Lasers in Micro-manufacturing

Laser processes have continued to be used for a considerably long time for specific micro-manufacturing processes. This is because there have been several decades of such applications in development through which conventional manufacturing approaches could not satisfy the major demands relating to accuracy and flexibility. On the other hand, the outstanding share of micro applications across the entire laser market has extensively been a minor segment through which laser cutting as well as welding have proven to be dominant within the laser application sector.1 As a result of the increasing trend towards miniaturization, as well as higher integration for diverse consumer products, laser processes are well becoming more important under which laser micro manufacturing continues to show a considerably high market increase.7 These developments are both fostered by the strong market pull and the availability of lasers that are very high quality. This consequently allows a specific deposition of energy across a micrometer scale which remains at high processing speeds. On the other hand, laser technology greatly lowers operational costs, enables easy installation as well as lowering maintenance costs which continue making lasers a more versatile tool for application within industrial micro manufacturing processes.

Apart from the existing areas of application for laser micro processing across fine mechanics and defined electronics, there are current megatrends towards considerable energy savings and health as well as global information through which the society has developed numerous laser applications. 6 Within the scope of production of distinctly highly effective laser drilling processes used on solar cells, the laser thin film ablation coupled with laser joining aspects have been processes that continue providing high processing speeds and low energy deposition. For the medical implants, the recently developed technologies in this area allow the due generations of specifically patient implants that are based on actual data.3 For the broadband communication, packaging technologies that are low temperature laser based are well suited for the high accuracy joining regarding optical fibers, micro lasers as well as closely related electronic components. Increasingly, this trend towards higher thermal stability for purposes of numerous application areas such as automotive as well as the sensor industry continue leading to a substantive change in the joining of technologies from soldering towards welding, where lasers can be used.

Further, laser joining of metal and polymer components using the Laser-Induced Fusion Technology (LIFTEC) process has turned to be a versatile tool in the packaging of a diverse scope of materials. The grounds of all these emerging laser applications make reference to the availability of the highly flexible laser sources as well as the optical equipment developed by fast and flexible laser light shaping for the stipulated time and space.3 Some of the newly developed process variables such as Twist, LIFTEC and Shadow as well as subsequent beam sources that have high beam quality and fast modulation capability qualify the laser application as a universal tool in this totality. Also, this could be as a result of the new wavelength regimes. The large range of materials which are processed through lasers spread out from microelectronics materials such as silicon as well as other semiconductors where hard materials including tungsten carbide used for tool technology and the very weak and soft materials such as polymers used for medical products are engaged. It is through this advancement that even diamond, glass and ceramics can be produced using laser technologies that have accuracies of less than 10 μm. In the previous years, laser processes were especially used for both medium and small lot sizes as a result of their high selectivity’s even though they were strongly increased materials across the geometry variability’s.6 Currently, the laser micro processing has become one of the tools for mass manufacturing through which the high quality as well as a significant increase of the levels of efficiency where lower energy consumption as compared to other manufacturing technologies have been noted.

Laser Micro Manufacturing for New Markets

More to the specific micro processing requirements of the miniaturized parts, most of the new products that arise from various demands of the overall energy savings will especially require both fast and selective manufacturing processes. This is because there is need to have them fulfilling a highly efficient laser technology in the long run. Among the available options in this context, the photovoltaic industry is one of the most mentioned in this line of technology. This is because it continues to use high quality lasers used for diversely different applications surrounding the manufacturing and production of solar cells as well as solar modules.5 Currently, laser based edge isolation is used in bulk silicon cells as well as thin film ablation in P1, P2 and P3 processes which are essentially industrialized laser processes. Focusing on the future, processes such as laser joining, texturing and doping will be on the increase efficiency as they will help in cutting the manufacturing costs.4 Away from this, fuel cells as well as high energy batteries will require fast packaging and surface structuring technologies that have minimum heat input as well as show elements of high speeds for a maximum flexibility coefficient in meeting the scale of integration and functionality in terms of demand.

Further, the manufacturing of these technologies display will require an overly selective thin film ablation accompanied by material transformation processes that are only provided by the new laser sources as well as laser processes that are material adapted. For the above applications, it is essential to note that manufacturing technologies are necessary in enabling performance of specific processing steps in the exclusion of the influence of the overall product material properties. The technologies become essentially out of place in the event that they are made from or allow the easy integration towards mass manufacturing lines across high production rates.2 More to it is the fact that the different processes need to be used in a fundamentally flexible way for purposes of enabling the customization of functions and properties of the stated parts in line with the increment of mass customizing requirements.

For purposes of fulfilling the requirements of such applications, the lasers as well as laser systems that have the capability of depositing energy through the very selective means and ways are needed. For micro ablation and ultra-short pulsed lasers with highest precision embracing pulse durations within the range of 10 ps are qualified for ablation using very low debris formation. The lasers which have these pulse specifications were available only at considerably lower power level in previous decades. However, today, newest results continue to show that even the power levels of 50 W at fundamentally repetition rates of around 4 MHz are made possible (Kunz et al. 18). The recent developments from research institutes and the global laser suppliers indicate that even the laser powers developed from several 100 W will be made available in the years to come. With these laser sources the application of high speed ablation and functionalism will have a new scope of potential. According to Multi-Material Micro Manufacture, for individuals who are extensively involved in laser-based manufacturing, most of the aspects in micro-manufacturing are not new concepts simply due to the fact that they have undertaken the industry across years through which there has been a certain transformation in the volume-production scales. People who remain newly engaged to the concepts of laser-based manufacturing, it is critical to appreciate the fact that there are numerous and significant challenges involved in the same.

