Study of the fluxing agent effects on the properties of no-flow underfill materials for flip-chip applications

As one of the key requirements of the no-flow underfill materials for flip- chip applications, a proper self-fluxing agent must be incorporated in the developed no-flow underfill materials to provide proper fluxing activity du ring the simultaneous solder reflow and underfill material curing. However, most of fluxing agents have some adverse effects on the no-how underfill m aterial properties and assembly reliability. In this paper, we have extensi vely investigated the effects of the concentration of the selected fluxing agent on the material properties, interconnect integrity, and assembly reli ability. Through this work, an optimum concentration window of the fluxing agent is obtained and a routine procedure of evaluating fluxing agents is e stablished.