THE STORY OF PCBS part I
Printed circuit boards have come a long way since their initial creation, many different small changes happened over their lifespan to create the PCB that is so useful today, being integral to many pieces of technology.
It was around 1925 that Charles Ducas created a patent for an electrical path straight onto an insulated area. Soon after that, Paul Eisler created the first real printed circuit board while working in England approximately around 1936. Early PCB designs were even inserted onto plain wood.
Quite some time afterwards in 1943, they began to be used for proximity fuses in World War II. In the 1950s and 1960s they began to have one side having the electrical parts and the print on the other side. The “Process of Assembling Electrical Circuits” was brought about by the US, and they improved upon the old methods by creating the pattern and then inserting it on the zinc plate. They would then use this plate to print the wire on top of the foil. This proved viable and was a major breakthrough.
New methods and efficiency
Boards were starting to be designed with more advanced methods in 1960. Corrosion stopping methods started to be implemented that protected the traces and components and keep them cleaner and more efficient. In the 70s a gradual reduction in size led to the soldering being hard to perform without bridges forming between pads. This led to solder masks which are a thin layer of polymer applied to the copper to prevent the bridging. Japanese industry experts started to create an alternate method known as liquid photoimageable masks. A layer of photo-polymer is coated onto the circuit which is then dried under controlled temperatures. It is after this point that it removes unneeded solvent, and then the areas of the solder mask film are compared against the track to see what is necessary. This became the industry standard going forward.