This study investigated the feasibility of ultrasonic bonding of a rigid printed circuit board (RPCB) to a flexible printed circuit board (FPCB) with a non-conductive film (NCF) for improving the long-term reliability and lowering the manufacturing cost. Peel tests of the joints were carried out with increasing bonding time to optimize the bonding condition. High-temperature storage and thermal cycling tests were carried out to evaluate the reliability. The RPCB was successfully bonded to the FPCB with NCF using a transverse ultrasonic bonding. The optimum time taken for bonding was 3sec. The joints with NCF showed a good reliability after the high-temperature storage test at 125C for 1,000h and the thermal cycling test for 1,000cycles.