(Printed Circuit Board) Presented By S.Muthumari PCB (Printed Circuit Board) Presented By S.Muthumari

Content PCB Bread Board Thickness of copper Types Manual printing Photo resist method Screen printing method Using software Etching process Schematic diagram layout

Difference between PCB Layout and bread board connection

Bread board ADVANTAGES: DISADVANTAGES: 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 There are subdivided into, 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 Methods 1.4.1. 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 process Fecl3+cu->cucl3+fe The following are used for etching HCL Cupric chloride Ferric chloride Ammonium chloride. Fecl3+cu->cucl3+fe

Method of etching Hand 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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