Reliability of carbon nanotube bumps for chip on film application

Carbon nanotubes (CNTs) are an ideal candidate for electrical interconnects due to their extraordinary thermal, electrical and mechanical properties. In this work, as-densified CNT bumps were applied as chip on film (COF) interconnection material. A silicon chip with patterned CNT bumps was bonded onto a flexible substrate using anisotropic conductive adhesive (ACA) with bonding pressure, at 127.4 MPa, 170 °C and for 8 seconds. The electrical properties of this structure were evaluated by measuring the contact resistance of each bump using the four-point probe method. Thermal cycling (-40~85°C, 1000 cycles) and damp heat tests (85°C/85% RH, 1000 hours) were conducted to evaluate the reliabilities of the CNT-COF structure bonded with ACA. The average contact resistances of two samples used for the reliability tests were 226 mΩ and 260mΩ. No electrical failure was observed after the damp heat test and only two were observed after the thermal cycling test. The average contact resistance was increased only 15.7% and 13.8%, respectively, after the thermal cycling and the damp heat tests.