Overview

Precision metal etching for sensors is a photochemical machining process in which a photoresist mask defines the part geometry and a matched chemical etchant dissolves the unwanted metal. Because the material is dissolved rather than sheared, parts leave the bath with no burrs, no mechanical stress and no heat-affected zone — the three dominant failure sources in sensor manufacturing. Substrates are typically stainless steel 304/316L, copper, nickel, phosphor bronze, beryllium copper, Kovar, Invar and titanium, supplied as foil or light stock from 0.02 mm to 1.5 mm. The process holds features down to roughly 1.2–1.5 times material thickness, keeps thickness uniform across a full panel, and yields parts that are flat, clean-edged and dimensionally repeatable from prototype to production volume.

Parameter Window

• Available Materials: 304/316L stainless steel, copper, nickel, phosphor bronze, beryllium copper, Kovar, Invar, titanium and their alloys
• Material Thickness Range: 0.02–1.5 mm (thin foil to light stock, depending on alloy)
• Tolerance: about ±10% of material thickness; on thin foil down to ±0.01 mm on critical dimensions
• Minimum Feature: 1.2–1.5 × material thickness for slots, apertures and grid lines
• Surface Options: passivation, Ni/Au/Ag/Sn plating, blackening, annealing; the etched edge is the final edge
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Material Selection & Incoming Inspection — Verify alloy, temper, thickness and surface condition against the drawing, and record the heat number for traceability.
2. Artwork & Phototool Generation — Compensate the artwork for isotropic undercut based on material thickness, then output high-resolution film or laser direct-imaging data.
3. Cleaning & Photoresist Lamination — Degrease and deoxidize the surface, then laminate dry film or coat liquid resist without bubbles or trapped particles.
4. UV Exposure — Calibrate exposure energy to resist thickness so that pattern sidewalls stay steep and linewidth stays on target.
5. Development — Wash away unexposed resist to open the areas to be etched, then inspect pattern integrity before the parts enter the etchant.
6. Etching — Match chemistry to the alloy (ferric chloride, cupric chloride or acid-based), run spray or immersion, and monitor etchant temperature, concentration and etch rate in real time.
7. Resist Stripping & Surface Finishing — Strip resist, neutralize and rinse, then passivate or plate as specified; anneal where the temper must be restored.
8. Inspection & Packaging — Sample dimensions, burr height and flatness with vision and profilometry systems, then package in tape-and-reel or trays.

Core Advantages

1. Burr-free edges: A diaphragm or membrane is never pierced and no leak path is created, so sealing faces mate cleanly and gasket compression stays predictable.
2. Zero mechanical stress: No shearing means no work hardening and no residual stress, so resistance, permeability and elastic modulus stay at design values.
3. No heat-affected zone: Metallurgy and magnetic properties are untouched; annealed and hard tempers both survive the process without reformulation.
4. No tooling investment: A design change is a film change, so prototypes move from weeks to days and low volumes no longer carry die amortization.
5. Micro features on thin foil: Slots, fine grids and dense hole arrays are routine at 0.02–0.1 mm, geometries that stamping cannot hold without distortion.
6. Batch consistency: Panel-to-panel and lot-to-lot variation is small, so calibration coefficients do not have to be rewritten for every delivery.

Typical Applications

• Strain gauge grids & load cell flexures: Foil grids form in a single step with uniform grid width and clean bond pads.
• Pressure sensor diaphragms & shims: Uniform diaphragm thickness plus burr-free edges gives stable deflection and reliable sealing.
• Capacitive & electrochemical sensor electrodes: Interdigitated electrodes and reference grids hold spacing accurately across the array.
• Temperature sensor lead frames & RTD masks: Fine leads are etched in one pass with no stamped roll-over or burr on the bond area.
• Flow sensor orifice plates & gas sensor grids: Aperture arrays come out with consistent hole diameter for even flow distribution.
• Magnetic & Hall sensor shims, EMI shields: Thin stock stays flat, so parts seat without warp during assembly.

Design Notes & Process Considerations

1. Feature-to-thickness ratio: Keep minimum slot width and hole diameter at 1.2 × thickness or greater; thinner stock allows finer geometry.
2. Undercut compensation: Etching is isotropic and removes roughly 0.8–1 × thickness per side, so artwork must be pre-enlarged by that amount.
3. Thickness uniformity: On diaphragm parts, specify the allowed center-to-edge thickness difference and use zoned spray to improve it.
4. Edge quality callout: State "burr-free, no recast layer, no discoloration" explicitly and agree the sampling method and acceptance criteria.
5. Stress and annealing: Where elasticity or magnetic performance must be restored after lamination and etching, put the annealing schedule on the drawing.
6. Panelization and registration: Array multiple parts per panel to raise throughput, and keep fiducial marks for downstream placement and inspection.