How are half-etched depth features specified on custom metal etching drawings?

Half-etched depth features on custom metal etching drawings are specified by defining the etched side, target depth or remaining thickness, feature boundaries, depth tolerance, and measurement basis in a way that can be interpreted consistently during photochemical etching tooling and production. Because chemical etching removes material from exposed areas, a half-etch feature is not just a 2D shape; it is a controlled recess that depends on sheet thickness, material behavior, etch direction, artwork layout, and process controls. The most important drawing element is etch direction. The drawing should explicitly label which surface is the reference side and use section views, leader notes, or side-view symbols to show whether material is removed into the A-side, B-side, or both. If the part has functional assembly orientation, such as a shim step, logo cavity, bending groove, fluid channel, encoder track recess, or electrical contact step, the reference surface must match the actual assembly direction. Otherwise, a visually similar recess may be produced on the wrong face and become nonfunctional. Depth should be specified as either a target etch depth or a target remaining material thickness, but not left as a vague “half etch.” For example, a note may state “0.05 mm single-side etch depth from top surface” or “remaining thickness 0.08 mm after etching from bottom side.” When possible, define remaining thickness for functional features because that value often directly relates to stiffness, electrical performance, sealing, bending behavior, or step height. If depth is specified instead, the nominal starting sheet thickness must also be clearly stated, because the same etch depth on different base thicknesses produces different remaining material. Engineers should avoid calling out “50% etch” without a numerical value, since actual sheet thickness variation and process response can make percentage-based notes difficult to inspect. Half-etched areas should be visually distinguished on the drawing. If through-etched openings, full-thickness features, and half-etched areas appear on the same part, each feature type should be distinguishable without relying on verbal explanation. Labeling the function of the recess helps manufacturing and quality teams apply the right process and inspection focus. Tolerances for half-etched features should be separated into at least three categories: planar dimensions of the etched opening or recess, depth or remaining-thickness tolerance, and location relative to datums. A recess that is correctly located but too deep may weaken the part, while a recess with correct depth but poor position may fail assembly. If the feature has a critical bottom radius, wall slope, or edge break, that should also be noted. Photochemical etching produces burr-free edges, but half-etched sidewalls are not perfectly vertical; the transition from the unetched surface to the recess floor will have a process-related profile. If a sharp corner, flat floor, or specific surface appearance is required, it should be marked as critical and reviewed against etching process capability. Material and sheet thickness must be stated on the same drawing or accompanying specification. INNOETCH works with stainless steel, copper, nickel, molybdenum, aluminum, and other thin metal materials, and each material etches at a different rate and can produce different recess profiles. Half-etch behavior also changes with material temper, rolling direction, surface condition, and thickness range. A depth note that works for one alloy may not transfer directly to another, so material callouts should include alloy, temper if relevant, and nominal thickness. If the part uses a specific stock material with known thickness variation, that information helps set realistic depth and remaining-thickness requirements. Drawings should also define the inspection method or acceptance basis where depth is functionally critical. Common verification points include micrometer or thickness-gauge measurement over the recessed area, optical measurement of feature position, cross-section checks during engineering approval, and visual comparison for noncritical decorative marks. If the part requires first-article approval before production, the drawing note should identify which half-etched dimensions are reportable. Certain feature types need additional notation. Half-etched bend lines or hinge lines should indicate bend direction and whether the recess is on the inside or outside of the bend. Half-etched channels or fluid-control features should state whether depth consistency across the part is critical to flow or sealing. Half-etched steps in precision shims or mechanical parts should define the mating surface and any step-height requirement. Encoder discs, lead frames, speaker grilles, filter mesh, and other precision components may combine through holes and half-etched areas on the same component; in those cases, datum structure and feature priority should be clear. A practical drawing checklist for half-etched features includes: reference side or etch side clearly marked; numerical depth or remaining thickness; nominal material thickness and material type; separate layer or hatch for each half-etch side; section views for ambiguous features; datum references for location; tolerance for depth, size, and position; surface or edge requirements where critical; and any functional notes such as bend line, logo, channel, step, or assembly orientation. When samples are available, they can help communicate intended appearance and function, but samples should not replace dimensional specification. A reference sample can show surface contrast, recess feel, or bend behavior, while the production drawing should define measurable requirements. If a customer provides a sample without a drawing, engineering review can identify feature locations and estimate depth, but formal production should still be based on approved drawing data. INNOETCH supports custom etched metal components based on customer drawings, samples, materials, dimensions, and application requirements, including prototype development, design optimization, production, and quality support from sample projects to mass production. For half-etched parts, engineering review focuses on whether depth notation is manufacturable, whether feature geometry is compatible with photochemical etching, and whether inspection requirements are clear before quotation and production planning. For quotation and design review, customers should provide the drawing file, material specification, nominal thickness, all half-etch depth requirements, tolerance expectations, quantity, and application notes. If depth features are critical, it is helpful to identify which dimensions are functional and which are cosmetic. For project review, drawings, material specifications, dimensions, tolerances, quantity and application requirements can be sent to nico@innoetch.com.