BS IEC 61586:1997 pdf download – Estimation of the reliability of electrical connectors

BS IEC 61586:1997 pdf download – Estimation of the reliability of electrical connectors.
The reliability of electronic assemblies depends on the reliability of the passive electrical connections between the active components, as well as on the reliability of the components themselves. There is a common perception that interconnections, specifically connectors, are a major source of failures, often of the “no fault found” variety, in electronic assemblies. Whether this perception is true is not the subject of this technical report, but connector reliability is a concern. Much of the increasing attention being given to reliability of electrical connectors focuses on the basic question of how the reliability of electrical contacts and connectors can be meaningfully determined.
The definition of reliability which will be assumed in this report. is the following:
the probability of a product performing a specific function under defined operating conditions for a specified period of time.
Some factors which are to be taken into account in addressing this definition are the subject of this report. The reliability assessment methodology to he discussed centres on appropriate statistical analysis of test data, based on proper consideration of the following issues.
a) The active degradation mechanisms are to be identified and categorized by their importance for the application.
b) Appropriate environmental tests, with corresponding acceleration factors and exposures, are to be determined for these degradation mechanisms.
c) The statistical approach to estimating reliability from the test data is to be agreed upon.
d) An acceptance criterion appropriate for the application of interest is to he established.
Items a) and b) relate to the ability of the product to continue to perform its designated function under the degradation mechanisms it is subjected to in its operating environment. In addition, the need for an acceleration factor is fundamental to assessing the operating life of the product.
Item c) is necessary, since the reliability definition is based on probability which requires statistical treatment of appropriate data.
Finally, item d) reflects that fact that the reliability to be assessed is based on the product performing a defined function.
a) the connector manufacturing process;
b) assembly/application procedures of the
equipment manufacturer;
c) abuse/misuse of the equipment by the end user. While the importance of these application or extrinsic factors cannot be denied, and may well be the determinants of connector reliability, they are highly variable and, therefore, difficult to account for in any estimation of reliability. For that reason, this report. will focus on intrinsic connector reliability, the reliability of the design/materials of the connector itself as evaluated by the procedures listed previously. This intrinsic reliability represents the greatest reliability which the connector can achieve; extrinsic factors will result in a reduction in reliability.
It is also to be noted that the approach to reliability estimation in this report differs significantly from that based on a base failure rate which is modified by application-specific factors as. for example, in IEC 863 or MIL Handbook 217.
rrhe two approaches are related in that the base failure rate could be determined by a different statistical treatment from the same data which are used in assessing reliability by the method to be discussed. The test environments and exposures would determine the standard conditions which are defined for the base failure rate. In addition, the derating factors used in the failure rate approach can. in principle, be derived from the same data used to determine acceleration factors in the proposed statistical method.
The advantage of the approach recommended in this report is that the standard conditions, acceptance criteria, and statistical treatment are specifically defined for the application under consideration. This is in contrast to a base failure rate starting point which is frequently poorly defined and documented.
1 Scope
This technical report deals with the estimation of the reliability of electrical connectors through the definition and development of an appropriate accelerated testing programme. The basic intrinsic degradation mechanisms of connectors are reviewed to provide a context for the development of the desired test programme.