What Is Soldering?- Types And How To Solder

If you’ve ever taken apart an electronic item that included a circuit board, then you have undoubtedly come across soldered components. Soldering is the method used to connect two or more electronic components together.

When soldering, solder (an amalgamation of metals that typically includes tin and lead or a combination of metals) is melted around the connection and solidifies.

Soldering can join components and create a permanent connection, but it can also be undone using a desoldering tool.

We are going to cover everything soldering today. What is soldering? What soldering is used for? What does soldering look like?

What Is Soldering?

Soldering is joining process that makes a non-moving connection using different types of metals by utilizing a melted filler metal, namely solder.

Solder is a metal alloy, typically tin and lead, that gets hot with a soldering iron until it melts. The soldering iron is heated above 600 degrees Fahrenheit and once in contact with the solder, cools to form a very strong electrical connection.

During soldering, the soldered workpieces do not melt like in welding, but are heated to moult the solder, now in a liquid state, to make a connection. Similarly, brazing does not melt the workpiece metals either, but has higher filler melting temperatures than soldering.

In past decades, the solder used to join electronics had lead, however, due to environmental and health issues, lead-free alloys are being prescribed more often as the solder of choice for electronics and plumbing.

What is Solder?

Solder is a molten metal mixture with the ability to create a continuous bond between metal parts. In soldering, the solder is melted, which will allow it to flow onto the surfaces of the parts to be connected. The solder is then cooled so it solidifies in order to join the parts.

In order to use an alloy as a solder, the solder is melted at a lower temperature than the melting point of the parts it is connecting.

The solder must also resist oxidative and corrosive effects that can undermine the joint over time. The most common solder for electrical connections is manufactured with useful electrical properties as well.

Soft solder has a typical melting point range of 90 to 450 °C (190 to 840 °F; 360 to 720 K), and is found commonly in electronics, plumbing, and sheet metal work. The most common alloys that melt in the range of 180 to 190 °C (360 to 370 °F; 450 to 460 K).

If solder is employed using alloys with melting points higher than 450 °C (840 °F; 720 K) it is called “hard soldering”, sometimes termed “silver soldering”, sometimes referred to as brazing.

Some alloys are eutectic in particular proportions, which means the alloy’s melting point is the lowest melting point possible for all those components, the melting point coincides with the freezing point.

Non-eutectic alloys may demonstrate widely different solidus and liquidus temperatures, they have distinct solid and liquid transitions.

When non-eutectic mixtures reach hot enough temperatures before melting they often exist as a paste of solid particles, in a melted phase of the lower melting point component.

If the joint is disturbed in this “pasty” state before the joint has entirely solidified, worst case, a poor electrical connection may result; the use of eutectic solder limits this situation.

In plumbing, the pasty state of a non-eutectic solder is both useful and exploitable, and can be used to mold the solder while cooking, for instance to ensure watertight joints of pipes, which can create the so-called “wiped joint”.

For electrical and electronics work, solder wire is easily acquired in a number of thicknesses for hand soldering (manual soldering using a soldering iron or soldering gun), and is also supplied with a flux core – or as a room temperature paste, or as foil of a preformed shape fitting exacting to the workpiece which may allow for mechanistic mass-production, as well as in smaller “tabs” that can be wrapped around the joint and melted using a flame.

How Does Soldering Work?

Solder is liquid when melted by heat from an iron connected with a temperature controller. When the solder metal is heated to a temperature above its melting point at approximately 600 degrees Fahrenheit, it will melt and as it cools, will create the solder joint.

Not only does solder create strong electrical connections, but a desoldering tool will be used to remove solder.

Solder is a metal alloy used to make strong permanent connections like copper joints in printed circuit boards and copper tube joints.

Solder can also come in two different types and two different diameters, lead and lead-free, and the diameter of solder can range from 0.032″ to 0.062″. The flux is inside the solder, and is the material used to reinforce and provide improved mechanical properties.

What Metals Are Used?

Filler metal in soldering used to be lead-based (lead solder) and now with regulations plant lead-containing solders are being phased out in favor of many lead-free solders which can include antimony, bismuth, brass, copper, indium, tin or silver.

Which Flux Can Be Used for Soldering?

There will sometimes be contaminants, to include, oils, dirt or oxides, at the point of connection. Flux will prevent oxidation and often has a dry-cleaning effect on the metal.

The flux used in this area is rosin flux and it is a good flux for providing both mechanical strength and electrical contact of the electrical connections. Sometimes a wetting agent can also be used to enhance the wetting of the flux and reduce surface tension.

