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48 PCB007 MAGAZINE I MARCH 2020 effect of heat on the material. Having this level of control over the beam allows for the pro- cessing of newer materials that are more prone to thermal issues such as delamination and di- electric or adhesive etch-back since increasing beam velocity allows adequate pulse spacing to avoid excessive heat accumulation (Figures 2 and 3). Natural laser energy fluctuations during la- ser processing must be mitigated to ensure the best possible quality and yield. This is espe- cially important in sensitive depth-controlled applications—such as blind via processing— with thin, easily damaged, or delaminated cop- per on the bottom capture layer. Alternatively, this is also important in applications where the easily-processed dielectric is very thin (e.g., 15 µm or less), allowing for very little margin of error for overdosing the dielectric and start- ing to damage the underlying copper. The best methods of avoiding such energy fluctuations include real-time laser energy monitoring and compensation during processing, as with ESI's Precision Pulse™ technology. Addressing Rising Production Costs With factory floor space at a premium and the cost of adding capacity increasing, productivity is a key area of focus. Systems that substan- tially increase throughput can delay the need to add more systems and enable PCB manufac- turers to avoid the costs of acquiring new land, floor space, permits, and resources associated with expansion. New systems can match the capacity of previous-generation systems with fewer units. Reducing the number of machines needed can also reduce overhead costs in both utility usage and personnel requirements. Improving laser system productivity can not only come from effectively using higher-pow- ered lasers, as discussed previously, but also from reducing unproductive time spent mov- ing the laser beam between features. Preparing to start laser processing with actions such as aligning to features on the workpiece and per- forming maintenance on the system also adds additional processing time. Enhanced beam positioning—such as ESI's Third Dynamics™ technology, which decreases the time required to move the laser beam be- tween features to be processed on the work- piece—is one way to minimize unproductive move time. Another more recent development in beam manipulation can have an even more dramatic impact on move time for processes requiring multiple effective spot sizes, such as blind via formation. The ability to instantaneously shift the la- ser's focus, thereby changing the effective la- ser spot size, as with ESI's DynaClean™ feature, eliminates the need to pass the beam over each of the workpiece's features twice—one time in focus, and one time out of focus. The effective result is a 50% reduction in move time. Advanced scale compensation algorithms, coupled with state-of-the-art vision capabilities, Figure 2: Minimal etch-back at the adhesive/bonding sheet interface. Figure 3: Unacceptable etch-back due to a higher localized heating effect.

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