Ultrasonic power features of wire bonding and thermosonic flip chip bonding in microelectronics packaging

Abstract

The driving voltage and current signals of piezoceramic transducer (PZT) were measured directly by designing circuits from ultrasonic generator and using a data acquisition software system. The input impedance and power of PZT were investigated by using root mean square (RMS) calculation. The vibration driven by high frequency was tested by laser Doppler vibrometer (PSV-400-M2). And the thermosonic bonding features were observed by scanning electron microscope (JSM-6360LV). The results show that the input power of bonding is lower than that of no load. The input impedance of bonding is greater than that of no load. Nonlinear phase, plastic flow and expansion period, and strengthening bonding process are shown in the impedance and power curves. The ultrasonic power is in direct proportion to the vibration displacement driven by the power, and greater displacements driven by high power (>5 W) result in welding failure phenomena, such as crack, break, and peeling off in wedge bonding. For thermosonic flip chip bonding, the high power decreases position precision of bonding or results in slippage and rotation phenomena of bumps. To improve reliability and precision of thermosonic bonding, the low ultrasonic power (about 1–5 W) should be chosen.

Keywords

ultrasonic power / wedge bonding / thermosonic flip chip / input impedance / failure

References

[1] LI J, HAN L, DUAN J, ZHONG J. Interface mechanism of ultrasonic flip chip bonding [J]. Applied Physics Letters, 2007, 90(24): 242902.

[2] LI Jun-hui, HAN Lei, ZHONG Jue. The characteristics of ultrasonic vibration transmission and coupling in bonding technology [C]// Proceedings of the 6th IEEE CPMT Conference on High Density Microsystem Design and Packaging and Component Failure Analysis. Shanghai, 2004: 311–315.

[3] ElgerG., HutterM., OppermannH.. Development of an assembly process and reliability investigations for flip-chip LEDs using the AuSn soldering [J]. Microsystem Technology, 2002, 7(5): 239-243

[4] TAIZO T. Thermosonic flip chip bonding for low cost packaging [C]// 2002 International Symposium on Microelectronics. Denver, CO, United States, 2002: 360–365.

[5] LiJ. H., HanL., ZhongJ.. Interface structure of ultrasonic wedge bonding joints of Ni/Al [J]. Trans Nonferrous Met Soc China, 2005, 15(4): 846-850

[6] WinchellV. H., BergH. M.. Enhancing ultrasonic bond development [J]. IEEE Trans Hybrids, Manuf Technol, 1978, 3: 211-220

[7] LiJ.-h., HanL., ZhongJ.. Microstructural characteristics of Au/Al bonded interface [J]. Materials Characterization, 2007, 58(2): 103-107

[8] DuanJ.-a., LiJ.-h., HanL., ZhongJ.. Interface features of ultrasonic flip chip bonding and reflow soldering in microelectronic packaging [J]. Surface and Interface Analysis, 2007, 39: 783-786

[9] TsujinoJ., SanoT., OgataH.. Complex vibration ultrasonic welding systems with large area welding tips [J]. Ultrasonics, 2002, 40(1/8): 361-364

[10] TsujinoJ., YoshiharaH., SanoT.. High-frequency ultrasonic wire bonding systems [J]. Ultrasonics, 2000, 38(1/8): 77-80

[11] LiJ.-h., HanL., ZhongJ.. Observations on HRTEM features of thermosonic flip chip bonding interface [J]. Materials Chemistry and Physics, 2007, 106(2/3): 457-460

[12] TsujinoJ., HongohM., TanakaR.. Ultrasonic plastic welding using fundamental and higher resonance frequencies [J]. Ultrasonics, 2002, 40(1/8): 375-378

[13] TsujinoJ., KoichiH.. Ultrasonic wire bonding using high frequency 330, 600 kHz and complex vibration 190 kHz welding systems [J]. Ultrasonics, 1996, 34(4): 223-228

[14] TsujinoJ., YoshiharaH., KamimotoK.. Welding characteristics and temperature rise of high frequency and complex vibration ultrasonic wire bonding [J]. Ultrasonics, 1998, 36(2): 59-65

[15] KangS. F., WilliamsP. M., MclarenT. S.. Studies of thermosonic bonding for flip-chip assembly [J]. Materials Chemistry and Physics, 1995, 42(3): 31-37