Different Types of Solders

There are 3 basic types of solder: lead-free or free of lead, lead, and flux. Lead-based soldiers are the most ideal and generally favoured in higher-risk applications such as medical electronics or aerospace.

There are so many solder types on the market today it can make it tough to find the best solder for your project or application. Luckily, there are mainly only three different solder categories, but we can use these to narrow the search:

• Lead-based solder initiated the electronics revolution. The predominant mixture is a tin/lead 60/40 mixture that melts around 180-190°C. This is called soft solder because the melting temperature was low enough for tin (the material chosen for its low melting temperature) and lead (chosen to lower the potential for tin whisker growth), and the tensile and shear strength properties were better with (up to) 100% tin.
• Lead-free solder has been developed as the EU began to limit the amount of lead allowed in consumer electronics, and manufacturers in the USA have been able to receive tax benefits for using lead-free solder. There are newer anneal processes that can mitigate tin whiskers along with various additives, including nickel, and use various conformal coatings. Lead-free solders generally have a higher melting point than conventional lead-based solders.
• Flux core solder is available in a “spool of wire” format and contains a reducing agent as a core. The flux is released when soldering and reduces (reverses the oxidation of) the metal at the contact point, providing a cleaner electrical connection. The flux also enhances the wetting properties of the solder. In electronics, rosin flux is generally used. Acid Cores are intended for metal repairs and plumbing, and not for electronics.

How To Solder

Soldering is the process of joining electronic component parts together by using solder and, subsequently, melting solder around the connection.

Solder is a metal alloy (usually of tin and lead) and when it cools, it creates a solid and strong electrical connection between the electronic parts. With soldering an electrical connection can easily be made permanent, but a permanent electircal connection can be removed with the use of a desoldering tool as described below.

To better explain how to solder, we are going to demo it in action in a real world example. In this case, we will solder an LED to a circuit board.

Step 1: Position The Component: First, place the leads from the LED through the holes in your circuit board. Next, turn the board over and bend the leads outwards at a 45 ‘angle. This will help the component form a better connection with the copper pad and keep it from falling out while soldering.

Step 2: Heat The Joint: Turn on your soldering iron and if you can adjust the heat, set it to 400’C. At this point, touch the tip of the iron to the copper pad and the LED lead at the same time. You will need to hold the soldering iron in this position for 3-4 seconds. This will ensure you heat both the copper pad and lead.

Step 3: Melt Solder To Joint: While you are holding the soldering iron on the copper pad and lead, tap the joint with your solder. IMPORTANT Do not touch the solder directly with the tip of the iron because you want the joint hot enough to melt the solder when tapped. If the joint is too cool, a poor joint will form.

Step 4: Cut The Leads Remove the soldering iron and allow the solder to cool naturally (do blow on the solder, it results in a poor joint). Now, you can cut the excess wire from the leads.

A good solder joint is smooth, shiny, and has the appearance of a volcano shape or cone. You want just enough solder to cover the entire joint, but not too much so it forms a ball or spills onto another lead or joint.

How To Solder Wires

It is now time to demonstrate to you how to solder wires together, and I would recommend using helping hands or any other sort of clamping mechanism for this part.

First, strip the insulation off the ends of both wires that you will solder together. If you have stranded wire, twist the strands together with your fingers. Next, make sure your soldering Iron is properly heated. Touch the soldering Irons tip to the end of one wire for 3-4 seconds holding the Iron by the wire.

While holding the Soldering Iron in place, touch the wire with the solder until the wire is completely coated. Now repeat this with the other wire. Now hold the two tinned wires on top of each other, and touch the soldering Iron to both wires. This should melt the solder and coat the wires well.

Remove the soldering iron and allow the solder joint to cool for a few seconds. You can slide down heat shrink tubing to cover the connection.

What is Desoldering?

In electronics, desoldering is removal of solder along with any components from a circuit board for troubleshooting, repair, replacement, and salvage.

Desoldering is simply melting the solder and taking away the joints made between two materials. In electronics, it means the removal of electronic components from PCB for troubleshooting, repairing, replacing, and salvaging. It is most often used for that reason.

To put it simply, desoldering is the exact opposite of soldering. You are undoing everything that you did in the soldering process. Desoldering, like soldering, is a complex process and can be done with a certain level of skill. This is done in more or less the same way carefully following safety precautions as described in soldering.

