General Process & Basics
Photochemical etching, also known as photochemical machining (PCM), chemical etching, or photo etching, is a highly precise subtractive manufacturing process that uses chemistry rather than force to remove metal. Unlike traditional machining methods that rely on cutting tools, stamping dies, or lasers, photochemical etching dissolves unwanted metal through a carefully controlled chemical reaction, producing intricate metal parts with exceptional accuracy and zero mechanical stress.
At its core, photochemical etching works on a beautifully simple principle: protecting the areas of metal you want to keep while chemically removing everything else. The process transforms a flat sheet of metal into complex components featuring holes, slots, intricate patterns, and precise geometries, all without ever touching the material with a cutting tool.
The magic lies in the photoresist, a light-sensitive coating that acts as a protective barrier. When exposed to ultraviolet light through a patterned phototool (essentially a high-resolution photographic negative of your design), the photoresist undergoes a chemical change. Depending on whether positive or negative photoresist is used, either the exposed or unexposed areas become soluble and can be washed away during development, leaving your desired pattern perfectly transferred onto the metal surface.
The process begins with sheet metal (typically stainless steel, copper, brass, nickel, aluminum, or specialty alloys) cut to the appropriate size. The metal surface must be meticulously cleaned to remove any oils, oxidation, or contaminants that could interfere with photoresist adhesion. Even microscopic imperfections at this stage can compromise the final result.
A thin, uniform layer of photoresist is applied to both sides of the metal sheet through various methods including lamination, spraying, or dipping. The coating must be completely even, as any variation in thickness will affect etching accuracy. Modern photoresists are engineered for specific metals and applications, offering exceptional resolution and chemical resistance.
The coated metal is sandwiched between two phototools (one for each side) and exposed to high-intensity UV light. The phototools are created directly from your CAD data, ensuring that what you design is exactly what you’ll manufacture. The UV exposure time is carefully calibrated based on the photoresist type, metal thickness, and desired feature resolution. This is where the design becomes permanently registered onto the metal.
After exposure, the metal enters a developing solution that selectively removes either the exposed or unexposed photoresist (depending on the resist type). What remains is a precise chemical-resistant mask that perfectly replicates your design pattern. The unprotected metal is now vulnerable to the etchant, while the masked areas remain completely protected.
The developed metal sheet is conveyed through a spray etching chamber where a chemical etchant (most commonly ferric chloride for stainless steel or cupric chloride for copper alloys) is atomized and sprayed onto both surfaces simultaneously. The etchant reacts with and dissolves the exposed metal atoms, progressively removing material until it etches completely through the sheet thickness. The etching rate is controlled by factors including etchant concentration, temperature, spray pressure, and conveyor speed. Advanced etching systems maintain precise control over these variables to ensure consistent results across the entire sheet.
Once etching is complete, the parts move to a stripping station where the remaining photoresist is chemically removed, revealing the finished metal components. A final cleaning process removes any residual chemicals, leaving parts that are ready for immediate use or subsequent finishing operations.
The chemical nature of photochemical etching delivers advantages that mechanical processes simply cannot match. Because no cutting tools contact the material, there are no burrs to remove; edges emerge clean and smooth. The process introduces zero mechanical stress, meaning thin materials won’t distort and delicate features remain dimensionally stable. Material properties remain unchanged; there’s no heat-affected zone altering the metal’s temper, hardness, or grain structure.
Perhaps most significantly, photochemical etching replicates your CAD design with remarkable fidelity. Complex geometries that would require expensive progressive dies or multiple machining setups are produced in a single operation. Changes to the design require only new phototools, not retooling expensive dies or reprogramming lengthy CNC operations. This makes photochemical etching exceptionally cost-effective for prototypes, low-to-medium production volumes, and parts with intricate details.
The atom-by-atom material removal through controlled chemical reaction enables extraordinary precision without the work hardening, micro-cracking, residual stress, or thermal effects that plague mechanical and thermal cutting processes. For applications where material properties directly affect performance, reliability, and service life, this complete preservation of base metal characteristics provides engineering advantages that can be difficult or impossible to achieve through alternative manufacturing methods.
From electronics and aerospace to medical devices and automotive applications, photochemical etching continues to be the manufacturing method of choice when precision, repeatability, and material integrity matter most.
4020 Jeffrey Blvd. | BUFFALO, NY 14219
P: (716) 821-9393 / (800) 875-1093
Website by Luminus
