Understanding the chemical etchings and RF shielding

Oct 29, 2012 by richiemoranx

Today’s society becomes more and more interested in ecology and power saving technologies. What this article is about to present may not be directly connected to ecology or power saving, but it surely improves the overall techniques used in the industry as well as achieve less manufacturing costs and better production through quality and time efficiency.

Chemical etching is very similar to a printing process, where the part designs can be highly intricate without having a major impact on the tooling or production process. Very thin metal can be processed without distortion, dimensional accuracy will increase as the thickness of the metal decreases.

The actual process of etching occurs when PEI places the metal sheets on the conveyor system, and then sprays both sides of the metal with etchant (etching chemistry is determined by the type of metal that’s being processed). The unprotected metal surfaces on these sheets will dissolve into solution, leaving an exact metal replica of the customer’s specifications.

After etching and rinsing, the remaining photo-resist is stripped-off the newly formed metal parts on the sheets, which are now ready for shipment or any further operations like plating, forming, soldering, silk screening, heat treating, welding and assembly.

For many etch steps, a part of the wafer is protected from the etchant using a “masking” material which can resist etching. Sometimes, the masking material is a photo-resist which has been designed through photo-lithography. Some situations, require a more sturdy mask, perhaps a silicon nitride one. The etch will make a cavity in a material, and that cavity depth can be controlled using exposure time or etching time (also known as etch rate). Chemical etching can produce very complex pieces that would be either impossible or impractical to produce using traditional stamping or laser cutting.

RF shielding is a modern practice used to reduce the electromagnetic field in a limited area, by introducing barriers within the field that are made of conductive and/or magnetic materials. Commonly, shielding is applied to enclosures with the sole purpose of isolating electrical devices form harmful interference form the “outside world”, or it can be applied to cables, protecting the signal traveling through cable wires from any distortions that could appear throughout the length of the cable.

Such enclosures are usually designed and used to filter a range of frequencies, under exact specified conditions. Another RF shielding method frequently used, usually in the case of electronic systems contained by plastic enclosures, is coating the inside of the enclosure with a metallic ink or similar material. The ink contains a carrier material loaded with a particular type of metal (copper or nickel), in form of very small particles. This ink is pulverized on the enclosure surface, and once dry, it resembles a continuous conductive layer of metal, which can be connected through an electrical contact to the chassis ground of the equipment, providing thus effective shielding.

As it can be seen throughout this article, such evolved techniques are being used in the industry’s countless applications and domains. And, they are still evolving, refining the process and lowering the costs.

For more information on Chemical Etching, you can visit here