Effect of electronic flame off parameters on copper bonding wire: Free-air ball deformability, heat affected zone length, heat affected zone breaking force

Effect of EFO parameters and superimposed ultrasound on work hardening behavior of palladium coated copper wire in thermosonic ball bonding

“…Thus, the FAB deformability is increased when I EFO is increased. This result is similar to the results obtained previously [11,12] where deformability of constant diameter Cu FABs increased with the increase of I EFO . In [16], the correlation between force-to-targetdeformation and H DEF is studied.…”

“…The increase of EFO current shows decrease of FAB work hardening during the deformation in Cu wire [11,12]. Also, US can induce a decrease of FAB working hardening of Cu wire [13,14].…”

“…The previously reported on-line method is used to evaluate FAB deformability by measuring FAB height (H FAB ) as illustrated in Fig. 1a and b, and deformed FAB height (H DEF ) [11][12][13][14][15][16].…”

Investigation of growth behavior of Al–Cu intermetallic compounds in Cu wire bonding

“…On account of the soaring price of Au in recent years, enormous efforts have been devoted in the electronic packaging industry to replacing Au by Cu wire. However, technical issues such as the need and control of forming gas during FAB formation [2][3][4][5][6][7][8][9][10][11][12][13], underpad damage caused by the much stiffer FAB [2,[13][14][15], Al pad splash that may lead to short circuit in fine-pitch applications as well as degraded reliability [2,13,16,17], slow AlCu intermetallic compound (IMC) formation and growth [3,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], and long-term reliability under humid environments [7,10,18,22,28,35,36] have been considered as significant technical challenges for Cu wire bonding.…”

“…Mechanical strengthening of Al pad is usually achieved by impurity doping of 1%Si [2,3,23], 0.5-4%Cu [11,28], or 1%Si-0.5%Cu [3,20,22,26,30]. On the other hand, stiffness of Cu wire and FAB can be lowered by using annealed [35], high-purity [16], or micro-doped wire [14], and through an adequate electronic flame-off (EFO) process [13,37]. The IMC formed in the bonding process concerns with the wire bondability and mechanical reliability, and the IMC formation and growth are greatly affected by the process parameters including bond force, heat, and ultrasonic energy.…”