Rapid formation of Cu/Cu3Sn/Cu joints using ultrasonic bonding process at ambient temperature

Abstract

Wafer bonding using Sn interlayer and silicon bond components with Ti/Ni/Cu metallization was achieved by ultrasonic bonding at ambient temperature for 4 s under 0.6 MPa. High-melting-point joint which fully consisted of Cu3Sn intermetallic compounds was formed with a high shear strength of 65.8 MPa and a low electrical resistivity of 67.3 μΩ · cm. Experimental results showed that ultrasonic vibration induced steep temperature rise at rubbing interface, melting solid solder, and sequent ultrasonic effects at the liquid Sn/solid Cu interface dominated the mechanism and kinetics of rapid formation of Cu3Sn joint.

Rapid formation of intermetallic joints through ultrasonic-assisted die bonding with Sn–0.7Cu solder for high temperature packaging application

“…Propagation of ultrasonic waves in a molten alloy medium will result in complex ultrasonic effects and dramatically affect the physical-chemical interactions at the liquid/solid interfaces [25][26][27]. Over the years, flip chip packaging with solder bumps using pre-heated ultrasonic bonding was also studied [28,29], but reports of successful ultrasonic-assisted soldering of die bonding are very rare.…”

“…Ultrasonic-assisted soldering/bonding has been proven able to form chip interconnection at a low temperature within a very short bonding time [24][25][26]. Propagation of ultrasonic waves in a molten alloy medium will result in complex ultrasonic effects and dramatically affect the physical-chemical interactions at the liquid/solid interfaces [25][26][27].…”

“…According to EDS analysis, the IPs were Ag 3 Sn and Cu 6 Sn 5 . Propagation of ultrasonic waves in a liquid medium could generate acoustic cavitation phenomena [25,29], and the ultrasonic effects are primarily derived from this acoustic cavitation, which includes the formation, growth, and rapid implosive collapse of micro-bubbles. In addition, the bubble collapse leads to the emission of shock waves [30][31][32].…”

Phase transformation between Cu(In,Sn)2 and Cu2(In,Sn) compounds formed on single crystalline Cu substrate during solid state aging

“…As an important metallurgical bonding layer between a soldering alloy and the substrate metal, intermetallic compound (IMC) layer takes obvious effect on the reliability of solder joints. [1][2][3] Till now, many researchers have worked on leadfree solders and investigated the nucleation and formation of IMCs during soldering [4][5][6][7][8] as well as the growth kinetics of IMC layers during solid-state aging process. [9][10][11] It is known that the growth of IMC layers plays an important role in the life of a packaging structure in microelectronic applications.…”

Rapid formation of Cu-Sn intermetallic compounds by strong electric current

“…However, the bonding time was about 30 minutes, which was timeconsuming. Mingyu Li et al [9] presented a rapid formation approach of Cu/Cu3Sn/Cu joints using ultrasonic bonding process at ambient temperature. They obtained the full IMCs joints by bonding process for 4 s under 0.6 MPa and the shear strength of joints was up to 65.8 MPa.…”