Feature: Semiconductors
Depending on the nature of the IC, Equation 2 can vary. For example,
when it’s an analogue IC with an extended range of operating voltage, Equation 2 can be used. For all other analogue ICs with fixed operating voltage, the voltage dependence factor will be set to 1. For digital CMOS-B families, the driſt sensitivity factor will be set to 1. Lastly, both voltage dependence and driſt sensitivity factors will be set to 1 for all other ICs. Note that the IEC 61709 standard provides information on how to
translate a reliability prediction from one set of conditions to another and appears to be the theory behind the SN 29500.
What Is IEC Technical Report 62380: 2004? IEC 62380 is another commonly used standard for estimating the failure rate of an IC. It was published in 2004 and was subsequently replaced by the IEC 61709. Despite this, the IEC 62380 standard is still used as a reference in the automotive functional safety standard ISO 26262:2018 as it is still available in the eleventh part as a model for reliability prediction of electronic components. Tis standard calculates the failure rate of an IC as a sum of the die,
package, and EOS. Te expression of FIT calculation according to IEC TR 62380 and ISO 26262-11:2018 is shown in Equation 3.
Where: • λdie is the die failure rate that contains parameters related to the number of transistors, IC’s family and technology used, and mission profile data such as temperature, working time, and influence factor of annual cycles
• λpackage is the package failure rate that contains parameters related to the thermal factor, thermal expansion, mission profile’s temperature factor of cycle, and IC’s packaging
• λoverstress is the overstress failure rate that has corresponding terms for different external interfaces
Failure Rates in ADI’s Safety Application Notes Aside from the reliability data that can be found at
analog.com, the reliability prediction of components for ADI can also be found in an IC’s safety application note, which is typically available when an IC is tagged as FS-enabled. For instance, the LTC2933’s safety application note shows the part’s FIT values derived from HTOL, SN 29500, and IEC 62380 reliability prediction methods. Tis can be seen in Figure 4, Figure 5 and Figure 6. Te tables shown in the figures display the FIT values alongside the conditions considered. System integrators can use available information under the tables to calculate the FIT by themselves if they have different conditions.
Figure 6: FIT based on the IEC 62380 according to the LTC2933 safety application note
Conclusion This article provides an overview of the three most common reliability prediction techniques for integrated circuits, namely the Arrhenius HTOL, SN 29500, and IEC 62380. A calculation based on the Arrhenius formula utilising the
data from HTOL testing provides the failure rate in FIT. SN 29500 provides a reference failure rate as well as conversion models to consider different stress operating conditions. IEC 62380 provides the failure rate of electronic components as the sum of the die failure rate, package failure rate and overstress failure rates. For ADI, failure rates of components can either be found at
analog.com or in a component’s safety application note. The advantage of the safety application note is that it provides a component’s reliability predictions based on the three methods discussed. On top of this, the information needed to calculate such
FIT values is made available so that system integrators can redo the calculations for themselves if they have different operating conditions.
Figure 4: FIT based on the Arrhenius HTOL according to the LTC2933 safety application note
Analog Devices:
www.analog.com
Figure 5: FIT based on the SN 29500 according to the LTC2933 safety application note
www.electronicsworld.co.uk June 2025 31
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