Hermetic Package Sealing

Low-Void Seals That Protect Critical Circuits

Hermetic package sealing uses solder or glass frit to isolate critical microelectronic circuits from the surrounding environment. Hermetic packages are usually ceramic or metal, sealed with a metal solder or solder-glass joint that keeps moisture and other corrosive contaminants from damaging components and wire bond connections.

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What a Reliable Hermetic Seal Requires

A hermetic seal must have zero breaks. In practice, that means extremely low voiding, with no single void or collection of voids larger than the seal width anywhere in the seal. Component placement matters too: any placement offset reduces overall seal volume and seal integrity, raising the risk of hermetic seal failure.

Tooling is just as important. Precision-manufactured fixtures hold the components in their designated locations during sealing, while free-floating weights apply constant pressure to the seal area, helping ensure a hermetic interface between the lid and the package.

Preventing Voids and Oxides in Hermetic Package Sealing

Purpose-built thermal profiles use positive inert gas pressure to minimize voids in the finished seal. Oxygen is repeatedly pumped out of the system, then backfilled with dry inert gas, to prevent oxide formation.

Voids often come from gas trapped during package and component fabrication. Pressure variation during the sealing cycle helps reduce these voids, and Palomar vacuum reflow systems combine it with precise thermal and atmosphere control to create robust hermetic seals.