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Equation 4 · Chiplets and Advanced Packaging in Practice: An Advanced Technical Guide

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yiy_i

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the independent per-die yield. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.

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yiy_i

Symbol y_i

the independent per-die yield.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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which is a first-order model — it assumes bonding introduces no additional defects and that die yields are independent, both of which are simplifications addressed separately below. Even under this optimistic assumption, four chiplets each yielding 95% compose to roughly 81% assembly yield, and a twenty-die stack at the same per-die yield falls to roughly 35% — the industry’s own framing of why an unscreened stack becomes uneconomical fast as die count rises [ 4 ] . The entire purpose of KGD testing is to push each yiy_i as close to 1 as pre-bond screening allows, since the model shows the product is unforgiving of even small per-die shortfalls once several dies are chained together.

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