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2026-08

Can a 20 μm Aperture Be Chemically Etched in a Shadow Mask?

Introduction

A stated minimum aperture size should never be evaluated in isolation from material thickness, pattern density, web width, tolerance requirements, and overall mask geometry.

A manufacturer may be able to evaluate an opening of approximately 20 μm under favorable conditions of thin foil, controlled pitch, and suitable material. This capability statement does not imply that every 20 μm aperture can be produced reliably in stainless steel, nickel, copper, or other alloys at arbitrary thickness, spacing, tolerance, or mask size. The complete aperture system must be reviewed as an interdependent set of parameters.

NKEYTO processes customized metal foils in the approximate thickness range 0.01–2.0 mm. Common production thicknesses include 0.03 mm, 0.05 mm, 0.10 mm, 0.20 mm, 0.50 mm, and 1.00 mm. Pattern accuracy typically falls in the range ±0.01–0.05 mm, contingent on structure, thickness, and process route. These figures remain subject to specific design review and are not universal guarantees.

Why Thickness Matters

Chemical etching is a partially isotropic process. Material is removed both vertically through the sheet thickness and laterally beneath the photoresist edge. As the required etch depth increases, lateral undercut becomes progressively more significant relative to the target aperture width.

A practical geometric indicator is the thickness-to-opening ratio:

where

= material thickness,
= target aperture width.

A 20 μm opening in a 20 μm foil presents a fundamentally different manufacturing risk from the same opening in a 100 μm sheet. A high ratio can produce:

Incomplete or partially closed apertures
Excessive side etching that enlarges the opening beyond tolerance
Narrow or irregular aperture throats
Pronounced wall taper
Reduced dimensional consistency across the panel
Lower production yield

Double-sided etching can reduce the etch distance required from each surface and thereby improve the achievable aspect ratio. However, front-to-back artwork registration then becomes a critical process variable; misalignment between the two sides directly degrades aperture wall geometry and dimensional yield.

Pitch and Web Width Are Equally Important

A single 20 μm test opening near the center of a laboratory coupon is not equivalent to an array of thousands of 20 μm apertures distributed across a production mask. Dense patterns alter local etchant transport, loading, and the structural integrity of the remaining metal.

If the ligament (web) between adjacent apertures is too narrow, undercut from both sides can weaken or completely eliminate the web. The resulting defects include broken bridges, pattern distortion, local sagging, and an increase in the effective mask-to-substrate gap during deposition.

A complete DFM review must therefore examine:

Aperture width and length
Material thickness and thickness tolerance
Center-to-center pitch
Minimum remaining web width after etching
Overall pattern density and open-area percentage
Distance from the patterned region to the free edge of the mask
Total mask dimensions and flatness requirements

High aperture counts also increase inspection burden. Measuring every opening is often impractical; the sampling plan, critical zones, and acceptance criteria must be agreed upon before production begins.

Deposition Performance May Be the Real Limitation

Even when a 20 μm aperture satisfies dimensional inspection, it may still fail to deliver the intended deposited feature. Vacuum evaporation is primarily a line-of-sight process. A relatively thick aperture wall can obstruct vapor arriving at non-normal incidence angles, producing sidewall shadowing, edge displacement, or feature enlargement.

Additional factors that interact with the finished aperture geometry include:

Mask-to-substrate gap
Source-to-substrate distance and angular distribution of the vapor flux
Wall taper left by the etching process
Local thermal deformation of the foil during deposition
Progressive aperture closure caused by film buildup on repeated use

Consequently, the smallest manufacturable opening is not automatically the smallest functionally useful opening. Manufacturing capability and deposition-process performance must be validated separately.

What Information Is Needed for Evaluation?

For a meaningful feasibility assessment, the following data should be supplied:

Vector CAD data (DXF, DWG, STEP, IGES preferred)
Exact material grade and temper
Foil thickness and thickness tolerance
Aperture dimensions, shape, and pitch
Patterned-area dimensions and overall mask size
Positional and dimensional tolerances on critical features
Intended mask-to-substrate gap
Source-to-substrate geometry and deposition method
Alignment and mounting method
Inspection criteria and sampling plan

A prototype should be validated both dimensionally and through an actual deposition trial. Only the combination of these results separates process capability from functional performance inside the vacuum chamber.

Engineering Recommendation

Treat the 20 μm figure as a process-limit indicator rather than a guaranteed capability. Feasibility is determined by the simultaneous satisfaction of thickness-to-opening ratio, web integrity, pattern density, etch-factor control, dimensional yield, and deposition geometry.

When the design approaches these limits, practical options include reducing foil thickness, enlarging the aperture, increasing pitch, adopting double-sided etching with tight registration control, adjusting tolerance strategy, or evaluating an alternative process route. A drawing-based DFM review performed before artwork release remains the most reliable method of quantifying risk and protecting both manufacturing yield and deposition accuracy.

About NKEYTO

NKEYTO is the international brand of Shenzhen Xintu Precision Hardware Co., Ltd., a precision metal manufacturing supplier based in Shenzhen, China.

We provide one-stop precision metal manufacturing services, including chemical etching, precision laser cutting, stamping, CNC machining, electroplating, and other customized surface treatments. Our capabilities support the development and production of precision metal components for industries such as semiconductors, electronics, optics, medical devices, and industrial applications.

With engineering support and flexible manufacturing capabilities, we help customers develop customized metal parts from prototypes to small and medium-volume production.

For technical evaluation or quotation, please feel free to contact:

Luna
Head of International Trade & Pre-Sales Technical Consultant
Email: luna@nkeyto.com
WhatsApp: +1 213 221 9094
Phone / WeChat: +86 135 5470 8126

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