PCB(Printed Circuit Board)

Presented

By

S.Muthumari

ContentPCBBread BoardThickness of copperTypes Manual printingPhoto resist methodScreen printing methodUsing software Etching processSchematic diagram layout

Difference between PCB Layout and bread board connection

Bread boardADVANTAGES:

1. A QUICK CHECK FOR EASY AND COMPLEX CIRCUITS BOTH AND

VERIFIES CIRCUITS AT INITIAL STAGE.

2.REUSABLE.

3.NO SOLDERING REQUIRED.

4.CAN BE DEBUGGED EASILY.

5.CHEAP AND CONNECTIONS CAN BE CHANGED.

• DISADVANTAGES: 1. UNRELIABLE.

2. DELICATE.

3.TEMPORARY.

4.HEAVIER.

PCB A printed circuit board, or PCB, is used to mechanically support and

electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a nonconductive substrate. It is also referred to as printed wiring board(PWB) or etched wiring board. Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices.

Components used for PCB Copper cladded sheets

There are subdivided into, paper phinally glass epoxy

Advantages of PCB Inexpensive/cheaper

High volume production

Automated soldering is possible

Highly reliable

Hold the component easily

Thickness Of Copper

0.8mm(used for low power component( e.g.: slim phone,smd,multimeter)

1.6mm(used in commercial purpose)

3.2mm(power electronics side

Examples: MOSFET, Diode.

Types Manual printing.

Photo resist method.

Screen printing

Using software

Manual printing• Get the required size copper board.

• Draw the layout on the board using permanent marker or nail police.

• Etching process.

• Fix the component on the board

• Check the output

Photo-resist method

The main properties characterizing the photo resist types are:

Photo resists are classified into two groups: positive resists and negative

resists

positive resist method

negative resist method

Positive resist method

A positive resist is a type of photo resist in which the

portion of the photo resist that is exposed to light becomes soluble to the

photo resist developer. The portion of the photo resist that is unexposed

remains insoluble to the photo resist developer.

• Negative resist method

A negative resist is a type of photo resist in which the

portion of the photo resist that is exposed to light becomes insoluble to the

photo resist developer. The unexposed portion of the photo resist is

dissolved by the photo resist developer.

Characteristic Positive Negative

Adhesion to Silicon Fair Excellent

Relative Cost Less

Expensive Developer Base Aqueous

Organic Minimum Feature 0.5 μm and below

± 2 μ step Coverage Better

Lower

Wet Chemical Resistance Fair Excellent 

Exposing Sun light (minimum 3 mins)

Mercury lamp(8 mins)

Tube light (15mins)

Screen printing • Screen printing printed circuit boards is typically

performed in a clean, dust free room using semi-automatic

or fully-automatic screen printing presses. The most

common PCB panel size is 53 x 72 cm, with the printing

area around 50 x 70 cm. The printed panel may contain

many PCB panels that are printed at once, and will

eventually be separated.

1.4 Soldering Methods1.4.1. Hand soldering:

It is the oldest method of soldering, it is still popular method in certain kinds of applications: Development of prototype boards

Low volume production Soldering of extremely temperature sensitive components Solder reflow of fine pitch components using hot bar Rework or repair of machine soldered boards The main disadvantages are operator training, speed, and consistent

quality. 

1.4.2 Machine Soldering:Two prominently used machine soldering types are:A. Wave Soldering

Primarily used for soldering through-hole components on to PCBs.

B. Reflow Soldering.

Used for soldering SMD components on to PCBs. Reflow soldering of SM components have the following advantages over manual soldering:

• Mass soldering• Consistency in manufacture through precise control of process

parameters.• flexible for small production runs as well.

Etching processThe following are used for etching

HCL Cupric chloride Ferric chloride Ammonium chloride.

Fecl3+cu->cucl3+fe

Method of etchingHand drought method

Splash method

Spray method

Solder mask

Solder mask is used to prevent oxidization solder able solder mask Un solder able solder mask

Why masking? a. Protect tracks from environmental effects suc as corrosion

b. avoid between two electrical components during soldering, testing.

c. Protects PCB material from environmental effects.

Plating To avoid corrosion

brightness easy solder able deposit harder than ordinary plating corrosion resistance non-staining non-toxic

Software • Eagle 6.2.0 version (Easily Applicable Graphically Layout Editor)

• PCB Wizard

• Pad2pad

• Spark PCB

Schematic Diagram

Layout

SMD Component Layout

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