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ssss1 shows an example of electromigration‐induced damage in Cu interconnects. The high current density in the interconnect has induced a flow of atoms along the electron flow direction, going from the cathode to the anode, leading to vacancy accumulation and void formation in the cathode region. Resistance of the interconnect increases gradually until an opening in the circuit occurs, where the resistance increases dramatically.

ssss1 An example of electromigration electromigration‐induced failure of void formation in Cu interconnects. (a) Electrons drifted from the bottom Cu line to the top Cu line. (b) Electrons drifted from the top Cu line to the bottom Cu line.

In the near future, the R&D of packaging technology for 3D IC devices will be the focus. The role of electronic packaging in Si‐based microelectronic technology is getting more and more important. In turn, reliability will be of major concern. The introduction of AI to facilitate the applications to new 3D IC devices and the reduction of the time‐consuming reliability tests will demand our concentrated effort. In the long run, the applications of electronic packaging technology to biomedical devices will be important. For example, as people lives longer, diabetes is common in old age. To determine oxygen content and sugar content in our blood, we use invasive method to obtain a drop of blood from our finger for measurement. It is very unpleasant! If we can invent a noninvasive method, for example by wearing a mobile device around our finger or arm, it will greatly reduce the unpleasant feeling in our daily live if we have diabetes. Even better, if we can implant a small device in our body to perform the blood testing function, we will need to understand the interfacial interaction between biological and nonbiological materials. In other words, we will need to study bio‐compactable materials, as well as the chemical reactions in body fluid at body temperature. Furthermore, we may need to join a biomaterial to a non‐biomaterial. To do so, we may need a low‐temperature solder or binder which can decompose slowly in the body. However, the melting point of the common Pb‐free solder, the eutectic SnAg, is over 200 °C, to be discussed in ssss1 on solder joint reactions. We may need a new solder whose wetting temperature is around 100 °C, which is above the working temperature and near the body temperature, for biomedical devices. While these issues are beyond the scope of this book, we note that the future of electronic packaging technology has a long way to go.