Precision Etched Stainless Steel Flat Thin Metal Shims 0.02mm To 1.5mm Burr Free Edges

Precision Etched Stainless Steel Shims — Thin Sheet, Burr Free Edges

A shim is a thin metal part that fills a gap, takes up a tolerance or protects a seating face, and it is usually the cheapest part in an assembly and the one that decides whether the assembly sits correctly. These shims are produced by photo chemical etching: the outline, holes, slots and any fine features are etched out of sheet metal through a photoresist mask, so the part is cut by chemistry rather than by a die or a cutter.

The practical consequence is that the part keeps the thickness of the sheet it came from, the edge carries no die roll-over and no grinding burr, and a drawing change is made in the artwork rather than in a hard tool.

Etched shim compared with a stamped or ground shim

Thickness, flatness and edge quality

• Thickness comes from the sheet. The part is not machined down, so the nominal thickness is the sheet thickness, and thickness variation follows the tolerance of the coil rather than the tolerance of a grinding operation
• One flat face is preserved. Because nothing is ground or coined, the face that was masked keeps the original surface of the sheet, which is what a shim needs when it seats against a machined face
• Edges are burr free. Etching removes material from both faces at once, so there is no rolled-over edge to interfere with stacking or to scratch a mating surface
• Thin parts need care with flatness. A large open area on thin sheet can bow after etching, so open area, sheet thickness and part size are considered together at review, and parts can be supplied flat or with a flatness call-out agreed on the drawing
• Half-etched marking is possible. Where a part needs identification, a shallow etched mark can be produced in the same process instead of printing or laser marking

Materials and surface finishes

Shims are usually specified in stainless steel because it holds a flat face and does not need plating to resist handling corrosion. Common choices are SUS301 for a harder, springier shim, SUS304 for general use and SUS316 where corrosion resistance matters. Copper alloys, beryllium copper, phosphor bronze and nickel are also etchable where the application calls for conductivity, spring properties or solderability.

Finishing is chosen per application: passivation for stainless parts, electropolishing where a smoother, brighter edge and surface are wanted, or nickel, gold, tin or silver plating where contact resistance, solderability or appearance matter. Plating thickness and the areas to be masked are agreed on the drawing, since plating adds to the part thickness and cannot be applied selectively without masking.

Specification

Where etched shims are used

• Electronics: spacing shims, grounding and contact shims, shielding and mounting plates
• Medical devices: thin spacer and locating shims in instruments and diagnostic equipment
• Automotive: clearance and preload shims for sensors, brackets and moving assemblies
• Semiconductor and vacuum equipment: flat shims and masks around fixtures and chambers
• Industrial automation: adjustment shims for guides, motors and fixture alignment

What these applications have in common is a flat, thin part that has to sit correctly on the first try, and an assembly where a burr or a thickness step would show up as misalignment rather than as a cosmetic defect.

Inspection on each lot

• Outline, hole and slot dimensions against the drawing
• Thickness checked on the finished part, not only on the incoming sheet
• Visual check for incomplete etching, residual resist, staining and edge condition
• Flatness check where the drawing calls for it
• Plating thickness and appearance where a finish is specified
• Quantity and packing check before dispatch

Information needed for a quotation

Send the drawing with the outline and feature dimensions, the material grade, the sheet thickness, the tolerance required on profile and on thickness, the surface finish, the first order quantity and the destination. Price and timing follow from the drawing: part size, feature density, thickness and finishing route each change the etching and handling time. Every shim is produced to the customer’s own specification, so this page describes the process rather than a fixed offer.