Hermetic Packaging Line

Role in QLT Fabrication

After wire bonding and fiber attachment, the quantum photonic chip must be hermetically sealed inside a butterfly-style or flatpack package. Hermetic sealing is the final critical step that determines whether a device can survive field deployment or remains a lab curiosity. Without it, moisture ingress degrades Si₃N₄ waveguide performance, corrodes TiN heater metallization, and increases SPAD dark count rates — ultimately destroying quantum coherence within weeks to months.

The hermetic packaging line integrates vacuum bakeout, controlled-atmosphere glovebox, seam welding or laser welding, and leak testing into a single process flow. For QLT's quantum photonic processor, hermeticity requirements follow both MIL-STD-883 and Telcordia GR-468-CORE standards, demanding internal moisture levels below 5,000 ppm after 10+ years of sealed operation.

• Moisture protection ● prevents waveguide degradation, metal corrosion, and SPAD dark current increase
• Inert atmosphere ● N₂ or dry air backfill; < 5,000 ppm H₂O per MIL-STD-883
• Long-term reliability ● telecom-grade devices require 20+ year sealed lifetime
• Qualification compliance ● MIL-STD-883 Method 1014 (hermeticity), Method 1010 (temperature cycling)
• Getter integration ● molecular sieve absorbs residual moisture for decades of margin

Why Hermetic (Not Epoxy or Polymer Seal)?

Hermeticity Analysis for QLT Package

MOISTURE INGRESS CALCULATION:

Target: Internal moisture < 5,000 ppm after 10 years
Package volume: ~2 cm³ (14-pin butterfly)
Initial backfill: dry N₂, < 50 ppm H₂O

With standard seam weld (L = 5 × 10⁻⁸ atm·cc/s He):
├── Convert to H₂O: L_H₂O = L × √(M_He/M_H₂O) × P_H₂O_ambient
│   = 5e-8 × 0.47 × 0.012 = 2.8 × 10⁻¹⁰ atm·cc/s
├── After 10 years (3.15 × 10⁸ s):
│   Total H₂O ingress: 2.8e-10 × 3.15e8 = 0.088 atm·cc
│   Internal moisture: 0.088 / 2 cm³ = 44,000 ppm → EXCEEDS SPEC
│
├── SOLUTION 1: Tighter seal (5 × 10⁻⁹ atm·cc/s)
│   Internal moisture after 10 yr: 4,400 ppm → PASS ✓
│
└── SOLUTION 2: Add 5A zeolite getter pellet (1 g)
    ├── Getter capacity: ~200 mg H₂O absorption
    ├── Total moisture ingress over 10 yr: ~3 mg
    ├── Getter covers 66× the ingress → huge margin
    └── RECOMMENDED: include getter in all packages

Technical Specifications

Package and Lid Materials

QLT Package Configurations

Seam Welder Specifications — AMADA SM-8500A

Seam Welding Process Parameters

Process Integration

QLT PROCESS FLOW ● Hermetic Packaging Line (Step 06):

PRE-REQUISITES:
├── Photonic die diced and inspected (dicing saw)
├── Die bonded to package base (die bonder, AuSn reflow 310°C)
├── Wire bonds complete: 48 × Au, 25 μm dia (#08/#31)
├── Fiber attached through hermetic feedthrough (#09)
└── All electrical/optical tests passed before sealing

STEP 1: Pre-Seal Bakeout
├── Load wire-bonded, fiber-attached chips in bakeout oven
├── Temperature: 150°C × 24 hr under vacuum (or dry N₂)
├── Purpose: drive out moisture from package cavity, die attach
│   adhesive, and wire bond pad surfaces
└── SA2200 bakeout oven (or equivalent vacuum oven)

STEP 2: Getter Installation
├── Place 5A zeolite molecular sieve pellet (1 g) inside package
├── Position away from wire bonds and fiber path
├── Getter pre-baked at 300°C × 2 hr to activate
└── Provides 200 mg H₂O absorption capacity (66× margin)

STEP 3: Transfer to Glovebox
├── Move packages into N₂-purged glovebox
├── Atmosphere: < 100 ppm H₂O, < 100 ppm O₂
├── Verify inline moisture/O₂ sensors read within spec
└── Minimize time between bakeout removal and glovebox entry

STEP 4: Lid Placement & Tack Weld
├── Place Au/Ni-plated Kovar lid on package seal ring
├── Gravity hold (no fixture needed for standard butterfly)
├── 4-corner tack welds: lower energy, short pulse
└── Verify lid alignment under stereo microscope

STEP 5: Seam Weld
├── Run parallel seam weld around full perimeter
├── Position-based energy control at corners
├── 70–80% pulse overlap for continuous gas-tight seal
└── Total weld time: ~30 seconds per package

STEP 6: Post-Weld Inspection
├── Visual inspection: check weld bead continuity (10–30×)
├── No gaps, cold welds, or excessive spatter
└── Measure lid planarity (no warping from thermal stress)

STEP 7: Helium Leak Test
├── Per MIL-STD-883 Method 1014
├── Target: < 5 × 10⁻⁸ atm·cc/s (fine leak)
├── Bomb at 3 atm He for 2 hours, then test
└── Reject and rework any unit exceeding leak spec

STEP 8: Moisture Verification (Sample Basis)
├── RGA or FTIR per MIL-STD-883 Method 1018
├── Target: < 5,000 ppm H₂O internal
├── Outsource to qualified test lab
└── 1 per lot minimum; 100% if qualification phase

Vendor Options & Pricing

Seam Welding Systems

Package and Consumables Vendors

Outsource Options (Prototype Phase)

Total System Budget

PHASED PROCUREMENT STRATEGY:

Phase 1 (Prototype): Outsource seam welding
├── 20 units × $100/unit = $2,000
├── Timeline: Month 3–6
└── Alternative: epoxy seal for lab testing (< 1 month life)

Phase 2 (Pre-production): Used system acquisition
├── Used SM-8500 + simple glovebox = $30,000–$50,000
├── Installation (3-phase electrical) = $5,000
├── Timeline: Month 6–12

Phase 3 (Production): Full glovebox line
├── Alpha Series glovebox system = $60,000–$100,000
├── SA2200 bakeout oven = $15,000–$30,000
├── Timeline: Year 2+

═══════════════════════════════════════════
ESTIMATED TOTAL (full line): $1,000,000–$2,000,000
  Includes: seam welder, glovebox, bakeout oven,
  leak tester, package inventory, consumables,
  installation, qualification
═══════════════════════════════════════════

Facility Requirements

Safety & Handling

Consumables & Maintenance