Flux free Flip Chip Attach technology for BGA/CSP packages

The solder Flip Chip Attach without flux using plasma treatment has been developed in order to eliminate the flux residue cleaning process for manufacturing the BGA/CSP packages. The plasma treatment is composed for roughening the solder surface and improving the solder wettability. Argon gas added hydrogen(Ar+H2) plasma has been very superior to argon plasma for etching/roughening the solder surface, therefore, a mixed gas plasma composed of carbon tetrafluoride and argon or oxygen(CF4/Ar or CF4/O2) has modified the solder surface for good solderability without damage to the Si chip, the passivation film and the organic substrate because of the active solder surface. After the Si chip was mounted on the organic substrate with the solder bumps treated with plasma, the solder bumps were reflowed at 230°C and underfilled. Package reliability has been demonstrated by the temperature cycle test (TCT) and temperature humidity bias test (THB) and this flux free flip chip attach technology with plasma treatment has been sufficiently verified such that it can be applied to packaging processes.