Non Metallic Cutting with a Pulsed Fiber Laser
Although more typically used for marking, nanosecond Pulsed Fiber Lasers are ideally suited to cut a surprising range of materials. They are low cost, compact, reliable and require no maintenance.
The scanner based cutting process can be applied to a wide variety of non-metallic materials including ceramics, polymers and even carbon composites, as well as metals. This application insight specifically looks at non-metallic materials including silicon, ceramics, plastics and rubber, and shows examples of these materials cut with a Pulsed Fiber Laser.
Introduction
The short pulses and relatively high peak powers that can be achieved with directly modulated seed MOPA designs enable these Lasers to be effective tools to cut a variety of materials.
As an alternative to standard CW type cutting the Pulsed Fiber Laser can be used in a multi pass vaporisation type cutting process using a scanner to repeatedly pass over the cut line removing a small amount of material per pass. No nozzle or assist gas is required. This technique offers a flexible, accurate and very affordable solution. The equipment is basically a simple laser marking machines / system!
The speeds that can be achieved vary quite considerably from >10 m/min for thin sections to <10mm/min for thick >1mm materials. For cutting thicker materials special techniques that effectively widen the kerf width must be employed such as cut line off-setting or beam wobbling.
Compared to conventional Laser cutting these speeds may be slow but for many applications the low capital cost and the flexibility offered by ns pulsed fiber laser cutting/marking systems are highly attractive.
Results show that effective cutting can be achieved with all of our redENERGY Pulsed Fiber Laser models SM/HS/HM, but each exhibits slightly different cutting characteristics and selection is very much dependent on the material and the desired output. For example for very narrow kerf widths the high beam quality and small spot size of the SM is best suited, while for thicker materials the higher peak power and slightly larger spot size HM generally produces better results.
How to cut Silicon
Silicon is a material (technically a metal) that is widely used in the electronics and solar industries and here are numerous cutting applications. This material is conventionally diced or cut using mechanical diamond cutting wheels, however these have limitations on thinner materials and do suffer from chipping at the cut edges.
The Pulsed Fiber Laser offers a flexible alternative that can be used to cut complex profiles and shapes with ease. The 5mm squares were cut out in 6sec using 20W SM (Image 1).
Image 1. Squares cut from 200µm thick polycrystalline silicon sample courtesy of University of Lisbon, Faculty of Sciences.
Cutting Ceramics with lasers
There is a significant industrial requirement for cutting of ceramics. Within the electronics industry there is a lot of thin substrate material that is cut either through scribe and break or through cutting. Again the limitation is the absorption of the material.
The key materials are alumina and aluminium nitride and their ability to be cut with 1µm Lasers depends on the specific material and surface finish. An example that processes well is green AlN where small discs can be rapidly cut from substrates (Image 2 & 3).
Image 2. ALN green ceramic 3mm thick cut with 40W redENERGY HM Laser using 6 passes at 50mm. Image 3. Cutting and marking of 0.7mm Alumina ceramic with 20W redENERGY HS -courtesy of Orotig srl.
What Other Non metallic Materials can be Cut?
The Pulsed Fiber Laser can also be used to cut a wide range of non metallic materials such as plastics and even rubbers. A key factor in determining if a material can be cut is the level of the absorption of the material to 1µm Laser light. Many plastics have high transmission at this wavelength and are therefore not suitable, however, some materials can be cut. The use of IR absorbing additives to many polymers is becoming a more common place solution particularly for marking and in some cases these additives may enhance cutting. Some materials such as certain polyester and polyethylene can be cut but tests should be made to assess suitability. An example of plastic cutting is plastic labels which can be marked as well as cut out from the sheet with a simple change in processing parameters (Image 5).
Image 4. Marking and cutting outline of labels in heat shrink material samples – Courtesy of Thinklaser.
Other examples include the selective cutting of protective plastic sheathing that is typically found of metals such as in cables and wires (Image 5).
Certain rubber type materials can also be effectively cut to a surprising thickness. An example is a 4mm thick black rubber that was profiled with through holes of 1mm (Image 6).
Image 5. Generic insulating plastic cut from copper substrate using redENERGY 20W HS. Image 6. 4mm rubber cut with 20W redENERGY HS.
Can Composite materials be cut?
Composites such as carbon fiber materials can be cut in thicknesses in excess of 1mm however, processing conditions need to be tailored to the material as some are more sensitive to charring. Perhaps another alternative is the cutting of multi-layer materials. An interesting application is in the electronics industry where 20W redENERGY HS Lasers are used for component cross-sectioning. The flexibility of the Laser allows all of the different material layers to be cut successfully (Image 10).
Image 7. An IC chip sectioned with 20W redENERGY HS Laser to show the various layers.
Conclusion
Nanosecond Pulsed Fiber Lasers are ideally suited to vaporisation cutting applications. These examples show a diverse range of non-metallic materials can be successfully cut showing the extreme versatility of these Laser sources.
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