by Marjorie Steele, Editor at IQS

To be sure, the manufacturing community has come a long way in terms of microtechnology. Not only have acid etching and photochemical etching helped manufacturers hurdle significant cost and time barriers, but it has dramatically increased our capacity for fabricating the precision micro-etched parts which are essential to manufacturing precision electronics and communications equipment. No longer are our precision parts manufacturers limited to what metal engravers can etch by hand scratch by agonizing scratch; with chemical and photochemical metal etching, the possibilities are virtually limitless.

Chemical etching has dramatically decreased the time required for the etching process, as opposed to individual machining or engraving. Once a surface pattern is applied, metal parts are submerged or coated with an etching chemical, commonly ferric chloride or cupric chloride, the chemical eats away at the exposed metal. This process generally creates a clean, controllable etch which requires little secondary processing.

Photochemical etching in particular has become an industry standard for cutting-edge microtechnology manufacturers. Photo etching compares to other processes – even standard chemical etching processes – in the same way that painting with die-cut stencils compares to hand painting. Even in chemical milling – still a far cry from hand engraving – “stencils” must be individually etched or cut, whereas the photochemical process, once design is completed, creates patterns almost instantaneously. Instead of etching patterns for wet chemical immersion being applied individually, pre-treated metals are fitted with a UV blocking patterned overlay which is then exposed to UV light. The photoresist not covered by the printed overlay develops, exposing targeted areas to the chemical etching the metal will undergo next. The entire patterning processes, previously the most costly and time-consuming step, takes minutes versus hours.

For all of the benefits of the chemical and photochemical etching, the process has its drawbacks. As with plastic, a seemingly time, cost and fuel efficient alternative to non-disposable packaging, photochemical etching produces considerable quantities of hazardous waste which are difficult to recycle and dangerous to dispose of. Large quantities of specialty and hazardous chemicals and gases, particularly chloride, must be manufactured and either recycled, a costly process, or disposed of at the hazard of the environment. Yet chemical etching has been integrated into the global manufacturing processes of so many mobile phones, automotive parts, computer chips and other communication and electronics devices that these concerns remain largely overlooked.

As the nanotechnology industry evolves, however, new developments are constantly being made to improve manufacturing processes. Recent concerns over global warming and ecosystem destruction have heightened all manufacturing communities’ interest in environmental concerns, and several solutions to chemical etching’s hazardous bi-products are being developed.

Among these developing solutions is electrolytic metal etching, also known as electro-chemical etching (ECE). Electrolytic etching works similarly to chemical and photochemical etching, except that the etch is achieved by passing a low voltage current to the metal through a stencil, with an electrolyte soaked pad acting as the current conductor. ECE is an effective marking process for round surfaces and fragile parts, and is already used in marking aerospace, auto and medical components. Harsh chemicals such as chloride or nitric acid are not required for this process; only electrolyte-infused water and a low electrical current are necessary. Whether or not ECE is capable of achieving etchings as dynamic as photochemical etching is a concern among the microetching community, however.

Plasma etching is another possible alternative to wet chemical etching. A “dry” process which uses gaseous plasma within a vacuum to etch metal surfaces. Capable of extreme micro precision, plasma etching is also capable of achieving vertical trenches – a result difficult to achieve from even the most precise photochemical etching. Costs for this process are high, however, since the equipment required for plasma etching is both complex and made from costly materials.

Despite these apparent hurdles, many industries are already beginning to make use of electrolytic etching and plasma etching in the microetching industries, and standards for hazardous photochemical waste disposal are continually being raised. Legislature influences the chemical etching process to some degree, but as the industry trends towards environmentally sustainable innovation, more and more metal engravers and metal etch service providers are pursuing green metal etching solutions.