Stainless Steel FeCl₃+HCl

Chemical Etching Formula
SUS321 with FeCl₃+HCl

For engineers selecting an etching chemistry for SUS321, the FeCl₃+HCl formula shown here defines the bath composition, temperature window, and achievable feature sizes across a 0.1-0.5 mm thickness band. Typical mass-production yield for this recipe is 96.4%, with a typical conveyor speed of 0.34 m/min at 50°C.

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
45 °Bé Concentration
1.420 Specific Gravity
50 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.1-0.5 mm Thickness Range
0.20 mm Typical Thickness
0.12-0.95 m/min Conveyor Speed Range
0.34 m/min Typical Speed
120-600 μm Min Hole Ø Range
100-500 μm Min Line Width Range
19-93 μm Undercut Range
2.70 Etch Factor (EF)
96.4% Typical Yield (95.5-96.7%)

Why FeCl₃+HCl for SUS321?

Ferric-chloride-based formulas are the industrial workhorse for ferrous, nickel, and copper-bearing alloys like SUS321. The Fe³⁺ ion oxidizes the metal surface; where HCl is present it regenerates dissolved species and stabilizes chloride concentration. The result on SUS321 is anisotropic etching with predictable undercut and an easily regenerated spent bath.

Process Window & Bath Control

Hold the bath at 50°C with concentration 45 °Bé (specific gravity 1.420). Across the 0.1-0.5 mm thickness range, conveyor speed runs from 0.12-0.95 m/min — thinner sheets move faster, thicker sheets slower, in roughly inverse proportion to thickness. A typical mid-range setpoint is 0.34 m/min for 0.20 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

When laying out artwork for SUS321 at through etch (double-sided), plan for a minimum hole diameter in the 120-600 μm range and a minimum line width in the 100-500 μm range, depending on the chosen sheet thickness within 0.1-0.5 mm. The etch factor of ~2.70 and undercut range of 19-93 μm determine how much the mask must be biased to land the finished dimension on target.

Design Rule Summary
• Minimum hole diameter range: 120-600 μm
• Minimum line width range: 100-500 μm
• Single-side undercut range: 19-93 μm
• Typical etch factor (EF): 2.70

Yield & Production Economics

Expect a yield in the 95.5-96.7% range for SUS321 with FeCl₃+HCl, with 96.4% 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

Typical applications for SUS321 processed with FeCl₃+HCl include precision shims, encoder discs, RF/EMI shields, surgical and dental components, fuel-cell bipolar plates, and fine filter meshes. The formula's tolerance band and yield make it well suited to medium-to-high-volume precision flat parts.

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

FeCl₃+HCl balances oxidation rate, bath stability, and photoresist compatibility for SUS321. More aggressive chemistries over-etch and roughen sidewalls; milder ones stall or attack the resist. This formula's concentration (45 °Bé) and 50°C bath keep the etch factor near 2.70 with predictable undercut.

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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