cprs module 3 - basic electronics

8/13/2019 CPRS Module 3 - Basic Electronics

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Module 3 - Basic Electronics
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Topic outline1 Introduction to soldering

2 What is Circuit Board

3 How to solder
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Lesson 1: Introduction to soldering
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Session Objectives

At the end of this session, you will be ableto:

Know what soldering is

Understand the safety precautions on

soldering Learn how to prepare the soldering iron


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Introduction

In this session, you will learn and

understand the importance and use of a

soldering iron for repairing cellular phones.


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What is Soldering?

Soldering is the process of using a metal

alloy with a low melting temperature

(solder) to fuse the electrical contacts of a

component to the pads of a circuit board.

NOTE:

Proper solderingmaximizes the strength

and conductivity of the connection; and

Poor solderingcan result in weakconnections, higher resistance that causes

heat build-up at the connection, and

possible failure of the component.


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Hot air Gun and Soldering Iron Temperature Setting

Hot air temperature tends to be variable

when working on any SMD components.

Various Cellular Phones Products use

different kinds of solders.

The amount of temperature on Hot Air

Gun's common setting is between 250-350

degrees Celsius while Soldering Iron is

between 200 - 280 degrees Celsius.


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Tips for soldering surface mount chip component

Cellular phone components need proper techniques of repairing. There are guidelines to keepin mind.

Chip ResistorsThe component body of chip resistors is made out of alumna; an extremely hard, white colored

material. The resistive material is normally located on the top. Chip resistors are usually mountedwith the resistive element facing upwards to help dissipate heat.

Ceramic CapacitorsThese components are constructed from several layers of ceramic with internal metalized

layers. Because metal heats up much faster than ceramic, ceramic capacitors need to be heatedslowly to avoid internal separations between the ceramic and the metal layers.

NOTE: Avoid rapid heating of ceramic chip capacitors during soldering operations.

Plastic BodyAnother style of chip component has a molded plastic body that protects the internal circuitry. There

are a number of different types of components that share this type of exterior package. The terminationstyles for plastic chip component packages vary considerably.

MELF - Metal Electrode Face cylindrical components

These may be capacitors, resistors, and diodes. It can be hard to tell them apart - since there is nouniversal coloring or component designators printed on the component bodies.


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Safety Precautions

Before proceeding to soldering, these are some safety precautions that you need to know:

I Never touch the tip of the soldering iron.It will give a nasty burn since it is very hot at about 400 Degree Celsius.

II Avoid touching the mains flex with the tip of the iron.Ordinary plastic flex could easily melt once touched by a hot iron and this will causeserious risk of burns and electric shock.

IIIKeep the soldering iron to its stand when not in use.Never put it down on your workbench, even for a moment!

IVWork in a well-ventilated area.The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoidbreathing it by keeping you head to the side of, not above, your work.

V Always wash your hands after using a solder.A Solder contains lead which is a poisonous metal.


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Lesson 2:What is Circuit Board
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Session Objectives


Know what a circuit board is

Identify the different components on the

Printed Circuit Board. Understand the diagrams of a Printed

Circuit Board

Learn the different circuit symbols


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Introduction

In this session, you will learn the

function of a Printed Circuit Board (PCB)

and identify the components within the

PCB.


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Printed Circuit Board (PCB)

A printed circuit board is one the main

components of a cellular phone. It is

considered to be the brain area of the

cellular phone and it runs the whole system.

A printed circuit board has to be very sturdyto be able to support its components.

A printed circuit board is used to

connect the electric components with the

use of conductive pathways and signaltraces through the use of electricity.


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Printed Circuit Board (PCB) Components

A printed circuit board consists of several components that work together to ensure the

proper functioning of the cellular phone.

