Digital technologies/Soldering/Soldering- Beginner

What is Soldering?

Soldering is a process often used when working with electronics. It consists of melting one metal to connect two or more metal pieces. This connection not only creates an electrical connection, but it also secures a component in place.

We will be going over two different situations where soldering is used. The first being when soldering two different wires together and the second is when soldering a component to a perfboard or a PCB. A perfboard is a rigid board which has a grid of holes drilled into it. Each hole is surrounded by a copper pad onto which you can adhere solder. A PCB is a printed circuit board. They are similar to perfboards except that the components are connected using a conductive material built into the board.

Safety When Soldering

• When Soldering be sure to wet the sponge being used inorder to avoid burning it or ruining the tip of the iron
• Don’t leave the iron unsupervised and on
• Long exposure of the iron to the PCB and other electronic components will lead to them burning
• Don’t touch the iron
• Allow the solder and board to cool before handling

Types of Soldering

Through-hole-technology (THT)

• Through-hole-technology (THT) soldering means to solder components that have leads that will go through holes inside a protoboard or PCB.

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Surface mount device (SMD)

• Surface mount D soldering is when you will solder a component to the surface of a PCB. This type of soldering is typically used for smaller components and chips.

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Equipment and Materials

Types of boards

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Breadboards

Breadboards are used to build temporary circuits, they allow you to plug wires into the board and prototype circuits. The holes in a breadboard are typically connected in 2 ways: the (+) bars running down the board are connected vertically and the (-) are connected in a similar way. Each horizontal row of 5 dots is connected together. The part in the middle of the board is where the connection breaks.

Perfboards/Protoboards/DOT PCBs

A protoboard (also known as a perfboard or DOT PCB) is a PCB with pre-drilled holes that have square or circular copper pads. This board allows you to insert components into the holes to secure them and then the holes can be bridged together in order to connect them together and create a circuit.

PCBs

PCBs or Printed Circuit Boards are boards with connection pathways printed into the board. These boards are typically used in later stages of prototyping as there isn’t as much flexibility once the board is printed.

Tools

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• Soldering Iron

This is the iron used to manipulate the solder onto the board or circuit.

• Exhaust

Melting the solder often results in the production of fumes, these fumes can be toxic with extended exposure and so, soldering if often done in areas with good ventilation or in the presence of an exhaust system/fan.

• Solder

The material used to create joints is called solder, this is often sold in rolls of wire, there are different forms of solder that can vary in dimension. Always be sure to use lead free solder as the alternative is toxic. When purchasing solder for circuits, ensure that it isn’t plumbing solder.

• Flux

Flux is a material used to aid in soldering, this chemical removes the oxides on the surfaces of the metals being soldered and allows the solder to flow more uniformly on the joint and components.

• Tip Tinner

This chemical aids in tinning the tip of the soldering iron, tinning allows for the iron to take up the solder and allows the solder with far greater ease. This material is great if the iron won’t tin with regular solder or sponge.

• Tweezers and helping hands

Often with smaller components and in the presence of a more complicated circuit, using additional equipment like helping hands or tweezers can help the process. These essentially aid in manipulating the components and keeping them in a specific position.

• Wire Strippers

How to Solder

Set up

To begin soldering gather all of the equipment and components necessary. And begin by determining which connection needs to be made and how you plan on making it. Next we will set up the Iron and station; Ensure you have a working soldering iron and stand, gold wool sponge/wet sponge, solder, and (optional) flux and tip tinner. Turn on the iron and select the appropriate temperature for the iron:

• 700F (370C) for through hole components and wires
• 600F (315C) for surface mount components
• Higher temperatures can damage

How to Strip a Wire

Soldering two wires is the best way to practice soldering at the very beginning. There are two types of wire, either stranded or solid core. Both have a metal core wrapped in a plastic covering. To see the metal, you need to expose the core by removing the plastic. This can be done using wire strippers or wire cutters.

Wire Strippers:

When using wire strippers - place the wire in the slot written to be for the wire gauge you’re using and gently press around the tubing. You want to be sure to avoid cutting through the core of the wire since the goal is to expose the core. Once the perimeter of the covering has been cut through you will then remove it by slipping it off the core as seen below.

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Soldering Considerations

Polarity

When soldering different components be sure to consider their polarity! Often times certain components will only work when connected a certain way, and example of such a component is an LED. LEDs have a positive and negative end and the component will only work when connected in a certain manner.

Heat Sensitivity

Due to various reasons such as material or size, certain components are only able to handle certain levels of heat when being soldered. If exposed to too much heat for too long, they are likely to burn out and become unusable.

What to not do when Soldering

What is needed:

• Soldering iron
• Solder (preferably lead free)
• Components you want to solder
• Vent fan

Optional items:

• Solder wick
• De-soldering tool
• Soldering mat

Soldering two wires together

Soldering two wires is the best way to practice soldering at the very beginning. There are two types of wire, either stranded or solid core. Both have a metal core wrapped in a plastic covering. To see the metal, you need to expose the core by removing the plastic. There are special tools to do this called “wire strippers”. However, it is possible to do the same thing with scissors. A video on how to strip the wire is available here.

Procedure

1. Grab a few wires, strip 1 cm off each end and bend each end in a U shape.
2. Crimp the two wires together with a pair of pliers.
3. Hold the soldering iron like a pen. Heat the two wires for 1-2 seconds and then flow solder on the connection. The goal is to heat the connection not the solder. Once you see the solder flow evenly throughout the connection, remove the solder and soldering iron.
4. Allow the connection to cool, this usually takes 20-30 seconds. During this time, avoid moving the wires

Soldering to a board

1. Place the lead (metal stick coming from component) or wire through the hole in the perfboard or PCB.
2. Holding the soldering iron like a pen, heat the copper pad and lead with soldering iron until the solder begins to flow and forms a strong connection. Remove solder, and then the soldering iro. This process should take only a few seconds.
3. Allow for the connection to cool

Do's and Don'ts

Remember to:

1. Select the correct temperature
   • 700F (370C) for through hole components and wires
   • 600F (315C) for surface mount components
   • Higher temperatures can damage
2. Clean the tip between uses
   • It’s better to use the gold wool to clean the tips rather than the sponges
3. Wet the sponges before use
   • If the sponges are used dry, they burn and leave residue on the tips
4. Tin the tip when you are using the iron
   • Add a small amount of solder to the iron to keep it from oxidizing when you place it in the holder

Do not:

1. Do not leave the iron on. Leaving the iron can cause the tip to burn and will ruin in the iron over time
2. Do not file the tip. The tips have a protective coating the will get ruined
3. Don’t touch the mat or any plastics with the iron. A thin plastic film will form on the iron which will inhibit soldering. This includes heat shrink tubing.