From Prototype to Production: Scaling Processes for Hermetic Packages

Prototypes prove feasibility; production proves reliability and cost. Moving hermetic packages from bench builds to repeatable volume runs requires disciplined choices in materials, seals, tooling, test depth, and documentation. Here is a practical roadmap to scale without losing hermeticity.

Lock the architecture before you lock the process

Early builds often use flexible materials and manual steps that do not scale. Before investing in fixtures or qualifications, freeze the package architecture:

• CTE matching: select alloy and ceramic pairs that tolerate furnace and operating cycles. Kovar with alumina, titanium with titanium feedthroughs, or matched glass systems reduce warpage and leak risk.

• Seal type: choose the production method that best fits the thermal budget and throughput goals. AuSn or AuGe brazing offers robust joints; seam welding excels for metal lids; laser welding adds precision for hybrids.

• Feedthrough strategy: consolidate pin counts and pitches to standard drill, metallization, and inspection capabilities.

Design for manufacturability and yield

Every tenth of a millimeter and every plating micron affects yield. Translate prototype tolerances to factory-friendly numbers:

• Tolerances and flatness: relax noncritical parallelism and surface profiles; specify lid flatness consistent with seam or laser plan.

• Plating stacks: standardize Ni and Au thicknesses across part families; avoid custom thicknesses per variant.

• Lid geometry: prefer planar or gently stepped lids over domed or complex forms that complicate fixtures.

• Window and filter features: modularize optical windows or EMI filters so the base can run without them when not required.

Choose scalable sealing and bakeout recipes

Pilot seals are often hand-tuned. Production demands recipes that survive normal drift.

• Thermal cycles: define soak times, ramp rates, and atmospheres with margins to absorb variability in furnace loading.

• Preform design: specify ring dimensions, seam widths, and fillet targets that are easy to inspect and difficult to bridge.

• Bakeouts: lock duration and temperature for moisture reduction with capacity in mind; longer is not always better if it blocks furnace slots.

Build the right fixtures and prove them statistically

Fixtures convert fragile parts into producible assemblies.

• Purpose-built nests: design braze and weld nests for repeatable alignment, thermal contact, and evacuation paths.

• Gauge and datum strategy: define how critical dimensions are set and measured in-line; keep datums consistent from machining through test.

• MSA and GRR: validate that measurement systems can distinguish good from bad parts, then baseline yields with pilot lots.

Standardize cleanroom and handling practices

Hermeticity fails as often from contamination as from poor joints.

• Cleanliness classes: specify minimum cleanroom class for assembly and seal; ensure gowning, solvent controls, and FOD checks are documented.

• Handling media: define gloves, tweezers, and temporary lids; eliminate silicone-based materials near bondable surfaces.

• Dry storage: requires nitrogen or desiccant cabinets with loggable humidity for pre- and post-seal WIP.

Scale the metrology: leak, moisture, and structure

Testing depth should match risk and application, not habit.

• Helium leak testing: set reject limits consistent with mission; define gross and fine leak flows, dwell times, and correlation checks.

• Residual Gas Analysis: specify which lots require RGA and actionable thresholds for water, hydrogen, and hydrocarbons.

• X-ray and visual: define sampling plans for voids in braze seams and lid flatness after sealing.

• Moisture modeling: document accepted models that translate leak rates to internal dew point over service life.

Create a right-sized qualification plan

Scale-up succeeds when reliability evidence travels with the process.

• Process capability: target Cpk values for critical dimensions and leak metrics; require capability before full release.

• Environmental screens: temperature cycling, thermal shock, vibration, and burn-in should reflect the real environment and failure modes.

• Change control: tie recipes, fixtures, and instruments to controlled travelers and work instructions; small changes trigger documented requalification.

Automate where stability beats artistry

Move the most variable steps to semi-automation first.

• Lid placement and tacking: use pick-and-place or pin nests to control position prior to seam or laser welding.

• Laser programs: standardize path libraries with QR-coded part recipes to eliminate operator programming drift.

• Data capture: log furnace curves, weld power, leak traces, and RGA spectra to a lot database for rapid trend analysis.

Secure the supply chain and capacity model

Beautiful processes fail without materials and machine time.

• Materials: lock dual sources for Kovar, alumina, glass preforms, and plating chemicals; document melt and ceramic grade approvals.

• Lead-time alignment: schedule furnace campaigns, plating runs, and helium mass spec maintenance to match the master production schedule.

• Getters and consumables: manage shelf life and activation profiles; avoid last-minute substitutions that change outgassing.

Cost and learning curve management

Early production is where real unit economics emerge.

• Routing and touch time: map each step with standard times; identify bottlenecks that benefit from parallel nests or additional fixtures.

• Yield Pareto: instrument scrap and rework by cause code; fix the top three before chasing minor defects.

• Lot sizing: optimize between setup amortization and WIP risk; right-size batches to avoid long dwell before leak test.

• Continuous improvement: adopt simple SPC on leak, lid flatness, and seam width; small drifts often precede escapes.

Documentation that scales with audits

Aerospace, defense, medical, and energy customers need traceability.

• Travelers and DHRs: include material certs, furnace records, leak plots, RGA snapshots, and operator sign-offs.

• Training and certification: define operator qualification for seal, test, and inspection; requalify on schedule.

• Configuration control: keep CAD, CAM, and laser programs under revision control; ensure labels and serialization match the traveler.

Pilot to production: a phased playbook

Run an intentional three-phase scale-up:

• Pilot lots: 30 to 100 units that validate fixtures, recipes, and metrology; expect design tweaks and process edits.

• Pre-production lots: hundreds of units with frozen drawings and controlled changes; demonstrate capability indices and screen throughput.

• Production release: formal process FMEA closed, control plan active, capacity plan aligned to demand, and costed BOM frozen.

KPIs that predict success

Track a small set of leading indicators:

• First-pass yield to leak spec

• Average and peak leak rates with standard deviation

• RGA failures per lot

• Rework rate and top three defect causes

• Furnace on-time and utilization

• Cost per unit versus routing standard