PCB-A Brief Introduction
of 18
-
Upload
richards-louis -
Category
Documents
-
view
221 -
download
0
Transcript of PCB-A Brief Introduction
-
8/8/2019 PCB-A Brief Introduction
1/18
EUPRAXIA 09
Welcome
to the PCBworkshop
Click to edit Master text stylesSecond level Third level
Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
2/18
SYNOPSIS
PCB cleaning
Ironing layout
Marking
Etching
Drilling
Tinning
Components-placing
Soldering
-
8/8/2019 PCB-A Brief Introduction
3/18
PCB CLEANING
The PCB is wiped with asoft cloth and thenscrubbed using sandpaperto remove the dustparticles.
Rinse the PCB and scrubonce more.
This abrasion will yield achemically and
mechanically activatedsurface that is ready forsubsequent processing.
Click to edit Master text stylesSecond level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
4/18
IRONING THE LAYOUT
The printout of thelayout is obtained fromthe EAGLE board file.
The sheet is alignedwith the PCB and isironed with uniformpressure for about 10-
15minutes.
Click to edit Master text stylesSecond level
Third level Fourth level
Fifth level
-
8/8/2019 PCB-A Brief Introduction
5/18
LAYOUT AFTER THEIRONING
After ironing, thepaper is carefullyremoved.
The PCB looks likethe image shown.
Click to edit Master text stylSecond level
Third level Fourth level
Fifth level
-
8/8/2019 PCB-A Brief Introduction
6/18
Dos and Donts
Donts:
Do not applyexcessive pressure
while ironing: itmight damage thecopper coating overthe PCB.
Handle the PCB withcare: copper ismetal, and ironing
makes it HOT- you
Dos :
The PCB should bemoderately moist
before ironing: thisensures that thetoner particlesadhere to the PCB.
The Iron box shouldbe set at moderateheat.
-
8/8/2019 PCB-A Brief Introduction
7/18
Dos and Donts
Dos.
Apply uniform pressureover the entire area.
If any part of the trackis not clearlyimpinged, use apermanent marker to
complete the track.
Donts:
Take care to avoid anyMisalignment of the
paper, else the Layoutwill get smudged.
-
8/8/2019 PCB-A Brief Introduction
8/18
ETCHING
A small hole is drilledat one corner of thePCB. A wire is
inserted and the PCBis lowered into atrough containing theEtching solution.
The PCB is shakenvigorously
Click to edit Master text stylesSecond level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
9/18
ETCHING
After a while, thecopper begins todissolve into thesolution.
The time for etchingdepends on theconcentration ofetching solution.
When etching iscomplete, the PCBlooks as shown.
Click to edit Master text stylesSecond level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
10/18
CAUTION !!
Do not leave the PCB in the etching solutionfor too long: the circuit track might begin to
dissolve causing discontinuities in thecircuit.
-
8/8/2019 PCB-A Brief Introduction
11/18
DRILLING
The through-holes forvarious circuitcomponents are
drilled using thehand-driller or therotary machine.
(Hand drillers are
much moreeconomical andeasily available.)
Click to edit Master text styles
Second level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
12/18
DRILLING .
Drill-bits of variousdiameters are usedto drill holes for
various circuitcomponents.
A few are mentioned:
Resistors:0.6-0.8mm
Capacitors: 0.6mm
Diodes: 1.2 mm
Click to edit Master text stylesSecond level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
13/18
TINNING
The track on the PCBis greased
completely with flux.
The track is tinned
using the solderingrod as shown.
Click to edit Master text stylesSecond level Third level Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
14/18
WHY TINNING ?ick to edit Master text stylescond levelThird level Fourth level
Fifth level
Although the copper track on the PCB issufficient to conduct electricity, copper is
prone to oxidation on exposure to air,which reduces its conductivity with time.
Hence, tinning is essential in order tomaintain conductivity of the track.
-
8/8/2019 PCB-A Brief Introduction
15/18
CAUTION
Extra care should be taken while tinning thinand closely spaced tracks, so as to avoid anyshort-circuiting by mistake.
It is advised that tinning is not done near thecomponent-through-holes: the soldering ofthe component leads (later) will suffice.
(If you tin the through-holes, you are liable
to blocking the holes.)
-
8/8/2019 PCB-A Brief Introduction
16/18
COMPONENTS-PLACING
A printout of the mirror-image of the circuit isobtained from the EAGLEfile.
Based on this circuit,components arepositioned on the PCB.
The Leads of the
components shouldemerge on the sidewhere tinning has beendone.
Click to edit Master text stylesSecond level Third level
Fourth level Fifth level
-
8/8/2019 PCB-A Brief Introduction
17/18
SOLDERING
After the components havebeen inserted in theirrespective positions, turn thePCB over, and the leads ofthe components are soldered.
While soldering ICs, a verysmall quantity of the solder ismelted onto the soldering rodand is then targeted at thelead from a distance: thisensures that the quantity andtime of heat transfer to the
leads (and hence to the IC) isminimal: thereby minimizesthe risk of damaging of the ICdue to undesirable heat.
Click to edit Master text stylesSecond level Third level Fourth level
Fifth level
-
8/8/2019 PCB-A Brief Introduction
18/18
THANK YOU
