Fluxless Flip Chip Bonding Tech Application for Ultra-High Density Micro-bump Structure

In flip chip assembly technology, flux is widely used to clean the bonding surface and provide good wetting environment between solder bumps and substrate conductive pads. In the high density of micro-bump structure, flux is hard to completely remove by using the tradition flux clean equipment, the flux residues will hinder interfacial adhesion of underfill when underfill dispensed in solder joint protection, it may cause the underfill delamination on the flux remaining location. In order to avoid the delamination problem, some solutions have been found such as new underfill material development or flux clean equipment upgrade. However, among those solutions chip directly bonding without applied flux would be the most effective method to avoiding the delamination. In this paper, we introduce the thermal compression bond equipment with fluxless technique in ultra-high density micro-bump structure, and optimize the operation parameter to get the good solder wettability, and enhance bonding accuracy and process throughput. Obtains good solder wetting performance, and then pass the reliability test without underfill delamination defect during thermal aging cycles.