What is laser etching?

Laser etching is a broad term encompassing various marking and shallow engraving processes. In general, laser etching differs only minimally from laser marking; etching involves changing the surface profile of a part rather than simply changing the colour or texture of the surface. However, this profile change, which can be either raised or sunken, is generally much shallower than the changes associated with laser engraving.

Laser etching is a method for creating visible marks or patterns on a variety of materials. In fact, the exact definition of what constitutes "etching" (as opposed to marking or engraving) varies by material and application. Laser etching is used on a wide variety of products such as automotive parts, medical devices, wine barrels, microelectronic components and tombstones. Laser etching is performed in the same way as many other marking, engraving and cutting processes. In fact, it is not at all unusual for a single laser tool to perform all of these functions, depending on the power setting and speed of the job.

To create the desired pattern, the laser beam scans across the surface of the part while being modulated (its power is varied). One way to create this movement is with a galvanometric scanning system. In this case, the movement of the beam is accomplished by moving mirrors. This method is often used for small parts because of the high speed. This technique is also suitable for etching curved parts (often in combination with rotary movement of the part).

Alternatively, the beam transfer optics (or even the part itself) can be moved using linear or stepper motors to make the desired marks. Larger or heavier parts such as signs and monuments are almost always etched in this way.

Laser etching of various materials

Almost any type of material can be laser etched. This includes metals, plastics, glass and ceramics, natural stone and semiconductors.

Laser etching of metal parts is performed in many industries, including automotive, aerospace, medical products, oil and gas, and more. It can be applied to almost all metals, including aluminum, steel, brass, copper and titanium. Laser etching of metals typically involves heating the material until it melts and stretches slightly. After this short laser heating cycle, the material cools almost immediately and hardens into a raised surface that has a rougher texture than before.

For metals, laser etching typically changes the surface height by less than approximately 25 µm. In contrast, laser engraving is often ten times deeper. Because engraving deeper marks requires the removal of much more material, laser etching can usually be done much faster.

Another advantage of laser etching is that the marks it produces can be dark, light or even a shade of grey. Laser engraving usually only produces dark marks. However, shallower etched marks are not as durable and abrasion resistant as engraved marks.

Glass is laser etched for decorative and commercial purposes. Text, patterns and other intricate designs, even including images, can be etched onto drinking glasses, mugs, bottles, award plaques, mirrors and other items. In the industry, many products supplied in glass containers, such as beverages or pharmaceuticals, are etched with information such as batch numbers and expiration dates. Similarly, serial numbers and tracking codes can be etched onto glass substrates used in the manufacture of microelectronics and displays.

A laser-etched surface on glass appears "frosted" - that is, translucent but not transparent. This is achieved by removing a very small amount of material, usually less than 25 µm. Importantly, the etching process produces a much rougher surface texture.

Laser etching is preferable to other mechanical and chemical methods because it is fast, clean and easily adapted for use on curved surfaces (which are common on wine glasses, bottles, etc.).

Laser etching of natural stone - such as granite or marble - is widely used for tombstones, memorial plaques and architectural purposes. Like glass etching, it involves removing a very small layer of material and changing the surface texture.

Laser etching is almost always used to create a light mark on a dark stone surface. The laser-etched pattern consists of many small dots placed close together, much like how photographs are reproduced in a newspaper. As a result, virtually any pattern can be etched, and even grayscale markings can be engraved. In addition to text, photographs, drawings and other patterns can be easily etched.

Laser etching on stone usually provides better mark visibility than sandblasting or mechanical engraving. It is also much faster than these other methods.

An extremely wide range of commercial, medical and consumer products, as well as signage and novelties, are laser markedon polymers . Because of the huge variety of materials and processes, it is more difficult to define exactly what constitutes laser etching of polymers and how this process differs from marking or engraving. The commonly used technique of 'foaming' - which delivers a light-coloured mark on a dark plastic - could rightly be considered a form of etching, as it only produces a small amount of surface relief (less than 50 µm).

Because laser etching allows high-contrast marks to be made in polymers without introducing significant amounts of heat into the part, it is also very popular in semiconductor and microelectronics manufacturing. For example, it can be used to mark flip-chips and other types of semiconductor packaging without damaging the circuitry they contain.

Laser etching of semiconductors is used throughout microelectronics manufacturing. This is because the small depth of the mark - often 10 µm or less - produces a high-contrast mark that does not damage surrounding or underlying circuitry. Laser etching is particularly useful for marking serial numbers and other identifiers on the back of wafers. It is also used on the thin lids of molds of packaged devices.

Lasers for etching

Due to the wide variety of materials and requirements, many different types of lasers are used for etching. Typical examples include:

Fiber lasers

CO2 lasers

DPSS lasers

Diode lasers

Coherent laser etching products

Coherent offers three types of laser etching products. The first is laser sources, including fiber lasers, CO2 lasers, DPSS lasers and diode lasers. These are useful for those creating their own etching systems.

We also offer etching subsystems. In particular, our PowerLine series combines various types of lasers with powerful scanning and beam transmission optics, drive electronics and powerful control software. This creates a fast, flexible and precise platform for etching, marking and engraving. PowerLine products can be supplied with almost any type of laser source, making them ideal for system designers and integration into production lines in a wide range of applications.

Source: Coherent.com