Metal shims, washers and spacers are thin, flat precision components used for spacing, alignment, leveling, load distribution and gap filling in mechanical assemblies. When manufactured by photochemical etching, these parts deliver burr-free edges, zero residual stress and consistent dimensional accuracy — properties that are difficult to achieve consistently with stamping, laser cutting or waterjet, especially in ultra-thin gauges.

Etched shims, washers and spacers are produced directly from solid metal sheet without hard tooling, making them ideal for custom sizes, unusual shapes, tight tolerances and low-to-medium volume orders. Common materials include 304/316 stainless steel, spring steel, copper and copper alloys, brass, aluminum, titanium, beryllium copper, nickel silver and Inconel. Typical thickness ranges from 0.02 mm to 2.0 mm.

Step-by-Step Etching Workflow for Metal Shims, Washers & Spacers

1. DFM & Artwork ReviewEngineers review part drawings: outer diameter, inner hole, thickness, flatness requirements and edge quality. Undercut compensation is applied to maintain precise ID/OD dimensions. Multi-part nesting is optimized to reduce material cost, especially for thin shim stock.
2. Surface Pre-treatmentMetal sheets are cleaned by alkaline degreasing, acid pickling and DI water rinsing to remove oil, fingerprints and oxides, ensuring uniform photoresist adhesion and consistent etch rate.
3. Dry Film LaminationPhotosensitive dry film is laminated onto both sides of the cleaned sheet under controlled heat and pressure, forming a uniform protective mask.
4. UV Exposure & DevelopmentUV light transfers the shim/washer/spacer pattern onto the photoresist through a precision photomask. Developer washes away resist on areas to be etched, exposing bare metal; protected regions become the finished parts.
5. Controlled Chemical Etching (Core Step)Double-sided spray etching selectively dissolves exposed metal to form the outer contour and inner hole simultaneously. No mechanical force or thermal impact, so ultra-thin parts remain perfectly flat. Etch parameters are tightly controlled for consistent ID/OD dimensions across the whole sheet.
6. Resist Stripping & Multi-stage CleaningThe photoresist mask is stripped off, followed by multi-stage deionized water rinsing and drying to remove residual etchant.
7. Precision InspectionInspect ID, OD, thickness, flatness, burr condition and edge quality. Use microscopy and coordinate measuring machines for tight-tolerance features. Count and sort parts before packaging.
8. Optional Post-processingAvailable: passivation, electropolishing, deburring check, plating (nickel, tin, gold), flattening/leveling, sorting and kitting, laser marking for identification.

Core Advantages of Etched Metal Shims, Washers & Spacers

1. Burr-free, stress-free precision partsNo stamping shear or laser heat. Zero burrs, zero residual stress, no edge rollover. Parts lie perfectly flat — critical for accurate shim stacking and gap control.
2. Ultra-thin capabilityEtching handles foils from 0.02 mm that stamping and laser cutting cannot process reliably. Consistent quality across thousands of parts.
3. Tight tolerances & consistencyUniform feature size across the whole sheet, ideal for precision adjustment, alignment and calibration applications where consistency matters.
4. Custom shapes without hard toolingAny geometry — round, square, slotted, stepped, custom profiles — can be produced from digital artwork. No die cost, fast design changes.
5. Wide material & thickness rangeStainless steel, spring steel, copper, brass, aluminum, titanium, beryllium copper, Inconel and more. From ultra-thin foil to 2.0 mm plate.
6. Low cost for small-to-medium volumesNo tooling investment makes etching economical for prototypes, custom sizes and low-volume precision parts. For simple geometries in very high volume, stamping may be cheaper per unit.

Typical Applications

• Mechanical assembly: Precision shims for gap adjustment, alignment spacers, leveling washers
• Automotive: Transmission shim packs, brake components, bearing spacers, engine adjustment washers
• Electronics: PCB mounting spacers, insulator washers, antenna spacers, connector shims
• Industrial machinery: Bearing adjustment shims, gearbox spacers, tooling shims
• Aerospace: Structural alignment shims, shim packs for composite assemblies, thermal spacers
• Medical & instrumentation: Calibration spacers, instrument alignment washers, precision support shims

Design Limitations & Notes

Isotropic wet etching requires side-undercut compensation in CAD. Minimum feature width and hole size are generally limited by sheet thickness. Very high thickness (over 2.0 mm) is better handled by stamping, CNC or waterjet. Etched parts are flat 2D components; if a 3D formed shape is required, etching should be combined with a secondary forming step. For applications requiring hardened spring steel behavior, specify material heat treatment status during DFM review.