Soldering is the use of molten metal to make electrical connections. Solder is the metal or metallic alloy used when melted to join metallic surfaces. Soldering process is used in the electronics industry to bond components together, forming one of more electrical connections. Soldering serves two functions: mechanical support—holding components of an assembly together, and electrical support—forming required electrical connections within a circuit.
Soldering is essential in most electronic devices, even with the development of microchips. Soldering is mainly used in making PCBs, in plumbing, and in roofing. This lab consists of digital and interactive activities to learn more about soldering. In this activity students will get hands-on with soldering.
Course/SkillsBuild for Student Module: IBM SkillsBuild Lab: Soldering
Length of Class: 60-90 mins
Outcomes: What learners will be able to know, do, or value by the end of the lesson.
- Students will understand the purpose of soldering.
- Students will be able to identify the tools and materials used for soldering.
- Students will be able to explain the safety measures required during soldering.
- Students will execute appropriate soldering and de-soldering.
Workplace learning skills:
- Agility and cognitive flexibility
- Analytical thinking
Required Learning Materials/Resources (per students)
- Soldering iron
- AA battery
- Solder wire
- Flush cutter
- PCB board
- Ticky Tack
- Soldering iron stand
- Safety glasses
Learning Environment Needs
This activity needs to be done in a well-ventilated area.
Prework for Educators
Instructors should review and become familiar with these materials prior to teaching:
It is recommended that teachers practice soldering before teaching this lesson to students.
Part 1: Intro to Soldering and Circuit Boards
Check for prior knowledge of soldering and circuit boards with the KWHLAQ worksheet. Ask questions like “What is soldering?” and “What is a circuit board?”
Show the video: How do Circuit Boards Work? Help students understand a PCB board’s function.
Ask some questions from the video like “What are PCBs?” and summarize what a circuit board is. Then check for understanding of the connection between circuit boards and soldering.
Review and demonstrate the tools needed for soldering:
- Soldering Iron: A soldering iron is a hand tool that plugs into a standard 120v AC outlet and heats up in order to melt solder around electrical connections. This is one of the most important tools used in soldering and it can come in a few variations such as pen or gun form. Be very cautious when using any type of soldering iron because it can heat up to 896′ F which is extremely hot.
- Soldering Iron Stand: This stand helps prevent the hot iron tip from coming in contact with flammable materials or causing accidental injury to your hand. Most soldering stations come with this built in and also include a sponge or brass sponge for cleaning the tip.
- Cutters: Used to trim the leads from components once soldered
- Solder Wire: The wire used to solder. In general, lead-free (Pb-free) solder should be used.
- Ticky Tack: Can be used to hold down the PCB while soldering
- Safety Glasses: These must be worn at all times when soldering.
Part 2: Soldering Safety
Before starting hands-on soldering review soldering safety. You could start out with a discussion or show this optional video How to Solder Safely Video (3:04)
You can also use this optional Soldering Safety Worksheet as an assessment and way to check for understanding before moving on to the hands-on activity portion of the lab.
Check for safety knowledge. Review these important safety points:
- Be careful of the hot soldering iron. Do not do anything but solder while holding the soldering iron. As soon as you’re done making the joint, return the iron to the stand.
- Never touch your face when soldering. Always wash your hands immediately after soldering.
- Only hold the soldering iron by the handle, ensure that fingers are kept well away from the hot end.
- Students must wear safety goggles. This prevents accidents, not only with the soldering iron itself, but in the rare situation of solder splashing.
- The soldering iron should always be returned to the stand when not in use. This prevents accidental burns. Also note that some parts of the stand can get hot.
- If a wide-open space isn’t available, ensure that the work area is well ventilated. A fume extractor can also be used to reduce the smoke. While only small amounts of smoke are produced, encourage the participants to not breath it in.
- When trimming the leads of components, place one hand over the leads in case they fly off.
- When feeding in solder to the joint, ensure that there is a good amount (about 6cm) of solder straightened out so that fingers don’t need to get too close to the tip of the soldering iron.
Part 3: Hands-On Soldering Activity
Start by demonstrating the preparation of the soldering iron. A clean iron makes all the difference when soldering. Ensure that the soldering iron tip is clean and tinned. Tinning the tip means applying some solder directly to the tip of the iron and then wiping it away on a damp sponge (or brass wool) that’s usually built into the soldering iron stand. A thin layer of solder is left on the tip, leaving a shiny silver appearance. You should tin the tip of your iron before and after each soldering session to extend its life.
