An analysis of electrostatic discharge considerations in the use of sodium bicarbonate media for de-potting sensitive electronic assemblies.

Sodium bicarbonate blast media offers superior performance in removing low-to-medium density polyurethane foam potting materials from electronic assemblies compared to conventional abrasive or other low-hardness blast media. This work identifies a class of processing equipment suitable for potting removal in electronic assemblies and provides a technical evaluation of appropriate process controls that significantly reduce the potential for Electrostatic Discharge (ESD) degradation or damage. Once appropriate process controls are added, the class of blast equipment demonstrated here, previously used only for non-ESD sensitive assemblies, can be safely used to provide new capabilities for component-level support. In many cases, assemblies that have been de-potted using sodium bicarbonate can be disassembled and rebuilt using normal production processes, enabling repair, reacceptance, and surveillance of assemblies that was previously impractical. This paper presents the results of a study that identifies significant process variables and their contribution to ESD generation. Data are presented to quantify process-related peak ESD voltages and mitigation methods. A discussion of how to implement practical ESD controls and de-potting process test methodologies is provided. The intent of this work is to document foundational experimental work that provides a technical basis for sodium bicarbonate as an ESD-safe material for use in de-potting processes when appropriate controls are implemented.