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The passage around this formula

That second half of the trade is where yield risk concentrates. If a bonded interface carries N individual interconnects and each has an independent probability $\pi$ of a bonding defect — misalignment, particle contamination, or a void — then the probability the whole interface bonds cleanly falls as $Y_{\mathrm{bond}}(N) \;\approx\; (1-\pi)^{N}$. Because N itself grows as roughly 1/$p^{2}$ under the density relation above, $Y_{\mathrm{bond}}$ falls unless the per-interconnect defect probability $\pi$ improves at least as fast as the pitch shrinks — which is precisely the motivation behind Chen and Gupta’s YAP+ framework, a pad-layout-aware yield model for copper-copper hybrid bonding that accounts for misalignment, particle…

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