PCB Soldering Techniques: The Complete Guide
As technology advances, so do the requirements for printed circuit boards (PCBs). The ability to solder PCBs is essential for anyone looking to work with electronics and develop their own projects. But with so many soldering techniques available, how do you know which one to choose?
If you’re looking to learn more about PCB soldering techniques, you’re in the right place. In this complete guide, we’ll cover everything from the basics of soldering to advanced techniques used by professionals. Whether you’re a beginner or an experienced electronics enthusiast, this guide will give you the knowledge you need to start soldering PCBs with confidence. So, let’s get started on our journey to mastering the art of PCB soldering.
What Is Soldering?
Soldering is the process used for joining metals together using a type of filler metal called solder. PCB manufacturing relies on soldering to join electronic parts. Solder joins components to pads on the circuit board.
PCB soldering involves heating the tip of a soldering iron to a high temperature. Solder wire is placed between the components and the soldering iron. The heat from the soldering iron melts the wire, which fuses with the metal of the components and PCB as it cools.
Tools Required for Soldering
PCB soldering requires the use of several tools and supplies, including solder flux, solder wire, and a soldering iron. Here is a closer look at these essential items.
Solder Flux
Solder flux provides several beneficial functions during the soldering process. It is often sold as a paste-like substance.
Flux acts as a cleaning agent for removing impurities from the PCB and electronic components. Removing impurities helps ensure a stronger bond. Using solder flux also prevents oxidation, which further increases the strength of the solder joint.
Flux is also very useful for beginners, as it makes soldering more forgiving and helps keep the solder in place. When the solder wire melts, it travels the path of least resistance, which includes the area covered with flux.
Solder Wire
Solder wire is made of various metal alloys with low melting points. The wire is typically divided into two groups – lead solder and lead-free solder. The most common lead solder includes a combination of 60% tin and 40% lead and has a melting point of about 350 degrees Fahrenheit.
The most common lead-free solder includes a tin and copper combination. It has a higher melting point compared to lead solder but can produce a stronger bond.
Soldering Iron
A soldering iron is necessary for heating and melting the solder wire. Soldering irons are available in many different designs, including simple handheld irons and soldering stations.
Soldering irons feature removable tips. The end of the soldering iron tip may include a chisel, conical, beveled, or bent tip.
Oxides and other impurities can gradually blacken the tip of a soldering iron, which limits its ability to transfer heat. Proper cleaning and maintenance can help prolong the life of your soldering iron tips.
There are also many tools available to help with the soldering task, including a soldering wick, magnifying glass, a PCB holder, and a soldering mat. While these tools are not essential, they can help with each stage of the soldering process.
What Are the Different Types of Soldering Techniques?
Soft soldering and hard soldering are the two main categories of soldering techniques.
Soft soldering involves joining metals using a solder wire that melts at temperatures up to 450 degrees Celsius (842 degrees Fahrenheit). Tin-lead solder and tin-copper solder have low melting points.
Hard soldering involves joining metals with temperatures exceeding 450 degrees Celsius, which means that it is technically a form of brazing. Brass is also typically used instead of a tin-lead alloy, as it has a higher melting point.
Soft soldering is the more common soldering technique, especially for PCB soldering. Using filler metal with a lower melting point puts less stress on the electrical components and circuit board.
How to Solder on a PCB?
PCB soldering is a relatively simple process, but involves several steps:
- Preparing your work area
- Applying solder flux to the PCB
- Positioning the electronic component
- Turning on the soldering iron
- Tinning the tip of the soldering iron
- Heating the solder joint
- Soldering the joint
1. Preparing Your Work Area
Solder in a room with good ventilation. You may even want to use a fan to help remove fumes and smoke from the solder flux and wire as they melt.
Work in a clean area with plenty of arm room to avoid accidentally burning other objects with the soldering iron. Soldering at a clean workstation also decreases the risk of contaminating the PCB with dust and other particles.
2. Applying Solder Flux to the PCB
Apply a small amount of solder flux to the pads or vias on the circuit board where you want to connect a component. The flux spreads across connected copper paths as it melts, so you only need a very small amount.
3. Positioning the Electronic Component
Place the component on the circuit board. The pins on the component should connect with the pads and flux on the PCB.
4. Turning on the Soldering Iron
With the work area and components prepared, turn on the soldering iron. Set the temperature to the desired setting based on the melting point of the solder wire that you use.
5. Tinning the Tip of the Soldering Iron
Tin the tip of the soldering iron as the temperature rises. Tinning protects the tip of the soldering iron from oxidation, which makes it less effective over time.
You can use a tinning powder or melt a small amount of solder wire on the end of the soldering iron tip. Wipe the tip on a brass coil to remove excess solder.
6. Heating the Solder Joint
Touch the tip of the soldering iron to the area that you want to solder. Heat the pins and PCB for one to two seconds. Preheating the components and PCB will help them bond with the solder as it melts.
7. Soldering the Joint
Hold the solder wire between the joint and the soldering iron tip. Touch the solder wire to the joint. It should start to melt from the heat applied in the previous step. However, you may need to move the soldering iron tip closer until the solder wire begins to flow freely.
After the solder wire starts to flow, pull the soldering iron back. The joint will start to cool and harden instantly, creating a small mound.
Useful Tips for PCB Soldering
The steps described should allow you to start PCB soldering with ease. However, the following tips can increase your chances of producing quality solder joints:
- Keep the tip of the soldering clean and tinned. After every two to three joints, clean and tin the tip for better heat conduction.
- Avoid applying heat for a prolonged period. Always start with the lowest temperature setting for the solder wire that you are working with to avoid damaging components.
- Consider using a magnifying glass to inspect the solder joints.
- Solder small parts, such as transistors and resistors, before soldering large parts, such as ICs. Starting with smaller parts makes it easier to reach all areas of the board.
- If the solder wire appears to melt too quickly or fails to bond, try using a lower temperature.
Summary
PCB soldering is necessary for connecting components to a circuit board. Soft soldering is the most used technique, as it involves the use of solder wire with a lower melting point.
If you plan to start PCB soldering, you will need a soldering iron, solder wire, and solder flux. Most handheld soldering irons are designed for soft soldering and include a max temperature that can accommodate all types of solder wire.
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