Simple and low-loss flip-chip bonding based on ink-jet printing for RF applications

In this Letter, a flip-chip bonding based on ink-jet printing technology is proposed and verified by interconnecting a separated coplanar waveguide (CPW) samples. Before the flip-chip bonding process, diameter and height of ink-jet printed silver bumps for flip-chip bonding are measured to be about 300 and 13 μm, respectively. In a frequency range from 300 kHz to 3 GHz, return loss and insertion loss of the flip-chip bonded CPW samples are measured to be higher than 20 dB and lower than 1.8 dB, respectively, where the length of the signal line is 35 mm. There are negligible discrepancies between radio frequency (RF) characteristics of the flip-chip bonded CPW and those of a conventional CPW. These results show that the proposed flip-chip bonding can be used to integrate RF components into electronic devices with low-loss using simple procedures.