Metal etching, also referred to as metal engraving, is the process of creating grooves, fine lines or impressed designs on metal parts or sheets. There are a number of different methods with which to achieve the desired pattern or finish on a metal part; the most common of these methods are mechanical or chemical machining or acid etching.
Traditionally, etching was performed by hand; hand engraving was implemented by using a fine tipped tool such as a burin to etch metal according to a desired pattern. This results in a unique and almost unrepeatable image being created although it is a time-consuming process. Today however, more commonly used techniques include chemical etching, photo etching or photofabrication and other processes such as stamping, laser engraving and water-jet cutting which are faster and more accurate than hand engraving. Laser etching is able to create very fine, clean lines in surfaces with little need for secondary finishing. Electro discharge machining, or EDM, is another method of metal etching which is able to achieve close tolerances. During the process, the metal part is exposed to streams of corrosive electromagnetic discharge. Any resulting imperfections, burrs or marks may be smoothed and polished away after the metal has been etched. It is a very versatile procedure and almost all metals can be processed using chemical milling, photo engraving or mechanical etching including: aluminum, brass, copper, nickel and stainless steel.
A popular method for metal etching is the use of chemicals, acids and bases as a reagent on surface of the metal part or plate. Using the process of masking and corrosive chemical exposure to create grooves, images, lines and holed surfaces, acid etching is able to achieve precise lines and specific depths. First, the metal sheet to be etched must be stripped of all oils and chemicals. Cleansers such as alkaline cleaners are used to strip organic materials, followed by an acid cleaner to remove chemical residue; neither of these cleansers can be too strong, or the polished surface of the metal will be scratched. Next, a masking is applied to the entire surface. Masking types are often tapes or paints, elastomers (rubber) or plastics. A pattern is cut into the masking in the same shape the metal is to be cut, then the cut masking is removed from the areas to be etched, and the chemical, or "reagent", is applied. After the acid has achieved its desired etch, both the reagent and the remaining photoresist are stripped from the metal part to reveal the final design. The length of time a chemical is allowed to react with a metal part depends on the desired depth of the grooves, and the strength of the acid. An understanding of chemicals and their corresponding characteristics is necessary to successfully implement chemical etching.
Mechanical milling, a common method used for metal etching, uses a lathe or CNC machine with fine tips which are able to process a range of materials and dimensions, including straight or curved surfaces. The computer of these machines controls the laser's or cutter's direction, pressure and speed resulting in a precise image or design with clean, fine lines. This method achieves precise and consistent results, but the initial tooling costs are high, and maintenance of the machines requires qualified personnel. Milling and grinding machines are also used to achieve certain etching finishes on metals, especially on larger sheeting used for architectural decorative or furniture purposes. A wide range of manufacturing options are available with these methods which are precise, accurate and repeatable. For some smaller processes and more intricate, decorative purposes, hand engraving is still used however it is restricted to a few narrow fields, but is still seen in jewelry, firearms, small decorative pieces and some musical instruments. Engraving or etching by machine and mechanical tools is more common. Widely available engraving machines are fairly simple to use and are able to engrave a number of surfaces such as metal, glass or plastic. Diamonds are typically used as the stylus, especially for machines required to engrave on harder materials and metals. Engraving equipment consists of three parts: a stylus or marking tool, a controller, and a surface
A variety of industries use methods of metal etching or acid etching for different purposes. Decorative uses include jewelry, firearm and musical instrument decoration, plaques, trophies and awards, as well as larger decorative purposes for architecture and furniture especially using stainless steel etching. For decorative etching, the surfaces are sometimes smoked so that the lines will be more visible. Industrial uses include stencils, printing plates, foil-stamping dies and more. Other industries requiring precision parts, such as the medical field, also use metal etching and chemical machining in order to achieve the desired fine finish on parts and components such as stents, cathodes and implants. Metal etching can also be used to help a metal part meet restrictive weight demands by removing a surface layer of a part through chemical or mechanical means. Metal etching services also create longer lasting stencils for the woodworking and art fields, printed circuit boards for the aerospace and electronics industries, and engraved or reduced missile skin panels and jet frames for defense.
Metal Etching Companies - Great Lakes Engineering, Inc.
Metal Etching Companies - VACCO Industries, Inc.
Metal Etching Companies - VACCO Industries, Inc.
Metal Etching Companies - United Western Enterprises, Inc.
