Chemical Etching Terminology

Etching Materials

Tecomet Etch has expertise in etching nitinol, titanium, molybdenum, Co-Cr alloys, Kovar, Stainless Steel, Copper, Brass, Beryllium-Copper, and Bronze etc. The products reach a broad range of applications including medical, electronic, and industrial use. Photo chemical machining (etching) is a low-temp, precise, flexible and economic process. for prototype or high volume production it cuts metal clean, burr-free without heat-affected zones. The thickness range is from 0.0001” up to 0.060” with excellent tolerances. Understanding chemical etching terminology through the photochemical machining glossary can be important when exploring the full range of this process’s capabilities.

Etching Process/Photochemical Machining

Thin metal sheets are first cleaned in chemical solutions and laminated with a very thin layer of photo-resist film. This film is photo sensitive and it can receive fine images within a part. Using a photo-tool, images are printed on both sides of the sheet with calibrated ultra violet lights. Printed sheets are developed in chemical solutions such that the desired surfaces are ready for etching. The sheets are then etched in acidic chemicals and the residual photo-resist film is stripped in alkaline solutions. Process parameters at each stage are controlled to obtain desired dimensions and finish. At this point the etched components are ready for necessary secondary operations such as forming, plating, heat-set, passivation, anodizing, etc.

Definitions & Dimensional Accuracy

Dimensional accuracy is a function of metal thickness, i.e., better accuracies are obtained on thinner metals. It also helps to achieve tighter tolerances. Another significant factor is the type of metal. For example, aluminum etches at a significantly faster rate than stainless steel. Titanium would require different etching chemistry than stainless steel or copper. Ultra-thin metal substrates require enhanced techniques. Our engineers will guide you to optimize your design.

Photo-Tool & Etch Allowance

A CAD drawing of the component is used to design a photo-tool. Adjustments are made to the external and internal dimensions by adding material based on type & thickness of metal to be etched. A layout of the photo-tool is prepared incorporating the proper etch allowance. The layout is comprised of several components on a sheet. using an extremely high resolution laser printer the layout is printed on transparent mylar sheets. The photo-tool is ready for use when the top and bottom mylar sheets are aligned and registered. In cases where ultra high resolution is needed a glass tool is used in place of a mylar tool.

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