Dispensable 3D Electrical Interconnects - A Near TSV Back end Packaging Solution

As packaging densities increase, lead by the requirements of smaller footprints, higher storage capacity, and multi-functional 3D die structures, traditional wire-bonding techniques become inadequate and thru silicon via (TSV) is not a cost effective solution for packaging houses. This paper discusses the benefits of dispensing the electrical interconnects instead of using traditional wire bond or high cost TSV processes. Dispensing electrical interconnects allow form factors for stacked packages to reach near TSV dimensions. Offsets to expose die pads are typically <150μm and in some cases totally vertical structures can be achieved.

Material selection will vary according to pitch and electrical requirements. Methods for applying the different materials will be discussed as well as material selection criteria. The progression from large pitch applications of >300μm down to fine

pitch applications of <100μm will be shown. Data will be presented stating the benefits for each material set and how the use of any of these dispensable electrically conductive fluids can be implemented into typical back end packaging houses using equipment that in most cases is already installed.

The non-contact nature of the dispensable electrical interconnect process allows for thinner die to be stacked without fear of cracking the stacked die. Furthermore, the entire die stacking process can be executed in a single step minimizing overall material

handling and repetitive die stack processes that induce die crack and expensive yield losses.