Comparison of Flip-Chip Bonding Characteristics on Rigid, Flexible, and Stretchable Substrates: Part I. Flip-Chip Bonding on Rigid Substrates

To compare the flip-chip bonding characteristics on rigid, flexible, and stretchable substrates, the contact-resistance and microstructure of the flip-chip joints processed using anisotropic conductive adhesive (ACA) were characterized on rigid Si and glass substrates. The average contact resistance of a flip-chip joint substantially decreased from 39.3 m Omega to 17.2 m Omega when the bonding pressure increased from 10 MPa to 100 MPa, which was attributed to the deformation of the ACA conductive particles that were trapped between the chip bump and the substrate pad. The average contact resistance at a bonding pressure of 200 MPa was further improved to 5.9 m Omega because of direct contact between the Au layer of the chip bump and the Cu substrate pad. After such direct contact occurred, the contact resistance hardly changed even when the bonding pressure increased to 300 MPa.