What is Printed Circuit Board
Before we start to talk about the history of printed circuit boards, we need to figure out firstly what a Printed Ciruit Board (usually called PCB) is. A printed circuit board (PCB) mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. PCBs can besingle sided (one copper layer), double sided (two copper layers) or multi-layer (outer and inner layers). Multi-layer PCBs allow for much higher component density. Conductors on different layers are connected with plated-through holes called vias which were covered in previous blogs. Advanced PCBs may contain components – capacitors, resistors or active devices – embedded in the substrate.
Printed circuit boards are applied in various industries and business. It requires the additional design effort to lay out the circuit, but manufacturing and assembly can be automated. Manufacturing circuits with PCBs is cheaper and faster than with other wiring methods as components are mounted and wired with one single part. Furthermore, operator wiring errors are eliminated.
PCBs are grouped into 3 main types, namely Single Sided Board, Double Sided Board, and Multi Layered Board.
Single Sided Board is the least complicated of the Printed Circuit Boards, since there is only a single layer of substrate. All electrical parts and components are fixed on one side and copper traces are on the other side.
Double Sided Board is the most common type of board, where parts and components are attached to both sides of the substrate. In such cases, double-sided PCBs that have connecting traces on both the sides are used. Double-sided Printed Circuit Boards usually use through-hole construction for assembly of components.
Multi layered PCB consists of several layers of substrate separated by insulation. Most common multilayer boards are: 4 layers, 6 layers, 8 layers, and 10 layers. However, the total number of layers that can be manufactured can exceed over 42 layers. These types of boards are used in extremely complex electronic circuits.
Point to point construction was used before printed circuits became the popular component used in electronics. It meant a few extremely bulky and unreliable designs that required large sockets and regular replacement. However, most of the issues were addressed when PCBs went into regular production.
For prototypes, or small production runs, wire wrap or turret board can be more efficient. Predating the printed circuit invention, and similar in spirit, was John Sargrove’s 1936–1947 Electronic Circuit Making Equipment (ECME) which sprayed metal onto a Bakelite plastic board. The ECME could produce 3 radios per minute.
The Austrian engineer Paul Eisler invented the printed circuit as part of a radio set while working in England around 1936. Around 1943 the USA began to use the technology on a large scale to make proximity fuses for use in World War II. After the war, in 1948, the USA released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-assembly process was developed by the United States Army. At around the same time in Britain work along similar lines was carried out by Geoffrey Dummer, then at the RRDE.
Originally, every electronic component had wire leads, and the PCB had holes drilled for each wire of each component. The components’ leads were then passed through the holes and soldered to the PCB trace. This method of assembly is called through-hole construction. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the Auto-assembly process in which component leads were inserted into a copper foil interconnection pattern and dip soldering. The patent they obtained in 1956 was assigned to the U.S. Army. With the development of board lamination and etching techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes are wasteful since drilling holes is expensive and the protruding wires are merely cut off.
From the 1980s small surface mount parts have been used increasingly instead of through-hole components; this has led to smaller boards for a given functionality and lower production costs, but with some additional difficulty in servicing faulty boards.
Currently, most circuit boards use multi-step methods such as conventional vacuum deposition and photolithographic patterning. However, these methods have certain disadvantages since they require a high processing temperature, involve toxic waste, and are costly. We have seen advances in technology in previous years and it’s not hard to imagine PCBs will soon be revolutionized. With the use of 3d printing become more mainstream ‘3d printing’ a printed circuit board has become realized.