Investigation on fluxless laser jet bumping technology

The effect of the technology parameters(laser current,laser pulse time and N2 pressure) for fluxless laser jet bumping on the bump's peel strength under N2 protecting conditions were investigated;the interfacial microstructure and composition of the intermetallic compound at bump(Sn63Pb37)/pad(Au/Ni/Cu) were analyzed in term of scanning electron microscopy and energy dispersive spectrometer.As the laser pulse time is constant,the peel strength decreases with increasing laser current;as the laser current is constant,the peel strength increases with increasing laser pulse time.In case of obtaining good bump's appearance,larger laser current along with shorter pulse time results in the decrease of bump's peel strength,smaller laser current along with longer pulse time increases bump's peel strength.Under existing test conditions,solder ball(Sn63Pb37) may wet the pad(Au/Ni/Cu) commendably.The continuous AuSn4 intermetallic compound layer is formed at the bump/pad interface and AuSn4 is detected in the solder pump near the interface.