It’s also important to add that when the soldering iron is not in use, turn it off. This prevents soot buildup on the tip of the iron that can make it difficult to use/clean. If you are having problems tinning the tip because it has become blackened, a tip cleaner/tinner can be used to rejuvenate it.
Students can put the wire through the plated hole and secure the parts. If they move while soldering, the joint will not work. They can be secured using the sticky-tack, or with clips. Bending the legs of the part out after putting it through the holes is a good way to prevent it from moving.
Now students can make a solder joint. Three points to keep in mind:
- Solder moves from cold to hot surfaces
- Solder moves most easily on “wetted” surfaces, that already have some solder on them. Flux improves wetting. The tip of the iron should be shiny, and the solder should move onto the iron (not ball up on the solder wire).
- The “sweet spot” of the iron is on the side of the tip, 1-2mm up from the end of the tip. We should use this surface to contact the parts being soldered together.
1. Tin the soldering iron tip by melting solder on it, then wiping off the extra solder onto the sponge. This gives the solder tip good wetting.
2. Touch the side of the soldering iron to the joint so that it contacts both the wire and the plated hole. This is the “sweet spot.”
3. Apply the solder so that it touches the wire and the plated hole on the side opposite where the iron is touching; hold it there until the solder melts and flows to cover the plate and wire.
4. When solder has coated the plated hole and the wire, remove the solder wire from the joint.
5. Remove the soldering iron from the joint. If step 5 happens before step 4, the solder wire will solidify to the joint! If the joint isn’t good, repeat the above steps.
The shape of the joint should look like this:
Here are some examples of how the joint should look and common problems:
Demonstrate making a solder joint:
- Use wire strippers to remove insulation from a wire
- Fold the wire and put it through two holes in the prototype board; the wire needs to stick out through the side with plating on the holes
- Make the solder joint as shown above.
- Trim the wires using the flush-cutters; cut the wire’s just a bit above the solder (avoid cutting into the solder joint as it can break the joint)
Have the student sit 1-2 people per soldering station and try making solder joints. Between two students, they shouldn’t need to use more than 9cm^2 of prototype board. When the students are finished, they should re-tin the tip of their iron and turn it off.
Tip: A common mistake is to apply solder to the tip of the iron and then to ‘wipe’ the solder onto the board. This won’t work, always apply solder to the pad and lead being soldered while the soldering iron is heating the pad and lead.
Part 4: Career Focus (20 mins)
The biggest source of soldering jobs is in the electronics industry. Virtually any product that gets plugged in or runs on batteries contains a circuit board. The manufacturing of circuit boards requires a multitude of different solders and the work must be precise. Professional certification is recommended for Soldering Trainers but is not required for Soldering Technicians. Soldering may be stipulated as a secondary skill within a job’s skill requirements details. Students can read more about Soldering Technicians here: What is a Soldering Technician (optional)
Students can also view this video: Skilled Assembly Jobs in Electronics Manufacturing (3:11) to learn more about careers with soldering.
25 Makerspace projects for kids: This site includes a compiled list of some favorite projects that are great for makerspaces. Learn how to make simple circuit out of a pizza box, create a circuit using paper, and many more.
Additional Resources/ Deeper Learning
What Is Flux? | Soldering Video: (2:44)
This video explains how Flux is a very important part of soldering. Flux is necessary to reduce the oxides that tend to form whenever you have hot metals in contact with the air.
Beginner’s Guide on Soldering | Instructables: Beginner’s guide on soldering. Learn how to solder with reasonable proficiency.
How Computers Work – You Tube Series I Code.org – In this YouTube series from Code.org, you’ll learn about about the components of a computer and and how they work.
Soldering Basics Lesson Plan– This is a general lesson plan guide to soldering that can be used as the basis to solder a variety of simple electronics kits.
Introduction to Soldering Lesson Plan – In this soldering activity students will solder wires to plated through-hole prototype boards and desolder joints using a solder sucker.
Based on application, how I will I know learners have met intended outcome?
— KWHLAQ worksheet
— Teacher may wish to create a rubric for soldering practice
—Soldering Safety Review Worksheet
How will I bring lesson to an effective closing?
— Check for understanding and answer any subsequent questions
— Emphasize key information
— Ask the question “What information did you learn that you think you will find important 3 years from now?”
— Remind students that there are more relevant courses on SkillsBuild for Students to continue their learning
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