Copper & Brass FeCl₃

Chemical Etching Formula
H90 brass with FeCl₃

This page documents the reference wet chemical etching formula for H90 brass using the FeCl₃ system. The recipe below covers a sheet-thickness range of 0.05-0.5 mm and is configured for through etch (double-sided). Every value is drawn from operational process records rather than theoretical calculation, and is provided as a starting point for your own process development.

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
34 °Bé Concentration
1.320 Specific Gravity
42 °C Bath Temperature
Through etch (double-sided) Etch Depth Type
0.05-0.5 mm Thickness Range
0.18 mm Typical Thickness
0.12-3.11 m/min Conveyor Speed Range
0.56 m/min Typical Speed
60-600 μm Min Hole Ø Range
100-500 μm Min Line Width Range
9-88 μm Undercut Range
2.85 Etch Factor (EF)
97.8% Typical Yield (97-98.1%)

Why FeCl₃ for H90 brass?

On H90 brass, 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 H90 brass etch line runs a variant of this formula.

Process Window & Bath Control

The process window for this FeCl₃ formula centres on 42°C and 34 °Bé. Conveyor speed spans 0.12-3.11 m/min over the 0.05-0.5 mm thickness band; the typical operating point is 0.56 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

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 60-600 μm and the minimum line width ranges 100-500 μm across the 0.05-0.5 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 9-88 μm, and the etch factor is about 2.85. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Design Rule Summary
• Minimum hole diameter range: 60-600 μm
• Minimum line width range: 100-500 μm
• Single-side undercut range: 9-88 μm
• Typical etch factor (EF): 2.85

Yield & Production Economics

Typical mass-production yield for H90 brass in the FeCl₃ system is 97.8%, within an observed range of 97-98.1%. 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 H90 brass 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

This formula is documented for a sheet-thickness range of 0.05-0.5 mm, with a typical value of 0.18 mm. Outside this band the same chemistry may still work, but conveyor speed and feature tolerances should be re-verified with a sample run before production.

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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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