COMPONENT PHOTO FUNCTION

Resistors Used to limit the flow of current. It has no polarity and is

checked by continuity testing (analog or digital typetester). (color; black and shiny, blue or violet)

Inductor Used together with capacitors as current filters. It has nopolarity and is checked by continuity testing (analog ordigital type tester). (color; gray or black but not shiny)


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Fuse Used to protect the unit from overload. It has no polarityand is checked by continuity testing (analog or digital typetester). (color; black or white with "K")

Diode acts as rectifier. It has polarity and is checked by one-sided

continuity testing. (color; black with stripe at one end)


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Capacitor Used as voltage filters and can store small amount ofelectricity. It has polarity and is checked by one-sidedcontinuity testing. (color; yellow or black with clearmarkings at the back with stripe on one side for polarized

capacitors and brown for non-polarized capacitors)

Transistor Used to amplify voltages. (color; black, it has 3, 5, or 6 pins)


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Light Emitting Diode(LED)

Used to illuminate the LCD and keypads. Commonlyknown as Backlights. Lights on when checking continuity.

Speaker Converts electrical signals into audible sound. Has cracking

sound when testing continuity.


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Microphone converts audible sound into electrical signals. Checkedusing one-sided continuity test.

Integrated Circuit (IC) performs multi-task function.

Types of IC Packaging:

a. Pin type- uses legs made of pins and can be Single In-Line Package (SIP) or Dual In-Line Package(DIP)

b. BGA (Ball Grid Array)- uses legs made of solder ball.


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Diagrams

Diagram is also known as electronic schematic. It is a graphical representation ofelectrical circuit. It shows the flow of connections between the devices using circuitsymbols, including the power and signal connections.

Types of Diagram

Block Diagram

Block diagrams are used to understand (and design) complete circuits by breaking themdown into smaller sections or blocks. Each block performs a particular function and theblock diagram shows how they are connected together. No attempt is made to show the

components used within a block, only the inputs and outputs are shown. This way oflooking at circuits is called the systems approach.


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Diagrams

Circuit DiagramCircuit diagrams show how electronic components are connected together. In a circuit

diagram, each component is represented using circuit symbols.


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Diagrams

PCB DiagramPCB Diagram is a graphical representation on how the components are arranged into the

printed circuit board.


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Circuit Symbols

Wires and Connections

COMPONENT CIRCUIT SYMBOL FUNCTION

Wire To pass current very easily from one part of a circuit toanother.

Cell Supplies electrical energy. The larger terminal (on the left)is positive (+). A single cell is often called a battery, butstrictly a battery is two or more cells joined together.

Battery Supplies electrical energy. A battery is more than onecell. The larger terminal (on the left) is positive (+).

DC Supply Supplies electrical energy. DC = Direct Current, always

flowing in one direction.

AC Supply Supplies electrical energy. AC = Alternating Current,continually changing direction.


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Circuit Symbols

Wires and Connections


Wire To pass current very easily from one part of a circuit toanother.

Fuse A safety device which will 'blow' (melt) if the currentflowing through it exceeds a specified value.

Transformer Two coils of wire linked by an iron core. Transformersare used to step up (increase) and step down (decrease)AC voltages. Energy is transferred between the coils bythe magnetic field in the core. There is no electricalconnection between the coils.

Earth(Ground) A connection to earth. For many electronic circuits, thisis the 0V (zero volts) of the power supply, but for mainselectricity and some radio circuits it really means theearth. It is also known as ground.


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Switches


Push Switch (push-to-make)

A push switch allows current to flow only when thebutton is pressed. This is the switch used to operate adoorbell

Push-to-Break SwitchThis type of push switch is normally closed (on), it isopen (off ) only when the button is pressed.

On-Off Switch (SPST) SPST = Single Pole, Single Throw. An on-off switchallows current to flow only when it is in the closed (on)position.

2-way Switch (SPDT) SPDT = Single Pole, Double Throw. A 2-way changeoverswitch directs the flow of current to one of two routesaccording to its position. Some SPDT switches have acentral off position and are described as 'on-off-on'.

Circuit Symbols


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Switches


Dual On-Off Switch(DPST)

DPST = Double Pole, Single Throw. A dual on-off switchwhich is often used to switch mains electricity because itcan isolate both the live and neutral connections.

