SMTA International Conference Proceedings

Comparison of Aperture Designs, Solder Pastes, Nanocoatings and Print/Inspection Systems

Authors: Chrys Shea, Jennifer Fijalkowski, Raymond Whittier, Michael Butler, Edward Nauss, Dean Fiato
Company: Shea Engineering Services, BAE Systems, ITWEAE/MPM, StenTech
Date Published: 9/22/2019   Conference: SMTA International

Abstract: To optimize aperture designs for miniaturized components with a legacy solder paste, an experiment was devised to test the transfer efficiency and repeatability of several aperture designs for 0402, 0201 and 01005 discretes, as well as 0.4 and 0.5mm BGAs. The twelve laser-cut stainless steel stencils that were tested included two different basic aperture designs on 4 and 5 mil thicknesses, with no coating, wipe-on nanocoating, and cured polymer nanocoating (2x2x3 full factorial). The solder paste driving the experiment was a tin-lead RMA product, developed at least 20 years prior, and presents as a high viscosity paste that is more challenging to print when compared with modern formulations.

The experiment was performed on the user’s assembly line using one set of printer and SPI equipment, and then replicated in the equipment supplier’s laboratory using a different printer and SPI gear. The results of each individual print test are discussed and then compared.

The experiment was then extended at the laboratory to include different solder pastes and show their response to different stencil designs, and potential for improving print capability of the assembly line.

Key Words: 

stencil printing, nanocoating, miniaturization, SPI, solder paste

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