High-Temperature Component Evaluation of Commercial Flash Memory and Capacitors for Enhancement of Geothermal Tool Development

Abstract

Environments relevant to geothermal energy exploration frequently exceed the temperatures and pressures commonly experienced by downhole tools in the oil and gas industry. As such, pushing the boundaries with geothermal tool development can often necessitate exceeding manufacturer specifications for temperature and pressure of individual circuit components. High-temperature circuit designers often must dedicate considerable time and resources to determine if a component exists that they may be able to knead performance out of to meet their requirements. In light of this difficulty, Sandia National Laboratories has initiated a program funded by the Geothermal Technologies Office at the US Department of Energy to compile and make available an empirically determined, practical dataset of select high-temperature component performances beyond specification. Detailed here are the efforts surrounding geothermal temperature characterization of commercially available HT-Flash memory modules made by Texas Instruments (SM28VLT32-HT) and preliminary results of 3 commercial solid tantalum capacitors. Flash evaluation boards were modified for high temperature application and read, write and erase functionality were tracked as well as prolonged data retention at various temperatures well beyond datasheet specifications. It was observed that each flash function has a different maximum operation temperature above specification. As temperature increases, erase, write, and then read functions successively fail. Within duration and temperature limits, functionality of each operation returns after cooling back below its threshold value. Importantly for logging tools, after cooling the flash modules in this study still retain all memory previously written. Flash lifetime at temperature was examined at several temperatures by 1000hr duration tests in the oven with new writes and periodic full memory reads throughout the test. To test the capacitors, capacitance and equivalent series resistance were tracked over a 1000hr test at 260°C. Results of MatLab fault analyses are described for each aspect of this study to facilitate out-of-spec high temperature tool design.