Cleaning-free flux for flip chip assembly

摘要

A method of assembling a substrate and die in a flip chip configuration using a no clean flux. The no clean fluxes have sufficient chemical activity to activate solder bumps contacting bond pads to form reliable solder joints, sufficient tackiness to hold the substrate and die in alignment with the solder bumps contacting the bond pads, and a viscosity to enable a high volume manufacturing process to be used. The no clean fluxes leave a minimal amount of residue during a reflow process that does not interfere with an underfill operation and does not adversely affect the solder joints. The no clean fluxes that can be used for this application are RM1919 from Alpha Metals, Co. and H208 from Indium Company.