What is Metal Etching
Metal etching is a metal removal process that uses various methods to configure complex, intricate, and highly accurate components and shapes. Its flexibility allows for instantaneous changes during processing. Since there is a limited amount of force or heat during the process, the properties of the etched material remain unaltered, which leaves workpieces free of stress or imperfections.
Etching is an ideal process for producing components with thicknesses of 0.0005 into 0.05 in or 0.00127 cm to 1.27 cm, which makes it a highly viable method for manufacturing small parts at exceptionally low cost
Metal Etching Processes
The process of metal etching is the removal of excess material from a workpiece using a chemical reaction. It is a method for shaping metals that have existed for hundreds of years. Metal etching began as a method for making weapons, household tools, and jewelry. The modern use of etching has paved the way for creating precision parts for aircraft, automobiles, and satellites.
Unlike other metal working processes, metal etching is fast, exceptionally accurate, and highly reliable. The tools used for etching have minimal wear and tear due to the low mechanical stress of the process.
The different types of etching include acid, photochemical, laser, and electrochemical. Acid metal etching is done in an acid bath, dipping, or flow coating. Photochemical etching uses light and chemicals to remove material. Laser etching melts the surface of the workpiece. Electrochemical etching uses a sodium-based solution with electrical pulses to remove material from the substrate.
Wet etching refers to etching processes that use chemicals or etchants to remove materials in a specific pattern defined by photoresist masks where material not covered by the mask is removed or etched away. Basic wet etching
involves diffusion of the etchant, a reaction between the etchant and the material, and diffusion of byproducts. It is an isotropic process that produces a reaction on all areas of a metal’s surface.
Acid Metal Etching
Metals That Can Be Acid Metal Etched
The type of metal to be etched influences the acid etching process since some metals etch quicker than others. Nickel and steels take far longer to etch than softer metals such as bronze or copper.
Any metal can be etched, with attractive metals being the most popular due to their characteristics and properties. Common metals used in etching are:
Titanium – light and strong with excellent fatigue properties
Aluminium – strong, lightweight, excellent weight ratio, and corrosion resistance
Copper – soft metal, thermal properties, electrical conductivity, etches quickly
Nickel – resistance to heat and corrosion, used as an alloy
Stainless Steel – corrosion resistant The 300 series is difficult to etch. The 400 series stainless steel is easier to etch but does not have corrosion resistance.
Bronze – ductile, machinability, harder than copper, stiff, and firm
Molybdenum – high strength, thermal properties, electrical conductivity, and low thermal expansion
The Acid Metal Etching Process
Cleaning the Metals
For a metal to be acid etched, it must have any contaminants, particles, oil, or chemicals removed from the surface. Solvents, deoxidizing agents, and alkaline solutions are commonly used. Cleaning is a necessary step in the preparation process to ensure that the surface is properly prepared.
Cleaning is necessary to ensure the film or screen printing ink has good adhesion to the metal surface. Any oil stain or oxide film must be completely removed with degreasing determined by the type of oil stain.
The maskant, or masking agent, is applied to the surface of the workpiece. It contains inert substances such as isobutylene isoprene copolymers and neoprene elastomers, which do not lose their structure when exposed to a chemical reaction.
The maskant can be applied by dipping or coating, where dipping includes immersing the workpiece and coating flows the maskant over the surface. The success of applying the maskant depends on how well the workpiece has been cleaned.
Image Impression on the Metal
The application of the image can be completed in several ways. In one process, the pattern for the component is carved into the maskant coating. Some applications use the maskant agent as the method for shaping the image. In either
case, the image is placed on the metal sheet.
When the image is carved into the maskant, the image is recessed. When the maskant agent shapes the image, the effect is the opposite, producing a raised image.
Acid Etching the Metal Piece
The etchant or acid is applied once the image is emblazoned on the maskant. The methods for applying the acid can be spraying it onto the workpiece or immersing it in an acid bath. The acid or chemical that is normally used is ferric chloride, a form of corrosive material. The time that the workpiece is exposed to the etchant depends on the type of metal and the intricacies of the piece being produced.
As seen in the image below, the image has been carved into the maskant, and the workpiece is lowered into the acid bath, where the exposed portions of the metal will be removed.
