This paper presents a method of self-arranging solderballs by using surface energy difference. After evaporating Au which has high surface energy on Si substrates, Teflon passivation layer which has low surface energy was patterned by lift-off process...
This paper presents a method of self-arranging solderballs by using surface energy difference. After evaporating Au which has high surface energy on Si substrates, Teflon passivation layer which has low surface energy was patterned by lift-off process. Droplets formed only on the hydrophilic Au solderball lands by the surface energy difference, not the hydrophobic Teflon surface. Scattered solderballs sticked by themselves to the wetted solderball lands on the tilted substrate. After setting preheating of 200℃ and soldering of 245℃ hot plates, the solderballs were soldered on the solderball lands and two substrates were soldered together completely. After measuring the mechanical shear strength of the soldered substrates with solderballs of 3×3, 4×4 and 5×5 arrays. the calculated shear strength per one solderball was 1.1~2.4kgf as high as the previous report.