The line between science and magic can easily be blurred for the average layman who primarily uses their laptop to check their email and watch cat videos. Printed circuit boards are a complex piece of engineering that allows us to seamlessly communicate with people on the opposite side of the world, or make your child’s toy speak to them when they press its button. To understand how circuit boards work, you must first know how they are constructed and how each step plays a crucial role to ensure an easy to use product. Printed circuit board assembly is easily done by heavy machinery, but some people still like to create the circuit board by hand to fit their unique needs. The assembly of these boards is done in a relatively easy seven-step process that includes creating a base circuit board, solder pasting, pick and place, reflow, inspection, component insertion, and then a final functionality test.
Printed Circuit Board Base
The green base of the circuit board has four layers: a substrate, copper, solder mask, and silkscreen. The substrate provides a firm base for the components to safely rest on. The copper acts as a conductor for faster transmission of currents. The solder mask acts as an insulator to protect against accidentally soldering the wrong pins. The silkscreen is the last layer that has letters and numbers to make it easier to decipher.
When your circuit board is ready for the assembly line you will place a thin steel stencil over the board and apply soldering paste to the uncovered areas. The solder paste will help the solder bond with a surface.
Pick and Place
During this process, the circuit board is placed on a machine where it will be suctioned to a robotic arm and moved down the assembly line where surface mounted components are attached to the board where the solder paste was applied.
During the reflow process, you will remove the board from the pick and place machine and place it on another assembly line where it is heated to 250 degrees. This extreme temperature will melt the solder in the paste and create a strong bond that will hold for a very long time.
Once the circuit board is removed from the industrial oven it will be manually inspected as well as an Automatic Optical Inspection (AOI). This AOI is equipped with several cameras that will closely examine all the solder connections and make sure everything is up to standard.
Some circuit boards have components that need to be inserted in hole built into the board during the first stage when the base was created. Once these components have been inserted they will go through a process called wave soldering where solder is applied to the entire bottom of the board and run through another oven.
Once the circuit board has completed this process it will go through one final stage of inspection where the functions will be tested to ensure usability for the consumer.