Designs of ultra-HPHT Electrical Component Packages for Downhole and Geothermal Wellbore Logging Tool Integrations

Abstract

Conventional dielectric sealing materials (PEEK, glass and glass-ceramic) used for sealing electrical feedthroughs, connectors, interconnectors and bulkheads in electronic packages can provide reliable downhole wellbore long-term logging tool service up to 150C or short-term logging service for greater than/equal 200C, due primarily to low glass transition temperature of the used sealing materials. This paper will demonstrate that the maximum allowable operating pressure and temperature could be from 20KSI to 100KSI and from 200C to 400C with Borosilicate and Bismuth-Boron-Silica (XTS) sealing glasses. Borosilicate glass sealed Inconel-Kovar/Kovar electronic housing could maintain reliability up to the maximum pressures of ~35KSI at 200C or 25KSI at 400C. Similarly, a Bismuth-Boron-Silica XTS glass sealed stainless steel electronic package housing could have a maximum operating pressure of ~100KSI at 150C or ~50KSI at 300C temperature. It has been found that high glass transition temperatures of (440-560)C for Borosilicate glass and (44010)C for Bismuth-Boron-Silicate (XTS) glass are key for making highly reliable ultra-HPHT electronic component packages. It is shown that the tetrahedral diamond-like microstructures of these sealing glasses are keys to ensure water-repelling properties to maintain sufficient electrical insulation resistance regardless of their use in water or moisture-rich wellbores. Moreover, compressive pin stress is found to be additional key for mitigate frequently observed glass seal cracks during logging tool field services.