Metal Etching Companies - United Western Enterprises, Inc.
Metal Etching Companies - Tech-Etch, Inc.
In metal etching, a subtractive industrial process and various etching chemicals or etchants are used to give a desired shape to metal. The process originally originated from armor decoration, when suits of armor were deemed important personal possessions.
During the metal etching process, a metal sheet is covered in a masking compound in a predetermined way, and the metal is bathed in a corrosive chemical known as an etchant. The etchant chemically reacts with the exposed material, without any masking material, and cuts the exposed material by dissolving it. The masking compound is usually inert. This process is also known as chemical milling or chemical machining.
With metal etching, cuts with varying depth are achieved, and the depth is determined by the time spent by the material in bath. The rate of etching is defined by the ratio of depth of cut to time spent in the bath. Many factors, such as the material to be etched, temperature, the etchant composition and concentration determine the rate. As there are number of factors that can influence etching, the common practice is to do a test run, where a material is exposed to chemicals and monitored for output performance. Based on the process performance, the chemistry and test are repeated until a desired depth and rate are achieved.
What is a standard metal etching process?
The first stage is cleaning, which is done at preparation stage. At this stage, you should ensure that the surface to be etched is contaminant free. If contaminants remain, they can alter the reaction and result inconsistent etching. For metal surfaces, solvents are used, which commonly incudede-oxidizing and alkaline solutions. Typical contaminants include grease, primer coatings, residue from the marking step, and oils.
Typically, in industrial settings, the masking material or maskants, include isobutylene-isoprene copolymers and neoprene elastomers, which are inert in nature and do not lose their structural integrity during chemical reactions. In the masking stage, these polymers are applied on the surface in a predetermined fashion that gives the required pattern. Masking can be done through either dipping or flow coating. In dip masking, the parts are immersed into maskant, whereas in masking by flow coating, the parts are coated by flowing the solution over a surface.
This is the stage where the chemical reaction takes places, as metal parts are immersed into corrosive material. The parts remain in a tank for a specified period to achieve definite width. There are numbers of factors that determine the width, and these have been discussed above.
This stage is also called demasking whereby products of the reaction and maskant are removed from asurface to reveal the desired pattern and design. A specific procedure is followed to remove etchants from parts. Typically, cold water is used for specific etchants and specialized processes, such as a de-oxidizing bath. The de-oxidizing bath removes the oxides left by the chemical reaction. Similarly, ranges of methods are utilized to remove the maskant; however, commonly, maskant is removed manually with the help of scraping tools.
When specific design configurations are required for metal, metal etching is used and can be either wet or dry, based on the etchant used for dissolving the metal. Etching via chemicals is similar to chemical milling, but the depth and rate of metal etching achieved is significantly greater in chemical milling.
Etching can be isotropic and anisotropic. When an etchant removes material in all directions uniformly, the etching achieved is isotropic. Conversely, when the removal is achieved in vertical direction, it is called anisotropic etching. Additionally, anisotropic etching can be completely anisotropic and partially anisotropic. Commonly, anisotropic dry etching achieves etching with a higher aspect ratio and finer resolution in comparison to isotropic etching.
When an etchant is in liquid form, the metal etching is called wet. The patterns that are required to be saved are masked, and the exposed material is etched away by liquid etchant. Lithography is used before the fabrication step to mask the patterns and configuration.
In wet etching, multiple chemical reactions take place, as the original reactants are consumed and new reactants are produced.
The wet etching process can be simplified in three steps:
When Silicon is used to etch anisotropic shapes, the common wet etching agents include ethylenediamine pyrocatechol (EDP), potassium hydroxide (KOH), and tetramethyl ammonium hydroxide (TMAH). However, in isotropic wet etching of Silicon, acetic acid, nitric acid, and hydrofluoric acid are used in combination. The rate of etching is defined by the concentration of etchants.
For achieving dry metal etching, instead of a solution, plasma or gas is employed to remove the material. The kinetic energy of particle beams, which is usually high, and the chemical reaction, or the combinations of these, etch the material.
Dry metal etching is further categorized as physical or chemical based. In physical dry etching, the kinetic energy of ions, electrons, or photons etch the substrate. In this type of etching, no chemical reaction is involved and particles kick the atoms out while the material evaporates.
