MICRO MACHINING | ARTICLE
Working with Aluminium So it is its exothermic nature that introduces hurdles for the efficient application of photochemical etching processes to aluminium, as well as the fact that aluminium is a corrosive resistant metal, and photochemical etching is a machining process based around selective corrosion.
Aluminium is amphoteric in nature meaning that it will react with acids or alkalines. As such it can be photochemically machined using either acidic or alkaline etchants, but use of either presents challenges.
The key to successful photochemical etching is strict process controls. Due to the amount of research and experience in this field, Precision Micro is today perhaps the most adept company in Europe at the application or the photochemical etching process to aluminium.
Aluminium is amphoteric in nature meaning that it will react with acids or alkalines. As such it can be
The highly exothermic reaction of aluminium to the etching process can in some instances destroy the photo-tool, and creates a rough etch. Effectively, the exothermic reaction causes the resist to pull away from the aluminium sheet, allowing the etchant to seep under the resist and compromising the etch. This leads to a rough, jagged, granular edge, a long way away from the smooth and straight etched profiles typical of the photochemical etching process.
photochemically machined using either acidic or alkaline etchants, but use of either presents challenges.
Some research into the efficient etching of aluminium has focused on the etchants used, some on temperature control, and still more on the cleaning and preparation of the metal.
Due to the exceptional demand for aluminium in a variety of industrial applications, and the requirement for a machining process that is both repeatable, consistent and overcomes such issues as already highlighted with laser cutting and punching, Precision Micro has invested considerable resource (some £500,000) in lamination equipment to improve the adhesion of the resist to the aluminium.
In addition, the company has utilised its five-decade long experience of photochemical etching to refine and adjust the concentrations of the corrosive chemistry used on aluminium to overcome some of the inherent issues involved with etching an amphoteric material.
Such adaptations of chemistry have proved
satisfactory for Precision Micro’s numerous client projects with additional emphasis on a range of other factors including process speed adjustment and temperature control. All these factors are inter-related, and one can have a negative impact upon the other. For example, adjusting speed of etching can lead to resist lift, so the optimisation of the process is a balancing act, success based on considerable expertise honed over many years and numerous projects.
18 | commercial micro manufacturing international Vol 7 No.4
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