PCB_MF

PCB DESIGNIn PCB design there are 3 st•Circuit design (available fro•Layout design (layout sketc•Art work design (output)

tagesom customers)ch)

TRANSLATING CIRCUIT DIAGRA•Read and understand the circu•Make a component list•Find out the IC equivalent andwhich you are going to do.Examples :Single sided PWB or•Decide the size of PCB

AM INTO LAYOUT:uit diagramd decide the type of board double sided PCB etc…

•Take a graph sheet and make a cthe physical dimensions make a sk•Place the pads on the intersectiothe size & pitch of the component•After placing pads draw the linesconnections. Take care of the sizedrawing it.

component layout is considering ketch.on of grid their pads depend on ts to be mounted. s where you want to make intere of the conductor thickness while

•If it is the double sided PCB it hasred/blue pencils to draw the cond“RED may be treated as componen•After making the layout check theschematic for circuit continuity an

s component side and solder useductor. nt side and blue as solder side’ e layout against the originalnd completeness.

Conductor width :They are based on two1.Current carrying capac2.Characteristic of impedinterconnecting lines

o factors ,citydance of power

General Example:If the Power conductor widthwidth for signal is 0.5mm & the2.0mmCurrent carrying capacity of 1can carry maximum 3 Amps.

h is 1.0mm, the conductore ground conductor width is1mm width, 35µm copper thick

For passing 3 Amps:1.Thickness & Width : 17.5µm &2.Thickness & width : 70µm & 0Standard thickness of copper fo

& 2.0mm0.5mm.oil is 17.5µm, 35µm & 70µm

4.2 BASIC LAWWgnd line > W supplWgnd line ≥ 2WW supply line ≥ 2

ly line > W signal lineW supply line2 W signal line

(a)Current carrying capa= 1mm = 3Amps35µm thick Cu foil

acity

(b)Resistance of 1mm = 5m

m = 35µm Cu FoilmΩ/cm length

4.3 Via hole :The interconnection between ccalled as Via hole. It is used in Dpcb’s.

component side & solder side isDouble sided and Multi layer

4.4 Annular ring : Annular ringthe diameter of hole. Iconnection and mechacomponent

is the area aroundIt gives electricalanical support to the

CONDUCTOR LENGTH It is based on the vorequirements .Ex: Resistance of 1mm Wthickness of a copper conohm/cm length. (For low

H: oltage drop (resistance)WIDTH & 35µm nductor is 5milliw current)

4.5 SCHEMATIC DIAGRAM RDESIGNATORS:Each component is identifiedreference designator such as: Cfor resistor, and Q for transistorThe number shows the differecomponents of the same type (The use of reference designatrecognizable identification for eschematic.

REFERENCE by an Alpha numericC1, R1,Q1 etc. (C for capacitor, Rr etc) ence between electrical(C1,C2,C3 etc) tors provides an easilyevery component part on the

Border Line (size):Border line can be addlayers and they can beto provide drill and cuthe manufacturing pro

:ded in mechanicale viewed in any layerut out guides duringocess.

Mounting holes : To fix the PCB’s withscrews & pins. Every “4’ we shouldsupport.

h the equipment usingd give mechanical

4.6 How to design a pcb wiwhere to run supply and gon the pcb

ithout the spikesground lines

Single sided PCB



Double sided PCB



UNUSED PCB AREA CAN BE LEFT UNECONNECTED TO GROUND

ETCHED AND

4.7 MICRO VIA Micro via is used as the inte layers in High Density Interc build-up (SBU) technology i boards.

erconnects betweenconnect ... Sequentialis used to fabricate HDI

4.8 DECOUPLING CAPAA capacitor which provides afor AC and to prevent commonof a circuit.Impedance : The total oppositWhen switching, the noise wovoltage lines and terminated toaid of the decoupling capacitor.

PACITOR low impedance path to ground coupling between the stages tion offered by the circuit. ould be removed from theo the ground line through the .





Decoupling CapacitoCeramic chip with short leadsPaper, polyster and other capThey have large series of inductElectrolytic Capacitors definite

Electrolytic Capacitors definitely avoidedor :s are preferablepacitors are not recommended.tance.tely avoided

4.9 TRANSMISSION The PCB techniquespecial microwave transmissionstrip line.MICRO STRIP: Micro strip is a flat conduconducting ground plane by anSTRIP LINE : Strip line is a flat conductorground planes

N LINEes can be used to create then line called Micro strip anductor separated from large insulating di-electric sandwiched between two