Abstract:The paper gives an overview of the concepts, basic requirements, and trends regarding packaging technologies of power modules in hybrid (HEV) and electric vehicles (EV). Power electronics is gaining more and more importance in the automotive sector due to the slow but steady progress of introducing partially or even fully electric powered vehicles. The demands for power electronic devices and systems are manifold, and concerns besides aspects such as energy efficiency, cooling and costs especially robustness and lifetime issues. Higher operation temperatures and the current density increase of new IGBT (Insulated Gate Bipolar Transistor) generations make it more and more complicated to meet the quality requirements for power electronic modules. Especially the increasing heat dissipation inside the silicon (Si) leads to maximum operation temperatures of nearly 200 o C. As a result new packaging technologies are needed to face the demands of power modules in the future. Wide-band gap (WBG) semiconductors such as silicon carbide (SiC) or gallium nitride (GaN) have the potential to considerably enhance the energy efficiency and to reduce the weight of power electronic systems in EVs due to their improved electrical and thermal properties in comparison to Si based solutions. In this paper, we will introduce various package materials, advanced packaging technologies, heat dissipation and thermal management of advanced power modules with extended reliability for EV applications. In addition, SiC and GaN based WBG power modules will be introduced.

In this study, the electrochemical corrosion property was measured by increasing Sb contents. The corrosion property of Sn-5Sb, Sn-8Sb, Sn-10Sb, Sn-8Sb-3Ag solder alloys was measured using polarization test. The polarization curves were measured in 3.5 wt. % NaCl solution of 25 ℃. Ag/AgCl and platinum were used by reference electrode and counter electrode, respectively. Corrosion potential (E corr), corrosion current density (I corr) and linear polarization resistance (LPR, R p) were estimated from the anodic and cathodic tafel lines. SnSb IMC was more diffused in the β-Sn structure by increasing Sb contents. Also, SnSb and Ag 3 Sn IMC was diffused in the β-Sn structure at Sn-8Sb-3Ag solder alloy. The corrosion potential (E corr) and corrosion current density (I corr) was increased by increasing Sb contents. But, the linear polarization resistance (LPR) was decreased by increasing Sb contents.

In this study, a Ag sintered joint was applied to replace the high-Pb solder to bonding materials between Aluminum Nitride (AlN) substrates and terminals used in wafer bake processes. The Ag sintered joint was fabricated using an optimized temperature profile. The high-Pb solder specimens were fabricated using a conventional reflow process. An X-ray analysis and mechanical properties evaluation of the specimens were performed. Subsequently, a high temperature storage test was performed for a high temperature reliability evaluation. The initial void analysis result showed that the Ag sintered joint and high-Pb solder joint had approximately 1%, and 20% voids, respectively. After being stored at a high temperature of 280 ℃ for 1000 h, the shear strength of the high-Pb solder joint decreased by approximately 27% owing to the Pb degradation. However, the shear strength of the Ag sintered joint was maintained. After 1000 h of a high temperature storage test, growth of Ni3Sn4 intermetallic compound and Kirkendall voids were observed at the high-Pb solder interface. Furthermore, a Ag-Au layer was observed at the sintered Ag interface. In addition, the sintered Ag joints densificated after the high temperature storage test.

Joint properties of Sn-Cu-(X)Al-(Y)Si lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-(0.01, 0.03)Al-0.005Si(wt.%) alloys were then fabricated in the form of solder balls for reflow samples. To evaluation of solder joint properties, solder ball was attached to PCB finished with OSP Cu pad. The reflow process was performed for 40 s above 260.5 ℃. And solder joint was evaluated by repeating the reflow process up to 10 times. The melting temperatures of Sn-0.7Cu, 0.01 Al-0.005Si and 0.03Al-0.0.005Si were 227.5, 230.2 and 231.4 ℃, respectively. Initial microstructures are composed of β-Sn regions surrounded by eutectic networks with spherical Cu 6 Sn 5 IMC particles. However, with the increasing Al content, refined eutectic β-Sn + Cu-Sn IMC networks were observed. The shear strength of Sn-0.5Cu-0.03Al-0.005Si solder joints was higher than Sn-0.5Cu-0.01Al-0.005Si and Sn-0.7Cu solder after 10 reflow test.