Case study of product defects found by air discharge mode ESD but missed by contact ESD

Product ESD immunity testing to meet European EMC Directive called for air discharge and contact mode ESD tests; however when testing product with exposed metal areas then contact mode is the specified method. In this paper 2 cases are documented to demonstrate that air discharge mode used exclusively on product with plastic or insulated covers/chassis should not be taken a backseat to contact ESD for exposed metal areas. In fact both methods should be used to complement each other when testing products.