A challenge many engineers face every day is how to prevent the intrusion or leakage of moisture or gases while simultaneously enabling electrical or optical signal transmission. Extremely sensitive electronics and electrical systems, opto-electronic components, and electro-chemical substances need to be protected against environmental influences especially harmful moisture and gases.
The best protection – a closed metal housing – is usually not a viable solution because electrical power and signals must be able to pass through (into and out of) the sealed enclosure. Technology known as hermetic sealing and packaging has been used for decades to enable signal transmission while remaining water- and air-/gas-tight. Hermetic seals can come in the form of electrical housings, (cable) feedthroughs, connectors or penetrators, headers, or conductor terminals. Hermetic sealing is also used for optical signal transmission, for example by encapsulating a sensor and capping it with a reliably vacuum-tight optical lens or window cap.