Printed Circuit Boards and IPC Standard
The general parameters to be considered before and during the design of any printed circuit board, but focuses on boards incorporating copper weights ≥ 3oz/ft2. The following parameters can and will have a major impact on reliability and performance of the end product. A comprehensive listing of all parameters and their design/performance tradeoffs is shown in IPC-2221.
The end-product requirements must be known before design start-up. Servicing and maintenance of the end product can directly influence conductor routing, part placement, board size, markings, coatings and final finish.
Finished printed circuit boards manufactured must meet or exceed the performance requirements of IPC-6011. There are three general end product performance classes that IPC-6011 has established. Class 1 is "general electronic products", Class 2 is "dedicated service electronic products" and Class 3 is "high reliability electronic products". Please see IPC-6011 or IPC-2221 for more information on the 3 classes.
There are several material choices available to the designer, ranging from standard printed circuit board epoxy resins to advanced dielectrics with specialized properties. There are a number of properties the designer must consider, including but not limited to; temperature (soldering and operating), electrical properties, structural strength, flame resistance, machine ability, thermal conductivity and thermal stability. Laminate materials should be selected from materials listed in IPC-4101.
It is important to note that for high current designs the temperature rise due to current flow in the conductor, when added to all other sources of heat at the conductor/laminate interface, do not exceed the maximum operating temperature specified for the laminate or the assembly. Materials used (prepreg, copper-clad, copper foil, heatsink, etc.) and minimum dielectric thickness/spacing must be specified on the master drawing.