Printed circuit boards (PCB’s) are in almost everything we use today connected to a power source. You will find them in radios, cars, smartwatches, and most electronic products. Circuit boards are what tie all of the components together in electronic devices.
Printed Circuit Board Material
Most PCB’s are rigid boards, but a small percentage of them are flexible so they can move without breaking circuit connections. A circuit board is usually custom-made for a specified purpose. You cannot take a circuit board from a car and expect it to work in something else.
The most common material is glass fiber, known as FR4. The reason for this material is that it provides stability under temperature fluctuations and is not an expensive material. The type of material also depends on the application for the printed circuit board. Other materials like PTFE (Polytetrafluoroethylene) are used for high-frequency radio communications.
Etching the Tracks Onto the Printed Circuit Board
The tracks are made of copper and are what connect the electronic components. This process is usually done with chemical etching using ferric chloride. A photographic process is used to get the proper pattern for the copper tracks. The PCB is covered in a thin layer called photo-resist and exposed to light through the photographic film.
Once the photographic process is completed, the circuit board is placed into the ferric chloride to etch the areas where no copper tracks are needed. If the board is placed in this etch for too long, ferric chloride could get under the photo-resist layer and damage the board.
Making the Holes
Now it is time to make the holes or known as via holes (vias). The holes are where the components will go, like resistors and capacitors. The inner surface of the holes has a copper layer to make an electrical connection to the copper tracks that connect the components.
The plated through holes process is done using a plating process. PCB CAD design software is used to drill the holes in their proper places.
Printed Circuit Board Silk Screen
A printed circuit board will usually have printed text to help identify the various components and their values. Printing component values and position helps anyone who has to troubleshoot and repair a circuit board if needed.
Soldering the Components
During soldering, it is important to keep areas of the printing circuit board that are not supposed to be soldered protected by a solder resist layer. The solder resist prevents solder from being applied to portions of the PCB where it doesn’t belong.
If solder is applied where it doesn’t belong, a short circuit can develop, ruining the circuit board. The solder resists areas are made of a layer of polymer and are usually colored deep green or red on the board.
You can find printed circuit boards on all electronic devices. The board first has to be designed with the copper tracks laid out. Then the tracks are etched into the circuit board and silk-screened with the components and values listed in their proper spots. The components are then soldered onto the board. Once completed, the circuit board will be used in electronics.
