How to Solder

The most critical skill in electronics is soldering. Learning how to solder is not a difficult task.

This “How to solder” guide is not going to be one of those guides where I boringly and very technically explain each particular step in the procedure and then you copy what I do. You may duplicate what I am doing but you will forget it as soon as you finish your soldering project.

The idea of this guide s that you learn the logic and process that is involved in soldering. This way you will be able to practice how to solder and build other soldering projects. Once when you understand a basic of soldering and get familiar with soldering tools you will be able to build stunning circuit boards or repair of a complex PCBs.

For some people soldering is a simple task performed with a soldering iron and a piece of solder. However, the soldering of the printed circuit board is a fine art of making reliable electrical connections. Knowing how to solder is handy when you building or repairing electronic devices and circuit boards.

Soldering is the process of joining certain metals by melting and flowing a filler metal alloy into the joint. Melted metal alloy, usually called solder, makes an electrical and mechanical connection in the joining place.

Safety precautions before soldering

Solder in a well-ventilated area or use smoke absorber. The soldering process produces fumes. Smoke absorber absorbs most of the smoke from flux and solder.

Keep flammable liquids and materials away from the work area

Soldering iron is HOT. Never touch the tip of the soldering iron

Never set your hot soldering iron down on anything other than a soldering iron stand

Never cut off a grounding prong on a soldering iron plug to make it fit an ungrounded receptacle

Hold wires to be heated with tweezers, pliers or clamps to avoid receiving burns from objects that are heated

Always wash your hands with soap and water after soldering

Wear eye protection

Soldering tools

Preparation for soldering with a soldering iron:

Preparation for soldering with a soldering elect and install the proper iron tip for your application while soldering iron is still cold

Adjusting temperature on the temperature controlled iron

Turn on your soldering station. Set desired temperature on soldering station in range 625-750 degrees F (330- 400 degrees C). Solder melts at around 370 degrees F (188 C).
Solder is an alloy of two metals; usually tin and lead at a rate of 60/40 (60 % tin, 40% lead) or 63/37. Solder alloy could be a combination of other metals. A variety of solder alloys are used in the soldering industry, however, a huge majority of solder alloys are still tin-lead alloys.

Trend is to avoid the use of lead in alloys and replace it with another metal such as silver. Leaded solder alloys offer a low melting point and increased reliability over lead-free solder alternatives.

Sponge on soldering iron

Dampen the sponge in the stand (the sponge should be damp, not soaking wet). Turn on the smoke absorber if you have one.

Soldering flux

Clean the soldering area and dirty components. All components must be clean and free from oxidation, grease, and other contamination. The solder will not stick to a dirty component or dirty area on the printed circuit board. You can use an approved solvent or cleaner.

Tip of the soldering iron must be clean as well. Clean the tip of soldering iron using by wiping on a damp sponge. If necessary, use brass wire tip cleaner to clean the tip of all residual solder and oxidation by inserting the tip and twisting a few times.

Before soldering, the tip of soldering iron should be “tinned” or, in other words, coated with solder. Apply some solder on each side of the tip end, then wipe on the damp sponge.

If you are soldering static sensitive components, wear anti-static protection (ESD) like a wrist strap.

How to Solder Circuit Boards

Inserting component in circuit board

Spread component’s leads to fit through the circuit board. Insert component into a metalized hole of the circuit board. Bend the component’s leads outward to prevent it from falling out.

How to solder circuit boards

Position the iron’s tip gently on the joint and hold for few seconds. Make sure it touches both: the component lead and the pad on the circuit board.

Hold soldering pencil at a 45-degree angle to circuit board surface and apply gentle pressure.
One of the most common mistakes that beginners in soldering make in this step is that they strongly push soldering iron to the soldering joint hoping that the stronger they push the more heat will be delivered to the soldering joint. This can end up damaging the circuit board or soldering pencil. There is no need for hard pressure - just position the tip gently to the soldering joint. Downward pressure against soldering joint must be minimized to avoid damaging, burning or lifting soldering pads and thin copper conductors on the circuit board.

Continue heating and apply some solder to the joint. The solder can be in form of solder wire or solder paste.

Don’t apply solder directly to the tip of the soldering iron. Heating one part but not the other will result in poorly formed joints. The solder should melt and flow smoothly onto the track and component lead to form a volcano shape.

The most common problems with soldering are adding too much or not enough solder.

How to cut component leads

It only takes a couple of seconds to make a perfect joint. The heating period depends on the temperature of your soldering iron and the size of the joint.

Remove the solder, then remove the soldering iron while keeping the joint still. Do not move the circuit board for a few seconds to allow the joint to cool.

Cut the surplus wire leads off with small cutters.

Good soldering joint

Inspect soldered joints.

Adjacent components may be bridged together or the joint may need additional solder for good electrical continuity. Shake the leads softly to make sure that there are no loose gaps in joints.

Good soldering joint is bright and shiny while bad solder joint has a frosted appearance. Cold solder joints are caused by insufficient heat. Good soldering technique combined with a little effort spent to make a perfect soldering joint may save a lot of time later in troubleshooting a defect caused by a bad soldering joint on the circuit board. Always clean and tin the iron’s tip when you are finished with soldering. Proper tinning will prevent oxidation and significantly extend tip life

How to solder Electronics

How to solder electronics depends on the package and size of electronic components to be soldered and soldering tools we are using.

Over the past several years, technology has caused dramatic changes in the way electronic devices are designed and this has changed ways how to solder electronics. In too many cases, the soldering skills and soldering techniques have kept pace with technological improvements in the design of electronic devices.

There are major differences between techniques and processes used in the manufacture of circuit boards and those required for repair them. With the advent of miniaturization of electronic components and switching from through-hole parts to surface-mount packages, the technique of soldering has significantly changed.

Updated: February 22, 2021