A packaging structure for an optical sensor with drill holes formed directly below an underfill layer includes a substrate having a plurality of drill holes, a plurality of vias, a plurality of traces, a plurality of gold wires, an underfill layer, a die having a plurality of bonding pads, and a container for isolating the die from the ambient atmosphere. The plurality of vias are formed within the plurality of drill holes and the plurality of bonding fingers are formed on the substrate. The plurality of traces formed on the substrate couple the plurality of bonding fingers to the plurality of the vias. The plurality of gold wires couple the plurality of bonding pads to the plurality of bonding fingers. The underfill layer is formed between the die and the substrate for die attachment, wherein the plurality of the drill holes are formed below the underfill layer.
