Single Sided (Conventional) Circuit Boards
Although the single sided PCB is the most basic and the start point of printed circuit technology and indeed, the start point of the invention, it still plays a major role in the industry.
The PCB was invented to give a good mechanical base for components and by using printing to produce the tracks allowed repeatability of interconnections in volume.
It also means reliability of connections compared to handwiring and another big benefit is ease of assembly production of an electronic device in volume.
In through hole device technology, it does have its limitations in interconnecting large numbers of components as all the tracks are on one side but it is a cheap way of gaining all the above benefits on more simple circuits.
Due to surface finishes like Lead free hot air level, Nickel Gold and organic surface protection, single sided boards can used for surface mount devices as well as through hole. Using this technology, although the PCBS are relatively simple, they can still be used in very complex devices. This is quite often apparent on LED technology.
The double sided “PTH” (plated through holes) PCB is the universal workhorse of the electronics industry. With increasing complexity and density of components many PCB’s need to use both sides of the Printed Circuit Board. This is more usually supplemented with plated-through-holes where the copper connections go right through the connecting holes to the opposite side of the board. These PTH Connections either form simple electrical connection between both sides of the PCB (Via Holes), or electrical connectivity and mechanical support for leaded components. This makes the double sided PTH PCB a much more physically robust item.
The multilayer PCB is the development of the double sided PCB. With increasing complexity and density of components many designers were struggling to find the route and size required for modern instruments. Adding just a power and ground plane to the inside of the board allowed the components to be powered with just two plated holes to the inner layers rather than a track back to a power/ground point. Once the technology to multilayer PCBs was established, it was further developed to have additional signal layers inside. This allowed the designers to produce highly complex and compact circuits and further development of blind and buried via hole technology has pushed these limits even further. The highly complex PCBs now being offered allow high density packaging to the designer’s requirement and in line with the most complex components.