Reliability investigations on LIFT-printed isotropic conductive adhesive joints for system-in-foil applications

• Reliability characteristics of isotropic conductive adhesive joints in surface mount technology applications are studied.
• Adhesive dots are deposited using laser-induced forward transfer printing as well as industry standard stencil printing.
• Reliability of laser-induced forward transfer printed adhesive joints benchmarked against stencil printed joints.
• The test methods used are: thermal shock, accelerated humidity, flexural and die shear testing.

The reliability of a commercially available isotropic conductive adhesive (ICA) deposited via laser induced forward transfer (LIFT) printing is reported. ICAs are particularly important for surface mount device (SMD) integration onto low-cost, large-area system-in-foil (SiF) applications such as radio frequency identification (RFID) transponder tags. For such tags, and for SiF in general, the reliability of the printed interconnects under harsh circumstances is critical. In this study, the reliability of surface mounted resistors bonded onto screen-printed conductive circuitry on polymer foil was assessed. The prepared samples were subjected to thermal shock testing (TST), accelerated humidity testing (AHT) and flexural testing, while electrical measurements were conducted at regular intervals. Die shear testing was performed to evaluate the bond strength. The reliability characteristics of the LIFT-printed samples were benchmarked against current industry standard stencil printing process. Finally, the applicability of the LIFT–ICA process for practical applications is demonstrated using RFID transponder integration and testing.