Carbon & Tool Steel FeCl₃+HCl

Chemical Etching Formula
SK5 Tool Steel with FeCl₃+HCl

Working with SK5 Tool Steel on a chemical etch line begins with the right formula. The FeCl₃+HCl system documented below produces through etch (double-sided) across 0.1-0.3 mm sheet, with a minimum hole-diameter range of 120-360 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
44 °Bé Concentration
1.410 Specific Gravity
50 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.1-0.3 mm Thickness Range
0.20 mm Typical Thickness
0.19-1 m/min Conveyor Speed Range
0.35 m/min Typical Speed
120-360 μm Min Hole Ø Range
100-300 μm Min Line Width Range
19-56 μm Undercut Range
2.70 Etch Factor (EF)
96.3% Typical Yield (96-96.5%)

Why FeCl₃+HCl for SK5 Tool Steel?

Ferric-chloride-based formulas are the industrial workhorse for ferrous, nickel, and copper-bearing alloys like SK5 Tool Steel. The Fe³⁺ ion oxidizes the metal surface; where HCl is present it regenerates dissolved species and stabilizes chloride concentration. The result on SK5 Tool Steel is anisotropic etching with predictable undercut and an easily regenerated spent bath.

Process Window & Bath Control

The process window for this FeCl₃+HCl formula centres on 50°C and 44 °Bé. Conveyor speed spans 0.19-1 m/min over the 0.1-0.3 mm thickness band; the typical operating point is 0.35 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

When laying out artwork for SK5 Tool Steel at through etch (double-sided), plan for a minimum hole diameter in the 120-360 μm range and a minimum line width in the 100-300 μm range, depending on the chosen sheet thickness within 0.1-0.3 mm. The etch factor of ~2.70 and undercut range of 19-56 μm determine how much the mask must be biased to land the finished dimension on target.

Design Rule Summary
• Minimum hole diameter range: 120-360 μm
• Minimum line width range: 100-300 μm
• Single-side undercut range: 19-56 μm
• Typical etch factor (EF): 2.70

Yield & Production Economics

Expect a yield in the 96-96.5% range for SK5 Tool Steel with FeCl₃+HCl, with 96.3% 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 SK5 Tool 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.

More Carbon & Tool Steel Formulas

Other formulas in the same material family.

50CrV4 Spring Steel FeCl₃+HCl Through etch (double-sided) 65Mn Spring Steel FeCl₃+HCl Through etch (double-sided) 65Mn Spring Steel FeCl₃+HCl Half etch (single-sided) DT4 pure iron FeCl₃+HCl Through etch (double-sided) SK2 Tool Steel FeCl₃+HCl Through etch (double-sided) SK3 Tool Steel FeCl₃+HCl Through etch (double-sided)

Frequently Asked Questions

Single-side undercut ranges 19-56 μm depending on thickness and dwell time. When sizing the photomask for a finished feature on SK5 Tool Steel, subtract twice the expected undercut from the target width so the etched dimension lands on specification.

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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