Printed Circuit Board (PCB)
A Printed Circuit Board (PCB) is a flat piece of material mechanically used to support and electrically connect the electronic component using conductive tracks and pads along with other features etched or formed in copper sheets commonly laminate to a non-conductive substrate.
+----------------------------+
| PCB (Top View) |
| |
| [R]---[C]---[U]---[L] |
| | | | | |
| V V V V |
| Res Cap IC LED |
+----------------------------+
Legend: printed in PCB:
[R] = Resistor
[C] = Capacitor
[U] = Integrated Circuit (IC)
[L] = Light Emitting Diode (LED)
Tracks = Copper lines that connect all the parts
PCB Component Function:
Resistors (R) limitation of current flow
Capacitors (C) Charge and discharge electric energy
ICs(U) Chips; brains of the circuit; do the computations/ logic
Led (s) (L) Light-emitting diodes ( LEDs ) Turn on when current moves through
Copper Tracks: Join pieces; such as electrical roads
Substrate Non conductive board material (e.g fiberglass)
The functionality of a PCB:
- The Power Source feeds electric current in the PCB.
- Copper Traces make the electricity flow to components ( resistors, capacitors, and ICs ) Explanation.
- It has dedicated components (e.g. an LED blinking component, a signal processing component)
- Correct operation needs electricity passing through a control path.
- The end product is realized (light, movement, signal etc.).
Consider your PCB a city map:
Copper stains = streets
Components = buildings
Electricity = traffic
PCB regulates the flow of traffic and destination.
Printed Circuit Board manufacturing process:
1. Design & Output
Eagle, KiCAD, Altium
Output: Gerber files (data files which indicate to machines where to print copper, and what holes to drill, etc.)
2. Bringing the PCB Layout to output
- A plotter is used to print design on a film (photomask).
- It serves as a guide on etching copper on the board.
3. Copper Cladding
- The copper is laminated on both sides of a fiber glass board.
- Tracks are built on this.
4. Photoresist Coating
The board is covered with the photoresist, a light sensitive material.
5. UV Exposure
- The film is used in transferring the PCB design onto the board via UV light.
- Areas not exposed to light are cleaned up leaving a pattern.
6. Etching
- The board when immersed in a bath of an acid.
- The unwanted copper is removed using acid - only the wanted tracks left.
7. Drilling
Mounting components, as well as vias are drilled (using CNC machines) with very great precision.
8. Plating /Copper Deposition
Electroplating involves placing copper in the holes drilled to enable the interconnection of layers.
9. Solder Mask and Application of the Mask
- Copper tracks are covered with a layer of a green (or other) solder mask.
- Components are only soldered on the pads.
10. Silkscreen Printing
Warnings, names of the components, logos are printed.
11. Electrical Testing
Automated testing looks at short circuiting or open circuiting.
12. Cutting / Profiling
During CNC-routers or V-cutting, large production panels are cut into individual PCBs.
13. Inspection
Final inspection is to make sure that the work is functional, straight and finished well.
Thanks.
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