In the removal process, the maskant and etchant are washed off the workpiece to reveal the final part. A variety of solutions and solvents are used such that the workpiece is not damaged, but the materials are removed. In some cases, depending on the resilience of the workpiece, the maskant can be scraped off.
A common method for removing the etchant is to bathe the workpiece in water. A deoxidizing bath may be required to remove oxides from the surface as a secondary measure. Though deoxidizing may not be necessary, it is a process that should be used with all acid etchings.
Photochemical Metal Etching
Utilizing Computer Aided Design (CAD)
The process of photochemical metal etching begins with creating a design using CAD or Adobe Illustrator. Although the design is the first step in the process, it is not the end of computer calculations. Once the rendering is finished, the thickness of the metal is determined, as well as the number of pieces that will fit on a sheet, a necessary factor for lowering the cost of production. A second aspect of the sheet’s thickness is determining part tolerances, which hinge on the part dimensions.
Utilizing Adobe Illustrator
Etching companies also use Adobe Illustrator to create their designs. Artists and designers use it to create vector graphics, which have been used for design purposes for over thirty years. Adobe Illustrator has digital drawing tools to produce illustrations, logos, and artwork.
During the design process in Adobe Illustrator, careful consideration is given to the type of material to be etched and the depth of the cuts allowing for the size of the kerf. The finished design is sent from Adobe Illustrator to the etching machine.
As with acid etching, the metal must be thoroughly cleaned before being processed. Each piece of metal is scrubbed, cleaned, and cleansed using water pressure and a mild solvent. The process eliminates oil, contaminants, and tiny particles. This is necessary to provide a smooth, clean surface for the application of the photoresist film to adhere securely.
Laminating Metal Sheets with Photoresistant Films
Lamination is the application of photoresist film. The metal sheets are moved between rollers that coat and evenly apply the lamination. To avoid undue exposure of the sheets, the process is completed in a room lit with yellow lights to prevent UV light exposure. Proper alignment of the sheets is provided by holes punched in the edges. Bubbles in the laminated coating are prevented by vacuum sealing the sheets, which flattens the laminate layers.
During photoresist processing, the CAD or Adobe Illustrator rendering images are placed on the layer of photoresist on the metal sheet. The CAD or Adobe Illustrator rendering is imprinted on both sides of the metal sheet by sandwiching them over and under the metal. Once the metal sheets have the images applied, they are exposed to UV light that places the images permanently. The photoresist becomes firm and hardens when the UV light shines through the clear areas of the laminate. Black areas of the laminate remain soft and uninfluenced by the UV light.
Developing the Sheets
From photoresist processing, the sheets move to the developing machine that applies an alkali solution, mostly sodium or potassium carbonate solutions, that washes away the soft photoresist film, exposing the parts to be etched. The process removes the soft resist and leaves the hardened resist, which is the part to be etched. In the image below, the hardened areas are in blue, and the soft areas are gray. The areas not protected by the hardened laminate are exposed metals that will be removed during etching.
Etching on a Conveyor
Much like the acid etching process, the developed sheets are placed on a conveyor that moves the sheets through a machine that pours etchant on the sheets. Where the etchant connects with the exposed metal, it dissolves the metal leaving the protected material.
The etchant is ferric chloride sprayed from the conveyor’s bottom and top in most photochemical processes. Ferric chloride is chosen as an etchant because it is safe and recyclable. Cupric chloride is used to etch copper and its alloys.
The etching process must be carefully timed and controlled under the metal being etched since some metals take longer to etch than others. For the success of photochemical etching, careful monitoring and control are crucial.
Stripping the Remaining Resist Film
During stripping, a resist stripper is applied to the pieces to remove any remaining resist film. Once stripping is completed, the finished part is left, as seen in the image below.
Unlike photochemical etching and acid etching, laser etching is a process that places marks, shapes, and images on the surface of parts and products. The process requires a great deal of energy and melts the substrate of the workpiece. Much energy is focused on a small workpiece area where it melts and expands the surface metal.
Laser Etching Metals
The laser beam is pulsed and releases bursts of energy at controlled and monitored intervals. In a second, a 100 W laser releases 100,000 pulses, with each pulse containing one millijoule (mJ) of energy that can reach a peak of 10,000 W.
