Stainless Steel FeCl₃+HCl

Chemical Etching Formula
SUS631(17-7PH) with FeCl₃+HCl

Working with SUS631(17-7PH) on a chemical etch line begins with the right formula. The FeCl₃+HCl system documented below produces through etch (double-sided) across 0.05-0.3 mm sheet, with a minimum hole-diameter range of 60-360 μm and a minimum line-width range of 100-300 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
46 °Bé Concentration
1.430 Specific Gravity
54 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.05-0.3 mm Thickness Range
0.15 mm Typical Thickness
0.16-2.4 m/min Conveyor Speed Range
0.58 m/min Typical Speed
60-360 μm Min Hole Ø Range
100-300 μm Min Line Width Range
10-58 μm Undercut Range
2.58 Etch Factor (EF)
96.1% Typical Yield (95.6-96.3%)

Why FeCl₃+HCl for SUS631(17-7PH)?

On SUS631(17-7PH), 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 SUS631(17-7PH) etch line runs a variant of this formula.

Process Window & Bath Control

The process window for this FeCl₃+HCl formula centres on 54°C and 46 °Bé. Conveyor speed spans 0.16-2.4 m/min over the 0.05-0.3 mm thickness band; the typical operating point is 0.58 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

Design rules for this recipe: hole diameter 60-360 μm, line width 100-300 μm, single-side undercut 10-58 μm — all as a function of thickness across 0.05-0.3 mm. The higher the etch factor (this formula holds about 2.58), the tighter the achievable tolerance. Below the minimum feature sizes, yield falls off steeply, so treat those numbers as hard floors rather than targets.

Design Rule Summary
• Minimum hole diameter range: 60-360 μm
• Minimum line width range: 100-300 μm
• Single-side undercut range: 10-58 μm
• Typical etch factor (EF): 2.58

Yield & Production Economics

Expect a yield in the 95.6-96.3% range for SUS631(17-7PH) with FeCl₃+HCl, with 96.1% 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 SUS631(17-7PH) 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

Run the bath at 54°C. Holding much above 59°C can degrade photoresist adhesion and erode feature edges; running below 49°C slows the etch and forces a conveyor-speed reduction. Production lines hold 54°C within ±1.5°C using redundant PID control.

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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