The input/output density of dies, such as processors, is continually increasing. In order to keep up with the increasing input/output densities the package substrates to which the dies are attached must also scale correspondingly. Under the current state of the art, a single surface finish is applied to both a die and a land side of a package substrate. The die side of a package substrate is the side on which the die attaches, while the land side of a package substrate attaches to a circuit board. This single surface finish may grow, or expand, laterally after application which may cause pad-to-pad bridging on the die side of the substrate if the pads are located too closely together. Therefore, the expansion of the surface finish on the die side limits the scalability of the package substrate. The surface finish composition on the land side, however, may be dictated based upon considerations related to circuit board connection requirements. These considerations do not necessarily extend to the die side connection requirements; however, under the current state of the art the same surface finish is applied to both the die side and the land side of the package substrate.
USPTO Backgrounds
USPTO Backgrounds