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62 SMT Magazine • February 2014 place. The data presented here indicates that with judicial choice of stencil design and ma- terials it will be possible for designers to work with aperture area ratios down to 0.4. To optimise a process it is becoming increas- ingly important that an engineer has a good un- derstanding of stencil aperture design specifica- tion, material properties and process options/aids available to him. The interaction between these facets is becoming more complex and critical to the successful implementation of a process. SMT references 1. IPC-7525, Stencil Design Guidelines, IPC, May 2000. 2. C. Ashmore, M. Whitmore, S. Clasper, "Optimising the Print Process for Mixed Tech- nology," Surface Mount Technology Interna- tional, San Diego, CA, October 2009. 3. R. Mohanty, "What's in a Squeegee Blade?" Circuits Assembly, May 2009. 4. G. Babka, S. Zerkle, F. Andres, R. Raut, W. Bent, D. Connell, "A New Angle on Printing", Global SMT & Packaging, February, 2009. 5. G. Burkhalter, E. Leak, C. Shea, R. Tripp, G. Wade, "Transfer Efficiencies in Stencil Print- ing" SMT May 2007. 6. Fleck, I., Chouta, P., "A New Dimension in Stencil Print Optimization," Surface Mount Technology International, Rosemont, Ill., Sep- tember, 2002. 7. W. Coleman, "Stencil Technology and Design Guidelines for Print Performance," Cir- cuits Assembly, March, 2001. 8. W. Coleman, "Paste Release vs Print Area Ratio," APEX 2001. 9. W. Coleman, M. Burgess, "Stencil Perfor- mance Comparison/AMTX Electroform vs. La- ser-Cut Electroform Nickel Foil," Surface Mount Technology International, October, 2006. 10. C. Läntzsch, "Nano Coated SMT Stencil with Anti-adhesion Effect," www.epp-online. de, 17.09.2008. 11. D. Manessis, R. Patzelt, A. Ostmann, R. Aschenbrenner, H. Reichl, A. Axmann, G. Klee- mann, "Evaluation of Innovative Nano-Coated Stencils in Ultra-Fine Pitch Flip Chip Bumping Processes," IMAPS 41st International Sympo- sium on Microelectronics, November, 2008. 12. M. Whitmore, C. Ashmore, "New Develop- ments in Broadband Printing Techniques," SMTA International, Orlando, USA, October, 2010. 13. M. Whitmore, C. Ashmore, "The Devel- opment of New SMT Printing Techniques for Mixed Technology (Heterogeneous) Assembly," 34th International Electronic Manufacturing Conference, Melaka, Malaysia, November 2010. 14. M. Whitmore, C. Ashmore, "Develop- ments in Stencil Printing Technology for 0.3 mm Pitch CSP Assembly," IMAPS 44th Inter- national Symposium on Microelectronics Long Beach, CA, October 2011. 15. IPC-7525B, Stencil Design Guidelines, IPC. Third edition, October 2011. Figure 9: Percent standard deviation plots for all experimental runs. FEATUrE bIG IDeaS ON MINIaTurISaTION continues