument used to melt a filler metal (solder) that will join two or more items together. This will create a permanent connection between electronic components that will last forever (well almost). Inside each soldering iron is a nickel-chromium resistor that will heat up the tip at a temperature between 280°C and 450°C.

It comes in different sizes and shapes and with different price rating. Even for beginners, I would recommend starting with a temperature-controlled Irons, you can find some that are not that expensive and it will be a good investment. Best brands on the market (according to me): Weller and Hakko.

Here is a list of the few characteristics that you should pay attention to when choosing a soldering Iron:

Solder

Solder is a metal alloy material that is melted to create a permanent bond between electrical elements. It is usually composed of a Tin/Lead alloy that melts at a temperature of about 200°C. Modern lead-free solder is an alloy of tin with various metals such as copper or silver and has a slightly higher melting point.

A word on leaded solder. In the industry, it is now forbidden to use leaded solder, as well as other substances, due to health concerns. This is your choice to use leaded solder or not, but remember that in any case, you should work in a well ventilated-area as both lead and flux are volatile and toxic, and wash your hands after soldering.

Inside the solder core, there is a material known as flux which will melt at the same time as the solder alloy. This flux act as a deoxidant that will burn the little oxide layer on PCB pads and on component leads. This is the reason you should never melt the solder on the tip of the iron but on the PCB pad. The goal here is to use the flux to clean the metallic surface which will improve electrical contact and mechanical strength.

For hobby electronics, the most common solder is the 60/40 (60% tin, 40% lead). 50/50 or 33/67 soldiers should not be used as they have an acid core that will damage your components and your board.

Safety precautions

• Never touch the tip of the soldering iron.
• Always put back the soldering iron to its stand when not in use.
• Work in a well-ventilated area: the smoke formed as you melt solder is mostly from the flux and it is toxic.
• Wash your hands after soldering: solder contains lead.

How to solder: step by step

Preparing the soldering Iron

• Choose which iron tip you will use and screw it tightly in place.
• Turn on your Soldering Iron. The iron will take a few minutes to reach its temperature.
• Dampen the sponge in the holding stand. Remember it should be damp, not completely wet.
• Tin the tip to improve the heat transfer from the iron to the component lead.
  • Clean the tip of the Iron on the damp sponge.
  • Melt a little solder on the tip Iron.
  • Clean again the tip of the Iron on the damp sponge.

Let’s solder

• Mount the component you want to solder onto the board.
• Apply the tip of your soldering iron on both PCB pad and component lead in order to heat them up.
• Apply solder on the PCB pad. Don’t put the solder on the iron tip, the solder should melt due to pad heat.
• Keep applying the soldering iron for 2 or 3 seconds, this aims to allow the deoxidant to burn the oxides that may be on the metallic surfaces.
• Check your solder, the goal is to make a nice volcano shape soldering. A good solder keeps a nice silver color with a smooth shiny aspect.
• If you need to redo the soldering, reapply a bit of fresh solder (not too much) or use a flux pen.
• Clean your iron tip on your damp sponge.

Soldering Tips

How to hold your component while soldering

To make the soldering process easier, it might be tempting to bend the leads of your components to prevent the part from falling out when the PCB is held upside down with components unsoldered.

Make sure you do not bend too much, 45° is a maximum. I’ve seen a lot of videos where makers are bending the leads to a 90° angle: this is madness! With this kind of angle, you will damage your PCB when cutting the leads and you will have a really hard time when you will need to desolder.

How to mount basic components onto PCB

How to Desolder using a desoldering braid

The desoldering braid is in fact, as its name says, made of a braid of copper wires, coated with flux. The interstices between the wires suck up the solder, which thus disappears from the place where it is no longer wanted. It is sold in the form of small coils of a few meters.

Desoldering step by step

• Position a piece of clean desoldering braid on the solder to be undone and place the soldering iron on the braid.
• Press the soldering iron to establish good thermal contact. The solder rises by capillarity into the braid.
• The color of the braid will start changing from its original copper color to an increasingly metallic gray color as it sucks in more solder.
• It may be necessary to have to repeat this operation a second time to obtain a perfectly clean spot. the first braid was there to remove as much solder as possible.
• With a little practice, it then becomes possible to slide the braid under the Iron.
• Sometimes, it may be necessary to add some fresh solder to an old solder to facilitate the fusion of the old joint.