IC packaging technology retrospective
All IC packaging technology structures since the invention of the integrated circuit itself have been tasked to perform, at a minimum, the simple and fundamental tasks of interconnecting and protecting the semiconductor die and making it useful for interconnection at the next level. Packaging the IC was an important hurdle to clear, and IC packaging spawned a great deal of innovation to tackle the problem of making interconnection of these miniature devices practical for those wishing to design with them to make useful electronic products by the integration and interconnection of the different IC devices. Making the interconnections between chip and package or substrate and doing so reliably was that an important early task that caused scientists and engineers of the era to explore. A variety of different methods were examined, yielding interconnection solutions that are still in use conceptually today, though those early techniques have been significantly improved upon over the ensuing decades. For evidence of the efforts of that time, one need only look back at patent records, which reveal that the techniques now so common, including wire bonding and flip chip, were being practiced shortly after integrated circuits made their debut. Figure 1 shows early patent drawings for making basic electrical interconnections to semiconductor devices using methods that are all, for all practical purposes, still in use today.
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