Three general end-product classes have been established by the association connecting electronics industries(IPC) to reflect progressive increases in sophistication, functional performance requirements, and testing/inspection frequency. It should be recognized that there may be an overlap of equipment between classes. The written contract shall specify the performance required and note any exceptions to specific parameters, where required. These classes are as follows:
Class 1- general electronic products. This includes consumer products, some computer and computer perihperals, as well as general military hardware suitable for applications in which cosmetic imperfections are not important and the major requirement is function of the completed board or assembly.
Class 2- Dedicated service eletronic products. Includes communication equipment, sophisticated business equipment machines, instruments and military equitment in which high performance and extended life are required and for which uninterrupted service is desired but not critical. Certain cosmetic imperfections are allowed.
Class 3- High Reliability electronic Products. Includes commercial equipment and military products in which continued performance or performance on demand is critical. Downtime cannot be tolerated and equipment must function when required such as for life support items or critical weapons systems. Board assemblies in this clss are suitable for application where high levels of assurance is required and service is essential.
2 Flexible materials
Materials used in the fabrication of either flexible or rigid flexible printed wiring boards are divided into three parts: the dielectric(either rigid and/or flexible), adhesives, and the conductor.
3 dielectrics
The majority of single- and double-sided flexible circuits fabricated today are produced using either copper polyester or polyimide films
as the dielectric. However, other materials that can be used as dielectrics are Teflon, polyethylene naphthlate(PEN), and polyethylene terephthalate(PET).
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