MICRO MACHINING | ARTICLE Photochemical Etching – Te Basics
Despite the fact that photochemical etching has been a machining technology for over 50 years, it is still a relatively low profile process, and its practical use in a variety of manufacturing scenarios with an ever broadening number of materials is one of industry’s best kept secrets. To remain competitive and to stimulate innovation in the production of micro metal parts, it is vital that design engineers are made aware of the nature of this versatile technology, and the opportunities that it presents when compared with beter-known and more traditional metal-working technologies.
Commonly misrepresented as merely prototyping technology, photochemical etching is in fact a versatile and increasingly sophisticated metal machining technology, with an ability to mass manufacture complex and feature-rich metal parts and components. Using photo-resist and etchants to chemically machine selected areas accurately, the process is characterised by retention of material properties, burr free and stress free parts with clean profiles and no heat-affected zones.
Coupled with the fact that photochemical etching uses easily re- iterated and low-cost digital tooling, it provides a cost-effective, highly accurate, and speedy manufacturing alternative to traditional machining technologies such as metal stamping, pressing, CNC punching, and laser and waterjet cuting.
Traditional machining technologies can produce less than perfect effects in metal at the cut line, oſten deforming the material being worked and leaving burrs, heat-affected zones and recast layers. In addition, they struggle to meet the detail resolution required in the ever smaller, more complex and more precise metal parts that many industry sectors require. Tere are instances — typically when an application requires multiple millions of parts and absolute precision is not a priority — when these traditional processes may be the most cost-effective. However, if manufacturers require runs up to a few million, and precision is key, then photochemical etching with its lower tooling costs is oſten by far the most economic and accurate process available.
Another factor to consider in process selection is the thickness of the material to be worked. Traditional processes tend to struggle when applied to the working of thin metals, stamping and punching being inappropriate in many instances, and laser and water cuting causing disproportionate and unacceptable degrees of heat distortion and material shreddin, respectively. While photochemical etching can be used on a variety of metal thicknesses, one key atribute is that it can also work on ultra-thin sheet metal, even as low as 10 micron foil.
It is in the manufacture of intensely complex and feature-rich precision parts that photochemical etching really finds its perfect application, as it is agnostic when it comes to shapes and unusual features in products to be manufactured. Te nature of the process means that feature complexity is not an issue, and in many instances, photochemical etching is the only manufacturing process that can accommodate certain part geometries.
Active in the field for many decades, Precision Micro is constantly pushing the boundaries of what is possible in the process, making advances in etchant chemistry and developing the process to embrace more and more metals and enhance accuracy for its customers. It is this pre-eminence that led to world-renowned
electronic systems company Tales to partner with Precision Micro in the manufacture of flexures required for use in cryogenic coolers for long life cooler applications, including space applications.
Flexures for a Cryogenic Cooler
Tales Cryogenics BV was founded as a separate company in 2000, and is able to trace its roots back to the late-1940s when it was a department within the high-tech equipment supplier Signaal USFA.
Today, Tales Cryogenics is a leading developer and manufacturer of specialised cryogenic equipment, with offices and manufacturing facilities located in Eindhoven, the Netherlands. Its expertise lies in offering — from design to manufacture — the most comprehensive range of cryogenic products for military, civil or space applications. Te company’s particular strengths include the translation of new concepts and techniques into custom-built working hardware, with special emphasis on prototype-building, series production, pre-production engineering and the development of special- purpose tooling and test equipment.
For a leader in the field with a world-class reputation to maintain, Tales Cryogenics chooses its partner suppliers extremely carefully, and when looking for a reliable and cost-effective manufacturer for a particularly critical flexure component for a satellite cryogenic cooler, it selected Precision Micro, established as the leading photochemical etching supplier in Europe.
Te critical nature of this component was key in choosing Precision Micro and the photochemical etching process as the preferred manufacturing method. Tere is no more extreme environment than space, which demands that parts and components not only work as intended, but do so over prolonged periods of time.
>> Continued on page 14 12 | commercial micro manufacturing international Vol 7 No.6
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