###### Abstract  
Electrochemical migration (ECM) of sintered nano-Ag could be a serious reliability concern for power devices with high-density packaging. An anti-ECM nano-Ag-SiO\({}_{\mathrm{x}}\) paste was proposed by doping 0.1 wt% SiO\({}_{\mathrm{x}}\) nanoparticles rather than previously used expensive noble metals, e.g., palladium. The ECM lifetime of the sintered nano-Ag-SiO\({}_{\mathrm{x}}\) was 1.5 to 3 times longer than that of the sintered nano-Ag, due to the fact that the SiO\({}_{\mathrm{x}}\) could protect the Ag from oxidation. The thermomechanical reliability of the sintered nano-Ag-SiO\({}_{\mathrm{x}}\) was also improved by sintering under 5 MPa assisted pressure. The lesser porosity and smaller grain boundaries of the sintered nano-Ag-SiO\({}_{\mathrm{x}}\) could also be beneficial to retard the silver ECM. In the end, a double-sided semiconductor device was demonstrated to validate the better resistance to the ECM using the sintered nano-Ag-SiO\({}_{\mathrm{x}}\).  
electrochemical migration; ionic migration; sintering; nanosilver; doping; Ag nanoparticles; reliability +
Footnote †: journal: Applied  
in conventional printed circuit boards (PCBs) [4, 10]. Double-sided cooling (DSC) silicon carbide (SiC) power devices have attracted more and more attention in industries, especially in electric vehicle applications, because of their superior heat dissipation capability and power density [11]. However, the DSC SiC devices have a very small electrode spacing, e.g., 250 \(\mu\)m [12]. When the great sintered nano-Ag was used as die attachment in the DSC SiC devices, it is crucial to avoid the ECM failure of sintered nano-Ag to guarantee the reliability of electric vehicles. Unfortunately, there is a current lack of research on the ECM of silver suppression for the DSC SiC power devices.  
Inhibition of the ECM of silver, such as alloying silver with indium or copper to form anti-ECM Ag-In and Ag-Cu alloys, had been studied [13, 14]. Recently, we proposed the method of alloying silver with palladium aimed at inhibiting the formation of silver ions through oxidation and decomposition in the anode to delay the ECM of silver [15]. However, these alloying methods need very high processing temperatures in order to improve the resistance to the ECM of silver by alloying more at the higher temperature, not to mention the extremely high cost of indium, palladium, and so on.  
In this paper, a nano-Ag composite paste was proposed with the 0.1 wt% SiO\({}_{\mathrm{x}}\) nanoparticles (NPs) as fillers. The conventional nano-Ag paste was compared as a reference. The lifetime for reaching the ECM failure was characterized in the first place. Then the thermo-mechanical reliability of the proposed nano-Ag-SiO\({}_{\mathrm{x}}\) paste was verified in the aspects of die-shearing strength and thermal impedance by thermal shocking tests because it is critical to ensure promising thermo-mechanical reliability besides the improvement of the resistance to the ECM. Microstructures and porosity were analyzed to clarify the effects of SiO\({}_{\mathrm{x}}\) doping on the ECM and the thermo-mechanical reliability. In the end, the proposed nano-Ag-SiO\({}_{\mathrm{x}}\) paste was used as a die attachment for a DSC power device. The improvement of the lifetime of the ECM was validated in the high power density demonstration.