Overview

A wafer bumping stencil etching service converts your wafer bump map into a framed, fine-pitch stainless steel stencil ready for solder bump or flux deposition. The service applies the right aperture reduction and wall treatment for bump-level geometries, etches the apertures from both sides of full-hard 304 stainless foil, electropolishes the walls, and verifies aperture size, foil thickness and tension before the stencil ships. What you receive is a stencil that deposits the same material volume at every pad, wafer after wafer.

The service is built for the exacting tolerances of wafer-level packaging, where bump height uniformity decides yield. Apertures are held to ±0.01 mm, foil to ±0.005 mm, and pitch reaches 0.15 mm, so solder bump, copper pillar and micro-bump arrays can be produced without hard tooling. Because the pattern is photographic, a prototype stencil is made in days and revised at no die cost, letting bump map iterations move at development speed. For packaging and assembly teams, the service removes the aperture-to-aperture variation that causes starved or bridged bumps.

Parameter Window

• Available Materials: full-hard 304 stainless steel, 301 stainless steel
• Material Thickness Range: 0.05–0.2 mm foil
• Tolerance: ±0.01 mm on aperture size, ±0.005 mm on foil thickness
• Minimum Feature: 0.08 mm aperture and 0.15 mm pitch
• Surface Options: electropolished, nano-coated, nickel plated, framed
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Bump Map Intake — Receive the wafer bump map or CAD data and convert it to aperture artwork, confirming pitch and die layout.
2. DFM Feedback — Return a manufacturability note flagging apertures at risk of poor release, with suggested reductions and wall finish.
3. Material Selection — Choose full-hard 304 stainless foil at the specified thickness for dimensional stability and strength.
4. Cleaning & Lamination — Degrease both sides and laminate dry film under controlled pressure for clean aperture areas.
5. Exposure & Development — Expose both sides through registered films and develop to open the bump apertures symmetrically.
6. Etching — Etch from both sides in matched chemistry, timing the process so apertures meet with clean walls.
7. Stripping & Electropolishing — Remove resist and electropolish to smooth aperture walls and radius edges for uniform release.
8. Inspection & Framing — Verify aperture size, wall quality and thickness, then frame the stencil and measure tension before shipping.

Core Advantages

1. Volume-ready supply: One process chain serves a prototype stencil and full production, with no retooling between stages.
2. Fast bump-map turns: Photographic tooling delivers a prototype in days, keeping packaging development on schedule.
3. Uniform deposition: Tight aperture and thickness control deposit consistent volume at every pad for even bump height.
4. Smooth release: Electropolished or nano-coated walls release paste and flux cleanly, cutting starved and bridged bumps.
5. Fine pitch without tooling: Bump arrays down to 0.15 mm pitch are produced from film, with no punch die cost.
6. Framed and verified: Stencils are framed under measured tension and checked, so they print flat out of the box — the mark of a reliable wafer bumping stencil etching service.

Typical Applications

• Solder bump deposition: Aperture arrays for printing solder paste to form solder bumps on wafer pads.
• Copper pillar bumping: Stencils for paste deposition in copper pillar bump formation.
• Wafer-level flux printing: Fine apertures for printing flux before ball placement or reflow.
• Micro-bump arrays: Ultra-fine apertures for micro-bump interconnects in advanced packaging.
• Redistribution bumping: Apertures aligned to redistribution layer pads for bump deposition.
• Pillar and stud stencils: Openings for solder studs and pillars in power and RF devices.

Design Notes & Process Considerations

1. Area ratio: Keep aperture opening area above 0.66 of wall area, or paste and flux will not release cleanly on fine bump apertures.
2. Deposit volume: Specify target deposited volume or bump height so foil thickness and aperture size can be balanced.
3. Wall finish: Electropolished or nano-coated walls are essential for uniform release on fine bump arrays.
4. Die alignment: Confirm the aperture array matches the wafer die layout and fiducials for stencil-to-wafer registration.
5. Frame and tension: State mesh tension and frame size so the stencil stays flat over the full wafer area.
6. Thickness tolerance: Call out foil thickness tolerance, since it directly drives bump height uniformity across the wafer.