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Equation 5 · Part 9 · Comparing the Main Approaches to Chiplets and Advanced Packaging

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ΔTj  =  P∑i=1NRth,i,\Delta T_j \;=\; P \sum_{i=1}^{N} R_{\mathrm{th},i},
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What this part means

A raised number can be a power. When it is a label or bound, it selects a case or the upper limit of a sum; the formula’s structure distinguishes these uses.

Its job in the formula

A raised mark can be a power or an index. Its position and the surrounding notation determine which.

The passage around this formula

The bill for that proximity arrives as heat, and it arrives in a specific, structural way rather than as a vague “3D runs hotter” intuition. A stack has exactly one face in contact with the package’s heat-removal path — typically the topmost die, under a lid or heat spreader — so the temperature rise at a given tier depends on everything the heat has to cross to reach that face: ΔTj  =  P∑i=1NRth,i\Delta T_j \;=\; P \sum_{i=1}^{N} R_{\mathrm{th},i}. where P is the power dissipated at that tier and each Rth,iR_{\mathrm{th},i} is the thermal resistance of one layer already between that tier and the heat sink — die bulk, bonding interface, or an intervening active tier. A tier two layers from the heat-removal face inherits the resistance of…

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the article section

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