Overview

Spacer chemical etching makes a spacer by removing metal where the spacer should not be, which allows a single flat blank to carry several thickness levels. The sheet is laminated on both faces, exposed with a different image on each side where a step is needed, developed, and etched in stages: a first pass opens the through-cut outline, a second pass half-etches a pocket to a controlled depth, and a third pass, if required, produces a shallower relief. Because depth is set by dwell time in the etchant rather than by a cutter, a 0.3 mm recess in a 1.2 mm spacer is produced without machining marks, without clamping distortion and without a deburring operation afterwards.

The process suits spacers that set a gap and must therefore be flat and dimensionally honest. Etching removes material uniformly from the exposed face, so the blank does not bend the way a milled part bends when internal stress is released, and thin ribs between pockets stay straight instead of chattering. Substrates run from 0.1 mm to 2.0 mm in stainless steel 304/316L, aluminum 5052, brass, copper and nickel, with through-features held to ±0.05 mm and step depth to ±0.02 mm.

Parameter Window

• Available Materials: stainless steel 304/316L, aluminum 5052, brass H62, copper C110, nickel 201
• Material Thickness Range: 0.1–2.0 mm
• Tolerance: ±0.05 mm on through-features, ±0.02 mm on step depth, flatness 0.05 mm per 50 mm
• Minimum Feature: 0.25 mm slot, 0.3 mm hole and 0.2 mm rib at 0.5 mm stock
• Surface Options: as-etched matte, passivation, electropolishing, anodizing (aluminum), nickel plating, laser marking
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Geometry & Step Review — Check how many thickness levels the design needs, whether each step can be reached from an exposed face, and whether ribs survive the etch.
2. Material & Temper Selection — Choose alloy and temper for flatness after etching; hard tempers hold flat better but limit the depth of relief that can be produced cleanly.
3. Dual-Image Film Set — Build separate artwork for the top and bottom faces, with registration marks shared so the two sides align to the same datum.
4. Cleaning & Double-Sided Lamination — Degrease and laminate resist on both faces in one pass to keep the two images concentric and avoid handling between sides.
5. Top and Bottom Exposure — Expose each face with its own image; where a step is single-sided, the opposite face is fully masked.
6. Development & Step Inspection — Develop and verify that every pocket window is fully open before etching, since a partly opened window etches to the wrong depth.
7. Staged Etching — Etch in timed stages, masking and re-opening windows between stages so that each depth level is reached independently.
8. Strip, Measure & Pack — Remove resist, measure step depth and flatness on a sampling basis, then pack flat with interleaving to protect the etched faces.

Core Advantages

1. Multiple thickness levels in one part: Steps, pockets and through-cuts come from one sheet, replacing a stack of separate shims with a single part number.
2. Depth by time, not by tool: Step depth is controlled by etch time and chemistry, so a 0.05 mm relief is as repeatable as a 0.5 mm one, with no cutter deflection.
3. No machining stress: Chemical removal does not induce the bending that milling releases, so thin ribs and wide pockets stay flat after the part is freed.
4. No burr, no deburr: There is no cutting edge, so edges need no secondary operation and no residual burr is left in a pocket where it could trap contamination.
5. Complex outlines without dies: Curved outlines, interrupted edges and internal windows cost the same as a plain ring, since the shape lives in the film.
6. Clean surfaces for bonding: Etched faces are uniformly matte and free of coolant residue, which gives consistent adhesion for gaskets, adhesives and coatings. That surface quality is why spacer chemical etching is chosen for bonded assemblies.

Typical Applications

• Stack assembly spacers: Parts that set the gap between stacked plates, with pockets that clear screw heads and connector bodies.
• Optical spacing rings: Rings that hold lens-to-sensor distance, half-etched to reduce wall thickness without losing stiffness.
• Sensor air-gap spacers: Flat spacers with a controlled recess that sets a magnetic or capacitive gap to ±0.02 mm.
• Connector height spacers: Thin plates that establish connector seating height in board-to-board assemblies.
• Motor end spacers: Insulating and locating plates between winding ends and housing, cut in 0.5 mm aluminum.
• Shield cavity spacers: Frames with pockets that create a controlled cavity depth under a shielding can.

Design Notes & Process Considerations

1. Step count: Each additional depth level adds an etch stage and a handling step; designs with more than three levels should be reviewed for cost before release.
2. Access to each step: A pocket can only be etched from a face that is exposed to the spray; blind steps open from the side must be reachable or they will etch unevenly.
3. Depth versus width: A pocket deeper than its width etches more slowly at the bottom; keep depth at or below half the pocket width for consistent results.
4. Rib width: Keep ribs at 1.0 × material thickness minimum, and radius internal corners, because a sharp re-entrant corner etches into a weak point.
5. Flatness callout: Specify flatness per 50 mm and state the measuring condition; single-sided etching of a large area will bow a thin blank unless balanced.
6. Marking and orientation: Etched faces are visually similar, so add a mark or a break in symmetry if the part must be assembled in one orientation. A spacer chemical etching supplier should flag this at drawing review, not at assembly.