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November 2016 • The PCB Magazine 73 STEPPING UP TO LASER PROCESSING FOR FLEX, PART 4: INSTALLATION, TRAINING AND INITIAL OPERATION cessing area inside the system, and is not escaping through any gaps in the system's cabinet when the shrouds and doors are closed. They also en- sure that safety interlocks are functional and trip at the appropriate time, and that all emergency machine off (EMO) buttons are operational. Major subsystems: Verifies the proper functioning of subsys- tems such as computer, power supplies, sensors, debris removal, etc. Laser and laser chiller: Verification of laser and chiller functional- ity, including laser power levels, chiller temper- ature stability and chiller coolant levels. This ensures that the laser will continue operating according to its specifications and avoids pre- mature service interventions. Optics quality and alignment: Laser spot quality and laser power transmis- sion through the optics path can be affected by optics that may have become contaminated, damaged or misaligned during shipment. Given the importance of laser spot quality and spot size in high-quality via formation, verification of items such as optics alignment, beam diam- eters and laser spot quality is critical. Motion/accuracy/kinematics: Verification of stages, galvanometers, and camera accuracy calibrations as well as motion and control loop functionality ensures that the process features will be placed accurately and formed correctly with precise beam positioning. Laser power stability and control: Correctly calibrated and functioning power control ensures the best possible yields, espe- cially for blind vias and other depth-limited processes on sensitive materials. At an absolute minimum, calibration of the system's power measurement sensors against a certified, cali- brated external power meter is required. Other tests related to system laser power control and laser power stability further verify how much laser power variability your process engineers will have to build into their process develop- ment calculations. Assuming these tests have been completed and no issues are documented, the system has met the supplier's own system specification cri- teria. If demonstration applications had been developed by your supplier prior to the system sale, this is often a good time to verify that the applications show similar quality on the system that you are purchasing as compared to those previously seen in the demonstration results. After the completion of these tests, the system will typically be released for your use. Training and Safe Tool Operation Now that the system is ready for use, how do you use it? At a minimum, your operators will require training related to basic tool opera- tion. On-site operator training is typically of- fered by your supplier's service or applications team, complementing a copy of the operator guide. These should cover safe operation of the tool, including laser, electrical, mechanical, chemical safety, functionality and the proper use of safety interlocks and EMOs. This should Figure 3: Examples of common laser system safety labels. Figure 2: A typical EMO button.