The PCB manufacturing process is a complex one, broken into a multitude of steps. Each process is equally tricky to work with, especially if you’re a beginner. To help out beginners like yourselves we’ve come up with this overview of the PCB “Soldering” process. A very sensitive process explained by PCBgogo that, depending on whether or not it’s done right, can make or break your PCB. 
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What is PCB Soldering?
Contents
First things first, let’s look at what PCB soldering exactly is. Soldering itself is a process in which two metals are joined together using solder (a tin-lead metal alloy) which is first heated at high temperatures and then cooled to create a strong electrical bond.
This process is incorporated into the PCB manufacturing process in which electrical components are connected to the surface of the Printed Circuit Board.
During PCB soldering, a soldering “iron” is used to melt the solder. Once melted, the solder will act as an adhesive, joining the two parts together. The solder will solidify once cooled and form a strong connection between both ends.
Types of PCB Soldering Methods Explained by PCBgogo
There are two main types of PCB soldering methods/techniques i.e. soft soldering and hard soldering. Hard soldering is further subdivided into two steps, silver soldering and brazes soldering.
Soft soldering will usually take place at a much lower temperature and makes use of a soft alloy such as tin-lead as opposed to hard soldering which takes place at much higher temperatures and uses stronger alloys (brass/silver).
Soft Soldering
Soft soldering is a process used to attach smaller components to PCBs. These components are usually prone to break down under higher temperatures due to their low-liquefying temperature. A filler metal, usually a tin-lead alloy is used. A gas torch is used to heat the solder, causing it to break down and bind the components to the board.
Hard Soldering
Hard soldering is a process that uses a solid solder joint to join two metal elements together. At higher temperatures the holes of the components become unlocked and solder spreads through them. Hard soldering is subdivided into two processes:
- Silver Soldering: Silver soldering uses a silver alloy as a space-filler metal. This method is usually employed in the maintenance of circuit boards and fabricating small components. Silver is used here due to its free-running individuality but for sole space filling a different flux is recommended.
- Braze Soldering: Braze soldering or “brazing” is a soldering technique used to connect terminals of base metals through a filler metal. The liquid filler metal runs through the bard and cools down to form a solid bond. A resulting much stronger joint is formed. The space-filler metal used here is brass.
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The Tools Required
For the soldering process, you will require a
- Soldering iron
- Soldering paste
- Solder flux
- Printed Circuit Board
The Process
We’ve briefly explained the manual process of PCB soldering step-by-step below:
- Prepare the soldering iron: You will first have to prepare your solder iron. First let your iron heat thoroughly, then coat the tip with solder (make sure you cover the entire tip). Once your tip is entirely coated, wipe it off with a wet sponge to remove any flux residue. Try to do this immediately before the flux has time to solidify. This is called “tinning” – a process that stops your solder iron tips from oxidizing by creating a protective layer between the air and iron.
- Prepare your PCB board: Next, you need to make sure you’re working with a clean surface. Clean away any dust or debris from the PCB, you can even wipe it down using an acetone cleaner.
- Place the components: While placing your components we recommend starting with the smaller sized ones and working your way up to the larger sized ones. Make sure the components go the right way around and secure them.
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- Apply heat: Next, you’ll be applying some heat to the joint. Start by adding a small amount of solder to the tip of the soldering iron (this will help heat pass from the iron to the board) then hold the iron tip so that it touches both the PCB board and the component lead. The solder applied earlier will touch both the lead and the board, heating them up. Hold the iron here until properly heated and then remove. (Be cautious so as not to overheat the area, if you notice any bubbling then remove and wait for it to cool down before you resume).
- Add solder paste: Once heated, add solder to the solder pad and lead. If heated correctly in the previous step the solder should flow freely and fill in the space, the flux should begin to bubble and liquefy. Add the solder until the joint is completely coated, then remove your iron from the area. Do not move or shake your board as the joint cools.
That’s pretty much it! Once cooled down, you can inspect your soldering job. You can trim the excess using side cutters. Then you’ll move on to the next components. Once all your components are successfully soldered, clean any extra flux from the surface of the board so you’re left with a clean, nicely soldered PCB.
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