Chemical Etching Formula
SUS309S with FeCl₃+HCl

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 FeCl₃+HCl for SUS309S?

On SUS309S, 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 SUS309S etch line runs a variant of this formula.

Process Window & Bath Control

The process window for this FeCl₃+HCl formula centres on 52°C and 46 °Bé. Conveyor speed spans 0.12-0.95 m/min over the 0.1-0.5 mm thickness band; the typical operating point is 0.34 m/min. Every 5°C drop in bath temperature requires roughly a 30% reduction in conveyor speed to hold the same etch depth, so temperature stability is the single biggest lever on consistency.

Design Rules & Tolerances

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 120-600 μm and the minimum line width ranges 100-500 μm across the 0.1-0.5 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 19-95 μm, and the etch factor is about 2.62. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Yield & Production Economics

Typical mass-production yield for SUS309S in the FeCl₃+HCl system is 96.4%, within an observed range of 95.5-96.7%. The dominant yield-loss modes are photoresist pinhole defects and rinse-water contamination. Improving incoming sheet quality and photoresist coating consistency gives the highest yield-improvement leverage for this formula.

Typical Applications

Parts produced with the FeCl₃+HCl formula on SUS309S 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.

Process Equipment & Material Reference

On the shop floor, this SUS309S + FeCl₃+HCl recipe is implemented on a wet chemical etching machine. The 52°C bath setpoint and 0.12-0.95 m/min conveyor range correspond to verified production envelopes on that equipment for through etch (double-sided).

The Stainless Steel chemical etching guide reference goes one level above the recipe shown here, surveying the full thickness range, depth options, and common subgrades we run for stainless.

Production Use Cases for This Formula

Production examples for the SUS309S / FeCl₃+HCl recipe span juicer filtration mesh etching, stainless steel metal filter mesh, and stainless filtration mesh for vacuum cleaners. In every case, the etch factor and undercut figures on this page are the dominant tolerance drivers — bath maintenance discipline matters more than equipment headline rating.

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.

Other Metals Etched with FeCl₃+HCl

The FeCl₃+HCl chemistry is also documented for these alloys.

More Stainless Steel Formulas

Other formulas in the same material family.

Frequently Asked Questions