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The passage around this formula

The arithmetic behind that reputation is straightforward and still governs every multi-die package built today. A packaged part’s yield is not the yield of its worst component; it is the product of every component’s yield together with the yield of the assembly step that joins them. Write the package yield $Y_{\text{pkg}}$ as a function of the assembly yield $Y_{\text{assy}}$ and the yield $Y_i$ of each of N individual die placed into the package: $Y_{\text{pkg}} = Y_{\text{assy}} \prod_{i=1}^{N} Y_i$. Multiplication is unforgiving at scale. Every die added to a package is another factor less than one, so a package holding several die each individually manufactured at a very respectable yield can still fail at an uncomfortable rate…

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