As the beam strikes the surface of the metal, it absorbs the energy and converts it to heat. The energy absorbed must only be enough to melt the micro surface, about 0.001 in or 0.00251 cm, and cause it to expand. In the laser etching process, very small amounts of the surface are affected, leaving a textured impression.
Types of Laser Etching Machines
The two types of laser etching machines are flatbed or plotters and galvo. The difference between the two methods is how the laser is applied.
Flatbed Laser Etching Machine
— With a flatbed laser, the laser beam is directed by a mirror that is parallel to the X-Y axis of the flatbed to a lens where it is focused. The X and Y move the laser beam and position it correctly. The only limitation of the process is the size of the machine.
Galvo Laser Etching
— The galvo process also uses mirror technology to direct the laser beam. The difference in the processes is how the galvo process directs the laser through high-speed oscillating mirrors that direct the beam in several directions by rotating and adjusting the mirror angles. It is an ideal process for fast-speed marking of fine intricate details. Galvo laser beams can mark any geometrie at speeds of several feet per second.
Laser Etching Materials
Before the development of laser etching, most etching was done by acid etching. Laser etching replaced acid etching because of its cost-effectiveness, the use of only a laser etching machine, and the lack of waste. The list below contains the common metals used for laser etching with their melting points.
Types of Lasers
The difference between lasers is determined by the type of mediums they use to produce the beam. The various mediums have wavelength emissions and absorption bands, with industrial waves continuous or pulsing.
Solid State Lasers
Solid-state lasers use glass or crystal material as their medium.
A gas laser has an electric current discharged by a gas medium.
Liquid lasers use a liquid as the medium, mixed with a dye and solvent.
Semiconductor lasers are known as diode lasers and use electric energy.
Metal Vapor Lasers
A metal vapour laser is an ion laser that vaporizes metals.
An excimer laser is an ultraviolet laser that produces powerful pulses.
Electrochemical Metal Etching
Electrochemical metal etching can etch into any material that conducts electricity. It does not require heat, does not change the microstructure of the metal, and does an extraordinary job of bringing out details in the workpiece. Electrochemical metal etching is an inexpensive and quick etching process.
Creating a CAD or Adobe Illustrator Design
As with photochemical etching, the process of electrochemical etching begins with the creation of a CAD or Adobe Illustrator design. Once the design meets the necessary parameters, it is printed on a transparency, which is used to create the stencil of the image to be etched.
Creating the Stencil
The stencil is made of a photosensitive material where the image from the transparency will be exposed and imprinted. Electrochemical stencils are highly durable and long-lasting materials that can be used for manual operations or electrochemical metal etching production machines. They deliver sharp, clear images repeatedly for hundreds of impressions.
The transparency is exposed to the stencil and imprinted on it. The stencil is washed out with a developing solution to expose the markings that have been imprinted.
The Electrochemical Etching Process
The etching process includes the use of sodium-based solutions that are combined with low-voltage electrical pulses. The current of the electricity dissolves the metal and extracts it into a cloth pad known as the monopod. As the material is removed, an oxide forms in the etched area, which gives the high etching contrast, a sharp image for easy detection, and prevents corrosion.
The shallow etching process of electrochemical metal etching happens quickly, in less than a second. The resulting image is dark. The darkness of the image depends on the type of metal being etched.
Deep etching, using electrochemical metal etching, uses direct current (DC) to remove the metal ions. The deep etching process can create parts and components with etching depths of 0.001 to 0.003 in or 0.00254 cm to 0.00762 cm or deeper. The power for deep etching is pulsating and may need to be repeated to reach the desired depth.
Metal Etching Products
Metal etching shapes and forms products with intricate and complex designs. It is a method several industries use, especially in computer components and electronics. The versatility of metal etching makes it ideal for products for the home and defence, and military weapons.
Metal etching produces a wide assortment of parts without damaging the structure or tolerance of the shaped metals, a shortcoming of other metal-forming methods. Metals retain all their characteristics and properties regardless of the piece being produced.
Metal Covers and Lids.
A necessary property of metal covers and lids is that they lay flat to fit tightly and precisely. Since etching does not stress or deform metals, it is the ideal choice for producing covers and lids made to the required dimensional tolerances.
