Photoengraving also known as photo-chemical milling is a process of engraving using photographic techniques. The most common type of photoengraving involves using a material that is photosensitive and resistant to acids or other etching compounds. This material, called a photoresist, is applied to a metal to be engraved. It is then exposed to light (usually strong ultraviolet) through a photographic negative causing it to harden where the negative allows light to pass. The photoresist is then developed by washing in a solvent that removes the unhardened parts. Finally, the metal to be engraved is exposed to an acid or other etching compound which dissolves the exposed parts of the metal. Photoengraving is used to make printed circuit boards, printing plates, foil-stamping dies and embossing dies. It is also used to make nameplates, presentation plaques and other decorative engravings. A similar process called photolithography is used to make integrated circuits. Engraving is the practice of incising a design onto a hard, flat surface, by cutting grooves into it. ... Photosensitivity is the amount to which an object reacts upon receiving photons of light. ... It has been suggested that this article or section be merged with resist. ... Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. ... Photography is the process of making pictures by means of the action of light. ... Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ... A stamp is a distinctive mark or impression made upon an object, for instance those made on a piece of paper and used to indicate the prepayment of a fee or tax. ... A die is a tool used in the manufacturing industry to create a wide variety of products and components. ... This article or section does not cite its references or sources. ... Photolithography is a process used in semiconductor device fabrication to transfer a pattern from a photomask (also called reticle) to the surface of a substrate. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ...

One method of photoengraving produces a shallow depression in the metal. This is used for intaglio printing plates or for decorative purposes. It is also the same method used for printed circuit boards. The engraving is ususlly made in copper or brass. The process can be done in open trays but is much more effective if the etchant (often ferric chloride) is sprayed onto the metal. If ferric chloride is used as the etchant no metal parts other than titanium can be used in the etching equipment. Decorative engraving will often be spray-painted then sanded to remove the paint from the raised parts of the engraving. Intaglio is a printmaking technique in which the image is incised into a surface. ... Iron(III) chloride, generically called ferric chloride, is an iron-based salt of chemical formula FeCl3. ...

Another method produces a deep engraving with sloped shoulders. In this method the metal (usually zinc or magnesium) is held face-down and a mixture of nitric acid and a soap-like oil is splashed onto it. As the acid etches the surface the oil adheres to the edges of the exposed area. This progressively reduces the area being etched resulting in a sloped edge; a single dot will end up as a cone-shaped mound protruding from the etched area. This method is used for printing plates (the shoulder supports the printing surface), foil stamping dies and embossing dies. Decorative engravings made by this method may go through a second process to produce a decorative background. The raised parts and their shoulders are painted with an etchant-resistive material and a pattern of etchant-resistive material is applied to the deep parts of the engraving. The resist for the background may be another photoengraving or may be randomly splashed-on. The engraving is etched again for a shourt time to produce a raised pattern in the background. Decoragive engravings of this type may also be spray-painted and sanded as in the previous method. General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... The chemical compound nitric acid (HNO3), otherwise known as aqua fortis or spirit of nitre, is a colorless, corrosive liquid, a toxic acid which can cause severe burns. ... Soap most commonly appears in bar form. ... This article or section does not cite its references or sources. ...

See also

• Photogravure