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MARCH 2022 I SMT007 MAGAZINE 13 2 November 2021 SEMICONDUCTOR ADVANCEMENTS In the mid-1960s, future Intel founder Gordon Moore discerned that the number of transistors that could fit onto an integrated circuit could be doubled every two years, allowing the production of ever more powerful semiconductor chips with greater cost efficiencies. As an empirical claim, Moore's Law held true for more than half a century. But the days of keeping pace with Moore's law are over. Silicon advancements have slowed, along with economic efficiencies. Instead, semiconductor designers are increasingly taking advantage of advancement of electronic interconnection within the packaging to achieve greater functionality and economic efficiencies they previously realized through silicon scaling. WHAT IS ADVANCED PACKAGING? Semiconductor chips are fragile and must be protected from thermal and mechanical stresses during operation. To provide this protection, chips are "packaged" using several different materials, mainly plastics. Once packaged, chips become active logic devices that perform computing and/or memory functions. Chips are just one of many different types of essential components within an electronic system. Protecting chips remains critically important, but advancements in packaging are now being driven by the need to leverage "on package integration" as an alternative technological path to the promise of Moore's Law. On-package integration is commonly referred to as heterogeneous integration which involves integrating multiple chiplets (logic or memory) in a single package. A chiplet is a functional circuit block fabricated on a wafer, typically in a smaller size than what would be possible in a system on chip. The chiplet can be applied to a substrate in a 2D configuration or stacked one on top of the other in a 3D configuration within a package to produce greater functionality and greater processing speed. One way to understand advanced packaging is by comparison to urban design. Simple business districts are characterized by modest structures with one purpose and simple connections internally (electrical, plumbing, telecom) and externally (streets, public utilities). In denser urban settings, designers need to make more efficient use of limited real estate, leading to taller building with more complex internal feature (elevators, energy and security systems) as well as external connections to support an increased number of occupants and business activities (e.g., higher-capacity utilities, streets and highways, parking systems). Likewise, simple electronics components may have relatively few internal parts and may be connected to one another via basic infrastructure such as printed circuit boards and wiring. More complex electronic systems require designers to pack more functionality into the semiconductor packages via more parts, layers, and interconnections. Connecting more chips within a multilayer package comes with new technological hurdles. Interconnects within a package can be as small as nine microns – on fifteenth the width of a human hair. ELECTRONICS ADVANCED PACKAGING: THINK OF A DENSE, MULTI-USE BUILDING