How to solder: A beginners Guide

What is Soldering?

Soldering involves the joining of two or more metal objects like wires by melting a filler metal and flowing it into the joint. A filler metal usually has a low melting point. Soldering is performed to create a permanent joint between electronic components. 

A soldering iron is used to heat the metal to be soldered and then solder metal is melted at the joint to create a secure connection. While creating a joint, keep in mind that only the solder metal will melt at the connection and not the parts that you want to solder.

Solder can be considered as a metallic glue that keeps the components together and creates a connection that enables the flow of electric current. There is an option of a solderless breadboard to create a connection but if you need your circuit to work for long, you will consider soldering the component together.

In this article, we will talk about how to solder, how to solder wires and how to solder LED lighting strips as well as tips and tricks for successful soldering.

How to solder: A complete Guide

This guide will help you learn how to solder in easy steps and how to choose the right soldering iron and solder wires.

Step 1: Safety precautions

The majority of solder wires and solder paste contain lead metal as solder alloy is usually a mixture of lead and tin. While performing soldering, lead may give rise to fumes that are harmful to your health. Moreover, solder generally has flux in the middle of the wire. Flux with rosin generates dangerous fumes that can be hazardous to health if inhaled.

Here are the precautionary measures while performing a soldering operation:

•         Always perform soldering in a well-ventilated space
•         Make use of a smoke absorber
•         Never touch the tip of the soldering iron with your hand as it is extremely hot i.e. usually 350 to 400 degrees Celsius
•         Never put hot soldering iron on anything other than a proper iron stand
•         Use eye protection while soldering 
•         Don’t keep flammable materials and liquids near your work area
•         Always use pliers, tweezers, or clamps to hold wires to be heated to avoid any burn incident

Step 2: Choosing soldering iron and solder

The whole process of soldering depends on heat and this heat is generated by a soldering iron. There is a broad collection of soldering irons, soldering guns, and soldering stations available in the market. They come in a variety of sizes, shapes, and wattage. The right soldering iron for you is based on the specific soldering project that you want to do.

In general, for every soldering operation, you need a sufficient amount of heat to rapidly melt the solder metal and apply it to the joint where you want to create a connection. However, you don’t need too much heat that can melt or burn delicate electronic parts on the circuit board. If you ignore the temperature of soldering iron, the chances are high that you ruin your soldering project with high heat.

From many options of soldering irons, you can go for the one with 15 to 24 watts power as if the wattage will too high, it is likely to ruin the heat-sensitive components of the circuit or detachment of printed circuit board (PCB) tracks. Selecting temperature-controlled soldering iron makes the process much easier as you can precisely control the temperature and rest assured that soldering iron is not either too hot to burn components and hot enough to melt the solder wire.

A solder is required to perform the soldering operation. A commonly used solder alloy is the one having 40% lead (Pb) and 60% tin (Sn). Another one is the solder with 37% lead and 63% tin that works very well with small electronic components. Recently, there is an increase in the use of lead-free solder wires due to the generation of harmful lead fumes. Solders are usually available in the form of solder wires.

The solder wire must be of good quality to create a perfect connection. It is good to choose rosin core solder wires. Avoid using acid core solder that is used to connect plumbing metal joints and electric contacts as the acid is likely to corrode and damage the copper tracks of PCB. A good solder wire has 40% Lead and 60% Tin with 0.75 to 1mm in diameter.

Step 3: Preparing for soldering

Once you have the right soldering iron and solder wire, the next step is to prepare for soldering. Turn on the soldering iron or soldering station. Adjust the required temperature by moving the knob on the front panel. Many good quality soldering stations take 1 to 2 minutes to achieve the required temperature. Clean the tip of soldering iron before every use. You can do it by wiping it with a wet sponge when the tip is hot enough. 

A new soldering iron tip needs to be heated and covered with solder before using it for the first time. This process is known as the “tinning” of the tip. The point of tinning is to create a thin layer over the tip that delivers better heat transfer from the tip to the solder connection. The soldering iron tip will transfer heat well only when it is clean.

All parts of soldering iron need to be clean and free from contamination and oxidation. A good joint can’t be created with a dirty soldering surface. The solder will not adhere to the dirty components or pads on the PCB.  

Step 4: Soldering

Use a pair of clamps or tweezers to insert all the parts in the circuit board. When the soldering iron is heated up to the desired temperature, pick it up from the stand and hold it in your hand like a pen. Touch the tips of iron to the solder joint and keep it for a few seconds. Ensure that the tip of soldering iron touches both copper pad on the component lead and circuit board. If you heat only of both parts, it will lead to a poor connection. The area of contact between the solder joint and iron tip is known as the thermal linkage.

