Overview

Micro shim etching is a photochemical machining route for producing ultra-thin spacers, washers and gap shims where thickness and flatness matter more than outline complexity. A dry-film resist is laminated to both faces of precision-rolled foil, the part outline and any half-etched steps are exposed and developed, and a matched etchant dissolves the unwanted metal from both sides at once. Because no die contacts the part, the shim leaves the line flat, burr-free and free of the rolled edge, work hardening and grinding marks that stamping and lapping leave behind. Stock is usually 304 or 316L stainless, 301 spring stainless, C17200 beryllium copper, C1100 copper, brass, nickel or Alloy 42, rolled to gauges from 0.01 mm to 1.0 mm.

For a buyer, micro shim etching solves the thickness stack-up problem that dominates precision assemblies. Shims are often stacked two, three or five deep to set a bearing preload or an optical gap, and every ±0.01 mm of error multiplies through the stack; photochemical processing holds a single shim to ±0.005 mm, or ±0.002 mm on selected thin gauges, without a grinding pass. Half-etching lets one part carry two or three thickness zones — a thick rim for handling and a thin flexing web — so a single component replaces a stack of separate washers. The result is a dimensionally stable, stress-free shim that seats flush and does not relax after assembly.

Parameter Window

• Available Materials: 304/316L stainless, 301 spring stainless, C17200 beryllium copper, C1100 copper, brass, nickel 200, Alloy 42
• Material Thickness Range: 0.01–1.0 mm, with 0.02–0.3 mm most common
• Tolerance: ±0.005 mm on thickness (down to ±0.002 mm on thin gauges); ±0.01 mm on profile
• Minimum Feature: 0.10 mm slot width and 0.15 mm hole at 0.05 mm stock; half-etch step depth ±10 % of gauge
• Surface Options: as-rolled, passivated, electropolished, black oxide, tin/nickel plating, adhesive handling tab
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Gauge Certification — Map incoming foil thickness by micrometer and assign a lot so the thickness budget is traceable.
2. Artwork & Step Design — Draw full-cut outlines and half-etched zones, compensating each level for its own side-etch allowance.
3. Cleaning & Lamination — Degrease and laminate dry film to both faces under controlled heat and pressure.
4. Exposure — Register the film to the sheet datum so all nested shims share one reference.
5. Development & Inspection — Open the cut areas and half-etch windows, then verify resist adhesion on thin webs.
6. Controlled Etching — Etch from both sides, timing the bath so through-cuts separate cleanly while half-etch zones stop at depth.
7. Stripping & Stress Relief — Strip resist, neutralize, and low-temperature anneal where flatness after bonding is critical.
8. Verification & Packing — Gauge-check every shim by contact or laser micrometer, then pack between liners to prevent bending.

Core Advantages

1. Tight thickness control: Certified foil plus chemical removal holds ±0.005 mm without grinding, so stack height stays predictable.
2. Flat and burr-free: No die roll or burr means the shim seats flush, spreads clamp load evenly and will not score mating faces.
3. Stress-free parts: No stamping force or thermal recast layer, so spring-temper 301 and beryllium copper keep their specified temper.
4. Multi-level in one piece: Half-etched steps create thick rims and thin webs in a single component, cutting part count and stack-up.
5. No hard tooling: A new thickness or outline is a new film; prototype gauges can be sampled without a lapping fixture.
6. Clean edges at thin gauge: Slots and holes hold dimension on 0.02 mm foil, where a punch would tear or deform the web.

Typical Applications

• Bearing preload shims: Precision spacers that set axial play in spindle and gearbox assemblies.
• Optical & laser mounts: Gap shims that fix lens spacing and alignment without tilting the optic.
• Semiconductor fixtures: Thin alignment and masking shims for bonding and test jigs.
• Valve & pump shims: Calibrated spacers setting spring seat height and clearance in fluid controls.
• Fuel-cell & battery stacks: Conductive spacers in copper or nickel that set compression and carry current.
• Aerospace gap shims: Lightweight, traceable spacers for skin-panel and actuator stack-ups.

Design Notes & Process Considerations

1. Thickness budget: State the total stack tolerance and let the supplier allocate the per-shim tolerance; ±0.005 mm each is realistic for three-deep stacks.
2. Flatness callout: Specify flatness per 25 mm and request stress-relief anneal, because thin foil curls after resist stripping.
3. Half-etch depth: Give step depth as an absolute value and a percentage of gauge; 50 % steps are easiest to hold consistently.
4. Burr and edge: Require burr-free edges explicitly when the shim slides against a seal or a coated housing.
5. Grain direction: Note rolling direction for spring-temper 301 and beryllium copper, since flexural behavior is anisotropic.
6. Nested layout: When a design uses micro shim etching across many gauges, group parts by foil lot on one sheet so thickness stays uniform.