When using MIL-HDBK-217F, Notice 2, depending upon device type, the number of transistors or gates is required in order to determine the base failure rates (C1) for microcircuits. The number of transistors or gates can often be estimated from block or circuit diagrams that may be included in vendor data sheets, even if the exact number is unknown. If this information cannot be extracted from the data sheet, it may be possible to contact the manufacturer and obtain the information from them. A last resort would be to use the worst case estimate of C1 for the given device type – especially if the device is complex.

Alternatively, the use of 217Plus failure rate models may be considered. When using 217Plus, the transistor/gate count is not necessary to predict microcircuit failure rates. Instead the device type (digital IC, linear IC, memory/microprocessor, etc.) is all that is required to determine the base failure rate for a microcircuit. Additional factors such as packaging, junction temperature, humidity, temperature cycling extremes and cycling rates are then applied to determine the overall device failure rate.

Richard Wisniewski,
Senior Reliability Engineer
Defense Systems Information Analysis Center (DSIAC)

Please note that the RIAC has been transitioned to the newly-formed Defense Systems Information Analysis Center (DSIAC). Inquiries related to the technical areas of reliability, maintainability and quality (RMQ) can continue to be made to the toll-free number at (877) 363-7422.