Visualization of alignment marks on a chip covered by a pre-applied underfill

摘要

Structures and methods for improving the visualization of alignment marks on an underfill-covered chip. A feature is formed on a chip, and an underfill material is applied to the chip at a wafer level so that the feature is covered the feature. The feature includes a first structural element comprised of a first material and a second structural element comprised of a second material that is electrochemically dissimilar from the first material to provide a galvanic cell effect. Filler particles in the underfill material are caused by the galvanic cell effect to distribute with a first density in a first region over the first structural element and a second region of a second density over the second structural element. The first density in the first region is less than the second density in the second region such that the first region has a lower opacity than the second region.

主权项

1. A structure comprising:
a chip; a feature on the chip, the feature including a first structural element comprised of a first material and a second structural element comprised of a second material that is electrochemically dissimilar from the first material to provide a galvanic cell effect; and an underfill material applied to the chip and covering the feature, the underfill material including a plurality of filler particles distributed in a first region of a first density over the first structural element and a second region of a second density over the second structural element, wherein the first density in the first region is less than the second density in the second region such that the first region has a lower opacity than the second region.