Reversing Switch(DPDT)

DPDT = Double Pole, Double Throw. This switch can bewired up as a reversing switch for a motor. Some DPDTswitches have a central off position.

Relay An electrically operated switch, for example a 9V batterycircuit connected to the coil can switch a 230V AC mainscircuit. NO = Normally Open, COM = Common, NC =Normally Closed.

Circuit Symbols


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Resistors


Resistor A resistor restricts the flow of current, for example tolimit the current passing through a LED. A resistor isused with a capacitor in a timing circuit.

Variable Resistor(Rheostat)

This type of variable resistor with 2 contacts (a rheostat)is usually used to control current. Examples include:adjusting lamp brightness, adjusting motor speed, andadjusting the rate of flow of charge into a capacitor in atiming circuit.

Variable Resistor(Potentiometer)

This type of variable resistor with 3 contacts (apotentiometer) is usually used to control voltage. It canbe used like this as a transducer converting position

(angle of the control spindle) to an electrical signal.

Variable Resistor(Preset)

This type of variable resistor (a preset) is operated with asmall screwdriver or similar tool. It is designed to be setwhen the circuit is made and then left without furtheradjustment. Presets are cheaper than normal variableresistors so they are often used in projects to reduce thecost.

Circuit Symbols


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Capacitors


Capacitor A capacitor stores electric charge. A capacitor is usedwith a resistor in a timing circuit. It can also be used as afilter, to block DC signals but pass AC signals.

Capacitor, polarised A capacitor stores electric charge. This type must beconnected the correct way round. A capacitor is used witha resistor in a timing circuit. It can also be used as a filter,to block DC signals but pass AC signals.

Variable Capacitor

This type of variable resistor with 3 contacts (apotentiometer) is usually used to control voltage. It canbe used like this as a transducer converting position

(angle of the control spindle) to an electrical signal.

Trimmer Capacitor This type of variable capacitor (a trimmer) is operatedwith a small screwdriver or similar tool. It is designed tobe set when the circuit is made and then left withoutfurther adjustment.

Circuit Symbols


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Transistors


Transistor NPN A transistor amplifies current. It can be used with othercomponents to make an amplifier or switching circuit.

Transistor PNP A transistor amplifies current. It can be used with othercomponents to make an amplifier or switching circuit.

Circuit Symbols


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Audio and Radio Devices


Microphone A transducer which converts sound to electrical energy.

Earphone A transducer which converts electrical energy to sound.

Loudspeaker

A transducer which converts electrical energy to sound.

Circuit Symbols


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Audio and Radio Devices


Piezo Transducer A transducer which converts electrical energy to sound.

Amplifier (generalsymbol)

An amplifier circuit with one input.It is a block diagramsymbol because it represents a circuit rather than just onecomponent.

Aerial (Antenna) A device which is designed to receive or transmit radiosignals. It is also known as an antenna.

Circuit Symbols


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Circuit Symbols

Output Devices


Lamp (lighting) A transducer which converts electrical energy to light.This symbol is used for a lamp providing illumination,for example a car headlamp or torch bulb.

Lamp (indicator) A transducer which converts electrical energy to light.This symbol is used for a lamp which is an indicator, forexample a warning light on a car dashboard.

Heater A transducer which converts electrical energy to heat.

Motor A transducer which converts electrical energy to kineticenergy (motion).


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Circuit Symbols

Output Devices


Bell A transducer which converts electrical energy to sound.

Buzzer A transducer which converts electrical energy to sound.

Inductor(Coil, Solenoid) A coil of wire which creates a magnetic field when

current passes through it. It may have an iron core insidethe coil. It can be used as a transducer convertingelectrical energy to mechanical energy by pulling onsomething.


