Stainless Steel FeCl₃+HCl

Chemical Etching Formula
SUS304 with FeCl₃+HCl

Working with SUS304 on a chemical etch line begins with the right formula. The FeCl₃+HCl system documented below produces half etch (single-sided) across 0.01 mm sheet, with a minimum hole-diameter range of 8 μm and a minimum line-width range of 100 μm. The numbers scale with thickness — thinner stock yields finer features.

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.

FeCl₃+HCl Etchant System
44 °Bé Concentration
1.410 Specific Gravity
48 °C Bath Temperature
Half etch (single-sided) Etch Depth Type
0.01 mm Thickness Range
0.01 mm Typical Thickness
74.85 m/min Conveyor Speed Range
74.85 m/min Typical Speed
8 μm Min Hole Ø Range
100 μm Min Line Width Range
1 μm Undercut Range
2.80 Etch Factor (EF)
97.8% Typical Yield (97.8%)

Why FeCl₃+HCl for SUS304?

On SUS304, the ferric chloride system attacks the alloy's oxide layer continuously while ferric ions drive dissolution. It is regenerable, compatible with standard photolithography, and produces clean burr-free edges — which is why nearly every SUS304 etch line runs a variant of this formula.

Process Window & Bath Control

Bath control for SUS304 in FeCl₃+HCl: temperature 48°C, concentration 44 °Bé, specific gravity 1.410. The recipe is tuned for half etch (single-sided). Conveyor speed is the primary throughput control, ranging 74.85 m/min across the supported thickness range. Check specific gravity each shift with a calibrated hydrometer and correct with fresh make-up or water as needed.

Design Rules & Tolerances

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 8 μm and the minimum line width ranges 100 μm across the 0.01 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 1 μm, and the etch factor is about 2.80. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Design Rule Summary
• Minimum hole diameter range: 8 μm
• Minimum line width range: 100 μm
• Single-side undercut range: 1 μm
• Typical etch factor (EF): 2.80

Yield & Production Economics

Expect a yield in the 97.8% range for SUS304 with FeCl₃+HCl, with 97.8% typical on a well-controlled line. Most rejects trace back to upstream coating and exposure rather than to the etch bath itself, so tightening photolithography control is usually the fastest path to a higher number.

Typical Applications

Parts produced with the FeCl₃+HCl formula on SUS304 are common in precision shims, encoder discs, RF/EMI shields, surgical and dental components, fuel-cell bipolar plates, and fine filter meshes. The burr-free, stress-free nature of chemical etching makes it the preferred process wherever flatness and edge quality matter more than raw throughput.

More Stainless Steel Formulas

Other formulas in the same material family.

AM350 Stainless Steel FeCl₃+HCl Through etch (double-sided) SUS2205 Duplex Stainless FeCl₃+HCl Through etch (double-sided) SUS2507 Super Duplex FeCl₃+HCl Through etch (double-sided) SUS301 FeCl₃+HCl Through etch (double-sided) SUS301 FeCl₃+HCl Through etch (double-sided) SUS302 FeCl₃+HCl Through etch (double-sided)

Frequently Asked Questions

This recipe is configured for half etch (single-sided). The 48°C bath, 44 °Bé concentration, and 74.85 m/min conveyor-speed range are tuned for that depth type. Switching between through-etch and half-etch, or single- versus double-sided, requires re-tuning conveyor speed and may change the mask design.

Need a Quote for This Process?

WET Etched runs production wet chemical etching lines using the FeCl₃+HCl chemistry. Send us your part drawing and quantity for a full process quote.

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