What is BS EN 61709 – Reliability of electric components about?  
BS EN 61709 is an international standard that discusses the reliability of electric components. It is intended for the reliability prediction of electric components as used in equipment and is aimed at organizations that have their own data and describes how to state and use that data in order to perform reliability predictions.
BS EN 61709 gives guidance on the use of failure rate data for reliability prediction of electric components used in equipment.
The stress models described herein are generic and can be used as a basis for conversion of failure rate data given at these reference conditions to actual operating conditions when needed and this simplifies the prediction approach. Conversion of failure rate data is only possible within the specified functional limits of the components.
Note: BS EN 61709 does not provide base failure rates for components – rather it provides models that allow failure rates obtained by other means to be converted from one operating condition to another operating condition.
Who is BS EN 61709 - Reliability of electric components for? 
BS EN 61709 on reference conditions for failure rates and stress models for conversion is useful for: 
- Electronic equipment and component manufacturers
- Electronic engineers
- Product design engineers
- Quality control and testing agencies
Why should you use BS EN 61709 - Reliability of Electric components?  
BS EN 61709 can be used to allow an organization to set up a failure rate database and describe the reference conditions for which field failure rates should be stated. The reference conditions adopted in this document are typical of the majority of applications of components in equipment however when components operate under other conditions the users may consider stating these conditions as their reference conditions.
Using the presented stress models allows extrapolation of failure rates from reference conditions to other operating conditions which in turn permits the prediction of failure rates at the assembly level. This allows estimation of the effect of design changes or changes in the environmental conditions on component reliability. Reliability prediction is most useful in the early design phase of equipment. It can be used, for example, to identify potential reliability problems, the planning of logistic support strategies, and the evaluation of designs.
BS EN 61709 also gives guidance on how a database of component failure data can be constructed to provide failure rates that can be used with the included stress models. Reference conditions for failure rate data are specified, so that data from different sources can be compared on a uniform basis. If failure rate data are given in accordance with BS EN 61709 then additional information on the specified conditions can be dispensed with.
What’s changed since the last update?
BS EN 61709:2017 supersedes BS EN 61709:2011, which is withdrawn. BS EN 61709:2017 includes some technical changes with respect to BS EN 61709:2011. These include: 
- Addition of 4.5 Components choice, 4.6 Reliability growth during the deployment phase of new equipment, 4.7 How to use this document, and of Clause 19 Printed circuit boards (PCB) and Clause 20 Hybrid circuits with respect to IEC TR 62380
- Addition of failure modes of components in Annex A
- Addition of Annex G (former Annex C), Considerations for the design of a database on failure rates, complemented with parts of IEC 60319
- Addition of Annex H, Potential sources of failure rate data and methods of selection
- Addition of Annex J, Presentation of component reliability data, based on IEC 60319
