How Circuit Boards Are Made

Computer electronic boards are basically a bunch of holes surrounded by conductive materials. How do circuit boards work, They allow electricity to pass in certain orders and are vital for the operation of almost every electronic device we use today – phones, tablets, computers, TVs and cars - all of them have circuit boards that connect all the different parts of the devices and make it possible for them to communicate with each other. There are a number of components that make the circuit board work including resistors, capacitors and diodes. They each have a specific job, for example, the resistors apply a certain amount of resistance to the current so that it does not exceed a safe limit. The capacitors store electric charge and then release it when the board needs power. The diodes block signals that might cause interference from passing through the board and they also make sure the current only passes in one direction to avoid damage.

The first patent for a PCB was filed in 1903. It was an electro-mechanical device that had flat conductors on a multi-layer insulating substrate with through-hole construction. This was the precursor to modern day PCBs. However, it was not until the mid-1960s – while Elvis Presley was shaking his pelvis and the United States ramped up its space program and the Cold War was heating up – that two important developments occurred in PCB technology. The first was a plated hole-through technology that allowed tightly spaced component pins to be placed on the PCB without overlapping and the second was surface mount technology that made it possible to solder components directly onto the copper traces.

Both through-hole and surface mount technology can be achieved either by additive or subtractive methods. In additive PCB fabrication the bare substrate is covered with photoresist that is exposed to light through a pattern that corresponds to the desired layout of the components on the board. The unexposed areas are then removed and the copper on both sides of the substrate is etched using a potassium permanganate-based etching solution. The etching removes the copper but leaves behind a thin layer of resin and glass fiber that is often coated with a phenolic or polyimide material such as FR-4, FR-1, FR-5, or CEM-1.

In the subtractive method a pattern is printed on a clear mylar sheet that is then laid over the bare laminate and exposed to a light source through another mask. The resulting negative is used to mass-reproduce the desired pattern on the photoresist that has been applied to the bare substrate. The resulting mask is then stripped and the substrate with copper is plated in the desired pattern using a chemical bath.

Computer circuit boards contain a wide range of toxic chemicals, and when they are discarded they can pollute the environment by leaching these chemicals into soil or water. This can cause respiratory problems and other health issues for animals and humans. Recycling PCBs helps to reduce this pollution by keeping these toxic chemicals out of landfills where they can seep into the groundwater and contaminate nearby water sources. It also cuts down on the need for more raw materials to be mined and processed, and it saves energy as it takes less energy to recycle existing materials than to produce them from scratch.