Precision Alloys FeCl₃+HCl

Chemical Etching Formula
Invar36 alloy with FeCl₃+HCl

This page documents the reference wet chemical etching formula for Invar36 alloy using the FeCl₃+HCl system. The recipe below covers a sheet-thickness range of 0.01 mm and is configured for half etch (single-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+HCl Etchant System
44 °Bé Concentration
1.410 Specific Gravity
50 °C Bath Temperature
Half etch (single-sided) Etch Depth Type
0.01 mm Thickness Range
0.01 mm Typical Thickness
43.31 m/min Conveyor Speed Range
43.31 m/min Typical Speed
10 μm Min Hole Ø Range
100 μm Min Line Width Range
1 μm Undercut Range
2.76 Etch Factor (EF)
97.1% Typical Yield (97.1%)

Why FeCl₃+HCl for Invar36 alloy?

Ferric-chloride-based formulas are the industrial workhorse for ferrous, nickel, and copper-bearing alloys like Invar36 alloy. The Fe³⁺ ion oxidizes the metal surface; where HCl is present it regenerates dissolved species and stabilizes chloride concentration. The result on Invar36 alloy 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 43.31 m/min over the 0.01 mm thickness band; the typical operating point is 43.31 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 Invar36 alloy at half etch (single-sided), plan for a minimum hole diameter in the 10 μm range and a minimum line width in the 100 μm range, depending on the chosen sheet thickness within 0.01 mm. The etch factor of ~2.76 and undercut range of 1 μm determine how much the mask must be biased to land the finished dimension on target.

Design Rule Summary
• Minimum hole diameter range: 10 μm
• Minimum line width range: 100 μm
• Single-side undercut range: 1 μm
• Typical etch factor (EF): 2.76

Yield & Production Economics

Typical mass-production yield for Invar36 alloy in the FeCl₃+HCl system is 97.1%, within an observed range of 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

Invar36 alloy etched with this recipe typically ends up in hermetic sealing rings, lead frames matched to glass/ceramic, and magnetic shielding. Because chemical etching applies no mechanical or thermal load, the finished features are free of work-hardening and heat-affected zones — a decisive advantage over stamping or laser cutting for these uses.

More Precision Alloys Formulas

Other formulas in the same material family.

1J22 Iron-Cobalt Alloy FeCl₃+HCl Through etch (double-sided) 1J46 Permalloy FeCl₃+HCl Through etch (double-sided) 1J50 Permalloy FeCl₃+HCl Through etch (double-sided) 1J79 Permalloy FeCl₃+HCl Through etch (double-sided) 1J85 Super-Permalloy FeCl₃+HCl Through etch (double-sided) HyMu80 (Permalloy) FeCl₃+HCl Through etch (double-sided)

Frequently Asked Questions

This recipe is configured for half etch (single-sided). The 50°C bath, 44 °Bé concentration, and 43.31 m/min conveyor-speed range are tuned for that depth type. Switching between through-etch and half-etch, or single- versus double-sided, requires re-tuning conveyor speed and may change the mask design.

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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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