Electroplated Sn-Au Structures for Fabricating Fluxless Sn-Rich Joints Research

Electroplating

Good economical alternative for vacuum deposition. (Low cost)

Can go beyond the thickness limit that vacuum deposition have

Low processing temperature (40C ~ 60 C) Prevents unwanted diffusion and reaction between Sn and Au 

 

Fluxless flip chip solder bonding

Conventional flip chip processes need resin flux to remove oxides and hold solder bumping devices.

 Flux residues degrade the reliability of the device due to corrosion.

 Flux residues interfere with the flow of underfill encapsultnts and adhesion.

 As interconnection density increases and pitch decreases, flux residues are more difficult to remove.

 

Bonding principle of Sn / Au solder joints

SAM and SEM images of joints