LASER ETCHING COPPER

Copper is one of the few metals that is directly usable in its natural form, or without being combined into alloys. It is characterised by having a very high thermal and electrical conductivity, making it a valuable material in electrical wiring, printed circuit boards, thermocouples, heat exchangers, electromagnets, and electric motors. Copper is a naturally soft and malleable metal which can be fashioned into pipes and pipe fittings, or as architectural elements. The green patina that the metal develops after a long period of atmospheric exposure is a particularly coveted finish by architects and designers due to its visual appeal.

Moreover, the metal has excellent workability and lends itself well to processes such as brazing, welding, and soldering. Where increased hardness is desired, copper has been blended with other metals to form alloys such as brass, bronze, and sterling silver, all of which are commonly used to create jewelry.

Copper’s antimicrobial property

A particularly useful characteristic of copper is its antimicrobial property. Copper and copper-alloy surfaces have the natural property of destroying microorganisms, making copper an excellent material for doorknobs, handrails, computer keyboards, shopping card handles, faucets, and health club equipment. Being a biostatic material, many other forms of life cannot grow on a copper surface. This has made copper a standard material to line ship hulls to protect against the growth of barnacles and mussels. The corrosion resistance of copper also makes it especially appropriate for long-term use in marine environments.

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The challenge of a reflective surface

Laser etching copper is particularly challenging because of the high reflectivity of the material. In fact, a solid surface made of pure copper will reflect more than 95% of incident near-IR radiation. As with stainless steel, a fiber laser is generally preferred over a CO2 laser when laser engraving copper or to produce laser cut copper. A fiber laser has a wavelength of around 1.07 µm, around 10x smaller than the wavelength of a CO2 laser. Not only will a fiber laser be reflected less than a CO2 laser, but the smaller wavelength allows for a greater power density which makes it easier to penetrate the copper surface.

The key in laser etched and cut copper is to keep in mind that the reflectivity of the metal steadily decreases as it gets melted, and dramatically drops at melting. Thus, an optimal laser cutting process for this material focuses on high-powered laser in short pulses on the unheated solid surface to minimise the amount of back-reflected light. A high-powered laser, at least 1000W, is needed to establish a heated or melted portion of the copper surface. After the initial step, the laser mostly interacts with the copper in its melted form, accelerating the laser etching or laser cutting process.

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