## 3 Results and Discussion  
The ECM experimental lifespan findings of the suggested nano-Ag composite paste and the control samples of conventional nano-Ag paste are listed in Table 1. According to Table 1, the nano-Ag-0.1%SiO\({}_{x}\) paste has a substantially longer failure lifetime than the nano-Ag paste under identical conditions. The 0.1 wt% SiO\({}_{x}\) doping in the original nano-Ag paste serves a critical function in preventing the silver from migrating electrochemically. Furthermore, the lifetime reduces greatly when the temperature and the electric field are increased. Figure 2: Fabrication process of the DSC demonstration and verification of electrochemical migration resistance for a DSC device using sintered nano-Ag-SiO\({}_{x}\) as die attachment. It was believed that the ECM behavior of the sintered nano-Ag at high temperatures initiates from the oxidation of the sintered anode and the decomposition of Ag\({}_{2}\)O [6]. When the temperature is constant, the higher the electrode voltage applied, the faster the Ag\({}^{+}\) formed after anodic oxidation. These Ag ions would reduce at the negative electrode as metallic Ag under the action of the electric field, resulting in the accelerated growth of conductive silver dendrites from the cathode and extended to the anode. As a result, the leakage current can be detected between the anode and the cathode. When the voltage remains constant, the higher the ambient temperature, the faster the ions travel. Then the produced Ag\({}^{+}\) speeds up the creation of silver dendrites under the specific electric field. Therefore, the ECM lifetime of the sintered nano-Ag-SiO\({}_{\rm x}\) in the temperature range of 573-673 K is 1.5 to 3 times that of the sintered nano-Ag. It was likely that the SiO\({}_{\rm x}\) covered on the silver, as shown in Figure 3a,b, should be susceptible to oxidation. The oxidation electrode potential of SiO\({}_{\rm x}\) oxidation to SiO\({}_{2}\), i.e., \(\sim\)0.06 \(V_{\rm SCE}\), was reported as more than one time lower than that of Ag oxidation to Ag\({}_{2}\)O, i.e., 0.13 \(V_{\rm SCE}\)[7; 19]. As a result, silver oxidation was reduced and the ECM was delayed. Figure 3c shows the change in shear strength following temperature cycling. The shear strength falls as the number of cycles increases. It should be noted that the shear strength of the Ag-SiO\({}_{\rm x}\) paste drops to less than 30 MPa after 600 cycles, but the shear strength of the nano-Ag control samples remains \(\sim\)30 MPa after 1000 cycles. It was likely that the atomic diffusion rate of Ag into Ag, i.e., \(\sim\)1.455 \(\times\) 10\({}^{-23}\) m\({}^{2}\)/s [20], is much higher than that of Ag into SiO\({}_{\rm x}\), i.e., \(-\)8.76 \(\times\) 10\({}^{-29}\) m\({}^{2}\)/s [21], resulting in an insufficient driving force for the sinter-bonding of Ag-SiO\({}_{\rm x}\) heterogeneous particles under the same pressure-free and sintering temperature conditions [22]. The Young's modulus of the SiO\({}_{\rm x}\) nanoparticles, on the other hand, is much higher than that of the Ag nanoparticles, and the thermal expansion coefficient is much lower than that of the sintered nano-Ag, so the interfacial bonds of the sintered Ag-SiO\({}_{\rm x}\) were subjected to thermo-mechanical stress fatigue during temperature cycling, eventually leading to its shear strength dropping faster in the case of pressureless sintering [23]. It was known the driving force for the sintering can be increased greatly if assisted pressure was applied [24]. An extra 5 MPa pressure was applied to promote the sintering of the Ag-SiO\({}_{\rm x}\) paste for better long-term reliability. Fortunately, the shear strength of the pressure-assisted sintered Ag-SiO\({}_{\rm x}\) can be kept at \(\sim\)35 MPa even after 1000 cycles. It was even higher than the shear strength of the nano-Ag control samples after 1000 cycles. It was believed that the pressure can ensure the better thermo-mechanical reliability of the nano-Ag-SiO\({}_{\rm x}\) paste.