There are many applications for flexible circuitry in the automotive industry and in some instances it may be necessary to provide EMI/RFI screening and this can be accomplished a number of ways. The most cost effective approach, and coincidentally the one which provides the most flexible construction, is to use silver Polymer screens encapsulated with a screen-printed or photo-imageable covercoat. In some flex cuircuit board applications it may be necessary, because of the frequencies involved, to resort to cross hatched screens.
The assembly techniques, when using flexible circuits, vary according to the material and the type of assembly. Simple crimp-on or ZIF (zero insertion force) mechanical connectors for interfacing with the outgoing world are more than adequate and the connector industry is responding to the need for lower profile, lower mass, reliable connector systems more befitting this technology than is the case with traditional connectors.
The weight savings in automobiles when comparing flexible circuits with a conventional wiring harness are very considerable with flexible circuits on its own often weighing less than 20% of their more traditional counterparts. This, coupled with the prospect of lower mass connectors, means a massive gain for the automotive industry.
The current carrying capability for any allowable temperature rise depends on both resistance and the ability to dissipate heat by conduction, convection and radiation. The thin, flat form of flexible circuit conductors makes them better heat dissipators than round wires of equivalent cross section, see figure
Typically, an electric sunroof or electric window motor requires around 8A and the flexible circuit will easily handle these relatively heavy currents, or indeed signal currents in alarm detector circuits.
Flexible circuits have been in existence for many years, most applications have been limited in most cases to general electronics and not until recently has the car become another highly complex electronics package. For example, when one of the world’s leading automotive electronics manufacturers wanted to produce a new electronic lock for a luxury car maker the problems and costs involved in joining four small printed circuit boards with connectors or a flex rigid multi-layer almost resulted in the project being abandoned.