Recommended Practice for Reliability Physics Analysis of Electronic Equipment, Modules and Components
This Recommended Practice describes a standard process for Reliability Physics Analysis (RPA1) for Electrical, Electronic, and Electromechanical (EEE) equipment, modules, and components used in the Automotive, Aerospace, Defense and other High-Performance (AADHP) industries
The AADHP industries are characterized by long lifetimes, rugged operating environments, and stringent safety and reliability requirements. It is critical to address these requirements by
1. Assembling the best available information, technical capability, and other resources;
2. Developing consensus among the industry stakeholders on the best way to address the issues;
3. Incorporating the results in consensus industry standards that are available to all.
This proposed document is a result of that approach.
RPA is a modern, science-based approach for reliability optimization, failure risk assessments and risk elimination achieved through the use of Computer Aided Engineering (CAE) durability simulation of EEE devices. RPA durability simulation combines stress analysis of usage and environmental conditions with EEE failure mechanism models produced and validated relevant research and data.
RPA leverages scientific understanding of the mechanisms that cause failure in EEE equipment, modules, and components; to assess their capability to perform their intended functions safely and reliably throughout their lifetimes. RPA is based on data acquired from relevant research, field experience and/or credible, relevant testing. It employs Finite Element Analysis (FEA) to quantify the relevant stresses on an item, and simulate its performance in the expected operating environments. RPA also uses mathematical modeling to quantify the factors that accelerate failures, and estimate times-to-failure risks over the EEE equipment’s expected lifetimes. RPA is facilitated by the use of CAE methods to perform a durability simulation that identifies reliability performance or failure risk over the service life of EEE equipment.
While RPA is technically complex, its implementation has become practical through ongoing advancements and availability of computing power, and the ease-of-use provided by CAE application programs that has facilitated its use. As its use proliferates, RPA is being conducted in a variety of ways; and its results are being reported and used in variety of ways; and the potential for confusion is increasing. To satisfy their needs for safety and reliability, the AADHP industries propose this recommended practice document to develop industry consensus on the best “standard” process for RPA. This consensus is broadened by cooperation among industries, including automotive and aerospace, to develop, maintain, and apply the RPA process to be described in this document.
The basic steps and models of the RPA process are applicable to EEE technologies used in all AADHP industries, however, their implementation may vary according to products, operating conditions durability service lifetimes, and environments. Therefore, this document describes the baseline RPA process, and a series of appendices or other sub-documents will describe its implementation in a range of specific circumstances.This document is not intended to be a mandatory list of tasks to be performed, tests to be conducted, or data to be reported, for every application in every program. Nor is it intended to mandate sophisticated high-end CAE simulations for situations when more basic calculation techniques will suffice. This document lists the basic steps to be taken to produce a credible RPA, whose results can be applied in a variety of ways to produce functional, safe, and reliable products, which can be designed, developed, validated, and, if necessary, certified effectively and efficiently.
This document is applicable to all hardware components of an EEE system. It is applicable to failure mechanisms that result from degradation of materials or accumulated damage to components, that impact the functional outputs of an EEE system based on the material science principle of stress driven damage accumulation in materials. It is not applicable to failures caused by design errors or misuse of the system; nor is it applicable to software.
1 RPA is also called physics-of-failure (PoF) analysis, but RPA is used here because it more accurately represents the intent of the process.
Rationale: The AADHP industries depend on an increasing number of highly sophisticated embedded EEE equipment, modules and components to perform essential safety critical functions. This requires the EEE devices to be highly reliable and durable. RPA durability simulations are a state-of-the art approach that adds the ability to achieve EEE reliability-durability objectives via design analysis methods, similar to basic stress analysis methods applied in mechanical and structural engineering. This capability to design in reliability accelerates product development and reduce dependence on costly prototype testing.
The AADHP industries need a realistic, state-of-the-art RPA process that improves upon traditional, actuarial-based reliability prediction methods. The traditional methods are based on compressing complex failure histories into simplified generic averages, represented by constant, lifelong, averaged failure rates. Those traditional methods have been shown to be simplistic, and inadequate for today’s highly complex and technically sophisticated EEE products that, in high-stress long-life applications, are susceptible to wearout mechanisms as they age. Furthermore, the years of field data required for those historic failure rate methods are not readily available in a timely manner for use in new designs as EEE technology and components evolve rapidly. The AADHP communities have been moving away from these actuarial methods for at least two decades.
In the automotive industry, the release of the Vehicle System Functional Safety Standard, ISO-26262-2011, required safety risk assessments to be performed using the widely discredited actuarial probabilistic methods mentioned above. To address concerns regarding the accuracy of ISO-26262-2011, the SAE AESRSC participated in the publication of ISO-26262-2018, which recognized CAE-based RPA methods as an acceptable method for use in functional safety risk assessments, as an alternative to the actuarial approaches. Therefore, one purposes of this proposed recommended practice is to define an industry-consensus-based standard RPA process, and best practices modeling procedures as an option for use in ISO-26262-2018 functional safety risk assessments.
RPA also addresses the time and costs of developing complex EEE systems and equipment. Development tests (e.g., qualification, reliability, durability, etc.) are expensive and time-consuming. By leveraging advanced computing capability, RPA enables development of EEE systems and equipment with improved safety, reliability and robustness.
Therefore, a primary purpose of this document is to define an AADHP industry-consensus RPA process, accompanied by a series of application-specific appendices (or other sub-documents), that
satisfies the intent of documents such as ISO-26262 (for the automotive industry), and RTCA DO-254 (for aerospace) in a manner that represents the most up-to-date physics-based methods: and is timely, effective, efficient, and most critically, results in safer and more reliable EEE products.
Relationship to Other Standards
This document will align with and reference the following existing SAE standards:
• SAE J1211 - Handbook for Robustness Validation of Automotive Electrical/Electronic Modules
• SAE J1879 - Handbook for Robustness Validation of Semiconductor Devices in Automotive Applications
• SAE J3083 - Reliability Prediction for Automotive Electronics Based On Field Return Data
• SAE J2940 - Use of Model Verification and Validation in Product Reliability and Confidence Assessments
• SAE J2816 - Guide for Reliability Analysis Using the Physics-of-Failure Process
• SAE ARP6338, Process for Assessment & Mitigation of Early Wearout of Life-limited Microcircuits.
• SAE ARP6379, Processes for Application-Specific Qualification of Electrical, Electronic, and Electromechanical Parts and Sub-Assemblies for Use in Aerospace, Defense, and High Performance Systems
It is also intended that the team that develops this standard will cooperate with SAE to develop aerospace and automotive versions of new SAE professional development training classes to teach the RPA process.
This document satisfies 5 of SAE’s reasons for producing a new standard:
• Create common language - YES
• Enhance safety - YES
• Facilitate trade through reduced regulations - NO
• Harmonize global markets - POSSIBLY
• Improve the environment - NO
• Increase productivity of processes – YES
• Permit common interfaces - NO
• Promote uniform testing or performance - YES
• Reduce costs – YES