Basic principle of laser etching process

The laser etching process is similar to the manufacture of printed circuit boards, where exposure to UV light transfers an image of a component onto a photoresist-coated metal. The unexposed photoresist is then washed away, leaving the bare metal etched. In tank etching, the prepared board is dipped in the etchant. Conveyor belt etching sprays high pressure etchants on the top and bottom of the board. The exposure length of the etchant is determined by the thickness of the alloy and metal. Of the many etchants used, the most common is ferric chloride. It is suitable for a variety of non-iron and iron metals, is relatively easy to use and easy to neutralize. Certain precious metals and many high performance alloys require the use of highly corrosive etchants such as hydrofluoric acid and require special attention.

Commercially available etching equipment requires strict compliance with environmental regulations and strict monitoring. Most of these facilities have a waste treatment function that removes molten metal from the etchant, neutralizes all chemicals and returns the process water to a technically drinkable state before discharge.

When you start the photolithography process, you need to create an image tool. Customer files (usually in 2D CAD formats such as DXF and DWG) correct the thickness of the material to be etched and step through and repeat in software to maximize the use of a particular sheet size. You can partially overlap or "nest" certain parts to improve material utilization. The composite file is sent to a very high resolution digital imaging device (usually a laser plotter) and imaged on two optically transparent Mylars. The top and bottom of this image tool are optically and mechanically aligned and punched. Image tools are cheap, usually less than $ 300, and can be created in 24-48 hours.

Cleanliness is important for successful photolithography, and the materials used must also be thoroughly cleaned. A variety of cleaning processes are available, including weak acid cleaning, abrasive sanding, alcohol wiping, and then a final rinse with deionized water.

The washed sheets are stacked and coated on both sides with a thin layer of UV-activated polymer called a dry film photoresist. Photoresists are particularly sensitive to light in the UV spectrum, so lamination, imaging, and development are all done in safe light with a yellow hue.

The photoresist-coated metal sheet is placed between the top and bottom of the picture finisher aligned with the printer pins. The air is then expelled from the squeegee and evacuated to ensure a firm contact between the emulsion and the photoresist. The plate is exposed to high intensity UV light and the photoresist in the exposed area of the image begins to cure.

The imaged board is placed in a developer, which rinses the unexposed photoresist and leaves bare metal in the shape of the part. The metal machined into the part is protected by the developed photoresist.

The Etcher is about 40 feet long and can handle a seat width of about 29 inches. A series of vibrating nozzles are located at the top and bottom of the driven roller conveyor, which runs along the length of the Etcher. In the first two chambers of the Etcher, the nozzle distributes the heated and pressurized Etchant. In the last two chambers, the etchant is neutralized by a series of consecutive rinses of cleaning solution.