High density R2R Screen Printed Silver Interconnections for Hybrid System Integration

In this case study, we investigated the minimum line width and spacing for roll-to-roll (R2R) screen printed silver interconnections on polyethylene terephthalate (PET). This initial pilot investigation involved rotary screen printing 16 high density I/0 patterns while alternating pitch (150, 175, 200, and 250 µm) and nominal screen linewidth (50, 75, 100, 150 µm).
Based on those results, we chose the Asahi silver nanoparticle ink and StorkS305 screen to compare three printed chip bonding test patterns utilizing a nominal line width of 75 µm (average printed line width was 115 µm), and a pitch of 150, 175 or 200 µm. Flip chip bonding of daisy chain bare dies was used to compare the effect of gold stud bumping and the choice of anisotropic conductive adhesive (ACA). Even though gold stud bumps ensured reliable connections, the choice of the ACA for unbumped chips proved uncertain, which has provoked ongoing and future investigations.
The results of this study shed significant and valuable light on high throughput R2R fabricated hybrid systems and necessary steps to be considered for future high density rotary screen printed hybrid electronic applications.