Page 131 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

MODULE 7 : Basic SMD & OCB Rework

LESSON 69 - 72 : Basic SMD (2, 3, 4 terminal components)

Objectives

At the end of this lesson you shall be able to:
• describe the wrong priciples of SMD and their types & advantages

Basic SMD (2, 3, 4 terminal components)

Introduction
Surface Mount Devices (SMDs) are used in a growing number of commercial and industrial products. Due to their
small size, prototype manufacturing, rework and repair can be difficult and are best performed using specialized
techniques specific to this technology. Learning these techniques will help you succeed when working with these
small components. The SMT technique opens advantages and new applications through miniaturizing of the
components and increasing of reliability.
Surface Mounted Devices (SMD) are active and passive electronic components without conventional connecting
wires.
Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are
mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is
called a surface-mount device (SMD).
Need of surface mount technology
SMDs have improved performance over through-hole component due to their smaller size, shorter internal leads,
and smaller board layouts. These factors reduce the circuit’s parasitic inductance and capacitance. SMDs can
also be more cost effective than traditional through - hole components due to the smaller board size, fewer board
layers, and fewer holes. SMDs can be challenging to solder, so it is best to learn general soldering skills on larger
components before attempting to work with SMDs.
1 Two terminal packages:
Diodes:
Diode is a two-terminal semiconductor device that will allow current to flow through it in only one direction. With
the proper voltage polarity across the device, it will act as a conductor. When the voltage polarity is reversed, the
device will act as a nonconductor, allowing no current to flow.
2 Three-Terminal Packages
Transistors
The transistor is a solid-state semiconductor device that can be used for amplification, switching, voltage
stabilization, signal modulation and many other functions. It allows a variable current, from an external source,
to flow between two of its terminals depending on the smaller voltage or current applied to a third terminal.
Transistors are made either as separate components or as part of an integrated circuit.

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