More about Metal Etching

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Metal etching is generally performed by a chemical process in which lines are incised on the metal with an acid. In a basic metal etching operation, the surface to be etched is covered with a specialized acid-resistant coating, select parts of the coating are scratched away by hand or mechanical means, and then the material is placed in an acid bath. The acid erodes the exposed sections of metal, leaving a pattern identical to that scratched into the coating, and then the work piece is removed and cleaned. The solutions used to perform the chemical etching are called reagents.

In the case of photoetching, which is a specialized form of metal etching, an acid-resistant pattern is photo-mechanically applied to the work piece. This surface is then exposed to etching chemicals, which erode the exposed sections, and then the photo-mask is removed. The major difference between the photoetching process and traditional chemical etching is the application of the photoresist, which is a solution that hardens when exposed to certain types of radiation, such as x-rays or ultraviolet light. The photoresist material allows manufacturers to use photo negatives and positives to produce the pattern to be etched, which drastically simplifies the machining process. It also eliminates any possible errors that may result from scribed maskants.

Photoetching is regularly used in the production of electronic circuit boards, semiconductors and other parts involving complicated patterns. The process is also used in the majority of chemical etchings, as it is far more accurate and easily performed than mechanical or manual scribing. Scribing, however, is used in certain situations, such as on extremely large parts and when simple patterns and short production runs do not warrant the use of photoetching.

When etching metal with the photoetching process, manufacturers often use mercury vapor lamps to harden the photoresist. A variety of processes should be performed before any etching operation, as parts need to be completely clean, degreased and uniform before being masked. Finishing treatments, such as plating, are also performed after the etching process is complete.