RightsCopyright © International Foundation for Telemetering
Collection InformationProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection.
AbstractSolder joint cracking has occurred in assemblies where discrete part subassemblies are fabricated on Printed Circuit Boards and conformal coating is applied to the sub-assembly. The objective of the investigation were to determine the extent and seriousness of the problem, to determine the cracking mechanism, and to provide engineering and process information to eliminate the problem. The analysis and test results indicate that many factors influence the strength of a solder joint and the ultimate crack that develops. Contamination by gold products and other foreign materials can significantly affect solder characteristics. Aging and temperatures experienced in the normal operating range of certain equipment adversely affects the strength of the solder materials. Conformal coating between the discrete part and the Printed Circuit Board is a major contributor to the cracking mechanism. Transistor assemblies using a Spacer under the TO-5 enclosure with Kovar Lead Material and completely covered with conformal coating have a high incidence of cracked solder joints. This condition is caused by the mis-match of coefficients of expansion between the Kovar Lead and the conformal coating.
SponsorsInternational Foundation for Telemetering