Chemical Etching Formula
SUP9 Spring Steel 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 SUP9 Spring Steel?

On SUP9 Spring Steel, 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 SUP9 Spring Steel etch line runs a variant of this formula.

Process Window & Bath Control

Bath control for SUP9 Spring Steel in FeCl₃+HCl: temperature 48°C, concentration 42 °Bé, specific gravity 1.390. The recipe is tuned for through etch (double-sided). Conveyor speed is the primary throughput control, ranging 0.2-1.02 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 120-360 μm and the minimum line width ranges 100-300 μm across the 0.1-0.3 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 18-55 μm, and the etch factor is about 2.72. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Yield & Production Economics

Expect a yield in the 96.3-96.8% range for SUP9 Spring Steel with FeCl₃+HCl, with 96.6% 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 SUP9 Spring Steel processed with FeCl₃+HCl include spring elements, blades, shim stock, and stamped-replacement flat parts. The formula's tolerance band and yield make it well suited to medium-to-high-volume precision flat parts.

Process Equipment & Material Reference

Process equipment for the SUP9 Spring Steel / FeCl₃+HCl combination is built around our precision acid cleaning machine platform — closed-loop temperature control, redundant pump headers, and metering for bath replenishment all directly affect the etch factor and yield numbers cited on this page.

The 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 steel.

Production Use Cases for This Formula

Parts produced with this SUP9 Spring Steel + FeCl₃+HCl formula end up in a wide range of finished products. Representative production runs we have completed using this exact recipe family include tea-infuser custom filter etching, stainless steel metal filter mesh, and juicer filtration mesh etching. Each case shares the same root sensitivity: clean photoresist edges, a tightly held bath SG of 1.390, and a conveyor speed inside the 0.2-1.02 m/min envelope.

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 Carbon & Tool Steel Formulas

Other formulas in the same material family.

Frequently Asked Questions