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Lesson 3: How to solder
http://e-tesda.gov.ph/CP_Repair/M2_L1.htmlhttp://e-tesda.gov.ph/mod/resource/view.php?id=329http://e-tesda.gov.ph/mod/resource/view.php?id=329http://e-tesda.gov.ph/mod/resource/view.php?id=329http://e-tesda.gov.ph/CP_Repair/M2_L1.htmlhttp://e-tesda.gov.ph/CP_Repair/M2_L1.htmlhttp://e-tesda.gov.ph/course/view.php?id=61http://e-tesda.gov.ph/course/view.php?id=61http://e-tesda.gov.ph/course/view.php?id=61http://e-tesda.gov.ph/course/view.php?id=61http://e-tesda.gov.ph/course/view.php?id=61


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Session Objectives


Know the proper techniques ofsoldering

Learn the safety precautions of soldering Understand what a circuit board is and

its components

Learn the circuit symbols


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Introduction

In this session, you will learn,

understand and perform the basic steps for

soldering different internal components of a

cellular phone.


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How to solder?

Basic Procedure on How to Solder

Note:Please keep in mind safety precautions.

Step 1: Clean the surface of the PCBA clean surface is very important for a strong,

low resistance solder joint.

Step 2: Component PlacementIn general itis best to start with the smallest and flattestcomponents (resistors, ICs, signal diodes, etc.)and then work up to the larger components(capacitors, power transistors, transformers)after the small parts are done.

Step 3: Apply HeatApply a very small amount of solder to the tipof the iron. This helps conduct the heat to thecomponent and board, but it is not the solderthat will make up the joint.


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How to solder?

Step 4: Apply Solder To The Joint

Once the component lead and solder pad have

heated up, you are ready to apply solder. Touch

the tip of the strand of solder to the component

lead and solder pad, but not the tip of the iron. If

everything is hot enough, the solder should flow

freely around the lead and pad. You will see the

flux melt liquify as well, bubble around the joint

(this is part of its cleaning action), flow out and

release smoke. Continue to add solder to the joint

until the pad is completely coated and the solder

forms a small mound with slightly concave sides.If it starts to ball up, you have used too much

solder or the pad on the board is not hot enough.

Step 5: Inspect The Joint and Cleanup

Once the joint is made, you should inspect it.

Check for shorts with adjacent pads or poor

flow. If the joint checks out, move on to the next.


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Basic De-soldering Procedure


A. Using a de-soldering pump (solder sucker)

Step 1:In setting up the pump, you need to push theSpring-loaded plunger down until it locks.

Step 2:Apply both the pump nozzle and the tip of yourSoldering iron to the joint.

Step 3:

Wait a second or two for the solder to melt.

Step 4:Then press the button on the pump to release thePlunger and suck the molten solder into the tool.


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Step 5:Repeat if necessary to remove as much solder aspossible.

Step 6:The pump will need emptying occasionally byunscrewing the nozzle.


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B. Using solder remover wick (copperbraid)

Step 1:

Apply both the end of the wick and the tipof your soldering iron to the joint.

Step 2:As the solder melts, most of it will flow onto thewick, away from the joint.

Step 3:Remove the wick first, then the soldering iron.

Step 4:Cut off and discard the end of the wick coatedwith solder.


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Soldering circuit board

Soldering circuit board components

1. IC HolderPlace the IC holder into the circuit board, so that the leads on the bottom

extend all the way through the holes in the board. Do not attach the IC to theholder yet. Turn the circuit board over so that the bottom is facing up, and heatyour soldering iron. Then solder each one of its lead. Use enough solder, thiswill prevent the solder to pull back from the board. After soldering all its lead,let it cool for a second.

2. ResistorsSoldering a resistor is not difficult. You just need to solder the two ends of

its lead to the board.


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Soldering circuit board

Soldering circuit board components

3. CapacitorPlace your capacitor lead to the circuit board. Bend the leads down to hold

the capacitor in place as you are soldering. Make sure the capacitor is as tight tothe board as possible. Touch the soldering iron to the joint it is sitting on. Andwait for a few seconds to let it cool.

4. InductorCenter the electronic component on the circuit board mounting pads. For

thru-hole components, feed the leads through the holes and bend the end of thelead over to hold it in place. Apply the solder to the lead. Do not move thecomponent or board until the solder connection cools for a few seconds.

cprs module 3 - basic electronics

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