The PCB board itself is made of insulating, heat-insulating and non-bending materials. The fine line material that can be seen on the surface is copper foil, which originally covers the entire PCB board. In the manufacturing process, part of the copper foil is etched off and the remaining part becomes a network of fine lines.
These lines are called wires or wiring and are used to provide circuit connections for parts on PCB boards. Usually the color of PCB board is green or brown, which is the color of solder resistance paint. It is a protective layer of insulation, which can protect copper wire and prevent parts from being welded to incorrect places.
The manufacturing process of PCB begins with PCB "substrates" made of glass epoxy or similar materials. The first step is to draw the on-line wiring between parts. The method is to "print" the printed negatives of PCB circuit boards on metal conductors by means of Subtractive transfer.
This technique is to lay a thin layer of copper foil on the whole surface and eliminate the excess parts. If a double panel is made, then both sides of the PCB's substrate will be covered with copper foil. And to do multi-layer board can do a good job of two double panels with a special adhesive "press" up.
Next, we can drill and electroplate the components on the PCB board. After drilling by machine according to drilling requirements, the inside of the hole must be electroplated (Plated-Through-Hole Technology, PTH). After metal treatment in the interior of Kongbi, the internal layers of wires can be connected with each other.
Before starting plating, debris must be removed from the holes. This is because the epoxy resin will produce some chemical changes after heating, and it will cover the internal PCB layer, so it must be removed first. Clearance and electroplating operations are accomplished in the chemical process. Next, it is necessary to cover the outer layer of the wiring with solder-proof paint (solder-proof ink), so that the wiring will not touch the plating part.
Then, various components are printed on the circuit board to indicate the position of each part. It can not cover any wiring or golden finger, otherwise it may reduce solderability or stability of current connection. In addition, if there are metal joints, then the "golden finger" part is usually plated with gold, so that when inserted into the expansion tank, high quality current connection can be ensured.
Finally, there is the test. Optical or electronic testing can be used to test whether PCB is short-circuit or open-circuit. Optical scanning is used to find defects in each layer, while electronic testing is usually done with a Flying-Probe to check all connections. Electronic testing is more accurate in finding short-circuit or break-circuit, but optical testing can detect the incorrect gap between conductors more easily.