General Process & Basics
Photochemically etched parts retain the complete, unaltered tensile strength and mechanical properties of the base metal from which they are manufactured. Unlike mechanical processes such as stamping that subject metal to extreme localized forces, or thermal processes like laser cutting that expose material to intense heat, photochemical etching removes material through a controlled chemical reaction that introduces absolutely zero mechanical stress into the remaining material.
The result is a finished part whose strength, ductility, fatigue resistance, and other mechanical properties remain identical to those of the original sheet metal. There is no work hardening, no micro-cracking, no residual stress, no heat-affected zone, and no alteration of the metal’s grain structure. For applications where material properties directly affect performance, reliability, and service life, this complete preservation of base metal characteristics provides engineering advantages that are difficult or impossible to achieve through alternative manufacturing methods.
When metal undergoes plastic deformation in stamping, punching, and shearing operations, the crystalline structure is mechanically disrupted. The metal grains are compressed, elongated, and distorted by the forces applied, changing the material’s properties in ways that can be problematic for many applications.
Similarly, when metal is exposed to intense heat in laser cutting or thermal processes, the elevated temperature causes phase transformations, grain growth, oxidation, and changes to mechanical properties. Rapid heating and cooling cycles create thermal gradients that induce residual stresses.
Photochemical etching operates differently. The chemical etchant dissolves metal atoms through an electrochemical reaction at controlled, moderate temperatures, typically between 100 and 150 degrees Fahrenheit (40 to 65 degrees Celsius). These temperatures are far below any transformation temperatures for common metals and alloys. The removal occurs atom by atom with no force applied to the bulk material, no shock loading, and no thermal spike.
Stamping creates parts by shearing metal between a punch and a die, subjecting the metal around the cut perimeter to extreme localized stress and plastic deformation. The shearing action creates distinct zones including rollover, burnished, and fracture zones, plus burrs extending beyond the nominal edge.
Within these zones, the metal has been work hardened through severe plastic deformation. Work hardening increases the dislocation density within the metal’s crystal structure, making the metal harder and stronger in the deformed region but simultaneously causing it to lose ductility and become more brittle.
In parts subject to cyclic loading, bending, or flexing, the work-hardened edge region becomes a potential site for fatigue crack initiation. Springs, flexures, diaphragms, and other components experiencing repeated deformation are particularly vulnerable to fatigue failures originating at worked edges. The micro-fractures and surface roughness also serve as stress concentration sites that can initiate cracking under load.
Laser cutting involves melting or vaporizing metal with an intensely focused beam, inherently creating thermal effects in surrounding material. The heat-affected zone (HAZ) typically extends from a few thousandths of an inch to 0.020 inches or more from the cut edge.
Within the HAZ, grain growth can reduce strength and toughness. Phase transformations may create hard, brittle structures or softer, weaker phases. Precipitation-hardened alloys may experience strength reduction. Residual stresses develop that can promote distortion or cracking. For thin materials, thermal distortion becomes a significant concern, often causing warping and dimensional instability.
Photochemical etching’s chemical material removal avoids all of these mechanical and thermal degradation mechanisms. The etchant dissolves exposed metal through an electrochemical oxidation-reduction reaction with no force transmitted to adjacent material and no significant heat generation.
The tensile strength, yield strength, elongation, hardness, fatigue resistance, and all other mechanical properties of a photochemically etched part are identical to those of the starting material. This allows designers to select materials based purely on required properties without needing to account for process-induced property changes.
The edges of photochemically etched features are smooth and burr-free, with no work-hardened layer, no micro-cracks, and no stress concentrations from rough surfaces. While chemical etching produces a slightly tapered edge profile, this taper is smooth and gradual, without abrupt changes in cross-section that concentrate stress.
Springs and elastic elements benefit significantly from preserved material properties. Testing has shown that photochemically etched springs can achieve fatigue lives exceeding those of stamped counterparts by factors of two to ten depending on the specific design and loading conditions.
Shims and spacers used for precision gap control maintain dimensional stability and flatness. The residual stresses from stamping or thermal cutting can cause distortion over time, while photochemically etched shims remain flat and dimensionally stable throughout their service life.
Electrical contacts and connectors maintain consistent conductivity and reliable spring force. Medical devices benefit from pristine surface conditions and unchanged metallurgical states. Aerospace components maintain certified material properties, simplifying qualification processes.
The preservation of material properties has been extensively documented through mechanical testing. Tensile tests show stress-strain curves identical to parent material. Hardness measurements show no gradient across etched edges. Fatigue testing confirms edges are not preferential failure sites. Metallographic examination reveals grain structures identical to base material with no deformed zones.
Engineers can design to published mechanical properties without applying derating factors for edge effects. For applications where edge condition is critical, photochemical etching may enable thinner materials or more aggressive designs than would be possible with processes that degrade edge properties.
Photochemically etched parts retain all carefully engineered mechanical properties of the base material without the work hardening, micro-cracking, heat effects, and stress concentrations that reduce the effective strength and reliability of parts produced through mechanical or thermal processes.
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