Investigation Into the Durability of Stencil Coating Technologies
Paper addresses durability of coatings in relation to the number of print cycles and underside wipe cycles and materials used on the underside wipe process.
Production Floor
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Authored By:
Greg Smith and Tony Lentz
FCT Assembly
Summary
It is well documented that Nano coatings on SMT stencils offer many benefits to those assembling PWBs. With reduced standard deviation and improved transfer efficiency nano coatings can provide, there is also a cost. As PWB assemblers work to justify the return on investment, one key question continues to arise. What is the durability or life of these coatings and what can be done in the print process to maximize the life of the coatings?
This paper addresses durability of the coatings in relation to the number of print cycles and underside wipe cycles applied as well as materials used on the underside wipe process. Different parameters will be applied and data will be collected. The results of this study will be summarized to help those using or considering the use of these nano coatings to improve their print process and suggestions will be given to maximize the life of the coatings.
Conclusions
Nano-coatings provide many benefits to the solder paste printing process including improved transfer efficiency, decreased standard deviation in the print process, reduced need for underside and stencil cleaning and reduced occurrence of bridging. These benefits last only as long as the nano-coating remains functional and since these coatings are nanometers to a few microns thick, users must understand they do not last indefinitely. Damage to coatings can occur thru both mechanical and chemical processes applied to the stencil during the assembly process, and once damage begins, it continues at an increased rate until the stencil no longer out performs an uncoated stencil.
There are ways to extend the life of the nano-coating on the stencil and to ensure excellent print performance by following the recommendations above. Finally, new technology is being studied to combine both types of nano-coatings into one technology that will offer the best benefits of each type of coating and possibly improve the overall durability of the coating.
Initially Published in the IPC Proceedings
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Comments
1, before the nano coating, the passivation of stainless steel sheet. Increase the adhesion of the coating. Prolonged use. 2, the coating thickness can be increased by two times.
Guo Qing Hui, Sunshine Laser & Electronics Technology Co.,Ltd
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