Precision foil resistors used as electro-pyrotechnic initiators

The proliferation of airbags and other pyro-technically deployed safety devices in new cars will require a costly increase in the number of energy-storage devices needed for each vehicle. If the activation energy could be reduced, cheaper storage capacitors can be used. However, the low energy levels contemplated would reduce the diameter of the resistance wire traditionally used to initiate the pyro-technic chain that results in airbag deployment. The wire diameter then becomes so thin that it introduces numerous problems, all of which reduce reliability in critical safety systems. Foil resistors, in which a thin planar foil is supported on a substrate and etched to precise thermal and electrical specifications, were developed and tested to replace traditional initiators for low energy applications. This paper describes the products developed, the affect on associated concerns within the industry, and the reliability tests performed on low energy foil initiators.