Reliability Criteria for Thick Bonding Wire

Abstract

Bonding wire is one of the main interconnection techniques. Thick bonding wire is widely used in power modules and other high power applications. This study examined the case for extending the use of traditional thin wire reliability criteria, namely wire flexure and aspect ratio, to thick wires. Eleven aluminum (Al) and aluminum coated copper (CucorAl) wire samples with diameter 300 μm were tested experimentally. The wire response was measured using a novel non-contact method. High fidelity FEM models of the wire were developed and validated. We found that wire flexure is not correlated to its stress state or fatigue life. On the other hand, aspect ratio is a consistent criterion of thick wire fatigue life. Increasing the wire aspect ratio lowers its critical stress and increases its fatigue life. Moreover, we found that CucorAl wire has superior performance and longer fatigue life than Al wire.

Finite element modeling and analysis of ultrasonic bonding process of thick aluminum wires for power electronic packaging

“…Such simulation requires an in-depth understanding of packaging materials, key processes, and influential parameters. So far, relevant studies are mainly focused on the mechanical and microstructure properties of thick aluminum (Al) bonding wires [11][12][13], reliability tests containing thermal cycling, power cycling, and other accelerated lifetime tests (ALT) [14], etc. Meanwhile, with the support of finite element simulations [11,15], the fatigue behavior related to the material properties in the thick bonding wires was investigated in detail [16,17].…”

“…So far, relevant studies are mainly focused on the mechanical and microstructure properties of thick aluminum (Al) bonding wires [11][12][13], reliability tests containing thermal cycling, power cycling, and other accelerated lifetime tests (ALT) [14], etc. Meanwhile, with the support of finite element simulations [11,15], the fatigue behavior related to the material properties in the thick bonding wires was investigated in detail [16,17]. A large number of failure modes were recorded to provide the basis for bond wire aging assessments [17], comparative analysis of aging mechanisms, and ALT.…”

“…Fatigue lifetime was found to be influenced by wire diameter [18], junction temperature swing [14], monitoring current [14], aspect ratio of the wedge, etc. [11]. It is clear that parameters of the process are key factors affecting the reliability of thick Al wire bonding.…”