Failure Rate Model for a Hybrid Device
The failure rate model for a hybrid device is based on the concept that the overall failure rate of a hybrid device depends upon the following:
• The failure rate contribution of the individual integrated circuits and/or discrete components (λC) that form the hybrid device. Because the components of a hybrid device are relatively free of the many parasitic elements that may be associated with monolithic devices, the failure rates (λC) are adjusted by a die correction factor, KG, depending upon the type of component concerned.
• The failure rate contributions of:
◦ Each of the chip or substrate resistors, λr, depending upon the hybrid package temperature.
◦ Each of the interconnections within the hybrid, λI, depending upon the type of connection and the package temperature.
◦ The hybrid package, λS, depending upon the package temperature and seal perimeter.
Each of the above failure rate contributions will further depend upon the intended operational environment of the device and its particular circuit function. Therefore, the failure rates are adjusted by an environmental factor, KE, and a circuit function factor, KF.
• The failure rate contributions derived from the above will also depend upon the mechanical complexity of the hybrid device as a whole and the screening process to which it is subjected during manufacture. Therefore, the failure rates are adjusted finally by a density factor, KB, and a quality factor, KQ.
From the above considerations, the predicted failure rate (λp) of a hybrid microelectronic device is given by the expression:
Where:
λp= The predicted operational failure rate (in failures/106) of a hybrid microelectronic device under stated environmental and operating conditions.
NC= The number of discrete components or integrated circuits of a particular type.
λC= The operational failure rate of the particular discrete component (Table A-2 through Table A-35) or integrated circuit (Table A-38 through Table A-47).
KG= The die correction factor appropriate to the particular discrete component or integrated circuit (Table A-48).
Nr= The number of chip or substrate resistors.
NI= The number of interconnections of a particular type.
λI= The base failure rate of the particular type of interconnection depending upon the package temperature (Table A-50).
λS= The base failure rate of the hybrid package depending upon the package temperature and seal perimeter (Table A-51).
KQ= The quality factor appropriate to the screening level under which the device is procured (Table A-54).