The contact between the surface of the solder joint and the soldering iron tip is a small straight like besides the tip of the iron. The thermal linkage can be considerably enhanced by the addition of a small quantity of solder to that line of contact among surface and iron tip. Molten solder creates a bridge between the solder joint and the iron tip. This bridge offers a quicker and better heat transfer into the solder joint.

Continue heating with a soldering iron and then apply solder to the joint. The solder must melt and quickly and smoothly flow onto the surface of the pad thus filling the gap between copper pad and component lead. Adding too few or too much solder are the two most common issues while performing soldering.

The soldering operation must be finished in than 2 seconds. The duration of the soldering process greatly depends on the soldering iron temperature and size of the joint. If you continue to heat the joint for more than 2 seconds, it is likely to break the conductors or pads on the circuit board or impair temperature-sensitive parts.

Hold the joint still for some time after removing the soldering iron and don’t move the circuit board for a couple of seconds to enable the connection to cool down and solder to solidify. 

Step 5: Inspection of solder joints

Start inspecting the solder joint visually right after the soldering. For proper inspection, a good magnifying lamp will be needed. Too little solder will lead to a weak connection while too much solder can cause bridging. A good solder joint must be smooth, shiny, bright, and volcano-shaped while bad joints are solder bridges, cold solder joints, or solder balls.

How to Solder Wires

Let's learn about how to solder wires together. For soldering wires, it is advisable to use helping hands or other sorts of clamp device.

Step 1: First you need to remove the insulation of both wires from the ends that you want to solder together. If you want to join the stranded wire, twist the strands with your fingers.

Step 2: Now heat the soldering iron and make sure it is fully heated before starting soldering. Now touch the end of one of both wires with the tip of soldering iron and hold it for 4 to 5 seconds. 

Step 3: Keep the soldering iron in place and touch the solder to the wire so that it is coated completely. Repeat the same process with another wire.

Step 4: Hold both wires on top of one another and touch both wires soldering iron. It will melt the solder and evenly cover both the wires. 

Step 5: Now remove the iron and wait a couple of seconds so that the connection cool down and harden firmly. Then cover the connection with the heat shrink.

How to solder LED Strip Lights

LED strip soldering is an easy process and here is how to do it.

Step 1: First, heat the soldering iron properly. For perfect results, tin and clean the tip of the soldering iron instantly before soldering. To tin, the tip of soldering iron, touch solder metal on both sides of the tip of soldering iron.

Step 2: Now you need to melt the solder wire on one LED strip segment that will be kept beneath the other. While performing soldering, apply heat to the specific area on the strip and not straight to the solder. Once enough heat has been applied to the target strip, begin adding solder.

Step 3: Arrange the other strip segment (non-tinned) over the tinned pads and apply heat. Keep the soldering iron intact until the solder melts again and starts to flow. To improve visual appeal and strengthen the bond, a small quantity of solder melt can be added to the top. 

Step 4: The LED strip light segments are connected now and electric current must flow through the complete length of the strip. 

Tips and Tricks for Successful Soldering

Here are some tips and tricks that will help you to practice successful soldering:

•          Properly clean the PCB joints with the help of a knife or blade to remove corroded material or dirt. The joint will be loose if it is dirty.
•          Choose the right soldering iron, preferably, a temperature-controlled soldering station or a cordless one.
•          Select the right type of vise or third hand
•          Choose the thinnest solder suitable for your task
•          For beginners, 60/40 solder is suggested 
•          Let your soldering iron reach the desired temperature
•          Select the appropriately sized tip for your task
•          Be careful while holding the soldering iron, so that it doesn’t burn your hand
•          First, apply the soldering iron to the joint and then the solder to the lead and let it flow and look for solder dripping
•          Avoid putting too much of solder on the joint as it will cause bridging
•          Clean the tip of soldering iron frequently with a tip cleaner, wet sponge or iron wool.
•          Avoid applying pressure on the iron
•          Hold the wires firmly to create a strong connection. Don’t move the joint while it is cooling and hardening. Don’t blow on the joint to cool it down. 
•          Clean the wires properly with a blade or knife to remove dirt or rust before soldering them. 
•          When you are done with soldering operation, cross-check the joints.  
•          If you are beginner, practice on a scrap before starting your project. Practice more and you will be a pro soon.