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52 DESIGN007 MAGAZINE I SEPTEMBER 2024 tion becomes unsustainable for upgrading and expanding the functions and performance. Implementing 2.5D System in Packaging Technology To meet user demands, semiconductor developers continue their efforts to increase functionality and performance with each gen- eration of silicon-based die elements. ese same developers will then need to rely on the design engineer and semiconductor package engineering specialists to support this industry segment with timely and innovative solutions that can facilitate the new product offerings. With the advances in semiconductor imag- ing technology, the complexity of the individ- ual die element has increased exponentially. Package solutions developed for these more advanced product offerings must facilitate the higher density interconnect and enable redis- tribution of the semiconductor's narrow pitch terminal pattern to a broader terminal for- mat. A primary challenge for the circuit board design professional is how best to intercon- nect these higher I/O, very fine terminal pitch semiconductor packages. System-in-package developers have realized that instead of the traditional monolithic inte- gration developed for the earlier, less complex applications, adapting mature, high-yielding miniature semiconductor "chiplet" die to meet the system level criteria is more economical and can significantly reduce development time. A chiplet is an integrated circuit block that has been specifically designed to work with other similar chiplets. Clustering and interconnect- ing two or more associated heterogeneous or homogenous semiconductor die within the confines of a single package outline enables closer coupling and the potential for enhanced electrical performance. By positioning these smaller and less complex functional chiplets in close proximity to the monolithic processor die, interconnect distance will be minimized and power and ground distribution optimized (Figure 1). Most of the interface between the com- ponent(s) and package substrate interconnect is confined to the silicon-based interposer plat- form's surface. is, in turn, allows the termi- nal array on the bottom surface of the package substrate to expand to a wider pitch, simplify- ing the interconnect to the host circuit board substrate. Silicon-based 2.5D Interposers Higher I/O semiconductors, die elements, when furnished with a uniform array of raised terminals, enable direct-die attachment to the 2.5D interposer. e primary function of the interposer is to accommodate attachment and facilitate interconnect of related die ele- ments mounted to the interposer's surface. Some referred to this substrate as "grid trans- Figure 1: Heterogeneous silicon-based system-in-package. (Source: Skywater Technologies)