Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 3rd Term
Week: 8
Age: 15 years
Duration: 45 minutes
Subject: Radio, TV & Electronics
Curriculum Theme: Trade
Previous Lesson: Soldering And Desoldering In Electric Circuits: Techniques And Safety.
Topic: SOLDERING AND DESOLDERING IN ELECTRONICS CIRCUITS
Subject Matter: Precautions, Types of solder, Correct technique

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define soldering and desoldering.
State at least three precautions to observe during soldering and desoldering.
Identify different types of solder.

Affective Domain:

Appreciate the importance of safety measures when working with electronic circuits.
Value the use of correct techniques for soldering and desoldering.

Psychomotor Domain:

Demonstrate the correct technique for soldering components onto a circuit board.
Demonstrate the correct technique for desoldering components from a circuit board.

Collaborate with peers when practicing soldering and desoldering techniques.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (JSS 1-3) / Senior Secondary Education Curriculum for Trade Subjects.
State Unified Scheme of Work for Radio, TV & Electronics (SSS 1).
Any standard Radio, TV & Electronics textbook for Senior Secondary Schools.

Instructional Materials

The teacher will teach this lesson with the aid of:

Soldering iron
Solder wire
Desolder wick / Solder sucker
Old circuit board with components
Safety glasses
Soldering stand

Rationale for the Lesson

This lesson helps pupils understand the basic processes of joining and removing electronic components, which is important for repairing and assembling electronic devices. Learning these skills prepares pupils for practical work in electronics and helps them maintain electronic gadgets they use daily.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of electronic components and their functions.

Lesson Content/Board Summary

SOLDERING AND DESOLDERING IN ELECTRONICS CIRCUITS

Definition of Soldering and Desoldering

Soldering is the process of joining two or more metal items together by melting and flowing a filler metal (solder) into the joint. The solder has a lower melting point than the adjacent metal parts.

Desoldering is the process of removing solder and components from a circuit board, often to replace faulty parts or correct errors.

Precautions During Soldering and Desoldering

It is important to observe the following precautions when soldering and desoldering:

Always wear safety glasses to protect eyes from splashes of molten solder or fumes.
Ensure good ventilation in the work area to avoid inhaling solder fumes.
Use a soldering iron stand to prevent burns and damage to the work surface.
Avoid touching the hot tip of the soldering iron.
Unplug the soldering iron when not in use or when leaving the workstation.
Work on a heat-resistant surface.
Wash hands thoroughly after handling solder, especially lead-based solder.

Types of Solder

Solder can be classified based on its composition:

Lead-based solder: Traditionally used, typically a tin-lead alloy (e.g., 60% tin, 40% lead). It has a lower melting point and flows well.
Lead-free solder: Environmentally friendly alternative, usually made of tin, copper, and silver alloys. It has a higher melting point and requires more heat.
Rosin-core solder: Contains a flux inside the solder wire, which cleans the metal surfaces during soldering, ensuring a good electrical connection.

Correct Soldering Technique

The following steps describe the correct soldering technique:

Clean the tip of the soldering iron and tin it with a small amount of solder.
Place the component lead through the hole in the circuit board.
Heat both the component lead and the copper pad on the circuit board simultaneously with the soldering iron tip for a few seconds.
Apply solder to the joint (not directly to the iron tip), allowing it to flow around the lead and pad.
Remove the solder and then the soldering iron once a shiny, cone-shaped joint is formed.
Allow the joint to cool naturally without moving the component.

Correct Desoldering Technique

The following steps describe the correct desoldering technique using a solder wick:

Place the desoldering wick over the solder joint to be removed.
Heat the desoldering wick with the soldering iron tip, pressing it onto the joint.
The molten solder will be absorbed by the wick.
Remove the soldering iron and the wick once the solder is absorbed.
Repeat if necessary until the component lead is free.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them if they have ever seen someone repair an electronic device, perhaps using a heated tool and some metal wire. The teacher then introduces the topic of soldering and desoldering.
Pupils’ Activity: Pupils respond to the questions and listen attentively to the introduction.
Learning Point: Pupils are engaged and introduced to the lesson topic.

Step 2: Definition of Soldering and Desoldering

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines soldering and desoldering, explaining their purposes in electronics. The teacher writes the definitions on the board.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the basic concepts of soldering and desoldering.

Step 3: Discussion of Precautions During Soldering and Desoldering

Time: 8 minutes
Teaching Skill: Safety Awareness/Discussion
Teacher’s Activity: The teacher discusses the various safety precautions that must be observed when performing soldering and desoldering, emphasizing the risks involved and how to mitigate them. The teacher lists these precautions on the board.
Pupils’ Activity: Pupils contribute to the discussion, ask questions about safety, and write down the precautions.
Learning Point: Pupils learn about the importance of safety and specific precautions.

Step 4: Explanation of Types of Solder

Time: 5 minutes
Teaching Skill: Categorization/Explanation
Teacher’s Activity: The teacher explains the different types of solder, focusing on lead-based and lead-free solders and the function of rosin-core solder. The teacher writes the types on the board.
Pupils’ Activity: Pupils listen and note the different types and their characteristics.
Learning Point: Pupils can identify and differentiate between various types of solder.

Step 5: Demonstration of Correct Soldering Technique

Time: 8 minutes
Teaching Skill: Demonstration/Modeling
Teacher’s Activity: The teacher demonstrates the correct soldering technique using a soldering iron, solder wire, and an old circuit board, following the steps outlined in the board summary. The teacher explains each step clearly.
Pupils’ Activity: Pupils observe the demonstration carefully, paying attention to the teacher’s technique and safety practices.
Learning Point: Pupils visually learn the proper method for soldering.

Step 6: Demonstration of Correct Desoldering Technique

Time: 7 minutes
Teaching Skill: Demonstration/Modeling
Teacher’s Activity: The teacher demonstrates the correct desoldering technique using a desolder wick (or solder sucker) to remove a component from the old circuit board, explaining each step.
Pupils’ Activity: Pupils observe the desoldering demonstration, noting the tools and steps involved.
Learning Point: Pupils visually learn the proper method for desoldering.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define soldering and desoldering.
Mention three precautions to observe during soldering.
State two types of solder.
Briefly describe the steps for a correct soldering technique.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 0 minutes (integrated with evaluation)
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the importance of correct techniques and safety. The teacher assigns pupils to research common soldering faults and their causes.
Pupils’ Activity: Pupils listen to the summary and note the assignment.
Learning Point: Pupils reinforce their understanding and are given tasks for further learning.

Lesson Keywords

Soldering – The process of joining metal parts using a molten filler metal (solder).
Desoldering – The process of removing solder and components from a circuit board.
Solder – A metal alloy with a low melting point used to join other metals.
Soldering Iron – An electrical tool used to heat solder to its melting point.
Solder Wick – A braided copper wire used to absorb molten solder during desoldering.
Flux – A chemical cleaning agent that aids in soldering by preventing oxidation.

Differentiation

For pupils who grasp concepts quickly, the teacher can encourage them to assist peers during practical sessions or research advanced soldering techniques. For pupils needing more support, the teacher will provide closer supervision during demonstrations and offer simplified explanations.

Note for teachers using this lesson plan

Ensure all safety equipment is available and pupils understand its use before any practical demonstration. Provide clear, step-by-step instructions and allow pupils to observe closely. If practical sessions are planned for a subsequent lesson, ensure enough materials and supervision are in place.