Investigation On Electrochemical Migration Of Sintered Nanosilver At High Temperatures In Dry Air

With the development of wide band-gap semiconductors, low-temperature joiningof semiconductor chips by the sintering of silver paste, a novel green packagingmaterial, is emerging as an alternative solution for die-attaching power electronicdevice, especially for high-temperature applications.This paper mainly studied the reliability of nanosilver paste in high powerelectronics applications at high temperatures to find ways to increase the reliability ofnanosilver paste in high power electronics applications at high temperatures.In this paper, we studied the formation of silver bridges during electrochemicalmigration of sintered nanosilver， we find that silver dendrites formed duringelectrochemical migration of sintered nanosilver grow from cathode toward anode.We observed the microstructure of silver bridges and found that the migrating silverbridges were presented as discrete silver particles on the surface of alumina substrate.The discrete silver particles preferentially emerged at the boundaries of the aluminaparticles at the initial stage. We proposed possible mechanism of electrochemicalmigration. Oxygen may play an important role in the migration of sintered nanosilverat high temperatures in our speculated mechanism.We defined the “lifetime” of electrochemical migration of sintered nanosilver,which is the time at which the leakage current first reaches1mA. We studied thedifferent effects of temperature, DC bias, electrode spacing, electrode types andsubstrates on electrochemical migration of sintered nanosilver. We find that the“lifetime” of electrochemical migration increase with the dc bias decreasing, electrodedistance increasing, and temperature decreasing. The “lifetime” of electrochemicalmigration of sintered nanosilver on alumina nitride substrate is longer than that on thealumina substrate. Based on the Arrhenius equation, we proposed a prediction modelof the “lifetime” of electrochemical migration and proposed the possible ways tomitigate the migration of sintered nanosilver.