Photochemical etching, also known as photo etching or photochemical machining, is a process used to manufacture many different kinds of sheet metal products. Parts are fabricated by precisely exposing sheet metal to high intensity light and acidic chemicals. Due to the unique features of this process, photochemical etching provides a precise and economical option for industrial metal etching.
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Benefits of Photo Etching
Unlike mechanical etching methods, photo etching does not produce sharp edges or burrs, and it leaves the physical properties of the metal unchanged. The process works well with practically any metal and works most effectively on metal sheets between 0.0005 and .080 inches in thickness. Another advantage to photochemical etching is its relatively lower cost. The real savings come in the form of reduced tooling costs. Phototools are substantially less expensive than mechanical tools, and it takes significantly less time to create them. This makes photochemical machining a particularly good option for prototyping as changes can be made quickly and affordably. In addition, since the phototool is only exposed to light, maintenance and repair costs are practically eliminated. For quick turnaround on precision etching, photochemical etching provides a reliable and economical solution.
Photochemical Etching Process
As its name suggests, photochemical etching utilizes light and chemical reactions to remove material, which means that it will require a very different procedure than mechanical etching processes. Instead of using a cutting tool, photo etching uses what is called a phototool. Using CAD software, engineers create negative images of the sheet metal parts they wish to create. These negative images are then printed on two sheets of photographic film. The phototool consists of these two printed film sheets. Once the phototool is ready, the sheet metal is thoroughly cleaned and laminated on both sides with a layer of light sensitive film called a photoresist. After lamination, the metal sheet is placed between the two halves of the phototool and exposed to high intensity UV light. The phototool ensures that only certain parts of the metal surface are exposed to the UV light. The photoresist in these exposed areas hardens, while the hidden areas remain soluble. A developing solution washes away the soluble photoresist film, leaving sections of hardened film on the surface of the metal. After the metal is developed, the sheet is placed on a conveyor which passes through an etching machine. The etching machine contains spray nozzles above and below the conveyor, and each sprays a heated solution of acid onto the two surfaces of the sheet metal. As the acid comes in contact with the unprotected metal surface, it quickly corrodes away the metal. Once the sheet metal exits the machine, all that remains is the desired parts which were protected by the photoresist. Finally, the parts are rinsed, and the rest of the photoresist is removed.
Applications of Photo Etching
The photo etching process is utilized in a diverse range of applications and industries due to the many benefits it provides. Photochemical etching has the capability to produce small and complex parts with great precision, making it ideal for use in the electronics and hardware industries. Common products manufactured using photochemical machining include fine screens, metal gaskets, sensors, circuit components, washers, apertures, and more.