Page 60 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Fig 10

The frequency can be determined by the formula

where frequency is in hertz and time in seconds.
Example
Time = Div x time base setting

= 5 x 0.2 ms
= 1 ms

Frequency = 1 kHz.

Printed circuit boards (PCB)

Objectives: At the end of this lesson you shall be able to
• state the types of etchants used for etching and preparation of etchant solution
• state the reasons for agitating the etchant solution while etching
• list the important points while drilling holes on PCBs
• list the advantages of marking component positions on PCBs.

Introduction

Printed circuit board in which the connecting wires are replaced by a thin conducting path called copper or silver
foil which is moulded in one side of the insulated board. The insulating board is generally made up of phonetic,
paper or fibre glass or epoxy.
The moulded conducting path generally known as tracks size depend on the power of the circuit. The width of
tracks are varied few millimeters to less than one millimeter depend on the circuit.

The thin tracks less than one millimeter made up with silver tracks where IC circuits and micro controller circuits
are to be made. Several process moulded to make PCB and it is explained below.
Etching

Once the required portions on the copper foil side of the laminate is painted/masked and dried, the next step is to
remove the copper present in the unmasked portions of the laminate. This process is known as etching.
Only after etching the unwanted areas of the copper foil, the metal side of the laminate gets the actual shape of
the circuit connection required.

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CITS : Power - Electrician & Wireman - Lesson 60-69