Overview

Thin shim etching cuts shims out of foil by photochemical machining, so a 0.02 mm or 0.05 mm shim keeps the flatness it had on the coil instead of picking up the roll-over, dimple and work hardening that a stamping die leaves behind. Resist is laminated on both faces, exposed through artwork, developed, and the outline is dissolved through the full thickness in one pass. Nothing clamps or strikes the foil, and the only force on the part is fluid pressure, so the face stays dead flat and the edge meets it at close to a right angle.

That flatness is the whole point. A shim does its job by filling a gap to a known value, and a face that is domed by even a few micrometres changes the stack height, tilts the clamped part and loads one side of a bearing or seal. Thin shim etching holds thickness to the tolerance of the incoming coil, holds flatness to about 0.03 mm per 100 mm, and repeats the same edge condition across thousands of pieces, which is why thin shims are specified for gearbox end play, optical spacing and sensor gap setting rather than being punched.

Parameter Window

• Available Materials: stainless steel 304/316L, brass H62/H65, copper C1100, nickel silver, beryllium copper
• Material Thickness Range: 0.02–0.3 mm
• Tolerance: ±0.05 mm on profile, ±0.01 mm on shim thickness, flatness 0.03 mm per 100 mm
• Minimum Feature: 0.08 mm slot width, 0.1 mm inner corner radius, 0.15 mm hole on 0.05 mm stock
• Surface Options: as-etched, passivated, degreased and oil-free, adhesive tabs, laminated stacks, marked part numbers
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Drawing and Stack Check — Confirm the shim outline, the target stack height and whether the part is used singly or as a laminated pack.
2. Foil Selection — Choose alloy and temper with certified thickness; flatness of the incoming coil sets the ceiling for the finished part.
3. Carrier Mounting — Temporarily bond foil below 0.05 mm to a rigid carrier so it can travel the line without buckling or edge curl.
4. Resist Lamination — Laminate dry film on both faces with matched nip pressure, keeping the film thin enough for 0.08 mm slots to open.
5. Exposure — Expose through registered film on both sides so the top and bottom outlines align and the wall does not lean.
6. Development — Wash out the unexposed resist, then verify slot openings and fine tabs before etching begins.
7. Through Etching — Spray etchant until the outline breaks through, then limit over-etch so the edge stays square and the shim does not thin at the rim.
8. Stress Relief and Inspection — Strip, neutralize, flatten between platens where required, then check thickness, flatness and burr before packing flat.

Core Advantages

1. Flat by process, not by luck: No die impact means no dome, no oil-canning and no residual stress pattern, so the shim sits flush in the gap it was designed for.
2. Thickness is the coil's thickness: Etching removes material in plane only, so a 0.05 mm shim measures 0.05 mm everywhere instead of thinning at the edge as a stamped part does.
3. Square, burr-free edge: The wall meets the face at close to 90° with no roll-over, so stacked shims do not gap or cock when clamped.
4. No work hardening: The foil is never bent or sheared, so soft tempers stay soft and thin brass does not crack at a tight inner corner.
5. Cheap revisions: Adjusting a shim by 0.02 mm in outline or adding a relief notch is a film change, not a die rework.
6. Stack building: Several thicknesses can be etched from matched foil and supplied as a numbered pack, so a mechanic adds shims to a target clearance instead of measuring each one.

Typical Applications

• Gearbox end play: 0.05 mm and 0.1 mm stainless shims set bearing preload without introducing a tilted face.
• Optical spacing: Blackened brass shims establish air gaps between lens elements and stops where 0.01 mm matters.
• Sensor gap setting: Thin non-magnetic shims set the clearance between a hall element and a target wheel.
• Motor and pump alignment: Laminated packs correct shaft height and angular misalignment under a bolted foot.
• Electronics thermal gaps: Copper shims bridge a die to a heat spreader where a thick pad would add resistance.
• Watch and instrument assembly: Sub-0.05 mm brass shims tune end shake in small mechanisms without burr interference.

Design Notes & Process Considerations

1. Do not design below the foil you can buy: A 0.02 mm callout only makes sense if the alloy is available in that gauge; otherwise the stack should be built from two thinner layers.
2. Slot width versus thickness: Keep slots at 1.5 × thickness or wider; narrower slots etch slowly and the resist is prone to lift at the edge.
3. Inner corners need radius: Specify 0.1 mm minimum radius. A sharp internal corner concentrates stress and etches into a keyhole shape.
4. Tabs and handling: Parts under 10 mm across should be supplied on a frame with break-off tabs, otherwise they are lost or bent during packing.
5. Flatness callout: State flatness per 100 mm on a free-standing part, and say whether it is measured before or after any plating step.
6. Cleanliness for bonded joints: If the shim goes under an adhesive or into a sealed cavity, require oil-free, particle-clean supply — thin shim etching leaves no lubricant, but handling and packing still have to be controlled.