Chemical Etching Formula
SUS631(17-7PH)
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 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.
• 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.
Process Equipment & Material Reference
On the shop floor, this SUS631(17-7PH) + FeCl₃+HCl recipe is implemented on a biomedical blade etching machine. The 54°C bath setpoint and 0.16-2.4 m/min conveyor range correspond to verified production envelopes on that equipment for through etch (double-sided).
If you need a wider view of stainless beyond this single recipe, our Stainless Steel chemical etching guide covers grade selection, photoresist compatibility, and typical industries that consume this metal in etched form.
Production Use Cases for This Formula
Typical end-uses for SUS631(17-7PH) run on this formula include stainless steel metal filter mesh, stainless filtration mesh for vacuum cleaners, and stainless steel mesh for aroma diffusers. The 54°C bath and 0.05-0.3 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.
More Stainless Steel Formulas
Other formulas in the same material family.
Frequently Asked Questions
Sources & References
- ASTM E407: Standard Practice for Microetching Metals and Alloys
- ASTM B912: Standard Specification for Passivation of Stainless Steels
- Photo Chemical Machining Institute — process capability guidelines
- NIST Engineering Statistics Handbook — process tolerance and capability
Standards are referenced for context. Always confirm parameters against the current published edition and your own process validation.
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.