Printed Circuit Board Assembly

A printed circuit board assembly can be found almost everywhere. It is the component that is found in almost any electronic device, from an MP3 player to the navigation systems on the International Space Station. How is it made? What is it made from? Where did it start? Most of these questions cannot be answered by the average person on the street, for they are seemingly complex at first glance and it would seem to take an engineer to understand it's mysterious workings. However, a printed circuit board assembly is not as complicated as one would suspect. The process begins with the board itself, which is coated with a soldering mask that gives the printed circuit board assembly it's green color. The masked board is then bonded with a layer of copper, which will later serve as the conductor between the electronic components after a process called patterning or etching. The unwanted copper can be removed with a variety of techniques such as silk screen printing, photoengraving, and PCB milling.

The basic pattern of the conductive pathways can be seen, and the printed circuit board assembly is well on it's way. After the board is masked and the copper pattern is laid down, then it comes time to mount the various electronic components onto the board. The 'unpopulated' board (a printed circuit board assembly with no electronic components) may be subject to testing to make sure the voltage readings are up to spec. This is after holes are cut into the board in which to mount the components using either special drills or lasers that evaporate the surface of the board. When the holes are in place and the board has been subject to testing, then the electronic components are mounted into the holes. Although drilling or burning holes into the board has been the traditional way of making a printed circuit board assembly, another technique uses no holes in which to mount the components. The electronic components are mounted on 'pads' or 'lands' and are connected to each other via the copper pathways.

This no hole technique has become more favorable recently do to the ability to make the printed circuit assembly smaller and more efficient. After the components are mounted to the board, it is subject to more tests to ensure it functionality. After the components are mounted and soldered, the printed circuit assembly is then coated with a substance to prevent corrosion or shorting out due to moisture. The first substance used to coat the boards used to be wax. As time went on different coatings were used on the board such as silicone rubber, polyurethane, acrylic, or epoxy. The printed circuit assembly is then placed in static-free bags due to their sensitivity to static electricity. From there, they are placed within the electronic device they were designed for. From it's earliest beginnings in radio, the printed circuit board assembly as come a long way. However the process of it's creation has remained largely the same. As more electronic devices are invented, there will be a higher demand for the printed circuit assembly to evolve into whatever form is asked of it.