2. Introduction to a Printed Circuit Board
• A printed circuit board (PCB) mechanically supports and
electrically connects electronic
components using conductive tracks, pads and other
features etched from copper sheets laminated onto a nonconductive substrate.
• PCB's can be single sided (one copper layer), double
sided (two copper layers) or multi-layer.
• A PCB populated with electronic components is called a
printed circuit assembly (PCA), printed circuit board
assembly or PCB assembly (PCBA)
3. What PCB is made of
• A basic PCB starts with a copper-clad fiberglass material or
thin copper sheets attached to either side of the board. It
consist of : Copper Foil
Copper Plating
Solder Flow
Solder Mask
Trace
Slots and Cut-outs
4. FABRICATION
Following are the basic steps of PCB design.
• Set-Up
• Imaging
• Etching
• Drilling
• Masking
• Silk Screening
• Route
• Electrical Test
5. PCB characteristics
• Through-hole technology
The first PCBs used through-hole technology, mounting electronic
components by leads inserted through holes on one side of the board
and soldered onto copper traces on the other side. Boards may be
single-sided, with an un plated component side, or more compact
double-sided boards, with components soldered on both sides
• Surface-mount technology
Surface-mount technology emerged in the 1960s, gained momentum in
the early 1980s and became widely used by the mid-1990s.
Components were mechanically redesigned to have small metal tabs or
end caps that could be soldered directly onto the PCB surface, instead
of wire leads to pass through holes
6. Etching process
Chemical etch
• Chemical etching is usually done with ammonium per
sulphate or ferric chloride.
• For PTH (plated-through holes), additional steps
of electroless deposition are done after the holes are
drilled, then copper is electroplated to build up the
thickness, the boards are screened, and plated with
tin/lead. The tin/lead becomes the resist leaving the
bare copper to be etched away.
Cont.…
7. Laser/Plasma Etch
• A new process creating new standards and the
demise of the chemical process is plasma etch.
In addition to no etch-back, this process also
eliminates imaging, or film error using a direct
imaging process, which transfers the layer
image directly to the material.
8. Design Assembly
• Manual Assembly
• Auto Assembly
Hole preparation is normally done
in the manufacturing process that
plates/or coats the exposed copper
areas with solder. This prepares
the surface of pads, as well as the
hole itself, with a fine coat of
solder that will make soldering
easier by helping the solder
adhere to the pad and hole wall
and helping the solder to "wick"
through the hole.
Auto assembly is an automated
process where most of the
component on a board are placed
and soldered to the board by
machine. Auto assembly requires
additional information from the
designer, in addition to the
standard Assembly information
provided for manual assembly.
9. Assembly Limitation
• The number of parts that can be assembled in
one pass
• Double-sided assembly
• Overall panel/board size
• Component size
• Component types (surface mount or thru-hole)
10. Routing
• Manual Route
• Auto Route
Route the following types of
nets first:
• Most difficult
• Most complex
• Tight fitting nets first
• Very high current
(primarily external)
• Very high voltage
(primarily internal)
• Manually route those
items shown in "manual
routing " first, if
necessary.
• Manually clean up paths.
• Miter right angle corners.
• Run DRC /design rules to
ensure clearances are met.
• Check annular ring.
11. EAGLE
• Stands for Easily Applicable Graphic Layout
Editor
• flexible, expandable and scriptable EDA application
with schematic capture editor, PCB layout editor,
auto-router
• Latest version is 6.1 and minimum requirements are
MAC OS X 10.6, Linux 2.6 and Windows XP.
14. Power supply board
• A power supply is a device that
supplies electric power to an electrical load.
• Power converters that convert one form of
electrical energy to another.
• Power supplies for electronic devices can be
broadly divided into line-frequency (or
"conventional") and switching power supplies.
