Copper & Brass FeCl₃+HCl

Chemical Etching Formula
C7100 Cupronickel with FeCl₃+HCl

Working with C7100 Cupronickel 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
42 °Bé Concentration
1.390 Specific Gravity
46 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.05-0.3 mm Thickness Range
0.15 mm Typical Thickness
0.19-2.83 m/min Conveyor Speed Range
0.68 m/min Typical Speed
60-360 μm Min Hole Ø Range
100-300 μm Min Line Width Range
9-55 μm Undercut Range
2.72 Etch Factor (EF)
96.9% Typical Yield (96.5-97.1%)

Why FeCl₃+HCl for C7100 Cupronickel?

On C7100 Cupronickel, 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 C7100 Cupronickel etch line runs a variant of this formula.

Process Window & Bath Control

Hold the bath at 46°C with concentration 42 °Bé (specific gravity 1.390). Across the 0.05-0.3 mm thickness range, conveyor speed runs from 0.19-2.83 m/min — thinner sheets move faster, thicker sheets slower, in roughly inverse proportion to thickness. A typical mid-range setpoint is 0.68 m/min for 0.15 mm stock. Use redundant PID temperature control to hold the bath within ±1.5°C, and titrate at least once per shift.

Design Rules & Tolerances

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 60-360 μm and the minimum line width ranges 100-300 μm across the 0.05-0.3 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 9-55 μm, and the etch factor is about 2.72. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Design Rule Summary
• Minimum hole diameter range: 60-360 μm
• Minimum line width range: 100-300 μm
• Single-side undercut range: 9-55 μm
• Typical etch factor (EF): 2.72

Yield & Production Economics

Typical mass-production yield for C7100 Cupronickel in the FeCl₃+HCl system is 96.9%, within an observed range of 96.5-97.1%. 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

Typical applications for C7100 Cupronickel processed with FeCl₃+HCl include lead frames, busbars, flexible heater elements, RF gaskets, and precision electrical contacts. The formula's tolerance band and yield make it well suited to medium-to-high-volume precision flat parts.

Process Equipment & Material Reference

Production of C7100 Cupronickel parts using the FeCl₃+HCl formula described above runs on a wet chemical etching machine configured for through etch (double-sided). The bath chemistry, conveyor speed, and rinse cascade detailed on this page reflect the operating profile we use on a live spray-etching line for this alloy.

Related to this formula, the Copper chemical etching guide page documents the full process envelope for the same alloy family, including pre-treatment chemistry and post-etch inspection criteria.

Production Use Cases for This Formula

Typical end-uses for C7100 Cupronickel run on this formula include stainless filtration mesh for vacuum cleaners, tea-infuser custom filter etching, and high-speed air-intake mesh for hair dryers. The 46°C bath and 0.05-0.3 mm supported thickness range cover most of the production work in these segments without re-tuning chemistry.

If your part falls into one of these classes — or a closely adjacent one — this formula is usually the right starting point. We confirm fit with a short sample run on the actual sheet stock before locking in mask artwork.

More Copper & Brass Formulas

Other formulas in the same material family.

C1020 OF Copper FeCl₃ Through etch (double-sided) C1100 T2 copper FeCl₃ Through etch (double-sided) C1100 T2 copper FeCl₃ Through etch (double-sided) C1100 T2 copper FeCl₃ Through etch (double-sided) C1100 T2 copper FeCl₃ Through etch (double-sided) C1100 T2 copper FeCl₃ Half etch (single-sided)

Frequently Asked Questions

Yes. Wet chemical etching is a non-contact chemical process with no mechanical cutting or thermal input, so etched C7100 Cupronickel features are completely free of burrs, work-hardening, and heat-affected zones. That edge quality is the defining advantage over stamping or laser cutting for precision flat parts.
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Reviewed by
Chief Engineer, Wet Etching · WET Etched
Ph.D., Metallurgical & Chemical Engineering, Xiamen University

Sources & References

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.

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