Printed circuit boards or PCBs are designed to support electronic components that are soldered onto copper pads in drilled holes in board or surface mount applications. A board design may also be a mix of surface mount components and through-hole components.
Printed circuit boards connect all the required leads electrically
with the help of conductive copper traces. The connection traces are
actually copper engravings on a non-conductive material. PCBS are
usually single sided with copper engravings on one side only. However,
there are other PCBs that are double sided with copper etchings and
component pads on both sides of the surface.
Copper tracings are etched onto the surface of the board as part of the manufacturing process of the PCB. There are multilayered boards in production that consist of several layers of dielectric substance drenched in adhesives. These layers separate the copper engravings. After aligning all these layers, they are attached into a single board structure. Presently, PCBs with more than 48 layers are being produced commercially.
This process involves deciding which materials should be used, what process should be employed, and determining the specific requirements of the customer. This is ascertained from the Gerber file information that is provided alongwith the purchase orders.
Imaging the Design
The Gerber file data is transferred onto a film which is positioned on the conductive copper layer.
Etching the copper traces
This is the traditional process that involves exposing the copper which is protected by the film, as well the other unprotected areas, to a chemical which removes all of the unprotected copper. At the end of the process, the protected copper traces and pads remain in place. Modern techniques use etching with the help of plasma laser rather than making use of the chemicals for the purpose of removing unwanted copper material. This allows for more defined copper lines.
Drilling holes inside the board
The process involves drilling holes for applications that will be plated through applications. A second drilling process is carried out for holes that will not be plated through. All the information regarding the locations of these holes and their respective sizes is given in the drill drawing file.
Masking the copper traces
The process involves application of protective material over the bare copper etchings in order to protect them from possible damage caused by the environment. The masking also provides insulation.
This process involves coating pad areas with a thin solder layer in order to prepare the PCB for reflow soldering or wave soldering procedures that will be carried out later after placement of the components.
After the printed circuit boards have been completed, a visual inspection of the PCBs is carried out in order to ensure the quality of the boards. A test of continuity is also carried out on the printed circuit boards by applying a voltage between different points and determining the flow of current. Every PCB manufacture has his own set of tests and checks that are put in place in order to ensure the production of high quality printed circuit boards.
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