Extended reliability of gold and copper ball bonds in microelectronic packaging

Abstract

Wire bonding is the predominant mode of interconnection in microelectronic packaging. Gold wire bonding has been refined again and again to retain control of interconnect technology due to its ease of workability and years of reliability data. Copper (Cu) wire bonding is well known for its advantages such as cost-effectiveness and better electrical conductivity in microelectronic packaging. However, extended reliabilities of Cu wire bonding are still unknown as of now. Extended reliabilities of Au and Pd-coated Cu (Cu) ball bonds are useful technical information for Au and Cu wire deployment in microelectronic packaging. This paper discusses the influence of wire type and mold compound effect on the package reliability and after several component reliability stress tests. Failure analysis has been conducted to identify its associated failure mechanisms after the package conditions for Au and Cu ball bonds. Extended reliabilities of both wire types are investigated after unbiased HAST (UHAST), temperature cycling (TC), and high-temperature storage life test (HTSL) at 150, 175, and 200°C aging temperatures. Weibull plots have been plotted for each reliability stress. Obviously, Au ball bond is found with longer time to failure in unbiased HAST stress compared to Cu ball bonds for both mold compounds. Cu wire exhibits equivalent package and or better reliability margin compared to Au ball bonds in TC and HTSL tests. Failure mechanisms of UHAST and TC have been proposed, and its mean time to failure (t 50 ), characteristic life (t 63.2 , η), and shape parameter (ß) have been discussed in this paper. Feasibility of silver (Ag) wire bonding deployment in microelectronic packaging is discussed at the last section in this paper.

Evolution and investigation of copper and gold ball bonds in extended reliability stressing

“…Figure 13 illustrates a Cu ball bond with lower package reliability margin and usually more susceptible to Cu moisture corrosion test under UHAST condition. This has been reported in our previous literature works [8,[25][26][27]31]. Cu ball bond has a layer of Pd coated on low-corrosive resistance Cu wire which inhibits moisture ball bond corrosion in UHAST conditions (130°C, 85 %RH).…”

“…Pd atoms in the Pd-coated Cu wire do not participate in the interfacial reaction, and have no marked effect on the growth rate of IMCs. Gan et al conducted studies on effects of bonding wires on UHAST and TC reliability and found Au with better UHAST reliability compare to Cu wire [25][26][27][28][29][30][31]. Au ball bond is well known with its Au atomic diffusion into Al metallization and caused resistive ball bonds with non-optimized bonding parameter [1,25].…”

A corrosion study of Ag–Al intermetallic compounds in chlorine-containing epoxy molding compounds

“…Moisture-induced corrosion at the Ag/Al bonding interface seems to be the root cause of this failure. Similar corrosion effect is also observed in Au-Al and Cu-Al wire-bonds [20][21][22][23]. The corrosion is strongly associated with halogen content, such as chlorine (Cl), in the epoxy molding compounds (EMCs).…”

Fatigue life evaluation of gold wire bonding solder joints in MEMS pressure sensors

“…While Al wire has the critical distinction with Au wire that the surface does not need to be heated, which make it suitable for temperature sensitive surfaces [11]. Gan et al [1,12] discussed the influence of wire materials on the bonding reliability, which found that the Au wire remained connecting for a longer time before failure than other materials even though with the disadvantage of expensive. Murali et al [13] aimed at the varying wire size and thermal aging periods, investigating the interface morphology and metallurgical behavior of the Au wire bonding area.…”