Meaning
Bonding processes join electronic components using silver particles that fuse at temperatures below their melting point without the application of external force. The adoption of pressureless silver sinter in power electronics allows for the creation of high-temperature interconnects that can withstand the demands of silicon carbide and gallium nitride chips. This technique relies on the high surface energy of silver nanoparticles to drive the diffusion process at the contact points.
The resulting bond is a solid silver layer with a melting point of nine hundred and sixty-one degrees Celsius, which is far higher than the original sintering temperature.
Thermal Diffusion
The sintering process begins with the evaporation of organic solvents and the subsequent breakdown of the surfactant coating on the particles. Once the silver is exposed, the atoms begin to move across the grain boundaries and create necks between the individual grains. In pressureless silver sinter, this movement is driven entirely by the reduction in surface area and the thermal energy provided by the oven.
Reliability Advantage
High thermal conductivity in the silver improves heat dissipation of the package and allows the device to operate at higher power densities. Because the joint does not melt until it reaches the bulk melting point of silver, pressureless silver sinter provides a stable connection that does not degrade under extreme thermal cycling. This property makes it a preferred choice for automotive and aerospace applications where reliability is the primary concern.
Production Constraint
Achieving a void-free bond requires careful control over the ramp rates and the atmosphere of the sintering furnace. If the heating is too fast, the rapid outgassing of the paste can create large internal pores that weaken the mechanical strength of the joint. Although pressureless silver sinter simplifies the assembly process by removing the need for complex clamping fixtures, it requires a longer processing time compared to traditional solder reflow.
Manufacturers must balance the improved performance of the bond against the lower throughput of the sintering station. The preparation of the substrate surfaces is also more demanding, as any contamination can prevent the silver particles from making the necessary contact to start the diffusion.
