Chemical Etching Formula
Kovar 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 Kovar alloy?

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

Process Window & Bath Control

Hold the bath at 50°C with concentration 44 °Bé (specific gravity 1.410). Across the 0.01 mm thickness range, conveyor speed runs from 30.36 m/min — thinner sheets move faster, thicker sheets slower, in roughly inverse proportion to thickness. A typical mid-range setpoint is 30.36 m/min for 0.01 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

Feature sizes scale with sheet thickness. For this formula the minimum hole diameter ranges 12 μm and the minimum line width ranges 100 μm across the 0.01 mm band, following the industry 1.2× (hole) and 1.0× (line) thickness rules. Single-side undercut ranges 2 μm, and the etch factor is about 2.75. Size your photomask by subtracting twice the expected undercut from each finished feature dimension.

Yield & Production Economics

Typical mass-production yield for Kovar alloy in the FeCl₃+HCl system is 97.0%, within an observed range of 97%. 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

Kovar 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

Process equipment for the Kovar alloy / FeCl₃+HCl combination is built around our wet chemical etching machine platform — closed-loop temperature control, redundant pump headers, and metering for bath replenishment all directly affect the etch factor and yield numbers cited on this page.

The Kovar chemical etching guide reference goes one level above the recipe shown here, surveying the full thickness range, depth options, and common subgrades we run for kovar.

Production Use Cases for This Formula

Parts produced with this Kovar alloy + FeCl₃+HCl formula end up in a wide range of finished products. Representative production runs we have completed using this exact recipe family include custom thin-film heating elements, electronic thin-film component etching, and ultrasonic mesh for robotic vacuum cleaners. Each case shares the same root sensitivity: clean photoresist edges, a tightly held bath SG of 1.410, and a conveyor speed inside the 30.36 m/min envelope.

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