Chemical Etching Formula
Au Pure Gold with Aqua Regia (3:1 HCl:HNO₃)

Formula Summary

The table below summarizes every parameter that defines this etching formula. Values listed as ranges scale with sheet thickness across the supported band.

Why Aqua Regia (3:1 HCl:HNO₃) for Au Pure Gold?

Aqua Regia (3:1 HCl:HNO₃) earns its place as a Au Pure Gold etching formula through repeatability. The bath can be titrated and corrected each shift to hold concentration (as specified) and specific gravity (1.150) within a tight band, which keeps the etch factor near 2.75 and yield near 98.4% run after run.

Process Window & Bath Control

Hold the bath at 28°C with concentration as specified (specific gravity 1.150). Across the 0.03-0.1 mm thickness range, conveyor speed runs from 0.8-4.87 m/min — thinner sheets move faster, thicker sheets slower, in roughly inverse proportion to thickness. A typical mid-range setpoint is 2.26 m/min for 0.05 mm stock. Use redundant PID temperature control to hold the bath within ±1.5°C, and titrate at least once per shift.

Design Rules & Tolerances

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 36-120 μm and the minimum line width ranges 100 μm across the 0.03-0.1 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 46160 μm, and the etch factor is about 2.75. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Yield & Production Economics

This formula delivers a typical yield of 98.4% (range 98.3-98.4%). At that rate, per-part economics are driven mostly by fixed photomask and setup cost for small batches and by sheet utilisation for large runs. The chemistry itself does not change with quantity, so the same recipe serves prototype and production volumes.

Typical Applications

Au Pure Gold etched with this recipe typically ends up in fine jewelry components, electrical contacts, and decorative inlays. Because chemical etching applies no mechanical or thermal load, the finished features are free of work-hardening and heat-affected zones — a decisive advantage over stamping or laser cutting for these uses.

Process Equipment & Material Reference

On the shop floor, this Au Pure Gold + Aqua Regia (3:1 HCl:HNO₃) recipe is implemented on a knife-mold etching machine. The 28°C bath setpoint and 0.8-4.87 m/min conveyor range correspond to verified production envelopes on that equipment for through etch (double-sided).

The material above is documented on this page at the recipe level. Bath chemistry, temperature, and conveyor speed are the controlling variables for repeatable output.

Production Use Cases for This Formula

Typical end-uses for Au Pure Gold run on this formula include stainless steel shower-head filter mesh, stainless filtration mesh for vacuum cleaners, and mobile-phone earpiece mesh. The 28°C bath and 0.03-0.1 mm supported thickness range cover most of the production work in these segments without re-tuning chemistry.

Adjacent applications usually transfer onto this same formula with no chemistry change, sometimes only a conveyor speed tweak. Drop a drawing and a target volume and we will return a process card built off the parameters on this page.

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Frequently Asked Questions