For this CSP type, the limiting factor is based on the minimum manufacturing capability of the leadframe supplier in geometry definition and thickness. Although the construction and assembly process is similar to that of a conventional package, the CSP technologies leveraged are the leadframe fabrication where the terminals are etched and the fine-pitch control needed for wirebonding. The package is basically constructed as an extension of the wafer fabrication process rather than a separate back-end assembly process. The SCSP is designed to reduce the package size to almost the size of the semiconductor device. It is also designed to cost a fraction of typical assembly cost, because packaging can be done before dicing.
Encapsulation is done at the wafer level, on bumped wafers, using a new transfer molding technique.
The result is a package only slightly larger than the chip itself. The ideal requirements for a CSP include small size, fit with an existing infrastructure and low cost. A 48-pin SCSP is 9.0 x 4.5 x 1.0 mm at 0.75 mm BGA pitch. By way of comparison, the TSOP measures 18 x 12 x 1.1 mm. In addition to the small size and the use of proven infrastructure, investments to develop the package are minimal, with unit pricing targeted to be competitive with other CSPs.