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For decades, wire bonding has played a dominant role in the microelectronic packaging industry [1] . After many years of research, wire bonding technology has gained popularity. It is now widely used in advanced and complex electronic packaging applications [2] . Quality improvement and cost reduction are always hot topics when higher requirements are placed on products. Excellent electrical and thermal conductivities, satisfactory tensile strength, and low cost make Cu the mainstream wire bonding material in the electronics field [3, 4] . However, Cu is not always suitable because it may cause material squeezing [5-7] (via the drill hole made by the Cu wire on the substrate) and impact the region underneath the pad during the wire bonding process. In such a case, Ag wire is a good alternative that can also significantly reduce costs [8, 9] . Ag is an important electrical contact and welding material with the highest electrical and thermal conductivities among metals. In addition, due to the excellent performance of some Ag and sintered-Ag alloys [10, 11] , Ag has a strong competitive edge in the electronics field. To ensure the best product quality, Au is the most frequently used wire bonding material. Due to its antioxidant property, Au has hardly any metal oxides on the surface, which are quite troublesome in wire bonding as these oxides prevent direct metal-metal contact and microweld formation. Also, Au has been used in various fields, such as wire bonding [12] . Different products'different choices of materials, according to their working environment and desired effects, can help reduce cost while guaranteeing high quality. Therefore, the performance of different materials during wire bonding processes needs to be investigated.
Studies have investigated the performance of Cu, Ag, and Au in wire bonding. Khoury et al. investigated Cu and Au's electrical performance and reliability in wire bonding, summarizing Cu and Au results [13] . Yoo et al. studied Ag wire bonding reliability with various bond pad materials [14] . Additionally, Zhang et al. studied the high-temperature reliability of Au wire bonding [15] . These studies indicate the reliability and performance of materials in wire bonding at a macroscopic level.
Molecular dynamics (MD) simulations help analyze atomic behavior and observe local changes at the atomic level. This makes MD a suitable tool to investigate the mechanism of wire bonding [16-19] . MD simulations could help verify and investigate the wire bonding mechanism at an atomic level. Li et al. investigated nanoindentation behavior of nanocrystalline Cu using MD simulation [20] . Abdeslam studied the effect of Ag inclusions on the mechanical behavior of Cu-Ag nanocomposites during nanoindentation using MD simulations [10] . Gu et al. studied the mechanism of microweld formation and breakage during Cu-Cu wire bonding using MD simulation [3] . However, the performance of various materials and their mechanisms in wire bonding is still unknown. Recently, heterogeneous integration has also been applied to solve the problem when a single material hits the bottleneck in improving its properties. Therefore, the current study has carried out a comprehensive study of the mechanism of typical wire bonding materials and a summary of various wire-substrate material pairs.
In this chapter, six material pairs are simulated, and the loading force, total energy, atomic configuration are observed to reveal the mechanisms of microweld formation and breakage. Critical values are also discussed to provide corresponding suggestions for the industrial process.