Bo Christensen, sales and marketing, Mekoprint
As the demand for more compact, lightweight and complex electronic components and systems increases, so does the demand for more capable and efficient metal fabrication processes. Photochemical machining (also known as chemical milling or chemical etching) is one such process.
Photochemically etched electronic components.
Photochemical machining is a subtractive fabrication process that involves applying temperature-regulated corrosive chemicals to sheet metal to produce complex shapes and patterns.
Manufacturers often choose photochemical machining for several reasons, namely:
- it can be used on nearly all metals;
- it can be used for quick and easy prototyping, modification and revision processes;
- it reduces thermal stress-related problems during fabrication;
- it reduces the occurrence of burrs (no burrs on the parts)
- it is highly precise and can be used to create complex geometric patterns on thin, lightweight metal sheets; and
- it is cost- and time-effective.
Photochemical machining processes match the increased demand for smaller, more lightweight electronic components and systems across a number of industries such as aerospace, automotive, electronic, medical and healthcare, and military.
Unlike more traditional metal machining processes (such as waterjet cutting, wire electrical discharge machining (EDM), stamping, etc.), photochemical machining can be used to produce a wide range of highly precise prototypes and finished components quickly and efficiently for all of the aforementioned industries and more.
Let us look at the five main reasons why manufacturers should consider photochemical machining for metal fabrication in more detail.
1. Exceptional versatility (works with almost any metal)
Photochemical machining is extremely versatile, meaning it is able to effectively and efficiently etch almost all metals with relative ease. This versatility is a godsend for manufacturers. The metal’s hardness, softness, fragility, thickness and toughness are largely irrelevant, which is a convenience not found when utilising more conventional metal machining practices.
Waterjet cutting and wire EDM, for example, are less versatile. Waterjet cutting is not suited to tougher and thicker metals, whilst wire EDM only works on metals with electrical conductivity, sometimes requiring a conductive layer (assisting electrode) on the workpiece surface.
2. Swift and cost-effective prototyping and modification processes
Arguably the biggest advantage of photochemical machining is the quick and easy creation of prototypes. It is a vital part of the entire manufacturing journey, especially when manufacturers need to make a component or system quickly, or if adjustments, modifications and revisions are required. Prototypes can be delivered within a matter of days (project size dependent).
Low-cost computer-aided design (CAD) software is used by engineers to digitally create stencil designs known as photo-tools. These photo-tools are hardened onto photoresist-coated sheet metals ready to be photochemically etched. They are incredibly cost-effective and allow customers to make changes without needless budget-stretching. Conventional tooling, on the other hand, is far more expensive, costing significantly more for simple changes.
Furthermore, if the customer requires multiple designs and components, the photochemical machining process allows manufacturers to create more than one electronic component at the same time, provided each one requires the same metal material and thickness. This is known as compound tooling.
3. No unnecessary thermal stress
By definition, thermal stress is the result of temperature changes in any given material, often causing unwanted and problematic expansion (when heated) and contraction (when cooled). High temperatures are often utilised in metal fabrication processes, usually in laser cutting or wire EDM, resulting in an increased risk of thermal stress-related issues.
Although the thermal stress affects the metal at a micro level, these issues themselves can cause a number of different problems, especially along the edges where etching takes place. Micro-level distortions, deformities and imperfections can affect electrical components and systems in ways not conducive to optimal performance and quality.
Fortunately, the photochemical machining process counteracts thermal stress-related concerns. As opposed to laser cutting, which transfers very high levels of heat onto the workpiece, photochemical machining essentially dissolves the unwanted metal from the workpiece. Whilst heat does occur and the metal will experience a rise in temperature, it will not be subjected to unnecessary thermal stress, weakening, fracturing or deformation. In fact, the metal will remain largely unaffected, causing fewer headaches for manufacturers.
4. Prevention of unwanted burrs
Burring is still one of the biggest problems faced in metal fabrication, especially if using laser cutting or wire EDM due to their infamous imprecision. Metal stamping can also lead to burring, simply because of the heavy-duty processes involved.
In terms of metal fabrication, burrs are considered annoying and counterproductive imperfections. They usually look like rough edges, ridges or small but solid, bubble-like shapes along the edges of metal. Sheet metal is the most commonly affected metal.
Aside from being an eyesore to look at, burrs can be unsafe to handle as well as cause corrosion, electrical short-circuiting, reduced formability and dimensional tolerance issues. If burrs occur, manufacturers are forced to eliminate them via a deburring process. Grinding, sanding, media blasting and electrochemical machining (ECM) are the most common deburring methods. Unfortunately, these methods are costly and take a lot of valuable time and effort.
To prevent burring and burring-related issues, manufacturers should be conscious of the etching methods they use. As mentioned, wire EDM, laser cutting and stamping all produce varying levels of burring but photochemical machining does not. The reason for this is that the chemical etchant completely dissolves all the unwanted burrs as the etching takes place, resulting in a clean, smooth surface.
5. Complex design capabilities (perfect for compact electronic devices and systems)
The demand for more compact and lightweight electronic devices and systems has risen significantly over the past ten or so years and continues to increase at a rapid pace. These devices and systems, in turn, require more compact and lightweight components that have increasingly elaborate geometric designs. Manufacturers must consider how best to create these designs in the thin metals required at the same time as improving overall performance and quality.
One of the primary benefits of using photochemical machining is that it is almost like 3D printing, in that it can be used to create very complex designs in a variety of metals to suit the intended purpose. It can be used on very thin and lightweight sheets of brass, copper, nickel and austenitic stainless steel. Photochemical machining is especially suitable for electromagnetic interference (EMI) shielding, filters and other electronic components that have complex designs because all component features (holes, angles, etc.) can be created at the same time, saving manufacturers time and money.
Photochemical machining can also be used to perform half-etching, a process that involves partially scoring lines to allow manual forming of the metal material. This is good for creating 3D shapes, as well as names, numbers and logos. Also, there is no extra cost to the manufacturer or customer.
To conclude, not all metal machining methods are suitable for creating today’s more compact and lightweight electronic components, often falling short of complexity, precision, performance and quality requirements. As has been highlighted, photochemical machining affords many more advantages than the quick and easy creation of prototypes, therefore it should be considered a main contender by manufacturers.
Photochemical etching at Mekoprint Chemigraphics.
Mekoprint