Overview

Roll to roll etching for lead frames is a continuous photochemical process that images, develops and etches a moving metal strip rather than individual sheets, producing lead frame features reel after reel with consistent geometry. Copper alloys such as C194 and C7025, iron-nickel Alloy 42, and 304 stainless are unwound from coil, laminated on both faces, exposed through a registered photo-tool, and sprayed with etchant that dissolves the unwanted metal between the leads. Because the strip keeps moving, etch time, temperature and conveyor speed are locked to the line speed, so lead width, pitch and half-etch depth stay uniform along hundreds of meters of material. The result is a burr-free, stress-free frame with fine leads, ready for plating, die attach and molding.

For semiconductor packaging and connector makers, roll to roll etching for lead frames replaces both stamping and sheet-based chemical etching when volume and fine pitch matter. Stamping struggles below about 0.15 mm lead width and introduces mechanical stress into thin leads, while sheet etching cannot match the throughput of a continuous line. A reel-to-reel line holds 0.1 mm leads on 0.2 mm pitch, keeps etch factor under control on both faces, and delivers parts in coil form that feed directly into automated plating and assembly equipment. Changeover between frame designs is a photo-tool swap, so high-mix production stays practical.

Parameter Window

• Available Materials: copper alloys C194/C7025, iron-nickel Alloy 42, Kovar, 304 stainless, phosphor bronze
• Material Thickness Range: 0.1–0.3 mm strip, 50–300 mm coil width
• Tolerance: ±0.02 mm on lead pitch, ±0.01 mm on half-etch depth, etch factor held per lot
• Minimum Feature: 0.1 mm lead width, 0.1 mm gap, 0.2 mm pitch at 0.15 mm stock
• Surface Options: selective silver / nickel / palladium plating, anti-tarnish, reel and leader tape, 2D/3D half-etch
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Coil Preparation — Slit and level the incoming strip, then verify thickness, temper and surface cleanliness.
2. Lamination — Apply dry-film resist to both faces under controlled heat and pressure as the strip advances.
3. Continuous Exposure — Expose the registered photo-tool on the moving strip with front-to-back alignment held by fiducials.
4. Development — Wash out unexposed resist to open the lead and tie-bar areas, then inspect line definition inline.
5. Etching — Spray etchant matched to the alloy, balancing line speed, temperature and pressure for a controlled etch factor.
6. Stripping — Remove resist and neutralize the strip before it is rinsed and dried in-line.
7. Plating & Finishing — Apply selective silver, nickel or palladium on functional areas and add anti-tarnish protection.
8. Rewind & Inspection — Check lead width, pitch and coplanarity by vision system, then rewind with interleaving and lot records.

Core Advantages

1. Continuous throughput: Reel-fed processing removes sheet handling and keeps etch conditions stable over long runs.
2. Fine pitch without stress: Chemical removal forms 0.1 mm leads without the mechanical shock a stamping die imparts.
3. Controlled etch factor: Two-sided spray keeps undercut symmetric, so lead width holds at the top and bottom of the strip.
4. Direct downstream feed: Coil-form output mates with automatic plating, die-attach and molding equipment.
5. Fast design changeover: A new frame is a new photo-tool, not a progressive die, easing high-mix production.
6. Material breadth: Roll to roll etching for lead frames handles copper, Alloy 42 and stainless on one line, covering leaded, QFN and connector-style frames.

Typical Applications

• IC lead frames: Fine-pitch frames for SOIC, QFP and QFN packages in copper or Alloy 42.
• LED lead frames: High-volume silver-plated frames for lighting and display packages.
• Connector contacts: Reeled contact strips with tight pitch for board-to-board and I/O connectors.
• Semiconductor substrates: Half-etched lead patterns for power devices and discrete components.
• Shielding cans and frames: Etched outlines later formed into EMI shields on the same reel.
• Sensor and MEMS leads: Thin, burr-free lead arrays for sensor and micro-system packaging.

Design Notes & Process Considerations

1. Etch factor allowance: Compensate artwork for the expected undercut so the finished lead width lands on target.
2. Lead width versus thickness: Keep lead width at roughly 1.2 × stock thickness or greater for reliable etching.
3. Tie-bar strategy: Design tie bars to hold the frame rigid through etching and plating without leaving hard-to-remove stubs.
4. Plating definition: Mark selective plating zones clearly and note masking limits near fine leads.
5. Coil format: Specify width, pitch, reel core, leader/trailer length and winding tension for downstream feeders.
6. Coplanarity: Call out lead coplanarity and camber per reel, since reel memory affects automated placement.