Electrical connectors are used in various environments and must be made of materials capable of enduring and withstanding the conditions. The etching process produces electrical products that are stress and burr-free using exceptionally high-performance metals that have excellent strength-to-weight ratios. Connectors can be produced with an accuracy of ± 0.025 mm or 0.001.
Metal etching is widely used in the medical field for making a variety of prosthetics for implantation and the production of surgical tools. Extremely tiny metal screens used in sensors, monitoring devices, and surgical needle threaders are made using the process.
The metal etching process is ideal for manufacturing surgical blades that have to be flawless down to the μm. The close dimensional tolerances of the metal etching process create blades that meet the demanding requirements of the medical field.
Unlike old automobiles, modern ones require an assortment of electrical components, clutch springs, encoder disks, fuel cell plates, and nameplates that must be produced with exceptionally accurate tolerances to meet weight and noise requirements. Every aspect of an automobile is precision engineered and designed down to the smallest detail, which is why the industry relies so heavily on metal etching.
The diaphragm of a microphone is the device that changes vocal waves into electronic waves. As microphones have gotten smaller, so have the diaphragm, which has presented a challenge for manufacturers. Metal etching has become the ideal solution to the problem since it can print and etch the smallest types of parts.
Modern technologies are getting smaller and smaller, creating the need for components that meet the decreasing sizes. Since many of the new products are micro-sized, there has been a rising demand for metal etching manufacturers to meet the demand. This has become especially true in the production of micro springs.
Every industry, from manufacturers of medical instruments to producers of firearms, depends on micro springs to supply tension and control. As the products have gotten smaller, so have the wires, which have diameters of 0.002 in or 0.05 mm to meet the specifications of the miniature applications.
Fuel cells are made by stacking bipolar plates with complex channels that enable liquids and gases to flow. The plates can be produced using traditional CNC machining, which introduces stress and burrs. Also, the machining process can be slow, expensive, and inefficient. Metal etching can produce the plates’ intricate components smoothly and efficiently. The process allows designers to adjust and change the size and shape of the plates.
Etching Product Numbers on Products and Parts
A common use of metal etching is placing identifying marks on equipment, parts, machinery, products, and components. Since etching can be used on any form of metal and is performed using a variety of processes, placing numbers and description on parts is a minor function of the process.
Metals commonly used for metal etching of nameplates are copper, aluminium, brass, stainless Steel, and aluminium. Etching is used instead of engraving because it can etch complex and intricate shapes and configurations. Also, metal etching is capable of machining stainless Steel. The commonly used process for etching nameplates is photochemical etching since it includes computer design.
The brief list above is only a small sampling of the thousands of parts, products, components, and items produced using metal etching. Modern manufacturing depends on metal etching to provide intricate and complex parts with the necessary precision and tolerances with on-time delivery.
Metals Used in Metal Etching
There are very few limitations to the types of metals that can be processed by metal etching. It is a metal machining method that can be applied easily and quickly. As with any manufacturing process, some materials are easier to work with than others. This is one of the factors that determine the use of certain materials.
The purpose of the component being produced is a further restriction on the materials used for metal etching. Conditions that place stress and demands on a part will require a different type of material from those needed for less stressful environments.
Titanium has many positive properties, including lightweight, strength, and exceptional fatigue performance. Though these characteristics are ideal for forming parts, they are difficult to machine. The difficulties of working titanium using normal machining processes are overcome with metal etching. The high thermal conductivity, chemical reactivity, and strength of titanium make it an ideal metal for the metal etching process.
Aluminium has many positive properties of titanium, such as a high strength-to-weight ratio and corrosion resistance. It has an excellent fatigue limit, making it good for producing aeronautical parts.
As with many metals, aluminium is suitable for a select number of etching processes. It is an ideal metal for laser etching because its surface has high thermal conductivity, which allows the machine to etch at very high temperatures. The resulting aluminium parts have rough granular surfaces in etching processes involving heat.
Stainless Steel can be etched using any of the various processes. It is an excellent material for laser etching since images placed on it meet photo quality standards.
Regardless of the process, the primary grades of stainless Steel used in metal etching are series 316 and 306.
In photochemical etching, stainless Steel easily accepts the photoresist laminate mask and the CAD or Adobe Illustrator image. Ferric chloride can remove unnecessary metal from components like other metals. Metal etching is widely used in stainless steel parts since burrs are not produced, and the metal is not stressed.
