PCB Fabrication Flow
First, panels are coated using a light-sensitive film.
Then the images from the artwork are then printed on these coated panels.
The printing is acid-resistant and thus allows the unwanted areas of the copper panel to be etched away.
Leaving is only the parts forming the circuit.
The etched layers are then laminated together.
They are pressed together with thin sheets of resin-coated fiberglass.
Which are at high pressure and high temperature. As the board cools the layers bond together.
The next stage involves drilling holes.
These holes are positioned using the drill data from the Gerber data file.
Some of the circuits on different layers. It will need connecting together.
This is achieved using a process called the “through-hole plating”, the PTH process.
A solder mask is then applied as a coating to protect the circuit.
Which is from any solder splashes applied during the final PCB assembly process.
Naturally, some of the circuits must be left exposed. Where soldering is required such as surface mount tabs, connection holes, etc.
The printed circuit board is now virtually complete. And just needs finishing off.
This involves cutting the board to size. Then there is electrical testing for open circuits and short circuits.
As well as a manual eye inspection to ensure high quality.
Some processes have AOI, Automatic optical instrument Process.