Overview

Custom leadframe etching builds a semiconductor leadframe from a customer drawing rather than from a standard catalogue. The strip is laminated with photoresist, exposed through a film generated from the drawing, developed, and etched so that the die pad, the inner leads, the outer leads and the tie bars appear as metal that was never cut. Lead width, gap and outline all come from the artwork, which means a new package layout is quoted on its geometry instead of on a die.

That is the point of ordering a custom leadframe. A stamping tool for a fine-pitch frame costs real money and takes weeks to cut, and every design change means modifying or scrapping it. With etching, the first article and the production part come off the same drawing, a revision is a new film, and a prototype can be in a package for evaluation long before a tool would have been finished. Copper C194 and C7025, plus alloy 42, are the usual materials, from 0.10 mm to 0.50 mm.

Parameter Window

• Available Materials: copper C194, C7025, alloy 42 (FeNi42), phosphor bronze
• Material Thickness Range: 0.10–0.50 mm
• Tolerance: lead width ±0.02 mm; outline and hole position ±0.03 mm
• Minimum Feature: 0.04 mm lead width at 0.10 mm stock; 0.10 mm lead pitch
• Surface Options: Ni/Pd/Au plating, selective silver, solder mask, anti-tarnish, spot plating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Drawing Review — Check lead width, gap, die pad size and tie bar layout against the strip thickness, and return a marked-up drawing where the design is outside the process window.
2. Material and Strip Definition — Confirm alloy, temper, strip width and grain direction; alloy 42 is chosen for stiffness and low expansion, copper for conductivity.
3. Panel Layout and Film — Nest the frames on the strip with the handling rails and indexing holes, then generate one film per revision and archive it with a revision number.
4. Lamination — Clean the strip and apply dry film resist on both faces; voids under the resist become missing or bridged leads later.
5. Exposure and Development — Expose with the pattern registered to the indexing holes, develop, and inspect the finest lead width before etching.
6. Etching — Etch from one or both faces depending on the lead geometry, controlling dwell so lead width and etch taper land inside tolerance.
7. Plating and Singulation — Strip the resist, plate Ni/Pd/Au or selective silver, then cut the strip to length or into individual frames as specified.
8. Inspection and Packing — Measure lead width, pitch, coplanarity and plating thickness, then pack in antistatic trays or on reels with a first-article report.

Core Advantages

1. No tooling charge: The only part-specific item is a film, so a low-volume or first-build frame does not carry the cost of a stamping die.
2. Revisions cost a drawing: When the die pad moves or a lead is added, the film is regenerated and the strip is re-etched — no tool modification, no scrapped die.
3. Prototype and production from one source: Sample frames for package evaluation and the production order run on the same process, so what is qualified is what ships.
4. Burr-free leads: Chemical removal leaves no roll-over, so lead tips sit flat for wire bonding and solder, and there is no burr to short a fine pitch.
5. Fine pitch without punch load: Stamping thin gaps in 0.5 mm copper loads the tool heavily; etching has no such limit and holds 0.10 mm pitch with clean walls.
6. Mixed layouts on one strip: Several frame designs can share a panel and an indexing scheme, which keeps engineering builds and family variants economical.

Typical Applications

• IC package frames: QFN, SOP and TSSOP frames with fine inner leads, produced to a customer's own pad layout.
• Power device frames: Copper frames for MOSFETs and diodes where thermal conduction through the die pad is the design driver.
• Optoelectronic packages: Alloy 42 frames for LED and sensor packages that need low thermal expansion.
• Sensor and MEMS carriers: Open-cavity frames with etched windows for pressure and flow dies.
• Connector and terminal strips: Etched contact arrays that need a defined spring geometry without a progressive die.
• Engineering prototypes: Small lots for package qualification, where a tooling lead time would stall the programme.

Design Notes & Process Considerations

1. Respect the thickness-to-gap ratio: A gap narrower than about 1.2× the strip thickness etches with visible taper; if the design needs it, thinner stock is the cheaper answer.
2. Say whether the frame is etched one or two sides: Double-sided etching halves the taper and holds lead width, but needs tighter front-to-back registration.
3. Define the tie bar and rail: Handling rails, indexing holes and tie bars are part of the delivery, not an afterthought — their position sets how the strip runs through assembly.
4. Choose plating by the assembly process: Wire bonding, die attach and soldering each want a different finish; Ni/Pd/Au, selective silver and anti-tarnish are not interchangeable.
5. Give the datum for coplanarity: State the seating plane and the flatness limit, because a frame that bows after plating will not sit flat in a mould or on a board.
6. Send the revision, not a sketch: A dimensioned drawing with a revision number keeps custom leadframe etching reproducible; a marked photo invites a re-interpretation at the next build.