Of the various metals, copper alloys are the easiest to work since they etch quickly and can be etched using any process. Metal etching is preferred for copper alloys because other metal working methods distort the metal and damage its properties. Copper alloys are conductive, durable, ductile, and malleable, which makes them suitable for two-dimensional and three-dimensional electronics.
Nickel alloys have resistance to heat and corrosion. As with copper alloys, nickel alloys are easy to etch and are widely used for electrical applications. They are versatile and can maintain their properties at temperatures up to 500 ° C or 932 ° F. A popular use of nickel alloys is a shielding material for electrical components since they are resistant to electricity.
In metal etching, nickel can be etched into various designs, shapes, and configurations. Etching is chosen for working nickel alloys because the process does not produce burrs or thermal stress on the metal.
Inconel is a nickel-based alloy with superior heat, corrosion, pressure, and oxidation resistance. Though these admirable properties make it difficult to etch and machine Inconel. Special metal etching processing has been developed such that inconel can be used to produce bipolar fuel plates.
There are a wide variety of uses for Inconel, including extreme conditions with tremendous pressure and heat. Its thick layer of oxide offers protection against the elements. The type of Inconel used the most in the etching process is series 625.
Benefits and Advantages of Metal Etching
Modern manufacturing and production demand immediate access to parts and components. Since mechanical metal forming takes time and preparation, more is needed to meet the needs of complex and involved production methods. For these reasons, metal etching has rapidly become the go-to manufacturing method.
As product and part designs become more precise, planned, and computerized, production methods are continually being adapted and adjusted to meet the new technical requirements. Although metal etching has a long history, it is constantly being improved and modified to meet today’s manufacturing needs.
Since much of the metal etching process is digital, it can be quickly generated. The precision of digital tooling ensures that every component created by the process will meet the design’s dimensional requirements.
Of the many aspects of modern production, the cost is a major factor when choosing a manufacturing process. The efficiency of metal etching makes it possible to have an accurate product run without errors or the need for finishing. The digital process allows for the adjustment of design errors before placing a product in production.
Other machining methods stress metals with heat, force, and mechanical manipulation that change the properties and characteristics of the metals. The metal etching does not stress metals such that they retain their properties and perform according to their characteristics. The metal etching process does not make contact with the metal surface, which allows the metal to be reshaped but has unchanged properties.
An absolute necessity for producing and manufacturing any metal component or part is that every piece that comes off the assembly process has the same dimensional tolerances. This is an essential part of production repeatability. With metal etching, the digital diagrams and renderings remain unchanged from production run to production run, guaranteeing that every workpiece will be the same from the first to the last.
Mechanical metal fabricating processes produce workpieces that have irregularities such as burrs, rough edges, and deformities that are removed during finishing. None of these factors are present in metal etching. Since any form of equipment does not touch workpieces, they come off the assembly process clean and ready for shipment.
Speed is the keyword for every form of the manufacturing process in the modern lexicon. Customers place their orders and expect completed parts immediately. Though metal etching makes that type of service impossible, the process has significantly rapid turnaround times. Since there isn’t any need for finishing, products are processed, produced, and shipped with little delay.
The digital process of metal etching provides the ability to create a prototype of the component for examination before it goes into production. Customers can sit down with a designer or engineer and give them the parameters of the part, which can be fed immediately into a computer for assessment and evaluation. Once agreement is reached on the dimensions, the rendering is transmitted from the computer to production without errors or any need for reprocessing.
Branding has become a central focus in marketing strategies and product development. Metal etching assists in the process by being able to place product identification easily on the items that are produced. This avoids the need for purchasing labels. During the planning process, it is possible to determine where to place any branding symbols or stamps, as well as part numbers and contact information.
- Metal etching is a metal removal process that uses various methods to configure complex, intricate, and highly accurate components and shapes.
- The process of metal etching is the removal of excess material from a workpiece using a chemical reaction.
- Metal etching shapes and forms products with intricate and complex designs.
- Etching is used to produce parts without damaging the structure or tolerance of the metals being shaped, which is a shortcoming of other metal-forming methods.
- There are very few limitations to the types of metals that can be processed by metal etching.