Electrothermal event refers to abnormal temperature increase leading to malfunction or catastrophic fails. The high temperature reached during such event activates or initiates some of the failure mechanism explained before, such as the growth of insulation oxide layers and outgassing processes responsible for organic contamination. Besides the formation of nonconductive layers at the contact interface, high temperature can also cause the degradation of plastic insulators and contribute to multiple short-circuit conditions.
Electrothermal events can be related to:
- Sustained overload conditions lead to high operating temperatures for long periods of time.
- Arcing due to the loose of connection at the contact interface during mechanical vibration.
- Transient short circuit conditions result in localized hot spots.
It also worth to mentioning here the interplay between electrothermal events and corrosion in constant-current biased systems. In those systems corrosion product at the contact interface increase the system resistance and therefore the dissipated power, which in turn accelerates the corrosion rate (electrothermal feedback).
Diagnosis
Prolonged operation under high temperatures lead to connector discoloration noticeable by visual inspection. Early hot spot detection is conducted by IR thermography which has been proved to be a useful tool to prevent temperature driven failures in crimped systems as well as to assess the crimping quality.6 In addition, these techniques are used to study transient electrothermal events.
Failures in crimped connectors can be can be related to different causes, some of the discussed elsewhere. The present post analyzes those related to electrothermal events.
References
1. Electronics Engineer’s Reference Book, Butterworth International Edition, Ed. L. W. Turner
2. Electronic Failure Analysis Handbook, McGraw-Hill, Pierry L Martin.
3. RADC-TR-78-15 Air Force Systems Command.
4. Materials and Processes for Spacecraft and High-Reliability Applications, Springer, Barrie D. Dunn.
5. Identification of corrosion and damage mechanisms by using scanning electron microscopy and energy-dispersive X-ray microanalysis: contribution to failure analysis case histories, IOP Conf. Ser.: Mater. Sci. Eng. 55 012015, G Pantazopoulos and A Vazdirvanidis
6. Use of Thermography and Ultrasonic Inspection for Evaluation of Crimped Wire Connection Quality, 18th World Conference on Nondestructive Testing; Matej FINC, Tomaž KEK, Janez GRUM.
*Are included all “Improper degree of compression in Crimped Connectors”, “Corrosion/Contamination in Crimped Connectors” and “ Electrothermal events Crimped Connectors”