These damage can be manifested as the immediate failure of the device, may also occur in the over-current shock after a long time to failure, shorten the working life of Ji'nan luminous word.

The reliability index was applied on basis of the analysis on the failure mode. And according to the sampling theory of reliability a reliability test method was put forward.

The electromagnetic pulse(EMP) damage mechanism and failure modes are obtained for the input port and output port of solid state relays by current injection method.