Application Analysis of Hermetic Packaging in the Sensor Field

1. Why Do Sensors Need Hermetic Packaging?

Sensors are the “eyes” that perceive physical quantities. But sensor chips are extremely sensitive to their environment — moisture causes MEMS movable parts to stick, and corrosive gases make infrared detector chips drift.

Hermetic packaging solves three core problems:

First, it blocks moisture and corrosive gases to protect the chip’s long-term stability.

Second, it provides a stable internal atmosphere — some sensors must be filled with high-purity nitrogen or inert gas, and only hermetic packaging keeps that internal atmosphere unchanged.

Third, it provides electrical feedthroughs — the feedthrough structure carries sensor signals from inside the sealed cavity to the outside without compromising hermeticity.

Typical scenarios: automotive intake-pressure sensors exposed to hot oil mist in the engine compartment; industrial gas sensors in contact with corrosive gases such as hydrogen sulfide; downhole pressure sensors working in high-temperature, high-pressure environments — none of these can do without hermetic packaging.

2. Typical Sensor Packaging Solutions

Different sensors call for different solutions:

Low-pressure sensors (e.g., tire-pressure monitoring) — GTMS solution: Kovar housing + borosilicate glass insulator; controllable cost, suited to high-volume automotive electronics.

High-temperature sensors (e.g., exhaust-gas temperature sensors) — CTMS solution: Al₂O₃ ceramic, high-temperature resistant and able to withstand the engine exhaust environment.

Infrared detectors — CTMS solution: the ceramic substrate provides high-conductivity heat dissipation, and brazing ensures highly reliable hermeticity.

Selection criteria: look at the temperature, the volume and the medium. The higher the temperature and the harsher the environment, the more CTMS is favored; the larger the batch and the more cost-sensitive the application, the more GTMS is favored.

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[Glossary]

1. MEMS (Micro-Electromechanical Systems): micro-electromechanical systems — miniature devices that integrate mechanical structures and electronic circuits on a chip

2. Hermetic Feedthrough: a hermetic packaging structure in which metal pins pass through the metal housing, insulated by glass or ceramic