Seam sealing is a precision resistance-welding process used to hermetically join a package lid to its seal ring. Both the cover and seal ring are typically fabricated from Kovar™ and finished with nickel and gold plating to ensure excellent weldability and corrosion resistance. During the process, two rotating conical electrodes roll along the package perimeter, applying controlled pressure and electrical current. The resulting overlapping spot welds form a continuous, gas-tight joint that meets stringent hermeticity standards.

This method offers several key advantages:

• Low thermal stress: The controlled I²R heating minimizes heat transfer to feedthroughs and internal devices, protecting sensitive circuits.

• Atmosphere control: Sealing is performed in a dry nitrogen or inert environment following deep vacuum bake moisture removal, maintaining a pristine internal atmosphere with sub-ppm H₂O and O₂ levels.

• No forming gas required: Seam welding achieves hermeticity without additional reducing gases, simplifying process control and equipment maintenance.

• Visual process control: The weld line is fully visible during sealing, requiring no complex fixturing or mechanical clamping.

Si-Craft’s seam weld sealing process provides the lowest temperature hermetic seal achievable for metal and ceramic packages, ensuring ultra-low leak rates and compliance with MIL-STD-883 Method 1014 and MIL-STD-750 requirements. The process supports both prototype and high-volume production, with throughput capability of several thousand packages per hour.

Seam Sealing via Resistent Welding

Seam Sealing With AuSn Solder Pre-Form Lid

Seam AuSn solder sealing is a precision resistance heating process used to join a Kovar™ lid to a thick-film seal ring on the package substrate. Both interfaces feature 1.27 µm gold over 5 µm nickel plating, ensuring superior solder wetting and bond integrity. The 80Au/20Sn eutectic solder provides excellent hermeticity with moderate fluidity when molten, forming a uniform, gas-tight joint without the use of forming gas. For manufacturing efficiency, solder preforms are pre-tacked to the lid prior to assembly.

During sealing, the lid is positioned on the seal ring—requiring only gravity for alignment—while opposing conical electrodes roll along the package perimeter. Controlled I²R heating melts the solder, bonding the gold–nickel surfaces and forming a continuous hermetic seal. The process requires no complex fixtures and allows direct visual monitoring throughout the seal.

Seam AuSn solder sealing delivers:

• Low thermal stress to internal components, minimizing heat exposure during bonding.

• Tight atmosphere control, performed in a dry inert environment after deep vacuum moisture removal.

• Fine leak performance, typically within one decade of welded seam hermeticity.

• Exceptional cleanliness, with sub-ppm H₂O and O₂ levels and 0.1 µ particulate filtration.

Compared to conventional oven or belt-furnace soldering, Si-Craft’s seam AuSn process offers the lowest device temperature exposure, minimal solder voiding, and outstanding microcircuit atmosphere integrity. The process exceeds MIL-STD-883 and MIL-STD-750 hermeticity standards and supports both prototype and high-volume production, accommodating several hundred packages per hour.

For ultra-small packages, our optimized solder control ensures void-free seals and robust mechanical strength even with narrow seal ring geometries—preventing trapped gases and maintaining the purity of the sealed cavity environment.

Hematic Sealing Via Laser Welding

Si-Craft Technologies offers high-precision laser welding for hermetic package sealing in semiconductor, MEMS, and optoelectronic applications. Our process uses tightly focused laser energy to achieve clean, localized welds with minimal heat input, ensuring excellent seal integrity and minimal stress to internal devices. Performed in controlled inert atmospheres with sub-ppm moisture and oxygen levels, Si-Craft’s laser sealing delivers reliable, gas-tight enclosures that meet MIL-STD-883 and MIL-STD-750 requirements. Ideal for hybrid ICs, optical transceivers, and aerospace modules, our laser welding solutions combine process control, cleanliness, and scalability from prototype to high-volume production.

Laser hermetic sealing uses a focused laser beam to weld the package cover to its base, creating a gas-tight closure with minimal thermal impact to internal components. Typically, the package is vacuum-baked and dehydrated prior to sealing; then the laser weld is performed in an inert atmosphere (low H₂O, low O₂, fine-particle filtration) to maintain a pristine internal environment. The extremely narrow heat-affected zone inherent in laser welding protects sensitive internal devices, feed-throughs and materials from thermal damage.

Key benefits of laser hermetic sealing:

• Very low heat input to internal structures — ideal for temperature-sensitive dies or MEMS.

• Ability to join dissimilar materials (e.g., Kovar™, titanium, stainless steel, ceramics) with precision.

• High reliability: excellent protection against moisture and gas ingress, suitable for military, aerospace, medical and high-reliability optoelectronic applications.

• Clean process: the inert atmosphere and pre-bake ensure very low residual moisture/oxygen inside the package.

• Visual and process control: welding stations often include glove boxes or enclosures for controlled atmosphere and monitoring.

At Si-Craft Technologies, our laser hermetic sealing offering is engineered to match the demands of mission-critical devices. We support a range of package materials and geometries, and provide full qualification to standards such as MIL‑STD‑883 and MIL‑STD‑750. Whether you are working on MEMS sensors, optoelectronic modules, or harsh-environment electronics, our laser seal process ensures minimal thermal exposure and maximum long-term reliability.