Influence factors of warpage reduction of thin dies by capillary action

Abstract

This paper examines a new technology to overcome the warpage of thin dies during electronics assembly. A liquid is encased in the gap between substrate and die, which acts as capillary. Consequently the die is planarized due to capillary pressure caused by the capillary action in the gap. Influencing factors on this effect, like gap height, level and orientation of die warpage, volume of liquid and the kind of the used liquid, were investigated. It was found that the success of the planarization depends strongly on the warpage orientation of the die. In case of a concave warpage orientation the technology is sensitive on the volume of the liquid, the gap height and of the warpage level in the initial state. In contrast, the planarization works significantly better for a convex warpage orientation and is less sensitive to parameter changes. The reasons for these differences were explained by a mechanical beam model.