Sealing Interface
High-integrity pressure barriers utilize specialized electrical connections to transmit signals across sealed chamber walls without compromising vacuum or pressure integrity. A hermetic feedthrough isolates internal sensor elements from harsh external environments while allowing uninterrupted electrical communication. This device maintains a pressure differential across its boundary, preventing gas migration through the junction.
Material Selection
Ceramic to metal joints and specialized glass seals provide the physical structure required to withstand extreme differential pressures. To ensure the durability of a hermetic feedthrough, the thermal expansion coefficients of the glass or ceramic insulator must closely match those of the metal pin and body. A mismatch in these coefficients leads to mechanical stress during thermal cycling, which causes micro-cracking and subsequent leak paths.
Electrical Transmission
Multi-pin arrangements within a single housing must maintain high insulation resistance under high humidity and elevated temperatures. The conductive pins of a hermetic feedthrough carry electrical signals from internal transducers to external processing units with minimal voltage drop. Designers must evaluate the pin materials for electrical conductivity and resistance to oxidation, particularly in applications where sub-millivolt sensor outputs are measured.
In marine or subsea sensing housing assemblies, the feedthrough pins are often gold-plated to prevent contact resistance from degrading the measurement accuracy over long-term deployments.
Leakage Limitation
Standard helium leak detection methods quantify the sealing efficacy of the assembly prior to field installation. A hermetic feedthrough must exhibit a leak rate of less than one times ten to the power of minus nine millibar liters per second to be qualified for ultra-high vacuum or deep submergence sensor installations. Exposure to extreme mechanical shock or thermal shock during deployment can compromise the glass seal, so verification testing is performed after mounting.