Laser Processes for Micro Joining of Metals, Polymers and Semiconductors
With respect to the ongoing increment in material diversification across miniaturized and highly integrated products, elements of laser joining are turning to be one central factor in the assembly processes. This is because it provides minimal influence on the various functionalities of the distinct parts as well as high levels of manufacturing effectiveness. On the other hand, laser beam welding has turned to be one of the common joining techniques for precision engineering resulting from the selective energy concentration surrounding the few 10–100 μm as well as the usage of a large scope of industrial applications. Therefore advantages within laser welding become widely spread.5 On the other hand, different metals need joining across the non-contact processes as well as the accessibility to the work pieces which are only possible from the set sides coupled with additional joining material components including adhesives and solders which have to be avoided. Moreover, the scope of laser beam joining continues to be an increasingly embraced feature of technology within electronics packaging as well as in the application of high levels of temperature as well as mechanical stabilities which have to be availed for and short joining times as requested.
Among the diverse laser joining technologies available, laser welding is established to be the most reliable process that has one of the largest field applications. This is applicable in the joining of metals and joining of polymers. For the wide range of applications, especially for packaging of electronics, the characteristic geometry within spot welding develops an overlap joint.6 All the joining partners need to be reliably connected even though they will often form the backside of the various parts which need to be molten. The full penetration of the lasers will have to be avoided simply due to the functional layers which are situated behind the aesthetic or connection aspects with regards to the visible surfaces. Single pulse conventional laser welding processes from heating and melting elements where the materials do not have any impact on the inherent molten material dynamics are evident.1 Therefore, all instabilities within the laser source, material conditions and beam guiding cause due elements of melt expulsions that have subsequent joining errors. Focusing on the copper welding, this becomes a typical phenomenon that was in the past a basic criterion developed to avoid laser welding which was a versatile tool in electronics packaging.

Laser Manufacturing for Solar Cell Solutions

For a while now, laser processes have continued to provide a minimum levels of reference to mechanical and thermal impacts on the processed products resulting from their selective aspects of energy control as well as the high processing speed in general. This way, they have turned to be well established for a wide scope of laser processes that are currently used in manufacturing solar cells. They are also applicable in the highest speed and maximum developments of in flexibilities of meeting the demands for the due scales of integration as well as functionality.5 Further, the manufacturing of Organic Light-Emitting Diodes (OLED) coupled with displays will require selective thin films which are critical in the ablation for material transformation processes that are only provided through new laser sources as well as material adapted laser processes. In all this manufacturing application technologies are needed for the purposes of enabling the performance of specific processing steps that do not influence the overall material properties of the products which are made from and allow ease in the integration of mass manufacturing lines into high production rates.4 Far from this, the various processes need to be used in more flexible ways in the customization of the functions as well as properties of the production parts with regards to developing an increment in mass customization requirements.

Using such laser sources, the high speed functionalism and ablation will embrace the potential for launching new areas which will be under further investigation especially for future cell concepts. This is especially based on high speed laser ablation that is currently one of the most preferred processes for the edge isolation in the manufacture of solar cells. Backside contacting through laser melting is beginning to be one of the aspects that are continuously introduced into industrial manufacturing lines via drilling Metal Wrap Through technologies.2 It is through the use of these technologies that there has been a considerable significant increment of manufacturing productivity as well as efficiencies of solar cells which are already achieved in the past. For further solar cell concepts and the increment of manufacturing speed as well as efficiency for even more laser processes, they are used for different micro-manufacturing processing steps for developing highly productive processes used in solar cell. They are also used in module manufacturing based on the reduction of costs as well as increment of production yields. Currently, there are various laser applications that are under investigation for considerably short time integration for the micro manufacturing processes including the micro ablation for doped surface layers and micro drilling for backside contacting. This goes hand in hand with laser soldering within the interconnection of solar cells onto various modules as well as new processes developed from the backside contact formation.1 In the long term, subsequent laser processes that have even more potential for the aspects of efficiency increment will be applied, similar to surface roughening as well as texturing for the improvement of light absorption and transformation to crystalline silicon from amorphous, lasers in micro manufacturing have greatly supported metallization within the improved current forms of management as well as laser supported selective doping.

References
1. Crafer, Autor C, and Oakley, Peter J. Laser Processing in Manufacturing. New York: Springer, 1992.
2. Fillon Bertrand, Khan-Malek, Chantai, and Dimov Stefan. Multi-Material Micro Manufacture. New York: Research Publishing Service, 2011.
3. Jain, V K. Micromanufacturing processes. New York: CRC Press, 2012.
4. Koc Muammer., Ozel, Tugrul. Micro-Manufacturing: Design and Manufacturing of Micro- Products. New York: John Wiley & Sons, 2011.
5. Krueger, Arnd, and Juchmann, Wolfgang. Miniaturizing microelectronics. The International Resource for Laser Material Processing, 2006. Web. 11 May 2013.
6. Kunz et al. Applications of lasers in microelectronics and micromechanics: Applied Surface Science, 1994; 80(2): 12-24.
7. Negro L D, and Boriskina, S V Deterministic a periodic nanostructures for photonics and plasmonics applications: Laser Photonics Review, 2011, pp. 1–41.
8. Qin, Yi. Micromanufacturing Engineering and Technology. New York: William Andrew, 2012.