Micron Technology, Inc.
Two-step solder-mask-defined design

Abstract:

An apparatus for a BGA package includes a pad mounted on a substrate. The apparatus also includes a solder resist layer disposed over the substrate and a buffer layer disposed over the solder resist layer. The solder resist layer can have a first aperture and the buffer layer can have a second aperture. The first and second apertures are aligned such that at least a portion of the pad is exposed to create a solder-mask-defined mounting pad. A diameter of the second aperture is larger than a diameter of the first aperture.