Hand Printing using Nanocoated and other High End Stencil Materials
This study details the effectiveness of nanocoating materials, high end stainless steel stencil materials, as they relate to the manual SMT printing.
Production Floor
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Authored By:
Bob Wettermann - BEST Inc
Summary
There are times when a PCB prototype needs to be built quickly to test out a design. In such cases where it is known early on that there will be multiple iterations or that a "one and done" assembly will be made that there will be some SMT assemblers who choose to hand print solder paste onto the board using a "frameless" stencil. In such cases where hand printing is used, the consistency of the printing technique has typically been in question. Furthermore, the effectiveness of both the nanocoatings as well as the higher end stainless steel materials, which have been heretofore studied in controlled printing environments, will be evaluated for their impact on the hand printing process.
Conclusions
The solder paste printing process is the area of the SMT assembly process where the greatest strides in improvement can be made with respect to yield. This is especially true in the case where several inputs to the manual printing process, are not controlled as in a machine-controlled printing process.
The high tension advanced stainless steel material provided the best release characteristics across all aperture sizes compared to the standard nickel-content small grain structure stainless steel. In addition, the printing volume was more consistent using this higher grade material. All the high tension material results were better than the high nickel content stainless steel stencils.
The addition of a nanocoating to the high nickel content stainless steel stencil did generally bring about higher print volume compared to an uncoated stencil. This was especially true of the thinner 3 mil stencil. However the consistency of the printing was lessened by the addition of a nanocoating for the thinner stencil.
Finally, it was demonstrated that each type of nanocoating material needs to be evaluated and confirmed for the manual printing process. In this study the nanocoating 1 material outperformed the nanocoating 2 material.
The higher grade high tension material had the best overall printing performance using a manual SMT printing process.
Initially Published in the IPC Proceedings
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