There are several methods of soldering, yet they all give the same result. It connects two distinct metals with the use of different types of solder material. Solder comes in a variety of materials.
The most common solder comes in metal alloy, which includes a mixture of tin or lead and brass or silver at very low MP. The solder starts melting when it comes in contact with hot soldering iron during the soldering process.
However, solder acts as an epoxy or glue that combines different parts of the board together.
The process of soldering on a circuit board or PCB refers to PCB assembly or PCBA. PCBA refers to a circuit board that contains copper plates, wires, and electrical components on it. PCBA plays an essential part in consumer electronic devices that we use daily. Consumer electronic products like smartphones, routers, computers, ovens, microwaves, refrigerators, and all contain PCBA in them. Moreover, it is also used in other fields of life like automobile, telecommunication, medicine, military, defense, and aerospace.
Types Of PCB Soldering Methods
PCB soldering refers to a process of combining more than two components together on the circuit board surface. Soldering plays an essential role in the designing process of a circuit board, as soldering is the only method to attach the circuit to a board or panel.
The three most common and widely used soldering methods involve Hand Soldering, Wave Soldering, and Reflow Soldering. Hand soldering, as the name suggests, performs manually, while wave and reflow soldering uses SMT or surface-mount machines to perform.
Hand soldering refers to a type of process in which humans apply pressure manually with a soldering iron pre-tinned tip. This heats up the solder and melts it.
However, hand soldering also refers to soft soldering in the field. It happens because hand soldering requires a temperature below 400 degrees Celsius. The metal alloy of solder contains lead in it which has an MP or melting point lower than 350 degrees. Volatile or fusible electrical components need less heat during soldering to avoid any damage. Therefore, make sure to use temperature at the lowest possible level so it won’t melt the metal. This, however, gives a “soft” connection or joint.
PCB hand soldering uses rework and Thermaltronics soldering equipment. It refers to the very last step of assembly, which requires complete details for SMT or THT components. SMT refers to a process in which components attach directly to the PCB surface. The device that uses this method to incorporate components serves as an SMD or SM device. At the same time, THT refers to a process in which electrical components are inserted in the PCB using holes and wires and soldered on the other side of the pads.
Moreover, hand soldering needs quite a lot of experience and knowledge to master the technique. The majority of engineers and assemblers consider it one of the simplest techniques. Yet it comes with both benefits and drawbacks.
Pros of Hand Soldering
Hand soldering allows the creation of a reliable electrical connection joint. Moreover, it is ideal, especially for smaller electrical components.
Cons of Hand Soldering
Hand soldering does not allow for higher temperatures. Therefore, it does not create a strong joint. Moreover, you cannot use it on devices with higher loads.
Hand Soldering & Assembly Rework
The process of hand soldering needs two main components to commence. A solder and soldering iron. Solder refers to a metal alloy that acts as an epoxy to joint components. While soldering, irony refers to a source of heat that melts solder around the electrical components. Irons come with different Watt ranges. Soldering irons with a range between 15W-60W gives good results. Moreover, a higher watt range may damage the board or the component.
Steps Of Hand Soldering
· Component Placement
Component placement comes as the very first step in the hand soldering process. First of all, clean the board to remove any type of dirt. Bend the wires or leads. Put the electrical component through the holes present on the panel. To ensure the right placement of the component, bend the wire from the board’s bottom at an angle of 45 degrees. Once the component fits in its right place, move forward. Extend the leads from electrical components to relieve their stress. Make sure the bend must remain two diameters of lead from the electrical component. The bend’s internal radius must equal one lead diameter. Also, the placement must show all the electrical parts.
· Preparing The Soldering Iron
Put the soldering tip on the joint in such a manner that it shows visible visuals of the contact point during the process of soldering. The angle must be 45 degrees. Make sure to clean the tip of the soldering iron and tin it well before using it. Furthermore, a freshly new tip that you have never used before must be tinned right after the solder reaches its melting point. Tinning refers to applying fresh flux and solder to the soldering tip. This coats all the soldering surfaces with the solder.
When the iron gets cold, wrap it with the soldering wire. Heat the soldering iron until the solder starts melting. Wait until the surface of the tip is completely wet. Wipe off any extra solder paste from the tip, then move on to the soldering. Also, remember if tinning does not complete efficiently, it may lead to an oxidized tip which makes the soldering process harder and more difficult.
To remove the oxidized part, copper tips can go with filing. However, the already-plated tip does not need any filling. Cool down the tip for a bit and use a wiring brush to brush off the stubborn brown or black oxidized material. Keep on brushing until the oxidized material removes. You can also use find files or sandpaper.
Once the oxidized material is removed, start the tinning process. Make sure not to sand or fill the plated tips. Moreover, if the tip does not have any oxidation and tin well, then just clean it with wipes, or damp sponge, or any other material before soldering. Place a tiny solder ball on the soldering tip surface, which helps as the contact point with electrical components in the soldering.
· Apply Heat
The iron tip of the soldering iron must touch the metal of the board and the electrical components firmly to create a connection. Apply heat on both parts until the solder melts down and gives off a strong joint. Put the solder around the electrical components. Take off the soldering tip as the joint form to prevent overheating the solder paste. Make sure to complete the process of soldering within just 2 seconds. However, if anyhow, the soldering takes 5 secs; then it may happen because of the incorrect method, small soldering iron, or too small soldering iron tip.
Make sure the tip of the soldering iron has a temperature of 343 degrees Celsius. Moreover, both metals must have a surface temperature above the melting point of the solder to accomplish efficient wetting. Make sure not to allow the solder to flow on a cooler surface than the temperature of the solder, as it may create “cold” joints. An adequate amount of solder flow and melt smoothly over the surface. Thus, giving a shiny, smooth, smooth straight thin edge. Whereas, if it gives a granular, irregular, dull, lumpy, and rounded look, then it means that the application of solder does not go well.
· Remove Heat
Once the solder coats the pad’s surface, stop applying more solder and take up the iron tip from the board. Do not touch or move the solder joint for about a few seconds. Allow it to cool down, as moving the joint will give off a cold joint.
· Finishing The Solder Joint
Cut off extra leads. Make sure not to fall for irregular solder edges. Also, leave a tiny headroom as it does not let the solder separate from leads on getting shocks during cutting.
Hand Soldering For Through-Hole Components
Once you gather all the hand-soldering equipment and components, start the process with the following steps.
- Clean the components leads and PCB thoroughly. Otherwise, it may create poor soldering joints.
- Apply the solder paste on the electrical components and leads of the circuit board that needs soldering.
- Heat the soldering iron at the required temperature.
- Grab the soldering iron and soldering lead in each hand. In this, use a reel stand to maintain adequate tension and angle.
- Identify the exact point where copper and leads of electrical components meet with each on the PCB. Put the soldering lead on that point and start applying heat.
- Cut off the excess leads.
- Look out for errors and irregularities. And try to resolve the problems.
Similarly, the soldering process works differently for SM assembly than the TH assembly. Do not lose hope if you don’t succeed in your first attempt at hand soldering. It considers the simplest method of all soldering processes, yet it needs extra care and attention while doing so. Therefore, keep practicing until you experience all of it. Hence, you will get a perfect joint PCBA in the end.