Chemical Etching Formula
Invar36 alloy with FeCl₃+HCl

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.

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.

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.

Process Equipment & Material Reference

On the shop floor, this Invar36 alloy + FeCl₃+HCl recipe is implemented on a wet chemical etching machine. The 50°C bath setpoint and 43.31 m/min conveyor range correspond to verified production envelopes on that equipment for half etch (single-sided).

If you need a wider view of invar beyond this single recipe, our Invar chemical etching guide covers grade selection, photoresist compatibility, and typical industries that consume this metal in etched form.

Production Use Cases for This Formula

Typical end-uses for Invar36 alloy run on this formula include heat-dissipation vent etching for VC cooling, stainless steel metal filter mesh, and high-precision etched lead frames. The 50°C bath and 0.01 mm supported thickness range cover most of the production work in these segments without re-tuning chemistry.

Designs that sit slightly outside this thickness or feature-size envelope are usually addressable by a sister formula in the same etchant family. The bath chemistry stays the same; the tuning shifts to conveyor speed and resist choice.

Other Metals Etched with FeCl₃+HCl

The FeCl₃+HCl chemistry is also documented for these alloys.

More Precision Alloys Formulas

Other formulas in the same material family.

Frequently Asked Questions