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50 SMT Magazine • February 2014 summarY: the smt print process is now very mature and well understood. however, as consum- ers continually push for new electronic products, with increased functionality and smaller form fac- tor, the boundaries of the whole assembly process are continually being challenged. abstract The next generation of miniaturised SMT devices waiting to make their mark will require the assembly community to rethink its pro- cesses and toolsets. The feature sizes that are in- volved in this new wave of miniaturisation are sub-200 microns. To put this into context, only a decade ago this would have been considered a Semicon domain. Of all the process involved within the sur- face mount assembly process the printer is certainly the most sensitive to these changes. But it's not only about printing miniaturised features—the process engineer has to balance miniaturisation with the requirements of "stan- dard" technology. Thus we are experiencing the age of heterogeneous assembly. Therefore, the miniaturisation program is causing the print process to be challenged in new ways, especially the impact on the avail- able process window available to achieve high- yield heterogeneous assembly. This paper will investigate the impact of miniaturisation and heterogeneous assembly on the print process and strategies for assem- blers to keep one generation ahead. In recent research work, actual paste deposit volumes and transfer efficiency have been monitored and compared for both square and round apertures with area ratios ranging from 0.20–1.35. This covers apertures sizes of between 100 and 550 microns in a nominal 100-micron thick stencil foil. In addition, the effect of ProActiv ultra- sonically activated squeegees has been assessed as part of the same experiment. A further com- FEATUrE by Clive ashmore, Mark Whitmore and Jeff Schake DEK PrINTINg MAChINES lTD Big Ideas on... ...Miniaturisation

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