Longitudinal Ultrasonic Bonding of Electrodes between Rigid and Flexible Printed Circuit Boards

Abstract

In this study, two electrodes between a flexible printed circuit board (FPCB) and a rigid PCB (RPCB) are bonded using longitudinal ultrasonic vibration. The surface finish of the electrode of the RPCB is fixed as an electroless Ni/immersion ALL (ENIG), whereas two different surface finishes, are employed for the FPCB: immersion Sn and ENIG. Electrodes of the RPCB and FPCB are successfully bonded using longitudinal ultrasonic vibration. While a continuous intermetallic compound (IMC) of(Cu(x)AU(1-x))(6)Sn(5) is formed at the ENIG/Sn interface, a Au-Ni-P reaction layer is formed with an un-bonded region at the ENIG/ENIG interface. The peel strength of the ENIG/Sn joint is higher than that of the ENIG/FNIG joint. Results of peel tests show that the bonding conditions have a significant effect on joint integrity. [DOI: 10.1143/JJAP.47.4300]