Pcb fabrication and types of fabrication and it's advantages. Application of pcb fabrication.It plays important role in electronics industry

1. Printed Circuit Board (PCB)
A printed circuit board (PCB) is a laminated sandwich structure of conductive and
insulating layers. PCBs have two complementary functions.
1. To affix electronic components in designated locations on the outer layers by means of
soldering.
2. To provide reliable electrical connections (and also reliable open circuits) between the
component's terminals in a controlled manner often referred to as PCB design.
PCBs mechanically support electronic components using conductive pads in the shape
designed to accept the component's terminals, and also electrically connect them using
traces, planes and other features etched from one or more sheet layers of
copper laminated onto and/or between sheet layers of a non-conductive substrate.
Through-hole technology
Surface-mount technology

2. Surface mount PCBs assembly occurs when
electrical components (surface-mount
devices) are machine picked and mounted
directly onto the surface of the PCB. During
this process, thousands of electrical
components are attached and connected to
their contact pads using reflow soldering.
Through-hole technology, also spelled “thru-hole”,
refers to the mounting scheme used for electronic
components that involves the use of leads on the
components that are inserted into holes drilled in
PCBs and soldered to pads on the opposite side
either by manual assembly (hand placement) or by
the use of automated insertion mount machines.

3. Types of PCB fabrication
Double-Sided PCBs Multilayer PCBs
Rigid PCBs
Flex PCBs
Rigid-Flex PCBs
Single sided PCBs

4. PCB FABRICATION PROCESS
1. Designing of electronics circuits & layout
2. Layout printing
3. Preparing substrate (A printed circuit board needs structure and shape. It
also needs a platform or canvass to hold all of its other components.)
4. Etching
5. Drilling
6. Solder mask application
7. Component assembly
8. PCB testing

5. DESIGNING OF CIRCUIT & LAYOUT
Softwares for PCB designing:- Proteus Professional/Eagle
PCB layout designing :-
1. Defining Trace Widths
PCB layouts use traces to connect components, but how wide should these traces be? The required trace width
for different nets depends on three possible factors:
• Manufacturability. Traces cannot be too thin, otherwise they can't be reliably manufactured.
• Current. The current carried in a trace will determine the minimum required width to prevent the trace
from overheating. When the current is higher, the trace will need to be wider.
For traces that don't need specific impedance or high current, a 10 mil trace width is fine for the vast majority of
low current analog and digital signals. Printed circuit board traces that carry more than 0.3 A may need to be
wider. To check this, you can use the IPC-2152 nomograph to determine your PCB trace width for a required
current capacity and temperature rise limit.
“1 mil = 1/1000 inch = 0.001 inch”
2. Make important nodes accessible.
3. Give space between components.
4. Place components with the same orientation.
5. Print the layout to see if components' sizes match.
6. Exchange wiring directions between layers.
7. Do not mount the electronic components within 1.27mm around the non-mounting holes, such as
tooling hole and standard holes.
8. Avoid placing holes under the components such as the horizontally mounted resistors, inductors,
(electrolytic capacitors, etc., so as to avoid short-circuiting the vias and component.

6. ETCHING
• ETCHING is an intaglio printmaking process in which lines or areas are incised using acid into a metal
plate in order to hold the ink. In etching, the plate can be made of iron, copper, or zinc.
• Chemical etching is usually done with ammonium per sulphate or ferric chloride.
• Process for using PCB etching machine:
1. Prepare Ferric Chloride Solution in the ratio of 1 KG Solid Ferric Chloride in 2 liters of water.
2. Put the solution in tank till the level touches 70% of the tank capacity. Make sure the heater and
temperature sensor tube is dipped in solution.
3. Set temperature to 50-55°C and after the solution is heated up to this temperature, dip the PCB hanged in
the hanger provided with the machine for 4-5 minutes.
4. Keep on inspecting the PCB after every 2 mins to avoid over etching.

7. DRILLING
PCB drilling, or printed circuit board drilling, is the process of creating holes, slots, and other cavities into an
electronic circuit board before soldering/mounting components onto it. It is typically done by using a PCB drill
bit (an automated machine) that is slightly smaller than the components placed on it.
Single-sided or double-sided PCB will be drilled directly after getting on the production line. Multi-layer
board will be drilled after pressuring layers. By classification of the function, different drilling holes can be
divided: through the hole, blind hole, Buried hole, etc.

8. SOLDER MASKING, COMPONENT
ASSEMBLY, PCB TESTING
A Solder mask is a protective coating over PCBs that prevents oxidation and electrical shorts. The solder
mask is coated over the entire board apart from the solder pads. The traditional green color coating that you see
on the PCBs is the solder mask. Uses Resin to coat the PCB to protect it from damage.
Soldering all components on right place leads to component assembly. And the resultant PCB is called as
Assembled PCB.
Final step in fabrication is – PCB Testing- which verifies the working of complete circuitry. Can be done by
manual , automated optical inspection , flying probe, x-ray inspection, etc methods.