Custom lead frames manufactured by photochemical etching are critical metal substrates for semiconductor packaging, serving as the bridge connecting semiconductor chips and external circuits. Compared with stamping lead frames, etching technology can produce ultra-fine, high-density pin structures on thin metal sheets. Pin width, pitch, pattern and outer profile can be customized according to packaging design. The product is flat, free of burrs and residual stress. Common materials include Kovar alloy, copper alloy, nickel silver, stainless steel. Typical thickness ranges from 0.02 mm to 0.3 mm. Widely used in IC packaging, discrete devices, optoelectronic components, LED packages, MEMS and micro sensors.

Step-by-Step Etching Workflow for Custom Lead Frame

1. DFM & Artwork OptimizationEngineers review vector drawings, calculate undercut compensation, check pin width, pitch and bridge layout. Optimize the design to avoid fragile narrow pins, ensure consistent dimensional accuracy for ultra-fine lead structures.
2. Surface Pre-treatmentMetal sheets go through alkaline degreasing, rinsing and oxide removal. Remove oil, fingerprints and surface contaminants to guarantee stable photoresist adhesion and uniform etching depth.
3. Dry Film Photoresist LaminationUV-sensitive dry film is laminated on both sides of the metal sheet under controlled heat and pressure to form uniform protective mask.
4. UV Exposure & DevelopmentUV light transfers lead frame pattern onto photoresist. The developer washes away resist on the area to be etched, exposing bare metal; protected regions form leads, pads and support frames.
5. Chemical Etching (Core Step)Custom etchant selectively dissolves exposed metal, double-sided etching forms precise lead frame structures. No mechanical impact, so ultra-thin, fine-pitch pins remain flat and undeformed.
6. Resist Stripping & Multi-stage CleaningStrip off photoresist mask, followed by DI water rinsing to remove residual etching chemicals.
7. Optional Post-processingSecondary operations: surface passivation, pre-plating (nickel, silver, gold), deburring inspection, tape mounting, carrier frame processing.
8. Precision Inspection & PackagingInspect pin dimension, pitch, flatness and edge quality. Use microscope and coordinate measuring machine for precision measurement, then vacuum packaging for semiconductor cleanroom requirements.

Core Advantages of Etched Custom Lead Frame

1. Ultra-fine high-density pinsCapable of ultra-narrow lead width and ultra-fine pitch, suitable for advanced small-size packaging that stamping cannot achieve.
2. Burr-free & stress-freeNo mechanical stamping force. Zero burrs, no residual stress, no pin deflection, stable flatness for packaging assembly.
3. High pattern flexibilityComplex irregular layouts, special pad shapes and custom support bridges can be realized easily. Design revision is convenient.
4. No expensive hard toolingOnly digital vector artwork required. Fast prototype turnaround, low cost for small batch sampling and new product verification.
5. Special alloy material supportProcess Kovar, copper alloy, nickel silver and other packaging-specific alloys to meet thermal expansion and conductivity requirements.
6. Consistent dimensional stabilityUniform etching across the whole sheet, tight tolerance for micro lead features.

Typical Applications

• Semiconductor IC packaging: SOP, SOIC, QFN, DIP, small package IC lead frames
• Discrete semiconductor devices: diodes, transistors, thyristor lead frames
• Optoelectronics: LED, photodiode, laser diode packaging lead frames
• MEMS & sensors: micro sensor, pressure sensor, medical sensing component lead frames
• Micro electronics: micro connector lead structures, miniature electronic packaging components

Design Limitations & Notes

Etching is isotropic, side undercut must be fully considered in DFM phase. Minimum lead width is limited by material thickness. For mass production of very large quantity and relatively simple pin structure, stamping lead frame may have better unit price. Etched lead frames are mainly recommended for prototype, low volume and ultra-fine pitch complex packaging.