Due to the unbalance wetting effect of the molten solder during reflow, the die will move and result in non-uniform solder joint between die and substrate. In addition, conventional solder paste has difficulty to achieve a desired bond line thickness (BLT) for heave copper clip attach.
To improve the solder distribution uniformity and get desired bond line thickness, a novel die attach material will be discussed in this paper. This novel die attach material is a solder paste with addition of Cu sphere. The existence of the Cu sphere in solder paste will ease the unbalanced wetting force of liquidus solder during reflow process to minimize die tilt issue. The addition of Cu sphere will reduce the spreading of solder caused by the heavy weight of copper clip, it is helpful to obtain a higher bond line thickness for copper clip application.