Methods of Desoldering

There are various ways of desoldering components. Each way requires different tools and different amount of soldering skill. The list below is a complete list of methods you can use to desolder components.

1. Using a Soldering Iron

A soldering iron is the least complicated and easiest tool you will use for desoldering components. You only need the soldering iron and a pair of fliers.

Here is what you have to do,

• Use the soldering iron to heat the solder until it begins to melt.
• With the tip of the iron, slightly push the pins and move the solder away from the joints.
• Use pliers to pull the components to remove them from the pinholes.
• When pulling the components, push down at their tips, not at their bodies, or you will damage them.

If you want to remove solder from holes, stick a safety pin inside the hole. This will suck the solder and help you to remove them easily.

Pros

• You only need a soldering iron to perform desoldering.
• You can reuse the desoldered components.

Cons

• If you use the soldering iron for too long, you may damage the board.

2. Using a Soldering Wick

The soldering wick method of removal is simple and quick to get rid of unwanted solder after soldering. Soldering wick is simply copper coils woven and weaved together, which makes it also called desoldering braid.

Soldering wick is made out of copper wires because copper is a good conductor of heat. Since solder is attracted to heat, the copper wires will suck up solder from a solder point.

Some soldering wicks are impregnated or treated with flux which allows solder to be removed even easier. If your soldering wick does not have any flux, you can dip the end of the wick in some flux to speed the process of removing solder.

Here is what you have to do to remove the solder,

• Twist a few inches of copper wire together to make a braid.
• Dip a small portion of the braid into flux to apply some flux to the copper braid.
• Place a portion of solder wick on top of the joint to be desoldered.
• Place your hot iron at the tip of the solder wick and at the pin that you want to remove solder from.
• Be patient and wait for a few seconds for the solder to melt and allow the solder wick to soak up the melted solder.
• Once you have soaked up the solder, take the solder wick and cut off the portion that is covered with solder.
• Now repeat the same process until you have removed all of the unwanted solder.

While handling the solder wick, ensure that you do not touch it using your hands as it will be very hot. Use a pair of pliers to hold and position it.

Pros

• The process being described is inexpensive, uncomplicated, and straightforward.
• This method is excellent for desoldering flat surfaces.
• You can use a solder wick of any size based on the amount of solder to be desoldered.
• Desoldered components can be reused.

Cons

• It is not possible to reuse the soldering wick; you need to cut the part that has solder on it.
• Because the soldering wick gets very hot, it may be difficult to place against the joint.
• This method is not effective for getting solder from pinholes.

3. Using a Desoldering Pump

In this approach, a desoldering pump is used to suction solder out of the solder joint. A desoldering pump is not much more than a small high-pressure vacuum pump. However, before you can use the pump to suction the solder out, you have to melt and heat the solder.

Here are the steps to use the desoldering pump to remove the solder,

• Utilize the soldering iron to heat the solder until it liquefies.
• Squeeze the bulb or press down the plunger of the desoldering pump and place it on the molten solder.
• Release the bulb to suck up the solder.
• Some desoldering pumps will have a release button so you do not have to keep squeezing the bulb.
• Remove the desoldered components.
• Repeat the above steps until you remove the leftover solder.

Certain desoldering pumps are packaged with a soldering iron, so you aren’t obliged to procure a soldering iron separately. You can remove the solder in the desoldering pump simply by squeezing the bulb, releasing it, then squeezing it again.

Pros

• Desoldering pumps are available in various designs and operating mechanisms to make things easier for you.
• This method works well for removing solder from pinholes and desoldering small components.
• You can reuse the desoldered components.

Cons

• Most desoldering pumps are large. So, you will find it difficult to get them into tight spaces.

4. Using a Heat Gun

A heat gun operates similarly to a soldering iron, by heating the solder so that you can pull the components off. You can also accomplish this task with a hot air station as well instead of a heat gun. Although it is very effective, it is also quite costly.

Here is how to desolder components using a heat gun,

• Turn on the heat gun.
• Hold the PCB firmly using a stand or pliers.
• Hold the tip of the heat gun against the solder until it melts.
• Remove the components using a pair of pliers.

When using the heat gun, ensure that you do not hold it against the board for too long. Otherwise, you will melt or damage the board.

Pros

• You can desolder and remove the components in a few seconds.
• You can reuse the desoldered components.

Cons

• As it heats the components very quickly, it damages the components in most cases and makes them unusable. In some cases, it also damages the board. If you are not careful, you can injure yourself as well during the process.

FAQs