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Introduction To Hermetic And Non-Hermetic Packaging Of Optical Modules

Time: 2024-01-05
1. Overview
        The difference between hermetic and non-hermetic packaging of optical modules mainly lies in the packaging method applied in optical chip packaging—specifically, whether the light-emitting semiconductor chips and optical detectors are installed in a sealed cavity.
2. Hermetic Packaging
        Hermetic packaging for optical modules generally refers to enclosing optical chips (such as VCSEL, FP, DFB, PD, and APD) in a sealed cavity, which is filled with inert gas for protection. It physically isolates the optical chips from moisture, oxygen, and other corrosive gases or liquids, thereby improving the product’s environmental adaptability and reliability.
        This hermetic packaging is more suitable for environments prone to water vapor corrosion and large temperature fluctuations.
        Common hermetic packaging forms for optical chips in optical modules include TO-CAN and BOX packaging. The following figure shows a schematic diagram of the TO-CAN packaging structure:
TO-CAN package BOSA optical components
Figure 1 TO-CAN Packaged BOSA Optical Component
3. Non-Hermetic Packaging
        Non-hermetic packaging is an optical module manufacturing process where optical chips are not sealed. It usually offers a better cost advantage. Common processes include COB (Chip on Board) and COC (Chip on Chip).
        In application, the optical chips are directly exposed to air and only rely on their own oxidation resistance capability against moisture and other gases, making them more vulnerable to external environment influences. Therefore, non-hermetic modules are mostly used inside data center equipment rooms with constant temperature and humidity.
Non-Hermetic COB Packaged QSFP Product
Figure 2 Non-Hermetic COB Packaged QSFP Product
        The choice between hermetic and non-hermetic packaging for optical modules mainly depends on the evaluation of the operating environment and cost budget.
        For higher reliability and environmental adaptability, hermetically packaged optical modules are generally preferred. For cost-sensitive applications deployed inside equipment rooms, non-hermetic optical modules can also be selected.
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