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Learn How to Solder

pcb-soldering.jpeg

In this lesson you’ll learn how to use a soldering iron to solder electronic components to a printed circuit board. The secret to learning to solder is patience and practice. You may not instantly pick up the new skill, but if you keep your cool and keep at it, you’ll be a soldering whiz in no time.

At the heart of any soldering project are electronic components like resistors, capacitors, LEDs, and integrated circuits, and the surface they are soldered to — a printed circuit board more commonly called a PCB. A PCB is a specially designed structure that solves the maze-like tangle of connections required for a circuit by using conductive and non-conductive material.

On the surface of a PCB, you’ll notice that there are drilled holes through the board with corresponding rings of copper on the opposite side. These are used with through-hole components and you can quickly identify them as they have long metal leads (often called legs). These leads are inserted through the board and soldered on the other side.

Surface-Mount components are designed to be soldered directly atop a PCB. They have leads, but they are much shorter as they don’t need to reach as far.

Through-Hole ComponentSurface Mount
Photograph of a 100K resistor on a hot-pink background.BatteryClip_patchr.jpg
Small components with long leads meant to thread through the PCB.Tiny to miniscule components with legs that are meant to sit on top of the PCB on pads.

[illo: PCB with pads, holes, and traces shown]

As you probably already know, different materials have different melting points. Electric components and PCBs can tolerate high temperatures and won’t melt easily. Solder however isn’t as tolerant and will melt at a much lower temperature. Soldering takes advantage of this to act a bit like the hot glue of your circuit.

By heating up a component lead and a PCB pad, you can melt solder between them. When the heat is removed, the solder will quickly cool and create a bond between them. You’ll often hear this connection called a solder joint, and when it’s done properly will look a bit like a shiny volcano.

Now that you know your way around a PCB and a bit about the two main types of components, it’s time to get you iron out and start practicing soldering. You’ll need the following parts and tools.

PARTS & TOOLS#

  • Soldering irons
    • Basic Soldering Irons
    • Adjustable 60W Pen-Style Soldering Iron
    • Soldering Iron - 60W (Adjustable Temperature)
    • Deluxe Soldering Irons
    • Digital Genuine Hakko FX-888D
    • Weller WE1010 Soldering Station
  • Solder
    • Solder Wire - RoHS Lead Free 0.5mm/.02" diameter - 50g
    • Solder Lead Free - 100-gram Spool
  • Soldering iron tip cleaners
    • Hakko Brass Sponge Solder Tip Cleaner
    • Natural Sponge
  • Printed circuit board
    • Components
  • A well ventilated room
  • Safety Glasses
  • Anti-Fog Protective Glasses

STEP 1#

Workspace Prep

pcb-workspace.jpeg

Successful soldering starts with a clean workspace and proper safety. Find a spot on a sturdy table near a power outlet and without much clutter and a pair of safety glasses to protect your eyes.

It will take a few minutes for your iron to get up to temperature, but while you wait you can practice holding your iron and getting your PCB and components ready for soldering.

STEP 2#

Get a Grip

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Soldering is a two-hand activity. With your dominant hand, grasp the soldering iron by its non-metal handle. With your other hand, hold the solder and stretch out a bit of it so you have some slack. Take a minute and practice time and get comfortable.

WARNING

Never touch or grab your soldering iron by the metal tip — this habit will keep you from getting a serious burn — and when working in groups, you never know how long the iron has been plugged in or how long it’s had to cool.

STEP 3#

Temperature Test

Once you plug in your iron, it will take a few minutes to get hot enough. Fancy soldering irons come with temperature gauges, but they aren’t necessary. You’ll know when your iron is ready when you can easily melt a bit of solder on the tip of it.

Surprisingly, this is one of the few times you’ll actually want to apply solder directly to your iron. Soldering is not painting.

NOTE

Never apply solder to your iron to spread onto a component — you won’t make a solid solid joint, but you will make a hot mess.

STEP 4#

Heat Those Leads Up

pcb-soldering-2.jpeg

To get started select a through-hole component and slot it into the holes of your PCB. Bend the leads of the component to help keep the component in place before you apply solder. This is more of an art than a science.

Place the side of your soldering iron’s tip so that it contacts the component lead and the adjacent solder pad on the PCB. Your goal is to heat these two metal parts up as much as possible. After a few seconds, touch the solder between the lead and the pad and feed the solder into the joint.

When enough solder has melted to cover the hole in the PCB, remove the iron. The remaining solder will quickly cool and create a conical shape that has a bit of a shimmer.

STEP 5#

Once you get the hang of soldering through-hole components, it’s time to heat your iron at try Surface-Mount Component soldering. The trick with surface mount work is really how you hold the component in place before you apply solder. In the case of the battery holder a small piece of tape can be used to hold the component in place.

First align the component with the solder pads. Then apply a bit of tape to hold it in place while you work. Place your iron on on of the pads and make sure it also touches the metal of the battery holder. After a few seconds, the metal should be hot enough to melt solder.


Now that you’ve learned to solder through-hole and surface-mount components, you’re ready to build more electronic circuits. Lesson #1 and learn how to build an LED badge.


Electronics Jargon#

Component Leads#

Metal wires built into a component that are used for soldering it to a PCB.

PCB (Printed Circuit Board)#

A common abbreviation for printed circuit board, a material typically made of fiberglass and copper that electronic components are soldered to to build circuits.

PCB Pad#

The exposed copper on a PCB where you can apply solder to to attach components. Pads in this lesson all surround drill holes through the PCB; however, as you learn more about PCB design, you’ll learn that pads also exist without drill holes — these are used for test points or for surface mount components.

Solder Joint#

The solder connection between a PCB pad and a component.

Surface Mount Components#

Electronic components that are placed on a PCB and soldered in place. They do not use drill holes to mount, but instead sit on exposed pads.

Through-Hole Component#

Electronic components with long metal leads designed to fit through drill holes in a PCB. These components are common in DIY electronics, but less so in consumer electronics where smaller surface mount components are used.