Chemical dry etching or vapor phase etching, as their names imply, involve chemical reactions to attack a silicon surface. The chemicals that are usually utilized for dry etching are fluorine, tetrafluoro methane, nitrogen trifluoride, sulfur hexafluoride, and chlorine gas.
As mentioned before, physical and chemical metal etching can also be in a combination and is called reactive ion etching. The reactive ion etching is the most extensively used technique in industrial settings as well as in labs. As both actions are used, the etching process is more rapid than normal. The process involves positively charged ions, which are produced from the reactive gases. The cations are exposed to the substrate at high speed, which then react chemically with the silicon.
Etching, with little alteration in technique, has applications in a wide range of industries, from fabrication of micro-electromechanical systems to aerospace components, to printing circuits to the production of missile skins. However, this ever evolving technology was first widely employed back in ancient times.
Etching mainly evolved for aesthetic applications where soft metals, such as copper and zinc, and later strong metal, like steel, were etched with the use of strong acids. Typically, armors, guns, plates and cups were etched to add aesthetic elements.
During the 16th century, etching made had its major effects on modern life when it was applied to printmaking in Germany. In printmaking methods, a metal plate was covered in acid-resistant material-typically wax. An artist then scraped the wax and exposed the metal to create a printing die using a pointed etching needle. After elaborate scraping, the plate was bathed in an acid or etchant. The acid dissolved a part of the metal where it is exposed, and it resulted in to metal plate with sunken lines and words. The metal plates were then inked and used, in large scale, for printing purposes. The process resulted in the production of printing dies that started the printing revolution, which brought Europe toward an industrial revolution.
At the same time, etching developed as an alternative to metal engraving, which at that time was a preferred method to produce patterns on metal. Soon, chemical etching was used to put trajectory information onto artilleries and canons, as etched plates were found to be very durable. Following this trend, milling or etching was applied to equipment, stiletto daggers, and shovels.
The next milestone in chemical milling was achieved in the 18th century, when a Swiss botanist, John Senebier, observed that certain plant resins, after being exposed to light, hardened and lost their solubility to turpentine. This piece of information led to development of present day photochemical etching. However, for almost a century, this method was only used in photography. A resin, which resists acid action, was applied in liquid form to the metal and exposed to light to outline the masked area. Using this method, impressions on metal plates were obtained.
The modern commercial use of photochemical machining came into existence in 1927. A Swedish company, Aktiebolaget Separator, developed this method for producing edge filters. The method was patented, and the technique was used to cut gaps filters. Around the beginning of the Second World War, the method got traction and was widely applied to machine hard metals. With the use of photochemical etching techniques, metal could be etched from both sides, and was extensively applied to make components from sheet foil.
Etching technology was later developed to support micro-fabrication, which served as the basis for the information technology revolution.
- Lines that are partially etched into the surface of the metal, which aid in the bending of the part in a subsequent operation.
- The process of heating a developed photoresist image until the resist coating becomes chemically resistant.
- A term originally used to refer to the process of photo chemical machining (PCM).
- A process in which ferric chloride acid is regenerated to maintain high quality acid for the etching process.
- The dipping, rolling, spraying, laminating, spinning, printing or flowing of the substrate surface layer of a photoresist material in order to cover it with a resist.
- A photographic process in which an image is transferred from one substrate to another.
- The subjection of a substrate surface to high temperatures or the pickling process in order to improve photoresistant adhesion.
- Photoresist in the form of rolled sheet laminate.
- Designing artwork for parts to be photochemically machined so that all shapes are outlined with a controlled line to be etched.
- An acid used to dissolve a layer of metal to form the component.
- A series of etched parts that are tagged into a frame. Blanks usually have several frets etched into them.
- Non-metallic elements fluorine, chlorine, bromine and iodine.
- An image etched/sunk into the surface of a piece.
- An electrically charged atom or group of atoms, the electrical charge of which results from a neutral atom or group of atoms losing or gaining one or more electrons.
- A photoresist applied to the substrate by dipping, roller coating or spraying.
- A device that receives optical power and changes it into an electrical signal.
- A material that, when applied to any of a variety of substances, becomes sensitive to portions of the electromagnetic spectrum and, when properly exposed and developed, masks a portion of the material.
- The rate of response of a photographic material to a particular range of the electromagnetic spectrum.
- A structure that underlies and supports or forms base material on which coatings are applied.
- Invisible electromagnetic radiation.