Overview

A custom 304 stainless steel sensor diaphragm is a thin, photochemically etched flexure that converts pressure into a repeatable deflection in pressure sensors, load cells and MEMS devices. Type 304 stainless is chosen for its formability, corrosion resistance and batch-to-batch consistency of elastic modulus; etching thins the sensing area without introducing tool marks, so the diaphragm responds linearly over its full range. Because material is dissolved through a photoresist mask rather than machined or punched, the part leaves the line flat, burr-free and free of residual stress at the thinned edge.

For a sensor designer, a custom 304 stainless steel sensor diaphragm solves three recurring problems: sensing zones thinned to a few tens of microns with uniform thickness, fine features such as strain beams, island grooves and pressure ports that cannot be punched into a thin sheet without warping it, and edges that must survive millions of pressure cycles without micro-cracks that cause zero-point drift. Geometry is defined by artwork, so a new range is a new film rather than a new die. Supplied from 0.03 mm to 0.5 mm stock, diaphragms are typically passivated or electropolished to improve corrosion resistance and support bonding downstream.

Parameter Window

• Available Materials: stainless 304 / 304L, 316L, 301 spring temper on request
• Material Thickness Range: 0.03–0.5 mm
• Tolerance: ±0.005 mm on thinned-zone thickness, ±0.02 mm on outline profile
• Minimum Feature: 0.08 mm strain-beam width and 0.15 mm pressure-port diameter at 0.10 mm stock
• Surface Options: passivation, electropolish, bright anneal, stress-relief anneal, nickel plating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & DFM Review — Convert the diaphragm drawing to vector artwork and confirm thinning ratio, beam widths and corner radii.
2. Material & Temper Selection — Match 304 / 304L lot, cold-rolled temper and flatness to the pressure range and medium.
3. Cleaning & Lamination — Degrease and micro-etch the sheet, then laminate dry-film resist with no bubbles over thin zones.
4. UV Exposure — Expose both faces through registered film so front-side islands align to back-side thinning pockets.
5. Development & Inspection — Develop the resist and inspect thin zones for pinholes before etching.
6. Controlled Etching — Spray-etch in stainless-matched chemistry; time, temperature and conveyor speed set thinning depth.
7. Stripping, Anneal & Passivation — Strip resist, stress-relief anneal to stabilize elasticity, then passivate or electropolish.
8. Thickness & Linearity Verification — Measure thinned-zone thickness, profile and flatness, sample pressure linearity, then tray-pack.

Core Advantages

1. Uniform thin zone: Chemical thinning leaves no tool marks, so full-scale output stays linear and sensitivity scatter is low.
2. No hard tooling: A new pressure range is a new phototool rather than a die, keeping low-volume programs affordable.
3. Stress-free edges: Etched parts carry no stamped micro-cracks, surviving millions of pressure cycles without fatigue failure.
4. Fine sensing features: 0.08 mm beams and 0.15 mm ports hold at 0.10 mm stock for miniaturized sensor structures.
5. Corrosion resistant: Passivated 304 bonds, glass-seals and welds readily, giving broad packaging compatibility.
6. Batch repeatability: A custom 304 stainless steel sensor diaphragm from one approved film etches identically from first article to volume lots, simplifying qualification.

Typical Applications

• Pressure sensors: Sensing diaphragms for piezoresistive and capacitive pressure cores where linearity matters.
• MEMS devices: Elastic membranes and island structures in micro pressure and acceleration devices.
• Load and force cells: Thinned flexures in strain-gauge load cells that raise sensitivity.
• Differential pressure and flow: Isolating diaphragms in DP transmitters and flow sensors exposed to process media.
• Medical and automotive sensing: Thin parts for disposable pressure probes and manifold pressure sensors.
• Vacuum and barometry: Reference diaphragms in absolute and vacuum gauges with burr-free seating.

Design Notes & Process Considerations

1. Thinned zone versus stock: State target thin-zone thickness and tolerance, typically 20–50% of stock, together with beam width.
2. Corner radii: Use internal radii ≥ 0.10 mm at islands and beam roots to avoid stress concentration and resist trapping.
3. Thickness tolerance: Call out thickness tolerance and measurement points, since scatter directly sets sensitivity spread.
4. Flatness callout: Specify flatness per 25 mm and overall bow; thin parts distort during anneal if not fixtured.
5. Surface and medium: Note passivation or polish and the contact medium; chloride service favors 316L and a corrosion review.
6. Panelization and marking: Group parts on a shared registration grid with orientation marks to speed bonding and alignment.