PCB's are small devices that hold electronic circuitrychips. There are a number of different steps that go into making a PCB, from designing it to manufacturing it. Whether you're working on your own or using a PCB manufacturer, understanding how a PCB is made step by step will help you
understand the entire process.
The Design of a PCB
A Printed Circuit Board or PCB is made of copper layers thatimpose traces and planes to route electricity throughout the board. These layers can be single sided for simple electronics and multilayers for more complex ones, like those found in your smartphone.
Layers are arranged to make the desired circuit layout, thensent to the printer. A plotter printer creates a "film" of the board, much like a photo negative. This film is printed on a laminate material that will become the body of the final product.
The design of a PCB is based on a computer-aided design(CAD) program, such as DesignSpark. The program then produces output files that are necessary for production of a finished PCB, such as Gerber and NcDrill files.
These files outline the placement of copper pathways,soldermask, and silkscreen. They also contain information for creating a laser stencil that is used for assembly of the finished board.
Next, the plan is sent to the manufacturer to be fabricatedinto a board. Depending on the size and complexity of the board, this can take anywhere from a day to several weeks.
The manufacturer may use an automated drilling machine todrill tiny holes called VIAS, which allow the board to connect to other layers on the same or a different PCB. Precision placement of these holes is important for efficient production.
Before drilling, the board is inspected and tested fordefects. It is then moved on to the next step of the process, which involves laminating the boards together.
This process takes two steps and involves a combination ofepoxy resin and glass fiber. The outer layers of the structure are covered in a special, photo-resist film that hardens when exposed to ultraviolet light. The photo-resist film protects the copper from etching, and it also shows the
manufacturer where bits of copper should be removed to make room for the components that will eventually be placed on the board.
After a UV light is passed over the photo-resist, it startsto harden in areas where there will be copper traces or planes. The resulting pattern of copper pathways is then used to guide the manufacturer in the fabrication of the board.
Once the traces are etched, it's time to remove thephoto-resist and expose the copper. This is done in multiple phases and requires solvents that can vary from one company to another.
Depending on the size and complexity of the structure, acopper etching machine will then be used to etch away the copper. This is often the most tedious part of the manufacturing process, but it is essential for a properly functioning board.
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