Bromine- and chlorine-induced degradation of gold-aluminum bonds

Abstract

The presence of bromine (Br) in flame retardant epoxies accelerates the degradation of gold-aluminum wire bonds. This experiment tests degradation by adding 5 wt.% 2,6-dibromophenol to the regular molding compound and holding thermal aging at 175°C and 205°C in ovens for up to 1,008 h. The intermetallic degrading microstructure was examined at different aging times. In order to better understand the mechanism behind the degradation, bulk Au 4 Al and Au 5 Al 2 single-intermetallic phases were prepared and reacted with molding compound at 205°C. The reactions were analyzed by a JEOL (Japan Electron Optics Ltd., Tokyo) Superprobe JXA-8900R under wavelength-dispersive spectrometry of x-ray mode. A similar chloride degrading study was performed by adding Tetrachlorobisphenol A to the regular molding compound. The results show that Br attacked the Au 4 Al phase first and then the Au 5 Al 2 phase. The chloride reacted with the Au 4 Al phase only.

Corrosion Study and Intermetallics Formation in Gold and Copper Wire Bonding in Microelectronics Packaging

“…The likely intermetallic phases to be corroding in Cu/Al wire bonding would be CuAl and Cu 9 Al 4 due to the lower proportion of Al in the intermetallic [12]. In the case of Au/Al wire bonding, Au 4 Al was shown to corrode in the presence of Cl − [16,17]. The intermetallics measurement at different storage durations (120 h, 240 h, 360 h and 480 h) and temperatures (175 °C , 200 °C and 225 °C ) are shown in Figure 9.…”

High‐Reliability Connection Products for Packaging Technology in Microelectronics

“…Another possibility as to the origin of the corrosion by mode E could be that Cl decomposes only Au 4 Al and reacts with the Al of the pad to form Al(OH) 3 .…”

Understanding materials compatibility issues in electronics packaging

“…Reactions between Au wire and Al pad metallization and the high temperature degradation of the bonds have been studied widely [19][20][21][22][23][24]. Different failure mechanisms proposed include Kirkendall voids due to unequal material fluxes [19] and contamination induced corrosion [20][21][22].…”

“…Different failure mechanisms proposed include Kirkendall voids due to unequal material fluxes [19] and contamination induced corrosion [20][21][22]. Specifically, the Au 4 Al intermetallic has been reported to be susceptible to dry corrosion, whereas other AuAl intermetallics react either more slowly or are not impacted [21,22]. Addition of small amount of Cu in the wire material has been shown to have a positive effect on the wirebond strength after aging [23,24].…”