Copper & Brass FeCl₃

Chemical Etching Formula
C5210 phosphor bronze with FeCl₃

Working with C5210 phosphor bronze on a chemical etch line begins with the right formula. The FeCl₃ system documented below produces through etch (double-sided) across 0.05-0.5 mm sheet, with a minimum hole-diameter range of 60-600 μm and a minimum line-width range of 100-500 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 Etchant System
40 °Bé Concentration
1.380 Specific Gravity
46 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.05-0.5 mm Thickness Range
0.20 mm Typical Thickness
0.12-2.77 m/min Conveyor Speed Range
0.40 m/min Typical Speed
60-600 μm Min Hole Ø Range
100-500 μm Min Line Width Range
9-91 μm Undercut Range
2.76 Etch Factor (EF)
97.4% Typical Yield (96.7-97.8%)

Why FeCl₃ for C5210 phosphor bronze?

Ferric-chloride-based formulas are the industrial workhorse for ferrous, nickel, and copper-bearing alloys like C5210 phosphor bronze. The Fe³⁺ ion oxidizes the metal surface; where HCl is present it regenerates dissolved species and stabilizes chloride concentration. The result on C5210 phosphor bronze is anisotropic etching with predictable undercut and an easily regenerated spent bath.

Process Window & Bath Control

Hold the bath at 46°C with concentration 40 °Bé (specific gravity 1.380). Across the 0.05-0.5 mm thickness range, conveyor speed runs from 0.12-2.77 m/min — thinner sheets move faster, thicker sheets slower, in roughly inverse proportion to thickness. A typical mid-range setpoint is 0.40 m/min for 0.20 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

Design rules for this recipe: hole diameter 60-600 μm, line width 100-500 μm, single-side undercut 9-91 μm — all as a function of thickness across 0.05-0.5 mm. The higher the etch factor (this formula holds about 2.76), 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: 60-600 μm
• Minimum line width range: 100-500 μm
• Single-side undercut range: 9-91 μm
• Typical etch factor (EF): 2.76

Yield & Production Economics

Typical mass-production yield for C5210 phosphor bronze in the FeCl₃ system is 97.4%, within an observed range of 96.7-97.8%. 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 C5210 phosphor bronze processed with FeCl₃ 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.

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

Spent FeCl₃ bath contains dissolved C5210 phosphor bronze ions and depleted oxidizer. Standard practice is chemical or electrolytic regeneration to recover activity, plus periodic decanting of metal-rich sludge for off-site recovery. Treatment to neutral pH with metals precipitation is the minimum before any discharge, and requirements vary by jurisdiction.

Need a Quote for This Process?

WET Etched runs production wet chemical etching lines using the FeCl₃ chemistry. Send us your part drawing and quantity for a full process quote.

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