Overview

Hermetic lid etching uses photochemical machining to produce flat sealing closures for packages that must stay airtight over years of service. The lid outline, sealing groove, weld ring and any step features are imaged onto a photoresist mask, developed, and the unprotected metal is dissolved in an alloy-matched etchant. Because the metal is removed chemically rather than stamped, the lid emerges flat and burr-free, with no edge roll-over or residual stress on the surfaces that will be seam-welded, soldered or laser-sealed — and the process runs equally well in Kovar, stainless steel 304/316L and titanium.

The value of hermetic lid etching lies in the sealing groove, a recessed channel that seats a solder preform or weld ring and locates the lid on the package wall. Etching forms this groove with a controlled depth and a straight, square bottom, which a stamping die cannot hold at thin gauges without distortion. The same process keeps the lid flat enough for a uniform seal ring, and it allows vent holes, alignment notches and internal steps to be added at near-zero incremental cost. For packages that must pass gross and fine leak testing, this combination of flatness, clean edges and repeatable groove geometry is what makes the seal dependable.

Parameter Window

• Available Materials: Kovar (ASTM F-15), stainless steel 304/316L, titanium, Alloy 42
• Material Thickness Range: 0.1–0.6 mm
• Tolerance: ±0.03 mm on outline, ±0.02 mm on groove depth and width
• Minimum Feature: 0.1 mm line width, 0.2 mm sealing groove, 0.3 mm vent hole at 0.25 mm stock
• Surface Options: electrolytic nickel, nickel/gold, gold plating, passivation, bare alloy
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Drawing Review — Convert package drawings to vector artwork, check groove width and depth against stock thickness, and lock outline and step calls.
2. Material Selection — Choose Kovar for glass/ceramic-matched seals, 304/316L for corrosion resistance, titanium for light weight; confirm grade and temper.
3. Cleaning & Lamination — Degrease the sheet and laminate dry film resist so no bubbles sit under the sealing groove or weld ring.
4. UV Exposure — Expose through high-resolution film with the artwork registered to the sheet edge for panel-level accuracy.
5. Development — Wash out unexposed resist to open the groove, outline and vent features, then inspect for under-developed edges.
6. Etching — Spray-etch in alloy-matched chemistry; groove depth and sidewall straightness are set by time, temperature and conveyor speed.
7. Stripping & Finishing — Remove resist, neutralize, then plate nickel, nickel/gold or passivate; stress-relief anneal restores flatness where required.
8. Inspection & Packaging — Verify flatness, groove depth and width, edge quality and plating against the approved sample, then pack in trays or waffle packs.

Core Advantages

1. Controlled sealing groove: Etching forms the groove with a consistent depth and square bottom, so the solder preform or weld ring seats evenly.
2. Flat and burr-free: Chemical removal leaves no dishing, curl or edge roll-over, so the lid forms a uniform seal ring on the package wall.
3. Multi-alloy capability: Kovar, stainless 304/316L and titanium run on the same line, letting one design span several package families.
4. Clean weld and solder surfaces: Nickel, nickel/gold and passivation finishes give a wettable, oxidation-free surface for sealing.
5. Fine vent and alignment features: Vent holes and alignment notches hold at 0.2–0.3 mm without distortion.
6. Tooling-free changes: Each lid shape is a new film, so groove and outline revisions happen in hours — hermetic lid etching stays economical through every design change.

Typical Applications

• Sealed sensor packages: Lids with sealing grooves for pressure, gas and inertial sensors that must hold vacuum or inert gas.
• Crystal and oscillator packages: Flat closures for quartz crystal and oscillator packages sealed by seam welding.
• MEMS and optoelectronic packages: Lids with vent and window features for MEMS and optoelectronic devices.
• Hybrid and RF module lids: Covers for hybrid microcircuit and RF module packages with matched expansion.
• Medical implant housings: Titanium lids for implantable device housings requiring biocompatibility and hermeticity.
• Aerospace relay and switch lids: Stainless and Kovar closures for hermetically sealed relays and switches.

Design Notes & Process Considerations

1. Groove depth and width: Call out the sealing groove depth and width separately, since they set how the preform or weld ring seats; typically ±10% of stock.
2. Flatness requirement: State flatness per 10 mm, since a dished or curled lid cannot produce a uniform seal ring.
3. Material versus CTE: Match the lid alloy to the package body; Kovar for glass/ceramic, 304/316L for metal bodies, titanium for light weight.
4. Vent hole placement: Keep vent holes at least 0.3 mm and away from the seal land, or they will weaken the joint and complicate leak testing.
5. Plating specification: Name the plating and thickness; gold over nickel is common where wire bonding or soldering follows sealing.
6. Panel layout: Group lids on one sheet with shared registration marks to reduce handling and keep unit cost down while preserving groove quality.