Laser Materials Processing

Laser Technology Solutions for Precision Machining of Challenging Materials

Laser materials processing is of great interest for industrial applications as well as for scientific investigations. Main advantages of the laser as a manufacturing tool are the high speed at which a laser beam can be moved and, contrary to mechanical tools, laser light is not subject to wear and tear. Besides the wavelength, the pulse duration of the laser source is the main parameter influencing the nature of the lasermaterial coupling. Pulse durations of down to a few femtoseconds are available from state of the art laser systems. The high peak intensities. provided by ultrashort pulses initiate multiphoton absorption mechanisms, bridging a band gap much larger than the photon energy. Thus, by applying ultrashort pulses the ablation of nearly any material is possible by multiphoton absorption.

The non-thermal nature of ultrashort pulsed ablation together with the ultrafast mechanism offers well-defined ablation threshold fluences and enables laser structuring with high precision.

Brittle Materials

Transparent and/or brittle materials such as glass, ceramics, and crystals are historically difficult to machine with good quality and high throughput. Traditional mechanical processes are often too harsh and, especially for thinner materials, must be slowed down to prevent severe cracking and chipping of the material. In addition, tool wear is problematic because the cutting edges are continually degrading throughout its lifecycle and the quality, yield, etc. of the processed parts are likely to also degrade—this on top of the consumable replacement cost that can be quite high over time. Furthermore, hard brittle materials result in high rates of tool wear and the consumable cost over time can become excessive. Hence, manufacturers have increasingly looked towards laser technology as a solution.

In many cases, nanosecond pulsed lasers offer good cost and performance for machining these materials. For alumina (Al2O3) ceramics, deep scribing with high speeds can be achieved even with IR (1064 nm) wavelengths, though improved quality and reduced feature sizes may be realized with shorter wavelengths. Glass cutting and drilling is increasingly common in a variety of industries, and green and UV wavelengths are commonly used with good success. As manufacturers pursue increasingly higher quality and machining of finer features, however, the laser industry must provide increasingly better tools.

Process Solutions for Brittle Materials

Picosecond laser technology is increasingly being adopted for machining these challenging materials with both good quality and high throughput. However, current picosecond lasers suffer from a number of major shortcomings – they tend to be expensive, large, inflexible and not necessarily reliable. Spectra-Physics’ IceFyre laser redefines the market for picosecond micromachining lasers. IceFyre is a new industrial picosecond laser that delivers exceptional performance, unprecedented versatility, smallest footprint and industrial reliability – all with industry-leading cost-performance.

The IceFyre laser offers >200 µJ pulse energy as well as >50 W average power at wavelength of 1064 nm. In addition, it includes TimeShift™ ps technology, which allows burst mode operation with variable subpulse separation time; the intensity of each sub-pulse, the spacing, and number of sub-pulses within the burst envelop can be varied while still maintaining the same maximum output power.

See Application Note 37 for more information.


Burst Machining of Copper and Stainless Steel

While picosecond lasers are commonly used to machine high bandgap materials such as glass and sapphire, they are increasingly being used to machine materials such as metals and semiconductors as well. To avoid excessively high fluence levels which can cause thermal damage, one can increase the beam size or simply operate at a higher pulse repetition frequency (PRF). Both cases, however, require increased scanning speeds to avoid cumulative heating and at some point equipment such as AOM deflectors or polygon scanners is required, thereby increasing system complexity and cost.

Two metals that are widely used in a variety of important industries are copper and stainless steel. With its excellent electrical conductivity, copper is used as a conducting medium in various electronics applications such as PCB and flex-PCB manufacturing as well as advanced electronics packaging. In addition, copper has excellent thermal conductivity and is used as a cooling medium not only in macro-scale applications, but also in smaller scale applications such as thermoelectric coolers (TECs) and cooling LEDs. Stainless steel is valuable in many industries due to its combination of high strength, corrosion resistance, and bacterial resistance. In automobile manufacturing, laser drilling of fuel injector nozzles is a large and growing application, particularly for ultrafast lasers. It is also used extensively in medical device manufacturing where lasers are used for cutting, drilling and marking. In addition, laser machining of stainless steel molds for industrial printing and embossing of intricate textures is a large and growing application space. Both copper and stainless steel have relatively low ablation thresholds and hence splitting a single pulse into multiple pulses should prove to be beneficial.

Process Solutions for Metals

Copper and Stainless Steel Machining Solutions

For "burst” processing of copper and stainless steel, Spectra-Physics’ IceFyre® picosecond laser platform excels, due to its highly tailorable pulse output made possible by TimeShift™ ps technology. The IceFyre 1064-50 laser offers >200 µJ pulse energy as well as >50 W average power at wavelength of 1064 nm. In burst mode operation, the temporal spacing, number of pulses within the burst envelop, and the shape of the burst envelope can be widely varied while still maintaining the same maximum output power, a unique capability among competing products.

See Application Note 41 for more information.

Plastics and Polymers

Cold laser ablation of dielectrics, such as polymers, is an attractive way to form clean and precise patterns. The use of direct writing with ultrashort pulsed lasers permits the generation of two-dimensional microstructures with arbitrary patterns that can be used in as diverse fields as biomedical devices, MEMS, and microfluidics. Although laser ablation with ultrashort pulse lasers can be applied successfully to several types of polymers, typical materials are polycarbonate (PC), polyimide (PI), polymethylmethacrylate (PMMA), polyethyleneterephthalate (PT), and polytetrafluoroethylene (PTFE).

Process Solutions for Plastics and Polymers

Micromachining with ultrashort pulse lasers present several advantages versus more conventional methods that use continuous-wave or long pulse lasers. The two advantages that make micromachining with ultrashort pulse lasers unique and attractive from a production point of view are the ability to create micron and sub-micron features size and the almost complete elimination of collateral damage in the surroundings of the machined pattern. Furthermore, because polymer ablation is a direct laser writing process it is capable of creating complex microstructures on large areas without the need of masks and tools. Hence, micromachining of polymers with ultrashort pulse lasers is an enabling technology for the fast prototyping of devices presenting novel geometries and novel materials as well.