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Tuesday, 29 November 2011

Exception PCB: What are Printed Circuit Boards?



A PCB, also known as Printed Circuit Boards, is very commonly used in the Electronics industry. A PCB is used for supporting and connecting electronic components. For this purpose pathways or tracks are etched from copper sheets which are laminated on a non-conductive substrate. PCBs are also called PWBs or printed wiring board.

The advantages of PCB are that it is very economical to use and is extremely reliable. Compared to other methods of attaching electronic components like wire wrap or point to point construction, PCBs can be tedious to make the layout and the initial cost are also higher. But in large scale production, they work out much more cheaply and faster. They are faster because the production and soldering of the circuit boards can be done by pre-set equipment. The PCB quality control guidelines have been spelled out by the IPC organization which is accredited by the American National Standards Institute. The UK based eXception PCB, is one of the major suppliers of complex printed circuit boards to the aerospace and defence sector. By gaining accreditation for AS 9100, the company has added another feather in its cap. Exception PCB has boosted its credibility and capability by the accreditation and is now planning to gain approval for the medical certification for PCB manufacturing in order to strengthen their medical customers’ needs.

Printed Circuit Boards were developed as early as in the 20th century. The invention of the printed circuit has been credited to an Austrian, Paul Eisler. Conducting layers in PCBs are made of thin copper foil. Most of the PCBs are made by patterning or etching. A layer of copper is bonded over the entire substrate and any unwanted copper is removed by applying a temporary mask. In this way only required copper traces are left intact. PCBs manufactured in large scale are used for silk screen printing and photography industries. In small scale, the PCBs are used to print on transparent film and also for use as photo mask. They are also used in laser resist ablation and in a CNC mill with a cutter. Hobbyists use it for laser printed resist on transparency film, for heat transfer with a laminator and other labour-intensive methods for vinyl fills and no washable markers.



PCBs are also used for chemical etching using ferric chloride and ammonium persulfate. The method in its simplified form is used by hobbyists for immersion etching. There are also multi-layer PCBs which have trace layers inside which are formed by bonding together individually etched boards. Drilling in a PCB is done through small diameter drill bits which are usually coated with tungsten carbide. The soldering on PCBs is done by plating with solder, tin or gold over nickel. A large variety of soldering techniques are used to attach components on to the PCB. In large scale production of PCBs, bulk wave soldering is done by machine placement.

The PCBs which may pass through extreme environments normally have a conformal coating which protects the PCB. This coating is done by spraying the components that have been soldered. The coating is known to protect the PCBs against corrosion and leakage. Since most of the PCBs are static sensitive, they are put in antistatic bags during transportation. It is important for the user to be grounded while handling these boards. There are different types of PCB construction like Cordwood construction which is known to save space used with wire ended parts in appliances where saving of space is a prerogative. The multiwire boards are an interconnected technique using insulated wires in a non-conducting plastic resin matrix. The surface mount technology used components redesigned to hold metal tabs that could be soldered to the PCB surface. Exception PCB, a company restructured from its American parent company, DDI, have been manufacturing PCBs for sectors that are wide ranging from Aerospace, Automobiles, Transportation, Oil and gas, communications, medical and marine, semiconductors and even Formula one.

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