ventional methods include shorter processing time, less expensive fi xtures, changes to hole diameters without changing “electrodes” or other “drill bits,” changes to hole locations by programming, and the ability to drill hard and nonconductive materials. Disadvantages of laser processing include pos- sible thermal damage to material, the need for post drill processes, potentially harmful vapors and initial capital equipment costs. Like any material removal process, optimization studies must be conducted to achieve the correct balance of cycle time, part quality, and part cost. The studies should focus on key process parameters for the material, and their effect on key quality char- acteristics of the part. Typically, wavelength, pulse width, energy/pulse and focal properties will have the biggest infl uence on hole quality. Optimal cycle time can be achieved by adjusting pulse repetition rate with two important caveats. The allowable adjustment is fi nite, in that pulse repetition rate will change the laser average power, and the beam quality of many lasers can change negatively with increased pulsing. Secondly, pulse repetition rate can change the sub- strate temperature through sidewall conduction and cause degradation in hole quality and time. In addition to the primary laser characteristics, there are multiple factors to consider for achieving a stable process. Beam quality, in conjunction with lens focal length and input beam diameter, will determine the focal spot size, and the depth of focus, essentially the “drill bit” diameter and length. Assist gases are also used for multiple reasons. One primary reason is to protect the lens or cover slide from ejected matter, but gas can also infl uence the drilling rate. Gases can also assist in removal (O2) or help reduce oxides (N). Pressure/fl ow will have to be balanced to protect the lens without suppressing the expelled material. Gases should be free of any moisture. Laser drilling has been demonstrated at aspect ratios (depth/diameter) of greater than 20:1.


Future Technological Development By Silke Pfl ueger, General Manager— Direct Photonics


Two main drivers are pushing the technologi-


cal development of lasers for material processing: Improving sources for traditional applications such as metal welding and cutting, and developing new sources for new applications, such as glass cutting. To increase the market for lasers in cutting and welding, laser developers are reinventing the way the radiation is generated. Modern laser sources are very reliable machines, used in production lines around the world. Size, effi ciency, and price are the main drivers for new laser development at 1 µm, with direct-diode lasers pushing into high brightness appli- cations. As an example of how specialized lasers are becoming, consider this: To enable a wider range of material to be cut, fi ber and disk lasers were devel- oped that have switchable beam quality to cut both thin and thick metal effi ciently. Ultrafast lasers are an example of new technolo- gies opening up completely new applications for lasers. They have now become production tools, cutting Gorilla Glass and sapphire in a manufacturing environment. Reliability, ease of use and a reduction in price are the main development drivers, ultimately enabling more applications and markets.


For more information about industrial laser use, visit our laser channel at MfgEngMedia.com


MfgEngMedia.com LF15


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