Overview

An OEM lead frame for wearable devices is produced by photo chemical etching, which forms fine lead fingers, die pads and locating holes out of a full metal foil in one chemical step instead of by stamping or laser cutting. Dry-film resist is laminated to both faces, the lead pattern is exposed and developed through high-resolution film, and the unprotected alloy is dissolved in a matched etchant, so fine-pitch leads, half-etched steps and lock holes all form together. Because removal is chemical rather than mechanical, the frame stays flat and burr-free with no work hardening or residual stress, preserving the coplanarity that die attach, wire bonding and surface mounting depend on in thin wearable packages.

For packaging and design engineers, this precision etching process addresses three limits of conventional methods in miniaturized wearables: stamping tooling is costly and slow to revise across fast-changing part numbers, and it leaves roll-over and stress on thin lead fingers that hurt coplanarity; laser cutting adds heat tint on copper alloys; and machining struggles to form die-pad recesses, lock holes and local thinning in one pass. Because the geometry lives in the film, a new part number is only a new artwork, and every frame on a sheet etches at the same rate, so lead width, step depth and edge quality stay consistent from first sample to volume production.

Parameter Window

• Available Materials: C19400/C7025 copper alloy, Kovar (Fe-Ni), Alloy 42, 316L stainless steel, nickel-iron clad foil
• Material Thickness Range: 0.10–0.50 mm foil, with half-etched steps and die-pad recesses
• Tolerance: ±0.02 mm on lead finger and outline, ±0.03 mm on die-pad position
• Minimum Feature: 0.08 mm lead width and 0.08 mm pitch, half-etch depth from 0.03 mm
• Surface Options: silver, nickel, NiPdAu plating, anti-tarnish coating for bonding and solderability
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Convert customer 2D files to vector outlines, check lead width, pitch and half-etch zones, and lock die-pad positions.
2. Material Prep — Select copper alloy or Kovar foil by bonding and molding method, shear to panel size, and inspect for surface scratches.
3. Cleaning & Lamination — Degrease and de-oxidize, then hot-roll dry film onto both faces with pressure matched to foil thickness so no bubbles sit under fine leads.
4. UV Exposure — Expose both sides through high-resolution film with front-to-back registration so lead fingers stay concentric with die pads.
5. Development — Wash away unexposed resist to open the alloy to be removed, and rework any fine lead still showing residual resist.
6. Etching — Spray chemistry matched to the alloy; time, temperature and conveyor speed govern the precision etching process, sidewall and half-etch depth across the panel.
7. Stripping & Finishing — Remove resist and neutralize, then apply silver or nickel plating, cut the dambars, and anneal for flatness where coplanarity demands it.
8. Inspection & Packaging — Verify lead width, coplanarity and plating against the approved sample, then pack in tape-and-reel or trays with first-article measurements.

Core Advantages

1. Panel-level coplanarity, no stamping stress: Chemical removal leaves no roll-over or internal stress, so lead fingers seat flat and bond or solder defects drop.
2. Half-etched steps in one pass: Die-pad recesses, lead thinning and lock holes form during the same etch, removing secondary machining.
3. Burr-free fine pitch: Chemical dissolution leaves no roll-over or dross, so closely spaced leads never short or damage the mold compound.
4. No tooling for fast revisions: Wearable part numbers change often, and a new geometry is just a new film, keeping samples and short runs economical.
5. Plating and bondability: With no heat-affected zone or work hardening, surface condition is uniform, so silver or NiPdAu plating gives stable gold-wire bonding.
6. Mixed part numbers on one panel: Different frames share registration marks on one sheet, which lowers handling and unit cost without separate dies.

Typical Applications

• Smartwatch SiP packages: Multi-row fine lead frames inside system-in-package modules, with die-pad recesses and lock holes formed in one pass for ball attach.
• TWS earbud microphone carriers: Micro lead frames for MEMS microphone packaging, with ultra-fine pitch and burr-free edges that keep the acoustic cavity clean.
• Health-patch sensor packages: Thin lead frames for bio-sensing chips, with half-etched thinning that eases skin-conformal bending and potting.
• AR-glass display drivers: Fine-pitch leads for micro-display driver chips whose coplanarity fits the compact optical module.
• Heart-rate and SpO2 modules: QFN lead frames with silver-plated bond surfaces and batch-wide consistency for high-speed pick-and-place.
• Flexible module interposers: Thin copper-alloy transfer leads with half-etched pre-scores that balance conductivity with assembly movement.

Design Notes & Process Considerations

1. Lead width versus thickness: Keep the narrowest lead at a safe ratio to stock thickness, or undercut will distort the finger and can break it.
2. Half-etch depth callout: Give target depth and tolerance for die-pad recesses and thinned zones, typically 30–70% of stock thickness.
3. Plating for bonding: Prefer silver or NiPdAu for gold-wire bonding, and state plating thickness so coatings do not hurt coplanarity.
4. Coplanarity: Specify overall coplanarity for surface-mount frames, and allow annealing to restore flatness where soldering demands it.
5. Dambars and lock holes: Reserve dambar positions and design lock holes for mold-compound grip, so leads do not deform after trim.
6. Complete drawing data: State alloy temper, lead positions, step depth and plating together; putting all six items on the print cuts back-and-forth confirmation.