Copper & Brass FeCl₃+HCl

Chemical Etching Formula
C7521 Nickel Silver with FeCl₃+HCl

This reference describes how C7521 Nickel Silver responds to the FeCl₃+HCl etching formula. At a bath temperature of 46°C and concentration of 42 °Bé, the recipe holds an etch factor of about 2.70 and a typical production yield of 97.1%. It is intended as engineering reference data for design, sourcing, and process planning.

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
0.2-2.97 m/min Conveyor Speed Range
0.71 m/min Typical Speed
60-360 μm Min Hole Ø Range
100-300 μm Min Line Width Range
9-56 μm Undercut Range
2.70 Etch Factor (EF)
97.1% Typical Yield (96.8-97.4%)

Why FeCl₃+HCl for C7521 Nickel Silver?

On C7521 Nickel Silver, 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 C7521 Nickel Silver etch line runs a variant of this formula.

Process Window & Bath Control

Bath control for C7521 Nickel Silver in FeCl₃+HCl: temperature 46°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 0.2-2.97 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

Design rules for this recipe: hole diameter 60-360 μm, line width 100-300 μm, single-side undercut 9-56 μm — all as a function of thickness across 0.05-0.3 mm. The higher the etch factor (this formula holds about 2.70), 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: 60-360 μm
• Minimum line width range: 100-300 μm
• Single-side undercut range: 9-56 μm
• Typical etch factor (EF): 2.70

Yield & Production Economics

Expect a yield in the 96.8-97.4% range for C7521 Nickel Silver with FeCl₃+HCl, with 97.1% 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

Typical applications for C7521 Nickel Silver 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.

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

Minimum line width ranges 100-300 μm over the supported thickness range, per the 1.0× thickness rule. At the fine end, photoresist resolution and adhesion — not the etchant — become the limiting factors, so resist selection matters as much as bath chemistry.

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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