EN 62005-3-2001 pdf download.Reliability of fibre optic interconnecting devices and passive components Part 3: Relevant tests for evaluating failure modes and failure mechanisms for passive components.
This part of IEC 62005 focuses on failure mechanisms associated with interconnecting devices and passive components. In order to estimate reliability by the acceleration testing described in IEC 62005-2, it is important to determine the dominant failure mechanism and the related test. This part of IEC 62005 introduces a choice of relevant tests from all the IEC 61300 series tests for each known failure mechanism and failure effects related to certain failure modes. (In IEC 62005-5, extension of severity depending on environmental category and performance request will be given.)
2 Choice of relevant tests
Figure 1 shows the guidelines for the choice of relevant tests. At the first stage, relevant tests are selected by considering the device type of passive optical components. Then, at the second stage. relevant tests are refined by considering known failure mechanisms for each device. Each set of relevant tests for a particular device and for a particular known failure mechanism is obtained by this procedure. After that, suitable test conditions should be selected.
3 Typical failure points
A typical passive optical component consists of different parts (the optical element, the package, the pigtail, joints, etc.) as shown in Figure 2. Each passive component exhibits failures that can be referred to these parts and that can be common for a large class of devices: failure mode, failure mechanisms, failure effects; a set of relevant tests is shown in Table 1. Table 2 Is more specific for each device type.
4 Failure modes and known failure mechanisms
For any component under consideration, a potential failure mode and effect analysis (PFMEA) should be carried out. Table 2 shows selected relevant tests by the procedure of Figure 1 for known failure mechanism or failure effects for each type of commercially available and testable devices. It must be emphasized that the list of known failure mechanisms and failure effects is not exhaustive. If new technology and new passive components become commercially available, they should be added to Table 2. Relevant tests are listed with the failure effect and the dominant known failure mechanism. As other relevant tests or methods of failure mode excitation become known, these should also be added In a supplementary table and published.
5 Criteria for the choice of stress conditions — Step stress method
The severity and the duration of the test are the main sensitive points in reliability estimations. The severity indicated for the test by the references is mainly intended for quality evaluation and may be not sufficient for accelerated ageing tests. ‘lnsufficient means that failures or observable degradation may occur in an unacceptably long time (too low acceleration). On the other hand, the use of too high acceleration could result in failure mechanisms that are not typical for the devices in their usual operating environments.
A feasible way to Identify failure mechanisms and to establish bounds for the test severity is the step stress method: a significative sample of devices, possibly after product screening, is aged at an increasing level of stress, starting from the operating conditions. Each testing condition is performed for a relatively short time (for instance 150 h): after that, temperature and/or humidity is increased. The severity increase should be high enough to avoid memory effects (ageing behaviour in one step is independent from ageing in the previous ones) but without causing an atypical failure mechanism (at least at the first steps).
In some cases, the degradation rates are recorded at each step. It is possible to extrapolate a preliminary relationship between degradation with temperature and/or humidity. If the degradation rates of more severe conditions are not consistent with an extrapolated acceleration law, this can also mean that a new failure mechanism has been induced.
The results of step stress testing can be used to corroborate the results of the extended reliability assessment programme. but they cannot be considered as a conclusive reliability evaluation.EN 62005-3-2001 pdf download.