Simultaneously printing the redistribution layer and filling of TSVs using a microengineered screen

This article reports the results obtained by screen printing through a microengineered electroformed nickel screen to successfully fill TSVs and print a redistribution layer on Si wafers. Redistribution lines were deposited down to 40μm width at 70μm pitch. Straight through hole sections on the microengineered screen formed a stencil/screen hybrid region enabling TSVs to be filled down to 8.5:1 aspect ratio. However multiple print passes were required to completely fill the vias. Rheological properties of the printing medium play a major impact on the print printing performance.